A Shell and Tube Heat Exchanger is a very common device used in many industries to transfer heat from a hot fluid to a cold one. It has a bundle of tubes inside a large shell. To make the heat transfer better, plates called baffles are placed inside the shell. These baffles have a special baffle-cut that forces the fluid to flow in a zigzag pattern across the tubes. This creates more turbulence and mixing, which dramatically improves performance. A Shell and Tube Heat Exchanger CFD simulation is the best way to see this complex flow and understand how to design better baffles. This project simulates the flow on the shell side to analyze how the baffles improve heat transfer, based on the reference paper by Ozden and Tari [1].

• Reference [1]: Ozden, Ender, and Ilker Tari. “Shell side CFD analysis of a small shell-and-tube heat exchanger.” Energy conversion and management5 (2010): 1004-1014.

Figure 1: The 3D model of the shell and tube heat exchanger with six baffles [1].

Simulation Process: Modeling Shell-Side Flow and Heat Transfer

To begin our Shell and Tube Heat Exchanger fluent simulation, we first designed the 3D model. We focused only on the shell-side fluid volume, subtracting the space for the tubes and the baffles. This geometry was then filled with a high-quality mesh containing 1,471,826 tetrahedral cells. A fine mesh is needed to accurately capture the complex flow around the baffles.

Next, the physics were set up in ANSYS Fluent. Cold water enters the shell inlet at a velocity of 1 m/s. A constant high temperature of 450 K was applied to the walls of the tubes to represent the hot fluid flowing inside them. The goal is to see how much heat is transferred from these hot walls to the cold water as it flows through the shell. The k-epsilon turbulence model was used to handle the turbulent flow created by the baffles.

Post-processing: How Baffles Boost Thermal Performance of STHE

A deep analysis of the simulation results clearly shows how the baffle-cut design improves the heat exchanger’s performance. The velocity contours show that the baffles force the fluid to flow perpendicular to the tubes. This “cross-flow” is the key to good heat transfer. The baffles disturb the flow, creating turbulence and mixing, with local velocities reaching up to 2.882 m/s, which is much higher than the simple 1 m/s inlet speed. This turbulent, zigzag path prevents the fluid from taking an easy, straight route and ensures it makes good contact with the hot tube surfaces.

Figure 2: Streamlines colored by temperature, showing the zigzag flow path created by the baffle-cuts.

Furthermore, the temperature results provide the final proof of the design’s success. The temperature of the cold water steadily increases from 300 K at the inlet to a final outlet temperature of 332.77 K. This significant temperature rise of nearly 33 K is a direct result of the enhanced mixing caused by the baffles. The temperature streamlines in Figure 2 visually confirm this. We can see the fluid warming up as it is forced to move up and down between the baffles, effectively absorbing heat from the tubes. This quantitative result from our Shell and Tube Heat Exchanger with Baffle-cut CFD simulation confirms that the baffle arrangement is working perfectly, turning a simple shell into a highly efficient heat transfer device.