Reynolds analogy comparison of dimpled versus protrusion roughness
- North Carolina A and T State Univ., Greensboro, NC (United States). Mechanical Engineering Dept.
The effects of surface roughness on skin friction and heat transfer in wall-bounded flows has long been an area of major interest in fluid mechanics research. Applications of the acquired knowledge to this point range from the study of atmospheric boundary layers to the enhancement of heat transfer in heat exchanger systems. 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, with Reynold`s numbers ranging from 1.2 {times} 10{sup 6} to 2.8 {times} 10{sup 6} (based on test plate length). 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 are presented in terms of the Reynolds analogy, St = C{sub f}/2, 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 with the protrusion roughness studied.
- OSTI ID:
- 455408
- Report Number(s):
- CONF-951135--; ISBN 0-7918-1752-0
- Country of Publication:
- United States
- Language:
- English
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