[tannh]

Hi everyone,

I am currently investigating an operational problem with the drain line of high pressure feedwater heater in power station. It vibrated with high amplitude during operation.

This drain line is from high pressure heater working at pressure 1.8 MPa, drains to deaerator at 0.6 MPa, there are bend, T-shape welds, gate type isolation valve, control valve.

I suppose there are flashing at some point along the pipe, because the problem arise when the heater deteriorate following by the rise of drain water temperature.

I would like to be suggested how to build a model to investigate the flashing potential, specific with openFoam.

I appreciate your recomendations.

[Martin_Sz]

To investigate the flashing potential in the drain line of a high-pressure feedwater heater using OpenFOAM, you can follow these steps:

1. **Define the Physical Model**:
- Start by defining the physical parameters of your system, such as the **geometry** of the drain line, including bends, T-shape welds, valves, etc.
- Specify the **operating conditions**, like the pressures at the heater (1.8 MPa) and the deaerator (0.6 MPa), and the temperature of the drain water.

2. **Select Appropriate OpenFOAM Solvers**:
- For flashing analysis, you might need to use a solver that can handle **two-phase flow** with phase change. The `interFoam` solver in OpenFOAM is designed for two-phase flow of immiscible fluids and might be suitable for your case³.
- If you're dealing with compressible flow, consider using `compressibleInterFoam` or `rhoCentralFoam` for more accurate results.

3. **Customize the Solver**:
- Modify the solver to include a **flashing model**, such as the Homogeneous Relaxation Model (HRM), which can predict the transition from liquid to vapor².
- Ensure that the solver can handle **choking** conditions, which occur when the flow reaches sonic conditions at the point of flashing.

4. **Set Up the Boundary Conditions**:
- Apply appropriate **boundary conditions** for pressure and temperature at the inlet and outlet of the drain line.
- Include any **heat transfer** effects that might contribute to the rise in drain water temperature.

5. **Mesh the Geometry**:
- Create a **mesh** that accurately represents the complex geometry of the drain line, paying special attention to areas where flashing is likely to occur.

6. **Run Simulations**:
- Perform simulations with varying parameters to understand the conditions under which flashing occurs.
- Analyze the results to identify the locations and conditions that lead to flashing.

7. **Validate the Model**:
- Compare the simulation results with **experimental data** or known behavior of the system to validate your model.
- Adjust the model as necessary to improve its accuracy.

Remember to consult the OpenFOAM user guide and relevant literature to ensure that your model and simulations are set up correctly. Additionally, participating in forums like CFD Online can provide valuable insights and recommendations from the community¹. Good luck with your investigation!