Experimental Study on Heat Transfer Augmentation for High Heat Flux Removal in Rib-Roughened Narrow Channels

Abstract

Frictional pressure drop and heat transfer performance in a very narrow rectangular channel having one-sided constant heat flux and repeated-ribs were studied experimentally for turbulent water flows. Their empirical correlations were derived for designing target cooling channels to remove high heat flux generated at target plates in a high-intensity proton accelerator system. The rib pitch-to-height ratios (p/k) were 10 and 20 while holding the rib height constant at 0.2mm the Reynolds number (Re) from 2,400 to 98,500 under different channel heights (H) of 1.2 mm and 3.2 mm, the rib height-to-channel equivalent diameter ratio (k/D_e ) of 0.088 and 0.036, respectively. The results show that the rib-roughened surface augments heat transfer by about 2–2.5 times compared with the smooth surface at the expense of around 2.5 times higher frictional pressure drop under a range of Re=8,000-to-30,000 at p/k=10, and H=1.2mm. Experimental results of channel height, H=1.2mm show slightly higher heat transfer and friction factor performance than that of the channel height, H=3.2 mm.

KEYWORDS:

• pressure drop
• heat transfer
• augmentation
• narrow channel
• repeated ribs
• empirical correlation
• heat flux
• target plate
• pressure dependence