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sweeteviljesus
08-12-2014, 05:32 PM
Is it possible to concentrate ambient heat sort of like light being concentrated with a lens?

Thanks,
Rob

Chronos
08-12-2014, 05:39 PM
It is possible, but it requires the expenditure of energy, which ends up as more heat. For it to happen without the expenditure of extra energy would violate the Second Law.

boffking
08-12-2014, 05:42 PM
This sounds like the reverse of refrigeration.

Joey P
08-12-2014, 05:47 PM
This sounds like the reverse of refrigeration.

It's not reverse refrigeration, it's just regular refrigeration. Refrigeration isn't cooling something, it's removing the heat. To apply that to the OP, the heat is being concentrated on the evaporator or in the refrigerant or on the condenser, take your pick.

am77494
08-12-2014, 05:59 PM
Is it possible to concentrate ambient heat sort of like light being concentrated with a lens?

Thanks,
Rob

It is very possible and very expensive. Think of work as the best form of heat and ambient heat as a worse form (If you want to get technical read up on exergy).

As long as two places exist with a temperature difference , you can get work out of it - the efficiency is high if the temperature difference is high and low if not.

Some of the ways to use ambient heat are :

1. Concentrate salt from sea water
2. Run a thermodynamic cycle with deep groundwater (assuming it is cooler)
3. Swamp coolers
4. The drinking bird is a perfect example of how ambient heat is concentrated into energy.http://en.m.wikipedia.org/wiki/Drinking_bird

Stranger On A Train
08-12-2014, 06:01 PM
This sounds like the reverse of refrigeration.Actually, it's called a heat pump cycle (http://www.mpoweruk.com/images/heat_pump.gif), and it is exactly like the refrigeration cycle except you reverse the hot and cold "reservoirs" so that instead of pumping ambient thermal energy (heat) "outside" to keep the interior cold you pump heat inside to make it warm. As Chronos states, this requires that you do work in order to pump the energy "up" (to a higher temperature state) from the cold reservoir to the hot reservoir, which incidentially creates more heat to be rejected. This isn't a problem when you have a good medium to reject heat into, such as the ambient air, but can be a limiting condition when you are isolated and your work heat is at a lower temperature state than the hot reservoir, such that your waste heat gets dumped back into the refrigerated side.

It is very possible and very expensive.Not really. Ground source heat pumps are quite an efficient way to heat a house, and on large scales heat regeneration is used to incrementally improve overall plant efficiency in a very cost effective fashion.

Stranger

beowulff
08-12-2014, 06:10 PM
Heat pumps are one of the most efficient ways to heat.
In areas with mild winters, heat pumps can be 300% (or more) efficient - they can provide the equivalent of 300W of heat for 100W of energy. This makes them more cost-effective than gas or electric heating. This efficiency advantage is reduced in areas with very cold winters, making them less attractive.

am77494
08-12-2014, 06:16 PM
Not really. Ground source heat pumps are quite an efficient way to heat a house, and on large scales heat regeneration is used to incrementally improve overall plant efficiency in a very cost effective fashion.

Stranger
Not so fast. The question was about using ambient heat energy which typically means atmospheric.

Stranger On A Train
08-12-2014, 06:21 PM
The ground is also an "ambient" heat source, i.e. it is at the same temperature as the air (more or less). As you note, the density of thermal energy and conductivity makes it a better source than ambient air (even when the temperature is slightly colder) but it is certainly possible to pump energy fro air as well, as demonstrated by the refrigerator.

Stranger

Isilder
08-13-2014, 06:50 AM
Is it possible to concentrate ambient heat sort of like light being concentrated with a lens?

Thanks,
Rob


You can make an infra-red lense. If you meant the infra-red type of heat.

Science does say that the word "heat" has two meanings - the kinetic energy of molecules (and individual atoms), and Infra-red, but you'd be better to specify infra-red if you meant that.

cmyk
08-13-2014, 07:19 AM
You can make an infra-red lense. If you meant the infra-red type of heat.

Science does say that the word "heat" has two meanings - the kinetic energy of molecules (and individual atoms), and Infra-red, but you'd be better to specify infra-red if you meant that.

Nit: It's not necessarily exclusive to infrared. EM radiation by way of photons at any wavelength can induce heat. Though, granted, your average room and its objects are radiating mostly in IR and visible light.

Chronos
08-13-2014, 08:04 AM
Right, any sort of light will be converted to heat when absorbed, and any sort of light can be produced by hot objects. The only reason we associate infrared specifically with heat is that most of the things we think of as "warm" or "hot" (animal bodies, fires, etc.) are at a temperature such that most of the light they produce is infrared.

misling
08-13-2014, 09:26 AM
My first thought was "my car's interior sure concentrates heat in the summer" - any enclosed space that is more heat absorbing than heat radiating will 'concentrate' heat to some degree.

sweeteviljesus
08-13-2014, 09:45 AM
Isn't the car concentrating sunlight? A car parked in a shady spot won't get hotter that the ambient air will it (neglecting heat being emitted from the engine)?

Rob

Joey P
08-13-2014, 10:17 AM
Isn't the car concentrating sunlight? A car parked in a shady spot won't get hotter that the ambient air will it (neglecting heat being emitted from the engine)?

Rob

It's not concentrating heat from ambient air, it's collecting energy from the sun and storing it.

jtur88
08-13-2014, 10:30 AM
If I understand the question correctly, I think that is what a block of ice does. It then uses the concentrated heat to melt.