Annex60.Fluid.HeatPumps.Carnot_TCon

# .Annex60.Fluid.HeatPumps.Carnot_TCon

Heat pump with prescribed condenser leaving temperature and performance curve adjusted based on Carnot efficiency

## Information

This is a model of a heat pump whose coefficient of performance COP changes with temperatures in the same way as the Carnot efficiency changes. The control input is the setpoint of the condenser leaving temperature, which is met exactly at steady state if the heat pump has sufficient capacity.

The model allows to either specify the Carnot effectivness ηCarnot,0, or a COP0 at the nominal conditions, together with the evaporator temperature Teva,0 and the condenser temperature Tcon,0, in which case the model computes the Carnot effectivness as

ηCarnot,0 = COP0 ⁄ (Tcon,0 ⁄ (Tcon,0-Teva,0)).

The heat pump COP is computed as the product

COP = ηCarnot,0 COPCarnot ηPL,

where COPCarnot is the Carnot efficiency and ηPL is a polynomial in heating part load ratio yPL that can be used to take into account a change in COP at part load conditions. This polynomial has the form

ηPL = a1 + a2 yPL + a3 yPL2 + ...

where the coefficients ai are declared by the parameter `a`.

On the `Dynamics` tag, the model can be parametrized to compute a transient or steady-state response. The transient response of the model is computed using a first order differential equation for the evaporator and condenser fluid volumes. The heat pump outlet temperatures are equal to the temperatures of these lumped volumes.

#### Typical use and important parameters

When using this component, make sure that the condenser has sufficient mass flow rate. Based on the evaporator mass flow rate, temperature difference and the efficiencies, the model computes how much heat will be removed by to the evaporator. If the mass flow rate is too small, very low outlet temperatures can result, possibly below freezing.

The condenser heat flow rate `QCon_flow_nominal` is used to assign the default value for the mass flow rates, which are used for the pressure drop calculations. It is also used to compute the part load efficiency. Hence, make sure that `QCon_flow_nominal` is set to a reasonable value.

The maximum heating capacity is set by the parameter `QCon_flow_max`, which is by default set to infinity.

The coefficient of performance depends on the evaporator and condenser leaving temperature since otherwise the second law of thermodynamics may be violated.

#### Notes

For a similar model that can be used as a chiller, see Annex60.Fluid.Chillers.Examples.Carnot_TEva.

## Revisions

- January 3, 2017, by Michael Wetter:
  Removed parameters `effInpEva` and `effInpCon` and updated documentation. This is for issue 497.
- August 8, 2016, by Michael Wetter:
  Changed default temperature to compute COP to be the leaving temperature as use of the entering temperature can violate the 2nd law if the temperature lift is small.
  This is for Annex 60, issue 497.
- November 25, 2015 by Michael Wetter:
  First implementation.

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