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Appendix D – Uncertainty Analysis The uncertainty in the temperature and pressure measurements was ±32 kPa and ±0.5°C, respectively, whereas the uncertainty in the CO2 mass flow rate was 0.3% of the measured value when assuming pure CO2. However, due to the fact that the measured mass flow rate was a mixture of roughly 91 to 93% CO2 and 6 to 9% lubricant, the uncertainty was set at 2% in the calculations. Table D3 shows the absolute and relative uncertainty in the total heating capacity of the CO2 heat pump unit during operation in the three different operating modes, when the compressor was running at 6000 rpm (m& ≈1.45 kg/min), the set-point for the hot water temperature was 70°C, and the supply and return temperatures in the space heating system were 35/30°C. Table D3 The absolute and relative uncertainty in the total heating capacity for the CO2 heat pump unit at different operating modes and gas cooler (high/side) pressures. The calculations are based on measurements from the CO2 circuit. Heating Mode GC Pressure δQ [W] αQ [%] SH=Space heating mode SH DHW SH + DHW D4 Uncertainty in the COP 8 MPa ±115 ±2.2 9 MPa ±110 ±2.0 9 MPa ±115 ±2.4 10 MPa ±160 ±2.0 8 MPa ±115 ±1.9 9 MPa ±130 ±1.9 DHW=hot water heating mode SH+DHW=combined mode The Coefficient of Performance (COP) of a heat pump unit is defined as: (D10) COP = QP where Q& is the total heating capacity of the gas cooler(s) [W] and P is the power consumption of the compressor [W]. According to Eq. D2, the absolute uncertainty for the total heating capacity is: (D11) & ⎡&2⎛& ⎞2⎤0.5 ⎢⎛δQ⎞⎜Q ⎟⎥ δCOP=⎢⎜P⎟ +⎜−P2 ⋅δP⎟⎥ D4 ⎣⎝⎠⎝ ⎠⎦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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