Brief Project Description and Progress
The EXP-HEAT goal is to improve the performance of heat pump units, by integrating a new hydraulic piston type expander and optimizing its design and combined operation at a wide operation range. Apart from the developed expander that is expected to be commercialized after the project end, two new products are planned to be developed: a new heat pump featuring the new expander and a retrofit kit for retrofitting already installed heat pumps with the expander machine. In the first year, according to the schedule of the project, a prototype expander has been designed by ITAL (Italgroup SRL), DORIN (Officine Mario Dorin SPA) and FIR (Universita degli Studi di Firenze) starting from an ITAL motor (Italgroup G100), and manufactured by ITAL. The manufactured expander was then tested at the test-rig developed by DORIN and FIR at the premises of DORIN. These first tests with R314a and CO2 served to measure the performance of the expander and to solve the major technical issues. The efficiency of the first version of the expander was poor, reaching isentropic efficiencies in the range between 8-10% according to the inlet quality of the refrigerant. The project was then suspended for 10 months. During this period, a dedicated campaign to identify the different inefficiency sources (mainly internal leakages and friction losses) and define the best available lubrication options was run by DORIN, ITAL and FIR and further modifications were designed to be implemented to the expander in order to solve these issues. In parallel, EURE (EUREFTEC AB) and KTH (Kungliga Tekniska Hoegskolan) conducted a thorough market analysis of heat pumps to showcase the potential for the developed expander and THERMO (Thermogas SA) and NTUA (National Technical University of Athens) focused on the use of the expander’s mechanical power and on specific retrofitting issues. The project suspension was then lifted and the new optimized expander was modified accordingly and a second test campaign was run with R404a and R410a in the premises of DORIN reaching a maximum shaft isentropic efficiency of 26%. This value has been extrapolated to more favourable conditions reaching the threshold value of 30%. Two prototypes of the latest version of the expander are currently undergoing testing in two dedicated test rigs: in a new heat pump system in the laboratory of KTH and in a retrofitted commercial heat pump in the laboratory of NTUA according to the project schedule.