Thermodynamic Analysis of Working Fluids for a New "Heat from Cold" Cycle

Adsorptive Heat Transformation systems are at the interface between thermal and chemical engineering. Their study and development need a thorough thermodynamic analysis aimed at the smart choice of adsorbent-adsorptive pair and its fitting with a particular heat transformation cycle. This paper addresses such an analysis for a new "Heat from Cold" cycle proposed for amplification of the ambient heat in cold countries. A comparison of four working fluids is made in terms of the useful heat per cycle and the temperature lift. The useful heat increases in the row water > ammonia ≥ methanol > hydrofluorocarbon R32. A threshold mass of exchanged adsorbate, below which the useful heat equals zero, raises in the same sequence. The most promising adsorbents for this cycle are activated carbons Maxsorb III and SRD 1352/2. For all the adsorptives studied, a linear relationship F = A·ΔT is found between the Dubinin adsorption potential and the driving temperature difference ΔT between the two natural thermal baths. It allows the maximum temperature lift during the heat generation stage to be assessed. Thus, a larger ΔT-value promotes the removal of the more strongly bound adsorbate.