14. Other aspects of Transport Phenomena

This study presents a new method of the surface temperature measurement by using thermochromic liquid crystals (TLCs) and digital camera sensitivity in irradiation of specific wavelengths near the blue. In this method, the surface temperature of the planar copper plate was measured by using the TLC sheet which the range of color change was 10-20℃. The temperature of the copper plate was controlled by a water-jacket under it. In order to clarify the wavelength suitable for this method, two different wavelengths, i.e., 405 nm and 440 nm, were irradiated to the analyte surface. The scattered light intensity from the TLC sheet corresponding to the surface temperature was obtained as RGB values by images taken with a 14-bit digital color camera. To reduce the effects of image noise, we used a median filter after averaging at each pixel of 100 images as preprocessing. Two methods were used to calculate the temperature: one using relative brightness values and the other using HS values after HSV transformation from RBG values. The uncertainty of the measured temperature was also analysed. In the case of 405nm, the measurable temperature range was wide to 39℃ (10-49℃), the reliable temperature range and average temperature resolution under temperature measurement uncertainty of 0.2℃ were 25℃ (10-35℃) and 0.004℃, respectively. There was no significant difference between the methods using relative brightness values and HS values. In the case of 440nm, the camera exposure time could be reduced to 1/40 of that of 405nm, but the uncertainty results were similar. In addition, it was also found that the practical measurable temperature range was slightly narrower than the 405 nm case. As a result, it was revealed that when focusing on the measurable temperature range, it was better to use an irradiation light wavelength of 405 nm.

Prof.

Koichi ICHIMIYA

Corresponding author