Journal of Heat and Mass Transfer Research
https://jhmtr.semnan.ac.ir/
Journal of Heat and Mass Transfer Researchendaily1Mon, 20 Jun 2016 00:00:00 +0430Mon, 20 Jun 2016 00:00:00 +0430Spectral quasi-linearization approach for unsteady MHD boundary layer flow of casson fuid due to an impulsively stretching surface.
https://jhmtr.semnan.ac.ir/article_422.html
The present paper seeks to examine a numerical method of solution called spectra quasi-linearization method (SQLM) to the problem of unsteady MHD boundary layer flow of Casson fluid due to an impulsively stretching surface under the influence of a transverse magnetic field, which is an important physical phenomena in engineering applications.The study extends the previous models to account for a classical non-newtonian fluid called Casson fluid under the influence of a transverse magnetic field. The flow model is described in terms of a highly nonlinear partial differential equations. The method of solution Spectral quasi-linearization methods(SQLM) seeks to linearised the original system of PDEs using the Newton-Raphson based quasilinearization method (QLM). The numerical resultsfor the surface shear stress are compared with those of the analytical approach results, and they are found to be in good agreement. The flow controlling parameters are found to have a profound effect on the resulting flow profiles.It is observed that there is a smooth transition from the small time solution to the large time solution. The magnetic field significantly affects the flow field and skin friction coefficient. Indeed, skin friction coefficient is found to decreaserapidly, initially, in small time interval before attaining a steady state for large time.Radiation and Chemical Reaction Effects on Unsteady Coupled Heat and Mass Transfer by Free Convection from a Vertical Plate Embedded in Porous Media
https://jhmtr.semnan.ac.ir/article_3951.html
A numerical solution is presented for unsteady coupled heat and mass transfer by natural convection from a vertical plate embedded in a uniform porous medium in the presence of thermal radiation and chemical reaction effects. The governing equations for this problem were developed and non-dimensionalized and the resulting equations were then solved numerically by an explicit finite-difference scheme. The Roseland approximation is used to describe the radiative heat flux in the energy equation. The solutions at each time step have been found to reach the steady state solution properly. The numerical results are presented in the graphical form to show the effects of material parameters including the thermal buoyancy, the solutal buoyancy, Reynolds number, the inverse thermal radiation parameter, the permeability parameter, Prandtl number, Schmidt number and the chemical reaction parameter on the skin-friction coefficient, the Nusselt number, the Sherwood number, the velocity profiles, the temperature profiles and the concentration profiles in the boundary layer.Heat Transfer Correlation for Two Phase Flow in a Mixing Tank
https://jhmtr.semnan.ac.ir/article_4228.html
Mixing tanks equipped with mechanical stirrer are broadly applied in chemical and petrochemical industries, due to their variety of industrial process requirements. In this study, helical single blade mixer was designed applying CATIA and then mixing of fluid and solid particles, in a tank with this agitator was examined by OpenFOAM. For velocity distribution in the mixing tank, continuity, momentum equations, boundary conditions and coding were performed applying C++ language scripts in the software. The results of velocity distributions in three directions coordinates indicated that the efficiency of helical blade mainly correlated to axial and tangential flows.&nbsp; The radial flow has less important role in mixing operation. Moreover, solid particles concentration distribution were computed in the fluid phase .It was exhibited that the particles were distributed homogeneously in the tank. In addition, temperature distribution was obtained applying continuity, momentum and energy equations as well as utilizing necessary code and boundary conditions in the software. Consequently, a correlation for Nusselt number as a function of Re, Pr and Vi was acquired by using temperature profile and dimensional analysis. The results achieved are in good agreement with those available in literature.The effect of SiO2 nanoparticle on the performance of photovoltaic thermal system: Experimental and Theoretical approach
https://jhmtr.semnan.ac.ir/article_4229.html
The low conversion efficiency of solar cells produces large amounts of thermal energy to the cells, and with an increase in the temperature of solar cells, their electrical efficiency decreases. Therefore, a hybrid photovoltaic thermal system improves the overall efficiency of the system by adding thermal equipment to the solar cell and removing excessive heat from these cells. In this paper, we study the effect of SiO2/water nanofluids on thermal and electrical efficiency of domestic photovoltaic thermal systems (DPVT) theoretically and experimentally. In the theoretical part, based on the control-volume finite-difference approach, an explicit dynamic model was developed for a single-glazed flat-plate water-heating photovoltaic thermal collector with closed loop cooling system with withdrawing urban water from the storage tank. The model accuracy was verified in comparison with the measured experimental data. Experimental results show that by increasing concentrations of nanofluid, the thermal and electrical performance has improved and overall efficiency decreased by increasing the diameter of the nanoparticles. The overall efficiency of the DPVT for 0 and 3 weight percent of SiO2/ water nanofluids with a diameter of 11-14 nanometers increased to 5.4% and 7.76% compared to base fluid, respectively.Numerical analysis of gas flows in a microchannel using the Cascaded Lattice Boltzmann Method with varying Bosanquet parameter
https://jhmtr.semnan.ac.ir/article_4230.html
Abstract. In this paper, a Cascaded Lattice Boltzmann Method with second order slip boundary conditions is developed to study gas flows in a microchannel in the slip and transition flow regimes with a wide range of Knudsen numbers. For the first time the effect of wall confinement is considered on the effective mean free path of the gas molecules using a function with nonconstant Bosanquet parameter instead of the constant one. The constant-force driven and pressure-driven gas flows in a long microchannel are simulated under different conditions. The results of the velocity profile, pressure distribution, and mass flow rate are in good agreement with the benchmark solutions and experimental data reported in the literature. The Knudsen minimum phenomenon is also well captured by the present model. The proposed Cascaded Lattice Boltzmann Method shows a clear improvement in predicting the flow behaviors of microchannel gas flows for the previous classic and Cascaded Lattice Boltzmann MethodEFFECT OF VISCOUS DISSIPATION ON STEADY NATURAL CONVECTION HEAT AND MASS TRANSFER FLOW THROUGH A VERTICAL CHANNEL WITH VARIABLE VISCOSITY AND THERMAL CONDUCTIVITY
https://jhmtr.semnan.ac.ir/article_4260.html
In this study, effects of viscous dissipation and variable physical properties on steady natural convection heat and mass transfer flow through a vertical channel were investigated. The variability in viscosity and thermal conductivity are considered linear function of temperature. The governing equations are transformed into a set of coupled nonlinear ordinary differential equations and solved using Differential Transformation Method (DTM). Results obtained were compared with exact solution when some of the flow conditions were relaxed and results from DTM show an excellent agreement with the exact solution which was obtained analytically. The influence of the flow parameters on fluid temperature, concentration and velocity are presented graphically and discussed for variations of the governing parameters. From the course of investigation, it was found that increasing viscous dissipation causes fluid temperature, velocity as well as the skin friction on the surface of both channels to increase. However, increasing the fluid viscosity retards the fluid motion and causes fluid temperature to decrease.Heat transfer enhancement in a spiral plate heat exchanger model using continuous rods
https://jhmtr.semnan.ac.ir/article_4261.html
This study presents an innovative and simple way to increase the rate of heat transfer in a spiral plate heat exchanger model. Several circular cross-section rods, as continuous vortex generators, have been inserted within the spiral plate heat exchanger in the cross-stream plane. The vortex generators are located at various azimuth angles of &alpha;=30◦, 60◦, 90◦, and 120◦ with non-dimensional diameters of d/H=0.3, 0.4, and 0.5. Computations have been carried out numerically by means of the finite volume approach under different Dean numbers (De) ranging from 500 to 1500 in the laminar regime. The flow physics within the advanced spiral heat exchanger model has been discussed using several velocity and temperature contours. It was found that by inserting the continuous vortex generators in the cross-stream plane of a spiral plate heat exchanger, the unsteady flow develops within the channel in which the rate of unsteadiness is proportional to d/H and De directly and to azimuth angle inversely. The maximum heat transfer enhancement with respect to the conventional spiral plate heat exchanger (without continuous vortex generators) is found to be 341% for &alpha;=30◦, d/H=0.5, and De=1500. Additionally, values of pressure drop penalty and thermal-hydraulic performance have been determined accordingly.The effects of added hydrogen to the premixed of methane and air in a MEMS channel
https://jhmtr.semnan.ac.ir/article_4358.html
In this paper, the effect of adding hydrogen to the composition of methane and air in a micro combustor is investigated by a three-dimensional numerical method. First, the results of the current study in determining the wall temperature of the micro combustion chamber are compared with those obtained from the experimental and numerical results of the previous research. By confirming the numerical solution of this study, the effect of adding hydrogen to the mixture of methane and air on the distribution of temperature, pressure and outlet velocity of the gases is calculated numerically. The numerical results show that increasing the percentage of hydrogen to the mixture of methane and air leads to nonlinear changes in the outlet velocity, pressure, and temperature. In addition, the results show that by increasing the percentage of hydrogen to 2.5% and 5%, the maximum outlet velocity of the gases and minimum temperature are produced in the micro combustor, respectively.Coupled Integral Equations Approach in the Solution of Luikov Equations with Microwave Effect
https://jhmtr.semnan.ac.ir/article_4368.html
The objective of this study is to present a mathematical modeling and solution approach for the drying process of spheroidal solids with the application of microwave in capillary porous media based on the Luikov equations, composed of a system of linear and coupled partial differential equations arising from the energy, mass and pressure balances inside the solid matrix. Additionally, the power generation term from the application of microwaves is added to this differential system. The solution to this problem is achieved through a Coupled Integral Equations Approach (CIEA), whose objective is the transformation of the initial PDE system into an ODEs one. A computer code was developed in FORTRAN 90/95 programming language, which uses the subroutine IVPAG from the IMSL library to solve the system of ODEs from the application of the CIEA. The results obtained were compared with other previously reported in the literature to verify the methodology and showed satisfactory agreement.Experimental study on the thermal conductivity and viscosity of transformer oil -based nanofluid containing ZnO nanoparticles
https://jhmtr.semnan.ac.ir/article_4369.html
This study investigates the effect of ZnO nanoparticles to transformer oil on the thermal conductivity and dynamic viscosity. The consequence of the temperature and nanofluid concentration as an important parameters have been explored on the thermal conductivity and viscosity of the samples. The results indicated that the thermal conductivity of the nanofluid was higher than that of the pure transformer oil at the temperature of 25&deg;C. Also, a rise in the nanoparticle concentration of transformer oil increased the thermal conductivity of nanofluid. Besides, the thermal conductivity at the volume fractions of 0.05% and 1% increased by approximately 4.61% and 11.53%, respectively. The dynamic viscosity reached the highest level at maximum volume fraction in all temperatures. In addition, an increase in the temperature reduced the dynamic viscosity of both the pure transformer oil and the nano-oil. At a given temperature, a rise in the volume fraction of ZnO nanoparticles enhanced the dynamic viscosity. Moreover, to predict the dynamic viscosity of nanofluid, a new correlation has been presented as a function of temperature and volume fraction with R-Sq=0.9913.Time Dependent Heat Source Estimation by Conjugate Gradient Method in Multi-Layers System for Hyperthermia of Breast cancer
https://jhmtr.semnan.ac.ir/article_4411.html
Hyperthermia is a form of cancer treatment where the temperature of the tumor is elevated to levels that induce its elimination. This paper discusses using a heating power source to destroy breast cancer cells. The geometry of the breast tissue is represented as a hemisphere containing three layers; muscle, gland, and fat. The conjugate gradient method that is one of The most powerful iterative methods was used to solve the inverse heat conduction problem via the Pennes bioheat equation in an axisymmetric coordinate system, where the irregular region in the physical domain (r,z) was transformed into a rectangle in the computational domain (ξ, η). The performance of the algorithm was evaluated on a tested point located at the (5, 2) position, accounting for two temperature increments. The results confirmed the accuracy and viability of the algorithm, which makes this approach promising for the actual application for breast cancer treatment soon.Wall thermal inertia effects of pulsatile flow in a ribbed tube: A numerical approach
https://jhmtr.semnan.ac.ir/article_4647.html
In present paper, heat transfer of pulsatile flow in ribbed tube was investigated numerically by considering the effect of thermal inertia of solid wall thickness. To this purpose, CVFV (Control Volume Finite Volume) technique with collocated grids arrangement was adopted to discretize momentum and energy equations. Rhie and Chow interpolation method was employed to avoid checker-board of pressure field in numerical simulation. The well-established SIMPLE (Semi-Implicit Method for Pressure Linked Equations) method was utilized to deal with the coupling of pressure and velocity in momentum equation. Stone&rsquo;s Strongly Implicit Procedure (SIP) was used to solve the set of individual linear algebraic equations. Womersley number, Reynolds number, velocity amplitude and wall thickness ratio are four essential parameters which influence heat transfer and Nusselt number in pulsatile flow in a ribbed tube. It was deduced by varying Womersley number Nu does not change. Nu enhances almost 19% by augmentation of wall thickness ratio from 0.125 to 1. It was shown by increasing velocity amplitude from 0.1 to 0.8, Nu reduces almost 4.7%.Analytical Solution of Non-ideal Gaseous Slip Flow in Circular Sector Micro-channel
https://jhmtr.semnan.ac.ir/article_4455.html
AbstractAnalytical solutions of gaseous slip flow in a microchannel with different cross-sections play an important role in the understanding of the physical behavior of gases and other phenomena related to it. In this paper, the fully developed non-ideal gaseous slip flow in circular sector microchannel is investigated using the conformal mapping and the integral transform technique to obtain the analytical exact solution. Van der Waals equation is used as the equation of state for a non-ideal gas.It is developed the models for predicting the local and mean velocity, normalized Poiseuille number,and the ratio of density for conditions where the small radius of the circular sector cross-section is zero (r1*→0) and is the opposite of zero (r1*≠0, r1*=10µm).Rarefication process and effects of wall slippage are important physical phenomena that are studied. The results show that the rarefication process depends on Knudsen number, and cross-section geometry. In order to validate the analytical solution, the results of the problem are compared to the analytical and numerical solutions. Good agreement between the present study and other solutions has confirmed.Developing a Model for Predicting the Outlet Gas Temperature of Natural Gas Pressure Reduction Stations to reduce Energy loss
https://jhmtr.semnan.ac.ir/article_4469.html
Natural gas stream must be preheated before pressure reduction takes place at natural gas pressure reduction station (PRS). It ensures that the natural gas stream remains above hydrate-formation zone. Heaters are used to prevent this problem. There is no precise method for determining the adjustment points of heaters; and the gas is usually heated to a temperature higher than the required temperature leading to the energy loss in heaters. In the present paper, the outlet gas temperature of regulator was predicted to prevent the energy dissipation by an applied analysis through thermodynamics equations and considering the deviation of natural gas from the ideal gas state using MATLAB software. The prediction of outlet temperature and application of control mechanisms made the temperature close to the standard temperature, so that avoiding the formation of destructive hydrate phenomenon, prevented the dissipation of 7983.7 standard cubic meter of natural gas and reduced 15.29 tone greenhouse gas emissions in a year at the PRS under study. The economic analysis of the proposed system has been carried out using Payback ratio method. The payback period of implementation of this control system is only less than one year. Results of comparison between the measured output temperature and calculated temperature through the software indicated an average difference of 9%.Forced convective heat transfer of non-Newtonian CMC-based CuO nanofluid in a tube
https://jhmtr.semnan.ac.ir/article_4545.html
In the present study, the thermal and rheological behavior of power-law non-Newtonian CMC-based CuO nanofluid in a tube is studied using ANSYS FLUENT software. Constant heat flux of 6000 W/m2 is subjected to the tube walls and the viscosity of nanofluid is assumed to be a function of shear rate, and temperature simultaneously. Two velocity profiles are considered as an inlet boundary condition: fully developed velocity and uniform velocity. Volume fractions of 0%-4%, and the Reynolds numbers of 600-1500 are considered in the simulations. For both velocity profiles, temperature and shear rate have considerable influence on the viscosity. Local heat transfer coefficient along the tube increases with the volume fraction, however, volume fractions less than 1.5% has an effect on local heat transfer slightly. It is revealed that as the Reynolds number enhances, local heat transfer and the average Nusselt number decrease. In conflict with previous investigations, the present results show that average Nusselt number is reduced by increasing the volume fraction of nanoparticles.Longitudinal vortex rolls in fluids
https://jhmtr.semnan.ac.ir/article_4648.html
This paper is concerned with longitudinal vortex rolls in fluids. The longutudinal rolls are observed in the sea surface, desert, and atmosphere. However, origin of the vortical motions are not clear, so that in this study laboratory experiments and theoretical analyses have been conducted to elucidate the formation mechanism of the longitudinal vortex rolls in laboratory . As the results, it becomes clear that these vortex rolls are generated by the interaction of the thermal convection and the shear force by the flow. That is, as far as these two effects are existed, irrespective of other conditions are different, quite similar longitudinal vortex rolls appear. Take for example, in dayly our lives when it is fine, we often ovserve longitudinal vortex rolls in the sky, when we look through the outside from the airplane window, we see the longitudinal rows of clouds, and when wo go on board , we notice the longitudinal wave lines on the sea surface.Statistical analysis of nanofluid heat transfer in a heat exchanger using Taguchi method
https://jhmtr.semnan.ac.ir/article_4708.html
In this study, a statistical experimental design method (the Taguchi method with L9 orthogonal array robust design) was performed to optimize experimental conditions such that to maximize the Nusselt number of Al2O3-water nanofluids in a double tube counter flow heat exchanger. The controllable factors were selected at three sets of conditions including temperature (45, 55, and 65℃), concentration (0, 0.05, and 0.15 vol.%), and flow rate (7, 9, and 11 l/min) of the nanofluid. Analysis of the obtained results revealed that the flow rate plays a key role in the Nusselt number of nanofluid with 63.541%. The optimal levels were defined for the three factors including the nanofluid concentration of 0.15 vol.%, the nanofluid temperature of 65℃,and the nanofluid flow rate of 11 l/min. The predicted Nusselt number of nanofluid under these conditions was 322.633. The confirmation test was also performed at the optimal conditions, by which good consistency was found between the experimental and the predicted results.Experimental evaluation of summer thermal comfort in various types of Sardab (Cellar): underground space in Iran vernacular houses
https://jhmtr.semnan.ac.ir/article_4714.html
This article aims to evaluate the effect of three types of Sardab (Cellars) on thermal comfort conditions. Two vernacular buildings in Yazd have been selected as case studies. In the Rasoulian house, a sardab with a water pond has been defined as case A and a Sardab without pond has been chosen as case B. Case C is a Sardab without pond in Mortaz house. Using experimental data, environmental parameters were analyzed for a month in two consecutive years. Using measured data, the values for Predicted Mean Vote (PMV) and Predicted Percentage Dissatisfied (PPD) have been calculated. The results show a considerable reduction in the air temperature (up to 20 oC) and an increase in the relative humidity of the air (up to 50%) in case A (the Sardab with pond). The sardabs without pond (Case B and C) presented lower efficiencies. Variations in daily temperatures have been presented in three cases with ceilings elevated at different heights. While the sardab that is placed completely underground presented the lowest temperature, in two other sardabs, the average air temperature was 2-3 degrees higher. According to the results, in a hot and dry climate, application of all sardab types, either with or without a pond, elevated or underground, would improve the thermal comfort condition and the energy efficiency of buildings.THREE DIMENSIONAL VISCOUS DISSIPATIVE FLOW OF NANOFLUIDS OVER A RIGA PLATE
https://jhmtr.semnan.ac.ir/article_4715.html
In this study, the physical perspectives on three-dimensional flow of base fluids with nanoparticles are comparatively investigated under the effect of viscous dissipation using Runge-Kutta 4th order numerical procedure. With the help of similarities transformations, the mathematical model which are described as partial differential equations are transmuted into ordinary differential equations. As said, the Runge-Kutta method, assisted by the shooting strategy, is designed to deal numerically with the resulting set of non-linear differential equations. Highlights of the flow-field and thermal field are illustrated quantitatively in plots. Results for local skin friction coefficients and local Nusselt number are reported and analyzed tabularly. The accuracy of present study is verified in comparison to existing literatures and we have identified an astounding understanding. Also, results indicate that, the velocity profile is enhanced by the modified Hartmann number and stretching ratio parameters. The nanofluid, in fact, has elevated skin friction values and is also more suitable for increasing the rate of heat transfer.Disinfection process with solar drying system
https://jhmtr.semnan.ac.ir/article_4716.html
COVID-19 has become a health threat around the world. Mask deficiency can be expected during a pandemic infection. The stability of viruses at different temperatures and relative humidity was assessed according to the type of contaminated surface material. With increasing temperature, the permanence of viruses decreases, and in proportion to the increase in temperature should not be damage to the quality of objects. Solar disinfection is one of the new methods of using renewable resources. By designing an integrated solar drying system with the phase change material, the internal temperature of the system reaches 54 ̊ C in April and the masks are disinfected with 3036 Wh/m2 internal cumulative solar radiation. By using the appropriate equipment in the system, the temperature difference inside and outside the system was reached 30 ̊C. A correlation coefficient of 95% in the MATLAB confirmed that the curve fit was good. The main purpose of this research is to identify appropriate solutions for disinfection and consultation with scientific literature. The results showed that the most appropriate hygienic and economical disinfection method was the use of solar energy.Thermodynamic Properties of Monatomic, Diatomic, and Polyatomic Gaseous Natural Refrigerants: A Molecular Dynamics Simulation
https://jhmtr.semnan.ac.ir/article_4740.html
Owing to their lower adverse environmental impacts, natural refrigerants have recently attracted a huge deal of attention. In this regard, the present study is aimed to evaluate the thermodynamic properties of different gaseous natural refrigerants at the molecular level using molecular dynamics (MD) simulations. In this context, the density (as a representative of structural features), enthalpy, and specific heat capacity (as representatives of energy properties) of several natural gaseous refrigerants including helium, nitrogen, methane, and ethane were assessed. Lennard-Jones potential was used for simulation of helium and nitrogen while AIREBO potential and OPLS-AA force-fields were employed for simulation of methane and ethane as polyatomic hydrocarbon refrigerants. Simulations are carried out at various temperatures above the boiling point and pressures of 1, 2, and 5 bar. MD results were in good agreement with the experimental data. Among the applied potentials, AIREBO potential offered results closer to the experimental data as compared with OPLS-AA force-field. The methane-ethane mixture was also addressed at different pressures and compared with the Peng-Robinson equation of state. The results of this study indicated that molecular dynamics can be employed as a reliable tool for predicting the thermodynamic properties of natural refrigerants. The results can be used in the refrigeration cycles.Modeling of the transient absorption of particulate drugs in the human upper airways
https://jhmtr.semnan.ac.ir/article_4753.html
Predicting the dynamics of aerosols in the respiratory tract is crucial for the analysis of toxic effects of particulate matters and to the respiratory targeted drug delivery. The present work focuses on evaluating the transient absorption of drug particles on the airway walls of the respiratory tract. For this purpose, simulations of airflow and particulate matters inside a three-dimensional model of respiratory airways were coupled to a one-dimensional drug absorption model. The drug absorption from mucus to the respiratory walls was studied using the transient mass transfer equations in a multilayer model. Different breathing rates of 5, 7.5, and 10 Lit/min were considered in the simulations. Particles with different sizes of 2, 5, 10, and 30µm were released at the entrance of the oral cavity during the inspiration phase. The airflow velocity distribution, particle concentration, and flux of drugs at the interface of mucus-tissue were studied in detail. The transient absorption process that occurred over the breathing time considered of 4 s was evaluated. The results showed that the drug mass flow rate at the mucus-tissue interface and the drug concentration in the tissue layer decreases with time. Also, it was found that after inspiration, the location of the maximum concentration changes from mucus to the tissue layer.