S-ST-1-12 Mixed Convection Heat Transfer in Vertical Tubes

L. Huang

Using water and propylene glycol in vertical tubes with two different diameters, HTRI recently collected upflow heating data covering a wide range of Reynolds numbers, Grashof numbers, and Prandtl numbers. Mixed convection in laminar, transition, and turbulent forced flow regimes was also studied extensively. These data, together with literature methods and data, form the foundation for evaluating and developing HTRI single-phase heat transfer methods.

In this report, we develop a flow regime map that identifies dominant heat transfer mechanisms. We also propose an asymptotic method for mixed convection that uses literature correlations for laminar forced and natural convection, as well as a new turbulent natural convection correlation. Because a laminar-like flow regime always occurs at the tube entrance, the heat transfer coefficient in this regime is better correlated using laminar-type correlations. The new methods, supported by the new flow regime map, significantly improve data prediction and greatly increase confidence in mixed convection heat transfer in vertical tubes.