Experimental performance and evaluation of direct evaporative cooling system coupled with a desiccant wheel in a closed greenhouse

Abstract

The greenhouse is one of the most advanced technologies protecting products against inconvenient climates. However, high humidity and temperature throughout the summer, particularly in closed greenhouses, have a reverse effect on the crops. In such conditions, reducing the temperature inside the greenhouse seems indispensable. Therefore, in this study, two different patterns of cooling systems, namely, direct evaporation and mixed direct evaporative desiccant rotatory wheel, were designed and developed in Tehran. The results of these models were evaluated, compared, and modeled in TRNSYS. Subsequently, for performance prediction of these models, they were examined in closed greenhouses located in 5 regions in Iran: Astara, Ahvaz, Bandar-abbas, Tehran, and Shiraz. The temperature and humidity in different parts of the greenhouse were measured and reported to assess the performance of these two systems in terms of the capability to supply the required cooling load, energy consumption, and functional expenses. The experimental results indicated that the direct evaporative cooling system isn't acceptable for cooling the closed greenhouse in the preceding regions. This system in conventional greenhouses can be applicable only in Astara, Tehran, and Shiraz. Although all traditional greenhouses in Tehran use a direct evaporative cooling pad system, such a system cannot be used for cooling the closed greenhouses. Also, findings of the present study indicated that despite the 10% increase in radiation intensity and 7% increase in temperature in the case of evaluating the mixed evaporative desiccant rotatory wheel system, the temperature changes of greenhouse in this system followed a similar behavior, and 8% reduction in functional expenses was also confirmed.