The effects of outdoor air-side fouling on frost growth and heat transfer characteristics of a microchannel heat exchanger: An experimental study

•Experimental data of frost formation on a microchannel heat exchanger.•Impacts of relative humidity, face velocity, and fouling level.•Surprisingly, light fouling increased heat transfer 1% and frost formation rate 19%.•Heavy fouling decreased the heat transfer and frost formation rates. Air source...

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Bibliographic Details
Published in:International journal of heat and mass transfer 2020-04, Vol.151, p.119423, Article 119423
Main Authors: Hu, Yifeng, Yuill, David P., Ebrahimifakhar, Amir
Format: Article
Language:English
Subjects:
Air flow
Air source heat pump
Coils
ENGINEERING
Enthalpy
Flow velocity
Fouling
Frost formation
Heat exchangers
Heat pumps
Heat transfer
Laboratories
Microchannel heat exchanger
Microchannels
Particulates
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Summary:•Experimental data of frost formation on a microchannel heat exchanger.•Impacts of relative humidity, face velocity, and fouling level.•Surprisingly, light fouling increased heat transfer 1% and frost formation rate 19%.•Heavy fouling decreased the heat transfer and frost formation rates. Air source heat pumps have the potential to efficiently heat and cool buildings, but their effectiveness in many climates is limited by frost growth on the outdoor heat exchanger in heating mode. These heat exchanger coils are also subject to fouling from fibers and particulates outdoors. Frost and fouling have each independently been studied extensively, and newly available research on fouling provides a method to realistically foul the air-side of coils in the laboratory. The current paper uses this method to conduct the first laboratory study of the important interactions between fouling and frost growth for a heat pump outdoor coil. A microchannel heat exchanger is tested clean and fouled, with variations in fouling level, humidity, and initial face velocity of air. Air flow rate is allowed to vary with resistance, and a surprising result is that light fouling increases heat transfer and frost growth rates, even with a 3.5% reduction in initial airflow caused by the fouling. However, heavier fouling decreases both rates. When frost growth is normalized to heat transfer, it is found to be increased by fouling; i.e. the coil's sensible heat ratio decreases.
ISSN:0017-9310
1879-2189
DOI:10.1016/j.ijheatmasstransfer.2020.119423