An Experimental Study of Air Flow and Heat Transfer over in–Line Flat Tube Bank

Abstract

An experimental study was made to investigate heat transfer and air flow around the flat tubes of in-line flat tube banks with laminar forced convection. Measurements were conducted for sixteen tubes in the flow direction; four rows of four tubes, three air velocities (0.6, 0.8 and 1.0 m/s) and Reynolds numbers ReDh = 527, 703 and 880, where Dh is the hydraulic diameter of the tube. The total heat flux supplied in all the tubes was 968, 2259 and 3630 W/m2 , respectively. The study results indicate that the average Nusselt number of all the flat tubes increased by 23.7%–36.7% with Reynolds numbers varying from 527 to 880 with fixed heat flux; also the average Nusselt number increased by 11.78%–23.75% at varying heat fluxes of 968, 2259 and 3630 W/m2 , respectively at Reynolds number Re = 703. In addition, the pressure drop decreased with the increase of Reynolds number. The Nusselt number–Reynolds number  correlation was found to be Nu = C₁.Re^C2 and the correlation yielded good predictions of the measured data with the mean error R
2 = 99.2%.