If you were to extract enough BTUs to lower 100 pounds of water 10 degrees C and were to convert that perfectly to mechanical energy how high could you raise the temperature of one pound of steel?

Answer 1

This is a question of heat capacity. The specific heat of water is about 9.3 times that of iron (I don't have a figure handy for steel but iron must be similar). So the heat extracted from the water is (weight of water) x 10 x (specific heat of water). The heat given to the steel will be (weight of steel) x T x (specific heat of steel). These are equal.

So: T = (Weight of water)/(Weight of steel) x 9.3 x 10 = 9,300 deg C.

This of course can't be done-thermodynamics doesn't allow heat to pass from a cooler to a hotter body. But it illustrates how much heat water contains. I know about that from paying to heat my swimming pool!

Answer 2

To lower 100 pounds of water by 10 degrees C, you would need to extract about 83,700 BTUs. If this energy were converted perfectly to mechanical energy and used to raise the temperature of one pound of steel, you could potentially raise the temperature of one pound of steel by around 7,737 degrees Celsius. This assumes perfect efficiency in the energy conversion process.