THERMAL CHARACTERISTICS OF A HEAT EXCHANGER TUBE FITTED WITH DIFFERENT PERIPHERALLY-CUT TWISTED TAPE INSERTS IN LAMINAR FLOW

Abstract

Experimental analyses of the alternation of clockwise and counterclockwise twisted tape (AT tape), and the AT tape in conjunction with three types of edge notches (V-cut, semicircle-cut, and rectangular-cut) on heat transfer and laminar flow friction characteristics in a uniform heat flux, circular copper tube using water as working fluid have been investigated in this paper. The investigations of plain tube were also carried out for comparison. The experiments covered a range of Reynolds numbers 500 ≤ Re ≤ 1800. The obtained results reveal that all of the present twisted tapes utilized in the experiment can significantly increase the Nusselt number and friction factor. The Nusselt number increases with increase in the Reynolds number while the friction factor shows an opposite trend for all cases. For a fixed Reynolds number, the Nusselt number and friction factor both increase with the reduction of edge notch area. Over the range investigated, the maximum value of performance evaluation criterion (PEC) achieved by the AT tape insert reached 1.54 at the Reynolds number equal to 1800. Finally, the empirical correlations for the Nusselt number, friction factor, and PEC were also determined. The predicted Nusselt number, friction factor, and PEC were, respectively, within ± 6.1%, ± 4.1%, and ± 3.3% deviation compared to the experimental data.