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A novel Temperature-Humidity-Time defrosting control method based on a frosting map for air-source heat pumps.

Author(s) : ZHU J., SUN Y., WANG W., et al.

Type of article: Article, IJR article

Summary

To improve the defrosting accuracy and the energy efficiency of the air-source heat pump (ASHP) under frosting and defrosting conditions, a novel Temperature-Humidity-Time (T-H-T) defrosting control method, based on a frosting map for the ASHP unit, is proposed in this paper. A field test was conducted for two heating seasons, to verify the feasibility and applicability of the T-H-T method. The advantages of the T-H-T method, compared to the conventional Temperature-Time (T-T) defrosting control method, are presented. In total, eight cases are shown in this paper. Cases 1 to 4 were chosen to reveal the T-H-T performance under different frosting conditions. It was found that no matter what kind of frosting conditions, defrosting was always initiated in a similar situation: ~90 % of the outdoor coil surface was covered by frost; the temperature difference between the compressor suction and discharge increased by ~20 %; and the heating capacity decreased by ~30 %. These results indicate that the T-H-T method can make an accurate decision under different frosting conditions. Cases 5a, 5b and Cases 6a, 6b were two groups of cases to compare the advantages of the T-H-T method against the conventional T-T method. Cases 5a and 5b were chosen for the non-frosting condition. It was found that the T-T method initiated the defrosting operation 31 times within 24 hours. However, none of the defrosting operations was conducted for the T-H-T method. Cases 6a and 6b were chosen to compare these two methods under consecutive and variable frosting conditions. For the T-T method, 37 % of the defrosting processes were found to be executed under conditions where defrosting was not necessary. However, for the T-H-T method, all the defrosting controls were found to be accurate and reasonable. These results indicated that the novel T-H-T method is suitable for the defrosting control of the ASHP, and has a more competitive performance than the conventional T-T method.

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Pages: 45-54

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Details

  • Original title: A novel Temperature-Humidity-Time defrosting control method based on a frosting map for air-source heat pumps.
  • Record ID : 30014561
  • Languages: English
  • Source: International Journal of Refrigeration - Revue Internationale du Froid - vol. 54
  • Publication date: 2015/06

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