What cooling method is used for stern tube bearings?

The correct answer is seawater, which is used as a cooling method for stern tube bearings primarily because it is abundant and readily available in marine environments. Stern tube bearings are located in the ship's hull, where the propeller shaft passes through, and they play a crucial role in supporting and allowing the shaft to rotate smoothly.

Using seawater for cooling helps to dissipate heat generated from friction as the stern tube bearings operate. This cooling is vital to maintaining the integrity and performance of the bearings, as excessive heat can lead to premature wear or failure.

In addition to being effective for heat transfer, seawater is also environmentally consistent with the operations of a vessel. This method allows for efficient heat management without the need for complex cooling systems that would require additional resources or fuel.

Other cooling methods, such as oil cooling systems or air ventilation, may have specific applications but are less common in the context of stern tube bearings compared to using seawater, primarily due to factors like availability, efficiency, and the nature of the marine environment.