17 June 2005
Lower charge heat pump systems can reduce the direct contribution to global warming as measured by the Total Equivalent Warming Impact (TEWI) as well as to mitigate flammability risks associated with hydrocarbon (HC) refrigerants. The DOE/ORNL Heat Pump Model was used to optimize a residential heat pump with several working fluids (replacements to HCFC-22) and conventional fin-tube heat exchangers. The study found that the required charge for optimal heat pump designs with HCFC-22 replacements can be somewhat lower than for the baseline heat pump system. Microchannel heat exchangers have the potential for even more significant reductions that can significantly reduce the TEWI of HFCs and possibly make flammable refrigerants more acceptable in residential equipment.