Velocity-dependent heat transfer controls temperature in fracture networks

Area of Science:

• Geothermal Energy
• Subsurface Heat Transfer
• Fracture Network Hydrogeology

Background:

• Heat transfer in subsurface environments, particularly geothermal systems, is governed by Newton's law of cooling.
• Accurate parameterization of the heat transfer coefficient within complex fracture networks remains a significant challenge.
• Understanding heat transfer is vital for the design and management of engineered and natural geothermal reservoirs.

Purpose of the Study:

• To investigate the heterogeneity of the heat transfer coefficient within fracture networks.
• To assess the utility of laboratory single fracture experiments in estimating heat transfer coefficients.
• To analyze heat transfer dynamics at the individual fracture level.

Main Methods:

• Experimental investigation of heat transfer coefficients in single fractures under varying flow rates.
• Numerical simulations to complement experimental data and analyze heat transfer distributions.
• Analysis of heat transfer characteristics at the scale of individual fractures.

Main Results:

• The heat transfer coefficient exhibits strong heterogeneity within subsurface fracture networks.
• Laboratory experiments on single fractures provide reasonable estimates of the heat transfer coefficient, dependent on flow rate.
• Individual fracture characteristics significantly influence overall heat transfer in the network.

Conclusions:

• The findings improve temperature predictions in geothermal systems by accounting for fracture-scale heat transfer.
• This research enables more sustainable management and design of geothermal reservoirs by considering individual fracture contributions.
• The study highlights the importance of experimental data from single fractures for characterizing complex subsurface heat flow.