What defines a "closed-loop" system in ship engineering?

A "closed-loop" system in ship engineering is defined by its ability to contain a fluid within a defined circuit where that fluid is recirculated or reused. In such systems, there is no exchange of the working fluid with the external environment; instead, it is continuously cycled through various components of the system to perform its intended function, whether it involves cooling, lubrication, or another operational role. The primary advantage of closed-loop systems includes enhanced efficiency and reduced waste, as the fluid can maintain its properties over time without significant contamination or loss.

In contrast, the other scenarios described do not fulfill the characteristics of a closed-loop system. Systems that allow fluids to escape freely or contain open vents are typically classified as open-loop systems. These configurations involve direct interaction with the environment, leading to potential heat loss, contamination, or the need for constant replenishing of the fluid. Additionally, while monitoring systems for fluid levels are essential for maintaining proper function in any system (including closed-loop systems), they do not define the system as a closed-loop by themselves. They are more about oversight rather than the structural or operational characteristics of the fluid management system.