Verification of the liquid crystal/heater technique for heat transfer measurement in confined flows

Heat transfer measurements using liquid crystals were carried out for fully developed turbulent flow in a horizontal pipe to verify the technique for confined flows using a well studied situation. Copper wire 90 diameters downstream of the entrance of the tube was wound around the tube for a length of 300 mm and produced the constant surface heat flux at the end of which the temperature profile was fully developed. It is found that the heat transfer distribution along the tube can be observed by noting the color distribution of the liquid crystal. The only significant heat loss is found to be that due to radiation. Excellent agreement is obtained with Engineering Sciences Data Unit (1977) data after accurate measurements of bulk temperature were made by measuring the center line temperature in the fully developed state and correcting for bulk temperature upstream.