Performance evaluation of simple and heat recovery adsorption cooling system using measured NH3 sorption characteristics of halide salts

The ammonia adsorption/desorption pressure-concentration isotherms (PCIs) of CaCl2, SrCl2, MnCl2 and FeCl2 are measured. Based on the desorption temperature of chosen salts, they are grouped as medium temperature salt (70-100 °C) and high temperature salt (>100 °C). Hysteresis between adsorption and desorption is observed due to dimensional instability during adsorption and desorption. The adsorption capacity of halide salts are assessed at various temperatures. The average values of adsorption/desorption enthalpies of CaCl2, SrCl2, MnCl2 and FeCl2 are evaluated as 44.01/56.59, 54.32/66.60, 60.17/65.62 and 66.87/92.99 kJ mol−1, respectively. The measured PCIs and evaluated thermodynamic properties are used to analyze the performance of simple and heat recovery adsorption cooling system based on the gas-solid pair of ammonia as refrigerant and CaCl2, SrCl2, MnCl2 and FeCl2 as respective adsorbent. The theoretical coefficient of performance (COP) is estimated as 0.35, 0.31, 0.27 and 0.19 for CaCl2, SrCl2, MnCl2 and FeCl2 based simple adsorption cooling system, respectively. The reduction in maximum theoretical coefficient of performance (COPmax) due to hysteresis is in the order of CaCl2 < MnCl2 < SrCl2 < FeCl2 while COPmax reduces in the order of SrCl2 < CaCl2 < MnCl2 < FeCl2 due to sensible mass of reactor. The HTS and MTS based simple adsorption systems are combined to develop heat recovery adsorption cooling system in which two cooling effects are obtained for single heat input using heat recovery between HTS and MTS. The value of coefficient of performance is increased to 0.60 for the combination of MnCl2-CaCl2-NH3.