.Buildings.Fluid.Geothermal.Borefields.BaseClasses.HeatTransfer.Validation.Measured_SmallScale

Information

This validation case simulates the experiment of Cimmino and Bernier (2015). The experiment consists in the injection of heat at an average rate of 8.67 W in a 0.40 m long borehole over a period of 168 h. Borehole wall tempratures were measured by a series of 22 thermocouples welded to the stainless steel pipe that contains the borehole and acts as the borehole wall.

Since the model is not adapted to the simulation of small scale boreholes, the borehole dimensions are multiplied by a factor 375 to obtain a scaled-up 150.0 m long borehole. The time values of the experimental data are then multiplied by a factor 375². The predicted borehole wall temperature is compared to the experimental data.

A sharp increase in the rate of change of the borehole wall temperature is observed at t=500 years. This is caused by a sudden change in the rate of heat injected to the fluid at the same moment. The simulated borehole wall temperature is more affected the measured borehole wall temperature since the validation model does not consider the dynamics of the borehole and the fluid, and that heat is directly injected at the borehole wall. In the experiment, the sudden change in heat injection rate was dampened by the circulating fluid, the borehole filling material, and the measurement apparatus.

References

Cimmino, M. and Bernier, M. 2015. Experimental determination of the g-functions of a small-scale geothermal borehole. Geothermics 56: 60-71.

Revisions

• July 18, 2018, by Massimo Cimmino:
  First implementation.