Passive cooling system aided with personal evaporative cooling and desiccant-trombe wall dehumidification for hot humid climate

Abstract

This study investigates the performance of a hybrid cooling system for an office space. The hybrid system combines a phase change material (PCM) storage layer with a melting temperature of 25 ºC to cool the supply air and a personalized evaporative cooler (PEC) system to provide local cooling for the occupants. In addition, humidity of the supply air is controlled using a solid desiccant wheel regenerated via an auxiliary heater assisted with a Trombe wall. Moreover, an evaporative cooler and a sensible wheel are used to assist in cooling the supply air. The combined system can be used primarily for hot humid climates in office spaces. The system should meet the space load, indoor air quality, and minimum fresh air requirements (7 l-s per person) set by ASHRAE standards and can provide thermal comfort during daytime with minimum electric energy consumption by using only small fans and an auxiliary heater. Mathematical models for each component have been implemented to simulate their performance and then evaluate the performance of the overall system. A bioheat model that can predict human thermal response such as skin and core temperatures has been used to predict the overall thermal comfort of the occupants. A case study for an office space located in Beirut is developed to assess the performance of the proposed hybrid cooling system during the summer months and to check the resultant overall thermal comfort of the occupants. The Trombe wall proved to be effective for regeneration purposes as it achieved a 55 percent thermal energy reduction compared to relying only on the auxiliary heater for regeneration. Overall, the proposed system achieved savings up to 87percent of the total operation cost compared with the consumption of a conventional AC unit over the entire cooling season.