On the combined effect of forced and free convection heat transfer in laminar boundary layer flows

✍ Scribed by Andreas Acrivos

• Publisher: Elsevier Science
• Year: 1966
• Tongue: English
• Weight: 798 KB
• Volume: 21
• Category: Article
• ISSN: 0009-2509
• DOI: 10.1016/0009-2509(66)85027-3

✦ Synopsis

The phenomenon of combined forced and free convection heat transfer in laminar boundary layer flows, in which the momentum equation is coupled with the energy equation on account of the presence of the gravitational term, is analyzed theoretically. It is shown that for large values of the Prandtl number, Pr, the relative importance of the forced and the free convection is controlled by the parameter Gr/Rea Prr/a, whereas for Pr < 1 the controlling parameter is Gr/Rea. An approximate but reliable technique is then developed for predicting the shear stress and the rate of heat transfer throughout the "intermediate" regime, for general surface geometries and for arbitrary velocity distributions at the edge of the boundary layer. The analysis shows moreover that this transition region is usually narrow for the case of aiding flows, and that, depending on the value of (Gr/Re2 Prrj3) or (Gr/ Rea), the flow may be described by either the pure forced or the pure free convection equations alone.