Constant-pressure variable-frequency closed-loop cooling tower system

I. System Design Concept

In industrial water cooling systems, there often exist multiple water usage points that are not used simultaneously. During peak water consumption periods, water supply is insufficient and water pressure drops. When certain equipment is not in use, the pump operates at a fixed speed, wasting electrical energy and, due to the pump's long-term high-speed operation, it can easily damage the bearings, affecting the pump's lifespan. Additionally, there have been instances where standby pumps have become rusty and seized. On this basis, Huata has developed a constant-pressure variable-frequency closed-loop cooling tower system, which saves energy by providing constant-pressure water supply.

2. Working Principle

The Constant Pressure Variable Frequency Closed Loop Cooling Tower System is an energy-saving water supply system. This system is a high-tech integrated energy-saving water supply unit that combines a variable frequency drive with a motor pump. The system adjusts the speed of the pump motor by controlling the output frequency of the variable frequency drive, based on the water pressure at the pump outlet (or the user's water flow rate) as the set parameter, via a pressure transmitter in the pipeline. This regulation of water pressure in the closed loop cooling circuit ensures that the water supply system maintains a constant pressure at the set value automatically: when water consumption increases, the frequency increases and the pump speed accelerates; when water consumption decreases, the frequency decreases and the pump speed slows down. This guarantees that the entire user's pipeline network always has sufficient water pressure (consistent with the user's set pressure) and water volume (which changes with the user's water consumption).

III. Advantages of the Constant Pressure Variable Frequency Closed-loop Cooling Tower System

Advantages of the Constant Pressure Variable Frequency System:

1. No negative pressure: The system operation with water topping up and pressurizing will not cause negative pressure in the pressurization system.

2. Adjustable Pressure: System pressure can be set by adjusting the pressure transmitter's value.

3. Variable Frequency Constant Pressure: The equipment continuously monitors the outlet pressure through sensors, compares the measured value with the set value, and calculates the number of motors and pump sets to be engaged as well as the variable frequency inverter's output frequency (which translates to the speed of the motor and pump) to achieve constant pressure.

4. High-level Automation: The system can achieve full automatic control with manual/automatic switching, automatic pressure adjustment, constant pressure, high/low voltage protection, phase failure protection, leakage protection, overload protection, overheat protection, and automatic digital temperature control. The system can be later configured with a human-machine interface according to user requirements, allowing for visual remote adjustment, monitoring, and maintenance, and integration with remote DCS systems.

5. Energy-saving systems, such as constant pressure variable frequency systems, can save at least 50% of electricity during operation. Combined with automatic digital temperature control, at least 60% of evaporation water consumption can be saved.