Measurement of thermodynamic properties of ammoniated salts and thermodynamic simulation of resorption cooling system

The adsorption and desorption pressure-concentration isotherms (PCIs) of ammonia on NaBr and MnCl₂ salts are measured at different temperatures. Significant hysteresis is observed between adsorption and desorption PCIs. From PCI data, van't Hoff plots are constructed to estimate the enthalpies of formation for different ammonia concentrations. Substantial variation in reaction enthalpy during adsorption and desorption is noticed from beginning to the end of the processes. The average values of ΔH for NaBr and MnCl₂ are -28.59 kJ mol^-1 and -60.17 kJ mol^-1 respectively for adsorption and 29.16 kJ mol^-1 and 65.62 kJ mol^-1 respectively for desorption. The resorption cooling system is thermodynamically analyzed using measured equilibrium data. The coefficient of performance (COP) and specific cooling power (SCP) of resorption system is evaluated to be 0.31 and 52 W kg^-1 at refrigeration, regeneration and ambient temperatures of -15 °C, 170 °C and 25 °C respectively at a mass ratio of 4. About 49.18% decrease in COP is noticed in comparison with maximum theoretical COP in which 32.78% and 16.36% reductions are due to hysteresis effect and thermal capacity of metallic mass respectively.