Fractures often provide major conduits through which groundwater can flow, and the convective heat transfer between rock fracture surfaces and circulating fluid is a critical issue in heat recovery in fractured rocks. It is known that fracture surface roughness has a significant influence on the hydraulic, thermal and transport behavior of single fractures. In this study, the effects of joint surface roughness on the fluid flow and heat transfer processes in a representative element volume of fractured rocks was examined, based on two distributions of Joint Roughness Coefficient. The results showed that the role of fracture surface roughness in macroscopic fluid flow and heat transfer in fractured rocks is critical, in terms of reducing total flow rate and increasing thermal breakthrough time. Macroscopic fluid flow and heat transfer in different realizations of DFN models can be different from each other, but this difference is not significant.

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