Energy-saving method checks refrigerant level in air co...(. The technique also was described in a ...)

Another research project at Purdue is nearing completion and has involved a more extensive evaluation of the virtual charge sensor. The project, also funded through California's PIER program, has been led by graduate student Woohyun Kim.

Purdue has applied for a patent on the technique, developed in research based at the university's Ray W. Herrick Laboratories.

Li and Braun created a software algorithm that interprets temperature-sensor data to estimate the amount of refrigerant in the system. The four sensors are attached to tubing running into and out of components called heat exchangers.

In air conditioning and refrigeration systems, liquid refrigerant evaporates in a heat exchanger called an evaporator, cooling the air. The refrigerant vapor turns back into a liquid in another heat exchanger called a condenser. During these evaporation and condensing steps, the refrigerant undergoes dramatic temperature changes.

Automotive air conditioning units equipped with the new refrigerant-charge system could activate a warning light on a car's dashboard. Technicians servicing home air conditioners might simply plug a personal digital assistant into the unit to read the refrigerant-charge information, Braun said.

Researchers began developing the technique four years ago.

"The method could be commercialized if a company invested some time in the implementation side," Braun said.

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