Jp. Meyer et al., Average boiling and condensation heat transfer coefficients of the zeotropic refrigerant mixture R22/R142b in a coaxial tube-in-tube heat exchanger, J HEAT TRAN, 122(1), 2000, pp. 186-188
Average boiling and condensation heat transfer coefficients were determined
experimentally for a coaxial tube-in-tube heat exchanger used in hot water
heat pumps. During manufacturing, the heat exchanger geometry used for the
experiments changed from round tubes to elliptical tubes as no spacers wer
e used to keep the inner tube from touching the outer tube. The refrigerant
used was two different mixtures of R22 with R142b in mass ratios of 80 per
cent/20 percent and 60 percent/40 percent. The results were compared to the
oretical results for straight tubes. It was concluded that the theoretical
modes do not predict the heat transfer coefficients very well in coaxial tu
be-in-tube heat exchangers where the annulus touches the inside of the oute
r tube.