Experimental and numerical analysis of a CO2 solar-assisted heat pump with PV-T evaporators

The purpose of this thesis work is to study both experimentally and through a numerical model a prototype of a solar-assisted heat pump, working with CO2 as refrigerant. In particular, the prototype is a dual-source heat pump that can use as heat source the external air, by means of a finned coil heat exchanger and the solar radiation through three PV/T collectors. The focus will be on the simultaneous operation mode where the heat pump works with both evaporators at the same time. This thesis is divided into seven chapters. The first chapter presents an overview of the state of the art reached by the research sector, both on the different technologies used in this prototype and on the use of CO2 as a refrigerant. The following two chapters describe the main components of the prototype under examination, as well as the measuring instruments used, a description of the various operating modes of the heat pump and the procedure used for data collection. The fourth chapter shows the numerical data collected during the experimental campaign, used to analyze and compare the various operating modes. The fifth chapter instead describes and validates the numerical model used to simulate the behavior of the heat pump in all steady-state operating conditions. In addition, a deeper analysis of the optimization of the evaporator type mode to be used is performed, according to the operating condition. Regarding the validation, this was carried out under steady-state conditions, by comparing the results of the experimental campaign with those provided by the model. In chapter six the validation of the model, under dynamic conditions, and a further analysis of the dynamic operation of the different evaporator modes, under the same operating condition, is carried out. Finally, in the final chapter, a discussion about the state of the art regarding reversible heat pumps and a subsequent possible numerical solution that can be adopted to invert the heat pump in question is done.