THE EFFECT OF A 180° BEND ON HEAT TRANSFER TO WATER IN A TUBE
U bends in heat exchanger tubes may influence performance.
The effect of a 180° bend on the local heat-transfer coefficient between a tube and water flowing through it was investigated. Three bends of radius ratios 4:1, 8:1 and 22:1 at Re = 700 to 42 000 were used.
Curves of tube temperature or local heat-transfer coefficient against position along tube for turbulent, laminar and transitional flow are discussed. Particularly striking effects are obtained with laminar and transitional flow.
A design chart is given, from which it should be possible to make reasonably reliable predictions of results for other bends and Reynolds numbers.