RE: [SG,DS] Power Armour Weapon

It's a matter of scale.  Engines generate a constant, relatively low
amount of heat.  Plus it has the mass of several hundred pounds of
engine block to soak up and distribute the heat, plus the mass of the
radiator and fluid.  This is combined with dozens of square feet of
radiating surface on the radiator (all those skinny fins). 

Comparison numbers - 1 gram of gasoline burns for 11.5 calories of
energy.  1 gram of black powder propellent burns for 718.1 calories per
gram - a roughly 70 fold difference in energy release. (modern
propellents are probably higher energy concentrates)

A gallon of gas weighs approximately 2.8 kg, so if you burn 10 gallons
an hour you have released 322 Kcal of energy.  If in one hour you fire a
conservative 100 rounds per minute, 1 gram of propellent per bullet, you
release 4,308 Kcal of energy.  Multiply by 4 for 400 rounds per minute
that is being discussed.  

Note that the 1 gram per bullet is probably low, I couldn't find a
number for grains of propellent in 7.62 NATO, but 1 grain is 0.648
grams, so two grains would be 1.296 grams.  For comparison, most .45
ammo is loaded to 5 or 6 grains of smokeless powder.

Yes, you could have a closed system for an MG, but you'd add a couple
hundred pounds of weight to it with extra pipes, reservoir, pump and
fluid. The added mechanical complexity probably isn't worth it either as
you then have to have flexible hoses, clamps and other parts that can
fail. 

-Binhan

> -----Original Message-----
> From: Ryan Gill [mailto:rmgill@mindspring.com]
> Sent: Tuesday, March 11, 2003 8:19 AM
> To: gzg-l@csua.berkeley.edu
> Subject: Re: [SG,DS] Power Armour Weapon
> 
> 
> At 11:22 AM +0100 3/11/03, KH.Ranitzsch@t-online.de wrote:
> >
> >I doubt it. Evaporation is just about the fastest way to move heat
> >energy. Heat transfer through conduction (radiator to air) is much
> >slower. With a radiator, you need either a ventilator to move enough
> >air over a small radiator or a large surface area with free 
> air access
> >to get rid of the heat.
> 
> Close circuit systems seem to do pretty well. All but one of my 
> vehicles has it as a cooling system. What about your cars?
> -- 
> --
> Ryan Gill		 rmgill@SPAMmindspring.com
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> '60 Daimler Ferret '42 Daimler Dingo '42 Humber MkIV (1/2)
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