Abstract:

:In order to analyze the heat transfer performance of a new type of heat exchanger, namely, the rectangular tube-bundle heat exchanger, the characteristics of heat transfer and flow resistance of two parallel converged-diverged plates inserted with twisted tapes were experimentally investigated, and the results were then compared with those of smooth plates as well as with those of the parallel converged-diverged plates without twisted tapes. It is found that, when the Reynolds number varies from 19000 to 44000, both the local Nusselt number and the friction factor decrease with the increase of the distance from the tape tail, while the efficiency index of heat transfer enhancement first increases and then decreases; and that, when the Reynolds number is 19071 and the distance from the tape tail is 140mm, the efficiency index reaches the maximum, which is 15% and 9% higher respectively than that of the smooth plates and that of the parallel converged-diverged plates without twisted tapes. It is thus concluded that the parallel converged-diverged plates inserted with twisted tapes greatly enhance the heat transfer.

Key words: compound heat transfer enhancement, rectangular tube-bundle heat exchanger, parallel convergeddiverged plate, twisted tape