when does a fracture matter for a borehole heat exchanger€¦ · the university of southampton...

Engineering and the Environment

The University of Southampton

GSHPA technical seminar

Leeds, 24 May 2018

When does

a fracture matter

for a borehole

heat exchanger ?

Sasha PedchenkoFleur LoveridgeNick WoodmanWilliam Powrie

Intro

Intro Methods Fracture Groundwater Uncertainty Sensitivity Conclusion

460 research papers

Intro

Intro Methods Fracture Groundwater Uncertainty Sensitivity Conclusion

Apparent

thermal

conductivity

dispersivity tensor

heat capacity of fluid

Darcy velocity

(Sauty et al., 1982)

= +Effective

thermal

conductivity ∗∗

Intro

Intro Methods Fracture Groundwater Uncertainty Sensitivity Conclusion

Fracture distance

Fracture aperture

Dehkordi et al., 2015

Intro

Intro Methods Fracture Groundwater Uncertainty Sensitivity Conclusion

Fracture distance

Fracture aperture

Dehkordi et al., 2015

Fracture in impermeablematrix

apparent thermal conductivity

Intro

Intro Methods Fracture Groundwater Uncertainty Sensitivity Conclusion

fracture influence

groundwater & uncertainty

effective parameters

Concept

Intro Methods Fracture Groundwater Uncertainty Sensitivity Conclusion

Workflow

Intro Methods Fracture Groundwater Uncertainty Sensitivity Conclusion

Numerical model

2D

Validation

MILS

One-factor-at-a-time

sensitivity analysis

Uncertainty analysis

30 000 runs

Example

Intro Methods Fracture Groundwater Uncertainty Sensitivity Conclusion

Distance 0.5 m

after 30 years

2K

Example

Intro Methods Fracture Groundwater Uncertainty Sensitivity Conclusion

Distance 0.5 m

Distance 10 m

after 30 years

2K

2K

Effects

Intro Methods Fracture Groundwater Uncertainty Sensitivity Conclusion

distance 10 m

0.05 m/day in matrix

Effects

Intro Methods Fracture Groundwater Uncertainty Sensitivity Conclusion

0.05 m/day in matrix0.005 m/day in matrix

distance 10 m

Groundwater

Intro Methods Fracture Groundwater Uncertainty Sensitivity Conclusion

~7 K

Groundwater

Intro Methods Fracture Groundwater Uncertainty Sensitivity Conclusion

~100m

Uncertainty

Intro Methods Fracture Groundwater Uncertainty Sensitivity Conclusion

Uncertainty

Intro Methods Fracture Groundwater Uncertainty Sensitivity Conclusion

☺

Uncertainty

Intro Methods Fracture Groundwater Uncertainty Sensitivity Conclusion

☺

Sensitivity

Intro Methods Fracture Groundwater Uncertainty Sensitivity Conclusion

0.05 m/day in matrix

0.005 m/day in matrix

☺

Intro Methods Fracture Groundwater Uncertainty Sensitivity Conclusion

Apparent thermal conductivity

Slow local groundwater flow

Slow local groundwater flow

Intro Methods Fracture Groundwater Uncertainty Sensitivity Conclusion

Apparent thermal conductivity Fast local

groundwater flow

Oleksandra PedchenkoEngineering and the EnvironmentUniversity of Southampton

oop1g10@soton.ac.uk

Thank youQuestions & advice welcome

Q&A supplements

Sensitivity

Intro Methods Fracture Groundwater Uncertainty Sensitivity Conclusion

0.05 m/day

0.005 m/day

Uncertainty

Intro Methods Fracture Groundwater Uncertainty Sensitivity Conclusion

0.05 m/day in matrix

0.005 m/day in matrix

Intro

Intro Methods Fracture Groundwater Uncertainty Sensitivity Conclusion

Apparent thermal conductivity

𝜆𝑎 = 𝜆𝐴 + 𝛼 𝛾𝐹 𝑣

effectivethermal conductivity of porous medium

dispersivitytensor

heat capacity of fluid

Darcy velocity

(Sauty et al 1982)