Review On Enhancement of Heat Exchanger by Mechanical Aids

The heat exchanger is an important device in almost all of the mechanical industries it is key element. Thus, many researchers in this area are working to improve the performance of the heat exchangers in terms of heat transfer rate. This paper is a review of passive augmentation techniques used in heat exchangers. The thermal performance behavior of tube in tube heat exchanger it is studied for wire coil inserts, twisted tape inserts and their combination. The research was done for constant/periodically varying wire coil pitch ratio. Some of them have varied 3 coil pitch ratios. The conical ring was also been tested. These inserts are tested individually and in combine form and results were compared. The Reynolds number is selected for allowing the inserts to be tested for different flow conditions from laminar, transient and turbulent. The new improved performance was found in the increasing order for inserts like wire coil, twisted tapes and conical inserts. Also, some of researchers have developed correlations for these inserts for Nusselt number as a function of Reynolds number.