We used a tunable diode laser absorption spectrometer and a static-pressure probe to follow changes in temperature, vapor-phase concentration of D2O, and static pressure during condensation in a supersonic nozzle. Using the measured static-pressure ratio p/p(0) and the mass fraction of the condensate g as inputs to the diabatic flow equations, we determined the area ratio (A/A*)(Wet) and the corresponding centerline temperature of the flow during condensation. From (A/A*)(Wet) we determined the boundary-layer displacement thickness during condensation (delta(#))(Wet). We found that (delta(#))(Wet) first increases relative to the value of delta(#) in a dry expansion (delta(#))(Dry) before becoming distinctly smaller than (delta(#))(Dry) downstream of the condensation region. After correcting the temperature gradient across the boundary layers, the temperature determined from p/p(0) and g agreed with the temperature determined by the laser-absorption measurements within our experimental error (+/- 2 K), except when condensation occurred too close to the throat. The agreement between the two temperature measurements let us draw the following two conclusions. First, the differences in the temperature and mole fraction of D2O determined by the two experimental techniques, first observed in our previous study [P. Paci, Y. Zvinevich, S. Tanimura, B. E. Wyslouzil, M. Zahniser, J. Shorter, D. Nelson, and B. McManus, J. Chem. Phys. 121, 9964 (2004)], can be explained sufficiently by changes in delta(#) caused by the condensation of D2O, except when the phase transition occurs too close to the throat. Second, the extrapolation of the equation, which expresses the temperature dependence of the heat of vaporization of bulk D2O liquid, is a good estimate of the heat of condensation of supercooled D2O down to 210 K. (c) 2005 American Institute of Physics.
作者
我是这篇论文的作者
点击您的名字以认领此论文并将其添加到您的个人资料中。
推荐
暂无数据