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7 – Discussion and Analysis The calculated evaporation and condensation temperature was -5oC and 35.5oC, respectively, whereas the isentropic efficiency of the compressor was about 0.67. The latter was approximately 12 to 14 percentage points higher than the estimated efficiency of the prototype CO2 compressor. The simulation model described in Section 6.1, Modelling of CO2 Heat Pumps Using a Tripartite Gas Cooler, was used to calculate the COP of the prototype CO2 heat pump unit when the isentropic efficiency was increased by 5 percentage points, and the heat loss from the compressor was reduced to 10%. The simulation results are presented in Table 7.2. Table 7.2 The estimated COP of the prototype CO2 heat pump unit at 5% percentage points higher isentropic efficiency and 10% relative heat loss from the compressor. Mode – Temperature Program Measured Calculated COP New COP Relative Difference Combined mode DHW mode SH mode 35/30-60oC 60oC 35/30oC 3.89 4.35 | 3.80 4.24 12% 3.01 3.37 | The higher isentropic efficiency reduced the power input to the com- pressor, whereas the lower heat loss from the compressor shell resulted in a higher CO2 inlet temperature for the tripartite gas cooler. All in all the improved compressor performance led to approximately 12% higher COP for the integrated CO2 heat pump in all operating modes. The exergy analysis and the computer simulations clearly demonstrated that it is of particular importance for an integrated CO2 heat pump unit to apply a high-efficiency compressor. 7.2.4.2 The Tripartite Gas Cooler During operation in the combined mode, the relative exergy losses for the tripartite gas cooler was as low as 12 to 14%, and increased heat transfer surfaces would only had a minor impact on the losses. This was also the case during operation in the DHW and SH mode, due to the low temperature approaches. Consequently, under the prevailing operating conditions, the tripartite gas cooler was a component with minimal poten- tial for efficiency improvements. 222PDF 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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