Energy efficiency comparison of heat pumping systems using R744 and R410A as refrigerant.

This work compares the cooling energy performance of various heat pumping systems using R410A and R744 as refrigerant. Focus is the energy efficiency of R744 hybrid ground-coupled heat pumping system. These hybrid systems thus use both ambient air and ground soil as heat sinks in the cooling mode. It is important to eliminate the underground thermal accumulation phenomenon in warm climates. Several dynamic models of heat pumping systems, using R410A and R744 as refrigerant, have been developed. They all use similar components with similar capacities and the same boundary conditions for a fair energy efficiency comparison. Simulation results show that the seasonal COPc of an R744 hybrid system reaches 3.55, which is around 42% better than for a R744 ASHP and 23% better than for a R744 GCHP system. The annual cooling performance factor of a commercial R410A ASHP system is better than for a R744 hybrid system, but the COPc for the R410A system will seriously decreased when the ambient temperature is higher than 30°C. R744 system can make great use integrating two heat sinks, as the system has a large temperature glide in the transcritical gas cooling process.