Experimental study on defrosting start control strategy for ASHPs

Mengjie Song, Ning Mao*

*Corresponding author for this work

Research output: Contribution to journalConference articlepeer-review

3 Citations (Scopus)

Abstract

In applications, the defrosting operation of an air source heat pump (ASHP) unit is always started with a pre-set time, corresponding to a fixed mass of frost accumulation, and thus resulting in series of mal-defrosting phenomenon. The exact defrosting initiation time is hard to be quantitatively given due to the dynamic and uneven frosting conditions. For an ASHP unit with a multi-circuit outdoor coil, when the melted frost was locally drained during defrosting, the optimization of start defrosting control strategy becomes more complicated. Here, this fundamental problem was experimentally investigated, with frost evenly distributed on the surface of the outdoor coil at the start of defrosting. Defrosting performance of the experimental ASHP unit at different frost accumulations were then comparatively analyzed, with the melted frost local drainage specially considered. These physical parameters include the temperature of tube surface and melted frost, compressor suction and discharge pressures and their difference, thermal energy taken from indoor air and electricity inputs on compressor and fans during defrosting, etc. Results suggest that, the defrosting efficiency reached its peak at 46.05% when frost accumulation was at 930 g. After the melted frost was locally taken away during defrosting, it reached its peak at 51.80% when frost accumulation was at 933 g. Thus, the time-based start defrosting control strategy was demonstrated to be fundamentally optimized with this method. Contributions of this study could be used for adjusting the control strategy of ASHP units, which are valuable to energy saving in industrial applications.

Original languageEnglish
Pages (from-to)438-443
Number of pages6
JournalEnergy Procedia
Volume152
DOIs
Publication statusPublished - 2018
Externally publishedYes
Event2018 Applied Energy Symposium and Forum, Carbon Capture, Utilization and Storage, CCUS 2018 - Perth, Australia
Duration: 27 Jun 201829 Jun 2018

Keywords

  • Air source heat pump
  • Control strategy
  • Defrosting efficiency
  • Frost accumulation
  • Melted frost

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Song, M., & Mao, N. (2018). Experimental study on defrosting start control strategy for ASHPs. Energy Procedia, 152, 438-443. https://doi.org/10.1016/j.egypro.2018.09.250