Please use this identifier to cite or link to this item: http://hdl.handle.net/10397/10873
Title: Study on the operating performance of cross hot-gas bypass defrosting system for air-to-water screw heat pumps
Authors: Wang, Z
Yang, H 
Chen, S
Keywords: Air-to-water screw heat pump
COP
Cross hot-gas bypass defrosting
Pressure
Temperature
Issue Date: 2013
Publisher: Pergamon Press
Source: Applied thermal engineering, 2013, v. 59, no. 41671, p. 398-404 How to cite?
Journal: Applied thermal engineering 
Abstract: Large-scale air-to-water screw heat pumps often operate with substantial frost formation on the air side of evaporators in winter, and the frost layer has to be melted away periodically. This paper presents a defrosting method for air-to-water screw heat pumps, i.e. the cross hot-gas bypass defrosting method, which uses two air heat exchangers for hot air from one air heat exchanger to melt the frost and absorb heat from another heat exchanger through the corresponding four-way reversing valve. The principle and process of this method are illustrated. The dynamic characteristics are experimentally investigated on a 359 kW air-to-water screw heat pump. The discharge temperature of the unit is at the normal range and the pressure varies little. A higher suction pressure is needed to achieve low pressure protection. The time period needed for the combination of heating and defrosting processes is short and it is not necessary to shutdown the compressor for defrosting so that a longer heating time period is possible. The inlet & outlet water temperature can be kept at around 30 C and high heating COP is obtained. The test results show that the units work as expected.
URI: http://hdl.handle.net/10397/10873
ISSN: 1359-4311
EISSN: 1873-5606
DOI: 10.1016/j.applthermaleng.2013.06.007
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