# -*- coding: utf-8
"""Module of class Merge.
This file is part of project TESPy (github.com/oemof/tespy). It's copyrighted
by the contributors recorded in the version control history of the file,
available from its original location tespy/components/nodes/merge.py
SPDX-License-Identifier: MIT
"""
import numpy as np
from tespy.components.nodes.base import NodeBase
from tespy.tools.data_containers import SimpleDataContainer as dc_simple
from tespy.tools.document_models import generate_latex_eq
from tespy.tools.fluid_properties import s_mix_pT
[docs]
class Merge(NodeBase):
r"""
Class for merge points with multiple inflows and one outflow.
**Mandatory Equations**
- :py:meth:`tespy.components.nodes.base.NodeBase.mass_flow_func`
- :py:meth:`tespy.components.nodes.base.NodeBase.pressure_equality_func`
- :py:meth:`tespy.components.nodes.merge.Merge.fluid_func`
- :py:meth:`tespy.components.nodes.merge.Merge.energy_balance_func`
Inlets/Outlets
- specify number of outlets with :code:`num_in` (default value: 2)
- out1
Image
.. image:: /api/_images/Merge.svg
:alt: flowsheet of the merge
:align: center
:class: only-light
.. image:: /api/_images/Merge_darkmode.svg
:alt: flowsheet of the merge
:align: center
:class: only-dark
Parameters
----------
label : str
The label of the component.
design : list
List containing design parameters (stated as String).
offdesign : list
List containing offdesign parameters (stated as String).
design_path : str
Path to the components design case.
local_offdesign : boolean
Treat this component in offdesign mode in a design calculation.
local_design : boolean
Treat this component in design mode in an offdesign calculation.
char_warnings : boolean
Ignore warnings on default characteristics usage for this component.
printout : boolean
Include this component in the network's results printout.
num_in : float, dict
Number of inlets for this component, default value: 2.
Example
-------
The merge mixes a specified number of mass flows and has a single outlet.
At the outlet, fluid composition and enthalpy are calculated by mass
weighted fluid composition and enthalpy of the inlets.
>>> from tespy.components import Sink, Source, Merge
>>> from tespy.connections import Connection
>>> from tespy.networks import Network
>>> import shutil
>>> import numpy as np
>>> nw = Network(p_unit='bar', iterinfo=False)
>>> so1 = Source('source1')
>>> so2 = Source('source2')
>>> so3 = Source('source3')
>>> si1 = Sink('sink')
>>> m = Merge('merge', num_in=3)
>>> m.component()
'merge'
>>> inc1 = Connection(so1, 'out1', m, 'in1')
>>> inc2 = Connection(so2, 'out1', m, 'in2')
>>> inc3 = Connection(so3, 'out1', m, 'in3')
>>> outg = Connection(m, 'out1', si1, 'in1')
>>> nw.add_conns(inc1, inc2, inc3, outg)
A merge with three inlets mixes air (simplified) with pure nitrogen and
pure oxygen. All gases enter the component at the same temperature. As
mixing effects are not considered, the outlet temperature should thus be
similar to the three inlet temperatures (difference might occur due to
rounding in fluid property functions, let's check it for two different
temperatures). It is e.g. possible to find the required mass flow of pure
nitrogen given the nitrogen mass fraction in the outlet.
>>> T = 293.15
>>> inc1.set_attr(fluid={'O2': 0.23, 'N2': 0.77}, p=1, T=T, m=5)
>>> inc2.set_attr(fluid={'O2': 1}, T=T, m=5)
>>> inc3.set_attr(fluid={'N2': 1}, T=T)
>>> outg.set_attr(fluid={'N2': 0.4})
>>> nw.solve('design')
>>> round(inc3.m.val_SI, 2)
0.25
>>> abs(round((outg.T.val_SI - T) / T, 5)) < 0.01
True
>>> T = 173.15
>>> inc1.set_attr(T=T)
>>> inc2.set_attr(T=T)
>>> inc3.set_attr(T=T)
>>> nw.solve('design')
>>> abs(round((outg.T.val_SI - T) / T, 5)) < 0.01
True
"""
[docs]
@staticmethod
def component():
return 'merge'
[docs]
@staticmethod
def get_parameters():
return {'num_in': dc_simple()}
[docs]
def get_mandatory_constraints(self):
variable_fluids = set(
[fluid for c in self.inl + self.outl for fluid in c.fluid.is_var]
)
num_fluid_eq = len(variable_fluids)
if num_fluid_eq == 0:
num_fluid_eq = len(self.inl[0].fluid.val)
num_m_eq = 0
else:
num_m_eq = 1
return {
'mass_flow_constraints': {
'func': self.mass_flow_func, 'deriv': self.mass_flow_deriv,
'constant_deriv': True, 'latex': self.mass_flow_func_doc,
'num_eq': num_m_eq},
'fluid_constraints': {
'func': self.fluid_func, 'deriv': self.fluid_deriv,
'constant_deriv': False, 'latex': self.fluid_func_doc,
'num_eq': num_fluid_eq},
'energy_balance_constraints': {
'func': self.energy_balance_func,
'deriv': self.energy_balance_deriv,
'constant_deriv': False, 'latex': self.energy_balance_func_doc,
'num_eq': 1},
'pressure_constraints': {
'func': self.pressure_equality_func,
'deriv': self.pressure_equality_deriv,
'constant_deriv': True,
'latex': self.pressure_equality_func_doc,
'num_eq': self.num_i + self.num_o - 1}
}
[docs]
def inlets(self):
if self.num_in.is_set:
return ['in' + str(i + 1) for i in range(self.num_in.val)]
else:
self.set_attr(num_in=2)
return self.inlets()
[docs]
@staticmethod
def outlets():
return ['out1']
@staticmethod
def is_branch_source():
return True
[docs]
def fluid_func(self):
r"""
Calculate the vector of residual values for fluid balance equations.
Returns
-------
residual : list
Vector of residual values for component's fluid balance.
.. math::
0 = \sum_i \dot{m}_{in,i} \cdot x_{fl,in,i} -
\dot {m}_{out} \cdot x_{fl,out}\\
\forall fl \in \text{network fluids},
\; \forall i \in \text{inlets}
"""
residual = []
for fluid, x in self.outl[0].fluid.val.items():
res = -x * self.outl[0].m.val_SI
for i in self.inl:
res += i.fluid.val[fluid] * i.m.val_SI
residual += [res]
return residual
[docs]
def fluid_func_doc(self, label):
r"""
Calculate the vector of residual values for fluid balance equations.
Parameters
----------
label : str
Label for equation.
Returns
-------
latex : str
LaTeX code of equations applied.
"""
latex = (
r'0=\sum_i \dot{m}_{\mathrm{in,}i} \cdot x_{fl\mathrm{,in,}i}'
r'- \dot {m}_\mathrm{out} \cdot x_{fl\mathrm{,out}}'
r'\; \forall fl \in \text{network fluids,} \; \forall i \in'
r'\text{inlets}'
)
return generate_latex_eq(self, latex, label)
[docs]
def fluid_deriv(self, increment_filter, k):
r"""
Calculate partial derivatives of fluid balance.
Parameters
----------
increment_filter : ndarray
Matrix for filtering non-changing variables.
k : int
Position of derivatives in Jacobian matrix (k-th equation).
"""
o = self.outl[0]
for fluid, x in self.outl[0].fluid.val.items():
for i in self.inl:
if i.m.is_var:
self.jacobian[k, i.m.J_col] = i.fluid.val[fluid]
if fluid in i.fluid.is_var:
self.jacobian[k, i.fluid.J_col[fluid]] = i.m.val_SI
if o.m.is_var:
self.jacobian[k, o.m.J_col] = -x
if fluid in o.fluid.is_var:
self.jacobian[k, o.fluid.J_col[fluid]] = -o.m.val_SI
k += 1
[docs]
def energy_balance_func(self):
r"""
Calculate energy balance.
Returns
-------
residual : float
Residual value of energy balance.
.. math::
0 = \sum_i \left(\dot{m}_{in,i} \cdot h_{in,i} \right) -
\dot{m}_{out} \cdot h_{out}\\
\forall i \in \text{inlets}
"""
res = -self.outl[0].m.val_SI * self.outl[0].h.val_SI
for i in self.inl:
res += i.m.val_SI * i.h.val_SI
return res
[docs]
def energy_balance_func_doc(self, label):
r"""
Calculate energy balance.
Parameters
----------
label : str
Label for equation.
Returns
-------
latex : str
LaTeX code of equations applied.
"""
latex = (
r'0=\sum_i\left(\dot{m}_{\mathrm{in,}i}\cdot h_{\mathrm{in,}i}'
r'\right) - \dot{m}_\mathrm{out} \cdot h_\mathrm{out} '
r'\; \forall i \in \text{inlets}'
)
return generate_latex_eq(self, latex, label)
[docs]
def energy_balance_deriv(self, increment_filter, k):
r"""
Calculate partial derivatives of energy balance.
Parameters
----------
increment_filter : ndarray
Matrix for filtering non-changing variables.
k : int
Position of derivatives in Jacobian matrix (k-th equation).
"""
for i in self.inl:
if i.m.is_var:
self.jacobian[k, i.m.J_col] = i.h.val_SI
if i.h.is_var:
self.jacobian[k, i.h.J_col] = i.m.val_SI
o = self.outl[0]
if o.m.is_var:
self.jacobian[k, o.m.J_col] = -o.h.val_SI
if o.h.is_var:
self.jacobian[k, o.h.J_col] = -o.m.val_SI
[docs]
@staticmethod
def is_branch_source():
return True
[docs]
def start_branch(self):
outconn = self.outl[0]
branch = {
"connections": [outconn],
"components": [self, outconn.target],
"subbranches": {}
}
outconn.target.propagate_to_target(branch)
return {outconn.label: branch}
[docs]
def propagate_to_target(self, branch):
return
[docs]
def propagate_wrapper_to_target(self, branch):
if self in branch["components"]:
return
outconn = self.outl[0]
branch["connections"] += [outconn]
branch["components"] += [self]
outconn.target.propagate_wrapper_to_target(branch)
[docs]
def entropy_balance(self):
r"""
Calculate entropy balance of a merge.
Note
----
A definition of reference points is included for compensation of
differences in zero point definitions of different fluid compositions.
- Reference temperature: 298.15 K.
- Reference pressure: 1 bar.
.. math::
\dot{S}_\mathrm{irr}= \dot{m}_\mathrm{out} \cdot
\left( s_\mathrm{out} - s_\mathrm{out,ref} \right)
- \sum_{i} \dot{m}_{\mathrm{in,}i} \cdot
\left( s_{\mathrm{in,}i} - s_{\mathrm{in,ref,}i} \right)\\
"""
T_ref = 298.15
p_ref = 1e5
o = self.outl[0]
self.S_irr = o.m.val_SI * (
o.s.val_SI - s_mix_pT(p_ref, T_ref, o.fluid_data, o.mixing_rule)
)
for i in self.inl:
self.S_irr -= i.m.val_SI * (
i.s.val_SI - s_mix_pT(p_ref, T_ref, i.fluid_data, i.mixing_rule)
)
[docs]
def exergy_balance(self, T0):
r"""
Calculate exergy balance of a merge.
Parameters
----------
T0 : float
Ambient temperature T0 / K.
Note
----
Please note, that the exergy balance accounts for physical exergy only.
.. math ::
\dot{E}_\mathrm{P} =
\begin{cases}
\begin{cases}
\sum_i \dot{m}_i \cdot \left(e_\mathrm{out}^\mathrm{PH} -
e_{\mathrm{in,}i}^\mathrm{PH}\right)
& T_{\mathrm{in,}i} < T_\mathrm{out} \text{ \& }
T_{\mathrm{in,}i} \geq T_0 \\
\sum_i \dot{m}_i \cdot e_\mathrm{out}^\mathrm{PH}
& T_{\mathrm{in,}i} < T_\mathrm{out} \text{ \& }
T_{\mathrm{in,}i} < T_0 \\
\end{cases} & T_\mathrm{out} > T_0\\
\text{not defined (nan)} & T_\mathrm{out} = T_0\\
\begin{cases}
\sum_i \dot{m}_i \cdot e_\mathrm{out}^\mathrm{PH}
& T_{\mathrm{in,}i} > T_\mathrm{out} \text{ \& }
T_{\mathrm{in,}i} \geq T_0 \\
\sum_i \dot{m}_i \cdot \left(e_\mathrm{out}^\mathrm{PH} -
e_{\mathrm{in,}i}^\mathrm{PH}\right)
& T_{\mathrm{in,}i} > T_\mathrm{out} \text{ \& }
T_{\mathrm{in,}i} < T_0 \\
\end{cases} & T_\mathrm{out} < T_0\\
\end{cases}
\dot{E}_\mathrm{F} =
\begin{cases}
\begin{cases}
\sum_i \dot{m}_i \cdot \left(e_{\mathrm{in,}i}^\mathrm{PH} -
e_\mathrm{out}^\mathrm{PH}\right)
& T_{\mathrm{in,}i} > T_\mathrm{out} \\
\sum_i \dot{E}_{\mathrm{in,}i}^\mathrm{PH}
& T_{\mathrm{in,}i} < T_\mathrm{out} \text{ \& }
T_{\mathrm{in,}i} < T_0 \\
\end{cases} & T_\mathrm{out} > T_0\\
\sum_i \dot{E}_{\mathrm{in,}i}^\mathrm{PH} & T_\mathrm{out} = T_0\\
\begin{cases}
\sum_i \dot{E}_{\mathrm{in,}i}^\mathrm{PH}
& T_{\mathrm{in,}i} > T_\mathrm{out} \text{ \& }
T_{\mathrm{in,}i} \geq T_0 \\
\sum_i \dot{m}_i \cdot \left(e_{\mathrm{in,}i}^\mathrm{PH} -
e_\mathrm{out}^\mathrm{PH}\right)
& T_{\mathrm{in,}i} < T_\mathrm{out} \\
\end{cases} & T_\mathrm{out} < T_0\\
\end{cases}
\forall i \in \text{merge inlets}
\dot{E}_\mathrm{bus} = \text{not defined (nan)}
"""
self.E_P = 0
self.E_F = 0
if self.outl[0].T.val_SI > T0:
for i in self.inl:
if i.T.val_SI < self.outl[0].T.val_SI:
if i.T.val_SI >= T0:
self.E_P += i.m.val_SI * (
self.outl[0].ex_physical - i.ex_physical)
else:
self.E_P += i.m.val_SI * self.outl[0].ex_physical
self.E_F += i.Ex_physical
else:
self.E_F += i.m.val_SI * (
i.ex_physical - self.outl[0].ex_physical)
elif self.outl[0].T.val_SI == T0:
self.E_P = np.nan
for i in self.inl:
self.E_F += i.Ex_physical
else:
for i in self.inl:
if i.T.val_SI > self.outl[0].T.val_SI:
if i.T.val_SI >= T0:
self.E_P += i.m.val_SI * self.outl[0].ex_physical
self.E_F += i.Ex_physical
else:
self.E_P += i.m.val_SI * (
self.outl[0].ex_physical - i.ex_physical)
else:
self.E_F += i.m.val_SI * (
i.ex_physical - self.outl[0].ex_physical)
self.E_bus = {
"chemical": np.nan, "physical": np.nan, "massless": np.nan
}
self.E_D = self.E_F - self.E_P
self.epsilon = self._calc_epsilon()
[docs]
def get_plotting_data(self):
"""Generate a dictionary containing FluProDia plotting information.
Returns
-------
data : dict
A nested dictionary containing the keywords required by the
:code:`calc_individual_isoline` method of the
:code:`FluidPropertyDiagram` class. First level keys are the
connection index ('in1' -> 'out1', therefore :code:`1` etc.).
"""
return {
i + 1: {
'isoline_property': 'p',
'isoline_value': self.inl[i].p.val,
'isoline_value_end': self.outl[0].p.val,
'starting_point_property': 'v',
'starting_point_value': self.inl[i].vol.val,
'ending_point_property': 'v',
'ending_point_value': self.outl[0].vol.val
} for i in range(self.num_i)}