Experimental evaluation of the heat output/input and coefficient of performance characteristics of a chemical heat pump in the heat upgrading cycle of CaCl₂ hydration

We herein evaluate the use of a chemical heat pump (CHP) for upgrading waste heat produced during the hydration of CaCl₂. The reactor module employed was an aluminum plate-tube heat exchanger bearing corrugated fins, a porous Ni plate, and the CaCl₂ sample in the form of a packed bed. The volumetric heat output and input characteristics of the reactor module were evaluated experimentally, the coefficient of performance (COP) was calculated for the heat upgrading cycle, and the hourly heat output for the system was determined. We found that the obtained waste heat could be upgraded from 100 to 155 °C, and the maximum volumetric heat output and input obtained were 380 and −280 kW·m⁻³, respectively. It was therefore apparent that a high performance reactor module could be obtained by reducing the heat and mass transfer resistances in the packed bed. In addition, using this reactor model, a coefficient of performance (COP) value of 0.48 was achieved for the heat upgrading cycle. Furthermore, upon switching the step time of the heat release and storage steps, an hourly heat output of 72 kW h·m⁻³ was achieved with a reaction fraction of 0.8. Our results therefore demonstrate that the use of our CHP system for upgrading waste heat would be expected to improve the energy efficiencies of industrial processes.