Turbulent heat and momentum transfer for gases in a circular tube at wall to bulk temperature ratios to seven

Abstract Measurements are reported for local friction and heat-transfer coefficients with constant heat flux in an electrically heated circular tube. Precooled nitrogen in turbulent flow was used to obtain local wall to bulk temperature ratios from 1·24 to 7·54. The Inconel test section had a 40 diameter hydrodynamic entry section and a 160 diameter heated section. The bulk inlet Reynolds numbers covered the range from 18 300 to 279 000. Correlations in terms of both the bulk and the modified wall Reynolds numbers are presented for the local friction factors; the local heat-transfer results are presented in terms of the wall to bulk temperature ratio with bulk properties and also directly on the modified wall Reynolds number. Both the friction and heat-transfer results are shown to be significantly affected by the influence of the variable properties. Entrance region effects for both the heat-transfer and friction coefficients are discussed.