Computational and experimental study of the effect of secondary flow on the temperature field and primary flow in a heated horizontal tube

Abstract

The fully developed temperature field and axial velocity profile are measured for a fluid with a Prandtl number of 80 at the outlet of a long horizontal tube which is heated electrically. The defining partial differential equations are solved by finite difference techniques to obtain the secondary flow patterns as well as the temperature field and axial velocity field. Relatively large secondary flows are found for temperature differences between the wall and the fluid as low as 0·05°F. For (GP) 1 4 greater than 30 boundary layer theory appears to be a good approximation to the temperature field. There are large temperature gradients near the wall; the isotherms in the core are horizontal and there is a significant temperature variation in the vertical direction. Although the secondary flow had a large effect on the temperature field it had little effect on the axial velocity distribution as has been predicted for large Prandtl number. The secondary flow pattern shows relatively large upward velocities near the wall and small downward velocities in the core. The thicknesses of the velocity and temperature boundary layers are approximately equal. These results agree with a treatment of the problem, based on dimensional reasoning, that has been presented in a previous paper from this laboratory.