Prediction of effective thermal conductivity of granular materials is important in many applications, from thermal management in electronics to celestial soils. Discrete elements method (DEM) is the most advanced approach, able to capture effects of mechanical load, material mixtures on transport coefficients. Pivotal for this approach is knowing heat transfer coefficient between adjacent particles. Currently in most DEM-capable software only particles with direct contact are considered for conduction heat transfer. We performed numerical modeling of conductive heat transfer coefficient between spherical particles separated by less conducting media. We use numerical solution of differential equations to take into account thermal resistance inside particles and through gap between them. Using non-dimensional approach, we found simple generalized correlation between heat transfer coefficient, ratio of thermal conductivities and ratio of gap between particles and their radius. Correlation is convenient to use in DEM heat transfer calculations in packed and fluidised beds.