Ground Material¶

class pygld.GroundMaterial(kth=None, Cp=None)¶

The GroundMaterial class holds all the thermophysical properties relative to the ground that are required for the modeling of ground-loop heat exchanger systems.

A database of predefined ground materials is available and can be obtained or printed with the get_predefined_materials() and print_predefined_materials() methods. The GroundMaterial can be initialized directly from a predefined material with the init_as(), passing as argument the index of the material in the database.

An Example is available at the end of this section.

Thermal Properties¶

GroundMaterial.Cp¶

Volumetric heat capacity in J/m³·K.

Get or set the volumetric heat capacity of the material as a single positive float value.

GroundMaterial.kth¶

Thermal conductivity in W/m·K.

Get or set the thermal conductivity of the material as a single positive float value.

GroundMaterial.al¶

Thermal diffusivity in m²/s.

Return the thermal diffusivity of the material as a single positive float value calculated as:

$al[i] = \frac{kth[i]}{cp[i] \cdot rho[i]}$

where $kth$ is the thermal conductivity in W/m·k and $Cp$ is the volumetric heat capacity of the material in J/m³·K.

Utilities¶

classmethod GroundMaterial.get_predefined_materials()¶: Return a dict containing the predefined GroundMaterial.

classmethod GroundMaterial.print_predefined_materials(end='\n')¶: Print the predefined GroundMaterial.

classmethod GroundMaterial.init_as(material_index)¶

Initialize the thermal properties of the GroundMaterial based on the specified material index.

This is a convenience function; the member variables can also be initialized manually.

Example¶

Import and print the list of predefined GroundMaterial:

>>> from pygld import GroundMaterial
>>> GroundMaterial.print_predefined_materials()
Predefined materials for the 'Ground':
- Amphibolite ........ kth=2.900 W/m·k, Cp=2600 J/m³·K
- Andesite ........... kth=2.200 W/m·k, Cp=2400 J/m³·K
- Anhydrite .......... kth=4.100 W/m·k, Cp=2000 J/m³·K
- Aplite ............. kth=3.100 W/m·k, Cp=2400 J/m³·K
- Arkose ............. kth=2.900 W/m·k, Cp=2000 J/m³·K
- Basalt ............. kth=1.700 W/m·k, Cp=2400 J/m³·K
- Breccia ............ kth=2.800 W/m·k, Cp=2100 J/m³·K
- Clay, dry .......... kth=0.400 W/m·k, Cp=1600 J/m³·K
- Clay, moist ........ kth=1.600 W/m·k, Cp=2400 J/m³·K
- Claystone .......... kth=2.200 W/m·k, Cp=2300 J/m³·K
- Coal ............... kth=0.300 W/m·k, Cp=1800 J/m³·K
- Concrete ........... kth=1.600 W/m·k, Cp=1800 J/m³·K
- Conglomerate ....... kth=2.800 W/m·k, Cp=2100 J/m³·K
- Diorite ............ kth=2.600 W/m·k, Cp=2900 J/m³·K
- Dolomite ........... kth=3.200 W/m·k, Cp=2500 J/m³·K
- Dunite ............. kth=4.200 W/m·k, Cp=2900 J/m³·K
- Eclogite ........... kth=2.900 W/m·k, Cp=3100 J/m³·K
- Gabbro ............. kth=1.900 W/m·k, Cp=2600 J/m³·K
- Gneiss ............. kth=2.900 W/m·k, Cp=2100 J/m³·K
- Granite ............ kth=3.400 W/m·k, Cp=2400 J/m³·K
- Granodiorite ....... kth=3.300 W/m·k, Cp=2600 J/m³·K
- Gravel, dry ........ kth=0.400 W/m·k, Cp=1500 J/m³·K
- Gravel, saturated .. kth=1.800 W/m·k, Cp=2400 J/m³·K
- Gypsum ............. kth=1.600 W/m·k, Cp=2000 J/m³·K
- Gyttja (sapropel) .. kth=0.600 W/m·k, Cp=2000 J/m³·K
- Ice ................ kth=2.200 W/m·k, Cp=1900 J/m³·K
- Ignimbrite ......... kth=3.000 W/m·k, Cp=2100 J/m³·K
- Lamprophyre ........ kth=2.600 W/m·k, Cp=2100 J/m³·K
- Limestone, massive . kth=2.800 W/m·k, Cp=2300 J/m³·K
- Limestone, marly ... kth=2.200 W/m·k, Cp=2300 J/m³·K
- Limestone, oolitic . kth=2.400 W/m·k, Cp=2300 J/m³·K
- Marble ............. kth=2.600 W/m·k, Cp=2000 J/m³·K
- Marl ............... kth=2.100 W/m·k, Cp=2300 J/m³·K
- Marl, clayey ....... kth=2.000 W/m·k, Cp=2200 J/m³·K
- Marl, dolomitic .... kth=2.200 W/m·k, Cp=2300 J/m³·K
- Metaquartzite ...... kth=5.800 W/m·k, Cp=2100 J/m³·K
- Micashist .......... kth=2.000 W/m·k, Cp=2200 J/m³·K
- Peat ............... kth=0.400 W/m·k, Cp=2200 J/m³·K
- Pegmatite .......... kth=3.000 W/m·k, Cp=2100 J/m³·K
- Peridotite ......... kth=4.000 W/m·k, Cp=2700 J/m³·K
- Quartzite .......... kth=6.000 W/m·k, Cp=2100 J/m³·K
- Rhyolite ........... kth=3.300 W/m·k, Cp=2100 J/m³·K
- Salt ............... kth=5.400 W/m·k, Cp=1200 J/m³·K
- Sand, dry .......... kth=0.400 W/m·k, Cp=1400 J/m³·K
- Sand, dry, compacted kth=1.200 W/m·k, Cp=1700 J/m³·K
- Sand, moist ........ kth=1.000 W/m·k, Cp=1800 J/m³·K
- Sand, saturated .... kth=2.400 W/m·k, Cp=2500 J/m³·K
- Sand, frozen ....... kth=2.000 W/m·k, Cp=1500 J/m³·K
- Sandstone .......... kth=2.300 W/m·k, Cp=2000 J/m³·K
- Serpentinite ....... kth=3.000 W/m·k, Cp=2200 J/m³·K
- Shale .............. kth=2.100 W/m·k, Cp=2300 J/m³·K
- Silt, dry .......... kth=0.400 W/m·k, Cp=1600 J/m³·K
- Silt, moist ........ kth=1.800 W/m·k, Cp=2200 J/m³·K
- Siltstone .......... kth=2.400 W/m·k, Cp=2300 J/m³·K
- Syenite ............ kth=2.600 W/m·k, Cp=2400 J/m³·K
- Till (moraine) ..... kth=2.000 W/m·k, Cp=2100 J/m³·K
- Tonalite ........... kth=2.700 W/m·k, Cp=2400 J/m³·K
- Trachyte ........... kth=2.800 W/m·k, Cp=2100 J/m³·K
- Tuff ............... kth=1.100 W/m·k, Cp=1100 J/m³·K
- Water .............. kth=0.600 W/m·k, Cp=4200 J/m³·K

Initialize GroundMaterial from the predefined material at index #14 and print the results:

>>> ground = GroundMaterial.init_as(14)
>>> print(ground)
Ground material: Dolomite
Thermal conductivity: 3.200 W/m·k
Volumetric heat capacity: 2500 J/m³·K
Thermal diffusivity: 1.28e-03 m²/s

Change the thermal conductivity for another value and print the results:

>>> ground.kth = 3.35
>>> print(ground)
Ground material: User Defined
Thermal conductivity: 3.350 W/m·k
Volumetric heat capacity: 2500 J/m³·K
Thermal diffusivity: 1.34e-03 m²/s

Note that the ground material is now labeled as ‘User defined’.

It is also possible to initialize an empty GroundMaterial and set the value of the properties manually:

>>> ground = GroundMaterial()
>>> ground.kth = 2.27
>>> ground.Cp = 3278
>>> print(ground)
Ground material: User Defined
Thermal conductivity: 2.270 W/m·k
Volumetric heat capacity: 3278 J/m³·K
Thermal diffusivity: 6.92e-04 m²/s