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Thermal Dynamics question.


thorne

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I am an engineer, fucker.

 

Electro-Mechanical, but dabble in quantum dynamics. See sig pic.

You're different. I'm speaking about the other idiots. Now get back in your hole.

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Actually, I dabble in engineering too, mechanical though.

 

 

How are you going to go about setting up this test? Remember the cooling/heating curves are logrithmic and approach a horizontal asymtote at delta T = 0, so this test could take a long time depending on cup size and temperature difference. Maybe you could track and plot the data points in Excel at like 5 min intervals? +-10 degrees would probably work good for starting points, but what would the variance be for human and measurement error? Might have to make the temps a little higher/lower... Stirring the water or a breeeze can have a big difference too, so try and minimize these variables or make them constant. This is going to be totally sweet... :cool:

 

It doesn't say wether or not the cups have lids in the original post... sooo maybe we could go ahead and do that? :p

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Actually, I dabble in engineering too, mechanical though.

 

Interesting that you dabble in ME. I guess you shouldn't say "ME though". ME has a focus on thermodynamics and all the rest of that fun stuff.

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I was an engineering major until I went to Athens.... shorty after I switched to programming

So that makes you ______.

 

A. Not an engineer.

B. Not a Cobra.

C. All of the above.

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The hotter cup.

 

The room has more mass of average temperature than the liquids. By design, molecules want to move faster within their realm of energy, so they "steal" heat to increase their movement, thus why things cool down.

 

The room has a greater mass than the cup of cooler liquid, so the room's mass will steal the heat from the hot liquid of smaller mass, cooling it down quicker than a small mass cup of liquid trying to steal the heat from a room much bigger than itself.

Not to mention the warmer cup's goal is to be "lazy" and shed it's energy. It's easier for an item to release energy as opposed to absorbing it.

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So, to continue beating the cooling horse.

 

Jeffmeden, what do you think about condensation forming on the colder cup? Seeing how condensation is the opposite of evaporation, it releases the heat it took to evaporate it when it condenses. I would think it would also increase the efficiency of the thermal barrier it condenses on.

 

I hypothesize that if we assume the OP's containers are not sealed, condensation could cancel out any potential gains evaporative cooling gives to the hotter cup. :cool:

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  • 2 weeks later...
The hot cup will reach room temperature first.

 

and EVERYONE in the thread has gotten the explaination of the answer why wrong.

 

<--- engineer with 2 actual real f**-ing degrees

BS Astronautical Engineering

BS Aeronautical Engineering

 

Considering that the problem does not state if the cup is covered or not, or give any psychrometric data, how could you determine this other than NLoC?

 

Seriously, I am very interested! I'm not taking heat transfer until this fall, so I only know the basics...

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