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# A MATHEMATICAL MODEL FOR DIRECT EVAPORATIVE COOLING AIR CONDITIONING SYSTEM

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**ABSTRACT:**Performance of a direct evaporative cooler (DEC) was numerically studied at various outdoor and indoor air conditions, with geometric and physical characteristics of it being extracted based on thermal comfort criteria. For this purpose, a mathematical model was utilized based on the equations of mass, momentum, and energy conservation to deter-mine heat and mass transfer characteristics of the system. It is found that the DEC can provide thermal comfort conditions when the outdoor air temperature and relative hu-midity (RH) are in the range of 27–41 C and 10–60%, respectively. The findings also revealed that by raising the RH of ambient air, the system will reach the maximum allowed RH faster and hence a smaller heat exchanger can be used when the ambient air has higher RH. Finally, performance of the DEC in a central province of Iran was inves-tigated, and a design guideline was proposed to determine size of the required plate heat exchangers at various operating conditions. [DOI: 10.1115/1.4028179]Journal of Thermal Science and Engineering Applications. 08/2014; 6(4):1016. - [Show abstract] [Hide abstract]

**ABSTRACT:**Evaporative cooling devices are used extensively in greenhouses in arid countries to reduce excessive ambient temperatures for cultivating high value crops. Accordingly, predicting outlet air temperature and humidity from the greenhouse evaporative cooler is an essential step in determining greenhouse design and operating parameters, such as the percentage of shading and air flow rate. Halasz (1998) developed a non-dimensional model capable of predicting the outlet air temperature and humidity, and outlet water temperature for evaporative coolers. This study assesses the accuracy of Halasz’s model when applied to a typical evaporative cooler used in greenhouses in Oman. A cross-fluted design of impregnated cellulose pads was used in the validation experiments. Combinations of two air flow rates and two water flow rates were studied. When model predictions were compared to measured results, it was found that the model accurately predicted the outlet air and water conditions. Within the range of operating parameters investigated, the average percentage predictive error for the outlet air and water temperatures ranged from 1.16 to 2.86% (SD ≤ 1.84%) and −4.91 to −1.30% (SD ≤ 2.29%), respectively. The average percentage predictive error for the outlet humidity ratio was between −2.21 and 0.43% (SD ≤ 4.82%).Biosystems Engineering. 01/2010; 107(2):86-96. - [Show abstract] [Hide abstract]

**ABSTRACT:**Performance of a direct evaporative cooler (DEC) was numerically studied at various outdoor and indoor air conditions, with geometric and physical characteristics of it being extracted based on thermal comfort criteria. For this purpose, a mathematical model was utilized based on the equations of mass, momentum, and energy conservation to determine heat and mass transfer characteristics of the system. It is found that the DEC can provide thermal comfort conditions when the outdoor air temperature and relative humidity (RH) are in the range of 27–41 oC and 10–60%, respectively. The ﬁndings also revealed that by raising the RH of ambient air, the system will reach the maximum allowed RH faster and hence a smaller heat exchanger can be used when the ambient air has higher RH. Finally, performance of the DEC in a central province of Iran was investigated, and a design guideline was proposed to determine size of the required plate heat exchangers at various operating conditions.Thermal Science and Engineering Applications. 08/2014;

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