Feasibility of driving convective thermal wave chillers with low-grade heat

Abstract

A theoretical investigation of a convective thermal wave adsorption chiller was completed. The working pair was activated carbon–methanol. The predicted axial profiles of loading and temperature exhibited the same features as those reported for ammonia-activated carbon beds. For practical purposes, the coefficient of performance (COP) and a dimensionless cooling power were insensitive to the heat capacity of the refrigerant vapour, or the effective thermal conductivity of the refrigerant. With regard to the bed, increasing either its effective heat capacity or its effective axial conductivity strongly impeded performance. The COP and the dimensionless cooling power were mapped against two composite dimensionless groups, formed from a Stanton number, a ratio of interphase heat transfer to axial conduction, and the group aL where a is surface area per unit volume and L is bed length. Realistic pumping power was possible only at the expense of relatively large machines and poor COP; the two attributes that the convective thermal wave machines are intended to enhance. The results discouraged the building of costly experiments.