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International Heat Transfer Conference 9

ISSN: 2377-424X (online)
ISSN: 2377-4371 (flashdrive)

HEAT TRANSFER CHARACTERISTICS OF LAMINAR BOUNDARY LAYERS IN THE PRESENCE OF VORTEX GENERATIONS

Jurandir Itizo Yanagihara
Department of Mechanical Engineering University of Sao Paulo Av. Prof. Mello Moraes, 2231 Sao Paulo, SP - 05508-900 Brazil

Kahoru Torii
Department of Mechanical Engineering and Materials Science, Yokohama National University, Yokohama 240, Japan

DOI: 10.1615/IHTC9.890
pages 323-328

Abstract

The influence of longitudinal vortices just downstream of half-delta wing vortex generators on heat transfer of laminar boundary layers was investigated. The local heat transfer coefficients and the mean and fluctuation component of velocity were measured. A substantial increase in the heat transfer was noticed, with a maximum improvement of the heat transfer coefficient of 80% for single vortex generators and 110% for pairs, in regions where the laminar structure was clearly predominant. It was observed that a single vortex generator disturbs the flow so that it creates two peaks of the heat transfer coefficients in the spanwise direction, each one associated with two different vortices. It was found that the stronger the vortex, the higher the heat transfer enhancement. In the case of vortex generator's pair, it was observed that for pairs whose common flow is downward, the smaller the distance between generators the higher the heat transfer coefficient. From this experimental work, some considerations about how to set a vortex generators array in heat exchangers could be pointed out.

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