The local heat transfer measurements in the cooling flow passage having both flat surface and semi-cylindrically grooved surface geometries inside the automobile disc brake were made. A uniform wall heat flux boundary condition on both surface geometries was created using gold film Intrex. Liquid crystal was used to measure the surface temperature. The experiments were made at Reynolds number (based on the hydraulic diameter of the rectangular duct) of Re=23,000, groove pitch-to-width (P/D) from 3 to 7, and groove depth-to-width (H/D) from 0.15 to 0.2. The results show that the magnitudes in the average Nusselt number on the grooved surface are maximum 92.8% higher than those on the flat surface without groove. A computer program utilizing the coupled FEM numerical technique that can predict the temperature distributions on the disc brake to analyze the thermal deformation has been developed.

The micro-encapsulated thermochromic liquid crystal has been used for the surface temperature measurement using its color change with heat. There are exciting new opportunities to apply this liquid crystal to the investigation of important and interesting heat transfer/fluid flow problems. The various techniques of using liquid crystal for the measurement of the local Nusselt numbers in very complex geometries are presented in this paper.

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