The Effect of Groundwater Level on Forced Convection Heat Transfer from a Buried Cylinder

The effect of groundwater level on forced convection heat transfer from a cylinder of 1 m in diameter buried at a depth of 10 m is studied numerically. The porosity and permeability of the soil are fixed at 0.5 and 1.0 x 10(-11) m(2), respectively, throughout the present study, while the inlet velocity U-0 and the position of the phreatic surface (h), measured from the center of the cylinder, are varied in the ranges from 10(-9) to 10(-3) m s(-1) and from - 4 to 4 m, respectively. Under these conditions, the heat fluxes on the cylinder are computed numerically. Various approximate solutions are also proposed and compared with those obtained numerically. The heat transfer results are also presented in nondimensional form for generality. The paper is divided into three parts, depending on the relative positions of the phreatic surface to the heated cylinder. First, the heat transfer rates are analyzed when the phreatic surface is above the cylinder, so that the cylinder is completely submerged in the water. In the second case, the phreatic surface is assumed to lie below the cylinder, so that the cylinder is left in the water-free space. In the third case, the phreatic surface is in contact with the cylinder surface, so that the cylinder is partially submerged in groundwater. For the above respective cases, three different approximate analyses are presented, and their validities and limitations are evaluated in comparison with the numerical calculations.