Solid thermal conduction is the dominant heat transfer mechanism for Vacuum Insulation Panels (VIPs) made with granular porous media, especially under vacuum conditions. Researchers tend to analyse heat transfer using numerical methods for granular porous media with complicated structures. However, the minimal contacts between spherical particles introduce significant complexity to numerical methods to solve heat transfer problems. To improve computational efficiency, this study quantitatively investigates the relationship between heat conduction and the contact radius between two contacting particles. A more accurate closed-form relation is proposed, and a scaling model is built to address the limitations of existing works that suffer from systematic errors and limited applicability. Compared to oversimplified relations in existing studies, numerical validation demonstrates that the proposed scaling model in this study achieves a maximum error of less than 1% in the range of 1/1000 to 1, significantly and fundamentally improving the predictive accuracy. This work provides a theoretical foundation for computing conductive heat transfer effectively in future studies in multiparticle systems.