Calculation approach of ground heat transfer considering annual variation of outdoor temperature

The calculation result of the current steady zoning calculation approach overestimates the ground heat transfer for failing to consider the large thermal storage ability of the ground and the difference in thermal conductivity. Based on this approach, treating the outdoor temperature approximately as the sum of its annual average and a sinusoidal wave with the period of one year, establishes a calculation model of ground heat transfer by three-dimensional dynamic finite difference method, and compares the calculation result by this method with that by the steady zoning calculation approach. Provides the steady heat transfer coefficients and the amplitudes and phases of heat flux in various zones under different thermal conductivities and thermal diffusivities of soil.