Experimental Investigation of Heat Transfer in Coiled Annular Ducts

Abstract

Forced convection heat transfer in coiled annular ducts was investigated experimentally. Average heat transfer coefficients were obtained for both laminar and transition flows. Two coiling diameters and two annulus radius ratios were used in the study. The data were correlated with Dean number and Reynolds number separately and compared with the available studies of coiled circular tubes and straight annular ducts. It was found that coiling augments the heat transfer coefficients above the values for a straight annulus especially in the laminar region. However, the augmentation is less than would be expected for a coiled circular tube. The augmentation decreases as the flow enters the transition region.