# -*- coding: utf-8
"""Module of class Desuperheater.
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/heat_exchangers/desuperheater.py
SPDX-License-Identifier: MIT
"""
from tespy.components.heat_exchangers.base import HeatExchanger
from tespy.tools.document_models import generate_latex_eq
from tespy.tools.fluid_properties import dh_mix_dpQ
from tespy.tools.fluid_properties import h_mix_pQ
[docs]
class Desuperheater(HeatExchanger):
r"""
The Desuperheater cools a fluid to the saturated gas state.
**Mandatory Equations**
- :py:meth:`tespy.components.heat_exchangers.base.HeatExchanger.energy_balance_func`
- :py:meth:`tespy.components.heat_exchangers.desuperheater.Desuperheater.saturated_gas_func`
**Optional Equations**
- :py:meth:`tespy.components.heat_exchangers.base.HeatExchanger.energy_balance_hot_func`
- :py:meth:`tespy.components.heat_exchangers.base.HeatExchanger.kA_func`
- :py:meth:`tespy.components.heat_exchangers.base.HeatExchanger.kA_char_func`
- :py:meth:`tespy.components.heat_exchangers.base.HeatExchanger.ttd_u_func`
- :py:meth:`tespy.components.heat_exchangers.base.HeatExchanger.ttd_l_func`
- hot side :py:meth:`tespy.components.component.Component.pr_func`
- cold side :py:meth:`tespy.components.component.Component.pr_func`
- hot side :py:meth:`tespy.components.component.Component.zeta_func`
- cold side :py:meth:`tespy.components.component.Component.zeta_func`
Inlets/Outlets
- in1, in2 (index 1: hot side, index 2: cold side)
- out1, out2 (index 1: hot side, index 2: cold side)
Image
.. image:: /api/_images/HeatExchanger.svg
:alt: flowsheet of the desuperheater
:align: center
:class: only-light
.. image:: /api/_images/HeatExchanger_darkmode.svg
:alt: flowsheet of the desuperheater
: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.
Q : float, dict
Heat transfer, :math:`Q/\text{W}`.
pr1 : float, dict, :code:`"var"`
Outlet to inlet pressure ratio at hot side, :math:`pr/1`.
pr2 : float, dict, :code:`"var"`
Outlet to inlet pressure ratio at cold side, :math:`pr/1`.
zeta1 : float, dict, :code:`"var"`
Geometry independent friction coefficient at hot side,
:math:`\frac{\zeta}{D^4}/\frac{1}{\text{m}^4}`.
zeta2 : float, dict, :code:`"var"`
Geometry independent friction coefficient at cold side,
:math:`\frac{\zeta}{D^4}/\frac{1}{\text{m}^4}`.
ttd_l : float, dict
Lower terminal temperature difference :math:`ttd_\mathrm{l}/\text{K}`.
ttd_u : float, dict
Upper terminal temperature difference :math:`ttd_\mathrm{u}/\text{K}`.
kA : float, dict
Area independent heat transfer coefficient,
:math:`kA/\frac{\text{W}}{\text{K}}`.
kA_char1 : tespy.tools.characteristics.CharLine, dict
Characteristic line for hot side heat transfer coefficient.
kA_char2 : tespy.tools.characteristics.CharLine, dict
Characteristic line for cold side heat transfer coefficient.
Note
----
The desuperheater has an additional equation for enthalpy at hot side
outlet: The fluid leaves the component in saturated gas state.
Example
-------
Overheated enthanol is cooled with water in a heat exchanger until it
reaches the state of saturated gas.
>>> from tespy.components import Sink, Source, Desuperheater
>>> from tespy.connections import Connection
>>> from tespy.networks import Network
>>> import shutil
>>> nw = Network(T_unit='C', p_unit='bar', h_unit='kJ / kg', v_unit='l / s',
... m_range=[0.001, 10], iterinfo=False)
>>> et_in = Source('ethanol inlet')
>>> et_out = Sink('ethanol outlet')
>>> cw_in = Source('cooling water inlet')
>>> cw_out = Sink('cooling water outlet')
>>> desu = Desuperheater('desuperheater')
>>> desu.component()
'desuperheater'
>>> et_de = Connection(et_in, 'out1', desu, 'in1')
>>> de_et = Connection(desu, 'out1', et_out, 'in1')
>>> cw_de = Connection(cw_in, 'out1', desu, 'in2')
>>> de_cw = Connection(desu, 'out2', cw_out, 'in1')
>>> nw.add_conns(et_de, de_et, cw_de, de_cw)
The cooling water enters the component at 15 °C. 10 l/s of ethanol is
cooled from 100 K above boiling point. The water flow rate is at 1 l/s.
Knowing the component's design parameters it is possible to predict
behavior at different inlet temperatures or different volumetric flow of
ethanol. Controlling the ethanol's state at the outlet is only possible,
if the cooling water flow rate is adjusted accordingly.
>>> desu.set_attr(pr1=0.99, pr2=0.98, design=['pr1', 'pr2'],
... offdesign=['zeta1', 'zeta2', 'kA_char'])
>>> cw_de.set_attr(fluid={'water': 1}, T=15, v=1,
... design=['v'])
>>> de_cw.set_attr(p=1)
>>> et_de.set_attr(fluid={'ethanol': 1}, Td_bp=100, v=10)
>>> de_et.set_attr(p=1)
>>> nw.solve('design')
>>> nw.save('tmp')
>>> round(de_cw.T.val, 1)
15.5
>>> round(de_et.x.val, 1)
1.0
>>> et_de.set_attr(v=12)
>>> nw.solve('offdesign', design_path='tmp')
>>> round(cw_de.v.val, 2)
1.94
>>> et_de.set_attr(v=7)
>>> nw.solve('offdesign', design_path='tmp')
>>> round(cw_de.v.val, 2)
0.41
>>> shutil.rmtree('./tmp', ignore_errors=True)
"""
[docs]
@staticmethod
def component():
return 'desuperheater'
[docs]
def get_mandatory_constraints(self):
return {
'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},
'saturated_gas_constraints': {
'func': self.saturated_gas_func,
'deriv': self.saturated_gas_deriv,
'constant_deriv': False, 'latex': self.saturated_gas_func_doc,
'num_eq': 1}
}
[docs]
def saturated_gas_func(self):
r"""
Calculate hot side outlet state.
Returns
-------
residual : float
Residual value of equation
.. math::
0 = h_{out,1} - h\left(p_{out,1}, x=1 \right)
"""
o = self.outl[0]
return o.h.val_SI - h_mix_pQ(o.p.val_SI, 1, o.fluid_data)
[docs]
def saturated_gas_func_doc(self, label):
r"""
Calculate hot side outlet state.
Parameters
----------
label : str
Label for equation.
Returns
-------
latex : str
LaTeX code of equations applied.
"""
latex = r'0=h_\mathrm{out,1}-h\left(p_\mathrm{out,1}, x=1 \right)'
return generate_latex_eq(self, latex, label)
[docs]
def saturated_gas_deriv(self, increment_filter, k):
r"""
Partial derivatives of saturated gas at hot side outlet function.
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]
if self.is_variable(o.p):
self.jacobian[k, o.p.J_col] = -dh_mix_dpQ(o.p.val_SI, 1, o.fluid_data)
if self.is_variable(o.h):
self.jacobian[k, o.h.J_col] = 1