Comparative performance analysis of direct and desiccant assisted evaporative cooling systems using novel candidate materials. (1st October 2020) - Khosravi, Nima
Highlights: Direct and desiccant assisted evaporative coolers were comparatively investigated. Five different organic evaporative cooling pad materials were tested. Vermiculite-CaCl2 composite was utilized as the desiccant material. Wood chips provided the highest evaporative cooling performance. Dew point effectiveness was 19–37% higher in desiccant assisted evaporative cooler. Abstract: In the last decade, desiccant assisted evaporative cooling (DAEC) is emerging as an alternative air conditioning (A/c) method due to its low operating costs and environmental impacts. However, for enabling wider usage of this technology, new desiccant materials (DeMs) and evaporative cooling pad materials (ECPMs), which are low cost, natural and locally available, need to be sought. In this regard, present study aims experimental investigation of different natural ECPMs in a fixed-bed solid DAEC system, where vermiculite-calcium chloride (Vmc-CaCl2 ) composite is utilized as the desiccant material. The selected ECPMs were also tested in direct evaporative cooling (DIEC) mode without using the desiccant; thereby the performances of DIEC and DAEC processes with the use of different ECPMs were comparatively investigated. Comparative analysis of different materials in DIEC and DAEC processes showed that the DAEC provides between 17 and 62% higher cooling capacity ( Q ̇ c ) than DIEC. Furthermore, achieved wet-bulb ( ε wb ) and dew point effectiveness ( ε dp ) values were found 26–50% and 19–38% higher with DAEC for different materials. According to the testing results, wood chips (WoC) was found as the best performing ECPM in both DIEC and DAEC modes. With the use of this material, obtained ε wb, a v e, ε dp, a v e and Q ̇ c, a v e in DAEC mode were found 50.6%, 52.5%, and 31.3% higher than EC, respectively. The cyclic performance analysis of DAEC also showed that; with the increasing charging temperature between 60 and 80 °C, moisture desorption rate rises from 6.60 to 15.27 g/min, while the system coefficient of performance (COP) drops in the range of 0.67–0.35.