Modeling and analysis of effective thermal conductivity during hydrate phase transitions

Abstract

Heat transport and mass transfer happen in the hydrate phase transition, effecting variation of the effective thermal conductivity of the hydrate-water-gas-sediment system. The effective thermal conductivity of methane hydrate and of its sediment system was measured experimentally to propose the additional coefficient formula caused by phase transition. The experimental results show that the effective thermal conductivity of the two systems were 0.2284–2.9900 W·m⁻¹·K⁻¹ and 1.0020–1.5030 W·m⁻¹·K⁻¹, and the additional coefficients were 0.5129–4.8619 and 0.5979–1.2504, respectively. The porous media structure can suppress various disturbances in the system and reduces the additional coefficient. The additional coefficient is generally normal distribution or has a linear relationship with the variational hydrate content in the phase transition stage but shows a strong linear connection with temperature in the non-phase transition stage. Based on the relation of additional coefficient and hydrate content, a correction effective thermal conductivity model is proposed to predict the effective thermal conductivity of hydrate-bearing sediment system during hydrate phase transition. The experimental data consistently fall within the predictive bounds of the model, with optimal predictive accuracy observed when the hydrate content is below 0.6. These research findings not only enrich the thermal physical property database, but also provide support for heat transfer analysis in the formation and exploitation of hydrate resources.