Performance evaluation of adsorption thermophysical battery for air conditioning applications

Abstract

The energy demand in HVAC utilization has been steadily increasing, specifically in warm climate countries such as Iraq. Therefore, searching for advanced air conditioning systems driven by waste energy sources such as adsorption air conditioning systems operated by solar energy becomes necessary. The objective of the present study is to investigate the performance of the adsorption thermophysical battery (ATB) employed with the silica gel-water under various operating conditions. In addition, examine and analyses the influence of outlet chilled temperature and pressure during the charge and discharge processes. The performance parameters of ATB including, cooling capacity (CC), coefficient of performance (COP), specific cooling power (SCP) under different effective temperatures are evaluated. The lumped parameter method (LPM) and modified Freundlich adsorption equations are used to develop a theoretical approach. The results revealed that, relatively low temperature range (50–70 °C) can be used during the charging process based on a common waste heat source. A significant reduction in the temperature and pressure of ECU during the charging-condensation process can be achieved by decreasing the inlet coolant temperature to the chilled temperature. This relatively low temperature is close to the chilled water temperature which can be used for air conditioning purposes. Investigating three inlet chilled temperatures 15 °C, 20 °C, and 30 °C showed that the increase in the chilled temperatures enhanced the evaporation process and increased COP, SCP, CC and the adsorption uptake. The reduction in the inlet coolant temperature from 40 to 20 °C, resulted in 11% enhancement in CC. The determined performance parameters of the ATB system under specified operating conditions are 2 kW, 0.3 and 100 Wkg−1 for CC, COP, and SCP respectively.