Thermo-Hydraulic Performance Analysis on the Effects of Truncated Twisted Tape Inserts in a Tube Heat Exchanger

Mehdi Ghalambaz,Wahiba Yaïci,Hossein Arasteh,Ramin Mashayekhi,Hafiz Muhammad Ali,Pouyan Talebizadehsardari

doi:10.3390/sym12101652

Abstract

This paper investigates the convective heat transfer in a heat exchanger equipped with twisted tape elements to examine effects of the twisted tape truncation percentage, pitch value, position and Reynolds number using 3D numerical simulation. A symmetric heat flux is applied around the tube as the studied heat exchanger. Based on the influences in both heat transfer enhancement and pressure drop, the performance evaluation criterion (PEC) is utilized. Inserting twisted tape elements and reducing the pitch value significantly augment the Nusselt number, friction coefficient and PEC number compared to the plain tube. For the best case with a Reynolds number of 1000, the average Nusselt number increases by almost 151%, which is the case of fully fitted twisted tape at a pitch value of L/4. Moreover, increasing the twisted tape truncation percentage reduces both heat transfer and pressure drop. Furthermore, the highest heat transfer rate is achieved when the truncated twisted tape is located at the entrance of the tube. Finally, it is concluded that for P = L, L/2, L/3 and L/4, the optimum cases from the viewpoint of energy conservation are twisted tapes with truncation percentages of 75, 50, 50 and 0%, in which the related PEC numbers at a Reynolds number of 1000 are almost equal to 1.08, 1.24, 1.4 and 1.76, respectively.

Highlights

Modifying heat transfer is a principal matter of concern for energy conservation and advantageous from an economic viewpoint
The reason is that the twisted tape inserts flow as a result of flow swirling, which improves the flow mixing, disturbs the thermal create secondary flow as a result of flow swirling, which improves the flow mixing, boundary layer and increases the heat transfer rate [51]
This paper investigated the laminar convection heat transfer in a tube equipped with twisted tape inserts

Summary

Introduction

Modifying heat transfer is a principal matter of concern for energy conservation and advantageous from an economic viewpoint. Symmetry 2020, 12, 1652 liquefaction [8], air dehumidification [9] and so forth, increasing the thermal performance is of vital importance To satisfy such a need, in the last two decades, researchers have proposed different passive techniques for heat transfer augmentation, including roughness elements [10], twisted tapes [11]. Man et al [18] experimentally investigated twisted tape inserts in an inner tube of a double pipe with clockwise and counterclockwise swirling directions. They showed that the heat exchanger thermal performance increases in the presence of twisted tape inserts, presenting a maximum value of 1.42 for the performance evaluation criterion (PEC) number. Lim et al [19]

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Results

Conclusion