Thermal Behaviour of Piggyback-Laid District Heating and District Cooling Pipes

Abstract District heating (DH) and district cooling (DC) networks are key to sustainable urban energy systems. This study investigates thermal interactions between DH and DC pipelines installed in a piggyback configuration within a shared trench using a combination of in-situ temperature measurements and transient heat transfer simulations. A 175-meter section of Munich’s DH and DC network was analysed through experimental temperature measurements and a finite element method (FEM)-based thermal model in MATLAB. Results show that DH operation increases trench soil temperatures, leading to continuous heat gains in the DC flow pipe. Although the impact within the investigated area is limited due to the short piggyback-laid section, large-scale implementations will experience greater thermal interference. A simulated scenario without DH in operation confirmed that the pipe placement aligns ground temperatures with DC flow temperatures, avoiding heat gains. The validated model serves as a reliable tool for assessing heat losses and gains, contributing to future DH and DC network designs in urban infrastructure planning.