A STUDY OF MASS LOADING LIMITS IN SPRAY DESUPERHEATING

An analytical expression is developed for the mass loading limit, defined as the limit beyond which liquid is unable to be vaporized in a general desuperheating system. This limit is subsequently compared to predictions originating from 3D numerical simulations based on a Lagrangian-Eulerian framework in combination with a RANS treatment for the vapor phase. The computations show that even for cases having much smaller mass loadings than the theoretical limit yield significant accumulation of liquid along the walls. Furthermore, the numerical findings presented in terms of streamwise profiles of mean droplet diameter, average vapor temperature, vapor-droplet slip velocity, and liquid mass show that the desuperheating process can be described as taking place in two distinct zones. In the first zone, located in the near-field, the flow process is characterized by vigorous liquid atomization and significant exchanges of mass, momentum, and energy between the liquid and vapor phases. In the second zone, which resides beyond the near-field, the desuperheating process displays a significantly reduced degree of vaporization, a near-equilibration of phasic velocities, and a milder change in the vapor temperature along the streamwise direction.