VARIABLE PROPERTY TURBULENT HEAT AND MOMENTUM TRANSFER FOR AIR IN A VERTICAL ROUNDED CORNER TRIANGULAR DUCT

Experimental data over a limited Reynolds number range are reported for local friction and heat-transfer coefficients with constant heat flux for turbulent air flow in an electrically heated vertical, rounded corner triangular tube at local wall to bulk temperature ratios from 1.1 to 2.1. The test section was in fact a rounded corner, three equal sided duct, with a ratio of the corner radius of curvature to hydraulic diameter of 0.15. The Inconel test section had a 100-diameter entry section and a 180-diameter heated section. Bulk Reynolds numbers ranged from 10900 to 37000 at the inlet. Correlation in terms of the wall-modified Reynolds number is presented for the local friction factors. Correlations are presented for the local heat-transfer coefficients in terms of the wall-to-bulk temperature ratio with bulk properties; and also directly in terms of the wall-modified Reynolds number. Both the friction and heat-transfer results are shown to be significantly affected by the influence of variable properties. A noticeable deviation of about 10-15 per cent from similar correlations for circular tubes is noted in both the friction and heat-transfer results. © 1968.