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Effect of wall roughness on convective heat transfer in commercial pipes
Author(s) -
Smith J. W.,
Epstein Norman
Publication year - 1957
Publication title -
aiche journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.958
H-Index - 167
eISSN - 1547-5905
pISSN - 0001-1541
DOI - 10.1002/aic.690030220
Subject(s) - reynolds number , prandtl number , heat transfer , mechanics , friction factor , turbulent prandtl number , thermodynamics , surface finish , convective heat transfer , materials science , nusselt number , physics , turbulence , composite material
Heat transfer and friction measurements were made for air flow through a smooth copper pipe and six other commercial pipes, with a ratio of diameter to equivalent sand roughness varying from 640 to 64. The Reynolds number range was 10,000 to 80,000. Though some increase in heat transfer coefficients with roughness was found, the heat transmission per unit power loss always decreased. The momentum–heat‐transfer anlogies of Reynolds and Colburn are shown to be inadequate for handling the experimental data. Those of Prandtl and Taylor, von Kármán, and Pinkel fail to show a required Reynolds number dependence of j h when friction factor has become independent of Reynolds number for a rough pipe. Martinelli's equation shows such dependence and, even in approximate form, gives good prediction of the experimental results.