Heat Transfer Augmentation by Tube Inserts in Heat Exchangers

Experimental investigations have been carried out in the fin and tube crossflow heat exchangers to determine the characteristics of different augmentative tube inserts. Hot oil through the tubes and the flow of ambient air perpendicular to the bank of finned tubes are the heat exchanging fluids. A special feature is the study of the pierced twisted tape which promises to be a good augmentative insert among the available types. The comparison of the different inserts under laminar and transition conditions of flow, helps in selecting the type of insert for optimal performance. Empirical relations have been formulated for the various inserts studied. Performance evaluation Criterion (PEC) is applied and the predicated values agree closely with the experimental results. From the enhancements obtained with the different augmentative inserts and the analysis of the mode of heat transfer, the selection of economical material is possible.