Critical review of heat pump prototype operation and required modications

TRI-HP EU project is aiming to develop trigeneration integrated solutions that combine heating, cooling and electricity generation, based on heat pumps running with natural refrigerants and using multiple renewable energy sources. This deliverable presents the experimental performance evaluations of the R744-ice heat pump, R290-ice heat pump, and R290-dual source heat pump. The R744-ice heat pump includes a rotary compressor coupled to an inverter, the tri-partite brazed plate gas cooler, an evaporator, an internal heat exchanger, an ejector, a throttling valve, and a liquid separator. The heat pump unit is designed with a capacity of 10 kW, 8 kW, and 10 kW under only domestic hot water, only space heating, and simultaneous domestic hot water and space heating modes to provide the tap water heating and space heating water up to 70 °C and 35 °C, respectively. The rst R290-ice heat pump prototype is designed with a capacity of 10 kW and consists of a scroll compressor with inverter, two plate heat exchangers in the heat sink side (desuperheater and condenser), an evaporator, an internal heat exchanger, and several expansion valves. A 10 kW R290-dual source heat pump is designed and manufactured to use both air and/or brine coming from geothermal boreholes as heat source/sink, allowing to test this unit under heating and cooling working modes. The R744-ice heat pump and R290-ice heat pump are studied at a steady state for only space heating operation, only domestic hot water operation, and simultaneous domestic hot water and space heating operation. The R290- dual source heat pump is investigated under heating and cooling conditions applying air and/or water as the heat source/sink. The effects of different operating parameters on the overall coefcient of performance, heat duty, and compressor energy consumption are analyzed in detail. The experimental results of the tested heat pumps show promising performances. The COP of R290-ice heat pump for space heating temperature 30/35 °C ranges between 4.4 and 5.4. However, the COP of the unit for domestic hot water with a set temperature of 65 °C drops to between 2.5 and 2.8. This is where the CO2-ice heat pump shows good results for high domestic hot water demand. In domestic hot water mode, the COP varies between 3.6 and 4.3 for set temperatures of 55 °C to 65 °C. The delivered heating capacity of the R290-dual source heat pump is slightly lower than the requirements under the design conditions. The coefcient of