Concept design of a thermo-chemical heat pump using calcium chloride-NH₃ and magnesium chloride-NH₃ working pairs

This work presents the design of a double effect thermochemical heat pump based on the calcium chloride-ammonia and magnesium chloride-ammonia working pairs. The work began with a comprehensive theoretical and literature review of the similar systems which exist in the literature. Once the literature review was done, a large temperature jump experimental rig was built in order to be able to determine the behaviour of the relevant working pairs. Even though the focus of the work is thermochemical reactions, the activated carbon-ammonia pair was first used to validate the large temperature jump rig. The reason for this is that the activated carbon-ammonia pair is better understood compare to the thermochemical reactions. The experiments on the activated carbon- ammonia pair yielded some useful results. The results obtained show that two heat transfer properties (thermal conductivity, k and heat transfer coefficient, h) with physical meaning can be extracted from large temperature jump data. Furthermore, the change in thermal conductivity with the packing density of the adsorbent was investigated. The general trend was one of increasing thermal conductivity as the packing density was increased, the thermal conductivity increased from 0.2Wm‾¹K‾¹ to 0.4Wm‾¹K‾¹ as the packing density was increased from 530kgm‾³ to 705kgm‾³. When the calcium chloride-ammonia and magnesium chloride-ammonia working pairs were investigated in the large temperature jump setup, the kinetic parameters for each respective reaction were obtained. This enabled the development of a dynamic model of a representative thermochemical heat pump based on the aforementioned working pairs. The dynamic model helped to investigate the performance of the heat pump under various operating conditions. The coefficient of performance (COP) and the specific heating power ranged from 1.21 to 1.40 and 40W/litre to 400W/litre respectively depending on the operating conditions