Views:0 Author:Site Editor Publish Time: 2020-04-27 Origin:Site
According to the technological requirements of the factory's production equipment, the chilled water supply temperature requirement is not higher than 9 ° C when the chiller is in operation throughout the year. The three cooling towers are open systems. Currently, due to less cooling load in winter, one chiller is generally operated. High load is 80%, most of the time the cooling load is about 50%. Considering that the outdoor temperature in winter is relatively low and the cooling load demand is small, you can make full use of the cooling capacity of the cooling tower and meet the cooling load of the factory through the plate heat exchanger demand.
In winter, when the air conditioning terminal and production equipment require cooling load, the existing cooling tower, cooling water pump, plate heat exchanger and chilled water pump can be used for cooling. Of course, this requires certain conditions, that is, the outlet temperature of the cooling tower is lower than the required temperature of the chilled water, and the outlet temperature of the cooling tower is directly related to the outdoor wet bulb temperature. Therefore, the "current outdoor wet bulb temperature plus Under the condition that 4.5 ℃ is less than or equal to the demand temperature of chilled water supply, a plate heat exchanger can be used for cooling.
Winter refrigeration uses a combination of plate heat exchanger cooling and chiller cooling to reduce cooling energy consumption, improve energy efficiency, and extend the life of the chiller.
Due to the large temperature difference between day and night in winter, when outdoor temperature changes and cooling load changes are more frequent, it is necessary to solve the problem of automatic frequent switching of the cooling modes of plate heat exchangers and chillers, and to ensure a constant control goal of chilled water supply temperature. To ensure the stable operation of the system. Under the same cooling load and water flow rate, as the temperature of the outdoor wet bulb decreases, the outlet water temperature of the cooling tower decreases accordingly.
In the chilled water system, under a certain cooling load demand and water temperature drop, the chilled water flow will directly affect the water supply temperature. Through the temperature sensors on the cooling water and chilled water supply pipes, respectively control the motor frequency of the cooling water pump and the chilled water pump to control the water flow; and adjust the output cold load of the chiller according to the water flow of the chiller to maintain the chilled water The temperature is constant.
Cooling mode switching
A temperature sensor is installed on the cooling water and chilled water supply pipelines. When the outdoor wet bulb temperature in winter is less than or equal to 4.5 ℃, the output load rate of the chiller is less than or equal to 50%, and the chilled water supply temperature is less than 9 ℃ for 10min, Can use plate heat exchanger cooling mode for cooling. At this time, the electric control valves M1 and M3 are slowly closed, the cooling power consumption of the chiller is slowly reduced, and the electric control valves M2 and M4 are slowly opened. At this time, the system enters the combined cooling mode of the plate heat exchanger and the chiller, and maintains the water supply temperature. It is constant until the chiller stops working, the electric regulating valves M1 and M3 are closed, and the plate heat exchanger cooling mode is completely entered. At the same time, the cooling water pump and the chilled water pump are used to control the flow of water and keep the temperature of the chilled water supply constant.
Analysis of energy-saving economic benefits
It is required that the temperature of the chilled water supply is not higher than 9 ℃, and the outdoor wet bulb temperature is below 4.5 ℃, and the cooling water can be used to cool the plate heat exchanger.
In winter, the factory requires less cooling load and has a lower cooling water temperature, which will greatly reduce the condensing pressure of the chiller and affect the aerodynamics of the chiller. If the cooling tower cooling water is used to provide cooling capacity for the air-conditioning terminal and process equipment through the plate heat exchanger profile, the running time of the chiller in winter can be reduced. Reduce energy consumption and extend its service life.