RT Journal Article ID 3a75ba9f6a69cb6f A1 Kithcart, Mark E. A1 Klett, David E. T1 Heat Transfer and Skin Friction Comparison of Dimpled Versus Protrusion Roughness JF Journal of Enhanced Heat Transfer JO JEH(T) YR 1996 FD 1996-12-01 VO 3 IS 4 SP 273 OP 280 AB This paper presents results of skin friction and heat transfer measurements made on flat plates with closely-spaced, three-dimensional surface roughness elements (hemispherical dimples, hemispherical protrusions, and rectangular protrusions) in turbulent boundary-layer flow at velocities ranging from 18 to 40 m/s (roughness Reynold's nos. from 1500 to 4000). The roughness element densities for each plate were chosen using Simpson's sand-grain roughness correlation to study the effects of spacing on drag and heat transfer in the vicinity of the peak of the Simpson-Dvorak correlation curve. The data is presented in terms of the efficiency factor, n = (Str/Sts/(Cfr/Cfs), to provide a means of comparing the effects on skin friction and heat transfer collectively. Dimpled surfaces have the advantage of significantly increasing heat transfer at a lower penalty in increased drag compared to the protrusion roughness studied. PB Begell House LK https://www.dl.begellhouse.com/journals/4c8f5faa331b09ea,0a32880b5a8e6054,3a75ba9f6a69cb6f.html