# -*- coding: utf-8
"""Module of class Drum.
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/drum.py
SPDX-License-Identifier: MIT
"""
import numpy as np
from tespy.components.nodes.droplet_separator import DropletSeparator
from tespy.tools.fluid_properties import h_mix_pQ
[docs]
class Drum(DropletSeparator):
r"""
A drum separates saturated gas from saturated liquid.
**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.droplet_separator.DropletSeparator.fluid_func`
- :py:meth:`tespy.components.nodes.droplet_separator.DropletSeparator.energy_balance_func`
- :py:meth:`tespy.components.nodes.droplet_separator.DropletSeparator.outlet_states_func`
Inlets/Outlets
- in1, in2 (index 1: from economiser, index 2: from evaporator)
- out1, out2 (index 1: saturated liquid, index 2: saturated gas)
Image
.. image:: /api/_images/Drum.svg
:alt: flowsheet of the drum
:align: center
:class: only-light
.. image:: /api/_images/Drum_darkmode.svg
:alt: flowsheet of the drum
: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.
Note
----
If you are using a drum in a network with multiple fluids, it is likely
the fluid propagation causes trouble. If this is the case, try to
specify the fluid composition at another connection of your network.
This component assumes, that the fluid composition between outlet 1 and
inlet 2 does not change, thus there is no equation for the fluid mass
fraction at the inlet 2!
Example
-------
The drum separates saturated gas from saturated liquid. The liquid phase is
transported to an evaporator, the staturated gas phase is extracted from
the drum. In this example ammonia is evaporated using ambient air. A
characteristic function is applied for the heat transfer coefficient of the
evaporator. It is possible to load the CharLine with the function
:code:`load_default_char` from the default lines. We want to use the
'EVAPORATING FLUID' lines of the heat exchanger.
>>> from tespy.components import Sink, Source, Drum, Pump, HeatExchanger
>>> from tespy.connections import Connection, Ref
>>> from tespy.networks import Network
>>> from tespy.tools.characteristics import CharLine
>>> from tespy.tools.characteristics import load_default_char as ldc
>>> import shutil
>>> import numpy as np
>>> nw = Network(T_unit='C', p_unit='bar', h_unit='kJ / kg', iterinfo=False)
>>> fa = Source('feed ammonia')
>>> amb_in = Source('air inlet')
>>> amb_out = Sink('air outlet')
>>> s = Sink('steam')
>>> dr = Drum('drum')
>>> dr.component()
'drum'
>>> ev = HeatExchanger('evaporator')
>>> erp = Pump('evaporator reciculation pump')
>>> f_dr = Connection(fa, 'out1', dr, 'in1')
>>> dr_erp = Connection(dr, 'out1', erp, 'in1')
>>> erp_ev = Connection(erp, 'out1', ev, 'in2')
>>> ev_dr = Connection(ev, 'out2', dr, 'in2')
>>> dr_s = Connection(dr, 'out2', s, 'in1')
>>> nw.add_conns(f_dr, dr_erp, erp_ev, ev_dr, dr_s)
>>> amb_ev = Connection(amb_in, 'out1', ev, 'in1')
>>> ev_amb = Connection(ev, 'out1', amb_out, 'in1')
>>> nw.add_conns(amb_ev, ev_amb)
The ambient air enters the evaporator at 30 °C. The pinch point temperature
difference (ttd_l) of the evaporator is at 5 K, and 1 MW of heat should be
transferred. State of ammonia at the inlet is at -5 °C and 5 bar. From this
design it is possible to calculate offdesign performance at 75 % part load.
>>> char1 = ldc('heat exchanger', 'kA_char1', 'DEFAULT',
... CharLine)
>>> char2 = ldc('heat exchanger', 'kA_char2', 'EVAPORATING FLUID',
... CharLine)
>>> ev.set_attr(pr1=0.999, pr2=0.99, ttd_l=5, kA_char1=char1,
... kA_char2=char2, design=['pr1', 'ttd_l'],
... offdesign=['zeta1', 'kA_char'])
>>> ev.set_attr(Q=-1e6)
>>> erp.set_attr(eta_s=0.8)
>>> f_dr.set_attr(p=5, T=-5)
>>> erp_ev.set_attr(m=Ref(f_dr, 4, 0), fluid={'NH3': 1})
>>> amb_ev.set_attr(fluid={'air': 1}, T=30)
>>> ev_amb.set_attr(p=1)
>>> nw.solve('design')
>>> nw.save('tmp')
>>> round(ev_amb.T.val - erp_ev.T.val ,1)
5.0
>>> round(f_dr.h.val, 1)
322.7
>>> round(dr_erp.h.val, 1)
364.9
>>> round(ev_dr.h.val, 1)
687.2
>>> round(f_dr.m.val, 2)
0.78
>>> ev.set_attr(Q=-0.75e6)
>>> nw.solve('offdesign', design_path='tmp')
>>> round(f_dr.m.val, 2)
0.58
>>> round(ev_amb.T.val - erp_ev.T.val ,1)
3.0
>>> shutil.rmtree('./tmp', ignore_errors=True)
"""
[docs]
@staticmethod
def component():
return 'drum'
[docs]
@staticmethod
def inlets():
return ['in1', 'in2']
[docs]
@staticmethod
def outlets():
return ['out1', 'out2']
[docs]
def get_mandatory_constraints(self):
num_mass_eq = 1
if self.inl[1].m == self.outl[0].m:
num_mass_eq = 0
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_mass_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},
'outlet_constraints': {
'func': self.outlet_states_func,
'deriv': self.outlet_states_deriv,
'constant_deriv': False,
'latex': self.outlet_states_func_doc,
'num_eq': 2}
}
[docs]
def preprocess(self, num_nw_vars):
super().preprocess(num_nw_vars)
self._propagation_start = False
[docs]
def mass_flow_func(self):
r"""
Calculate the residual value for mass flow balance equation.
Returns
-------
res : float
Residual value of equation.
.. math::
0 = \sum \dot{m}_{in,i} - \sum \dot{m}_{out,j} \;
\forall i \in inlets, \forall j \in outlets
"""
if self.inl[1].m == self.outl[0].m:
return self.inl[0].m.val_SI - self.outl[1].m.val_SI
else:
res = 0
for i in self.inl:
res += i.m.val_SI
for o in self.outl:
res -= o.m.val_SI
return res
[docs]
def mass_flow_deriv(self, k):
r"""
Calculate partial derivatives for mass flow equation.
Returns
-------
deriv : list
Matrix with partial derivatives for the fluid equations.
"""
if self.inl[1].m == self.outl[0].m:
if self.inl[0].m.is_var:
self.jacobian[k, self.inl[0].m.J_col] = 1
if self.outl[1].m.is_var:
self.jacobian[k, self.outl[1].m.J_col] = -1
else:
for i in self.inl:
if i.m.is_var:
self.jacobian[k, i.m.J_col] = 1
for o in self.outl:
if o.m.is_var:
self.jacobian[k, o.m.J_col] = -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) -
\sum_j \left(\dot{m}_{out,j} \cdot h_{out,j} \right)\\
\forall i \in \text{inlets} \; \forall j \in \text{outlets}
"""
if self.inl[1].m == self.outl[0].m:
res = (
(self.inl[1].h.val_SI - self.outl[0].h.val_SI)
* self.outl[0].m.val_SI
+ (self.inl[0].h.val_SI - self.outl[1].h.val_SI)
* self.inl[0].m.val_SI
)
else:
res = 0
for i in self.inl:
res += i.m.val_SI * i.h.val_SI
for o in self.outl:
res -= o.m.val_SI * o.h.val_SI
return res
[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).
"""
# due to topology reduction this is the case quite often
if self.inl[1].m == self.outl[0].m:
if self.outl[0].m.is_var:
self.jacobian[k, self.outl[0].m.J_col] = (self.inl[1].h.val_SI - self.outl[0].h.val_SI)
if self.inl[1].h.is_var:
self.jacobian[k, self.inl[1].h.J_col] = self.outl[0].m.val_SI
if self.outl[0].h.is_var:
self.jacobian[k, self.outl[0].h.J_col] = -self.outl[0].m.val_SI
if self.inl[0].m.is_var:
self.jacobian[k, self.inl[0].m.J_col] = self.inl[0].h.val_SI - self.outl[1].h.val_SI
if self.inl[0].h.is_var:
self.jacobian[k, self.inl[0].h.J_col] = self.inl[0].m.val_SI
if self.outl[1].h.is_var:
self.jacobian[k, self.outl[1].h.J_col] = -self.outl[1].m.val_SI
else:
super().energy_balance_deriv(increment_filter, k)
[docs]
@staticmethod
def initialise_target(c, key):
r"""
Return a starting value for pressure and enthalpy at inlet.
Parameters
----------
c : tespy.connections.connection.Connection
Connection to perform initialisation on.
key : str
Fluid property to retrieve.
Returns
-------
val : float
Starting value for pressure/enthalpy in SI units.
.. math::
val = \begin{cases}
10^6 & \text{key = 'p'}\\
h\left(p, x=0 \right) & \text{key = 'h' at inlet 1}\\
h\left(p, x=0.7 \right) & \text{key = 'h' at inlet 2}
\end{cases}
"""
if key == 'p':
return 10e5
elif key == 'h':
if c.target_id == 'in1':
return h_mix_pQ(c.p.val_SI, 0, c.fluid_data)
else:
return h_mix_pQ(c.p.val_SI, 0.7, c.fluid_data)
[docs]
def propagate_wrapper_to_target(self, branch):
return super().propagate_wrapper_to_target(branch)
[docs]
def propagate_to_target(self, branch):
if branch["connections"][-1].target_id == "in2":
return
outconn = self.outl[0]
subbranch = {
"connections": [outconn],
"components": [self, outconn.target],
"subbranches": {}
}
outconn.target.propagate_to_target(subbranch)
branch["subbranches"][outconn.label] = subbranch
outconn = self.outl[1]
if subbranch["components"][-1] == self:
branch["connections"] += [outconn]
branch["components"] += [outconn.target]
outconn.target.propagate_to_target(branch)
else:
subbranch = {
"connections": [outconn],
"components": [self, outconn.target],
"subbranches": {}
}
outconn.target.propagate_to_target(subbranch)
branch["subbranches"][outconn.label] = subbranch
[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} = \sum \dot{E}_{\mathrm{out,}j}^\mathrm{PH}\\
\dot{E}_\mathrm{F} = \sum \dot{E}_{\mathrm{in,}i}^\mathrm{PH}
"""
self.E_P = self.outl[0].Ex_physical + self.outl[1].Ex_physical
self.E_F = self.inl[0].Ex_physical + self.inl[1].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 {
1: {
'isoline_property': 'p',
'isoline_value': self.outl[0].p.val,
'isoline_value_end': self.outl[1].p.val,
'starting_point_property': 'v',
'starting_point_value': self.outl[0].vol.val,
'ending_point_property': 'v',
'ending_point_value': self.outl[1].vol.val
}}