22 May 2008

EFFECTS OF ELECTRONIC EXPANSION VALVES ON HEAT PUMP PERFORMANCE


The use of electronic expansion valves in heat pumps allows a preciser run of the
superheat of the refrigerant. Enhanced new products for this purpose are now available. With
them, the designer can define the cycle continuously (stepless) compared with today’s
compromise using fix adjusted thermostatic expansion valves. Over the whole range of
application the delivered capacity is piloted. Of special interest are situations as for example
air/water heat pump with air inlet temperatures above + 15 °C. The control of the electronic
component is to integrate in the heat pump control procedure in order to guarantee an
optimized run of the whole heat pump system with all its changing data. The paper shall
present the latest developments and first test results, how and how far COP’s and especially
SPF (seasonal performance factor) can be improved by the use of electronic expansion
valve. The research shall also reduce the application cost of the electronic expansion valves
in order to allow the wide application also in small heat pumps.