Improving evaluation of the heat losses from arrays of pipes or electric cables buried in homogeneous soil

The evaluation of the heat loss from finite arrays of horizontal buried cylinders is very interesting for many practical applications. A considerable effort has been done in the field of the electrical engineering to develop methods for calculating the thermal flux from the cables system to the ground surface through the soil. Nevertheless, the modeling hypothesis currently assumed for the case of arrays of a finite number of pipes-cables introduces approximations that can involve inaccuracies in calculation. In this paper the extent of such inaccuracies is investigated by numerical techniques. Results show that the thermal resistance value of the worst refrigerated cylinder, obtained from numerical simulation, can result even 60% higher than the value calculated with standard IEC–IEEE method, while the thermal resistance of the whole array does not differ from the value obtained with the standard IEC–IEEE calculation method. Some correlating equations to obtain more accurate results in the thermal resistance calculation for the worst refrigerated cylinder are proposed. ► Thermal conductive field of an array of infinite length cylinders in a semi-infinite space with constant thermal properties has been studied. ► Results show that the value of the thermal resistance between each cylinder and the ground surface obtained from the numerical simulation ( R NUM ) has different values from the one ( R IEC ) calculated with Standard IEC–IEEE method. ► The ratio R NUM / R IEC shows a dependence on P/D, on cylinder number N C , and doesn’t vary so much with the depth value h C . ► Dimensionless correlations to evaluate the ratio R NUM / R IEC have been proposed. ► The whole array thermal resistance (for length unit) has also been numerically calculated.