Shell and Tube Heat Exchanger with a spiral Baffle

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The problem simulates heat transfer inside a shell and tube heat exchanger with a spiral buffer.

Shell and Tube Heat Exchanger with a spiral Baffle, ANSYS Fluent CFD Simulation Training

The problem simulates heat transfer inside a shell and tube heat exchanger with a spiral buffer by ANSYS Fluent software. The heat exchanger is a device for transferring heat between two hot and cold fluids. The industry’s two most common heat exchangers are plate heat exchangers and shell and tube heat exchangers. The shell and tube heat exchangers consist of a cylindrical outer shell and inner tubes inside.

One of the cold or hot fluids passes through the space between the tubes and the outer shell, and the other fluid passes through the inner space of the inner tubes in the same direction or vice versa. One way to enhance the heat transfer process between two fluids is to use buffers inside the shell’s fluid flow path.

The use of buffers in the flow of fluid causes turbulence in the fluid flow through the shell and further contact of the fluid with the tubes, and as a result, heat transfer is enhanced; But on the other hand, it causes a pressure drop in the fluid as well as the deposition of fluid in the shell. Therefore, the use of helical baffle reduces the pressure drop and sedimentation inside the heat exchanger in addition to strengthening the heat transfer between the two fluids.

In the current model, the heat exchanger consists of seven internal tubes and a spiral buffer inside the shell. The flow of water with a flow rate of 0.5 kg.s-1 and a temperature of 300 K enters the shell from the shell inlet and is exchanged with tubes with a constant temperature of 450 K.

In fact, it is assumed that the cold flow passes through the shell and the hot flow through the inner tubes; But for simplicity, the model assumes that the temperature of the hot fluid flowing through the tubes during the process has a constant temperature value, which is assumed to be 450 K.

Shell and Tube HEX Geometry & Mesh

The present 3-D model is designed using Design Modeler software. The model is a shell and tube heat exchanger that includes an external shell and seven internal tubes inside. The diameter of the shell is 3 cm and its length is 60 cm. Inside the interior and between the shell and the tube, a spiral buffer is used. The following figure shows a view of the geometry.

The meshing of the model has been done using ANSYS Meshing software and the mesh type is unstructured. The element number is 1629340 and the accuracy of the cells in the areas adjacent to the wall of the tubes is higher. The following figure shows a view of the mesh.

CFD Simulation

To simulate the present problem, several assumptions are considered:

• The solver is pressure-based.
• The effect of the gravity on the fluid flow is 9.81 m.s-2 along the y-axis downward.

A summary of the steps for defining the problem and its solution is given in the following table:

 Models (shell and tube) k-epsilon Viscous model realizable k-epsilon model standard wall function near-wall treatment on Energy Boundary conditions (shell and tube) mass flow inlet Inlet 0.5 kg.s-1 mass flow rate 300 K temperature Pressure outlet Outlet 0 Pa gauge pressure wall Baffle’s wall stationary wall wall motion (shell and tube) coupled thermal condition Outer wall for shell stationary wall wall motion 0 W.m-2 heat flux wall Inner walls for tubes stationary wall wall motion 450 K temperature Solution Methods (shell and tube) Simple Â Pressure-velocity coupling Standard pressure Spatial discretization first-order upwind momentum first-order upwind turbulent kinetic energy first-order upwind turbulent dissipation rate first-order upwind energy Initialization (shell and tube) Standard Initialization method 0 Pa gauge pressure 0 m.s-1 x-velocity, z-velocity 0.7106586 m.s-1 y-velocity 300 K temperature

Shell and Tube Results

At the end of the solution process, two-dimensional and three-dimensional contours of pressure, temperature, and velocity, as well as two-dimensional and three-dimensional velocity vectors and path lines, are obtained.

2 reviews for Shell and Tube Heat Exchanger with a spiral Baffle

1. Barney Russel

How does this simulation take into account the impact of heat exchanger fouling on heat transfer?

• MR CFD Support

The simulation includes advanced models for heat exchanger fouling, which can significantly affect heat transfer performance. It can simulate the impact of factors such as fouling thickness, fouling thermal conductivity, and fouling resistance on heat transfer

2. Marie Wallace

Would you please tell me when do we use “Coupled” thermal condition in the wall boundaries?

• melika maysoori

Hi Marie. Sure ðŸ™‚ . If the wall is two-sided, i.e., a wall boundary is located between two areas of connection (fluid-fluid or fluid-solid), the problem of conjugated heat transfer is raised. In such a case, when the Mesh file is read by Fluent software, a virtual wall called Shadow is automatically assigned to each of the two-sided walls. For example, if the boundary of a Wall-1 is a double-sided wall. After calling in Fluent, the Wall-1-shadow virtual wall border is created, which corresponds precisely to the Wall-1 border, and each of these borders is connected to one of the two connection areas. In such conditions, different boundary conditions can be considered for the two walls, or by selecting the Coupled option, the heat transfer of the two walls is affected by each other and is in the form of a couple. The following describes how to define the thermal conditions for a double-sided wall in a coupled or separate manner.

If both sides of the wall are coupled, select the Coupled option (Coupled thermal condition appears only in the boundary condition of the double-walled walls). In this case, the definition of other parameters is unnecessary because Fluent software automatically calculates the heat transfer in the wall based on the values calculated in the elements adjacent to the wall. The material, thickness, and amount of heat production of the wall can be determined to calulate the thin walls. It is noteworthy that the definition of these parameters for a wall is automatically considered for its corresponding virtual wall.

3. Barbara

This tutorial helped me with my project.

• melika maysoori

You’re welcome. ðŸ™‚ If you need more training, you can refer to the rest of our related products, or contact us for private online training.

4. Ebba Jacobson

How does this simulation take into account the impact of the spiral buffer on heat transfer?

• MR CFD Support

The simulation includes advanced models for the spiral buffer, which can significantly enhance heat transfer in the heat exchanger. It can simulate the impact of factors such as buffer size, shape, and material on heat transfer performance.

5. Gilbert Cartwright

How does this simulation model the process of conduction in heat transfer?

• MR CFD Support

The simulation includes advanced models for conductive heat transfer, which is an important factor in heat exchangers. It can simulate the impact of factors such as material properties, temperature gradient, and contact area on conductive heat transfer.

6. Stefanie Ryan

Can this simulation be used to evaluate the impact of different buffer designs on heat transfer?

• MR CFD Support

Yes, the simulation can be adjusted to evaluate the impact of different buffer designs on heat transfer. This includes different buffer sizes, shapes, and materials.