🔍 Key Concepts

• Follow the direction of fresh water flow in the diagram from the engine outlet, through the coolers, and back to the engine inlet. • Understand that a heat exchanger removes heat from the fresh water, while the lube oil cooler can add some heat back into the fresh water. • Consider what the thermostatic control valve is doing during normal operation (regulating jacket water temperature by mixing cooled and bypassed water).

💭 Think About

• Starting at the point where fresh water leaves the engine (its hottest point), in what order does it pass the thermostatic valve, the RW/FW heat exchanger, and the lube oil cooler? • After passing through the RW/FW heat exchanger, is the fresh water hotter or cooler than it was going in? How about after it passes the lube oil cooler? • Which of the labeled locations (A–D) is upstream of any cooling devices, and which are downstream of one or more cooling stages?

✅ Before You Answer

• Verify the flow arrows on the illustration so you’re certain which way the fresh water is moving. • Identify clearly which component is the raw water/fresh water heat exchanger and which is the lube oil cooler, then match them to choices A–D. • Make sure the point you pick is located before the major cooling of the fresh water, not after it has been cooled and possibly reheated.