Basic Principles for Substantiation of Working Pair Choice

Abstract

The chapter is devoted to basic principles for substantiation of working pair choice. Principles for substantiation for selection of adsorbate and adsorbent are considered. The main requirements to adsorbate are formulated as follows: low cost, easy of obtaining, small molecular size to facilitate the adsorption effect; high latent heat of evaporation and small volume in liquid state; high thermal conductivity; low viscosity, thermal stability with adsorbent in the operating temperature range; chemical stability in the working temperature range; non-toxicity for animals and human, non-aggressiveness and incombustibility; low pressure saturation (slightly above atmospheric pressure) at normal operating temperature; the absence of environmental problems. Water is shown to conform to these requirements. The crucial requirements to adsorbent are the ability to adsorb large amounts of adsorbate when cooled to environment temperature and give a high cooling effect; high values of maximal adsorption; desorption of the major portion of adsorbate (ideally all) when heated by an accessible source of heat; low heat capacity; good heat conductivity, short cycle time; no deterioration and loss of adsorption capacity over time or use; non-toxicity, non-aggressiveness; chemical physical compatibility with the selected adsorbate; low cost and wide availability. Properties of various types of adsorbents were compared. Composites ‘salt inside porous matrix' are shown to be promising media for heat storage and transformation. Characteristics of thermodynamic cycles of heat conversion were analysed. The ways to improve the coefficient of performance were analysed and shown to be affected by a proper choice of an adsorbent.