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Old 11-12-2013, 01:18 PM   #144
RickB
Scraping Paint
 
City: Fort Lauderdale
Vessel Model: CHB 48 Zodiac YL 4.2
Join Date: Oct 2007
Posts: 3,804
Geez, I wonder why waterjet cutting machines don't produce great clouds of steam, or melt the crap out of fabrics, paper, or foam? Some of those buggers squeeze water up to around 100,000psi. Must be some kind of voodoo thing, do you think?

Hydraulic systems get hot because flowing oil through an orifice will increase the heat. It is a liquid with long molecules that release a lof of energy when they get disturbed, it's not a gas that expands by absorbing heat from outside or converting the work of compression into pressure and heat. If you have a 100 hp worth of hydraulic flow but only extract 50hp worth of work out of it, that other 50hp is going to be dissipated as heat.

Check out the temperature difference across a hydraulic reducing valve sometime ... the pressure drops drastically but it doesn't cool the fluid - quite the opposite, it gets hotter than a trawler forum argument with a pretender. Dropping pressure in a hydraulic system without doing work will produce heat. The pump only adds a tiny amount of heat from internal friction. The fluid does not compress enough to produce heat adiabatically.

Compressing a gas is a whole 'nuther process altogether and that is how a diesel engine works and why air gets hot when compressed by a turbocharger. Like many others with a little bit of the vocabulary, you need to attach the correct concept to the words if you want to make sense or try to explain how or why stuff works.

You've got quite a handly little IR thermometer if it can read an injector tube by itself. Tell you what I'll do, sometime in the next week or so I'll take an IR movie of fuel moving through a diesel injection pump so we can see how much it heats up.
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