Innovative presets for cooling in new air pressure installations

1 China Great Wall Aluminum Company 2# air compressor station has 3 sets of 7L-100/8 air compressors, which are mainly used for agitating winds for alumina production. It is a key equipment of our factory. The equipment is two-stage compression. According to the instruction manual of the equipment, the air is first compressed by the first-stage cylinder to a temperature of 160, and then the temperature is lowered to about 40 by the intercooler, then enters the secondary cylinder for compression, and then enters the storage. Stir the gas tank to the seed tank.

Due to the unreasonable design structure of the intercooler, the design requirements are not met, and the automatic shutdown due to excessive temperature often causes the compressor to fail to operate normally, resulting in a passive situation in alumina production. In order to ensure the wind for the mixing tank, the structure of the intercooler is modified.

2 status analysis

The 7L-100/8 compressor uses a square element type intercooler, gas flows between the tubes, and cooling water flows in the tubes. The cooler core is rectangular and consists of a bundle of light pipes inserted into a set of iron fins. The two cores are horizontally placed in the housing. To make the overall structure compact, the intercooler is placed on the fuselage. This limits the size and weight of the cooler. After many years of use, it is found that the intercooler generally has a poor cooling effect, resulting in the exhaust temperature of the compressor being as high as 170 or more, which not only causes a large amount of power to be wasted, but also shortens the service life of the compressor valve and piston ring, and makes the cylinder There is a large amount of carbon in the pipeline, and because the cylinder exhaust port automatically controls the instrument, the temperature of the exhaust port is controlled to be no higher than 160, and the actual exhaust temperature is higher than this temperature, causing the compressor to overheat and stop. Result in shortened service life of each component.

3 reasons for the temperature is too high

3 1 intercooler between the two cylinders of the fuselage, the size and weight of the cooler are limited

When using a conventional component intercooler, there is not enough room to accommodate the necessary heat exchange area.

3 2 structural reasons

The level of the cooler is too large to use the gap between the casing and the core, so that part of the high-temperature gas does not pass through the cooling core in the casing, and cannot be cooled due to the short circuit.

3 3 heat sink is easy to cause deformation

The original intercooler core is composed of a plurality of sets of heat-dissipating iron pieces, which is easy to cause deformation of the film during installation and manufacture, and is easily blocked by carbon between the cooler piece and the piece to reduce cooling efficiency.

3 4 There is a gap between the inner hole of the heat sink and the outer surface of the copper tube

Since the inner hole of the heat sink and the outer surface of the copper tube are in the manufacturing process, there is often a gap to form an air thermal resistance, which reduces the heat exchange efficiency, so some heat sinks do not have a heat exchange effect.

4 transformation principle

According to the theory of heat transfer, the heat transfer efficiency affecting the intercooler is mainly the heat transfer coefficient of water and pipeline, and the heat transfer coefficient of gas and pipeline. Heat exchange area A = Q / KT m in the formula Q! ! ! The amount of heat transfer, that is, the heat load type of the cooler, is calculated from the inlet and outlet temperature parameters of the gas and the temperature parameter of the inlet and outlet of the cooling water. The Q value is the displacement of the compressor, the temperature of the gas entering the cooler, and the discharge. The temperature calculation of the cooler is also a fixed value; only K is a variable, and there are many factors affecting the K value. The main square element cooler is the air-moving shell, a is the heat transfer coefficient between the gas and the pipe wall, and the cooling water is inside the pipe; b is the heat transfer coefficient between the cooling water and the pipe wall, which affects the K value. It is the heat transfer coefficient of the gas and the pipe wall. Since the value is small, the K value is small and the required heat exchange area A is increased, resulting in a large volume of the intercooler. In order to design the intercooler to be similar in size to the original intercooler, the heat transfer coefficient between the gas and the pipe wall must be increased. Therefore, the cooler uses a copper threaded pipe to increase the heat coefficient between the gas and the pipe, and to increase the heat coefficient. The heat exchange area of ​​the cooler.

It is a structural diagram of the 7L-100/8 compressor, and the square element heat exchanger is on the left side. Because it has been changed into a tubular heat exchanger, it overcomes the defects of the original cooler in structure, manufacturing and installation, and solves the current situation of low heat transfer efficiency of the L-type compressor intercooler, so that it can be cooled in a limited space. The effect meets the design requirements.

Parameters in the intercooler before the air cooler retrofit air inlet temperature, 35 cooler inlet temperature, 172 158 cooler outlet temperature, 85 40 cooler maximum temperature, 87 118 secondary outlet temperature, especially the threaded tube heat exchanger The trial production has opened up a new field of application of threaded tube heat exchangers in the compressor industry. The heat exchange efficiency of the threaded pipe is 45 times that of the ordinary light pipe. Therefore, the original square element type cooler is changed into the tube type cooler, and the gas is divided into the S type gas passage by the partition outside the threaded pipe to make the gas The flow rate of the shell side is increased, the gas temperature is lowered, and the efficiency of the device is improved. The modified vertical threaded tube heat exchanger has achieved good results by replacing the original square element heat exchanger with the heat exchanger.

5 Conclusion

The 7L-100/8 compressor intercooler was installed and tested on the 10# unit of the 2# air compressor station of China Great Wall Aluminum Co., Ltd., and the cooler outlet temperature dropped to about 40, which extended the maintenance period and service life of the compressor. , achieved good economic benefits. The intercooler temperature is relatively low during operation. The threaded pipe is not easy to scale. The copper threaded pipe has a service life of more than 3 times than the light pipe, and the annual economic benefit is more than 100,000 yuan. It has extensive promotion value in the same industry.

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