The following explains the origin of the fluid and matrix parameters listed above. Project examples for this are, for instance, geothermal extraction and reinjection systems or thermally used ground probe fields. As a rule, an investigation is first carried out, for example using a GeoResponse test, to determine the suitability of the subsurface for geothermal use. The fluid parameters set above are empirical values from the literature. The following figure shows the results of a project-specific subsurface investigation.

Origin of the heat parameters

The matrix density ρ_s of 1,900 kg/m³ used in the SPRING dialog was taken as the average of the measured density of the Quaternary terrace sediments. The thermal conductivity of the matrix ʎ_s is calculated from the thermal conductivity of the overall system (ʎ_total from the table = 2.6 for Quaternary terrace sediments) using the following formula:

ʎ_f * n + (1-n)*ʎ_s = ʎ_total

ʎ_f = 0,6 W/(m*K), Empirical values fluid (groundwater)

n = Porosiy (of the model) [-]

ʎ_s = Thermal conductivity of the matrix , is wanted

ʎ_total = 2,6 W/(m*K), from figure above

With a porosity of 0.07 and rearranging the equation for ʎ_s, we get ʎ_s = 2.75 W/(m*K). The heat capacity c_s is calculated from the determined specific heat capacity (from the table) of 3,300 kJ/(m³*K) by dividing by the matrix density ρ_s of 1,900 kg/m³, resulting in 1,737 J/(kg*K). The conversion from kJ to J must be observed. The parameters for the other soil layers can be assigned via a zoning file.

Freezing