23 September 2011

DYNAMIC-LUMPED PARAMETER MODEL OF A HEAT PUMP – SENSITIVITY ANALYSIS FOR PERFORMANCE OPTIMIZATION


A heat pump dedicated to building heating must exhibit sufficient efficiency
(usually measured by the coefficient of performance) in order to comply with low energy
consumption and CO2 production. Good performance can be achieved through capacity
control. In this study, the authors evaluate the impact of the capacity adjustments on the
transient behaviour of the heat pump. A dynamic, lumped-parameter model is used, which is
composed of moving-boundary exchanger sub-models, static compressor and expansion
valve sub-models. It is shown, by examining the transfer function of the expansion valvesuperheating system, that changes in the compressor flow rates may influence seriously the
control of the superheating. Future developments should be devoted to further investigation
with respect to capacity control but also to model refinement and validation through
experience.