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Experimental Investigation of Knudsen Number Effect on Gas Heat Transfer in Micro-tubes (Knudsen Number Effect in Micro-tubes)
Jaroslav Hemrle, Sadanari Mochizuki and Akira Murata

Results of heat transfer experiments in small-diameter tubes with focus on the effect of Knudsen number, Kn, are presented. The test section consisted of large number of small diameter tubes. Kn was controlled directly by regulating the pressure level inside the test section. The experiment was conducted with air for ranges of 0.01<Re<22 and 0.0001<Kn<0.8. Observed effects of Kn were in qualitative agreement with velocity slip and temperature jump theory and heat transfer performance decreased monotonically with increasing Kn. For Kn=0.01 and 0.1 the heat transfer coefficient was reduced by approximately 5 and 25%, respectively.

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