Temperature Measurement Technique by Liquid Crystal Thermometry Considering the Effect of Viewing Angle and Its Application to Thermal Convection Phenomenon.

Abstract

Field temperature measurement technique with encapsulated liquid crystal particles suspended in a liquid has been investigated considering the viewing angle effect on the color to temperature transformation. Two calibration techniques are studied, one is a neural network and the other is a spline fitting technique, where the calibration points are distributed over the image plane in order to consider the viewing angle effect. The calibration study is carried out with uniform temperature field image captured at various temperatures. It is found that the calibration error due to the viewing angle variation is reduced with an increase in the number of calibration points and by the introduction of smoothing technique. It is found that the spline fitting technique is superior to the neural network technique considering the evaluated temperature error and computing time. The spline fitting technique is applied to the temperature measurement of thermal convection over a heated surface and the thermal structures generated near the top and bottom boundaries are discussed.