Precautions for the design of the cooling system o

2022-09-19
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Precautions for the design of cooling tower cooling system closed cooling tower - the circulation of industrial cooling water between heat exchange equipment and cooling tower is driven by water pump. When designing the circulating system, the head and flow of the water pump have a certain margin. In this way, when the cooling water circulation system is running, one situation is to ensure the water flow and close the valve in the pipe, which consumes a lot of energy on the valve

precautions for the design of cooling tower cooling system

1 The selection of outdoor conversion temperature point of cooling tower cooling mode is directly related to the cooling hours of the system. Assuming that the required water supply humidity at the end of the air conditioner is determined to be 12.7 ℃ by calculation, considering the cooling range of the cooling tower, the heat loss of pipelines and heat exchangers and other heat losses to increase the water temperature by 4.5 ℃, it can be concluded that the cooling tower cooling mode can be switched when the outdoor wet bulb temperature is equal to or lower than 8.2 ℃

2. After the cooling tower in the system is selected according to the cooling load in summer and the outdoor calculated wet bulb temperature in summer, its cooling capacity under the cooling tower cooling mode should also be checked

3. The plate heat exchanger should be selected as the heat exchanger in the indirect cooling system. Compared with the traditional shell and tube heat exchanger, plate heat exchanger has high efficiency of heat exchange

4. In the direct cooling system, the chilled water pump in the cooling water loop should be set with bypass. In the cooling mode of the cooling tower, the chilled water pump is closed, and the chilled water passes by the chilled water pump. At this time, the circulating water power is provided by the cooling water pump. Therefore, the conversion of special pumps for cooling should be considered in the system design

5. In the design of direct cooling system, in order to speed up the utilization of magnesium alloy and rare earth magnesium (aluminum) alloy, attention should be paid to the sterilization and filtration of cooling water to prevent blocking the end coil

6. Considering that under specific outdoor wet bulb temperature and building load, the cooling amplitude of the cooling tower (the difference between the outlet water temperature of the cooling tower and the outdoor wet bulb temperature) decreases with the increase of the size of the cooling filler, for multiple sets of cooling tower systems, the method of series cooling towers can be used to increase the cooling effect, increase the outdoor conversion temperature of the cooling tower cooling mode, and thus increase the cooling hours

7. Since the cooling tower mainly operates in winter during the filtration season, antifreeze facilities should be set in the cooling water system in areas with low temperature in winter, such as setting side pipes and adding heaters

the circulation of industrial cooling water between heat exchange equipment and cooling tower is driven by water pump. When designing the circulating system, the head and flow of the water pump have a certain margin. In this way, when the cooling water circulation system is running, one situation is to ensure the water flow and turn down the valve in the pipeline, which consumes a lot of energy on the valve; the other situation is not to turn down the valve and the water flow in the pipeline is large, which leads to high energy consumption of the pump and reduced cooling effect of the cooling tower. The technology of water kinetic energy recovery cooling tower is to install a water turbine in the circulating water pipe to drive the fan to rotate, so as to use the excess water energy in the pipe to adjust the water flow in the pipe and improve the working state of the water pump.

1. Principle of free cooling at the water side

free cooling by water regulation refers to the appropriate addition of some pipelines and equipment on the basis of the conventional air conditioning water system. When the outdoor wet bulb temperature is below a certain value, Turn off the refrigeration unit, and the circulating cooling water flowing through the cooling tower will directly or indirectly supply cooling to the air conditioning system, so as to achieve the purpose of energy saving. With the arrival of transition season and winter, the outdoor temperature gradually decreases, the relative humidity decreases, and the outdoor wet bulb temperature also decreases, so does the outlet water temperature of the cooling tower. At this time, the indoor humidity load and cooling load of the building are also declining, and the dehumidification amount required at the end of the air conditioner is reduced. Appropriately increasing the chilled water temperature and reducing its dehumidification capacity can fully meet the comfort requirements of the air conditioning system

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cooling can be divided into two categories according to whether the cooling water is directly sent to the air conditioning terminal equipment: indirect cooling system and live makeup cooling system

2.1 indirect cooling system

indirect cooling system refers to the cooling water loop and chilled water loop in the system are independent and not connected, and energy transfer mainly depends on intermediate heat exchange equipment. Its biggest advantage is to ensure the integrity of the chilled water system loop. The sanitary conditions of the loop are guaranteed, but the cooling effect is reduced due to the intermediate heat exchange loss

2.1.1 add a plate heat exchanger to the original air conditioning water system. When cooling the cooling tower, turn off the refrigerating unit and connect the cooling water and chilled water to the plate heat exchanger respectively to realize energy transfer between them

2.2 direct cooling system

direct cooling system refers to a system that sets a bypass pipe in the original air conditioning water system to connect the chilled water loop with the cooling water loop. In summer, the normal air-conditioning water system is operated. When turning to the cooling tower for cooling, turn off the refrigeration unit and open the bypass through the valve, so that the cooling water directly enters the user's end. The cooling tower in the system can be open or closed. When the open cooling tower is used, the cooling water is easy to be polluted in direct contact with the outside air, and the dirt is easy to enter the indoor air distribution pipeline with the cooling water. Therefore, the development of the pipe making extruder industry still has a large market space, and the coiled tubes are blocked by dirt, so they are rarely used. Although the closed cooling tower can meet the health requirements, its heat transfer effect is affected due to its indirect evaporative cooling principle. In addition, the closed cooling tower is rarely used in China

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