Control of jet impingement heat transfer in crossflow by using a rib

Experimental studies are carried out to investigate the jet impingement heat transfer in crossflow by liquid crystal thermography (LCT). The aim is to assess the possibility of controlling heat transfer by using a rib. The crossflow Reynolds number spans from 80,000 to 160,000 and the velocity ratio ranges from 1.0 to 2.8. The results show that the presence of rib can significantly modify the heat transfer pattern of impinging jet. For all the tested cases, the presence of rib makes the Nusselt number profiles across the stagnation point change from a classical bell-shaped profile to a plateau-like pattern, indicating the enhanced heat transfer region expands more as the rib is present. In particular, the presence of rib has a more pronounced effect on the enhancement of heat transfer at lower velocity ratios (R = 1.0 and R = 1.4). However, in such cases, the local heat transfer in the rib corner region deteriorates. At higher velocity ratios (R = 2.0 and R = 2.8), the presence of rib makes the heat transfer rate more uniform, but meanwhile, it is found that the impinging jet effect tends to be weaker. (C) 2011 Elsevier Ltd. All rights reserved.