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International Heat Transfer Conference 9

ISSN: 2377-424X (online)
ISSN: 2377-4371 (flashdrive)

CONSTRICTION RESISTANCE OF DROPWISE CONDENSATION ON POLYMER COATED SURFACE

Takaharu Tsuruta
Kyushu Institute of Technology, Sensui 1-1, Tobata, Kitakyushu, Fukuoka 804-8550, Japan

Masayuki Shirahama
Department of Mechanical Engineering, Kyushu Institute of Technology Tobata-ku, Kitakyushu 804, Japan

Takashi Masuoka
The University of Kitakyushu, and Department of Mechanical Engineering, Kyushu University, Kyushu, Japan

DOI: 10.1615/IHTC9.3760
pages 97-102

Abstract

Various experiments and theories have been introduced, to explain the effect of polymer coating on the dropwise condensation heat transfer as will be sighted in this paper. By taking account of the constriction resistance caused by the inhomogeneous heat flux through the polymer layer, the authors derived the fundamental equations describing the effect of coating thickness. The combination of single-droplet constriction resistance with the instantaneous drop-size distributions leads to a correlation for the Nusselt number. In the experiments, fluoroethylene propylene (FEP) was coated on the copper block and heat-transfer measurements were performed for dropwise condensation of steam in a pressure range from atmospheric down to 2 kPa. The measured heat-transfer coefficients decreased with increasing polymer thickness and they agreed satisfactorily with the theoretical predictions. It is then confirmed that an increase of thickness of polymer coating raises the constriction resistance and reduces the heat-transfer coefficient.

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