The influence of channel height on heat transfer enhancement of a co-angular type rectangular finned surface in narrow channel

M. D. Islam, K. Oyakawa, M. Yaga, I. Kubo

Research output: Contribution to journalArticlepeer-review

19 Scopus citations

Abstract

An experimental research was conducted to investigate the effect of channel height on heat transfer enhancement of a surface affixed with arrays (7 × 7) of short rectangular fins of a co-angular type pattern in channels. An infrared imaging system with the camera (TVS 8000) measured the temperature distributions to calculate the local heat transfer coefficients of the overall surface (fin base and endwall) of the representative fin regions. Heat transfer experiments were performed for a co-angular type fin pattern varying the channel to fin height ratio (Hd / Hf) from 2 to 5. Friction factors of the finned surfaces were calculated from pressure drop measurements. Relatively larger friction occurs for the smaller channel to fin height ratios and the friction factor slowly decreases with increasing Reynolds number. For the larger channel to fin height ratios, friction factor slowly increases with Reynolds number. The area averaged heat transfer decreases with increasing the channel to fin height ratio and channel aspect ratio, while heat transfer increases with the mainstream velocity. This is because, separation space between the channel wall and the fin top surface has a great influence on the phenomena of flow separated from the fin edge and vortex formation. At a smaller separation space, generated vortex is strongly reflected and vortex structure formation is adequately completed having full strength to interact with fins and endwall surface which leads to larger friction and contributes heat transfer enhancement. A detailed heat transfer analysis and iso-heat transfer coefficient contour gives a clear picture of the heat transfer characteristics of the overall surface. A relative performance graph indicates that the lowest channel to fin height ratio (Hd / Hf = 2) has the highest thermal performance out of the channels tested. In addition, significant thermal enhancement, 2.6-3 times the smooth surface value can be achieved at lower Reynolds numbers with a co-angular fin pattern in the channel.

Original languageBritish English
Pages (from-to)1639-1648
Number of pages10
JournalInternational Journal of Thermal Sciences
Volume48
Issue number8
DOIs
StatePublished - Aug 2009

Keywords

  • Co-angular fin pattern
  • Convective heat transfer
  • Heat transfer enhancement
  • Height influence
  • Infrared image system

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