A Simulation Model for CO2 Solar-Assisted Heat Pumps

Heat pumps are a widely spread kind of thermal system used to provide heating. This kind of system has to be adapted to the new requirements related to environmental impacts of its working fluids. Several countries already restricted the use of non-environmental friendly fluids and established deadlines for the end of their use. Carbon dioxide is a suitable option since it is a natural substance, with very low greenhouse impact and null ozone depletion potential. Considering this scenario, a steady state simulation model was developed and a parametrical analysis is presented for a solar-assisted heat pump with carbon dioxide as working fluid on a transcritical compression cycle. In the high pressure side a gas cooler working as a counterflow heat exchanger provides hot water for residential use. In the low pressure side, a flat-plate solar collector improves heat input for the system enabling a more compact design. Simulation results are presented as a function of some working parameters that demonstrate the feasibility of the system for the intended application.