Significance of parameters affecting the performance of a passive down-draft evaporative cooling (PDEC) tower with a spray system

Abstract

h i g h l i g h t sIt demonstrates the significance of main parameters including those have not been well treated in the literature. It presents practical design guidelines for main parameters so as to significantly improve the performance of the system. It ensures that the performance of the system varies with many factors, rather than one dominant factor. It formulates two mathematical models that predict outlet air temperature and velocity. a b s t r a c t PDEC towers with spray systems are known to achieve substantial energy savings. Various parameters such as the wet-bulb depression, the tower height, and the wind speed have been known to be key factors affecting the performance of the system. To date, the significance of these parameters and other important factors have not been adequately treated in the literature. There also has been a lack of models that can successfully investigate potential benefits of the system under various conditions where this particular system could be applicable. To address these critical issues, this study performed a parametric analysis by using a FLUENT model validated against experimental data. It demonstrated the significance of individual parameters including water droplet sizes. As a result, practical design guidelines for important system parameters were presented. A statistical analysis was then used to formulate analytic models that account for all of the relationships found in this study between the parameters and the supply air conditions of the system. Two regression equations were formulated for predicting supply air temperature and velocity.

Performance control of a spray passive down-draft evaporative cooling system

“…These analytical models embrace such key variables as a water droplet size and velocities over a wind catcher and a cross-section of a spray PDEC tower. They are validated against experimental data and the details of the development of the models can be found in [24]. They are the only models that adequately account for air mass flow rates and water droplet sizes, which are critical in the prediction of the performance of a spray PDEC system.…”

“…As the enhancement of energy efficiency has been one of the key areas in building sectors that consume energy most, a spray PDEC system has been adopted in the cooling of buildings in order to utilize the benefits of the direct evaporative cooling [5,6,12,[18][19][20][21][22]. To date, many studies focused on this particular system and advanced the performance of the system [1,5,6,12,[23][24][25].…”

“…It could also be an obstacle when a spray PDEC system plays a role of a primary cooling system, which requires meeting all the variable cooling loads. In that point of view, one of the obstacles of a spray PDEC system is that the cooling performance is limited to the wet-bulb depression [1,5,12,24]. As the cooling capacity of a spray PDEC system is constrained to the climatic conditions, it may not be able to respond all space cooling demands that vary with time significantly.…”

“…As the cooling capacity of a spray PDEC system is constrained to the climatic conditions, it may not be able to respond all space cooling demands that vary with time significantly. It causes a significant variation in the indoor thermal environment as the maximum capacity of the system varies with outdoor air conditions [5,25]. A spray PDEC system is typically suitable for a hot dry climate and water resources are fairly limited in this region [4,5,8,12].…”

Selecting Nozzle Arrangement of a Chimney Tower to Reduce the Temperature and to Increase the Entrainment Mass Flow

“…Basically the multi-stage model is the development from the predecessor single stage model to improve the performance. Some design and investigations were reported in various publications, such as in experiment [1,2,3] also by using a simulation CFD approach [4,5,6]. In order to improve the cooling effect, additional water spray from the nozzle into the chimney can be useful [7].…”