HEAT TRANSFER CHARACTERISTICS IN A DOUBLE-PIPE HEAT EXCHANGER EQUIPPED WITH COILED CIRCULAR WIRES

Zohir, A. E.; Habib, M.A.

doi:10.21608/jesaun.2012.114407

HEAT TRANSFER CHARACTERISTICS IN A DOUBLE-PIPE HEAT EXCHANGER EQUIPPED WITH COILED CIRCULAR WIRES

Document Type : Research Paper

Authors

A. E. Zohir ¹
M.A. Habib ²

¹ Mechanical Engineering Department, Tabbin Institute for Metallurgical Studies, Cairo, Egypt,

² Mechanical Engineering Department, King Fahd University of Petroleum and Minerals, Dhahran, Saudi Arabia

10.21608/jesaun.2012.114407

Abstract

The effects of insulating wires (acting as turbulators only), with circular cross section of 2mm diameter, forming a coil of different pitches on the heat transfer rates are experimentally investigated. The investigation is performed for turbulent water stream in a double-pipe heat exchanger for both parallel and counter flows (for comparison) with cold water in the shell side. The experiments are performed for flows with Reynolds numbers ranging from 4,000 to 14,000. Three different spring coiled wire pitch values are used. The experimental results reveal that the use of coiled circular wire turbulators leads to a considerable increase in heat transfer over those of a smooth wall tube. The mean Nusselt number increases with the rise of Reynolds number and the increasing of pitch for both parallel and counter flows. The convective heat transfer coefficient for the turbulent flow was found to increase with turbulators for all coiled wire pitch values with the highest enhancement of about 450% for the counter flow while it was 400% for the parallel one. Correlations for mean relative Nusselt numbers and coiled wire pitch are provided.

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