Purdue University’s Research on Heat Pump Design Promises More Efficiency

Purdue University researchers are developing a new heat pump design that promises better efficiency in very low temperatures and can be used effectively across a wider geographic range. If the end result of the project meets all projected expectations, then it could drastically cut down heating bills of people living in cold climates.

US Department of Energy is funding the project, with a grant of up to $1.3 million. It is hoped that a concept/prototype pump design will be ready after the research span of three years. Others working on the project with Purdue include Carrier Corp and Emerson Climate Technologies Inc. Emerson is involved with the research side, while Carrier has taken the responsibility of integrating the design into a complete heat pump system.

The research aims to make changes in heat pump operation for better performance in very low temperatures. Two cooling processes involved in heat pump compression are being studied by researchers. In one process, moderately large quantities of oil are being added to the compressor to absorb all the heat produced during compression. In the second process, a vapor and liquid mix refrigerant is being injected at different times during the compression process to facilitate cooling. The injection of oil and refrigerants is not possible in a traditional reciprocating compressor design. Researchers had to redesign the scroll compressor to allow the addition of these substances into the compressor chamber.

Eckhard Groll is a mechanical engineering professor working on the project. According to him, a design modification was necessary as the reciprocating compressor could not accept liquids. The new scroll compressor is unique – in this, the liquids can be easily pumped, something that was needed for the purpose of the study. He said that it is important to evaluate the level of efficiency of a system that can pump liquid as well as compress gas and a significant amount of computational modeling will be involved.

Groll added that heat pump efficiency can be maintained with this technology, even if temperatures outside drop to low levels. Others assisting on the project include assistant professor of civil engineering W.Travis. Horton. The new technology that will be developed at the end of the research will work by altering the existing vapor compression cycle used by typical refrigeration and air conditioning systems. There are four stages in the process: the refrigerant is compressed into a vapor which condenses to form a liquid. This is further expanded into a mixture of liquid and vapor and ultimately evaporated.

The process of injecting the refrigerant into the scroll compressor will be carefully controlled by a set of valves that are being developed as a part of the project. An ongoing research on the Ericsson cycle will be used for this purpose. Purdue University is researching something similar in a joint study with the California Energy Commission.

Doctoral students participating in the research are Ian Bell and Margaret Mathison. Their research papers will be presented at the 13^th International Refrigeration and Air Conditioning Conference.

Watch our video on
ClearView's guarantee