Pressure Drop and Heat Transfer in a Duct With Triangular Cross Section

TL;DR: In this paper, local and average heat transfer coefficients and the temperatare field in the duct wall have been determined for the condition of constant heat generation per unit volume of the duct walls.

Abstract: Friction factors were measured for a duct whose cross section has the shape of an isosceles triangle witb a side ratio 5 to 1 in the fully developed now region ior laminar, transitional, and tarbulent conditions. In addition. local and average heat-transfer coefficients and the temperatare field in the duct wall have been determined for the condition of constant heat generation per unit volume of the duct walls. Friction factors in laminar flow agreed well with analytical predictions. In the turbulent flow range they were by 20 per cent lower than values calculated from relations for a round tube with the use of the "hydraulic diameter." Heat-transfer coefficients averaged over the circumference of the duct were only half as large as values calculated from round tube relations in the Reynolds number range from 4300 to 24,000. The measurements also revealed that thermal starting lengths were in excess of 100 diameters. In round tubes a length of 10 to 20 diame ters has been found sufficient to develop the temperature field. (auth)