Numerical investigation of forced convection from vertical boreholes

In this work, the transient forced convection from vertical boreholes is investigated by numerical simulation. The actual borehole geometry is accounted for, resulting in perturbed flow and temperature fields. The present results are compared with an analytical line heat source model. A wide range of viable Péclet numbers is considered. The predicted average borehole surface temperature, Θ ¯ b , is in excellent agreement with the analytical solution for Pe ≲ 0.2 and Fo ≳ 1. As in the infinite line source model heat is released from the borehole axis so that the rise of the average borehole temperature provided by the analytical model is slower than the present results for Fo < 1. For Pe > 0.2, the distortion of the flow field induced by the borehole shows a significant effect on Θ ¯ b , causing an appreciable difference between the numerical results and the analytical solution in the whole range of considered Fourier numbers.