Implementation of liquid crystal thermography to determine wall temperatures and heat transfer coefficients in a tube-in-tube heat exchanger

摘要

Liquid crystal thermography was used in a water-operated concentric tube-in-tube heatexchanger to determine local annular heat transfer coefficients at the inlet region. Anannular diameter ratio of 0.54 was considered with the inlet and outlet orientatedperpendicularly to the axial flow direction. Both heated and cooled cases were consideredat annular Reynolds numbers ranging from 1000 to 13 800. Wall temperature distributionswere directly measured by means of a coating of thermo-chromic liquid crystals. Local heattransfer coefficients at the inlet were higher than those predicted by most correlations, butgood agreement was obtained with some literature.