Undisturbed Ground Temperature—Different Methods of Determination

Abstract

Methods for the calculation of the undisturbed ground temperature (UGT) are presented. Heat fluxes occurring on the surface of the ground and their influence on the UGT are described. Correlation equations for the calculation of the undisturbed ground temperature based on the meteorological data averaged in the yearly cycle are proposed. These equations are of a semi-empirical character and they are based on the heat flux balance. The determined coefficients of these equations, particularly the convection heat transfer coefficient, are consistent with the values specified by other methods.

Undisturbed ground temperature in Melbourne

“…However, for the local site (Burnley, Melbourne) variation in average ground temperature (ΔT m , °C) was found to be 1.4 °C between TRNSYS and measured at 21 m and 40 m depthas shown in Figure 2. As described the various heat fluxes (Figure 1(a)), the ground temperature is highly influenced by the ambient air temperature as per different UGT equation models [2,9] where other heat fluxes were almost cancelled out by each other. In addition, Baggs [14] investigated on remote prediction of ground temperature in Australia soil.…”

“…Temperature changes in the soil and ground surface are essential driven by heat fluxes at the ground surface. Various phenomena occurring at the ground surface are presented in Figure 1(a) [2,8,9]. The surface temperature (T s ,°C) is raised by absorbing heat from the solar radiation (S,Wm -2 ).…”

“…Figure 4 shows the monthly ground temperature variations with various depths. Simulation (TRNSYS) was used to determine the ground temperature at 0, 3,6,9,10,11,12,13,14,15,18,21, and 40 m depthon the representative dates [15]of every month (from January to December). At 0 m depth, the maximum ground surface temperature was foundto be 21.38 °C inJanuary and the minimumground surface temperature was foundto be 11.15°C inJuly.…”

Heat Transfer Model to Predict Temperature Distribution in the Ground

“…The thickness of subsurface layer depends on the thermal diffusivity of the ground. For low values of thermal diffusivity, the subsurface layer has a small thickness, but when the thermal diffusivity of the ground is high, the stabilization of the ground temperature occurs at larger depths [15].…”

“…They improved the convective component by introducing the aerodynamic resistance of the canopy layer. Most of other works are based on the heat fluxes balance equation on the ground surface, i.e., short-wave and long-wave radiation fluxes, convective heat flux, evaporative heat flux and conductive flux [13][14][15][16][17], however some of these works assume that the long-wave radiation flux has a constant value or show the results of temperature measurements or heat transfer rates when a ground heat exchanger is installed in the soil. For example, Nam et al [17] developed a numerical model that combines a heat transport model with groundwater flow using heat fluxes balance on the ground surface and a heat exchanger model with a U-tube shape.…”