A study on the performance of the airside heat exchanger under frosting in an air source heat pump water heater/chiller unit

Yao, Yang; Jiang, Yiqiang; Deng, Shiming; Ma, Zhenqiang

doi:10.1016/j.ijheatmasstransfer.2004.03.013

Cited by 153 publications

(41 citation statements)

References 12 publications

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“…In order to obtain meaningful experimental results, it was necessary to ensure that frost accumulated on the surface of the three circuits was even at first. For an ASHP unit with a multi-circuit outdoor coil, it is hard to make the frost evenly accumulated on the surface of the outdoor coil, as many parameters affect frosting performance [31]. However, in this study, modulating valves installed at the inlet refrigerant pipe to each circuit (as shown in Fig.…”

Section: Three Experimental Casesmentioning

confidence: 99%

An experimental study on defrosting performance for an air source heat pump unit with a horizontally installed multi-circuit outdoor coil

et al. 2016

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Highlights• Negative effects due to gravity eliminated when outdoor coil horizontally installed.• Defrosting efficiency increased 9.8% after outdoor coil horizontally installed.• Defrosting efficiency decreased 6.6% when air fan reversed to blow the melted frost.• Total mass of the retained water collected decreased 222 g less after wind blowing.• Higher DEV respected better defrosting performance for multi-circuit outdoor coils. 2 AbstractWhen frost forms and accumulates over the outdoor coil's surface in an air source heat pump (ASHP) unit, system operating performance will be dramatically deteriorated.Reverse cycle defrosting is the most widely used standard defrosting method. A previous related study reported that downwards flowing of melted frost due to gravity over a vertical multi-circuit outdoor coil would decrease the reverse cycle defrosting performance. If the outdoor coil can be changed to horizontally installed, the flow path of melted frost over coil surface can be shortened, and the flow directions of refrigerant and melted frost changed from opposite to orthogonal. Consequently, a better defrosting performance is expected. In this paper, therefore, an experimental study on defrosting performance for an ASHP unit with a horizontally installed multi-circuit outdoor coil was conducted. Experimental results show that, when a vertical outdoor coil was changed to horizontally installed, the defrosting efficiency increased 9.8%, however, with the same defrosting duration at 186 s. Furthermore, when the outdoor air fan was reversed to blowing the melted frost during defrosting, the total mass of the retained water collected decreased 222 g. However, the defrosting efficiency was not increased, but decreased 6.6% because of the heat transfer enhanced between hot coil and cold ambient air.

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Section: Three Experimental Casesmentioning

confidence: 99%

An experimental study on defrosting performance for an air source heat pump unit with a horizontally installed multi-circuit outdoor coil

et al. 2016

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“…Air source heat pump (ASHP) units used as cooling or heating source for building heating, ventilating and air conditioning installations have been increasingly and widely applied over the recent decades in many parts of the world [2,3]. However, when an ASHP unit operates at a low temperature and high humidity environment, frost can be formed and accumulated over the surface of its outdoor coil [4,5]. The outdoor coil is usually of multi-circuit structure on the refrigerant side in order to minimize its refrigerant pressure loss and enhance the heat transfer between refrigerant and outdoor air [4][5][6][7][8][9][10][11][12][13][14][15][16][17].…”

Section: Introductionmentioning

confidence: 99%

“…However, when an ASHP unit operates at a low temperature and high humidity environment, frost can be formed and accumulated over the surface of its outdoor coil [4,5]. The outdoor coil is usually of multi-circuit structure on the refrigerant side in order to minimize its refrigerant pressure loss and enhance the heat transfer between refrigerant and outdoor air [4][5][6][7][8][9][10][11][12][13][14][15][16][17]. Frosting adversely affects the operational performance and hence the energy efficiency of an ASHP unit, therefore periodic defrosting is necessary [6].…”

Section: Introductionmentioning

confidence: 99%

A modeling study on alleviating uneven defrosting for a vertical three-circuit outdoor coil in an air source heat pump unit during reverse cycle defrosting

2016

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“…Although previous research related to both frosting and reverse-cycle defrost for ASHPs have been carried out and reported, they are mainly for system modeling (Krakow et al, 1993;Yao et al 2004), or for improving the operating characteristics of ASHPs (Anandet al 1989;O'Neal et al 1991;Nutter et al 1996;Jhee et al, 2002;Watters et al 2002;Huang et al, 2004;Guo et al 2008). The fundamental problem of insufficient heat available during reverse-cycle defrosting remains unsolved.…”

Section: Introductionmentioning

confidence: 99%

An Experimental Study on the Defrosting Performance of a PCM-Based Reverse-Cycle Defrosting Method for Air Source Heat Pumps

Deng

Jiao

2010

Int. J. Air-Cond. Ref.

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When an ASHP operates in heating mode, frost can be accumulated on the surface of its outdoor coil. Currently the most widely used defrosting method for ASHPs is reverse cycle defrost. However, the fundamental problem for such a method is that there is insufficient heat available for ASHPs during defrosting. This paper reports on an experimental study of developing a novel reverse-defrosting method which is thermal energy storage (TES) based using phase change material (PCM). Comparative experiments were carried out at two operating conditions: standard defrosting condition and the PCM-based defrosting condition. Results indicated that the use of this PCM-based reverse defrosting method could help shorten defrosting time, improve indoor thermal comfort for occupants, as compared with the use of standard defrosting method. Furthermore, the experimental results also suggested that storing heat in PCM would not degrade the quality of space heating provided by the ASHP during heating operation.

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A study on the performance of the airside heat exchanger under frosting in an air source heat pump water heater/chiller unit

Cited by 153 publications

References 12 publications

An experimental study on defrosting performance for an air source heat pump unit with a horizontally installed multi-circuit outdoor coil

An experimental study on defrosting performance for an air source heat pump unit with a horizontally installed multi-circuit outdoor coil

A modeling study on alleviating uneven defrosting for a vertical three-circuit outdoor coil in an air source heat pump unit during reverse cycle defrosting

An Experimental Study on the Defrosting Performance of a PCM-Based Reverse-Cycle Defrosting Method for Air Source Heat Pumps

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