Surface temperature measurement of a heated capillary tube by means of an infrared technique

We describe a method to measure the surface temperature of small-size devices by means of an infrared technique. The method is based on adjusting the temperature of the background to a level equal to the measured temperature of the object surface. The proposed method of infrared measurement was applied to investigate the average and local heat transfer coefficient in a small tube of inner diameter of 1.07 mm in laminar flow, in the range of Reynolds numbers 10 < Re < 400. It was shown that the heat transfer coefficient is much lower in the region of Reynolds numbers 10 < Re < 100 than that predicted theoretically for laminar flow in tubes of larger diameter.