According to a new study, heat pumps are not so efficient in extremely cold climates, only being suited for moderate climates. These provide cooling in summer and heating in winter. Researchers at Purdue University have recently developed a new type of heat pump that allows residents in cold climates to halve their heating bills, due to its high efficiency.
For moderate climates, this device aims to improve the overall efficiency. Unlike other heating technologies used in cold regions, these new heat pumps might cost 50% less. In such regions, natural gas is unavailable and residents rely on liquid propane and electric heaters.
“We’ll be able to extend the geographical range where heat pumps can apply. So this could open up a whole new market.” said W. Travis Horton, an assistant professor of civil engineering.
The vapor-compression cycle of typical heat pumps has four stages: 1) refrigerant is compressed as a vapor, 2) condenses into a liquid, 3) expands to a mixture of liquid and vapor 4) then evaporates. The new technology works by modifying the conventional vapor-compression cycle behind standard air conditioning and refrigeration.
During the compression process, the research team is working to investigate two cooling approaches. These could reduce the energy losses due to friction in the expansion stage and also improve the compression process. In the first approach, large quantities of oil are introduced into the compressor to absorb heat produced throughout the compression stage. Next, in the second approach, a mixture of vapor refrigerant and liquid from the expansion stage is injected at various points during compression to provide cooling.
The researchers are planning to create a system for precisely controlling the flow of refrigerant from the evaporation stage into the compression stage using a series of small valves. Conventional heat pumps typically use reciprocating compressors and in this case a piston compresses refrigerant. But the new heat pump will be composed from a “scroll compressor,” which uses a rotating, scroll-shaped mechanism to compress refrigerant.
Researchers expect the release of a prototype by the end of 2012. To finish this $1.3 million project, the company collaborated with Emerson Climate Technologies Inc. and Carrier Corp. Emerson will work with three doctoral students to create the prototype heat pump and Carrier will integrate the new heat pump into a complete system. “With this technology we can maintain the efficiency of the heat pump even when it gets pretty cold outside,” stated Groll.