Pipe¶
Create Function¶

create_pipe
(net, from_junction, to_junction, std_type, length_km, k_mm=1, loss_coefficient=0, sections=1, alpha_w_per_m2k=0.0, text_k=293, qext_w=0.0, name=None, index=None, geodata=None, in_service=True, type='pipe', **kwargs)¶ Creates a pipe element in net[“pipe”] from pipe parameters.
 Parameters
net (pandapipesNet) – The net for which this pipe should be created
from_junction (int) – ID of the junction on one side which the pipe will be connected to
to_junction (int) – ID of the junction on the other side which the pipe will be connected to
std_type (str) – Name of standard type
length_km (float) – Length of the pipe in [km]
k_mm (float, default 1) – Pipe roughness in [mm]
loss_coefficient (float, default 0) – An additional pressure loss coefficient, introduced by e.g. bends
sections (int, default 1) – The number of internal pipe sections. Important for gas and temperature calculations, where variables are dependent on pipe length.
alpha_w_per_m2k (float, default 0) – Heat transfer coefficient in [W/(m^2*K)]
name (str, default None) – A name tag for this pipe
index (int, default None) – Force a specified ID if it is available. If None, the index one higher than the highest already existing index is selected.
geodata (array, shape = (,2L), default None) – The coordinates of the pipe. The first row should be the coordinates of junction a and the last should be the coordinates of junction b. The points in the middle represent the bending points of the pipe.
in_service (bool, default True) – True for in service, False for out of service
type (str, default "pipe") – An identifier for special types of pipes (e.g. below or above ground)
qext_w (float, default 0) – External heat feedin to the pipe in [W]
text_k (float, default 293) – Ambient temperature of pipe in [K]
kwargs – Additional keyword arguments will be added as further columns to the net[“pipe”] table
 Returns
index  The unique ID of the created element
 Return type
int
 Example
>>> create_pipe(net,from_junction=0,to_junction=1,std_type='315_PE_80_SDR_17',length_km=1)
Component Table Data¶
net.pipe
Parameter 
Datatype 
Value Range 
Explanation 
name 
string 
Name of the pipe 

from_junction 
integer 
\(>\) 0 
Index of junction at which the pipe starts 
to_junction 
integer 
\(>\) 0 
Index of junction at which the pipe ends 
std_type 
string 
A selected std type for the pipe 

length_km 
float 
\(>\) 0 
Length of the pipe [km] 
diameter_m 
float 
\(\gt\) 0 
Inner diameter of the pipe [m] 
k_mm 
float 
\(\gt\) 0 
Pipe roughness [mm] 
loss_coefficient 
float 
\(\geq\) 0 
An additional loss coefficient which might account for e.g. bends 
alpha_w_per_m2k 
float 
\(\geq\) 0 
Heat transfer coefficient [W/(m^2K)] 
qext_w 
float 
\(>\) 0 
An additional heat flow entering or leaving the pipe [W] 
text_k 
float 
\(>\) 0 
The ambient temperature used for calculating heat losses [K] 
sections 
integer 
\(\geq\) 1 
The number of internal pipe sections 
in_service 
boolean 
True / False 
Specifies if the line is in service. 
type 
string 
Type variable to classify junctions 
net.pipe_geodata
Parameter 
Datatype 
Explanation 
coords 
list 
List of (x,y) tuples that mark the inflexion points of the pipe 
Physical Model¶
For both the hydraulic and temperature calculation mode, the main function of the pipe element is to calculate pressure and heat losses, respectively.
Hydraulic mode¶
The following image shows the implemented pipe model with relevant quantities of the hydraulic calculations:
Losses are calculated in different ways for incompressible and compressible media. Please also note that for an incompressible fluid, the velocity along the pipe is constant. This is not the case for compressible fluids.
Incompressible media¶
The pressure loss for incompressible media is calculated according to the following formula:
Compressible media¶
For compressible media, the density is expressed with respect to a reference state using the law of ideal gases:
As reference state variables, the normal temperature and pressure are used by pandapipes. With this relation, also the pipe velocity can be expressed using reference values:
Inserting the equations from above in the differential equation for describing the pressure drop along a pipe results in the following formula, which is used by pandapipes to calculate the pressure drop for compressible media:
The equation for pressure drop also introduces a variable K. This is the compressibility factor, which is used to account for real gas behaviour.
After calculating the gas network, the pressure losses and velocities for the reference state are known. During post processing, the reference velocities are recalculated according to
The equations from above were implemented following [Eberhard1990].
Because the velocity of a compressible fluid changes along the pipe axis, it is possible to split a pipe into several sections, increasing the internal resolution. The parameter sections is used to increase the amount of internal pipe sections.
Friction models¶
Three friction models are used to calculate the velocity dependent friction factor:
Nikuradse
PrandtlColebrook
SwameeJain
Nikuradse is chosen by default. In this case, the friction factor is calculated by:
Note that in literature, Nikuradse is known as a model for turbulent flows. In pandapipes, the formula for the Nikuradse model is also applied for laminar flow.
If PrandtlColebrook is selected, the friction factor is calculated iteratively according to
Equations for pressure losses due to friction were taken from [Eberhard1990] and [Cerbe2008].
The equation according to SwameeJain [Swamee1976] is an approximation of the calculation method according to PrandtlColebrook. It is an explicit formula for the friction factor of the transition zone of turbulent flows in pipes and is defined as follows:
Heat transfer mode¶
The following image shows the implemented pipe model with relevant quantities of the heat transfer calculations:
For heat transfer, two effects are considered by the pipe element:
The heat loss due to a temperature difference between the pipe medium and the surrounding temperature is calculated
An additional heat in or outflow can be specified by the user
The heat losses are described by
according to [Baehr2010]. If the default value of the sections parameter is changed, the resolution of temperature values can be increased.
Result Table Data¶
For incompressible media:
net.res_pipe
Parameter 
Datatype 
Explanation 
v_mean_m_per_s 
float 
The mean pipe velocity [m/s] 
p_from_bar 
float 
Pressure at “from”junction [bar] 
p_to_bar 
float 
Pressure at “to”junction [bar] 
t_from_k 
float 
Temperature at “from”junction [K] 
t_to_k 
float 
Temperature at “to”junction [K] 
mdot_from_kg_per_s 
float 
Mass flow into pipe [kg/s] 
mdot_to_kg_per_s 
float 
Mass flow out of pipe [kg/s] 
vdot_norm_m3_per_s 
float 
Norm volume flow [m^3/s] 
reynolds 
float 
Average Reynolds number 
lambda 
float 
Average pipe friction factor 
For compressible media:
net.res_pipe
Parameter 
Datatype 
Explanation 
v_from_m_per_s 
float 
The velocity at the pipe entry [m/s] 
v_to_m_per_s 
float 
The velocity at the pipe exit [m/s] 
v_mean_m_per_s 
float 
The mean pipe velocity [m/s] 
p_from_bar 
float 
Pressure at “from”junction [bar] 
p_to_bar 
float 
Pressure at “to”junction [bar] 
t_from_k 
float 
Temperature at “from”junction [K] 
t_to_k 
float 
Temperature at “to”junction [K] 
mdot_from_kg_per_s 
float 
Mass flow into pipe [kg/s] 
mdot_to_kg_per_s 
float 
Mass flow out of pipe [kg/s] 
vdot_norm_m3_per_s 
float 
Norm volume flow [m^3/s] 
reynolds 
float 
Average Reynolds number 
lambda 
float 
Average pipe friction factor 
normfactor_from 
float 
Normfactor to calculate real gas velocity at “from”junction (only for gas flows) 
normfactor_to 
float 
Normfactor to calculate real gas velocity at “to”junction (only for gas flows) 