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# Efficiency of a heat pump watch

1. Could someone explain to me how the efficiency of a heat pump is more than 100% and how this is possible.

Thanks very much.
2. (Original post by sonic23)
Could someone explain to me how the efficiency of a heat pump is more than 100% and how this is possible.

Thanks very much.
Haha i assume this is a joke

In real life a heat pump can never be 100% efficient - it is always less
Haha i assume this is a joke

In real life a heat pump can never be 100% efficient - it is always less

no my teahcer has a phd and said this.
4. The heat pump can pump heat faster than the actual power of the pump.
5. i think its because the input is W

Whereas the output is Q+W

Therefore, the efficiency = (Q+W)/ W > 1
6. The function of a heat pump is to supply as much heat possible to the hot body.The coefficient of performance of a heat pump is measured by Q1/ W which is greater than 1.

A refrigerator, on the other hand, is designed to remove heat from the cold body ; its coefficient of performance is given by Q2/ W
7. (Original post by sonic23)
The function of a heat pump is to supply as much heat possible to the hot body.The coefficient of performance of a heat pump is measured by Q1/ W which is greater than 1.

A refrigerator, on the other hand, is designed to remove heat from the cold body ; its coefficient of performance is given by Q2/ W
This coefficient of performance is not the same as efficiency.
8. (Original post by El Doctoré de Mystéro)
This coefficient of performance is not the same as efficiency.
So would the efficiency of a heat pump be above or below 100%

this is killing me can someone please explain
9. (Original post by sonic23)
So would the efficiency of a heat pump be above or below 100%

this is killing me can someone please explain
Maybe get a hobby/some friends?
10. (Original post by sonic23)
So would the efficiency of a heat pump be above or below 100%

this is killing me can someone please explain
By definition the efficiency of something cannot be greater than 100%, as it is defined as the amount of work/energy output divided by the energy/work input.

This is always less than 100% because conservation of energy states that you can't get more out than you put in.
11. i think your confusing efficiency with coeffiecent of performance.
Maybe get a hobby/some friends?
lol
13. (Original post by El Doctoré de Mystéro)
By definition the efficiency of something cannot be greater than 100%, as it is defined as the amount of work/energy output divided by the energy/work input.

This is always less than 100% because conservation of energy states that you can't get more out than you put in.

The effiency of a heat engine is W/Q1 correct

a heat pump is the reverse of a hea engine, and the input is work being done with the output being Q1. Therefore the efficiency is Q1/W, which is a ratio greater than 100%...
14. Efficiency depends on the temperature difference you have.

The biggest temperature difference would be absolute zero and something on the other end of the spectrum.

No known place in teh universe is at absolute zero there you get less than 100%, you coudl come really close i guess but nor 100%+

More than 100% would be using energy and outputting more than what was given??
15. (Original post by M_01)
Efficiency depends on the temperature difference you have.

The biggest temperature difference would be absolute zero and something on the other end of the spectrum.

No known place in teh universe is at absolute zero there you get less than 100%, you coudl come really close i guess but nor 100%+

More than 100% would be using energy and outputting more than what was given??

hmm. im just gona leave this
16. A heat pump is a device for heating up something by drawing HEAT from the environment.
In order to do so it requires WORK to be done.
The WORK eventually turns into HEAT. You also are drawing HEAT from the environment.

Thus the work is the 100%. Whilst the heat from the enviroment is the rest of the heating.

Therefore the heat output can be greater than 100%.

However when we talk about the efficiency of heat engines, we compare the efficiency with that of the Carnot Cycle (which is by definition 100% efficient).
17. You can never get anything that is 100% efficient in terms of energy
18. (Original post by Mehh)
A heat pump is a device for heating up something by drawing HEAT from the environment.
In order to do so it requires WORK to be done.
The WORK eventually turns into HEAT. You also are drawing HEAT from the environment.

Thus the work is the 100%. Whilst the heat from the enviroment is the rest of the heating.

Therefore the heat output can be greater than 100%.

However when we talk about the efficiency of heat engines, we compare the efficiency with that of the Carnot Cycle (which is by definition 100% efficient).

So the HEAT OUTPUT can be more than 100% because it is the addition of heat from the cold body and the work being done.

However, the efficiency cannot be 100 percent. Could you please explain to me a bit more about the carnot cycle?

Thanks bro
19. To understand what a Carnot Cycle is, I have to give a small crash course in Thermodynamics.

There are two types of thermodynamic devices in existance, Heat Pumps and Heat Engines.
Both of them are devices where energy is transfered between two heatsinks and work.
A Heat Pump moves energy from a cold source to a hot source, using work.
A Heat Engine moves heat from a hot source to a cold source producing work.

Now it can be proven that the maximum amount of work produced by a heat engine is when the process is reversible.
It can similarly be proven that the most heat pumped per unit of work is with a reversible heat pump.

The inability to reverse a process comes from something we call Entropy.
The Carnot Cycle is a theoretical heat engine/heat pump which produces zero Entropy and hence is reversible and thus for a given pair of heat sinks (at a given temperature) has the best co-efficient of performance.

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