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First Thermal and Fluids Engineering Summer Conference

ISSN: 2379-1748
ISBN: 978-1-56700-430-4

FLOW BOILING OF WATER IN A HYDROPHOBIC COATED SMALL DIAMETER TUBE

DOI: 10.1615/TFESC1.mph.013156
pages 1835-1846

Manoharan Aravinthan
Department of Mechanical Engineering, Indian Institute of Technology Madras, Chennai, India - 600036

Sourav Sarkar
Indian Institute of Technology Madras, Chennai, India - 600036

Sarit Kumar Das
Heat Transfer and Thermal Power Laboratory, Mechanical Engineering Department,Indian Institute of Technology Madras, Chennai, India - 600036; Indian Institute of Technology Ropar, Rupnagar-140001, Punjab, India

Arcot R Balakrishnan
Dept. of Chemical Engineering, Indian Institute of Technology, Madras, Chennai - 600 036, India


KEY WORDS: Hydrophobic surface, wettability, flow boiling average heat transfer, two phase frictional pressure drop.

Abstract

Surface wettability is the ability of the liquid to remain in contact with a solid surface. In the present study, the experiments were conducted in the hydrophobic coated copper tube and regular tube to study the wettability effect on flow boiling of deionised water under subcooled conditions. The hydrophobic surface is fabricated inside a copper tube with an inside diameter of 3 mm and with length of 300 mm by Electroless Galvanic Deposition method. The flow boiling experiments were conducted for mass fluxbetween 100-650 kg/m2s and the heat flux wasvaried between 10-150 kW/m2. The measured surface roughness value of the hydrophobic coated surface is 5.65µm and the surface contact angle is 143.5°. The flow boiling frictional drop and two phase heat transfer was measured and compared between the regular and the hydrophobic copper minitube. The average flow boiling heat transfer co-efficient in the hydrophobic copper tube is higher than the regular tube due to nucleation site density. Further, it was found that the two phase frictional pressure drop is higher for the hydrophobic coated tube than the regular tube. Hence, it may be concluded that surface wettability is an important parameter in flow boiling heat transfer of small diameter tubes.

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