HEAT (MASS) TRANSFER CHARACTERISTICS

IN SERPENTINE FLOW PASSAGES

WITH A SHARP TURN

 

Masafumi Hirota,  Hideomi Fujita,  Hiroshi Nakayama

and  Ahmad Syuhada*

 

Department of Mechanical Engineering

 

(Received May 29, 2000 )

 

Abstract

 

Heat (mass) transfer characteristics for turbulent flow in rectangular cross-sectioned two-pass channels with a sharp turn have been examined experimentally using the naphthalene sublimation method.  It is well known that heat transfer characteristics in such channels are very complex, and they are influenced by many experimental parameters.  Among many possible parameters, main attention of this study has been directed to the influence of following four parameters on the heat (mass) transfer characteristics in the channel.  (i) Turn clearance, (ii) Reynolds number, (iii) Flow-inlet condition at the channel entrance, (iv) Inclination angle of the partition wall.  In this paper, detailed maps of the local Sherwood number distribution are presented, which make clear the complex and steep changes in the local heat/mass transfer rates in and after the sharp turn section and their dependency on these parameters.  Then, from a viewpoint of enhancing the mean heat transfer and improving the uniformity of the local heat transfer rates concurrently without an increase of pressure loss, the optimum channel geometry has been determined based on the experimental results.

 

KEYWORDS: forced convection heat transfer, heat exchanger, complex turbulent flow, flow separation and reattachment, secondary flow, naphthalene sublimation technique