Reversing air-source heat pumps - Noise at defrost initiation and a noise reducing strategy
Journal article, 2016

With the increasing use of air source heat pumps, noise disturbance can be a barrier for further market growth and acceptance. Both steady state noise level and noise events influence reported noise disturbance. In this study one of the transient noise events was investigated: the noise initiated when the heat pump shifts to defrost mode. The results show that noise from a heat pump at defrost initiation was strongly dependent on the pressure differences in the system at the time of the shift. A reduced pressure difference resulted in a lower noise level. A control strategy that adds an idling time for the heat pump just before the shift of the 4-way valve is therefore suggested. This will have a small negative effect (<3%) on the heat capacity of the heat pump but the effect upon the COP will be negligible. (C) 2016 Elsevier Ltd and International Institute of Refrigeration. All rights reserved.



4-way valve


Pressure differences


Heat pump



Noise reduction


O. Gustafsson

SP Sveriges Tekniska Forskningsinstitut AB

C. Teuillieres

Electricite de France (EDF)

H. Hellgren

SP Sveriges Tekniska Forskningsinstitut AB

Monica Axell

SP Sveriges Tekniska Forskningsinstitut AB

Jan-Olof Dalenbäck

Chalmers, Civil and Environmental Engineering, Building Services Engineering

International Journal of Refrigeration

0140-7007 (ISSN)

Vol. 62 137-144

Driving Forces

Sustainable development

Areas of Advance


Subject Categories

Energy Systems



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