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

Abstract

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