Convective heat transfer coefficient

in a buried bitubular exchanger in transitory flow

T. Mnasri*, R. Ben Younes

Research Unit of Energy and Environment, Faculty of Sciences of Gafsa, 2112 Zarroug, Tunisia* Corresponding author. E-mail:

Received: 09 December 2006; revised version accepted: 17 May 2007



     This article presents the results of measurement of the local heat-transfer coefficient wall-fluid, in forced convection, in a bitubular exchanger. The exchanger wall is in permanent thermal contact with a semi-infinite medium such as the ground. The flux density measuring method disturbs the heat transfer between the coolant and the external medium.  Thus we employed a method based on the use of very fine cylindrical probes. We determined the evolution of the heat-transfer coefficient for various values of Reynolds number. We showed that the bitubular exchanger presents a maximum of heat transfer in a privileged area along its axis and this is according to Reynolds number. The obtained results agree with those obtained by different methods, for geometrical configurations of the same type.

Keywords:  Bitubular; Forced convection; Local heat-transfer coefficient; Exchanger; Transition.

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