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

Abstract

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.

Design and Thermal Analysis of an Air Source Heat Pump Dryer for Food Drying

“…Food drying is an important part of production. There are significant drawbacks to the traditional way in which heat for drying is gained by burning fuel: it consumes a large amount of energy and it causes serious environmental problems, such as haze problems in China [1][2][3][4]. A heat pump is a device that converts medium-low temperature heat energy into medium-high temperature heat energy.…”

Experimental Test Stand of a Heat Pump Integrated in Air Handling Unit

“…Lauke esantis šilumokaitis pradeda šildyti, o viduje šaldyti. Taip vyksta, kol užšalęs šilumo kaitis, esantis lauke, nebus nutirpintas (Song et al, 2016;Bareika, 2013;Frik, 2019;Liu et al, 2018). Karštų dujų apėjimo linijos technologijos esmė ta, kad šaldymo agento suslėgtosios karštos dujos po kompresoriaus yra tiesiai nu kreipiamos į šilumos siurblio garintuvą, kad jį atitirpintų.…”

“…V š -exhaust fan) (Wenju et al, 2011;Lu et al, 2019;Song et al, 2016;Bareika, 2013;Karim et al, 2019;Qiu et al, 2019). Apibendrinant analizės rezultatus galima konstatuoti, kad eksperimentinis vėdinimo įrenginio su integruotu ši lumos siurbliu stendas turi atitikti šiuos reikalavimus:…”

A systematic review of recent air source heat pump (ASHP) systems assisted by solar thermal, photovoltaic and photovoltaic/thermal sources

“…abundant social benefits [6,7], and environmental-friendly characteristics [8,9]. ASHP systems have already been widely applied in different types of buildings [10,11].…”