Learning Forum

[mel123]

I am working with the evaporation model in Fluent to evaporate water in a flowing pipe and had a few questions regarding inputs and setup. First, since I am unsure of specific properties of the pipe, can I apply a known heat flux (say 500 W/m^2) to the fluid (with a wall thickness of 0) and expect the fluid to heat to evaporating conditions without further thermal conditions? And secondly, is there a way to specify that only the vapor phase can exit the system? I have an initial flowrate of water but was hoping to measure time/temperature/volume to evaporate the water. It seems as though some of the water is leaving the system before being evaporated which not only causes the evaporation rate to be incorrect but also cools the system by replenishing the water. Ideally, I would want the flowrate of liquid water to be 0 m/s until some has evaporated forcing only the vapor phase to leave the system and replenishing the system with more water.nnThank you for your help. n

[DrAmine]

You can even switch on shell conduction if you can want to account for pipe thickness and tangential heat transfer without having to resolve the solid pipe wall. Think about using Semi Mechanistic Boiling or you own code.nnI do not understand your second point.n

[mel123]

Thank you for the response. Sorry if my second question isn't clear. I would like for the evaporation process to be continuous and that as the liquid water is vaporized, more is replenished (i.e. there needs to be a flowrate into the pipe of only liquid water). However, I need to ensure that only vapor can exit on the other end of the pipe instead of a vapor and liquid mixture. Therefore, the liquid must remain in the pipe until it is vaporized. Is this more clear?.Thank you again.n

[DrAmine]

So you need to estimate the required heat flux to evapirate certain mass flow of subcooled water. Based on that you can start a parameter study.n