Experimental study of novel desiccant coated energy exchanger employing PCM – Silica gel working pair for air conditioning and thermal energy storage application

Advancement of air conditioning systems is a key focus because of high energy usage and rising demand for better air quality. Desiccant air conditioning offers enhanced energy management and sustainability features. Phase change material (PCM) based thermal energy storage systems are effective for efficient thermal energy storage applications. Hence, the practicality of integrating PCM with desiccant coated energy exchangers (DCEE) for air conditioning and thermal energy storage necessitates experimental investigation. Therefore, a novel desiccant coated circular fin tube energy exchanger (DCCEE) has been designed and fabricated in this study. DCCEE is integrated with PCM to assess its dehumidification and thermal energy storage characteristics. The key highlight of this work is the use of PCM-silica gel as the working pair instead of conventional water–silica gel. A linear driving force model is used to evaluate the silica gel’s adsorption and desorption kinetics. Experiments have been designed by response surface methodology employing the central composite design technique to analyze the effect of independent parameters on the response of DCCEE. The variation in the cooling capacity, adsorption effectiveness, and PCM temperature at different input conditions has been judiciously evaluated. The adsorption capacity of silica gel is 0.332 g/g at a relative pressure of 0.9. Under the air velocity of 2.5 m/s, the total cooling capacity of DCCEE has the highest value of 3.55 kW, which consists of 1.18 kW sensible cooling capacity and 2.37 kW latent cooling capacity. At the 20 °C and 22 g_wv/kg_da condition, the adsorption effectiveness reaches a maximum value of 0.82. During adsorption, PCM melts in response to different input parameters and reaches phase change point in 490 s (air temperature), 540 s (air velocity), and 570 s (relative humidity), respectively. To conclude, this study elucidates the feasibility of integrating PCM with DCEE and provides a reference for DCEE system design.