Heat Transfer Intensification in a Heat Exchanger by Means of Twisted Tapes in Rib and Sawtooth Forms

Pasu Poonpakdee, Boonsong Samutpraphut, Chinaruk Thianpong, Suriya Chokphoemphun, Smith Eiamsa-ard (), Naoki Maruyama and Masafumi Hirota
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Pasu Poonpakdee: School of Engineering, King Mongkut’s Institute of Technology Ladkrabang, Bangkok 10520, Thailand
Boonsong Samutpraphut: Department of Mechanical Engineering, Mahanakorn University of Technology, Bangkok 10530, Thailand
Chinaruk Thianpong: School of Engineering, King Mongkut’s Institute of Technology Ladkrabang, Bangkok 10520, Thailand
Suriya Chokphoemphun: Department of Mechanical Engineering, Faculty of Industry and Technology, Rajamangala University of Technology Isan Sakonnakhon Campus, Sakonnakhon 47160, Thailand
Smith Eiamsa-ard: Department of Mechanical Engineering, Mahanakorn University of Technology, Bangkok 10530, Thailand
Naoki Maruyama: Division of Mechanical Engineering, Graduate School of Engineering, Mie University, Tsu 514-8507, Mie, Japan
Masafumi Hirota: Division of Mechanical Engineering, Graduate School of Engineering, Mie University, Tsu 514-8507, Mie, Japan

Energies, 2022, vol. 15, issue 23, 1-17

Abstract: This experimental study aimed to intensify the aerothermal performance index ( API ) in a round tube heat exchanger employing twisted tapes in rib and sawtooth forms (TTRSs) as swirl/vortex flow generators. The TTRSs have a constant twist ratio of 3.0, a constant rib pitch ratio ( p/e ) of 1.0, and six different sawtooth angles ( ? = 20°, 30°, 40°, 50°, 60°, and 70°). Experiments were carried out in an open flow using air as the working fluid for Reynolds numbers between 6000 and 20,000 in the current study, which was conducted in a heated tube under conditions of uniform wall heat flux. A typical twisted tape (TT) was also tested for comparison. The experimental results suggest that TTRSs yield Nusselt numbers ranging from 1.42 to 2.10 times of those of a plain tube. TTRSs with larger sawtooth angles ( ? ) offer superior heat transfer. The TTRSs with ? = 20°, 30°, 40°, 50°, 60°, and 70° respectively, enhance average Nusselt numbers by 158%, 162%, 166%, 172%, 180%, and 187% with average friction factors of 3.51, 3.55, 3.60, 3.67, 3.75 and 3.82 times higher than a plain tube. Additionally, TTRSs with sawtooth angles ( ? ) of 20°, 30°, 40°, 50°, 60°, and 70° offer APIs in the ranges of 0.99 to 1.19, 1.01 to 1.21, 1.03 to 1.26, 1.05 to 1.31, 1.07 to 1.42, and 1.09 to 1.48, respectively, which are higher than those of the typical twisted tape (TT) by around 5%, 7%, 11%, 16%, 25%, and 31%, respectively. This demonstrates that twisted tapes in rib and sawtooth form (TTRSs), with appropriate geometries, give a promising trade-off between enhanced heat transfer and an increased friction loss penalty.

Keywords: aerothermal performance index; friction factor; heat transfer enhancement; twisted tapes in rib and sawtooth form; swirling flow; vortex flow (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2022
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (1)

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