Experimental heat transfer and pressure drop study on typical, perforated, V-cut and U-cut twisted tapes in a helically corrugated heat exchanger

In this paper, heat transfer and friction factor are experimentally studied in a double pipe heat exchanger which has an inner corrugated tube filled with various categories of twisted tapes from conventional to modified types which include perforated, V-cut and U-cut types. The twist ratios are 3, 5 and 7, the hole diameter ratio are 0.11 and 0.33, the width and depth ratio of the cuts vary from 0.3 to 0.6 and the Reynolds number is changed from 5000 to 15,000 of turbulent regime. All of these factors lead to the performance of more than 350 experiments. The results of the main parameters on heat transfer and pressure drop show that the Nusselt number and friction factor for all cases of twisted tape corrugated tube are more than the empty corrugated tube. Also the Nusselt number and friction factor for corrugated tube equipped with modified twisted tapes are higher than typical tapes except those of perforated types which lead to lower Nusselt number and friction factor.