AN ANALYSIS OF THE PERFORMANCE OF AN EXTERIOR AIR - DOMESTIC WATER HEAT PUMP - REGULATION AND INTRINSIC PERFORMANCE
The objective of this project is to identify possible improvements for an electrical compressor heat pump of around 12 kW with air as a heat source. To test the heat pump under different "weather" conditions a test loop has been built which delivers air at the evaporator, at a required temperature and humidity (5 000 Nm**3/hr, - 15 to 20 degrees C and 10 to 100% relative humidity). On the condensor side a water circuit with several capacities and heat exchangers simulates the thermal behaviour of a 120 m**2 dwelling. The major part of the first phase was devoted to the construction of the test loop. Subsequently a commercial domestic heat pump was extensively tested. The instantaneous performance of the heat pump agreed well with the data claimed by the manufacturer. The annual energy saving however was significantly lower due to the following: + loss of efficiency caused by defrosting cycles; + loss of efficiency due to inadequate thermal load matching between the heat pump and the house. It was shown that control of the condensing temperature, instead of a conventional control of the room temperature can bring energy savings of 10%. This could probably also be realized by load matching with a compressor with a variable speed; the heat output range with such a compressor however is limited; + the inefficient operation of components such as the evaporator and the condensor heat exchangers and the expansion valve (bad regulation caused a too high super heating temperature). Optimization could lead to a considerable improvement. Modifications in the compressor are proposed which may lead to an increase of the efficiency from the present 40-60% to 60-70%. Decrease of heat pump performance due to compressor oil dissolving in the refrigerant can be neglected for the hermetic piston compressor.
Bibliographic Reference: EUR 10523 FR (1986) MF, 140 P., BFR 300, BLOW-UP COPY BFR 700, EUROFFICE, LUXEMBOURG, POB 1003
Availability: Can be ordered online
Record Number: 1989125036300 / Last updated on: 1987-04-01
Available languages: fr