Condensation heat transfer and pressure drop characteristics of R-134a in horizontal smooth tubes and enhanced tubes fabricated by selective laser melting

This paper reports a study of condensation heat transfer and pressure drop of R134a inside four enhanced tubes and one plain tube fabricated by Selective Laser Melting (SLM). The results are compared to a plain commercial aluminum tube. The enhanced tubes consist of a tube with a metallic foam struc...

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Main Authors: Wang, X. W., Ho, Jin Yao, Leong, Kai Choong, Wong, Teck Neng
Other Authors: School of Mechanical and Aerospace Engineering
Format: Article
Language:English
Published: 2019
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Online Access:https://hdl.handle.net/10356/104480
http://hdl.handle.net/10220/50020
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Institution: Nanyang Technological University
Language: English
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spelling sg-ntu-dr.10356-1044802023-03-04T17:20:53Z Condensation heat transfer and pressure drop characteristics of R-134a in horizontal smooth tubes and enhanced tubes fabricated by selective laser melting Wang, X. W. Ho, Jin Yao Leong, Kai Choong Wong, Teck Neng School of Mechanical and Aerospace Engineering Singapore Centre for 3D Printing R134a Engineering::Mechanical engineering Condensation This paper reports a study of condensation heat transfer and pressure drop of R134a inside four enhanced tubes and one plain tube fabricated by Selective Laser Melting (SLM). The results are compared to a plain commercial aluminum tube. The enhanced tubes consist of a tube with a metallic foam structure, a tube with eight short circumferential pin fins, a tube with five long circumferential pin fins and a tube with five twisted pin fins. The experiments were conducted at mass fluxes from 50 to 150 kg/m2 s. Throughout the experiments, the inlet and outlet vapor qualities were maintained at 0.9 and 0.3, respectively. Two saturation pressures of 13.4 bar and 11.6 bar were investigated. The effects of fin height, refrigerant flow direction and mass flux on the heat transfer coefficient and pressure drop were studied. Our results show that for the wavy flow pattern, the saturation pressure, vapor quality, mass flux, refrigerant flow direction and fin structure have significant effects on the condensation heat transfer coefficient and pressure drop. At higher saturation pressures, the head impact on the fins with shorter fin height has a higher heat transfer coefficient than the back impact. For the longer and twisted fins, a reversed trend was observed. With an increase in the mass flux or a decrease in the saturation pressure, the difference in heat transfer coefficients between the head and back impact for the same tube structure reduces. The heat transfer coefficients of the metallic foam tubes are higher than that of the plain SLM tube with a large penalty of pressure drop. The eight-fin tubes yield higher efficiency indices in terms of heat transfer over pressure drop when compared to the other tubes. NRF (Natl Research Foundation, S’pore) Accepted version 2019-09-26T05:42:42Z 2019-12-06T21:33:44Z 2019-09-26T05:42:42Z 2019-12-06T21:33:44Z 2018 Journal Article Wang, X. W., Ho, J. Y., Leong, K. C., & Wong, T. N. (2018). Condensation heat transfer and pressure drop characteristics of R-134a in horizontal smooth tubes and enhanced tubes fabricated by selective laser melting. International Journal of Heat and Mass Transfer, 126, 949-962. doi:10.1016/j.ijheatmasstransfer.2018.04.163 0017-9310 https://hdl.handle.net/10356/104480 http://hdl.handle.net/10220/50020 10.1016/j.ijheatmasstransfer.2018.04.163 en International Journal of Heat and Mass Transfer © 2018 Elsevier Ltd. All rights reserved. This paper was published in International Journal of Heat and Mass Transfer and is made available with permission of Elsevier Ltd. 28 p. application/pdf
institution Nanyang Technological University
building NTU Library
continent Asia
country Singapore
Singapore
content_provider NTU Library
collection DR-NTU
language English
topic R134a
Engineering::Mechanical engineering
Condensation
spellingShingle R134a
Engineering::Mechanical engineering
Condensation
Wang, X. W.
Ho, Jin Yao
Leong, Kai Choong
Wong, Teck Neng
Condensation heat transfer and pressure drop characteristics of R-134a in horizontal smooth tubes and enhanced tubes fabricated by selective laser melting
description This paper reports a study of condensation heat transfer and pressure drop of R134a inside four enhanced tubes and one plain tube fabricated by Selective Laser Melting (SLM). The results are compared to a plain commercial aluminum tube. The enhanced tubes consist of a tube with a metallic foam structure, a tube with eight short circumferential pin fins, a tube with five long circumferential pin fins and a tube with five twisted pin fins. The experiments were conducted at mass fluxes from 50 to 150 kg/m2 s. Throughout the experiments, the inlet and outlet vapor qualities were maintained at 0.9 and 0.3, respectively. Two saturation pressures of 13.4 bar and 11.6 bar were investigated. The effects of fin height, refrigerant flow direction and mass flux on the heat transfer coefficient and pressure drop were studied. Our results show that for the wavy flow pattern, the saturation pressure, vapor quality, mass flux, refrigerant flow direction and fin structure have significant effects on the condensation heat transfer coefficient and pressure drop. At higher saturation pressures, the head impact on the fins with shorter fin height has a higher heat transfer coefficient than the back impact. For the longer and twisted fins, a reversed trend was observed. With an increase in the mass flux or a decrease in the saturation pressure, the difference in heat transfer coefficients between the head and back impact for the same tube structure reduces. The heat transfer coefficients of the metallic foam tubes are higher than that of the plain SLM tube with a large penalty of pressure drop. The eight-fin tubes yield higher efficiency indices in terms of heat transfer over pressure drop when compared to the other tubes.
author2 School of Mechanical and Aerospace Engineering
author_facet School of Mechanical and Aerospace Engineering
Wang, X. W.
Ho, Jin Yao
Leong, Kai Choong
Wong, Teck Neng
format Article
author Wang, X. W.
Ho, Jin Yao
Leong, Kai Choong
Wong, Teck Neng
author_sort Wang, X. W.
title Condensation heat transfer and pressure drop characteristics of R-134a in horizontal smooth tubes and enhanced tubes fabricated by selective laser melting
title_short Condensation heat transfer and pressure drop characteristics of R-134a in horizontal smooth tubes and enhanced tubes fabricated by selective laser melting
title_full Condensation heat transfer and pressure drop characteristics of R-134a in horizontal smooth tubes and enhanced tubes fabricated by selective laser melting
title_fullStr Condensation heat transfer and pressure drop characteristics of R-134a in horizontal smooth tubes and enhanced tubes fabricated by selective laser melting
title_full_unstemmed Condensation heat transfer and pressure drop characteristics of R-134a in horizontal smooth tubes and enhanced tubes fabricated by selective laser melting
title_sort condensation heat transfer and pressure drop characteristics of r-134a in horizontal smooth tubes and enhanced tubes fabricated by selective laser melting
publishDate 2019
url https://hdl.handle.net/10356/104480
http://hdl.handle.net/10220/50020
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