https://jhmtr.semnan.ac.ir/ Journal of Heat and Mass Transfer Research en daily 1 Tue, 01 Dec 2026 00:00:00 +0330 Tue, 01 Dec 2026 00:00:00 +0330 https://jhmtr.semnan.ac.ir/article_10563.html Transcritical CO₂ refrigeration systems are increasingly adopted as low-GWP alternatives; however, their performance deteriorates due to high gas cooler pressures and large throttling losses. Subcooling the refrigerant before expansion is a key thermodynamic solution to mitigate these losses, yet a comprehensive and updated synthesis that directly compares the performance and applicability of diverse subcooling techniques within a unified framework is lacking. This review addresses that gap by providing a structured, critical analysis of both internal and external subcooling methods, including internal heat exchangers (IHX), ejector- and expander-assisted systems, and mechanical and thermoelectric subcoolers. The consolidated findings indicate that for high-ambient conditions, mechanical subcooling consistently emerges as the most effective approach, offering substantial COP improvements (20-40%) and in the case of DMS, significant discharge pressure reduction. This review further examines integration challenges, advanced control strategies, and emerging hybrid and renewable-assisted systems, offering valuable insights for researchers and designers aiming to enhance the sustainability and performance of next-generation CO₂ refrigeration technologies. https://jhmtr.semnan.ac.ir/article_10432.html In this study, a cycle for water production from air trapped in a closed chamber is simulated and analyzed. The cycle comprises two sections: humid air and refrigerant. Humid air flows over evaporator coils, condensing water vapor into droplets. Various parameters affecting the cycle's performance, including the temperature and flow rate of incoming humid air, and the refrigerant temperature, are investigated. Through numerical modeling and parametric analysis, it is found that lower refrigerant temperatures in the evaporator significantly increase water production, especially at temperatures below 5°C. Furthermore, increasing the humid air flow rate up to 0.05 kg/s enhances dehumidification, but further increases beyond this rate reduce dehumidification as the cooling capacity is primarily used to lower air temperature. Additionally, it is observed that higher inlet air temperatures initially increase water production, with optimal flow rates varying based on temperature conditions. The ratio of latent heat to compressor power consumption improves with higher flow rates up to 0.05 kg/s, after which efficiency decreases. While the Coefficient of Performance (COP) improves with increased air flow rates, higher evaporator coil temperatures lead to reduced moisture extraction. These findings provide valuable insights for optimizing water production cycles, offering strategies to enhance efficiency for industrial and environmental applications. https://jhmtr.semnan.ac.ir/article_10605.html This study evaluates magnetic nanoparticle hyperthermia for treating peritoneal metastasis, focusing on the effect of ascitic fluid and convection on tumor heating and healthy tissue. Magnetic nanoparticles (MNPs) were applied to raise tumor temperature to 42–46°C under an alternating magnetic field. Finite element simulations were used to calculate magnetic field distribution (Maxwell’s equations), heat generated by MNPs (Rosensweig model), temperature in the tumor and surrounding solid tissue (Pennes bioheat equation), and fluid temperature and convection in the peritoneal cavity (Navier–Stokes equations). Induction heating in the tumor was unaffected by ascitic fluid, though overall heat in the peritoneal cavity increased. Heat generated by MNPs was lowest at the tumor center and highest near the surface, with ascitic fluid enhancing heat production. Tumor temperature reached 45–46°C without ascitic fluid but decreased to 43–44°C when convection was present. Healthy tissue temperature remained below 44.2°C in both scenarios. Convective cooling in the fluid was the dominant factor influencing temperature distribution, causing non-uniform heating within the tumor. Conclusion: Magnetic nanoparticle hyperthermia effectively targets tumor tissue while protecting healthy tissue. The presence of ascitic fluid significantly alters temperature distribution through convection, highlighting the importance of considering fluid dynamics in treatment planning. https://jhmtr.semnan.ac.ir/article_9943.html In previous work, the reverse osmosis (RO) process was evaluated based on the potential synergy of Process Design and response surface methodology (RSM) methodologies, and the effects of membrane age, percentage recovery, concentrations of salts, pH, temperature, and pressure of feed water and the rejected brine concentration were optimized and modeled. The current work includes the determination of phenomenological parameters of mass transfer for RO membrane systems using the Spiegler-Kedem-Katchalsky model. The mass transfer coefficient and membrane permeability for salts were determined as a function of temperature and percentage recovery. The calculations of mass transfer parameters were based on a reference RO membrane (ESPA4-LD-4040), a three stage RO process, a 3-year membrane age with 95% and 85% recovery, a permeate flow 20 m3/h, pH 7, a constant feed TDS of 800 mg/l, constant pump pressure for feed water of 15 bar, and feed-water temperatures of 4, 8.2, 25, 30, and 42oC. The results showed that when the temperature increases from 4°C to 42°C, the mass transfer coefficient increases by 35.44% for 95% recovery, and 83.97% for 85% recovery, respectively. A general mathematical model describing the relationship between the mass transfer coefficient and feed water temperature, water permeability, and salt permeability was developed. The Spiegler-Kedem-Katchalsky model proved its capability for membrane performance evaluation through the determination and correlation of the phenomenological parameters of mass transfer for the membrane system. https://jhmtr.semnan.ac.ir/article_10009.html One of the challenging issues in the evaporation process is investigating the dynamic behavior of bubbles while considering the continuous changes in the bubble's contact angle with the surface. In this study, the effect of the dynamic contact angle on the accuracy of predicting the heat transfer coefficient and the dynamic behavior of the bubble during the evaporation process is examined. In this numerical study, the Volume of Fluid (VOF) method was used to track the two-phase interface, and the Lee phase change model was employed to simulate the liquid-to-vapor phase transition. The influence of the dynamic contact angle on the prediction accuracy of the heat transfer coefficient and the bubble's geometric parameters was analyzed. Furthermore, the effects of wettability, heat flux, bubble diameter, and bubble contact diameter on the heat transfer coefficient and the bubble departure time were investigated. A comparison of the heat transfer coefficient results with the Stephan and Preußer correlation revealed that the predicted heat transfer coefficient in the dynamic contact angle case is approximately 37% higher than in the constant contact angle case, with a 1.4% error compared to the Stephan and Preußer correlation. Moreover, in the dynamic contact angle case, the bubble's geometric parameters during evaporation were predicted with an error of less than 4% compared to experimental results. The results also indicated that surface wettability has a significant impact on the heat transfer coefficient. Finally, it was shown that increasing the heat flux, decreasing the bubble diameter, and reducing the bubble base diameter significantly enhance the heat transfer coefficient and decrease the bubble departure time. https://jhmtr.semnan.ac.ir/article_10010.html In this study, a 2-D CFD simulation was carried out using ANSYS Fluent to analyze the thermal and flow behavior of a single-pass rectangular solar air heater (SAH) duct fitted with semicircular roughness. Single, triple, and penta rib configurations were tested across Reynolds numbers (4,000 to 20,000) and rib pitches from 15 mm to 24 mm, corresponding to P/e ratios between 10.7 and 17.1. The objective was to evaluate how these geometrical variations influence heat transfer (Nusselt number), pressure loss, outlet temperature, and the overall thermo-hydraulic performance (THPP). The penta-15P configuration showed the highest heat transfer rate (Nu = 137.8) and pressure drop (54.14 Pa) at Re = 20,000, while also delivering the highest outlet temperature of 306.2 K at Re = 4,000. Despite the rise in flow resistance, the best balance between heat transfer and frictional loss was achieved by the penta-24P setup at Re = 4,000, which recorded the maximum thermo-hydraulic performance value of 2.59. These findings suggest that while more complex rib designs enhance thermal efficiency, they also increase flow resistance. Among all tested designs, the penta-24P configuration stands out as the most efficient option for improving solar air heater performance at lower flow rates. https://jhmtr.semnan.ac.ir/article_10073.html Internal leakage in industrial pressure valves is recognized as a critical hazard in the gas industry, where timely and accurate detection plays a vital role in preventing accidents and minimizing energy losses. Acoustic Emission (AE) technology, as a non-destructive and online method, has recently become one of the key tools for condition monitoring of industrial equipment, particularly in noisy environments. In this study, an intelligent leakage monitoring system based on AE was designed and developed to detect and assess the severity of internal leakage in valves used at the gas pressure reduction station in Qazvin Province. The focus of the research was on two commonly used types of industrial valves (ball valves and plug valves) whose structural differences pose analytical challenges in leakage detection. Initially, a laboratory-scale pilot system was built to simulate controlled leakage scenarios, and the resulting AE signals were used to develop and train signal processing algorithms. The proposed system was subsequently evaluated under real operational conditions with high levels of ambient noise. One of the key contributions of this research is the introduction of a quantitative index for determining internal leakage severity based on features extracted from the AE signals, enabling real-time classification and monitoring of valve performance. Field results confirmed that the developed system can accurately detect even minor leakages without requiring process interruption and assess their severity with high reliability. https://jhmtr.semnan.ac.ir/article_10102.html An experimental investigation was conducted to enhance gas turbine combustion chamber efficiency by eliminating hot spots, stabilizing operation, and achieving uniform temperature distribution. The effects of gas-to-liquid ratio (GLR) on spray characteristics of an industrial airblast injector were studied using the Particle Droplet Image Analysis (PDIA) technique. At GLR = 3.8, the minimum Sauter Mean Diameter (SMD) reached 235 µm at 4 cm from the injector tip centerline. Axial and radial distributions of SMD revealed that higher GLRs result in finer atomization, with a reduction of up to 22% in average droplet size compared to low GLR cases. The spray cone angle varied between 92° and 96°, influencing particle dispersion and chamber coverage. Injector rearrangement based on spray pattern, SMD, and cone angle achieved a 3% reduction in average turbine outlet temperature and significantly improved temperature uniformity, as confirmed by six thermocouple measurements. These results demonstrate that optimized injector configuration enhances combustion performance and thermal efficiency in gas turbines. https://jhmtr.semnan.ac.ir/article_10103.html Shell-and-tube heat exchangers (STHXs) are widely employed in industrial thermal systems, but conventional baffle designs often cause high pressure drops, stagnant flow regions, and suboptimal heat transfer. This study proposes and numerically evaluates a novel three-zonal porous baffle configuration, wherein porosity is varied radially to redistribute shell-side flow, suppress bypassing, and enhance turbulence. Using computational fluid dynamics (CFD) with the realizable k–ε turbulence model, the effects of baffle thickness (7.5–10 mm), zonal cut radius (21.00–22.00 mm), and baffle number (6–8) were systematically investigated. The optimized structure (a 10 mm thick baffle with 8 units at Zonal Cut Radius, Rc = 21.00 mm) obtained a maximum heat transfer coefficient of 13,008 W/m²·K and a heat flux rate of 423.21 kW, demonstrating a 28% improvement over conventional porous baffles. Simultaneously, the design reduced shell-side pressure drop by up to 49%, lowering pumping power requirements while maintaining high thermal efficiency. Parametric analysis revealed an optimal cut radius range (21.0–21.5 mm), beyond which heat transfer gains plateau due to flow saturation. The porosity gradient (inner ≈30%, middle ≈30%, outer ≈40%) proved crucial in minimizing stagnant zones and strengthening crossflow mixing near tube walls. These findings establish three-zonal porous baffles as a scalable and manufacturable enhancement for industrial STHXs, offering a practical route to improved energy efficiency, reduced operating costs, and extended equipment life. Future work should experimentally validate these results and explore advanced materials and alternative cut angles for broader industrial applicability. https://jhmtr.semnan.ac.ir/article_10113.html The effective dissipation of thermal energy remains a persistent and critical issue in modern engineering systems, particularly those characterized by miniaturization or geometric complexity. Motivated by limitations inherent in conventional cooling paradigms, this study explores the increase of convective heat transfer in porous microchannels, enhanced by applying magnetic fields. A detailed two-dimensional computational fluid dynamics (CFD) simulation was undertaken, Analyzing the flow behavior of a Fe₃O₄-water nanofluid in a microchannel featuring a porous structure. The study systematically evaluated the thermal and hydrodynamic performance under varying magnetic field intensities (spanning 800 to 1400 Gauss) and utilizing distinct magnet array configurations (two magnets versus four magnets). Findings reveal that the imposition of magnetic fields yields a statistically significant enhancement in heat transfer efficacy, particularly within intermediate flow regimes. At a Reynolds number approximating 600, the four-magnet configuration, subjected to a 1400 Gauss field, manifested a maximum Nusselt number increment of 58.4%, indicative of substantial improvement in thermal dissipation capabilities. However, as the flow transitions towards an inertia-dominated regime at elevated Reynolds numbers (≈1800), the effect of the magnetic field diminishes correspondingly, with the (PEC) asymptotically approaching unity. Furthermore, pressure drop penalties engendered by magnetohydrodynamic forces are observed to be most pronounced at lower flow rates, while a gradual decline as the Reynolds number is increased. These observations provide a valuable empirical and theoretical foundation for the design of high-performance microchannel thermal management systems predicated on the synergistic exploitation of magnetohydrodynamic principles and the thermophysical properties of ferrofluids. https://jhmtr.semnan.ac.ir/article_10156.html The hydrodynamic behaviors of refined sugar bed with a continuous gas stream and a horizontal pulsed gas in a gas-particles bubbling fluidized bed were simulated by the 2D Two Fluid Model. The effect of pulse frequency on the hydrodynamics of the gas and particles was also analyzed. The results show that the porosity of the bed and the size of the bubbles caused by the pulsed gas were greater than those of the continuous fluidization. The simulation results also determined that the average velocity of the gas flow through the distribution grid is greater than 0.94 m.s-1 and the pulse frequency changes between 0.5 Hz and 1.5 Hz, which is suitable for pulsed gas fluidization for refined sugar products. In this range, the superficial velocity reaches an average value of 0.67 m.s-1, fluctuating between 0.35 m.s-1 and 0.9 m.s-1, the bed porosity varies within this range 0.25 - 0.59, and the pressure drop across the bed ranges from 300 - 900 Pa. The gas-particles bubbling fluidized bed system with pulsed gas flow enhances the mixing of particles and gases while reducing gas flow compared to the conventional continuous fluidized bed system. https://jhmtr.semnan.ac.ir/article_10157.html Abstract: In this research, nanofluids inside a microchannel, under a laminar flow regime, were investigated using CFD tools and the finite volume method with Ansys Fluent software. A corrugated heat absorber microchannel is used with a flat plate. 3% of copper oxide solid nanoparticles suspended in a non-Newtonian Nanofluid. It was obtained from a concentration of 0.5% by carboxymethyl cellulose (CMC) in water fluid. As a result of this research, the pressure drop increases by about 70%. Also, the pressure drop increased, but no significant effect on the results was observed with the change in the height of the microchannel. The innovation is studying the laminar regime non-Newtonian nanofluid of water-carboxymethyl cellulose with a concentration of 0.5% by weight and copper oxide solid nanoparticles with a volume fraction of 1% and 3%, in a sinusoidal and three-dimensional microchannel with non-slip boundary conditions. The goal was to increase heat transfer and it is successful. https://jhmtr.semnan.ac.ir/article_10203.html Relative performance analysis in terms of flame shape, size, temperature distribution and pollutant levels of non-swirling turbulent, Inverse Diffusion Flame (IDF) and Central Diffusion Flame (CDF) is experimentally studied. Methane gas is used as fuel and air as an oxidizer. In IDF (two inlet system), air enters through the central tube and fuel through the outer coaxial tube. In CDF (three inlet system), another coaxial tube is added around the outer fuel tube and secondary air (annular) is supplied through it. In IDF and CDF, both mass flow rate of air (125 LPM) and mass flow rate of fuel (4 LPM) are kept constant in all cases. In CDF, secondary air flow rate is varied between 5 and 25 percent in 5 percent increments. Flame characteristics such as flame appearance, length, temperature distribution, and emission are measured and compared for IDF and CDF. Secondary air in CDF improves flame stability compared to IDF. Better stability is observed in CDF compared to IDF. Total flame length and blue zone length are less in CDF compared to IDF because the reaction zone shifts towards the flame base as the annular jet of CDF provides additional air for the combustion process. CO emission level decreases with increasing annular air fraction in CDFs. CDF with 10% annular air outperforms in terms of blue zone length, flame length, CO emissions and combustion noise. https://jhmtr.semnan.ac.ir/article_10204.html The convection heat transfer flow of air in a rectangular duct with and without diamond obstacles arranged in two ways (aligned and staggered) was experimentally examined in this work. The purpose of the diamond obstacles was to enhance heat transfer within the duct. A variety of turbulent conditions were utilized for the tests.(Re=10000–35000). Pitch to obstacle height ratios of 4, 5, and 6 were employed with aluminum barriers at height ratios of 0.16, 0.25, and 0.3. These barriers improved heat transfer by enhancing the mixing process between air and the heated walls, according to the experiments' findings. This is seen when the barriers apply with (e/H) = 0.3 and (p/e) = 6 for the two configurations. The staggered configuration is thought to provide the best enhancement of thermal performance equal to 174 % at Re=10,000 while aligned arrangement is 156% at the same conditions. Regarding the pressure drop, the findings demonstrate that the staggered arrangement yields the highest friction factor values for all investigated velocities, as well as the highest values for the elevation and pitch ratios, it reaches to 0.14 at Re=10,000 for staggered and 0.122 for aligned. https://jhmtr.semnan.ac.ir/article_10205.html The aim of the present study is to analyse the natural convection through numerical simulation in a trapezoidal shaped enclosure intact with a uniformly heated cylinder. The purpose of this study is to investigate the effect of various controlled parameter like trapezoidal angle (95°- 115°), cylinder position (CP1- CP5), Rayleigh number (1 × 105- 1 × 107) and for different boundary conditions of the enclosure walls on the rate of heat transportation. A control volume approach with SIMPLE algorithm is used to solve the governing conservation equations for laminar, steady, two-dimensional natural convection. It has been observed during analysis that the flow movement of the fluid has been affected substantially when the cylinder position changes to different locations which leads to the variation in the rate of heat transfer. Furthermore, the rise in heat transfer is observed when the enclosure angles and Rayleigh number are changed in ascending order. This study covers the impact of trapezoidal angle along with heated cylinder position on the heat transportation. https://jhmtr.semnan.ac.ir/article_10206.html This study evaluated the thermal performance of a 100 cc internal combustion engine cylinder through the integration of geometry–material–FEM criteria aimed at a techno-economic co-optimization. Four fin geometries (rectangular, circular, angular, and trapezoidal prismatic) and five alloys preselected using CES EduPack (Al 5182-H19, Mg Z6, lamellar graphite cast iron EN-GJL-300, Zn–Cu–Ti Korloy 3130, and Zn–Al ZA-27) were analyzed. The developed method comprised: (i) CAD modeling in SolidWorks, (ii) material preselection based on thermal conductivity (k), density (ρ), and cost, and (iii) steady-state thermal simulations in ANSYS, where minimum and maximum temperatures (Tmin/Tmax), heat flux, and fin mass were quantified. The results showed that the angular geometry maximizes heat dissipation, reaching a maximum heat flux of approximately 0.069 W/mm² (Al 5182-H19: 0.069172; Mg Z6: 0.069177), outperforming rectangular (≈ 0.056–0.063 W/mm²), trapezoidal (≈ 0.044–0.050 W/mm²), and circular (≈ 0.038–0.042 W/mm²) geometries. With the Mg Z6 alloy, fin mass remained low (0.360 kg for angular), offering advantages over aluminum (≈ 0.522 kg) and particularly over cast iron (≈ 1.424 kg). In relative terms, the angular + Mg Z6 combination increased maximum heat flux by approximately 85% compared with circular + Mg Z6 (0.069177 vs. 0.037448 W/mm²) and by 24% compared with rectangular + Mg Z6 (0.055613 W/mm²), maintaining Tmax ≈ 585 K and reducing Tmin to ≈ 552 K, thereby enhancing the thermal dissipation gradient at the fin base. In summary, the main contribution of this study is a reproducible methodology for form–material co-optimization based on the finite element method and a multicriteria selection (k–ρ–cost), enabling quantitative decision-making for small-displacement cylinder redesign. Consequently, the combination of angular fins with the Mg Z6 alloy is identified as the most favorable option for lightweight engines, balancing thermal performance, mass, and cost. https://jhmtr.semnan.ac.ir/article_10207.html In recent decades, researchers have focused on passive techniques that use vortex generators (VGs) to enhance the transport of heat. By trying to decrease the flow's pressure drop, this study aims to examine the strength of the vortex produced by VGs. The result shows that the winglet vortex generators' increased attack angles produce stronger secondary flows, which improve fluid mixing and heat transfer coefficient. Experiments were carried out in the Reynolds number range of 4096 to 20,480 in the current study to assess pressure drop and heat transfer enhancement. The study's findings show that, with comparatively modest errors, the measured coefficients of heat transport from the test data have a same inclination as per trend. Compared to CRWVGs, RWVGs exhibit a lower pressure drop, however with a marginal reduction in heat transfer enhancements. Heat transfer performance was only decreased (by about 2.1%), when holes were added to RWVGs. But because of increased flow resistance, these improvements came with a higher pressure drop, for which RWVGs reached 35.37% and for CRWVGs even higher at 60°. https://jhmtr.semnan.ac.ir/article_10223.html This study presents a pore-scale numerical investigation of water vapor adsorption in silica gel using the lattice Boltzmann method (LBM). Five distinct geometric configurations with nearly identical porosity values (~0.56) were simulated to ensure consistent flow conditions and enable a focused analysis of adsorption dynamics. The results demonstrated that fluid flow behavior remained uniform across geometries, with permeability values showing minimal variation. The adsorption process was then examined under varying particle sizes (1.6 to 4.57 μm), inlet concentrations (20 to 40 mol.m^(-3)), and Langmuir isotherm parameters. Among all the examined factors, particle size had the most pronounced influence on adsorption dynamics. Smaller particles (1.6 μm) achieved complete adsorption within 17 μs , while larger particles (4.57 μm) required up to 95 μs, about 5.5 times longer. This delay in larger particles is attributed to their higher internal diffusion resistance, whereas smaller particles, with their greater area-to-volume ratio, enabled faster adsorption and higher mass flux. Conversely, changes in inlet concentration and the absolute values of the Langmuir adsorption and desorption rate constants (adsorption rate k_a altered from 1.47×〖10〗^6 to 1.47×〖10〗^8 with constant adsorption to desorption rate K) had negligible effects on the overall dynamics. These findings highlight that solid-phase diffusion is the dominant mechanism governing adsorption in silica gel, while the influence of isotherm kinetics and external concentration gradients is of second importance. This work contributes to a deeper understanding of mass transfer limitations in porous adsorbents and offers insights for optimizing material design and operating strategies in adsorption-based systems. https://jhmtr.semnan.ac.ir/article_10277.html The combination of hyperthermia and intravesical chemotherapy is a promising strategy for non-muscle-invasive bladder cancer. However, during intravesical drug administration, the formation of air pockets within the bladder is common and may influence thermal distribution and overall treatment efficacy. Magnetic nanoparticle hyperthermia is a preclinical technique for localized, controllable thermal therapy in bladder cancer. This study numerically investigates the impact of intravesical air pockets on the efficacy of magnetic nanoparticle hyperthermia in stage T1 non-muscle-invasive bladder cancer. A two-dimensional finite element model incorporating the Pennes bioheat equation and Navier–Stokes equations simulated tissue heating and fluid dynamics. Air pockets of two different volumes were analyzed to investigate size-dependent thermal effects, and their positions were varied to examine the influence of direct contact with the tumor compared to no contact. The results showed that air pockets did not alter the magnetic field intensity in the tumor region. Air pockets not in contact with the tumor had no measurable impact on nanoparticle heating or tumor temperature. Air pockets in direct contact with the tumor increased intratumoral temperature, enhanced thermal uniformity, and reduced nanoparticle heating power. Larger tumor-contacting air pockets slightly increased intratumoral temperature without significantly affecting spatial distribution. These findings indicate that air pockets, regardless of size or position, do not compromise the therapeutic effectiveness of magnetic nanoparticle hyperthermia and may offer a procedural advantage over conventional hyperthermia in treating bladder cancer. https://jhmtr.semnan.ac.ir/article_10288.html Enhancing the thermal efficiency of solar systems, particularly vacuum tube collectors, is crucial in addressing challenges related to energy storage and fluctuations in solar radiation. The incorporation of phase change materials (PCMs) into these collectors provides an effective means of thermal energy storage. However, the inherently low thermal conductivity of PCMs limits heat transfer, thereby reducing their overall effectiveness. To overcome this constraint, optimizing the geometry of fins and absorber plates has been shown to markedly improve the uniform melting of PCMs. In this study, four innovative configurations of a vacuum tube solar collector incorporating fins, an absorber plate, and PCM were developed and analyzed. The investigation focused on the influence of fin and absorber plate geometries on the PCM melting behavior under identical boundary conditions, PCM type, and fin arrangements. The melting process was first evaluated over a 15-second interval, during which the fourth configuration achieved the highest melting rate, with a PCM liquid mass fraction of 0.286. This superior performance was further confirmed over an extended period of 80 seconds, where the same configuration consistently exhibited the most rapid melting. The novelty of this work lies in the synergistic integration of fins, absorber plates, and PCMs, combined with the strategic placement of fins, partial filling of the collector with PCM, and the introduction of a uniquely designed absorber plate. These design innovations collectively distinguish the present study from previous research and highlight the potential of advanced geometric optimization to enhance the performance of solar thermal energy storage systems. https://jhmtr.semnan.ac.ir/article_10289.html This study numerically investigates a series of novel lip-shaped divergent-exit hole configurations designed to enhance film cooling effectiveness on turbine blade surfaces. Six configurations were analyzed Full Lip (FL), Oval Lip (OL), Oval Upper Lip (OUL), Oval Lower Lip (OLL), Full Upper Lip (FUL), and Full Lower Lip (FLL) using Reynolds-Averaged Navier–Stokes (RANS) simulations with the RNG k–ε turbulence model. The computational results were validated against experimental data for a baseline cylindrical hole at multiple blowing ratios (M = 0.5, 1.0, and 1.5). The findings indicate that all lip-shaped geometries improved the laterally averaged film cooling effectiveness compared with the conventional cylindrical hole, with the FL configuration exhibiting the most consistent performance. At M = 1.5, the FL hole achieved up to 100% enhancement in film cooling effectiveness relative to the baseline, primarily due to improved coolant attachment and suppression of jet lift-off. These results demonstrate the potential of asymmetric lip-shaped exits to achieve more uniform cooling coverage and higher thermal protection under realistic turbine operating conditions. https://jhmtr.semnan.ac.ir/article_10291.html In many applications, such as power plants, thermal energy may be lost to the ambient environment so, using devices such as heat pipe heat exchangers is necessary to recover this energy. In this study, a thermosiphon heat pipe heat exchanger is designed and manufactured for this purpose. The thermal performance of this exchanger is experimentally and numerically investigated at different filling ratios (35%, 50%, and 75%) of a working fluid (DOWTHERM™ A) and condenser inlet air velocities (0.5, 1, 1.5, 2, and 2.5 m/s). The study is carried out at a wide range of evaporator inlet air temperatures (160 to 320°C), constant evaporator inlet air velocity (1 m/s), condenser inlet air temperature (24°C) and heat flux (8000 W). The exchanger model used in this study includes 60 copper heat pipes with square aluminium fins. The heat pipe (100 cm total length) consists of three sections namely: the evaporation section (40 cm length), the adiabatic section (20 cm length), and the condensing section (40 cm length). The results show that the filling ratio, air velocity, and evaporator air temperature have an important effect on the thermal performance of the heat exchanger. In overall, the optimum values of the filling ratio, air velocity, and evaporator air temperature to obtain the best thermal performance of the exchanger are 50%, 0.5 m/s, and 320°C, respectively. Where at these values, the highest condenser air temperature and maximum exchanger effectiveness (240°C and 74% numerically and 250°C and 77% experimentally) are obtained. Through the comparison between the numerical and experimental results, an excellent agreement is found between them with a maximum difference percentage that does not exceed 5%. https://jhmtr.semnan.ac.ir/article_10292.html This study investigates the thermal–hydraulic performance of a single H-type fin-and-tube heat exchanger, emphasizing the influence of weld quality and thermal contact resistance at the fin–tube interface. The research addresses a critical gap regarding how imperfect welds and interfacial resistance affect the efficiency of H-type fin–tube heat exchangers commonly used in waste heat recovery applications. The methodology combines physical modeling to conceptualize geometry and thermal–fluid interactions, mathematical formulation to define governing equations for conjugate heat transfer and turbulent flow, and numerical simulations using ANSYS FLUENT to evaluate steady-state performance. Results show that a thin resistive layer with a thermal contact resistance of 3.08 × 10⁻⁶ K•m²/W reduces the overall heat transfer coefficient, Nusselt number, and Colburn j-factor by approximately 8%, while the friction factor remains largely unaffected. Velocity and temperature profiles reveal localized flow acceleration and temperature gradients near imperfect welds, highlighting regions prone to thermal hotspots. Discontinuous welds with incomplete penetration (GL/Ft = 0, Gw = 0.01 mm) immediately reduce heat transfer efficiency by 13%, escalating to ~50% over long-term operation due to localized overheating, corrosion, and fatigue. The novelty of this work lies in its Multiphysics framework, which quantifies hidden effects of weld discontinuities and provides practical insights for heat exchanger design optimization, weld quality assurance, and long-term reliability of compact energy recovery systems. https://jhmtr.semnan.ac.ir/article_10293.html This study presents a prediction model for a vertical flat plate under conditions of high wall superheat and low water subcooling in mixed-convection film boiling, utilizing Linear, AdaBoost, Random Forest, and Gradient Boosting regression models integrated with machine learning approaches. The analysis of saturated and low subcooled film boiling has been conducted from heat and mass transmission perspectives and relevant vaporization criteria using heat ratio. Predictions for the Nusselt number have been formulated for several flow configurations, encompassing wall superheat ranging from 260 to 1200°C, liquid subcooling from 0 to 10°C, and flow velocities from 0 to 2.65 m/s. The Gradient-boosting regression model precisely predicted Nu across diverse flow conditions with an error margin of less than ±1%, indicating as an effective instrument for predicting the thermal performance of high wall superheat, low water subcooling mixed-convection film boiling, outperforming the predictive abilities of Linear, AdaBoost, and Random Forest regression models when compared with experimental data. https://jhmtr.semnan.ac.ir/article_10294.html Water deficiency is a significant global challenge that requires the advancement of sustainable and effective desalination methods. Solar stills provide a feasible solution for the production of fresh water in areas dealing with water limitations, particularly in remote locations. The intermittent and changing character of solar radiation imposes significant limitations on most applications. The accurate forecasting of solar radiation is crucial for estimating the distillate yield of a solar still system. For this purpose, the study evaluates the freshwater yield of the modified pyramid solar still in Tehran. Utilizing monthly data from 1984 to 2023 and employing Long Short-Term Memory (LSTM), Gated Recurrent Unit (GRU), Convolutional Neural Network (CNN), and CNN-LSTM algorithms, predictions for solar irradiance and temperature are calculated for the next ten years. The results validated the better performance of the CNN and GRU models in forecasting solar radiation and temperature. The predicted average annual freshwater yield for the ten years from 2024 to 2033 is calculated to be 2630 liters in Tehran. These findings emphasize the importance of integrating accurate solar forecasting techniques with renewable desalination systems to optimize water production. Furthermore, the approach outlined in this study can be applied to other regions with similar climatic conditions to enhance freshwater accessibility and ensure long-term water sustainability. https://jhmtr.semnan.ac.ir/article_10404.html The process of obtaining plant extracts includes several steps and the quality of an extract is influenced by several factors such as the parts of the aromatic and medicinal plant. The majority of research on plant drying focuses on the impact of the drying process on the chemical composition and antioxidant activity of essential oils and methanolic extracts on leaves, stems, flowers, and fruits. The different parts of the Myrtle (Myrtuscommunis L.) have traditionally various specific applications; fruit decoction is used in the treatment of infectious diseases and skin diseases In the present study, in collaboration with the laboratory for valorization of forest resources, we studied the behavior of myrtle fruits by combining two treatments highly recommended for the drying of aromatic and medicinal plants: a DIC pretreatment on initially fresh fruits followed by controlled convective drying of the temperature and humidity of the drying air, which represents an innovation in drying processes since we have treated the leaves with separate processes in previous research. The application of DIC resulted in an extended product structure, which led to a mathematical modeling of diffusion coefficient as a function of temperature and relative expansion ratio. As a result, the overall drying operation has improved in terms of efficiency, energy consumption and environmental sustainability. https://jhmtr.semnan.ac.ir/article_10405.html India possesses abundant coal reserves, but much of this coal is characterized by high ash content, presenting challenges for efficient utilization. To better understand and model the gasification behavior of high ash content coal, this study presents a novel application of Artificial Neural Networks (ANN) and Machine Learning (ML)-based regression models. Addressing a significant gap in existing literature, the models were developed to predict key output parameters—namely the concentrations of CH4, CO, CO2 and H2 using input features such as elemental composition (C, H, N, S, Ash). Three ML regression techniques—Multiple Linear Regression (MLR), Support Vector Regression (SVR), and Random Forest Regression (RFR)—were employed. Among these, the RFR model exhibited the highest prediction accuracy, with all outputs within permissible error limits and an R2 value of 0.99993. The SVR model also showed satisfactory performance but occasionally produced unrealistic outputs, such as negative CH4 concentrations. MLR, on the other hand, was inadequate for capturing the complex nonlinear relationships in the data. The ANN model achieved strong alignment with experimental results, with minimal average deviations across all target variables, and demonstrated stable performance after 10 training epochs. A comparative analysis between the RF and ANN models suggests that a hybrid modelling approach could further enhance prediction reliability. Overall, the findings confirm the suitability of advanced ML techniques, particularly Random Forest and ANN, for accurately modelling the gasification process of high ash content coal. https://jhmtr.semnan.ac.ir/article_10406.html This study employed the Reynolds stress turbulence model (RSM) to numerically investigate the influence of vortex finder shape on the hydrodynamic and collection efficiency within three cylinder-shaped oil-gas cyclone separators, a type commonly used in compressor systems. The simulations were based on realistic operating conditions. The computational simulations revealed that alterations to the outlet pipe configuration in cylindrical cyclones significantly affect the gas-phase hydrodynamics. Case 1 is characterized by the highest tangential velocity, which achieves 2.8 times the inlet velocity. However, Case 3 demonstrates the lowest maximum tangential velocity among the investigated configurations, approximately 1.1 times the inlet velocity. Furthermore, deformation of the cyclone, particularly through a reduction in the outlet diameter, enhances the pressure drop adjacent to the cyclone walls. Nevertheless, the resulting complex flow patterns give rise to a counter-rotating flow, which compromises the overall separation performance. Conversely, the region surrounding the outlet pipe is characterized by heightened turbulence kinetic energy (TKE) and more intense rotational vortices compared to other sections of the cyclone. Therefore, the separation efficiency of gas-oil cylindrical cyclones is positively correlated with increasing flow velocity. https://jhmtr.semnan.ac.ir/article_10407.html The present study employs a two-dimensional numerical analysis of heat transfer enhancement in a heat sink-inspired cavity using nanofluids, based on the Multiple Relaxation Time Lattice Boltzmann Method. A systematic analysis is conducted to investigate the impact of nanoparticle volume fraction (φ = 0-5%), Reynolds number (Re = 10-500), and Richardson number (Ri = 0.1,1,10) on thermal performance. The findings of the study demonstrate that augmenting the nanoparticle volume fraction substantially enhances heat transfer, particularly at low Reynolds numbers (Re ≤ 100), where natural convection exerts a predominant influence. In the case of a 5% concentration, the average Nusselt number is observed to increase by more than twofold in comparison with the base fluid. This phenomenon can be attributed to the enhanced thermal conductivity resulting from the presence of the substance under investigation. However, this enhancement diminishes as forced convection becomes dominant at higher Re. The greatest thermal performance gains occur at Ri = 0.1, indicating strong forced convection. A thorough investigation into the thermal performance factor reveals that nanofluids demonstrate optimal efficacy in low-flow regimes. https://jhmtr.semnan.ac.ir/article_10408.html Effective thermal management has become an essential part of the machining process, as the excessive temperature generated detrimentally affects tool life, dimensional accuracy, and the metallurgical properties of both the tool and the workpiece. With the advancement to Industry 4.0, the design of multifunctional materials has become one of the key focuses of advanced engineering. This study numerically presents an essential first step of designing a multifunctional cutting insert to obtain effective heat dissipation from the cutting tool tip by incorporating copper as a conductive material within cutting inserts, along with the thermal impact of the conductive material’s geometry, placement, and size. Findings demonstrated that the overall integration of conductive material significantly reduces the tool tip as well as the overall body temperatures. Among all the tested geometries of conductive material—circular, rectangular, square, and trapezoidal—the trapezoidal shape exhibited the most effective performance in lowering cutting temperature. The placement of conductive material near the tool tip and rake face proved to be highly efficient, while positioning beyond the heat-affected zone had negligible influence. Additionally, the effect of coolant velocity was found to be marginal after the introduction of conductive material, with a temperature reduction of less than 40 K between 1 m/s and 10 m/s. The most notable result was achieved with trapezoidal copper inserts, where a temperature drop of 478.89 K was observed under optimized conditions. Overall, this study establishes conductive material incorporation as a promising strategy for enhancing heat dissipation and minimizing thermal issues in metal cutting. While the findings of the foundational thermal analysis of the multifunctional W-Cu insert made it persuasive, it concurrently drew the mechanical challenges of structural integrity. https://jhmtr.semnan.ac.ir/article_10409.html A Taguchi-based Analysis of Variance (ANOVA) was conducted on a Triple pipe heat exchanger configured as a latent heat thermal energy storing system with stearic acid as a phase change medium (PCM). In this setup, stearic acid occupies the middle annular region, while water, acting as the working fluid (HTF), goes through the inner and outer annular tubes. Key design variables—fin geometry (G1–G4), mass flow rate (ranging from 0.11 to 0.45 kg/s), and working pressure (0.6–0.9 kg/cm²)—were investigated to optimize thermal effectiveness and energy storage capacity. The Taguchi method was employed to perform the optimization, and experimental runs were designed based on the L16 orthogonal array. Statistical analysis was carried out using Minitab software to assess the influence of all factors. Main effect graphs for both effectiveness and energy storage were generated to identify the optimal configuration. The study found that the combination of geometry G4, mass flow rate 0.11 kg/s, and pressure of 0.9 kg/cm² yielded the best performance in terms of effectiveness, whereas the configuration with geometry G1, mass flow rate of 0.11 kg/s, and pressure of 0.6 kg/cm² was optimal for energy storage. A confirmation experiment was conducted to validate the Taguchi optimization results, which showed excellent agreement with experimental data, exhibiting less than 2% error. Furthermore, ANOVA results indicated that fin geometry had the most significant impact on system performance, contributing 97.06% to effectiveness and 45.04% to energy storage, substantially more than the other parameters studied. https://jhmtr.semnan.ac.ir/article_10433.html The research topic aims to address the urgent need for enhanced energy efficiency in HVAC systems by developing and optimizing efficient heat transfer fluids. Despite the significant attention given to single-component nanofluids, there is a lack of systematic study on the performance of Al2O3-CuO hybrid nanofluids in a double-pipe heat exchanger for HVAC system applications. A comprehensive experimental investigation was done on the various hybrid nanofluid concentrations (0.05%, 0.1%, 0.15%) under different Al₂O₃:CuO ratios (70:30, 60:40, 50:50) at Reynolds number 3,000-12,000. Results show that 60: 40 Al2O3:CuO hybrid nanofluid of 0.1% concentration exhibits a 42.3% enhancement in Nusselt number, 38.7% increase in heat transfer coefficient and 28.4% improvement in thermal effectiveness over that of pure water, with tolerable friction penalties (15-22%). The obtained performance shows a remarkable increase when compared with other published works. The current correlation has 42.3% higher increase with 13.8% reported by Suresh et al. for Al2O3-Cu and 31% with Madhesh et al. for Cu-TiO2 hybrid nanofluids. The hybrid shows a 35.5% improvement over the single Al2O3 nanofluids and 13.5% improvement over CuO. A significant increase is shown in this work of 18-25 % as compared to single nanoparticles by using a hybrid system. It can be concluded that in the current research work, the experimental correlations were developed and validated which could be used to implement the hybrid nanofluids in the advanced energy-efficient HVAC systems. Finally, the study has developed validated experimental correlations which enable the implementation of hybrid nanofluids in advanced HVAC systems to achieve higher energy efficiency. https://jhmtr.semnan.ac.ir/article_10443.html The growing global demand for sustainable and high-efficiency energy sources has intensified research on alternative fuels for spark-ignition engines. This study experimentally investigates the performance and emission characteristics of the EF7 engine fueled with gasoline blends containing ethanol, methanol, and toluene at 5%, 10%, and 15% volumetric concentrations. An artificial neural network (ANN) model was concurrently developed to predict critical exhaust emissions including CO, CO₂, NOx, and HC based on engine operating parameters. Experiments were conducted at full load under constant speeds of 2000 and 3000 rpm, and the ANN model was trained and validated using the collected datasets. Results indicate that ethanol and methanol blends enhance brake power and torque up to a 10% blending ratio, primarily due to increased laminar flame speed, charge-cooling effects, and oxygen-enriched combustion chemistry. However, further increasing the alcohol fraction to 15% reduced engine output, attributed to the lower heating value and diminished volumetric energy density of the blends. Toluene addition provided stable power and torque across all blending ratios owing to its high octane number and knock resistance, though without notable performance gains. Emission analysis revealed that alcohol blends significantly decreased CO and HC emissions while slightly elevating CO₂ levels, confirming improved combustion efficiency. In contrast, toluene blends increased NOx and HC emissions, likely resulting from higher local combustion temperatures and incomplete aromatic oxidation. Overall, moderate alcohol blending (approximately 10%) achieved the optimal trade-off between engine performance and emission reduction. The integrated experimental–computational framework established in this study offers a robust methodology for optimizing blended fuels in spark-ignition engines. https://jhmtr.semnan.ac.ir/article_10444.html This study revisits the turbulent forced‑convection performance of multi‑walled carbon nanotube (MWCNT)/water nanofluids. Building on a Eulerian–Eulerian two‑fluid framework, we couple a second‑order orientation tensor with population balance equations (PBEs) to simultaneously resolve shear‑induced alignment, anisotropic thermal conductivity and aggregation kinetics. A rigorous grid convergence study and quantitative comparisons with published experiments demonstrate root‑mean‑square errors below 5 % in Nusselt numbers and friction factors. Micro-level validation of the constitutive models is provided by comparing predicted orientation factors with rheo-optical measurements and simulated cluster size distributions with dynamic light scattering (DLS) data. The new coupled model predicts an optimal operating window (0.8–1.2 vol% % MWCNTs, Reynolds number 20 000–40 000) where the performance evaluation criterion (PEC) exceeds 1.3. Within this window, axial thermal conductivity increases by ~38 % and Nusselt numbers by ~24 % at 1 vol% %, while hydraulic penalties remain manageable. Concentrations above 1.2 vol% % trigger rapid aggregation that reduces thermal conductivity and increases viscosity, producing PEC values below unity. An economic analysis based on a 500-kW cooling system and realistic nanofluid preparation costs indicates payback periods of less than two years when operated in the high-PEC region. The paper closes with a balanced discussion of modelling limitations and future research directions. https://jhmtr.semnan.ac.ir/article_10445.html This study numerically compares three thermo-dependent viscosity models—the Reynolds, Vogel-Tammann-Fulcher (VTF), and Williams-Landel-Ferry (WLF) models—in natural double-diffusive convection within a square cavity filled with a non-Newtonian binary fluid. The influence of the thermo-dependence parameter m and the behavior index n is assessed under fixed thermal and concentration conditions on vertical walls and adiabatic, impermeable horizontal walls. The dimensionless conservation equations for momentum, heat, and mass are solved using the finite volume method with a power-law scheme. Variations in m and n are examined for each viscosity model to quantify their effects on flow structures, Nusselt, and Sherwood numbers. The results demonstrate the importance of accounting for both thermo-dependent viscosity and rheological effects, providing validated guidance on model selection for accurate prediction of coupled heat and mass transfer in thermally sensitive, non-Newtonian systems. An increase in m intensifies flow circulation and enhances heat and mass transfer, while decreasing n (more pseudoplastic behavior) further improves transport performance. The VTF and WLF models produce results in close agreement with the Reynolds model, with only minor deviations for specific parameter combinations. Quantitatively, increasing m from 1 to 3 strengthens convective circulation by 45%, and enhances heat and mass transfer by 50% and 60%, respectively. Likewise, decreasing the behavior index to n = 0.6 produces 65% growth in flow strength, 40% in heat transfer, and 50% in solutal transport, highlighting the strong coupling between rheology and buoyancy dynamics. https://jhmtr.semnan.ac.ir/article_10463.html This research presents a parametric and sensitivity analysis to evaluate the effects of building orientation, mutual shading, and HVAC system performance on the energy consumption of residential buildings in four Iranian climates: Ahvaz (very hot/humid), Tabriz (cold/dry), Tehran (temperate/semi-arid), and Yazd (hot/dry). Utilizing a validated dynamic energy model in DesignBuilder, seven block configurations six within an alley and one standalone were simulated. The results quantify a critical climate-driven energy trade-off: strategic shading reduces cooling demand by 11.5% to 29% in hot and temperate climates but concurrently increases heating demand by up to 25% in colder settings. A key supplementary finding from sensitivity analysis is that enhancing HVAC system efficiency (e.g., increasing cooling COP from 2.5 to 4.5) can yield energy savings (~44.5%) comparable to those achieved by architectural shading alone. This underscores the necessity for an integrated design approach that synergizes climate-responsive urban form (optimized shading) with high-performance building systems to achieve optimal energy performance. The study provides evidence-based guidelines for the energy-conscious planning of residential complexes in similar climatic contexts. https://jhmtr.semnan.ac.ir/article_10498.html The scarcity of fresh water remains a pressing global challenge, particularly in arid and remote regions where conventional perfection methods are often expensive and energy-intensive. Solar distillation, using solar stills represents a sustainable and low-cost approach for producing potable water. This review provides a systematic evaluation of recent strategies aimed at enhancing solar stilts with particular emphasis on deign modifications, materials innovations and operational improvements. Key parameters influencing freshwater yield include basin water depth, climate conditions, glass cover orientation, and absorber surface characteristics. Recent advances highlight the effective use of phase change material for thermal energy storage, the incorporation of nano materials to improve solar absorption, and their application in reflective or cooling mechanisms to enhance evaporation and condensation processes. In addition, thermoelectric systems and hybrid configurations integrating photovoltaic modulus or solar concentrators have demonstrated substitutional improvements in efficiency and water output. Experimental and numerical investigations Despite these advancements, challenges related to economic feasibility, long-term durability, and adaptability to varying climatic conditions remain. This review concludes that further research is required to integrate advanced thermal management techniques with novel materials in order to develop scalable, efficient, and cost-effective solar desalination technologies capable of supporting sustainable freshwater supply. These findings provide a structured foundation for future scalable and economically feasible solar desalination systems suitable for real-world implementation. https://jhmtr.semnan.ac.ir/article_10555.html This study explores how Navier slip boundary conditions, applied either fully or in localized hydrophobic regions, reshape the vortex–induced vibration and heat–transfer behaviour of an elastically mounted square cylinder at a Reynolds number of 22,000 and Prandtl number of the flow is 7. The coupled fluid–structure dynamics are resolved using a finite-volume solver with SST k–ω turbulence modelling and a Runge–Kutta integrator for structural motion. The fluid–structure interaction framework is validated against reference results for both stationary cylinders under slip and no-slip conditions and conventional flow-induced vibration (FIV) responses, showing excellent agreement. Simulations are performed over the reduced-velocity range of 3–14 and various slip lengths (0\le b*\le0.2). For fully hydrophobic surfaces, the cross-flow vibration amplitude is substantially reduced—by nearly 50% at Ur=10—while the inline oscillation amplitude grows markedly, reaching almost a twofold increase at Ur=12. These changes coincide with an elevation in shedding frequency and a notable weakening of lift fluctuations. Heat transfer is consistently strengthened under slip, and the mean Nusselt number reaches a maximum enhancement of approximately 53% at higher reduced velocities. When slip is introduced only on selected surfaces, its effect becomes strongly configuration-dependent. Rear-face hydrophobicity produces the greatest suppression of transverse motion, front-face slip yields the most pronounced reduction in force coefficients, and only full-surface slip results in a significant rise in heat-transfer performance. Despite local irregularities with reduced velocity, the overarching trends remain clear, with slip accelerating vortex shedding, moderating cross-flow vibrations, increasing streamwise oscillations, and enhancing convective transport. These findings demonstrate that the strategic distribution of hydrophobic regions can serve as an effective passive-control approach for improving both the dynamic and thermal behavior of square cylinders in turbulent flow. https://jhmtr.semnan.ac.ir/article_10562.html This numerical analysis examines how radial temperature gradient influences the stabilization threshold of Taylor-Couette flow across a range of radius ratios (0.77 ≤ η ≤ 0.95). Numerical simulations were conducted for seven radius ratios, with a constant temperature gradient applied between the inner and outer cylinders. The primary objective was to determine the temperature gradient required to stabilize the flow at the threshold of transition from laminar to vortex flow. Velocity contours, vorticity, skin friction coefficient, velocity profiles, and streamlines were analyzed to assess flow stability. The results reveal that the minimum stabilizing temperature gradient occurs at a radius ratio of 0.877, beyond which the required temperature gradient increases significantly. For a radius ratio of 0.77, the Richardson number exceeds 10, leading to flow destabilization due to buoyancy forces. A predictive relationship for the stabilizing temperature gradient as a function of the radius ratio was derived. Additionally, the Nusselt number at the stabilizing temperature gradient was examined, and empirical correlations were provided. The findings highlight the critical role of temperature gradients in controlling flow stability and vortex suppression in Taylor-Couette systems, offering valuable insights for engineering applications. https://jhmtr.semnan.ac.ir/article_10564.html In recent years, the aerospace industry, including propulsion engines, and the power generation sectors, such as power plants and generation systems, have increasingly relied on gas turbines. The performance of a gas turbine connects closely with the temperature of the incoming gas. Thus, higher temperatures result in more effective operations. Moreover, this relationship showcases the importance of managing and optimizing gas inlet conditions. So, keeping temperatures elevated can truly enhance overall turbine performance. However, higher temperatures also lead to increased thermal stress and reduced material strength. Therefore, it is essential to employ effective cooling methods to protect hot components, such as turbine blades, from incoming thermal loads. This paper introduces various methods for cooling gas turbine blades, discussing the advantages and disadvantages of each method. It reviews research on the effectiveness of these cooling methods and explores how to achieve greater efficiency with each one. The outcomes from computational experiments are compared with existing experimental evidence. This helps to confirm the discoveries. Moreover, the appropriateness of the low Reynolds k-ε turbulence model (LS) for forecasting film cooling efficiency on a spinning blade is investigated thoroughly! Furthermore, the impact of shaped holes on film cooling characteristics at different rotating speeds (0, 300, 500 rpm) is considered. The study investigates how different hole shapes influence the cooling performance under varying rotational conditions. Finally, the use of laterally diffused holes at high rotating speeds is recommended to achieve the highest film cooling effectiveness. This recommendation is based on the observed improvements in cooling performance with laterally diffused holes, which provide better coolant distribution and enhanced cooling efficiency. By tackling these factors The document strives to enhance the current endeavors to boost gas turbine blade cooling methods. This ensures improved functionality & extended durability of turbine parts, especially in extreme heat situations. https://jhmtr.semnan.ac.ir/article_10571.html Energy exchange through shock waves has numerous practical applications, including gas compression, supercharging, power generation, and refrigeration. This paper focuses on utilizing shock waves and expansion waves for refrigeration. When high-pressure gas suddenly enters a receiving tube, it generates a shock wave that moves forward, while an expansion wave propagates in the opposite direction, creating a cooling effect. Compared to conventional turbo-expanders, gas wave refrigerators (GWR) require significantly lower rotational speeds, which makes them more cost-effective, structurally simpler, and operationally more reliable. Extensive research efforts worldwide aim to advance gas wave refrigeration technology. This review explores the contributions of various researchers on the design and development of different types of GWR. The paper highlights the technological challenges, such as the self-circulation ability of GWR to eliminate the need for an external circulation system, the capability to handle liquid in the gas, damping of the reflected shock wave and losses due to temperature differential along the length of the channels or tubes. These technological challenges addressed by different researchers are presented to enable the successful development and widespread adoption of gas wave refrigeration systems. Additionally, the latest cutting-edge trends in the field of GWR are also covered. This paper provides a comprehensive overview of the advancements made in GWR technology, along with its technical obstacles and potential solutions. https://jhmtr.semnan.ac.ir/article_10642.html This article presents the impact of combining evaporative cooling pads with an air-cooled chiller system installed in a commercial building, the Gullan Mall, to improve energy efficiency and performance. The plant, which covers an area of 40,000 m² and employs 420 staff, has six 1,400 kW chillers (model 30XB XB1400), each with a base Coefficient of Performance (COP) of 2.5. Evaporative pad was placed upstream of chiller condensers with 150 mm thickness, 81% saturation efficiency, and a low-pressure drop. Experimental results show high performance of the chiller between 11:00 am and 6:00 pm in peak summer (June). When ambient temperatures ranged from (38 to 44)°C, the COP of the system with the evaporative pad maintained higher values (3.5 to 4.0), while the COP without the pad decreased from 3.4 to 3.0 under the same conditions. This enhancement is due to reduced inlet air dry bulb temperature, leading to lower condenser pressure and compressor-specific energy while sustaining cooling capacity. Economic payback over 15 years at an electricity cost of $0.11/kWh and an initial investment of $43,200 demonstrated significant energy savings. A cost-effective adiabatic cooling strategy with evaporative pads resulted in saving 267.3 MWh, or 22% of electricity consumed, and its cost ($79,737.97 to $62,504.2) in June. Financial feasibility is supported by the Net Present Value (NPV) analysis, which signals a positive NPV. These results demonstrate the potential of integrating evaporative cooling for air-cooled chillers, especially in hot regions, offering a sustainable method for optimal HVAC performance and reduced energy use. Cooling pads slightly reduce CO2 emissions at higher power usage and reduce noise by 10-15 dB, improving efficiency and acoustic comfort. https://jhmtr.semnan.ac.ir/article_10659.html The optimization of engine cooling systems is critical for enhancing performance, reducing fuel consumption, and extending the lifespan of engines. This study explores the thermal performance of three modified fin geometries namely rectangular, circular, and angular, through the introduction of tapered geometries aimed at improving heat dissipation and reducing material usage. Using ANSYS Workbench 2020 R1, finite element analysis (FEA) was conducted to evaluate the thermal efficiency of these tapered fins under steady-state conditions. The results reveal significant improvements across all tapered fin designs. The Tapered Rectangular Fin achieved 4.18 times improvement in heat dissipation at the base along with a 36.07% reduction in weight compared to the baseline design. The Tapered Circular Fin provided 4.43 times enhancement in heat dissipation and a 16.36% decrease in weight. Notably, the Tapered Angular Fin outperformed the other configurations, delivering the highest improvement in both, the heat dissipation and weight reduction. The maximum heat flux of 0.22534 W/mm² for the modified angular fin represents a 5.54% improvement over the modified rectangular and 16.78% over the modified circular designs. These results confirm the efficacy of geometric tapering in optimizing fin performance for air cooled motorcycle engines. These modifications were achieved by tapering the thickness of the fins from 3 mm at the base to 1 mm at the tip, optimizing material usage while enhancing thermal performance. This study demonstrates the effectiveness of tapered fin geometries in enhancing thermal efficiency, reducing weight, and improving material efficiency in cooling systems. The results indicate that tapered fins provide a viable solution for the development of more fuel-efficient, sustainable, and cost-effective cooling solutions in the automotive industry. Furthermore, the findings have broader implications for other industries, such as aerospace and electronics, where efficient heat dissipation is essential. https://jhmtr.semnan.ac.ir/article_10671.html This article scrutinized the numerical investigation and optimization heat transfer analysis for a double diffusive mixed convection of cold water in a porous enclosure containing two sided moving lids with the inclusion of Dufour and Soret effects. The vertical boundaries of the enclosure are preserving with different uniform temperatures and concentrations, while the horizontal walls are treated as adiabatic. The lid-driven walls are constructed in four different cases based on the moving direction of vertical walls. In recognition of the link between pressure and velocity, the SIMPLE algorithm is utilized to solve the governed flow equations. The influence of Darcy number ranging from 10-4 to 10-1 and porosity ranging from 0.2 to 0.8 is measured with the representation of streamlines, isotherms and isoconcentration contours, and average Nusselt number. It is found that, the case 2 where the left and right vertical walls are moving towards downward and upward directions yields the optimum heat and mass transfer rates than the remaining cases. In particular, the increasing percentage of heat and mass transfer rate is about 177% & 200% for case 2 when the increase of Da from 10-4 to 10-3. It is intended that the research conducted can be used in the design of electronic cooling systems in the future. https://jhmtr.semnan.ac.ir/article_10691.html The statistical investigation and optimization of the characteristics of reactive distillation column for isoamyl acetate production to reduce energy consumption have been investigated using response surface methodology. Isoamyl acetate has three main applications including flavoring in the food industry, industrial solvent, and personal products. To optimize the characteristics of the reactive distillation, the variables under investigation included “Number of Reaction Stages” (2-4-6), “Number of Stripping Stages” (8-10-12), and “Number of Rectification Stages” (2-3). The response or dependent variables included “Reboiler Heat Duty” and “Condenser Heat Duty”. The response surface methodology and the CCD design method are used to model and determine the optimal levels of each parameter. The R2 value for “Reboiler Heat Duty” and “Condenser Heat Duty” are obtained at 0.9891 and 0.9890, respectively, indicating a high agreement of the model results with the input data. The optimal conditions included “Number of Reaction Stages”: 5, “Number of Stripping Stages”: 12, and “Number of Rectification Stages”: 2, in which “Reboiler Heat Duty” was 1737.107 W and “Condenser Heat Duty” was -1780.115 W. The simulation data matched the predicted responses of the statistical software, indicating that the statistical modeling is performed accurately. https://jhmtr.semnan.ac.ir/article_10713.html Channels with partial porous inserts provide improved thermal performance while effectively limiting pressure drop compared to fully porous configurations. The present study investigates steady, fully developed thermo-fluid transport of a Williamson couple stress fluid in a vertical parallel-plate channel partially filled with a Darcy–Forchheimer porous medium. The flow domain is divided into clear-fluid and porous regions, driven by a uniform pressure gradient. The channel walls are maintained at different constant temperatures, and interfacial conditions enforcing continuity of velocity, shear stress, temperature, and heat flux are imposed to ensure proper coupling between both regions. The governing nonlinear momentum and energy equations are non-dimensionalized and solved using the Differential Transform Method (DTM). The resulting semi-analytical solutions exhibit rapid convergence and are validated against numerical results. The obtained velocity and temperature fields are further used to evaluate entropy generation, skin friction, and Nusselt number, with detailed parametric effects reported through tables and plots. The study provides a unified mathematical framework for non-Newtonian thermofluid transport in composite porous channels and highlights the efficiency of DTM for solving strongly coupled nonlinear boundary-value problems of engineering relevance. The study is motivated by emerging applications in microfluidic transport, bioengineering systems, porous thermal management devices, polymer processing, and enhanced filtration technologies, where the simultaneous influence of microstructural effects, fluid elasticity, and inertial porous resistance becomes significant. https://jhmtr.semnan.ac.ir/article_10714.html A furnace is used in domestic heating and in industrial operations such as forging, annealing, and melting. A composite based furnace equipped with insulation and a hybrid heat source enhances thermal regulation and energy efficiency. This study models the governing heat transfer equations across composite furnace walls and applies MATLAB to transform and solve them. All surface heat equations were formulated using fundamental heat transfer principles. The nonlinear equations within the composite layers were numerically implemented in MATLAB using an explicit scheme and corresponding thermal conductivities to simulate temperature distributions. Results showed that the dimensionless heat flux, q ˉ, increased nonlinearly with furnace temperature, θ_i. The heat flux rose rapidly from approximately 0 to 0.35 as θ_i increased from 1 to 3, representing nearly 70 % of the attainable heat flux within the lower operating range. However, beyond θ_i≈5, only marginal increases in heat flux were observed, indicating increasing insulation effectiveness and thermal resistance. The convection surface temperature, θ_s, and insulation interface temperature, θ_in, both increased nonlinearly before gradually approaching stable values at higher furnace temperatures. Specifically, θ_s increased by about 25 %, while θ_in increased by approximately 67 %. Results further revealed strong thermal attenuation across the composite wall. For θ_i=3, the temperature reduced by about 52 % across the wall thickness, while for θ_i=6, approximately 75 % temperature reduction was achieved, demonstrating the effectiveness of the insulation layer in limiting heat penetration and reducing thermal losses. The authors recommend that future studies focus on increasing the composite wall to enhance temperature distribution across the furnace layers. Insulation in a composite-based furnace should be encouraged. https://jhmtr.semnan.ac.ir/article_10756.html This study focused on creating a form-stable phase change material (PCM) by impregnating coconut oil into the porous structure of expanded perlite with a defined particle size, utilizing a free adsorption method. Unlike many reported fatty acid–based form-stable PCMs, this study demonstrates that expanded perlite with an optimized particle size (0.1–1 mm) can stably retain up to 28 wt.% coconut oil using a simple free adsorption method, without vacuum assistance. To confirm its thermal reliability and chemical stability, the selected coconut oil/expanded perlite PCM underwent 100 melt/freeze cycles. The prepared PCM's characteristics and thermal energy storage capabilities were assessed using Scanning Electron Microscopy, Fourier Transform Infrared spectroscopy, and Differential Scanning Calorimetry. Key findings from the DSC analysis revealed a melting temperature of 12.76°C and a latent heat of 24.62 J/g for the coconut oil/expanded perlite form-stable PCM. These results indicate that the proposed CtO/EP form-stable PCM offers a cost-effective, thermally reliable, and scalable solution for low-temperature thermal energy storage, with strong potential for practical applications in greenhouse climate regulation and cold-chain energy management. https://jhmtr.semnan.ac.ir/article_10866.html This study investigated the effect of placing a rectangular obstacle in the divergent section of a venturi on hydrodynamic cavitation intensity. The geometry was simulated and analyzed over a range of pressure ratios from 3 to 6 and divergence angles from 5 to 7 degrees. The research aimed to develop a surrogate modeling framework based on Computational Fluid Dynamics (CFD) data for accurate cavitation intensity prediction. The results of CFD simulations show that in both venturi with and without obstacle, the average vapor volume fraction with increase of divergent angle decreases and with increase of pressure ratio increases. The presence of obstacle while maintaining these trends, the cavitation intensity significantly intensifies. Following data preprocessing, two machine learning models CatBoost and Gaussian Process Regression (GP) were trained and evaluated. Quantitative results demonstrated that both models performed with high accuracy, with CatBoost showing slightly superior performance (test R²: 0.903, RMSE: 0.00896) compared to GP (test R²: 0.886, RMSE: 0.00967). Comprehensive error analyses confirmed the models' robustness and generalizability. SHAP sensitivity analysis identified the divergence angle as the most influential parameter. https://jhmtr.semnan.ac.ir/article_10867.html Measuring turbine blade temperature is critically important due to the material's thermal limits. In this study, machine learning (ML) method has been used to predict the heat flux of the outer surface of a turbine blade model. The heat flux is predicted from the outlet temperature and the inlet velocity and inlet temperature and blade model length, which is in inverse heat transfer problems (IHTP). The Reynolds-Averaged Navier-Stokes (RANS) equations were solved to analyze heat transfer, and the k–ω model was used to account for turbulence effects. Simulations were carried out in 648 different cases with varying inlet velocities (6 to 20 m/s), inlet temperatures (300 to 310 K), blade heat fluxes (400 to 2000 W/m²) and blade model lengths (180 to 220 mm). The channel surface temperature, measured 100 mm downstream of the blade model, was recorded as the output. The results of the numerical analysis showed that the surface temperature is directly proportional to the heat flux of the blade model and is inversely proportional to the flow rate. The simulation results were processed as an inverse problem using support vector regression (SVR), optimized support vector regression, Gussian Process Regression (GPR), and multi-layer Perceptron (MLP) algorithms. The Marine Predators Algorithm (MPA) was utilized to optimize the hyperparameters of the SVR model, resulting to a significant improvement in the results. The mean absolute error for support vector regression, optimized support vector regression, multi-layer Perceptron, and Gaussian process regression algorithms were 0.0564, 0.0094, 0.0037, and 0.0069, respectively. These results indicate that the multi-layer Perceptron algorithm provided the best prediction performance for this problem. Finally, the MLP method was also processed with 792 and 432 data sets, which shows that the results are independent of the number of data sets. https://jhmtr.semnan.ac.ir/article_10868.html A solar parabolic trough collector is a solar thermal device that concentrates solar radiation onto a receiver tube to generate high temperature thermal energy. This study presents a numerical investigation to evaluate the thermal performance of a solar parabolic trough collector using inclined internal fin insertions. The standard LS-2 collector geometry is employed, with stainless steel as the absorber tube material and Syltherm-800 as the heat transfer fluid. Circular, rectangular, and conical fins are inserted at inclination angles of 45°, 60°, 75°, and 90° , and their thermo-fluid performance is evaluated under non-uniform heat flux conditions across Reynolds numbers from 4,000 to 16,000 and inlet temperatures of 400 K and 500 K. The non-uniform heat flux distribution is determined using Monte Carlo ray-tracing in Tonatiuh 2.2.4, and three-dimensional flow and conjugate heat transfer are simulated using ANSYS Fluent 2021 R1. A fin inclination angle of 600, provides the optimum thermo-fluid performance, achieving a maximum performance evaluation factor of 1.43 at a Reynolds number of 16,000 and an inlet temperature of 400 K, corresponding to improvements of 16% and 13% compared with the 90° and 45° configurations, respectively. The 60° conical fin lowered pumping power by 31.94% and 14.29% compared with 90° and rectangular fins. Among the investigated geometries, the conical fin exhibits the best overall performance, attaining a maximum Nusselt number of 235. Optimization of fin height identifies an optimum fin height to inner diameter ratio of 0.25, yielding a maximum performance evaluation factor of 1.515. The highest thermal efficiency of 68.0% is achieved with 90° fins. This optimal configuration remains consistent at both inlet temperatures, confirming its robustness and potential for improving the thermal performance of solar parabolic trough collectors. https://jhmtr.semnan.ac.ir/article_10869.html Effective thermal management is vital for spacecraft electronics facing transient heat loads. A two-dimensional enthalpy–porosity model was implemented in ANSYS Fluent to simulate phase change material melting and solidification under both terrestrial and zero-gravity conditions, capturing mushy zone behavior. A parametric study evaluated foam thickness (L*=0.3–1.0), width (16–70 mm), porosity (0.90–0.98), and material type (aluminum, copper, silicon carbide, and graphite) on peak temperature, melt evolution, and system mass. Results show that porous media can reduce maximum temperature by up to 65 K and system mass by approximately 70% while ensuring safe operation. Under zero-gravity, PCM–foam composites significantly enhance heat spreading since the conductive foam skeleton compensates for suppressed natural convection, ensuring uniform melting regardless of orientation. The findings quantify critical trade-offs between thermal performance and mass. This work provides clear quantitative robust design guidance for developing lightweight, passive thermal management systems for satellites and deep-space probes operating in harsh extraterrestrial environments.