Dynamic Characteristics and Energy Consumptions of an Indirect District Heating System Operating in Different Control Strategies

A set of dynamic models was developed for an indirect district heating system (IDHS), including pumps and adjusting valves. Firstly, dynamic simulations were conducted to find out how the supply water temperature of the boiler, indoor air temperature and fuel consumption vary with outdoor temperature. The influence of outdoor temperature could be compensated by modulating fuel consumptions, but the influences of solar radiation and indoor heat gains could not be ignored. Then, one-week operational states were simulated with actual meteorological data exerted and validated. And then, different control strategies were implemented and the one-week operational situations were simulated, respectively. The smallest indoor temperature variations could be achieved if the fuel, the primary piping network and radiator water flow rates were jointly controlled. However, the least amount of energy was consumed if the fuel consumption was controlled in terms of boiler supply temperature jointly with primary piping network flow rate controlled in terms of indoor temperature.