Energy Conversion 2

[ARgearhead]

What would be the best way to convert mechanical energy (i.e. human pedaling, cranking, etc.) into enough heat to boil water? Is there a way to go straight from mechaincal to heat, or would it work better to go to electricity and how?

 

[pmover]

friction between two surfaces - like brake shoes - may create enough heat to boil water. pick two materials that will most suitable for the demo. i would not want to be the power source . . .
drive a dc generator that is connected electrically to a heating grid.
either way, it would likely take quite a while to "boil water". of course, how much water is needed to boil?
a solar water bag is better for warming water, but not quite boil.

good luck!
-pmover

 

[IRstuff]

Do the math first. Figure out how many joules you need.

TTFN

 

[BigInch]

Then go solar.

Going the Big Inch!

http://virtualpipeline.spaces.msn.com

 

[JStephen]

With the right conditions, you can get more heat transfer using a heat-pump arrangement than a frictional type arrangement. Depends on why you're asking.

I remember a Dagwood comic strip from long ago. The door-to-door salesman comes around and says he is selling "hot rocks". The way they work is "You just rub them together to produce heat!" Closing line: "And if that doesn't work, by the time you're done, you'll be too tired to care."

 

[MintJulep]

I have an exercise "rider" at home that uses a fluid damper as its resistance. The surface of the damper gets too hot to touch after a few minuts, probably about 130 - 140F.

Certainly it is possible. The question is how much water, and in what time.

The sustainable power output of a human is relatively well documented. If the power meters on excercise bikes are to be believed, I can sustain 100 watts pretty much indefinately, and peak near 300 watts for (very) short bursts.

As IRstuff said, do the math.

 

[BigInch]

100 W is petty close to perking a pot of coffee each hour. Let's see... What time will I get to work?

Going the Big Inch!

http://virtualpipeline.spaces.msn.com

 

[Yorkman]

How about 778Ft/lbs = 1 BTU; James Prescot Joule did it with a series of paddles with counter wieghts and pullies in an experiment to determine the aprx. mechanical equivalant to heat, or so I'm told.

I'm not a real engineer, but I play one on T.V.
A.J. Gest, York Int./JCI

 

[MintJulep]

Ah, put the estimed Mr. Joule's paddles produced a rather low quality heat. Difficult to achieve boiling by stirring water at anything near atmospheric pressure.

But that spurred a thought.

Suppose you replace the damper on my exercise rider with an air cylinder and a check valve. That is to say, turn it into a vacuum pump...

 

[Yorkman]

Now your thinking out of the box!!! Heck with a fast cadence even a fat guy like me could get tepid water to boil, he did'nt specify what the temperature had to be did he?

I'm not a real engineer, but I play one on T.V.
A.J. Gest, York Int./JCI

 

[KiwiMace]

Nice vacuum idea - Do it on a mountain.

If you turbine straight into a fixed volume of water that is well (perfectly) insulated, eventually that pot will boil - ie. as long as the heat doesn't get lost in the process.
I can't get past how fritzed out you are going to get when it takes 1hr to get your coffee fix in a morning - you are going to need to burn that energy off on a bike.

 

[BigInch]

If you do this in a near vacuum, the water boils, but its at ambient temperature. Not much of a wake-up.

Going the Big Inch!

http://virtualpipeline.spaces.msn.com

 

[MintJulep]

But a good way to make iced coffee!

 

[BigInch]

Excellent! Now that's thinking out of the box.

Going the Big Inch!

http://virtualpipeline.spaces.msn.com