A theoretical and experimental study of HFE-7000 in a small scale solar organic Rankine cycle as a thermofluid.

Abstract

The use of thermofluids with boiling temperatures lower than the water, allows the operation of low and medium temperature solar thermal systems on an Organic Rankine Cycle (ORC) to generate both mechanical and heat energy. At the same time, the selection of appropriate thermofluid is an important process and has a significant effect both on the system performance and the environment. Conventional thermofluids such as Chlorofluorocarbons (CFCs) and Hydrochlorofluorocarbons (HCFCs) have high ozone depletion (ODP) and high global warming (GWP) potential. It is therefore important to investigate novel and environmentally friendly thermofluids to address environmental impacts as global warming and ozone layer depletion. Hydrofluoroethers (HFEs) have zero ODP and relatively low GWP and therefore can be used as a replacement for CFCs and HCFCs. In this study, a small scale solar ORC is designed and commissioned to use HFE 7000 as a thermofluids. The system has a flat plate collector and a vane expander as the heat source and prime mover of the cycle respectively. The system performance is determined through energy analysis. Then, a mathematical model of the cycle is developed and the effect of various operating conditions on the components, as well as the whole cycle is examined through performing simulation analyses. Both the experimental and theoretical research indicates that HFE 7000 offers a viable alternative to be used efficiently in small scale solar ORCs to generate mechanical and heat energy.