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International Symposium on Imaging in Transport Processes.
May, 25-29, 1992, Athens, Greece

DOI: 10.1615/ICHMT.1992.IntSympImgTranspProc


ISBN Print: 978-1-56700-012-2

AN IMAGE PROCESSING TECHNIQUE FOR THE ANALYSIS OF THERMOTIC DISTRIBUTIONS UTILIZING LIQUID CRYSTALS

pages 195-202
DOI: 10.1615/ICHMT.1992.IntSympImgTranspProc.190
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摘要

One of the most time-consuming and difficult problems in heat transfer and fluid dynamics is to determine the velocity and/or the temperature field, especially when the temperatures depend on the fluid motion, as in convection flows. In three-dimensional (3D) convective flows the distribution of temperature can be very complex and it may be necessary to make measurements in a large number of locations, using numerous sensors, in order to resolve them. This problem can be ameliorated by using liquid crystals as sensors.
A number of previously reported investigations (see, for example, [5,7, 8]) have been concerned with the measurement of heat transfer using liquid crystals and an extensive review of liquid crystal thermographic applications is given by Yianneskis [9]. The information processed in such applications is the color displayed by the crystals. In order to obtain the temperature information appropriate image-acquisition software was developed to use together with the system described below.
Here we describe the methodology employed for the determination of temperature distributions on surfaces exposed to fluid flows using a liquid crystal thermographic technique. The system makes use of a digital image processing system developed at King's College London. The system enables accurate measurements of temperature distributions on surfaces of complex geometry to be performed for both steady-state and time-varying flow and heat transfer processes. The advantages of the technique and problems encountered during its use are discussed and the main considerations in the implementation of the color analysis for the transformation of the isochromes displayed by liquid crystals to isotherms are outlined. Characteristic results from the flow in a ventilated chamber indicating the capabilities of the method for temperature measurements are presented.

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