Review of Advances In Heat Transfer |

ABSTRACT:

Different heat transfer enhancers are reviewed. They are (a) fins and microfins, (b) porous media, (c) large particles suspensions, (d) Nano fluids, (e) phase-change devices, (f ) flexible seals, (g) flexible complex seals, (h) vortex generators, (i) protrusions, and (j) ultrahigh thermal conductivity composite materials. Most of heat transfer augmentation methods presented in the literature that assists fins and microfins in enhancing heat transfer are reviewed. Among these are using joint-fins, fin roots, fin networks,biconvections, permeable fins, porous fins, capsulated liquid metal fins, andhelical micro fins. It is found that not much agreement exists between works ofthe differentauthors regarding single phase heat transfer augmented with micro fins.However, too many works having sufficientagreements have been done in the case of two phase heat transfer augmented with microfins. With respect to nanofluids, there are still many conflicts among the published works about both heat transfer enhancement levels and the corresponding mechanisms of augmentations. The reasons be yond these conflicts are reviewed. In addition, this paper describes flow and heat transfer in porous media as a well-modeled passive enhancement method. It is found that there are very few works which dealt with heat transfer enhancements using systems supported with flexible/flexible-complex seals. Eventually, many recent works related to passive augmentations of heat transfer using vortex generators, protrusions, and ultra-high thermal conductivity composite materials are reviewed. Finally, theoretical enhancement factors along with many heat transfer correlations are presented in this paper for each enhancer..