The Effect of Buoyancy on Laminar Flow and Heat Transfer in Pipes

抄録

Buoyancy-induced secondary flows in a heated pipe rotating about a parallel axis are similar to those in a stationary horizontal heated pipe. The effect of buoyancy on fully developed laminar flows and heat transfer in rotating pipes and in horizontal pipes is studied by similarity analysis and computations. The similarity analysis reveals that the flows are characterized by a new fundamental parameter, K_LB, and the Prandtl number, Pr;K_LBplays a role of Peclet number in the cross-section and Pr determines the sensitivity of the axial primary flow to secondary flow. Heat transfer is basically independent of Pr. Based on the dimensionless governing equations, limiting behaviours of velocity and temperature fields are discussed. Similarity conclusions are supported by computational results of contours of velocity and temperature, the friction factor and heat transfer rate. Semi-empirical formulae for the friction factor and the Nusselt number are presented.