Multi-stage variable pressure difference control method for on-off type terminal chilled water systems

The variable pressure difference control in on-off type terminal chilled water systems is a difficult point of the variable flow chilled water systems. In order to solve the impact of the missing on-off control valve positions on the identification of the most unfavorable thermodynamic loops, a control method for setting the pressure difference of the dynamic balance valve of the crossbar according to the terminal temperature vector is proposed, and the set pressure difference of the dynamic differential pressure balance valve and the main pipe is adjusted step by step according to the principle of serial control to enhance the control stability of the system. Theoretical analysis shows that the control method has advantages of large temperature difference between supply and return water, smaller set value of total flow and main pipe pressure difference compared with the control methods of the main pipe constant pressure difference, the terminal constant pressure difference and the variable thermal loop pressure difference, and the chilled water transfer coefficient on the user side is increased by 47%-790%, 36%-530% and 34%-552%, respectively, showing greater energy-saving potential.