.AixLib.BoundaryConditions.GroundTemperature.GroundTemperatureKusuda

Information

• This model is a simple model for undisturbed ground temperature
• It is used with district heating grids or LTN in order to model thermal pipe losses

Main equations

T_ground =T_mean*T_amp*exp(-D*√(π/(365*α))) *cos((2π/365)(t-t_shift-(D/2)*√(365/(π*α))))

Assumption and limitations

The model does not model the influence of the pipe temperature loss on the ground temperature. The ground temperature is only dependent on the set parameters.

Typical use and important parameters

The model is used as a boundary condition for the thermal losses in district heating pipes.

Differently then stated in the parameter description below t_shift needs to be declared in days and α needs to me declared in m2/day! (The Modelica SI unit diffusivity does not support m2/day as a display unit.)

A typical value for α is bewteen 0.03 and 0.05 m2/day.

Options

No options.

Validation

The validation was done by comparing simulation results (San Francisco example) with the findings of the first given reference below (Florides and Kalogirou,2005).

The Potsdam Institute for Climate Impact Research provides measurement data for a German site, which can be used for comparison.

Implementation

The model implements the equation given above and supplies the undisturbed ground temperature via a heat port.

References

• Florides and Kalogirou, 2005, Annual ground temperature measurements at various depths. In: 8th REHVA World Congress, Clima, Lausanne, Switzerland Citeseer, 2005
• T. Kusuda, P. R. Achenbach, Earth temperature and thermal diffusivity at selected stations in the united states, Tech. rep., DTIC Document (1965)
• Bünning F., 2017, Simulation-based investigation of bidirectional low temperature district heating and cooling networks and their control, Master thesis

Revisions

• April 30, 2018, by Marcus Fuchs:
  Update documentation (see issue 561).
• May 2017, by Felix Buenning: Updated information window according to documentation standards
• October 2016, by Felix Buenning: Developed and implemented