Heat Transfer Characteristics of Radial Liquid Film Flow. Local Heat Transfer Characteristics near Turbulent Trnasition Point.

Abstract

The heat transfer characteristics of radial liquid film flow were investigated experimentally. The change of local heat transfer coefficient α in the radial direction was measured, using a small heat-transfer surface of 1 mm diameter. Experimental α's agreed with theoretical ones calculated by the profile method for laminar and turbulent region. In the laminar region, α monotonously decreases in the radial direction. Special attention was paid to the turbulent transition region. When the film flow reaches the transition point, α begins to increase with development of the turbulent boundary layer. After α takes the extremum value, it decreases again by the rate expressed by the theory of the turbulent flow region. The heat transfer characteristics near the transition point well explain the film surface behavior observed in the past. In the downstream region of the transition point, the turbulence decays rapidly and the film flow shows a tendency to shift to a laminar like flow.