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Journal of Flow Visualization and Image Processing
SJR: 0.161 SNIP: 0.312 CiteScore™: 0.1

ISSN Print: 1065-3090
ISSN Online: 1940-4336

Journal of Flow Visualization and Image Processing

DOI: 10.1615/JFlowVisImageProc.v2.i3.70
pages 267-283

VISUALIZATION OF LOCAL HEAT TRANSFER IN A PIN FIN CHANNEL WITH LIQUID CRYSTALS

S. C. Lau
Lynntech Inc., 7610 Eastmark Drive, College Station, Texas 77840; Department of Mechanical Engineering, Texas A and M University, College Station, Texas 77843-3123
L. M. Russell
NASA-Lewis Research Center, Cleveland, Ohio 44135
D. R. Thurman
NASA-Lewis Research Center, Cleveland, Ohio 44135
S. A. Hippensteele
NASA-Lewis Research Center, Cleveland, Ohio 44135

ABSTRACT

Thermochromic liquid crystals and an Inconel foil heater were used to map the detailed local heat transfer distributions in a rectangular pin fin channel with ejection holes along one side wall and the end wall. The staggered array of pins had 12 alternate rows of three and two pins. The pin height-to-diameter ratio was 1.0 and the spacings between two adjacent pins was 2.5 times the pin diameter. Results were obtained for Reynolds numbers based on the pin diameter and maximum velocity in the pin fin channel of approximately 25,000, 40,000, 60,000, and 90,000. The local heat transfer coefficient was generally low in the first row, high in the third and fourth rows, and decreased downstream of the fifth row of pin fins along the channel, as air exited through the ejection holes. The local heat transfer coefficient was very high at the bases of the pins, relatively high near the ejection holes, and was the lowest near the corner between the side wall with the ejection holes and the end wall. The heat transfer coefficient distributions with and without end wall flow ejection differed very little over the upstream half of the channel. Near the end wall, however, the heat transfer distributions were very different, with lower values but slightly larger variations in the case of no end wall flow ejection. Under the conditions of the present investigation, the relative local Nusselt number distribution appeared to be independent of the flow Reynolds number.


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