The prediction of friction factors in turbulent flow for an under ground forced cooled pipe-type electrical transmission cable system

Abstract

Forced cooled systems for underground, oil filled, pipe-type electrical transmission cable systems are becoming increasingly common in large urban centers. In systems of this type there exist a number of electrical transmission cables in an oil filled conduit. These cables are wrapped with a semi-circular, protective skid wire, which increases the turbulence in the flow and up until now has prevented any accurate or realistic prediction of the pressure drop. An equation has been used which correlates the friction factor of the rough surface which has been developed which combines the effects of the rough and smooth surface on the flow to obtain a friction factor vs. Reynolds Number plot for the entire pipe-type cable system. This theory has been written in the form of a FORTRAN IV computer program which accepts as input the geometrical dimensions of a system and yields as output the friction factor and corresponding Reynolds Number for the entire pipe-type cable geometry. The results predicted from the theory are consistently 15-30% above the experimentally determined values.