Heat Transfer Enhancement of Tube in Tube Heat Exchanger Using Delta Winglet

Abstract

Delta winglets and inserts are used to improve the convective heat transfer coe cient in heat exchangers. Most important area of application of delta winglets and inserts are in enhancement of heat transfer in heat exchanger. Though ns are used to increase the heat transfer of heat exchanger but in this heat transfer is increased by increasing the contact surface and not by changing the nature of ow of uid. Geometric parameters and orientations of turbulant generators signi cantly alter the ow eld and hence the convective heat transfer coe cient. The presence of the delta winglet causes ow separation, reattachment and secondary recirculation zone on the downstream side of the delta winglet. However the presence of delta winglet causes pressure drop. In the present work experimental analysis for heat transfer in tube in tube heat exchanger with and without delta winglet is carried out for twelve di erent mass ow rate with three di erent uid combinations. The heat transfer augmentation in the form of Nusselt number variation is established for delta winglet. Thermal performance and pressure drop for delta winglet for Reynolds numbers range of 80 to 6500 at annulus side have been studied. Apart from delta winglets (V- shaped inserts), the experimental analysis are extended for the short (20 cm) and long (50 cm) insert. Results shows (with water as annulus side uid) that the average percentage increase in Nusselt number is 49%, 23%, and 38% for delta winglets, short insert and long insert respectively as compared to plain tube. It is also clear from the experimentation that, due to highest prandtle number ethylene glycol produce maximum heat transfer coe cient. It is observed that with Kerosene (Ethylene Glycol) as annulus side uid, percentage increase in Nusselt number is 40%, 16%, 31% (43%, 13%, 29%) for delta winglets, short insert, long insert respectively as compared to plain tube.