Blocks: Newsletter Challenge (07/18/06)

The two blocks are at the same temperature so there would be no heat transfer and thus no power generated. The steel block feels cooler because its more thermally conductive than the plastic block. Of course, if you kept a finger on the metal block you might be able to generate a small amount of power with your turbine, but that would get boring.

I'd keep the joke going and ask him how he would design the turbine to get power
from such a small delta T.
Then I'd suggest using a thermocouple and let him try it.
No pain, no gain, no free lunch.

How do you keep an idiot busy for hours? Ask him how long it will take for the two blocks to reach the same temperature if you move them so they are touching. Have him check their temperature with his finger every 15 minutes...

>He starts to see dollar signs and shouts, "Let's >do it with big blocks — we'll make millions!" >What do you tell him? I would tell him to give me $50,000 for seed money to get this project going!!!

You need to sit down and have a beer, 'cause you're not going to like what I'm about to tell you: "I'm sorry, but we can't be friends anymore. Now drink your beer and leave!"

This is so seemple I am no going to answer!

Diamond, especially a big one, feels cold as ice. That 'ice' as Miss Monroe eulogised, conducts heat five times better than silver, a lot better than steel. In the plastic block/steel block scenario, I would advise the potential investor that we need big diamonds. OK he might sue me later, but think of all those blond haired maidens that might crowd round!

Both blocks are the same temperature and cooler than your body. The steel block only feels cooler than the plastic block because it is a better thermal conductor and is sinking your body heat faster.

as our competent coleagues evidenced the answer is easy. Let' s see the advantages, take such an action:

+ suggest your friend a scientific comitee for the project

+ fix a prize for the cost savings

+ tell him the truth and get the prize money

The metal block feels cooler only because it conducts away heat from your hand faster than the plastic block. They are of course at the same temperature and so cannot drive any heat engine.

What to tell him?? Please take an elementary physics course before you suffer terminal embarrassment.

OK, its bad enough that someone tries to get energy from two solid blocks at the same temperature, but with a "turbine"? Just how do you "hook up a turbine" to two solid blocks?

If you had said "hook up a bi-metallic junction, thermo-electric generator", "Seebeck effect generator", "thermopile", or even "thermocouple", I would have thought, "HA! Good one! The friend thinks the blocks are at different temperatures because one feels cooler than the other (due entirely to thermal transfer properties of the materials as noted by others)". But you didn't. You said, "hook up a turbine".

My understanding from two semesters of Thermodynamics in Engineering School is that a "turbine" works on the principle of fluid flow, not just heat flow. For a turbine to work mass must flow, not just energy. Fluid must move, not just heat. Of course, fluid can be made to move by heat, but that takes more equipment than just a "turbine".

Were you thinking that there could be enough air convection between the two bodies to provide enough breeze to power the turbine? Even if the steel was glowing red hot and the plastic was super-cooled by immersing in liquid nitrogen I doubt you would get any noticible air flow, much less enough to overcome the frictional forces in a turbine.

Oh, I get it, you were just trying to see if the less intelligent people would focus on the temperature issue and ignore the fact that you slipped in the word "turbine", right?

Yeah, right. Maybe you are not as smart as you think you are!

Steel is a better conductor, but it also takes more heat to raise a particular volume of steel one degree than it does for the same volume of plastic. It has a greater specific heat.

Maintaining the blocks at a cool temp requires engery. Check out the web site www.jchs.k12.net:81ag_aquaculture.htm they heat a green house for an 9000 sq foot vocational school green house which includes aquaculture fish tanks. They use the heat from a deep well produce the needed heat.