Evaluation of cooling effects: outdoor watermist fan

This article summarises a research paper ‘Evaluation of cooling effects: outdoor water mist fan’ by Craig Farnham, Kazuo Emura & Takeo Mizuno published in 2015 in --Building Research & Information, 43:3, 334-345, DOI: 10.1080/09613218.2015.1004844.

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Evaporative spray cooling can improve thermal comfort and provide relief from thermal stress, even in a subtropical climate such as Japan. An experiment was carried out that combined a water mist spray with a fan and assessed its impact on the comfort of 141 participants on hot summer days. Participants were visitors to a public event held on 10–11 August 2013 in Osaka, Japan.

It was found that the cooling effect was highly efficient. The forced convection of the fan helped cool the skin and accelerate the evaporation of mist droplets that had adhered to skin and clothing. This produced an almost instant decrease in skin temperature. The mist and fan combination achieved localised cooling rates of more than 200 W/m2. Exposed skin temperatures could drop 2 K within 10 s with light wetting and were 1 K cooler even after leaving the mist. There was no correlation between time spent in the mist and degree of effect.

75% of respondents said the wettedness from the mist was pleasant, while 75% had claimed their state of wettedness before entering the mist (due to their own sweating) was unpleasant.

This technology has the potential to reduce heat stress and discomfort, particularly at large outdoor events and festivals. It could also reduce cooling loads within buildings by providing inhabitants with thermal relief outdoors. Continuing research will measure the effects of misting fans on people engaged in moderately strenuous activity in hot conditions.

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Craig Farnham, Kazuo Emura & Takeo Mizuno (2015) Evaluation of cooling effects: outdoor water mist fan, Building Research & Information, 43:3, 334-345, DOI: 10.1080/09613218.2015.1004844.

Read the full paper at Taylor & Francis Online.

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