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Flow boiling

Hi all,

New user here. I have NX Advanced, Thermal & Advanced Thermal, Flow & Advanced Flow. I am working on a particular problem, but having difficulty.Any suggestions / advice would be greatly appreciated.

Take the example of a tube running through a block of solid, hot material. Assume the application is a once-through boiling process at a pressure of about 45 barg, where the fluid is initially water (~20°C), then evaporates and eventually becomes superheated (~350°C) all in the same tube between the inlet and outlet. The heat source for the fluid is from the hot solid material surrounding the tube.

Can NX model this scenario (both steady-state, and transient with the flow rate being varied to maintain the outlet temperature as the heat from the heat source is depleted)? I am particularly looking to be able to indentify the point at which boiling commences (time and location) and also the point at which boiling is complete and superheating commences.

Can the software determine the mass fraction (steam quality) in the two-phase (boiling) region?

Thanks in anticipation,

Dave Reynolds.

Re: Flow boiling

Hi, Dave

We have recently supported a reseller in Australia to create a model that sounds all too close to be a coincidence. The 3D NX Flow solver does not support the superheated boiling of water yet. We are introducing the dual phase flow at NX 7.5.x as a first step to tackle this problem, but it will not do that explicitly right now.

However, you can treat this problem with a 1D pipe flow element by leveraging a user sub-routine in NX Advanced Thermal to tackle the phase change at high water pressure and control the outlet temperature to be 350 C with a PID controller. I have provided this to the Australian reseller.

If you have further questions on this topic, please don't hesitate to contact me directly at Perhaps you can ask your contact at the Australian reseller and we can all get on a conference call if needed.

Best Regards,