What is the purpose of baffles in a heat exchanger?

• A. To support tubes and direct flow
• B. To decrease pressure drop
• C. To measure temperature
• D. To roughen flow

Answer: (A)

In a shell-and-tube heat exchanger, baffles are placed inside the shell to shape the flow and support the tubes. Their main job is to hold the tubes in place and direct the shell-side fluid to pass across the tube bundle rather than moving straight along the shell. This cross-flow path increases the contact between the fluid and the tube surfaces, which boosts heat transfer and helps distribute temperature more evenly. The baffles also provide structural support, helping prevent tube sagging and vibration.

Because guiding the flow across the tubes adds friction and creates a longer flow path, baffles typically increase, not decrease, the pressure drop. They do not measure temperature—that’s done by sensors—nor are they intended to “roughen” the flow; they create turbulence to enhance heat transfer, not to roughen the surface.