The total amount of circulating water remains constant; what factors determine the magnitude of the backflow pressure difference in the device?

The factors that affect the pressure difference in the return flow of circulating water mainly include: 1. **Pipeline resistance**: The length, diameter, and shape of the pipes (the number and type of bends), as well as the smoothness of their inner surfaces, all influence the level of resistance. 2. **Pump performance**: The pressure and flow rate provided by the pump directly affect the pressure difference in the system. 3. **Flow rate**: The higher the flow rate of water in the pipe, the greater the frictional resistance, and thus the higher the pressure difference. 4. **Internal structure of the device**: Such as the arrangement and opening degree of heat exchangers and valves, as well as any issues related to blockages or contamination. 5. **Temperature**: The higher the temperature of water, the lower its viscosity, which can result in different flow properties. To reduce the pressure difference while keeping the total amount of circulating water constant, the following measures can be considered: – **Optimize pump control**: Adjust the operating mode of the pumps to lower their output pressure appropriately, while ensuring that the system’s flow requirements are met. - **Reduce flow rate**: Slow down the pump speed or increase the pipe diameter appropriately; this will reduce the flow rate and thereby lower the pressure loss in the system. - **Clean pipes and equipment**: Regularly inspect and clean the deposits and impurities inside the pipes to keep them clean and unobstructed, thereby reducing resistance. - **Adjust valve opening**: Appropriately adjust the opening of the valves in the system to ensure a steady flow of water, and prevent an increase in overall pressure difference due to excessive local resistance. - **Check and eliminate any leaks or blockages in the system**: These issues can affect system pressure, and addressing them promptly can help reduce the pressure difference. In this way, the pressure difference in the system can be effectively adjusted and reduced without changing the total amount of circulating water. .

Under normal conditions, the flow rate and pressure of the circulating water remain stable; for the same unit, the pressure difference between the inlet and outlet of the circulating water is generally constant. It is not possible to adjust the pressure difference in the main pipe carrying the circulating water to the unit by adjusting the valve openings of the heat exchangers within the unit.

His summary is quite comprehensive; all the equipment between your two pressure measurement points will experience pressure loss, that is, a pressure difference. For example, replace the check valve at the outlet of your circulation water pump with one that results in less pipe loss ； I see that your backflow pressure is relatively high; it should be possible to reduce the pressure overall.

I don’t understand why the pressure difference needs to be reduced. If it is considered from the perspective of reducing energy loss, methods for lowering the pressure difference have already been mentioned by others. From the perspective of protecting the equipment, for example, some measuring instruments cannot withstand large pressure differences; in such cases, a valve can be added to the return pipeline to control the pressure difference, as long as the flow rate meets the required standards. It depends specifically on the actual layout of the pipes; both local and overall aspects need to be considered together.

This post was last edited by pzhmotor on 2025-3-3 at 14:28. The factor that affects the pressure difference is resistance; to reduce the pressure difference, it is necessary to reduce resistance. In practical work, there are certain constraints, and it’s not possible to reduce something just as easily as one wishes. Heat exchange equipment comes in standard designs, and it generally has specified ranges for inlet circulating water pressure (and temperature). Too low a pressure/temperature may affect the heat exchange process, while too high values indicate blockages inside the heat exchanger that require cleaning. The circulating water outlet pressure must ensure the lowest inlet pressure for all parallel devices. The return pressure of the circulating water also has a certain pressure range, which is influenced by the nozzles in the cooling tower. A high return water pressure indicates that the nozzle is clogged and needs to be cleaned as well. This is also a key aspect of circulating water management; dredging and cleaning the nozzles are required procedures. In my opinion, the original poster’s proposition is not rigorous. Strictly speaking, circulating water systems with a fixed flow rate are very rare. Due to the different water temperatures in winter and summer, the cooling effect of the circulating water is not the same; obviously, the volume of circulating water in summer is greater than that in winter. In practice, variable frequency systems that use flow rate to control the speed of circulation pumps are rare; outlet pressure is what is more commonly used. Unless your system has a high degree of redundancy and is extremely stable.

The design of the circulating water heat exchanger at the highest point determines the supply pressure; what remains are the opening degrees of each heat exchanger and the opening degree of the valve at the top tower