Ryszard Zwierzchowski, Olgierd Niemyjski
The paper presents a simulation of heat losses of a distribution network with different technical structure and under different operating conditions for a District Heating and Cooling (DHC) system. The DHC system consists of a Combined Heat and Power (CHP) plant and a Distribution Network (DN) with chambers and heat and cold substations. The different operating conditions of the DHC systems result in the DNs having variable transportation losses. The result of the analysis was used to verify the models and calculation methods of the fluid flow and heat losses in the DN, when cold is generated using either absorption or adsorption chillers. Different technical structure of a DN means a system of connected underground and aboveground piping with different diameters. DNs in Poland are usually installed as an underground, traditionally insulated piping placed in the concrete ducts (large diameter main pipelines) or a pre-insulated piping placed directly in the ground. The total heat losses of the DN differ according to the individual systems and depend on the size of the DHC system, its heating loads and quality of insulation of the piping. This paper presents the results of the numerical calculation of the temperature distribution in the soil around the piping channel using an FDA model. These results were utilized for numerical simulation of the water and heat flow through the DN and calculation of heat transportation losses. The numerical simulation of heat losses was performed for the particular system of connected underground and aboveground piping with different diameters. Finally, the heat transportation losses of the DN were calculated and compared for analyzed District Heating (DH) system i.e. without cold consumers and for the DHC system, when cold for consumers is generated using either the absorption or the adsorption chillers.