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TEST RESULTS AND ANALYSIS Stage 1. It is well known that refrigeration cycles operating near the critical point have higher throttling losses than cycles with condensing temperatures much lower than the critical temperature. The throttling losses in a transcritical cycle can however be reduced if the temperature of the supercritical fluid before the throttling valve is considerably lower than the critical temperature. This is especially important to have in mind when working with CO2-cycles. Therefore, the working fluid temperature after the gas cooler outlet has a crucial influence on the performance of CO2 heat pumps. It is important to cool down the fluid temperature as low as possible. If a constant approaching temperature difference is assumed, it will become obvious that the system should operate with as low cooling water inlet temperature to the gas cooler as possible. Thanks to the modified connection of the water inlet from the tank to the heat pump, it is in the experiment possible to control the heat pump water inlet temperature by adjusting the cooling water flow rate to the plate heat exchanger (i.e. the one simulates the radiator system).The variation of heat pump unit COP for different water inlet temperatures were pre-tested at the beginning of the testing work to get a feeling on the water inlet temperature’s control scheme. The heat pump performance at different water inlet temperature to the gas cooler was tested at 7 °C outdoor temperature. These test results are shown in Figure 11. As the trend shows in the figure, the heat pump heating COP decrease with increasing water inlet temperatures. Besides that, one may also notice large deviations in the results. The reason for this is the dynamic behavior of the system, the different operating points were monitored during a relative short period of constant water inlet temperature (i.e. the system was not at a very stable condition, when those points were recorded). More results can also be found in appendix 1. 6 5.5 5 4.5 4 3.5 3 2.5 2 1.5 1 Figure 11. COP1 vs. Water inlet temperature to the gas cooler at 7 °C outdoor temperature 15 20 25 30 35 40 45 Water inlet temperature gas cooler 20 COP 1PDF Image | CO2 heat pumps for the Swedish market
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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
Heat Pumps CO2 ORC Heat Pump System Platform More Info
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