NUMERICAL-SIMULATION AND LASER HOLOGRAPHIC STUDY ON THERMAL-DIFFUSIONIN COUNTERFLOW WITH DIFFERENT TEMPERATURES

This paper presents a numerical simulation and a laser holographic int erferometric study on thermal diffusion characteristics of combined fo rced and free heat convection in a counterflow with different temperat ures. The purpose of this paper is to make clear the characteristics o f a direct mixing heat exchanger for advanced energy conversion. In th e numerical study, the Bow patterns and isotherms for both adiabatic a nd non-adiabatic wall conditions are simulated in two-dimensional fiel ds over a wide range of the Reynolds number and Grashof number for ste ady and unsteady, laminar and turbulent hows. Real time holographic in terferometry is applied to visualize the isotherms for the simulated f low fields and to build a new concept of practical heat exchanger desi gn. In evaluating non stationary interferograms, the time averaged hea t flow rate is introduced and the thermal diffusion effect is discusse d. As the result, thermal diffusion at the mixing interface of counter flows can be well characterized. (C) 1997 Elsevier Science Ltd.