tespy.components.piping package

tespy.components.piping.pipe module

Module of class Pipe.

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/piping/pipe.py

SPDX-License-Identifier: MIT

class tespy.components.piping.pipe.Pipe(label, **kwargs)

Bases: SimpleHeatExchanger

The Pipe is a subclass of a SimpleHeatExchanger.

There are two different types of pipes available: An at the surface and a subsurface buried pipe. The implementation is based on [38] (surface) and [39] (subsurface).

Ports

• Fluid inlets: in1

• Fluid outlets: out1

• Power inlets: heat

• Power outlets: heat

• Heat inlets: heat

• Heat outlets: heat

Mandatory Equations

• mass flow equality constraint(s): variable_equality_structure_matrix

• fluid composition equality constraint(s): variable_equality_structure_matrix

When a power or heat connector is attached:

• energy_connector_balance: energy_connector_balance_func

Parameters:

• char_warnings (bool) – Ignore warnings on default characteristics usage for this component.

• D (float, dict, "var") – Diameter of channel. Quantity: length. Can be set as a system variable by passing "var" as its value.

• darcy_group (GroupedComponentProperties) – Darcy-Weißbach equation for pressure loss. Elements: L, ks, D. Equation: darcy_func.

• design (list) – List containing design parameters (stated as String).

• design_path (str) – Path to the components design case.

• dissipative (bool) – Description missing.

• dp (float, dict) – Inlet to outlet absolute pressure change. Quantity: pressure_difference. Equation: dp_structure_matrix.

• environment_media (str) – Description missing.

• flow_speed (float, dict) – Flow speed at inlet of pipe. Quantity: speed.

• flow_speed_group (GroupedComponentProperties) – Equation connecting volumetric flow, flow speed and diameter of pipe. Elements: D, flow_speed. Equation: flow_speed_func.

• hw_group (GroupedComponentProperties) – Hazen-Williams equation for pressure loss. Elements: L, ks_HW, D. Equation: hazen_williams_func.

• insulation_tc (float, dict) – Thermal conductivity of insulation. Quantity: thermal_conductivity.

• insulation_thickness (float, dict) – Thickness of pipe insulation. Quantity: length.

• kA (float, dict, "var") – Deprecated, use UA instead. Quantity: heat_transfer_coefficient. Can be set as a system variable by passing "var" as its value.

• kA_char (tespy.tools.characteristics.CharLine, dict) – Deprecated, use UA_char instead.

• kA_char_group (GroupedComponentProperties) – Deprecated, use UA_char_group instead. Elements: kA_char, Tamb.

• kA_group (GroupedComponentProperties) – Deprecated, use UA_group instead. Elements: kA, Tamb.

• ks (float, dict, "var") – Roughness of wall material. Quantity: length. Can be set as a system variable by passing "var" as its value.

• ks_HW (float, dict, "var") – Hazen-Williams roughness. Can be set as a system variable by passing "var" as its value.

• L (float, dict, "var") – Length of channel. Quantity: length. Can be set as a system variable by passing "var" as its value.

• label (str) – The label of the component.

• lmtd (float, dict) – Effective logarithmic mean temperature difference Q/UA. Quantity: temperature_difference.

• local_design (bool) – Treat this component in design mode in an offdesign calculation.

• local_offdesign (bool) – Treat this component in offdesign mode in a design calculation.

• material (str) – Description missing.

• offdesign (list) – List containing offdesign parameters (stated as String).

• pipe_depth (float, dict) – Depth of buried pipe. Quantity: length.

• pipe_thickness (float, dict) – Wall thickness of pipe. Quantity: length.

• power_connector_location (str) – Description missing.

• pr (float, dict) – Outlet to inlet pressure ratio. Quantity: ratio. Equation: pr_structure_matrix.

• printout (bool) – Include this component in the network’s results printout.

• Q (float, dict) – Heat transfer. Quantity: heat. Equation: energy_balance_func.

• Q_ohc_group_subsurface (GroupedComponentProperties) – Equation for heat loss of buried pipes. Elements: insulation_thickness, insulation_tc, Tamb, material, pipe_thickness, environment_media, pipe_depth. Equation: ohc_subsurface_group_func.

• Q_ohc_group_surface (GroupedComponentProperties) – Equation for heat loss of surface pipes. Elements: insulation_thickness, insulation_tc, Tamb, material, pipe_thickness, environment_media, wind_velocity. Equation: ohc_surface_group_func.

• Tamb (float, dict) – Ambient temperature. Quantity: temperature.

• UA (float, dict, "var") – Heat transfer coefficient considering ambient temperature. Quantity: heat_transfer_coefficient. Can be set as a system variable by passing "var" as its value.

• UA_char (tespy.tools.characteristics.CharLine, dict) – Heat transfer coefficient lookup table for offdesign.

• UA_char_group (GroupedComponentProperties) – Heat transfer from design heat transfer coefficient, modifier lookup table and ambient temperature. Elements: UA_char, Tamb. Equation: UA_char_group_func.

• UA_group (GroupedComponentProperties) – Equation for heat transfer based on ambient temperature and heat transfer coefficient. Elements: UA, Tamb. Equation: UA_group_func.

• wind_velocity (float, dict) – Velocity of wind at insulation surface. Quantity: speed.

• zeta (float, dict) – Deprecated, use zeta_d4 instead.

• zeta_d4 (float, dict) – Geometry-independent friction coefficient zeta/D^4 for pressure loss calculation. Equation: zeta_d4_func.

Example

A mass flow of 10 kg/s hot ethanol is transported in a pipeline. The pipe is considered adiabatic, in the first approach and has a length of 100 meters. We can calculate the diameter required at a given pressure loss of 2.5 %. After we determined the required diameter, we can predict pressure loss at a different mass flow through the pipeline. Afterwards heat losses can be calculated by defining insulation and environment parameters. The heat losses of a subsurface pipe can be compared to heat losses of a surface pipe.

>>> from tespy.components import Sink, Source, Pipe
>>> from tespy.connections import Connection
>>> from tespy.networks import Network
>>> nw = Network(iterinfo=False)
>>> nw.units.set_defaults(**{
...     "pressure": "bar", "pressure_difference": "bar",
...     "temperature": "degC", "enthalpy": "kJ/kg"
... })
>>> so = Source("source 1")
>>> si = Sink("sink 1")
>>> pi = Pipe("pipeline")
>>> pi.set_attr(pr=0.975, Q=0, L=100, D="var", ks=5e-5)
>>> inc = Connection(so, "out1", pi, "in1")
>>> outg = Connection(pi, "out1", si, "in1")
>>> nw.add_conns(inc, outg)
>>> inc.set_attr(fluid={"ethanol": 1}, m=10, T=30, p=3)
>>> nw.solve("design")
>>> round(pi.D.val, 3)
0.119
>>> round(outg.p.val / inc.p.val, 3) == round(pi.pr.val, 3)
True
>>> inc.set_attr(m=15)
>>> pi.set_attr(pr=None)
>>> pi.set_attr(D=pi.D.val)
>>> nw.solve("design")
>>> round(pi.pr.val, 2)
0.94

In the second section the example shows how to calculate the heat losses of the pipe to the ambient considering insulation. For this, we will look at a pipe transporting hot water. Since we change the fluid, we should also give a reasonable guess value for the outflow connection of the pipe as the initial guess originates from the previous calculation using ethanol as fluid.

>>> inc.set_attr(fluid={"water": 1, "ethanol": 0}, T=100)
>>> outg.set_attr(h0=300)
>>> pi.set_attr(
...     D="var", Q=None, pr=0.975,
...     Tamb=0, environment_media="dry soil", pipe_depth=5,
...     insulation_thickness=0.1, insulation_tc=0.035,
...     pipe_thickness=0.003, material="Steel"
... )
>>> nw.solve("design")
>>> round(pi.Q.val, 2)
-1780.74

We can reuse many of the given parameters of the pipe. By unsetting the pipe”s depth and setting the environment media and wind velocity instead the analogous method for surface pipes is applied. Observe, how the overall heat loss increases.

>>> pi.Q_ohc_group_subsurface.is_set = False
>>> pi.set_attr(
...     pipe_depth=None, environment_media="air", wind_velocity=2.0
... )
>>> nw.solve("design")
>>> round(pi.Q.val, 2)
-2434.12

flow_speed_dependents()

flow_speed_func()

Heat transfer calculation based on pipe material, insulation and surrounding ambient conditions for subsurface pipes.

Returns:

float – Residual value of equation

\[0 = c \cdot \pi \cdot D ^ 2 - \dot m \cdot v_\text{in} * 4\]

get_parameters()

ohc_subsurface_group_dependents()

ohc_subsurface_group_func()

Heat transfer calculation based on pipe material, insulation and surrounding ambient conditions for subsurface pipes.

Returns:

float – Residual value of equation

\[0 = \dot m \cdot \left(h_\text{out}-h_\text{in}\right)- \Delta T_\text{log} \cdot A \cdot U\]

First order approximation of multipole method for a single pipe in the ground.

Reference: [39]

ohc_surface_group_dependents()

ohc_surface_group_func()

Heat transfer calculation based on pipe material, insulation and surrounding ambient conditions fur surface pipes. Valid for forced convection.

Returns:

• float – Residual value of equation

  \[ \begin{align}\begin{aligned}0 = \dot m \cdot \left(h_\text{out}-h_\text{in}\right)- \Delta T_\text{log} \cdot A \cdot U\\U = R_\text{conductance} + \frac{1}{\alpha_\text{outer}}\\\alpha_\text{outer} = \frac{Nu_\text{l} \cdot \lambda}{l}\\Nu_\text{l}= 0.3 + \sqrt{Nu_\text{l, lam}^{2} + Nu_\text{l, turb}^{2}}\\Nu_\text{l, turb} = \frac{0.037 Re_l^{0.8} \cdot Pr}{1+2.443 \cdot Re_l^{-0.1}\cdot (Pr^{2/3}-1)}\\Nu_\text{l, lam} = 0.664 \sqrt{Re_l}\cdot \sqrt[3]{Pr}\end{aligned}\end{align} \]

• Reference ([38])

tespy.components.piping.valve module

Module of class Valve.

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/piping.py

SPDX-License-Identifier: MIT

class tespy.components.piping.valve.Valve(label, **kwargs)

Bases: Component

The Valve throttles a fluid without changing enthalpy.

Ports

• Fluid inlets: in1

• Fluid outlets: out1

Mandatory Equations

• mass flow equality constraint(s): variable_equality_structure_matrix

• fluid composition equality constraint(s): variable_equality_structure_matrix

• equation for enthalpy equality: variable_equality_structure_matrix

Parameters:

• char_warnings (bool) – Ignore warnings on default characteristics usage for this component.

• design (list) – List containing design parameters (stated as String).

• design_path (str) – Path to the components design case.

• dp (float, dict) – Inlet to outlet absolute pressure change. Quantity: pressure_difference. Equation: dp_structure_matrix.

• dp_char (tespy.tools.characteristics.CharLine, dict) – Inlet to outlet absolute pressure change as function of mass flow lookup table. Equation: dp_char_func.

• Kv (float, dict) – Flow coefficient in m3/h. Equation: Kv_func.

• Kv_analytical (dict) – Fitting parameters and method for the analytical Kv evaluation provided in a dictionary with keys ‘method’ (callable) and ‘params’ (list).

• Kv_char (tespy.tools.characteristics.CharLine, dict) – Lookup-table data for flow coefficient as function of opening.

• Kv_char_analytical_group (GroupedComponentProperties) – Elements: Kv_analytical, opening. Equation: Kv_char_analytical_func.

• Kv_char_group (GroupedComponentProperties) – Equation for flow coefficient over opening. Elements: Kv_char, opening. Equation: Kv_char_func.

• label (str) – The label of the component.

• local_design (bool) – Treat this component in design mode in an offdesign calculation.

• local_offdesign (bool) – Treat this component in offdesign mode in a design calculation.

• offdesign (list) – List containing offdesign parameters (stated as String).

• opening (float, dict, "var") – Opening ratio of the valve. Quantity: ratio. Can be set as a system variable by passing "var" as its value.

• pr (float, dict) – Outlet to inlet pressure ratio. Quantity: ratio. Equation: pr_structure_matrix.

• printout (bool) – Include this component in the network’s results printout.

• zeta (float, dict) – Deprecated, use zeta_d4 instead.

• zeta_d4 (float, dict) – Geometry-independent friction coefficient zeta/D^4 for pressure loss calculation. Equation: zeta_d4_func.

Example

A mass flow of 1 kg/s methane is throttled from 80 bar to 15 bar in a valve. The inlet temperature is at 50 °C. It is possible to determine the outlet temperature as the throttling does not change enthalpy.

>>> from tespy.components import Sink, Source, Valve
>>> from tespy.connections import Connection
>>> from tespy.networks import Network
>>> nw = Network(iterinfo=False)
>>> nw.units.set_defaults(**{
...     "pressure": "bar", "pressure_difference": "bar",
...     "temperature": "degC"
... })
>>> so = Source('source')
>>> si = Sink('sink')
>>> v = Valve('valve')
>>> so_v = Connection(so, 'out1', v, 'in1')
>>> v_si = Connection(v, 'out1', si, 'in1')
>>> nw.add_conns(so_v, v_si)
>>> v.set_attr(offdesign=['zeta_d4'])
>>> so_v.set_attr(fluid={'CH4': 1}, m=1, T=50, p=80, design=['m'])
>>> v_si.set_attr(p=15)
>>> nw.solve('design')
>>> design_state = nw.save(as_dict=True)
>>> round(v_si.T.val, 1)
26.3
>>> round(v.pr.val, 3)
0.188

The simulation determined the area independent zeta_d4 value \(\frac{\zeta}{D^4}\). This value remains constant if the cross sectional area of the valve opening does not change. Using zeta_d4 we can determine the pressure ratio at a different feed pressure.

>>> so_v.set_attr(p=70)
>>> nw.solve('offdesign', design_path=design_state)
>>> round(so_v.m.val, 1)
0.9
>>> round(v_si.T.val, 1)
30.0

You can also specify the flow coefficient of the valve Kv which is used in context of liquids. For this there are several methods available:

• direct specification with Kv

• lookup table specification \(Kv=f\left(opening\right)\) with Kv_char and opening

• arbitrary function specification \(Kv=f\left(opening, params\right)\) with Kv_analytical and opening

>>> nw = Network(iterinfo=False)
>>> nw.units.set_defaults(**{
...     "pressure": "bar", "pressure_difference": "bar",
...     "temperature": "degC"
... })
>>> so = Source('source')
>>> si = Sink('sink')
>>> v = Valve('valve')
>>> so_v = Connection(so, 'out1', v, 'in1')
>>> v_si = Connection(v, 'out1', si, 'in1')
>>> nw.add_conns(so_v, v_si)
>>> so_v.set_attr(fluid={'water': 1}, T=50, p=5)
>>> v_si.set_attr(p=4)

First we specify Kv:

>>> v.set_attr(Kv=10)
>>> nw.solve('design')
>>> round(so_v.v.val, 4)
0.0028

Then, for example an analytical function:

>>> def analytical(opening, *params):
...     return params[0] * opening
>>> v.set_attr(
...     Kv=None,
...     opening=0.5,
...     Kv_analytical={"method": analytical, "params": [10]}
... )
>>> nw.solve("design")
>>> round(v.Kv.val_SI, 1)
5.0

Or, use the Kv_char, which is a CharLine instance:

>>> from tespy.tools import CharLine
>>> kv_data = np.array([
...     0.09,0.63,1.1,2.1,3.1,4.2,5.2,6.2,7.2,8.2,9.2,10.3,11.3
... ])
>>> opening_data = np.array([0,5,10,20,30,40,50,60,70,80,90,100,110]) / 100
>>> Kv_char = {
...     "char_func": CharLine(x=opening_data, y=kv_data) , "is_set": True
... }
>>> v.set_attr(Kv_char=Kv_char, Kv_analytical=None)
>>> nw.solve("design")
>>> round(v.Kv.val, 1)
5.2

Kv_char_analytical_dependents()

Kv_char_analytical_func()

Equation for Kv characteristic of a Valve opening \(K_v=f\left(opening\right)\)

Kv is determined from the method supplied by the user in the Kv_analytical specification and the additional parameters next to the opening. The method must accept parameters in the following way: method(opening, *params)

\[K_v=\dot V \cdot \sqrt{\frac{\rho}{1000\cdot \Delta p}}\]

The residual is reformulated as below:

Returns:

float – Residual value of equation.

\[0=K_v ^ 2 \cdot \frac{\Delta p}{100} -\frac{\left(3600 \cdot \dot m \right) ^ 2}{\rho}\]

Kv_char_dependents()

Kv_char_func()

Equation for Kv characteristic of a Valve opening \(K_v=f\left(opening\right)\)

Kv is determined from the degree of opening with a lookup table, the Kv equation is then applied:

\[K_v=\dot V \cdot \sqrt{\frac{\rho}{1000\cdot \Delta p}}\]

The residual is reformulated as below:

Returns:

float – Residual value of equation.

\[0=K_v ^ 2 \cdot \frac{\Delta p}{100} -\frac{\left(3600 \cdot \dot m \right) ^ 2}{\rho}\]

Kv_dependents()

Kv_func()

Equation for Kv value of a Valve

The equation is as follows:

\[K_v=\dot V \cdot \sqrt{\frac{\rho}{1000\cdot \Delta p}}\]

The residual is reformulated as below:

Returns:

float – Residual value of equation.

\[0=K_v ^ 2 \cdot \frac{\Delta p}{100} -\frac{\left(3600 \cdot \dot m \right) ^ 2}{\rho}\]

dp_char_dependents()

dp_char_func()

Equation for characteristic line of difference pressure to mass flow.

Returns:

float – Residual value of equation.

\[0=p_\text{in}-p_\text{out}-f\left( expr \right)\]

entropy_balance()

Calculate entropy balance of a valve.

Note

The entropy balance makes the following parameter available:

\[\begin{split}\text{S\_irr}=\dot{m} \cdot \left(s_\text{out}-s_\text{in} \right)\\\end{split}\]

get_bypass_constraints()

get_mandatory_constraints()

get_parameters()

get_plotting_data()

Generate a dictionary containing FluProDia plotting information.

Returns:

data (dict) – A nested dictionary containing the keywords required by the calc_individual_isoline method of the FluidPropertyDiagram class. First level keys are the connection index (‘in1’ -> ‘out1’, therefore 1 etc.).

static inlets()

static outlets()