Effect of surface roughness on heat transfer and fluid flow characteristics at low reynolds numbers in small diameter tubes
Abstract
The effect of surface roughness on pressure drop and heat transfer in circular tubes has been
extensively studied in literature. The pioneering work of Nikuradse [I] established the sand grain
roughness as a major parameter in defining the friction factor during laminar and turbulent flows.
Recent studies have indicated a transition to turbulent flows at Reynolds number values much below
2300 during single-phase flow in channels with small hydraulic diameters. In the present work, a
detailed experimental study is undertaken to investigate the roughness effects in small diameter
tubes. The roughness of the inside tube surface is changed by etching it with an acid solution. Two
tubes of 1.032 mm and 0.62 mm inner diameter are treated with acid solutions to provide three
different roughness values for each tube. The Reynolds number range for the tests is 500-2600 for
1.067 mm tube and 900-3000 for 0.62 mm tube.
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