Connective Heat Transfer in Annular Passage with High Heat Flux

Abstract

An experimental study was performed on convective heat transfer of concentric annular gas flow with the inner tube heated. The examined region of the Reynolds number ranged from 6 000 to 10 000 and that of the dimensionless heat flux parameter from 0.2×10^-3 to 5.5×10^-3. Special attention was p. aid to the examination of the existing correlations for high heat flux heat transfer and also to the criteria for the occurrence of so-called laminarization of the annular flow. No laminarization was detected even for the highest heat flux case although they satisfied the proposed criteria for the occurrence of laminarization for the circular tube flows. It is anticipated, therefore, that the annular flow is less vulnerable to laminarization than is the circular tube flow. Experimental results also show that as the exponent of (T_w/T_in) it is recommended to use 0.38 instead of 0.20 or 0.31, which were proposed by the former authors for heat transfer with variable properties.