TY - JOUR
T1 - Experimental study on frost unevenly distributed and melted frost downwards flowing during defrosting for ASHPs
AU - Song, Mengjie
AU - Fan, Cheng
AU - Mao, Ning
AU - Wang, Zhihua
AU - Xia, Yudong
N1 - Publisher Copyright:
© 2019 The Authors. Published by Elsevier Ltd.This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/)Peer-review under responsibility of the scientific committee of ICAE2018 The 10th International Conference on Applied Energy.
PY - 2019
Y1 - 2019
N2 - For an air source heat pump (ASHP) unit, uneven frost distribution would result in mal-defrosting, or adversely degrade system defrosting efficiency. Previous investigations demonstrated that, for an ASHP unit with a multi-circuit outdoor coil, when the frosting evenness value (FEV) on its surface of outdoor coil is higher, the defrosting efficiency would also be higher. On the other hand, as reported, the downwards flowing melted frost during defrosting would also play negative effects on defrosting performance. Although the comprehensive influence of the two factors, uneven frost distribution and the downwards flowing melted frost, had been experimentally investigated, the influence of uneven frost distribution or the FEV on negative effect of downwards flowing melted frost was still unknown. As a fundamental and interesting problem, it is meaningful to be explored. It was therefore quantitatively analyzed here basing on six experimental cases. Water collecting trays were used to take away the melted frost during defrosting in three cases, and the other three ones without trays installed stood for the traditional status. Meanwhile, their FEVs of two groups were separately adjusted to be at three different levels. Results clearly showed the positive effects of increasing FEV and taking away the melted frost on system defrosting efficiency. After the melted frost was taken away, the FEV effects was increased. The increase of defrosting efficiency seems unchanged, but the reduction of defrosting duration was obviously increased from 17 s to 22 s. However, the differences of defrosting duration and efficiency changed were too small when melted frost was locally drained or not. More experimental cases with lower FEVs should be carried out.
AB - For an air source heat pump (ASHP) unit, uneven frost distribution would result in mal-defrosting, or adversely degrade system defrosting efficiency. Previous investigations demonstrated that, for an ASHP unit with a multi-circuit outdoor coil, when the frosting evenness value (FEV) on its surface of outdoor coil is higher, the defrosting efficiency would also be higher. On the other hand, as reported, the downwards flowing melted frost during defrosting would also play negative effects on defrosting performance. Although the comprehensive influence of the two factors, uneven frost distribution and the downwards flowing melted frost, had been experimentally investigated, the influence of uneven frost distribution or the FEV on negative effect of downwards flowing melted frost was still unknown. As a fundamental and interesting problem, it is meaningful to be explored. It was therefore quantitatively analyzed here basing on six experimental cases. Water collecting trays were used to take away the melted frost during defrosting in three cases, and the other three ones without trays installed stood for the traditional status. Meanwhile, their FEVs of two groups were separately adjusted to be at three different levels. Results clearly showed the positive effects of increasing FEV and taking away the melted frost on system defrosting efficiency. After the melted frost was taken away, the FEV effects was increased. The increase of defrosting efficiency seems unchanged, but the reduction of defrosting duration was obviously increased from 17 s to 22 s. However, the differences of defrosting duration and efficiency changed were too small when melted frost was locally drained or not. More experimental cases with lower FEVs should be carried out.
KW - Air source heat pump
KW - Defrosting efficiency
KW - Frost distribuiton
KW - Frosting evenness value
KW - Melted frost
UR - http://www.scopus.com/inward/record.url?scp=85063886920&partnerID=8YFLogxK
U2 - 10.1016/j.egypro.2019.02.045
DO - 10.1016/j.egypro.2019.02.045
M3 - Conference article
AN - SCOPUS:85063886920
SN - 1876-6102
VL - 158
SP - 2826
EP - 2833
JO - Energy Procedia
JF - Energy Procedia
T2 - 10th International Conference on Applied Energy, ICAE 2018
Y2 - 22 August 2018 through 25 August 2018
ER -