Single-pass SW/DW heat exchanger with double-tube sheets

Figure 2-4.—Single-pass SW/DW heat exchanger with double-tube sheets. Figure 2-5.—Two-pass SW/DW heat exchanger with single-tube sheets. Double-tube sheets are used at both ends of a tube bundle. A void space between the sheets prevents contamination of the distilled water and permits the monitoring of water loss due to tube leakage. You should be on the lookout to detect leakage at the “telltale drains,” which indicates a failure of a tube joint. The type of water leaking out indicates whether the failure is in the primary or secondary system. The telltale drains should never be plugged or capped off. A leak in one of the tubes shows up as a loss of water in the secondary side of the liquid-cooling sys- tem, because it operates at a higher pressure than the primary side. This is intentional, as it ensures that the distilled water is not contaminated with seawater when a leak develops in a heat exchanger. A double-pass heat exchanger is generally used when there is limitation on the installation of the heat 2-7