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Stephen wrote:
>> ...oh, wait...
>
> Yes, the cardiovascular system is an effective heat exchanger working with the
> lungs and skin. :)
More impressive is the scientific *fact* this this system is somehow
able to keep the contents of the human body at a temperature drastically
*lower* than the surrounding ambient, even though the human body itself
generates heat, in utter defience of the 2nd law of thermodynamics.
I'd never believe it if I hadn't seen it with my own eyes...
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scott wrote:
> Maybe not burning to a crisp, but if you raise the temperature of your
> innards by just a few degrees things begin to screw up very rapidly.
> You have quite a sophisticated temperature control system to keep you at
> around 37 degrees inside...
Or, to put it the correct way round, your life processes are designed to
work at one specific temperature *because* you have an elaborate system
designed to keep things at exactly that temperature. ;-)
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> More impressive is the scientific *fact* this this system is somehow
> able to keep the contents of the human body at a temperature drastically
> *lower* than the surrounding ambient, even though the human body itself
> generates heat, in utter defience of the 2nd law of thermodynamics.
http://en.wikipedia.org/wiki/Evaporation
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On Fri, 09 Jan 2009 11:48:15 +0000, Invisible <voi### [at] dev null> wrote:
>Stephen wrote:
>
>>> ...oh, wait...
>>
>> Yes, the cardiovascular system is an effective heat exchanger working with the
>> lungs and skin. :)
>
>More impressive is the scientific *fact* this this system is somehow
>able to keep the contents of the human body at a temperature drastically
>*lower* than the surrounding ambient, even though the human body itself
>generates heat, in utter defience of the 2nd law of thermodynamics.
>
>I'd never believe it if I hadn't seen it with my own eyes...
Sorry, but the ambient temperature is generally lower than body temperature.
When it is higher we use evaporation, as Scott says.
Although it is amazing the temperatures that we can tolerate. Once I was working
--
Regards
Stephen
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>> More impressive is the scientific *fact* this this system is somehow
>> able to keep the contents of the human body at a temperature drastically
>> *lower* than the surrounding ambient, even though the human body itself
>> generates heat, in utter defience of the 2nd law of thermodynamics.
>>
>> I'd never believe it if I hadn't seen it with my own eyes...
>
> Sorry, but the ambient temperature is generally lower than body temperature.
Yes, _usually_ it is, and this is quite unsurprising.
> When it is higher we use evaporation, as Scott says.
didn't die. Indeed, although he came out looking half dead, a
radiothermometer confirms that his *internal* temperature barely moved.
> Although it is amazing the temperatures that we can tolerate. Once I was working
*serious* protective clothing...
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On Fri, 09 Jan 2009 12:55:19 +0000, Invisible <voi### [at] devnull> wrote:
>
>didn't die. Indeed, although he came out looking half dead, a
>radiothermometer confirms that his *internal* temperature barely moved.
>
Again several years ago, when I was working offshore, I worked for two days on a
separation train where the ambient temperature was IIRC about 50deg C. There was
a team of us taking turns monitoring the instrumentation as the HVAC system had
failed. We would spend about 30 mins in the heat and 30 mins cooling down then
back into the heat. All of us were able to keep it up foe 12 hours a day. I
can't remember how much water we drank but we were given salt tablets as well.
Remember "Production Rules". :)
>> Although it is amazing the temperatures that we can tolerate. Once I was working
>
>*serious* protective clothing...
No serious PPE (Personal Protective Equipment). Safety boots, jeans, tee shirt,
overalls, leather/cotton gloves and hard hat. I tried removing my tee shirt but
the metal on the overalls was too hot to touch. I know what the temperature was
because I took a mercury thermometer up to check as I wanted to know what the
temperature was and a bi-metallic strip thermometer was reading over 100C.
--
Regards
Stephen
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Stephen wrote:
> No serious PPE (Personal Protective Equipment). Safety boots, jeans, tee shirt,
> overalls, leather/cotton gloves and hard hat. I tried removing my tee shirt but
> the metal on the overalls was too hot to touch. I know what the temperature was
> because I took a mercury thermometer up to check as I wanted to know what the
> temperature was and a bi-metallic strip thermometer was reading over 100C.
can only assume that your drenched clothing somehow kept you a few
degrees cooler than that or something. (Surely water must evapourate
stupidly fast at almost boiling point!)
Reminds me of the time I was trapped by a fire. I didn't realise that
skin could actually excrete water that fast. I'm not kidding, I had
water *pouring* off me like water flows out of a tap. I have no idea how
much water there is in the human body, but I'd suggest fatal dehydration
couldn't take very long at that speed. (I had one *bad* headache
afterwards!)
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On Fri, 09 Jan 2009 14:28:51 +0000, Invisible <voi### [at] devnull> wrote:
>
>can only assume that your drenched clothing somehow kept you a few
>degrees cooler than that or something. (Surely water must evapourate
>stupidly fast at almost boiling point!)
>
At those temperatures your clothing is bone dry. If it had been wet then there
is a big chance of being scalded. (Counter intuitive, I know)
>Reminds me of the time I was trapped by a fire. I didn't realise that
>skin could actually excrete water that fast. I'm not kidding, I had
>water *pouring* off me like water flows out of a tap. I have no idea how
>much water there is in the human body, but I'd suggest fatal dehydration
>couldn't take very long at that speed. (I had one *bad* headache
>afterwards!)
It is amazing how fast you can sweat once you get started.
--
Regards
Stephen
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Invisible wrote:
> *serious* protective clothing...
Ever heard of sauna? ;P
-- Arttu Voutilainen
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scott wrote:
> Probably some sort of continuous calibration system to account for
> temperature changes etc, I guess the head movement mechanisms need to be
> controlled pretty accurately!
Interesting idea. Maybe I'll leave it on for a few minutes, idle, and see if
it keeps making noises after it has been spinning for a while.
As an aside, it turns out that on CDMA at least, the list of cell phone
numbers that should start ringing during this 1.25 time fits in one or two
packets, and is sorted by phone number, so while you're listening, if you
hear a higher phone number in the list, you can power down. It turns out you
have to adjust the sleep timer depending on how many phone numbers you
listened to, because running the receiver heats up the quartz crystal
differently depending on how long it runs, so the timer runs at a different
speed, and you'll miss your wake-up window if you don't. Pretty intensely
complicated inside there.
--
Darren New, San Diego CA, USA (PST)
Why is there a chainsaw in DOOM?
There aren't any trees on Mars.
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