Fluid Properties

The Fluid dataclass holds the thermophysical properties of the heat carrier fluid circulating in the borehole heat exchanger.

Using CoolProp

CoolProp can be used to compute the fluid properties at a given temperature and pass them directly to Fluid.

Common fluid strings for BHE applications:

CoolProp string

Fluid

Freeze point (approx.)

'Water'

Pure water

0 °C

'INCOMP::MEG[0.20]'

Monoethylene glycol 20 %

−9 °C

'INCOMP::MEG[0.25]'

Monoethylene glycol 25 %

−12 °C

'INCOMP::MEG[0.30]'

Monoethylene glycol 30 %

−15 °C

'INCOMP::MEG[0.35]'

Monoethylene glycol 35 %

−20 °C

'INCOMP::MPG[0.20]'

Monopropylene glycol 20 %

−7 °C

'INCOMP::MPG[0.25]'

Monopropylene glycol 25 %

−10 °C

'INCOMP::MPG[0.30]'

Monopropylene glycol 30 %

−13 °C

'INCOMP::MPG[0.35]'

Monopropylene glycol 35 %

−18 °C

The fraction value in brackets is the mass fraction (e.g. 0.25 = 25 % by mass). The full list of available incompressible mixtures is available on the CoolProp documentation.

Example

from CoolProp.CoolProp import PropsSI
from carm.fluid import Fluid

fluid_str = 'INCOMP::MEG[0.25]'
T = 278.15  # K  (5 °C, typical BHE fluid temperature)
P = 101325  # Pa

rho = PropsSI('D', 'T', T, 'P', P, fluid_str)

fluid = Fluid(
    k_w   = PropsSI('L', 'T', T, 'P', P, fluid_str),
    rho_w  = rho,
    cp_w   = PropsSI('C', 'T', T, 'P', P, fluid_str),
    ni_w   = PropsSI('V', 'T', T, 'P', P, fluid_str) / rho,
)