Transient thermal conductivity of flexible district heating twin pipes

The standardized methods to measure the thermal conductivity of straight district heating pipes are not applicable on flexible district heating pipes. This paper presents a transient method determining the temperature dependent thermal conductivity of flexible twin pipes. A transient method to determine the temperaturedependent thermal conductivity of flexible single district heating pipes is presented in this paper. A flexible pipe coil is immersed into cold water. Hot water is distributed in the coil. The temperature decline of the coil water is measured and calculated. Minimizing the difference between the calculated and measured temperatures gives λ(T) of the flexible polyurethane foam. The method gives small errors