I would almost guarantee that marine engineers have such data and probably for many hull shapes, and if they don’t for all hull shapes they could probably fairly easily do that with a little bit of the global warming research $ that’s floating around.

Also, the comment about surface water churn in highly traveled waters contributing to lower readings seems to make sense, in the same way that a hurricane leaves behind a trail of cooler water, but I would be cautious about jumping to a numeric conclusion on this without some analysis.

I am a retired merchant marine engineer. I made my living on merchant ships from 1966 to 1999, when I retired as Chief Engineer of a 32,000 SHP steam turbine powered container ship.

A ship moves through the water at between 12 knots and 22 knots. (Twelve knots for an old Liberty Ship from WWII, 22 knots fairly representative of new ships.) At even 12 knots, the speed is fast enough to cause turbulent flow of the sea water and thereby prevent a “warm” layer forming along the ship. In addition, very little of the ship is a significant heat source; only the area in way of the machinery spaces. Most of the ship is thermally inert cargo space that may be warmer or colder than the sea temperature. The main cooling water pump (Main Circulator) takes suction through the hull at a depth of 15 feet to 60 feet (depending on the ship) below the surface of the water. In addition, a Main Circulator will pump up to several thousand gallons per minute.

In short, the concept that the water would be heated by a measurable amount is far fetched at best. The statement indicates that assumptions were made about the measurement process and there was no meaningful investigation before these opinions were voiced.

Actually, there is cause for concern in using these numbers. Typically, either alcohol type bulb thermometers or bimetallic type thermometers were used. They were calibrated at the factory before they were installed, but never after that as long as the readings were “close enough”. It was not until the late ‘60s that thermo-electronic (e.g. RTD and Thermister) methods started to enter the fleet. It is to be expected that, particularly with the older readings, each one may be on the order of up to 10 degrees off, with a random distribution.

Regards,

Steamboat Jack

I served on aFletcher class destroyer. My memory is hazy, but I seem to recall an intake pipe about 18″ in diameter (though that may have been after it was split). The principal use of sea water was in the steam condensers.

More importantly it was located well below the waterline, at least sufficiently deep so that heavy weather would not expose the inlet.

I am not sure why sea water say 10′ in depth can be presumed to be the same temperature as water retrieved by a bucket on the surface.

REPLY: Your last line says it all, and I have plans to discuss that in part 3, and maybe part 4 if I have enough material.

REPLY: Thanks Rex, I had not looked in awhile. I’ll showcase this soon.