Increasing the COP and the heat pump

[Pisica]

How do you draw the heat pump in the p-V diagram?

Currently, it refers to the Carnot cycle, which has two isotherms and two adiabatic ones.

But I think that there is no isotherm in the heat pump, as well as the refrigerator.
On one heat sink it absorbs heat and on another it removes heat

And the compression and expansion of the gas cannot be isothermal.

I believe that when expanding the gas at the "evaporator" it is a mechanical thing that is lost that can be recovered.

The discussion will be clarified as we discuss if we are interested.
Let's begin, please,
With the drawing of the cycle in p-V coordinates/ For the heat pump or refrigerator or air conditioner.

 

[Pisica]

In the video above there is such a system. It can be used both to create cold and to create warm.

In the picture above is the "evaporator", that is, a thin pipe that allows the passage of a small amount of gas.

I think that if I replaced this thin tube evaporator with a turbine, I would recover energy.

 

[PeterDonis]

think that there is no isotherm in the heat pump, as well as the refrigerator.

There is, at least in the ideal case. Both the condenser and the evaporator are isothermal, at least as long as both phases are present.

On one heat sink it absorbs heat and on another it removes heat

Yes, but the heat being transferred is latent heat as far as the working fluid is concerned, meaning that the transfer occurs at constant temperature.

And the compression and expansion of the gas cannot be isothermal.

That's correct, those portions of the cycle are not isothermal. They are usually idealized as adiabatic (no heat transfer in or out of the working fluid).

 

[PeterDonis]

the drawing of the cycle in p-V coordinates

Are you sure you want a pressure-volume diagram? A pressure-enthalpy diagram is much more commonly used for this kind of analysis.

 

[PeterDonis]

I believe that when expanding the gas at the "evaporator" it is a mechanical thing that is lost that can be recovered.

I think that if I replaced this thin tube evaporator with a turbine, I would recover energy.

Why do you think that?

 

[Pisica]

"Yes, but the heat being transferred is latent heat as far as the working fluid is concerned, meaning that the transfer occurs at constant temperature."
Do you mean the latent heat of evaporation and condensation, of changing from gas to liquid and vice versa?

But the heat pump can't work with gas without reaching the liquid state, that is, without changing its state of aggregation?

 

[PeterDonis]

the heat pump can't work with gas without reaching the liquid state, that is, without changing its state of aggregation?

That's correct. A phase change from gas to liquid occurs in the condenser--that's why it's called a condenser. And a phase change from liquid to gas occurs inside the evaporator--that's why it's called an evaporator.