Heat Transfer in Turbulent Separated Flow

Abstract

An investigation was carried out with the object of determining the physical effects of separation and the associated reattachment and redevelopment, upon the heat transfer characteristics of turbulent flow in pipes and to compare the results of these flow conditions with the fully developed one-dimensional condition and with a recently developed numerical technique for the solution of recirculating flows.Separation of the flow was induced in a 4ft length of 2 in. internal diameter nicrome tube of wall thickness 0.001 in. by means of a sudden enlargement of diameter at the entry of the tube. The tube was electrically heated by the passage of a current along its length. The first 25 in. of the tube was metered by thermocouples which gave the wall temperatures and from these the local heat transfer rates and Reynolds numbers up to 5 X 10 4 using air as the working fluid.

Heat transfer characteristics in a sudden expansion pipe equipped with swirl generators

“…3C shows a comparison for Nusselt number ratio (Nu x /Nu fd ) against X/H. There is modest agreement between our present data and the data of El-Shazly et al (2005) and Smyth (1974) in the region around the peak of Nusselt number with much good agreement in the redeveloping region after reattachment of the flow. The Nusselt number ratio starts off at approximately two times the fully developed Nusselt number, at entry to the test section, and then rise very steeply peaking at about 3.5 times the fully developed Nusselt number at a point around 7X/H along the test section from the step.…”

“…For the case of plain pipe expansions, all studies found considerable augmentation of the heat transfer levels with peaks occurring in the vicinity of the reattachment point (Holman, 1984;Zohir and Abdel Aziz, 2006;Krall and Sparrow, 1966;Baughn et al, 1984;El-Shazly et al, 2005;Incropera and Dewitt, 1981;Smyth, 1974). Krall and Sparrow (1966) used an electrically heated stainless steel tube downstream of the orifice, giving them an essentially constant wall heat flux boundary condition.…”

Heat Transfer to Separation Flow in Heat Exchangers

“…Smyth [14] conducted experiments to study the physical effects of separation and the associated reattachment and redevelopment, on the heat transfer characteristics of turbulent flow in pipes and compared the results of these flow conditions with the fully developed one-dimensional flow condition. He also compared results with a recently developed numerical technique for the solution of recirculation flows.…”