Thermal Characteristics of Two Types of Concrete Conduit Installations

A field installation of two different types of underground duct banks was made. They differed only in the spacing between the ducts and in the amount of concrete used in their thermal circuits. Identical loading was applied to each duct bank and studies were made of thermal gradients around them as determined by thermocouples. Differences in their thermal capabilities were shown to be due to different degrees of drying in soil or concrete in close proximity to the loaded ducts. Possible corrective measures to obtain better thermal conditions and a method of calculating thermal capabilities are presented, using previously published equations.