Pipe¶

class pygld.Pipe(di, do, material=None)¶

The Pipe class holds the geometry and material properties of the pipes used in the construction of ground-loop heat exchangers. The inner and outer diameters of the pipe in cm must be passed as arguments when instantiating Pipe. These values can afterward be accessed or changed with the di and do properties

The thermophysical properties of the pipe are held in a PipeMaterial object that can be accessed with the material property or set with set_material(). The optional argument ‘material’ can be used to pass a custom PipeMaterial when instantiating a Pipe. If no PipeMaterial is provided when instantiating Pipe, the pipe’s material will be set to that of a standard HDPE pipe by default, with a thermal conductivity of 0.4 W/m·k and a volumetric heat capacity of 1500 J/m³·K. These values can be changed afterward by setting directly the properties PipeMaterial.kth and PipeMaterial.Cp of the pipe’s material.

An Example is available at the end of this section.

Geometry¶

Pipe.di¶

Inner diameter of the pipe in cm.

Get or set the inner diameter of the pipe as a single positive float value.

Pipe.do¶

Outer diameter of the pipe in cm.

Get or set the outer diameter of the pipe as a single positive float value.

Pipe.wt¶

Return the pipe wall thickness in cm calculated as:

$wt = (do - di) / 2$

where $do$ and $di$ are, respectively, the outer and inner diameter of the pipe in cm.

Pipe.Ai¶

Return the inner area of the pipe in cm² calculated as:

$Ai = \frac{\pi \cdot di^2}{4}$

where $di$ is the inner diameter of the pipe.

Pipe.Ao¶

Return the inner area of the pipe in cm² calculated as:

$Ao = \frac{\pi \cdot do^2}{4}$

where $do$ is the outer diameter of the pipe.

Material and thermal resistance¶

Pipe.material¶: Return the PipeMaterial of the pipe.

Pipe.set_material(material)¶: Set the PipeMaterial of the pipe.

Pipe.Rcond¶

Return the conductive thermal resistance of the pipe in m·K/W calculated as:

$Rcond = \frac{ln(do/di)}{2 \cdot \pi \cdot kth}$

where $di$ and $do$ are, repectively, the inner and outer diameter of the pipe in m and $kth$ is its thermal conductivity in W/m·k.

References¶

Pipe conductive thermal resistance :

Hellström, G. 1991. Ground Heat Storage - Thermal Analyses of Duct: Storage Systems. Ph.D. thesis. University of Lund. Department of mathematical physics, Lund, Sweden. Eq.8.2, p.75.

Example¶

Import and instantiate the HeatPump class:

>>> from pygld import Pipe
>>> pipe = Pipe(di=3.39852, do=4.2164)
>>> print(pipe)
Inner diameter: 3.40 cm
Outer diameter: 4.22 cm
Wall thickness: 0.41 cm
Inner area: 9.07 cm²
Outer area: 13.96 cm²
Pipe material: HDPE
Thermal conductivity: 0.400 W/m·k
Volumetric heat capacity: 1500 J/m³·K
Thermal diffusivity: 2.67e-04 m²/s
Conductive thermal resistance: 0.08580 m·K/W

Change and print the thermal properties of the pipe. This must be done through the pipe’s material as:

>>> pipe.material.kth = 0.43
>>> pipe.material.Cp = 0.1540
>>> print(pipe.material)
Pipe material: User Defined
Thermal conductivity: 0.430 W/m·k
Volumetric heat capacity: 1540 J/m³·K
Thermal diffusivity: 2.79e-04 m²/s