PDF Publication Title:
Text from PDF Page: 274
Appendix A – CO2 as a Working Fluid in Heat Pumps A1.3 Mass Flow Rate and Pressure Drop vs Dimensions of Pipelines and Components The mass flow rate in a heat pump system, which affects the required dimensions of components and piping, is inversely proportional to the specific enthalpy of evaporation of the working fluid. Since CO2 has a relatively large specific enthalpy of evaporation (Table A1), the required mass flow rate in a CO2 heat pump at 0oC evaporation temperature is about 5 to 15% lower than that of plants using HFCs. The moderate mass flow rate in combination with the steep saturation pressure curve (Section A1.6) leads to higher optimum flow velocities and smaller dimensions of components and pipelines than that of heat pump systems using HFC working fluids. This is also the case when comparing a CO2 system to a propane system, since the considerably steeper saturation pressure curve of CO2 is dominant to the roughly 60% lower mass flow rate in the propane system. A1.4 Required Compressor Volume The required compressor volume to produce a certain refrigerating or heating capacity is roughly inversely proportional to the suction pressure (Lorentzen and Pettersen, 1993). Due to the very high vapour density of CO2, the volumetric refrigerating capacity VRC (Gosney, 1982) is con- siderably higher than that of propane and the HFCs. As an example, the required swept volume for a reciprocating CO2 compressor at 0oC suction gas temperature is in the order of 35 to 85% lower than that of com- pressors designed for propane and HFC working fluids. A1.5 Compressor Performance Compressors in CO2 heat pump systems will operate at high mean pres- sures with large pressure differentials, and the latter will typically range from 5 to 10 MPa. However, the pressure ratio, which heavily affects the volumetric and energy efficiencies of the compressor, will be lower than that of conventional working fluids. Table A2 shows, as an example, typical pressure ratios for CO2, propane and selected HFCs at -10 and 0oC evaporation temperature and 35 and 50oC condensation temperature. The high-side pressures for the CO2 system are 9 and 11 MPa (RnLib, 2003). A4PDF Image | Residential CO2 Heat Pump System for Combined
PDF Search Title:
Residential CO2 Heat Pump System for CombinedOriginal File Name Searched:
20559406.pdfDIY PDF Search: Google It | Yahoo | Bing
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
| CONTACT TEL: 608-238-6001 Email: greg@infinityturbine.com | RSS | AMP |