Performance investigation of high-temperature heat pumps with various BZT working fluids

In this paper we propose four kinds of high-temperature heat pumps with mechanical compression, working with various Bethe–Zel’dovich–Thompson (BZT) fluids, and study their performances for comparison purposes. A total of 17 molecularly complex fluids from the class of siloxanes and perfluorocarbons are selected as potential working fluids. The Martin–Hou, Peng–Robinson–Stryjek–Vera and Span–Wagner equations of state are used in the analysis. A parametric study is also conducted for a range of isentropic efficiency and temperatures at sink and source. The results of the energetic and exergetic coefficient of performances show that the heat pumps proposed in this study appear to be attractive for some applications with a temperature difference of about 50 °C, whenever heat and/or work recovery, or using a non-conventional energy source (renewable, waste heat, waste matter) or sustainable nuclear energy is possible. Examples of such applications may include providing heat to high-temperature endothermic reactions, thermo-chemical water splitting, physical processes (e.g., distillation), or industrial heat treatments. Among the fluids studied here, siloxanes show the best performance.