Analysis of the conjugation effect during convective flow film boiling conditions in an eccentric annular test section Original Research Article

The objective of this investigation was to present a technique for estimating the conjugation effect on post-dryout heat transfer. To this aim, an experimental study was conducted to measure the conjugation effect on the post-dryout heat transfer using an internally heated eccentric annular test section (outside diameter (O.D.), 13.51 mm; inside diameter (I.D.), 11.54 mm). The experiments were carried out at 7 and 9 MPa with the mass flux varying from 2.0 to 5.0 Mg m−2 s−1 and the inlet vapour quality from 0.01 to 0.20. Five different minimum gap sizes between 0.06 and 1.92 mm were tested. The two-dimensional well temperature distribution on the inside surface of the heated tube was measured using a unique sliding thermocouple technique. A data reduction method was developed to determine the radial heat flux variation on the boiling surface from the temperature measurements. A numerical smoothing procedure was used to minimize the effect of the random temperature measurement error of the sliding thermocouple on the estimated radial heat flux variation. The results show that the conjugation effect can cause the local radial heat flux to deviate by as much as 17% from the average value.