thermocompressors

Alex Meissner

I am trying to model a thermocompressor using Fluent 5. This device has two inlet streams and one out let. the first inlet is at a pressure of 165 psi and 360(f). This stream enters a converging-diverging nozzle, where it reaches sonic velocity. The second inlet is a 120-psi and 338(f). The high-pressure stream draws the low-pressure stream in and mixes. It is then discharged at some intermediate pressure and temperature. I have created one meshed volume and simulated it several times in Fluent. The velocities and pressures from the results are much higher than expected. Questions: Does Fluent know that the high-pressure stream reaches sonic velocity just given BC's? Why are the velocities and pressures higher than expected? And does anyone have suggestions on how to model two inlet streams and one outlet?