Design and online calibration methods of pressure-independent intelligent regulating valve based on hydrodynamic resistance characteristics

•The hydrodynamic resistance characteristics of regulating valves are studied.•A design method of the pressure-independent intelligent valve is studied.•An online calibration method based on room temperature prediction is proposed.•A hybrid optimization algorithm is proposed in identification parameters.•The similitude principle is introduced in data expansion. In the district heating system, hydraulic maladjustment led to uneven heating and severe energy consumption. The existing valves cannot be accurately adjusted in the pipe networks and the complex structures of some valves weaken the energy-saving potential, failing to meet the demand of smart heating development. Considering these problems, the hydrodynamic resistance characteristics of regulating valves are studied, and the design and online calibration methods of the pressure-independent intelligent valve based on it are proposed. Among them, a) A hybrid optimization algorithm combining the particle swarm optimization algorithm and Elman neural network trained by Levenberg-Marquardt algorithm in identifying hydrodynamic resistance characteristics of regulating valves quickly and accurately with the least amount of experimental data is studied. b) For valves of the same type with different sizes, similitude principle provides a theoretical basis in expanding hydrodynamic resistance characteristics. c) An online calibration method of the pressure-independent intelligent regulating valve applied in the heating system based on the principles of room temperature prediction and mass conservation is proposed which avoids the inconvenience of field calibration. The pressure-independent intelligent regulating valve is worth researching and developing which provides a novel idea for decoupling the hydraulic conditions in parallel loops and reducing energy consumption.