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5 – Experimental Results The COP vs. the Evaporation Temperature Figure 5.32 shows the measured COP for the CO2 heat pump unit at varying evaporation temperature and 60oC hot water temperature. At -10oC evaporation temperature (2.649 MPa), the suction gas superheating was 2.2 K ±0.1 K, the CO2 mass flow rate was 1.21 kg/min ±2% and the inlet city water temperature was 6.9oC. The test at 0°C evaporation temperature had to be cancelled due to operational problems with the test rig. 4.0 3.5 3.0 2.5 8.0 8.5 9.0 9.5 10.0 Gas Cooler Pressure [MPa] 3.80 3.27 3.25 -5°C -10°C Figure 5.32 The measured COP in the DHW mode at varying evapo- ration temperature and 60oC DHW temperature. Since the COP at -10oC evaporation temperature was virtually identical at 8.5 and 9 MPa high-side pressure, the optimum high-side pressure was probably located between 8.5 and 9 MPa, and the maximum COP was therefore higher than 3.27. Hence, assuming a maximum COP of 3.4, the COP decreased by approx. 10% when the evaporation temperature was altered from -5 to -10oC. This is about 4 percentage points more than that of the combined mode, which indicates that the COP was more sensitive to variations in the evaporation temperature in the DHW mode. The Heating Capacity of the Gas Cooler Units The total heating capacity at optimum high-side pressure and 60 and 70oC hot water temperature was 7.1 to 7.5 kW, respectively. This was about 5% higher than that of the total average heating capacity in the combined mode. The difference was mainly a result of the higher optimum high-side pressure and the lower average temperature approach. 138 COP [-]PDF Image | Residential CO2 Heat Pump System for Combined
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CO2 Organic Rankine Cycle Experimenter Platform The supercritical CO2 phase change system is both a heat pump and organic rankine cycle which can be used for those purposes and as a supercritical extractor for advanced subcritical and supercritical extraction technology. Uses include producing nanoparticles, precious metal CO2 extraction, lithium battery recycling, and other applications... More Info
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