Paper presented to the 10th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Florida, 14-16 July 2014.
In this paper the wall surface temperature distributions
at the inlet regions of a tube-in-tube counter flow heat
exchanger were investigated by making use of Liquid
Crystal Thermography (LCT). With flow not being fully
developed at the inlet region it is difficult to predict the
heat transfer coefficient and the appropriate wall
temperature on the inner tube under different flow
conditions. In this study water was considered in the
annulus in the turbulent flow with annular Reynolds
numbers of 1 000, 5 000 and 10 000. Local annular heat
transfer coefficients were determined from the measured
wall temperature profiles and the derived local annular
bulk fluid temperatures based on the measured coupled
local heat transfer rate in the inner tube. It was found that
Liquid Crystal Thermography allowed for the
measurement of the average wall temperature which could
vary significantly in the inlet region. It was also found that
the local heat transfer coefficients varied within a large
extent. For the particular heat exchanger under
investigation here which had annular diameters of 36 mm
and 19.5 mm, heat transfer coefficients reached a
maximum from 150 mm onwards after the inlet.
