In many factories, machines use a device called a Shell and Tube Heat Exchanger to change the temperature of liquids. However, there is a big problem inside the tubes. The fluid near the wall moves very slowly and forms a “thermal boundary layer.” This layer acts like a blanket. It stops the heat from moving from the hot wall to the cold liquid. To fix this, engineers put small objects inside the tubes called Turbulators. A Blade-shape Turbulator is a special type that looks like a small wing or fan blade.

This project is a Blade-shape Turbulator CFD simulation designed to show you how these devices work. We use ANSYS Fluent to see the water moving inside the tube. By using this software, we can see how the blade cuts the water and mixes it. For more examples of thermal systems, please visit our Heat Exchangers tutorials. Our simulation follows the methods used in the research paper by Reference [1].

• Reference [1]: He, Li, and Peng Li. “Numerical investigation on double tube-pass shell-and-tube heat exchangers with different baffle configurations.” Applied thermal engineering 143 (2018): 561-569.

Figure 1: The 3D geometry of the tube with Blade-shape inserts used for the simulation.

Simulation Process: Modeling the Heat Exchanger in Fluent

To start this Blade-shape Turbulator Simulation, we first made the 3D model. We drew a long tube and placed the blade-shaped inserts inside it. This geometry is complex because of the small blades. Therefore, we made a mesh with 6,500,644 tetrahedral cells. A “cell” is a small piece of the model where the computer calculates the math. We need 6.5 million cells to see the tiny swirls of water around the blades clearly.

In the ANSYS Fluent setup, we turned on the Energy Equation. This tells the software to calculate temperature changes. We set the material of the tube to Steel. We set the boundary conditions to match a real heater. Hot water at 353 K flows outside the tube (in the shell). Cold water at 293 K enters the tube. The goal of this Turbulator in heat exchanger study is to see how much hotter the cold water gets when it leaves the tube.

Post-processing: Analysis of Swirling Flow and Heat Transfer

A real and deep analysis of the Blade-shape Turbulator CFD simulation results shows exactly how the physics of flow improves heating. The first thing we look at is the velocity contour (speed of the water). In a normal tube without inserts, water flows in straight lines. The water in the middle is fast, but the water near the wall is slow. This slow water stops heat transfer. But with the Blade-shape Turbulator, the flow changes completely. The velocity contour shows that the blades block the straight path of the water. This forces the water to speed up and flow around the blades. Behind every blade, we see a wake zone or a swirl. These are called vortices. These vortices act like small spoons that stir the water. They push the cold water from the middle of the tube to the hot walls, and they pull the hot water from the walls to the middle. This mixing destroys the “blanket” layer that stops heat.

The temperature contour confirms that this mixing works very well. We can compare the results of this Heat exchanger CFD simulation with a “Clean Tube” (a tube with no turbulators). In the Clean Tube simulation, the water leaves the outlet at 314.73 K. This is a small increase. However, in our Blade-shape Turbulator fluent simulation, the water is mixed much better. The data shows the outlet temperature is 318.15 K. This is a difference of 3.42 K. This number is very important. It proves that the swirling flow created by the blades adds more heat to the water. The uniform colors in the temperature contour show that the hot and cold water are mixed thoroughly. This deep analysis proves that the shape of the blade uses the energy of the flow to increase the efficiency of the heat exchanger significantly.

Figure 2: Velocity streamlines and temperature contours showing the mixing effect.

Key Takeaways & FAQ

• Q: What is a thermal boundary layer?
  • A: It is a thin layer of slow fluid near the tube wall. In this Blade-shape Turbulator CFD simulation, we see that this layer stops heat transfer. The turbulators are designed to break this layer.
• Q: How much does the turbulator help?
  • A: The data is clear. The clean tube heats water to 314.73 K, but the turbulator tube heats it to 318.15 K. This means the turbulator adds an extra 3.42 K of heat.
• Q: Why do we need 6.5 million cells?
  • A: The Blade-shape Turbulator ANSYS fluent model has small, curved blades. We need a fine mesh (many small cells) to calculate the complex swirling flow and vortices accurately around these small shapes.