Abstract
The coupling of reversible ammoniation reactions between two salts presents a method for the exploitation of low grade waste heat. This resorption configuration can be used for thermal transformation or heat pumping, to recover waste heat to primary producers, or for integration in heat networks. To understand the solid/gas reaction behaviour and to model its kinetics, Large Temperature Jump (LTJ) experiments were performed on a composite of barium chloride in an expanded natural graphite (ENG) matrix. A model has been built using a semi-empirical equation from the literature, which has been validated with the LTJ results. The results suggest the semi-empirical model provides a reasonable prediction for solid/gas reactions once the constants have been identified. Enhancing the model to handle sequential phase change reactions will enable a wide number of salts to be modelled, making the design of a resorption system practicable.
Highlights
Halide salts reacting with ammonia are an attractive prospect for the purpose of heat pumping and transforming
An Large Temperature Jump (LTJ) test piece comprised of a typical section of heat exchanger containing a small sample of adsorbent will emulate the performance of a working resorption bed or adsorption generator
If an equal pressure rise in a small timestep is assumed for all the elements, knowing the quantity of heat flow in or out of each, plus the assumed kinetic equation allows the change in temperature and mass of adsorbed or desorbed ammonia to be calculated
Summary
Halide salts reacting with ammonia are an attractive prospect for the purpose of heat pumping and transforming. Future physical adsorption systems (e.g., carbon-ammonia or zeolite-water) may become more affordable, but chemisorption systems (e.g., resorption with ammonia—metal halides) produce more heat per kg adsorbed refrigerant and have potentially higher Coefficient of Performance (COP). The change in temperature of the heat exchanger in thermal contact with the adsorbent bed initiates the adsorption and desorption reactions [3]. An LTJ test piece comprised of a typical section of heat exchanger containing a small sample of adsorbent will emulate the performance of a working resorption bed or adsorption generator. Future physical adsorption systems (e.g., carbon-ammonia or zeolite-water) may become more affordable, but chemisorption systems (e.g., resorption with ammonia—metal halides) produce more heat per kg adsorbed refrigerant and have.
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