EXPERIMENTAL INVESTIGATION OF USING NEW SHAPE AUGMENTATIONS FOR ENHANCING HEAT TRANSFER IN HEAT EXCHANGERS

Abstract

The present investigation aims to study experimentally the effect of using basket twisted bars as a new shape of turbulators in order to achieve better heat transfer inside tube heat exchangers. In this study, air is used as a working fluid with six different values of flow rates (Reynolds number values vary from 6000 to 13500), while the value of heat flux is kept constant in this investigation. In addition, the effect of spacing ratio (SR( between these turbulators is taken into account. Therefore, 3, 4 and 5 pieces of these turbulators are distributed along the test section during experiments. The results show that the heat transfer rate for all cases tends to increase with rising Reynolds number value, while the friction factor shows downward behavior with the same Reynolds number value. In addition, it is found that (SR=4.2) gives maximum heat transfer rate with 115.9 % above plain tube case. Friction factor values increase by 313%, 235% and 193% for SR= 4.2, 6.4 and 11 respectively comparing with plain tube). The enhancement efficiency also increases when inserting baskets twisted bars with rates 127.5 %, 134.3 % and 139.8 % for SR= 11, 6.4 and 4.2 respectively.