Question 39 3AE02 - Third Assistant Engineer (Alt)

The Correct Answer is A **Explanation for Option A (Segmental):** Segmental baffles are the most common and standard arrangement used in shell-and-tube heat exchangers, including marine-type units. They are highly effective because they force the shell-side fluid (typically seawater in marine applications) to flow back and forth across the tube bundle, creating high turbulence. This turbulent flow significantly increases the overall heat transfer coefficient ($U$) and promotes efficient heat exchange. They also provide mechanical support for the tubes, preventing sagging and vibration damage, which is crucial in dynamic marine environments. **Why the Other Options are Incorrect:** * **B) Doughnut:** Doughnut baffles (or orifice baffles) and doughnut-and-disk arrangements are generally used when very low shell-side pressure drop is required, or for specific fouling mitigation strategies. While they exist, they are specialized and much less common than segmental baffles in general industrial and marine applications where maximum thermal efficiency is the primary goal. * **C) Disc:** Disc baffles, often used in conjunction with doughnut baffles (disk-and-doughnut arrangement), create a more complex flow path. Like pure doughnut baffles, they are specialized designs. The combination of disc and doughnut baffles is complicated to manufacture and install and is not the "most common" standard choice for marine shell-and-tube heat exchangers. * **D) Solid:** Solid refers to a type of baffle plate without any major cuts or openings for flow redirection (e.e., a solid support plate, or a tube sheet). Baffles must have openings or cuts to redirect flow and induce turbulence across the tubes. A completely "solid" baffle would block the flow of the shell-side fluid entirely, rendering the heat exchanger inoperable.