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Old 10-08-2011, 12:08 PM   #16
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Yes, its good stuff.

Another way to think about it:
The heat energy is not a constant value. The temperature of the substance is a measurement of molecular activity. If you remember from 7th grade science class, water molecules in warm water are moving at a faster rate, than the molecules in the colder water. The volume and state of the water remained the same. The temp difference was the acceleration of the particles, and their interaction with one another.
Now when we apply this concept to the refrigeration cycle, the liquid refrigerant particles are compacted together, bouncing off of one another at a rapid rate. When the refrigerant is expanded in a larger space (that being a lower pressure area) the molecules are interacting at a lower rate. The heat energy is dissapated as molecular interaction decreases.
This is not the whole picture of the process, but that is why the refrigerant is not as warm as it is in the liquid phase.

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Old 10-08-2011, 12:13 PM   #17
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Originally Posted by dlloyd
To TechNow

The question is the opposite of the TXV question. When the compressor raises the pressure the temperature increases. In a pressure cooker this happens but it is energized by the stove heating coil.What does that in a heat pump? In order for any substance to increase its temperature, it requires the insertion of heat energy.

"Heat of compression" Can you explain that better?
Heat of compression is basically friction.

The heat pump is no different than an a/c. Its just the evap is now outside, and condenser inside.
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Old 10-18-2011, 08:33 AM   #18
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No, friction is not the answer. That would be a terrible loss.

When the compressor raises the pressure, the temperature is increased as we know. But the heat energy that drives his is the same source hat gives us COPs greater than 100%

The electrical energy the runs the compressor is first converted to mechanical energy to drive the compressor. A small amount is converted to heat energy because of friction as a loss. Then the mechanical energy is converted to heat energy. It cannot be used up or dissipated, only converted to another form.

That heat energy from the electrical energy is inserted into the refrigerant to raise the temperature. It also adds to to ground heat energy to give the high COP.

Elec. Energy (in BTU) +ground source energy(in BTU)
COP= ________________________________________________ =400%
Elec. Energy (in BTU)

That's it.
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Old 10-18-2011, 06:06 PM   #19
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Quote:
Originally Posted by dlloyd View Post
No, friction is not the answer. That would be a terrible loss.

When the compressor raises the pressure, the temperature is increased as we know. But the heat energy that drives his is the same source hat gives us COPs greater than 100%

The electrical energy the runs the compressor is first converted to mechanical energy to drive the compressor. A small amount is converted to heat energy because of friction as a loss. Then the mechanical energy is converted to heat energy. It cannot be used up or dissipated, only converted to another form.

That heat energy from the electrical energy is inserted into the refrigerant to raise the temperature. It also adds to to ground heat energy to give the high COP.

Elec. Energy (in BTU) +ground source energy(in BTU)
COP= ________________________________________________ =400%
Elec. Energy (in BTU)

That's it.

That's correct...Heat of compression. That's why the refrigerant has to be a gas form to compress. The energy to run the compressor (less losses) goes to raising the temperature and energy content of the gas.

The flip side: In my steam plant days....we condensed the steam back to condensate because it took less energy to raise the pressure (not temperature) to inject it back to the steam generator.
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Old 10-18-2011, 06:24 PM   #20
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Google "P-h diagram refrigeration cycle". It shows the states the refrigerant passes thru...some of the diagrams show actual cycles including superheat and subcooling in the real world (not the "ideal" cycles)
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Old 10-18-2011, 07:30 PM   #21
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Quote:
Originally Posted by dlloyd
No, friction is not the answer. That would be a terrible loss.

When the compressor raises the pressure, the temperature is increased as we know. But the heat energy that drives his is the same source hat gives us COPs greater than 100%

The electrical energy the runs the compressor is first converted to mechanical energy to drive the compressor. A small amount is converted to heat energy because of friction as a loss. Then the mechanical energy is converted to heat energy. It cannot be used up or dissipated, only converted to another form.

That heat energy from the electrical energy is inserted into the refrigerant to raise the temperature. It also adds to to ground heat energy to give the high COP.

Elec. Energy (in BTU) +ground source energy(in BTU)
COP= ________________________________________________ =400%
Elec. Energy (in BTU)

That's it.

When moving surfaces (refrigerant molecules) come in contact with each other, the kinetic energy is converted into heat. Kinetic energy is converted to heat whenever motion and friction occur. Thus, heat of compression, is from friction.

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