Heat transfer from in-line and perpendicular arrangements of cylinders in steady and pulsating crossflow

Abstract

An investigation was conducted to determine the effect of organized flow pulsations on mean heat transfer from a single cylinder, in-line arrangements and perpendicular arrangements of cylinders. Pulsation frequencies of up to twice the natural vortex shedding frequency and zero to peak. amplitudes as high as 36 percent were used. Pulsations were sinusoidal with at least 93 percent of the power at the fundamental frequency. Turbulence levels (Tu=0.5 percent) were not altered by the addition of unsteady flow. Reynolds number ranged from 23,000<Re<49,000. Results for heat transfer on the front and back of the cylinder are given for a constant wall temperature boundary condition. Heat transfer measurements were made by applying a heat balance to a thick walled copper tube divided into four individually heated segments with guard. heaters located at each end.

Mean heat transfer was found to increase for all three arrangements when organized flow pulsations were applied. For a single cylinder and for perpendicular arrangements, heat transfer increases were found primarily on the back of the cylinder. For in-line arrangements, increases occurred mostly on the front of the cylinder. for the range of pitch ratio most useful to heat exchanger design, in-line arrangements were found to have a higher Nusselt number than perpendicular arrangements.