PRESSURE DROP AND HEAT TRANSFER IN A DUCT WITH TRIANGULAR CROSS-SECTION

摘要

Friction factors in laminar flow agreed well with analytical predictions. In the turbulent flow range they were by 20 per cent lower than values calcu¬lated 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 diameters has been found sufficient to develop the tempera¬ture field.