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Energies 2021, 14, 8238 22 of 25 Table 11. Mean value of high pressure, evaporation pressure, water mass flow rate at the gas-cooler, gas-cooler heat flow rate, and COP during the simulation time. Time [h] 0–2.5 2.8–3.7 3.9–4.9 6.9–8.1 8.1–9.3 9.3–11.9 11.9–13.1 13.1–15.3 15.3–16.4 16.4–19.2 19.2–20.2 20.2–23.0 23.0–24.0 5. Conclusions p [bar] p [bar] eva HP 35.1 94.4 30.5 105.0 34.1 94.6 33.7 95.0 31.0 105.0 35.2 95.1 31.7 105.0 35.0 95.5 31.5 105.0 35.2 94.6 31.0 105.0 35.0 94.4 30.5 105.0 mwater kgh 2627.2 2498.7 3080.8 3458.3 2612.0 3212.6 2598.3 3559.8 2538.4 2798.9 2441.4 2645.3 2497.7 −1 Hot Water Production SH DHW SH SH DHW SH DHW SH DHW SH DHW SH DHW COP [-] 91.5 3.16 168.4 3.40 107.3 3.06 120.5 3.00 176.0 3.43 111.9 3.12 175.1 3.50 124.0 3.07 171.1 3.49 97.5 3.16 164.5 3.46 92.2 3.15 168.3 3.31 Q [kW] gc This paper presented the numerical model of a CO2 unit, which can operate according to a chiller or heat pump configuration. The numerical model was developed with the software Simcenter AMESim v.17, and its results were compared against experimental data in both heat pump and chiller configuration. The heat pump configuration of the numerical model was validated in both steady- state and dynamic conditions. In the steady-state condition, the model was in accordance with the experimental data in operating points and gas-cooler heat flow rate. The model was also validated in dynamic conditions by suddenly shutting off one of the compressors; the model was able to correctly replicate the heat pump dynamic behaviour, with a maximum difference between the experimentally collected and predicted gas-cooler heat flow rate of 5.0%. The numerical model assessment against experimental data was also performed in chiller configuration. The validation process demonstrated inconsistent accuracy between the two tested conditions. Furthermore, as the chiller configuration was much more complex than the heat pump one, due to the use of a flooded evaporator and two-phase ejector, further investigation is needed to provide a robust validation under different operating conditions. Lastly, the numerical model was utilized to investigate the dynamic performance of the refrigerating system operating in heat pump configuration in a typical application where the gas-cooler was coupled with hot water tanks. The model demonstrated a higher COP when operating in DHW operations due to a higher value of gas-cooler heat flow rate. Future work will consider: • The validation of the numerical model of the system operating in chiller configuration in dynamic conditions and the development of a predictive model of the natural circulation evaporator; • An experimental campaign in order to increase the accuracy of the model in the prediction of the performance of the system. • The coupling of the system with a validated numerical model of water tanks, in order to correctly quantify the dynamic behaviour of the coupled system and discuss the optimal control strategy; • The prediction of the system performance in a yearly simulation. • The use of the numerical model in a theoretical study to increase the efficiency and optimize the system during operation in chiller and heat pump configuration.PDF Image | Dynamic Modelling and Validation of an Air-to-Water Reversible R744
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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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