Vapor compression heat pumps are still the most reliable heatingand cooling systems for thermal management of spacecraft. However, system efficiency and adequate capacity are essential totheir proper functioning. Current heat pump systems have fivemajor components: compressor, evaporator, condenser, reversing4-way valves, and accumulator. The energy efficiency andcapacity of the conventional heat pump could be further improvedby incorporating more advanced design features, such as liquidover-feeding and passive charging optimization technology.Liquid over-feeding was developed by the Oak Ridge NationalLaboratory and was extensively tested on off-the-shelf airconditioners. The test results showed a 12% improvement incooling capacity and 7.5% increase in system coefficient ofperformance. Passive charging optimization technology (patentpending at ORNL) would further improve the performance of theadvanced heat pump at off-design conditions. The objectives ofthis research are the development of a computer model foradvanced heat pumps to be used in spacecraft, and development of a prototype advanced heat pump unit. Potential Commercial Application(s): A successful Phase I effort will lead to commercializationopportunities because liquid over-feeding and refrigerantinventory control could be implemented as hardware onconventional air conditioning systems. Some companies arealready interested in the liquid over-feeding technology. Refrigerant inventory control to ensure the optimum amount ofrefrigerant charge will be attractive to makers of airconditioning systems for commercial buildings because suchsystems operate most of the time at off-design conditions.
