I am simulating a single flow in a 2D wall heated at one side with a constant heat flux at the bottom. The flow of the tube is in the laminar region. I needed to calculate the Nusselt No for the fully developed region in the fluent ansys.
If anyone having the knowledge of calculating the Nusselt No using FLUENT ANSYS or the information that can serve the purpose.
I will really appreciate the help.
It would be better to understand if you can provide a graphical description of your problem.
To calculate h or convection heat transfer coefficient, you need to calculate Nusselt number. Depending on the flow regime, you should set the appropriate Nusselt number for the analysis. Since you said that the flow regime is laminar, try a number between 1 and 10 by trial and error and compare the values of the wall temperature with the standard you have.
The Heat transfer coefficient (h) and Nusselt number (Nu) can be calculated using the FLUENT ANSYS solver by solving the energy equation. The energy equation takes into account the heat transfer due to conduction, radiation, convection, and turbulence. For laminar flow in a fully developed region, the Nusselt number can be determined by solving the energy equation at the wall, which is given by: Nu = h*L/k where h is the heat transfer coefficient, L is the characteristic length, and k is the thermal conductivity of the medium. The heat transfer coefficient can be calculated from the energy equation by solving for the convective and radiative terms. The convective term is given by: h = (T - Tw)/(T - Tinf) where T is the local temperature, Tw is the wall temperature, and Tinf is the free-stream temperature. The radiative term is given by: h = εσ(T^4 - Tinf^4)/(T - Tinf) where ε is the emissivity of the medium and σ is the Stefan-Boltzmann constant. The Nusselt number can then be calculated by solving the energy equation at the wall.
To calculate the heat transfer coefficient and Nusselt number for laminar flow in the fully developed region using FLUENT in ANSYS, you can follow these general steps:
1. Set up the geometry and mesh: Create the geometry of your system and generate a suitable mesh using ANSYS Meshing or any other meshing software. Ensure that the mesh is fine enough to capture the boundary layer and resolve the flow features adequately.
2. Define the fluid properties: Specify the fluid properties such as density, viscosity, and thermal conductivity in the FLUENT software. This information is required for accurate heat transfer calculations.
3. Define the boundary conditions: Set the appropriate boundary conditions for your problem, including the inlet velocity profile, temperature, and any other relevant parameters. Ensure that the flow is in the laminar regime and fully developed in the region of interest.
4. Define the wall conditions: Specify the wall conditions for the surfaces where heat transfer is taking place. This includes the wall material properties, temperature, and the heat transfer model to be used (e.g., constant wall temperature or constant heat flux).
5. Set up the solver settings: Choose the appropriate solver settings for your problem. Select the laminar flow model and set the convergence criteria for the solution.
6. Run the simulation: Start the simulation and allow it to converge to a steady-state solution. Monitor the convergence criteria, such as residuals, to ensure a reliable solution.
7. Post-process the results: Once the simulation is complete, post-process the results to extract the heat transfer coefficient and Nusselt number. FLUENT provides various tools and options for post-processing, including surface integrals and report generation.
8. Calculate the heat transfer coefficient: Use the surface integral option in FLUENT to calculate the heat transfer rate at the desired wall surface. Divide the heat transfer rate by the temperature difference between the wall and the bulk fluid to obtain the heat transfer coefficient.
9. Calculate the Nusselt number: Divide the calculated heat transfer coefficient by the thermal conductivity of the fluid to obtain the Nusselt number. The Nusselt number represents the convective heat transfer enhancement compared to pure conduction.
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