Effects of Ratio of Dynamic Circulation to Evaporation Rates on Exergy and Cooling Efficiencies an Evaporative Cooler

Document Type : Full Length Research Article

Author

Department of Mechanical Engineering, Faculty of Engineering, University of Birjand, Birjand, Iran

Abstract

The expected performance characteristics of a wet media in an evaporative cooler with the specified geometric and material aspects are reducing the dry-bulb temperature and increasing the moisture content of the air outlet. Inlet air conditions are not under the control of the designer or the operator, but the choice of media geometry and fabric, the external factors such as the water circulation rate, and the velocity of air passing through the media could be controlled by the designer. Based on cooling performance for the excelsior of aspen wood pad, the minimum amount of ratio of the static circulation to evaporation rates is about 8 to 12, which has been mentioned in the literature. In this work, for the cellulosic pad by considering the exergy and cooling efficiencies, the optimal ratios of circulation to evaporation rates are presented for different air velocities. It can be seen that under the constant inlet air conditions, by increasing the air velocity as: 0.5, 1.0 and 1.5 m/s, the maximum exergy efficiency values are 0.10, 0.13 and 0.18 respectively and there are some specified values (minimum) for the ratios of water circulation to evaporation rates between 2 and 2.8 for the typical cellulose pad. However, for the same air velocities, maximum cooling efficiencies occur at lower exergy efficiencies, such as 0.03, 0.04, and 0.045, respectively.

Keywords

Main Subjects

References

[1]    John, R.W., 1996. Evaporative Air Conditioning Handbook, second ed., Chapman & Hall, New York.
[2]    Abohorlu Doğramacı, P., Riffat, S., Gan, G. and   Aydin, G., 2019. Experimental study of the potential of eucalyptus fibres for evaporative cooling, Renewable Energy, 131, pp.250-260.
[3]    Dowdy, J.A., Handy, E.T., 1986. Heat- and Mass-Transfer Coefficients, ASHRAE Transactions, 92(2), pp.60-70.
[4]    Karaca, C., Yıldız, Y., Dağtekin, M. and Gümüş, Z., 2016. Effect of water flow rate on cooling effectiveness and air temperature change in evaporative cooling pad systems, Environmental Engineering and Management Journal, 15(4), pp.827-833.
[5]    Martínez, P., Ruiz, J., Martínez, P.J., Kaiser, A.S., and Lucas, M., 2018. Experimental study of the energy and exergy performance of a plastic mesh evaporative pad used in air conditioning applications, Applied Thermal Engineering, 138, pp.675-685.
[6]    Paschold, H., Li, W.W., Morales, H., and Walton, J., 2003. Laboratory study of the impact of evaporative coolers on indoor PM concentrations, Atmospheric Environment, 37(8), pp.1075-1086.
[7]    Sohani, A., Zabihigivi, M., Moradi, M.H., Sayyaadi, H., and Balyani, H.H., 2017. A comprehensive performance investigation of cellulose evaporative cooling pad systems using predictive approaches, 110, pp.1589-1608.
[8]    Franco, A., Valera, D.L., Madueño, A., and Peña, A., 2010. Influence of water and air flow on the performance of cellulose evaporative cooling pads used in mediterranean greenhouses, Transactions of the ASABE, 53(2), pp.565-576.
[9]    Franco, A., Valera, D.L., Peña, A., and Pérez, A.M., 2011. Aerodynamic analysis and CFD simulation of several cellulose evaporative cooling pads used in Mediterranean greenhouses, Computers and Electronics in Agriculture, 76(2), pp.218-230.
[10] He, S., 2015. Performance Improvement of Natural Draft Dry Cooling Towers Using, School of Mechanical & Mining Engineering, 53(10), pp.122-130.
[11] Takakura, T., 1982. Heating, Ventilating and Cooling Greenhouses, Journal of Agricultural Meteorology, 38(1), pp.65-70.
[12] Tejero-González, A., and Franco-Salas, A., 2021. Optimal operation of evaporative cooling pads: A review, Renewable and Sustainable Energy Reviews, 151, 111632.
[13] Rong, L., Pedersen, P., Jensen, T.L., Morsing, S., and Zhang, G., 2017. Dynamic performance of an evaporative cooling pad investigated in a wind tunnel for application in hot and arid climate, Biosystems Engineering, 156, pp.173-182.
[14] Vishnu, S., 2014. Factors affecting the performance characteristics of wet cooling pads for cooling pads for data center applications, (M. Sc Thesis, The University of Texas at Arlington).
[15] Omidi Kashani, B., 2022. Increase of energy efficiency ratio of a direct evaporative cooler by dynamic behavior with energy and exergy analysis, Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science, 236(7), pp.3818-3830.
[16] Plot Digitizer, Department of Physics at the University of South Alabama in Mobile, AL.
[17] Stull, R., 2011. Wet-bulb temperature from relative humidity and air temperature, Journal of Applied Meteorology and Climatology, 50(11), pp.2267-2269.
[18] Tetens, O., 1930. About some meteorological terms, Zeitschrift Geophysic, 6, pp.297-309.
[19] Dincer, I., and Rosen, M.A., 2015. Exergy Analysis of Heating, Refrigerating and Air Conditioning: Methods and Applications, Elsevier.
[20] Kenneth, W., 1994. Advanced Thermodynamics for Engineers, McGraw-Hill, New York.
[21] Farmahini-Farahani, M., Delfani, S., and Esmaeelian, J., 2012. Exergy analysis of evaporative cooling to select the optimum system in diverse climates, Energy, 40(1), pp.250-257.
[22] Nada, S.A., Fouda, A., Mahmoud, M.A., and Elattar, H.F., 2019. Experimental investigation of energy and exergy performance of a direct evaporative cooler using a new pad type, Energy and Buildings, 203, pp.109449-109449.
[23] Santos, J.C., Barros, G.D.T., Gurgel, J.M., and Marcondes, F., 2013. Energy and exergy analysis applied to the evaporative cooling process in air washers, International Journal of Refrigeration, 36(3), pp.1154-1161.
[24] EES: Engineering Equation Solver, F-Chart Software: Engineering Software.

Files

History

  • Receive Date: 01 June 2021
  • Revise Date: 15 November 2022
  • Accept Date: 20 November 2022

Share

How to cite

Statistics