modelCHP
Information
The CHP model does not consider part-load operation (ON/OFF regulation is assumed). Thus, constant natural gas consumption and total efficiency are assumed. The electrical efficiency is computed assuming a constant second-law efficiency, whose value is computed using the nominal operating conditions.
The gas source is assumed to be at a constant temperature of 500ºC. The primary side fluid is modeled by means of 1-D incompressible fluid flow model (Cell1DimInc), in which a dynamic energy balance and static mass and momentum balances are applied on the fluid. The heat transfer in the primary fluid is modeled with a constant heat transfer coefficient. However, it can be changed to other heat transfer models through the HeatTransfer parameter in the fluid model.
Furthermore, the model includes a Boolean input connector on_off, which defines the operational state of the CHP. In the equations, the Boolean input is translated to a variable value together with a first order block, which can take into account a start-up time constraint. The model also includes a real output connector Wdot_el, which outputs the value of the generated electrical power. This connector is useful, for example, in the case where a heat pump is powered by the CHP.
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| Modelica.Units.SI.Volume | V | 0.005 | Internal volume |
| Modelica.Units.SI.Area | A | 10 | Heat exchange area |
| Modelica.Units.SI.MassFlowRate | Mdotnom | 10 | Nominal mass flow rate of the working fluid |
| Real | eta_tot | 0.9 | Total efficiency of the CHP |
| Modelica.Units.SI.Time | tau | 60 | Start-up time constant |
| Modelica.Units.SI.Temperature | Tmax | 273.15 + 100 | Maximum temperature at the outlet |
| Modelica.Units.SI.Temperature | Th_nom | 500 + 273.15 | |
| Initialization | |||
| Modelica.Units.SI.Temperature | Th_start | 500 + 273.15 | Start value for the condenser temperature |
Connectors
| Type | Name | Default | Description |
|---|---|---|---|
| Modelica.Fluid.Interfaces.FluidPort_a | InFlow | ||
| Modelica.Fluid.Interfaces.FluidPort_b | OutFlow | ||
| Modelica.Thermal.HeatTransfer.Interfaces.HeatPort_a | HeatSource | ||
| Modelica.Blocks.Interfaces.BooleanInput | on_off | ||
| Modelica.Blocks.Interfaces.RealOutput | Wdot_el |
Components
| Type | Name | Default | Description |
|---|---|---|---|
| Real | eta_el | Electrical efficiency of the CHP | |
| Real | eta_th | Thermal efficiency of the CHP | |
| Modelica.Units.SI.Power | Wdot | ||
| Modelica.Units.SI.Power | Qdot | ||
| Modelica.Units.SI.Temperature | Tc | ||
| Real | LHV | 1000 | |
| Modelica.Units.SI.MassFlowRate | Mdot_nom_fuel | ||
| Modelica.Units.SI.Temperature | T_water_ex_CHP | ||
| Modelica.Units.SI.Power | Qdot_gas | ||
| Real | eta_el_nom | Nominal electrical efficiency of the CHP | |
| Real | eta_th_nom | Nominal thermal efficiency of the CHP | |
| Real | eta_II_nom | ||
| Modelica.Units.SI.Temperature | Th | ||
| Modelica.Units.SI.Temperature | Tc_nom | ||
| Flows.FluidFlow.Cell1DimInc | fluid | ||
| Interfaces.Heat.HeatPortConverter | heatPortConverter | ||
| Modelica.Thermal.HeatTransfer.Sources.PrescribedHeatFlow | prescribedHeatFlow | ||
| Modelica.Blocks.Continuous.FirstOrder | firstOrder | ||
| Modelica.Fluid.Sensors.Temperature | T_ex_CHP |
Contents
| Name | Description |
|---|---|
 Medium |