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Effect of relative humidity on heat transfer across the surface of an evaporating water droplet in air flow

Published online by Cambridge University Press:  10 April 2009

RYOICHI KUROSE ,
AKITOSHI FUJITA  and
SATORU KOMORI
RYOICHI KUROSE*
Affiliation:
Department of Mechanical Engineering and Science and Advanced Research Institute of Fluid Science and Engineering, Kyoto University, Yoshida-honmachi, Sakyo-ku, Kyoto 606-8501, Japan
AKITOSHI FUJITA
Affiliation:
Department of Mechanical Engineering and Science and Advanced Research Institute of Fluid Science and Engineering, Kyoto University, Yoshida-honmachi, Sakyo-ku, Kyoto 606-8501, Japan
SATORU KOMORI
Affiliation:
Department of Mechanical Engineering and Science and Advanced Research Institute of Fluid Science and Engineering, Kyoto University, Yoshida-honmachi, Sakyo-ku, Kyoto 606-8501, Japan
*
†Email address for correspondence: kurose@mech.kyoto-u.ac.jp
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Abstract

A three-dimensional direct numerical simulation (DNS) is applied to flows inside and outside an evaporating spherical water droplet in air, and the effect of relative humidity on the heat transfer between the droplet and ambient air is investigated. The initial air temperature is set to be 15 K higher than the initial droplet temperature. The results show that the local evaporation heat loss indicates the maximum on the front of the droplet and decreases on going from the front to the rear, and the reduction on the rear becomes marked for high-droplet Reynolds numbers. This is because the evaporation rate is suppressed on the rear surface by the presence of flow separations behind the droplet. The droplet temperature decreases in the low-humidity condition, whereas it increases in the high-humidity condition. This difference is caused by the heat balance of evaporation heat loss and convective heat gain from ambient air at the droplet surface.

Type
Papers
Information
Journal of Fluid Mechanics , Volume 624 , 10 April 2009 , pp. 57 - 67
Copyright
Copyright © Cambridge University Press 2009

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