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It can be observed that the HCs and the HFOs present lower discharge temperatures than R410A, whereas R152a and R32 entail a higher one, fact that confirms the observations of Ho-Saeng Leea (2012). R152a surpasses the baseline values from an outdoor temperature of -12 °C, and an increase up to 7.4% at the highest temperatures is detected. Concerning R32, it entails the highest discharge temperatures between the alternatives, with a maximum increase of 27.8% at the lowest temperatures of the evaluated range. It has to be noted that below -6 °C, R32 operates at temperature above the safety limit for the compressor, as also observed by Barve et al. (2010) As a consequence, careful consideration of materials and other substances must be taken. It can be pointed out that in this case the correlation for the compressor efficiency is not optimal for R32, as it was assumed to be the same obtained with R410A. The results could thus be improved with the better knowledge of the compressor’s performance with the specific refrigerant. 4.2. Volumetric heating capacity The results obtained for the volumetric heating capacity (VHC) can be seen in Figure 4.2 in the case of radiator heating, and in Figure 4.3 for the case of floor heating. The values of VHC are here obtained for an evaporation temperature of -8 °C, with a subcooling amount of 4 °C and superheat of 4.8 °C. 6000 5000 4000 3000 2000 1000 0 25 35 45 55 65 Condensation temperature [°C] R410A R32 R152a R290 R1270 R1234yf R1234ze(E) Figure 4.2. Volumetric heating capacity vs. condensation temperature (radiator heating) It can be noticed from the graph Figure 4.2 that all refrigerants imply a lower VHC when compared to R410A, except for R32. In average, R32 entails an increase in the VHC of 12.4%. As mentioned, the other options all involve lower VHCs. The HFOs own the biggest reduction, of averagely 59.9% and 68% for R1234yf and R1234ze(E) respectively. It can be noticed that propylene, presents a higher VHC than propane; propylene could thus in this case represent a better option between the two hydrocarbons. Concerning the HFOs, it can be observed that -34- VHC [kJ/m3]PDF Image | Next generation of refrigerants for residential heat pump systems
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