CFD Simulation of a Shell & Tube Heat Exchanger in ANSYS Fluent
CFD simulation of a shell and tube heat exchanger lets you see exactly how heat moves between the hot and cold streams and where the design can be improved. In this free tutorial you will simulate a shell and tube heat exchanger with a baffle and multiple inlets and outlets in ANSYS Fluent, across three video parts covering geometry import, solver setup and results post-processing.
2. Part 1 — Geometry Import and Domain Setup
3. Part 2 — Solver Setup and Boundary Conditions
4. Part 3 — Results and Post-Processing
5. Evaluating Heat Exchanger Performance
6. Frequently Asked Questions
Introduction and Working Principle
A shell and tube heat exchanger transfers heat between two fluids: one flows through a bundle of tubes (the tube side) while the other flows around those tubes inside a cylindrical shell (the shell side). Heat conducts through the tube walls from the hotter stream to the cooler one. This CFD simulation models that process as a conjugate heat transfer problem, solving convection in both fluids and conduction in the solid tube walls simultaneously.
The baffle is the key feature of this model. It forces the shell-side fluid to weave across the tube bundle rather than sliding straight through, which raises velocity and turbulence near the tubes and boosts the convective heat transfer coefficient. The multiple inlets and outlets let you study more realistic manifold and flow-distribution effects than a single-port model allows.
Continuity: d(rho)/dt + div(rho u) = 0
Momentum: d(rho u)/dt + div(rho u u) = -grad(p) + div(tau) + rho g
Energy (fluid and solid, coupled): d(rho E)/dt + div(u(rho E + p)) = div(k_eff grad T) + S_h
Part 1 — Geometry Import and Domain Setup
The first video describes importing the complete geometry of the shell and tube heat exchanger with baffle and multiple inlets and outlets. The heat exchanger consists of the shell and the tube bundle, and the domain is separated into the shell-side fluid region, the tube-side fluid region and the solid tube walls. Clear named selections (shell_inlet, shell_outlet, tube_inlet, tube_outlet, tube_walls, baffle) make the boundary condition setup in Part 2 straightforward.
Part 2 — Solver Setup and Boundary Conditions
The second video shows the complete solver setting. It covers the turbulence model used for the analysis, the complete boundary conditions along with the material selection. The energy equation is enabled for heat transfer, materials are assigned to the shell-side fluid, the tube-side fluid and the solid tube walls, and inlet and outlet conditions are applied to both streams so the conjugate heat transfer can be solved.
| Setting | Typical choice |
|---|---|
| Solver | Pressure based, steady |
| Energy equation | On (conjugate heat transfer) |
| Turbulence model | k-epsilon realizable or k-omega SST |
| Shell and tube fluids | Water, oil or air as required |
| Tube solid | Copper, aluminium or steel |
| Inlets | Velocity or mass-flow inlet with temperature |
| Outlets | Pressure outlet |
Part 3 — Results and Post-Processing
The third video presents the results of the shell and tube heat exchanger with baffle and multiple inlets and outlets. The results are shown as contours, streamlines, animation and volume rendering. Temperature contours reveal how the fluid cools or heats along its path, velocity streamlines show how the baffle redirects the shell-side flow across the tube bundle, and the animation and volume rendering give a clear three-dimensional picture of the mixing and heat exchange.
Evaluating Heat Exchanger Performance
Once the solution converges, the shell and tube heat exchanger performance is judged from a few key numbers taken from surface reports on the inlet and outlet boundaries: the heat duty Q from the temperature rise of the cold stream, the effectiveness, the log mean temperature difference (LMTD), and the shell-side and tube-side pressure drop. A good design maximises heat transfer while keeping the pressure drop within acceptable limits. You can cross-check the CFD heat duty with the heat exchanger LMTD calculator and confirm the near-wall mesh with the y-plus value CFD calculator. If you are new to verification, work through the grid independence test tutorial first.
Frequently Asked Questions
What is conjugate heat transfer in a shell and tube heat exchanger CFD model?
Conjugate heat transfer means the simulation solves heat conduction in the solid tube walls together with convection in both the shell-side and tube-side fluids. The energy equation is coupled across the fluid-solid interface so heat passes from the hot fluid through the tube wall into the cold fluid.
Why does a shell and tube heat exchanger have baffles?
Baffles force the shell-side fluid to flow across the tube bundle in a cross-flow zig-zag path instead of straight along the shell. This raises the shell-side velocity and turbulence, increases the convective heat transfer coefficient and improves the overall heat exchange, at the cost of a higher pressure drop.
Which turbulence model is best for a heat exchanger simulation in ANSYS Fluent?
The k-epsilon realizable model with enhanced wall treatment is a common and robust choice for shell and tube heat exchangers. The k-omega SST model is preferred when the near-wall boundary layer and separation behind the baffles must be captured more accurately.
How do you evaluate heat exchanger performance from the CFD results?
Performance is evaluated from the inlet and outlet temperatures of both streams to find the heat duty Q, the effectiveness and the log mean temperature difference (LMTD), together with the shell-side and tube-side pressure drop. These metrics come directly from surface reports on the inlet and outlet boundaries.
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