Indoor thermal comfort analysis during dynamic frosting-defrosting process of air source heat pumps

Wang, Wei, Ren, Jianyu, Tan, Yang, Luo, Zhiwen ORCID: https://orcid.org/0000-0002-2082-3958, Wei, Wenzhe, Jin, Xinyue, Sun, Yuying and Zhang, Chunxiao 2026. Indoor thermal comfort analysis during dynamic frosting-defrosting process of air source heat pumps. Building and Environment 289 , 114100. 10.1016/j.buildenv.2025.114100

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Abstract

During the defrosting operation of air source heat pump (ASHP) and a period thereafter, it stops supplying heating to indoor space. This leads to indoor temperature drop significantly, and further causes thermal discomfort for subjects. To improve the thermal comfort during the frosting-defrosting process of ASHP, two test rigs, one air-water heat pump (AWHP) heating system and one air-air heat pump (AAHP) heating system, were built in an artificial climate chamber. Under the standard frosting condition of 2/1 °C, space heating experiments were conducted to investigate the variations of indoor environment and thermal sensation of subjects during the frosting-defrosting process. Results showed that the indoor temperature declined notably during the defrosting operation for AWHP and AAHP. Specifically, the temperature decreased 2.6–4.6 °C for AWHPs, and 1.4–1.9 °C for AAHPs. Owing to the decrease in indoor temperature and the increase in draught sensation, the thermal sensation of subjects in AWHP-heated rooms and AAHP both decreased significantly. 78.4 % subjects in AWHP-heated rooms and 73.5 % subjects in AAHP-heated rooms reported a downgrade in thermal sensation after defrosting. Then, the acceptable indoor temperature at the beginning time of defrosting were calculated, and they were respectively 20.74–25.09 °C and 19.91–24.45 °C for the AWHP-heated rooms and AAHP.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Schools > Architecture
Publisher:	Elsevier
ISSN:	0360-1323
Date of First Compliant Deposit:	9 December 2025
Date of Acceptance:	2 December 2025
Last Modified:	10 Dec 2025 11:00
URI:	https://orca.cardiff.ac.uk/id/eprint/183073

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