Validation of Halasz’s non-dimensional model using cross-flow evaporative coolers used in greenhouses

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%).