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research-article

Numerical Study of Heat Transfer Enhancement of Roll-to-roll Microchannel Heat Exchangers

[+] Author and Article Information
Heng Wang

Research Engineer, Department of Mechanical Engineering, National University of Singapore, Singapore
henry.617@hotmail.com

Samuel D. Marshall

Research Fellow, Department of Mechanical Engineering, National University of Singapore, Singapore
mpesdm@nus.edu.sg

Rerngchai Arayanarakool

Research Fellow, Department of Mechanical Engineering, National University of Singapore, Singapore
mperar@nus.edu.sg

Lakshmi Balasubramaniam

Research Associate, Department of Mechanical Engineering, National University of Singapore, Singapore
Bala.lakshmi02@gmail.com

Xin Jin

Associate Professor, School of Mechanical Engineering, Beijing Institute of Technology, Beijing, China
goldking@bit.edu.cn

Poh Seng Lee

Associate Professor, Department of Mechanical Engineering, National University of Singapore, Singapore
pohseng@nus.edu.sg

Peter C. Y. Chen

Associate Professor, Department of Mechanical Engineering, National University of Singapore, Singapore
mpechenp@nus.edu.sg

1Corresponding author.

ASME doi:10.1115/1.4038910 History: Received September 14, 2017; Revised December 12, 2017

Abstract

In this paper, the heat transfer performance of two roll-to-roll microchannel heat exchangers in the shape of square cross-section with the side length ranged from 0.2 mm to 0.5 mm are investigated via numerical studies. To assess the heat transfer enhancements, equivalent straight channel heat exchangers are also researched numerically as comparisons. For roll-to-roll devices, numerical studies demonstrated that there were two reasons for heat transfer enhancement. Firstly, inside the microchannel, when the average Dean Number was greater than around 10, Dean Vortices started to form within the roll-to-roll microchannels, enhancing the convective heat transfer between channels. Secondly, the compact roll-to- roll structure of the heat exchangers increased the heat transfer areas compared with straight microchannel equivalents, and thus promoted the conductive heat transfer. Numerical simulations noted both higher Nusselt Numbers and higher Thermal Performance Factors of roll-to-roll microchannel heat exchangers than the equivalent straight microchannels, and were employed to optimize both the microchannel cross-section dimension and the wall thickness between channels. In addition, this study also calculated the swirling strength and the heat transfer area to characterize the convective heat transfer and conductive heat transfer respectively, and made a comparison between two roll-to-roll microchannel heat exchanger designs.

Copyright (c) 2017 by ASME
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