Micro technology in heat pumping systems (Reprinted from 20th International Congress of Refrigeration, IIR/IIF, Sydney, yr 1999)

Micro heat pumps, with dimensions in the order of centimetres, may in the future be utilised for the heating and/or cooling of buildings, vehicles, clothing, and other products or applications. A number of issues have yet to be solved, including the construction of a microscale compressor, and determination of micro heat exchanger heat transfer capacities, Test samples of micro heat exchangers and a corresponding test apparatus have been built. Some two-phase experiments with propane (R-290) as refrigerant have been conducted. Preliminary results for a micro condenser with 0.5 mm. wide trapezoidal channels of 25 turn length showed that a heat flux of up to 135 kW/m(2), based on the refrigerant-side area, was attainable. The corresponding overall heat transfer coefficient was 10 kW/(m(2) K), with a refrigerant mass flux of 165 kg/(m(2) s) and a refrigerant-side pressure drop of 180 kPa/m. (C) 2002 Elsevier Science Ltd and IIR. All rights reserved.