Application of IR thermography for unsteady fluid-flow research

Tiit Koppel; Matti Lahdeniemi; Ari Ekholm

doi:10.1117/12.304712

26 March 1998 Application of IR thermography for unsteady fluid-flow research

Tiit Koppel, Matti Lahdeniemi, Ari Ekholm

Proceedings Volume 3361, Thermosense XX; (1998) https://doi.org/10.1117/12.304712
Event: Aerospace/Defense Sensing and Controls, 1998, Orlando, FL, United States

Abstract

In the recent years the IR thermography technique has been sued successfully as a new contactless instrument for gas and fluid flow research in pipes and on the surface of a flat plate. It is well known that most energy changes in the flow take place in the boundary layer. This is in turn important for the intensity of convective heat transfer in pipe flows and enables to measure processes connected with energy changes in the flow from outside the pipe. Series of measurements of suddenly accelerated and pulsating pipe flow were made at Satakunta Polytechnic, Technology Pori, Finland. The theoretical criterion describing the transition from laminar to turbulent regime is found depending on the critical thickness of the boundary layer of suddenly accelerated flow. At the moment of transition of the 'plug' type flow into turbulent flow, the velocities in the wall region diminish and this can be detected using the IR thermography from the wall temperature changes. the experimental results of the mean velocity development and transition criteria correspond to the theoretical calculations. The changes of the internal structure of the flow affect the convective heat transfer and this in turn influences the pipe wall temperature. IR thermography measures pipe wall temperature changes and consequently we can detect flow structure changes in the boundary layer in the accelerated and decelerated phase of the pulsating pipe flow.

Citation Download Citation

Tiit Koppel, Matti Lahdeniemi, and Ari Ekholm "Application of IR thermography for unsteady fluid-flow research", Proc. SPIE 3361, Thermosense XX, (26 March 1998); https://doi.org/10.1117/12.304712

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