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International Heat Transfer Conference 10

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

DETAILED MEASUREMENT OF LOCAL HEAT TRANSFER IN A SQUARE-CROSS-SECTION DUCT WITH A SHARP 180-DEG TURN

Akira Murata
Department of Mechanical Systems Engineering, Tokyo University of Agriculture and Technology, 2-24-16 Nakacho, Koganei, Tokyo 184-8588, Japan

Sadanari Mochizuki
Tokyo University of Agriculture and Technology, 2-24-16, Naka-cho, Koganei-shi, Tokyo 184, JAPAN

M. Fukunaga
Department of Mechanical Systems Engineering College of Engineering, Tokyo University of Agriculture and Technology, Japan

Abstract

Local heat transfer measurement was performed for a sharp 180-deg turn by measuring the wall temperatures at 146 points in the flow passage. In order to understand the flow structure, flow visualization was also conducted for laminar cases. In the heat transfer experiments, the airflow Reynolds number was varied from 1500 to 30000. It was disclosed that the averaged heat transfer increased in the downstream region from the sharp turn and the local heat transfer showed the considerable variation in the peripheral and streamwise directions. For the laminar case, the local lie at transfer characteristics were well explained by the flow behavior obtained through the flow visualization. For the turbulent cases, the abrupt change of heat transfer coefficient in the flow direction was observed on the outer and inner walls, which was caused by flow separation and its reattachment. The measurement in a round 180-deg turn was also performed to examine the effect of geometrical configuration of the turning section on the heat transfer. It was found that the qualitative characteristics of the heat transfer for the round-turn passage were almost similar to those for the sharp-turn passage, though the value of heat transfer coefficient was lower and its variation was smaller than the sharp-turn results.

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