ANALYSIS OF CHEMICAL HEAT-PUMPS (CHPS) - BASIC CONCEPTS AND NUMERICAL-MODEL DESCRIPTION

Thermochemical phenomena occurring during the reaction between a gas a nd solid porous media (thermochemical materials) have been modelled. T he practical application envisaged is the use of these thermochemical materials in chemical heat pumps (CHP) to produce both heat and cold. In the synthesis part of the cycle, a gas (e.g. ammonia) at a moderate pressure reacts uniformly with the salt (e.g. MnCl2 . 2NH(3)) compone nt of a thermochemical material. Subsequently the ammoniated salt (MnC l2 . 6NH(3)) is decomposed to release the gas at an elevated pressure. A detailed numerical model is presented for the decomposition phase o f the CHP reaction cycle. The numerical simulation of a CHP reactor du ring a synthesis-decomposition reaction cycle has several specific req uirements. The phase change problem involving discontinuities in the t hermal properties of the two different salts at their reaction interfa ce needs special care for numerical solution. In this paper, the sourc e-based method which is a fixed grid enthalpy approach, was used. The solution of the partial differential equation was obtained, using a co ntrol volume approach around each spacial node. This thermal study exa mined configurations that had different reactor diameters, and other p arameters that influenced heat transfer. Typical results included conv ersions, power generated as a function of reactor diameter and time-on -stream, required heat exchange area, and heat losses. (C) 1997 Publis hed by Elsevier Science Ltd.