Investigation of Overlapped Twisted Tapes Inserted in a Double-Pipe Heat Exchanger Using Two-Phase Nanofluid.

Mehdi Ghalambaz,Amir Keshmiri,Wahiba Yaïci,Pouyan Talebizadehsardari,Ramin Mashayekhi,Hossein Arasteh

doi:10.3390/nano10091656

Abstract

This study investigated the laminar convective heat transfer and fluid flow of Al2O3 nanofluid in a counter flow double-pipe heat exchanger equipped with overlapped twisted tape inserts in both inner and outer tubes. Two models of the same (co-swirling twisted tapes) and opposite (counter-swirling twisted tapes) angular directions for the stationary twisted tapes were considered. The computational fluid dynamic simulations were conducted through varying the design parameters, including the angular direction of twisted tape inserts, nanofluid volume concentration, and Reynolds number. It was found that inserting the overlapped twisted tapes in the heat exchanger significantly increases the thermal performance as well as the friction factor compared with the plain heat exchanger. The results indicate that models of co-swirling twisted tapes and counter-swirling twisted tapes increase the average Nusselt number by almost 35.2–66.2% and 42.1–68.7% over the Reynolds number ranging 250–1000, respectively. To assess the interplay between heat transfer enhancement and pressure loss penalty, the dimensionless number of performance evaluation criterion was calculated for all the captured configurations. Ultimately, the highest value of performance evaluation criterion is equal to 1.40 and 1.26 at inner and outer tubes at the Reynolds number of 1000 and the volume fraction of 3% in the case of counter-swirling twisted tapes model.

Highlights

In thermal engineering systems, convective heat transfer involves wide applications, including fuel cells [1], refrigeration [2], electronic device cooling [3], solar air collectors [4], and aerospace engineering [5]
It is visible that the fluid temperature undergoes more changes in lower Reynolds numbers due to the lower fluid velocity resulting in more time for fluids flowing through the inner and outer tubes from the heat exchanger’s inlet to outlet to exchange heat
Another point that is visible in this figure is that, at a given Reynolds number, the fluid outlet temperature in plain heat exchanger (PHE) is different compared with Co-STT and Counter-STT cases so that the twisted tape cases show a higher temperature difference between the heat exchanger inlet and outlet in comparison with the PHE

Summary

Introduction

Convective heat transfer involves wide applications, including fuel cells [1], refrigeration [2], electronic device cooling [3], solar air collectors [4], and aerospace engineering [5]. To increase the thermohydraulic performance of engineering systems, different techniques have been proposed, among which using twisted tape inserts has been widely used [6,7]. Applying additive nanoparticles to the base fluid to enhance the thermophysical properties of the working fluid has been considered as an effective technique to modify heat transfer [12,13]. On the other hand, combining different techniques to promote the thermohydraulic performance of thermal engineering systems as much as possible has been paid a lot of attention in recent years [20,21]

Objectives

Results

Conclusion