Generally speaking, the material temperature is determined by the process conditions and can not be changed at will, while the temperature of heating agent or coolant can be changed by selecting different media and flow rate. The heat transfer operation technology and chemical principle can be changed. For example, when saturated steam is used as heating agent, increasing steam pressure can increase its temperature; Increasing the flow of cooling water in the water cooler or using frozen brine instead of common cooling water can reduce the temperature of the coolant, etc. However, it should be noted that the technical feasibility and economic rationality should be considered when changing the temperature of heating agent or coolant. In addition, the average heat transfer temperature difference can be larger by using countercurrent operation or increasing shell side coating. 3. Increasing heat transfer coefficient can improve heat transfer rate of heat exchanger. Increasing the heat transfer coefficient is actually reducing the total thermal resistance of the heat exchanger maintenance device. The total heat transfer resistance between the two sides of the wall is equal to the sum of the convective heat transfer resistance, fouling heat transfer resistance and pipe wall heat transfer resistance. It can be seen that the total thermal resistance and the partial thermal resistance should be reduced. But in different cases, the proportion of each thermal resistance is different, so we should analyze the specific problems and try to reduce the proportion of the larger thermal resistance. Generally speaking, the thin wall and high thermal conductivity will not be the main thermal resistance in metal heat exchanger. The fouling resistance is a variable factor. When the heat exchanger is just put into use, the fouling resistance is very small, which can not be considered. However, with the extension of service time, the gradual increase of fouling can become the main factor hindering heat transfer, because the fouling gradually increases, which can become the main factor hindering heat transfer. The specific measures to reduce the fouling resistance are as follows: increasing the flow velocity and disturbance of the fluid to reduce the deposition of the fouling layer; Strengthen water quality treatment and try to use softened water; Adding scale inhibitor to prevent and slow down the formation of scale layer; Use mechanical or chemical methods to remove dirt in time. When the wall thermal resistance and fouling thermal resistance can be ignored, oik  111  should be increased * * the value of fluid should be increased * * the value of fluid should be increased * * the chemical engineering principle of two heat transfer operation technologies should be increased * * the value of fluid should be increased * * α Value. When two α When the difference is large, for example, water vapor condenses to heat the air, then 1 / K ≈ 1/ α At this time, the key to increase K value is to increase K value α The smaller side is fluid α。 if α I and α At the same time, * * improves both sides of the body α， In order to improve the K value. In the tube heat exchanger, in order to improve the heat transfer efficiency α， For the convective heat transfer without phase change, the following specific measures are usually taken: 1. In the tube side, the multi pass structure can make the flow velocity multiply and the flow direction change continuously, thus greatly improving the heat transfer efficiency α， However, when the number of passes increases, the maintenance force of the flow resistance heat exchanger will increase, so it needs to be weighed; ② In the shell side, multi pass structure can also be used, that is, longitudinal diaphragm is installed. However, due to the difficulties in manufacturing, installation and maintenance, multi pass structure is generally not used in engineering, and baffle is widely used, The principle of chemical engineering can not only increase the velocity of the fluid in the shell side, but also force the fluid to change the flow direction for many times, so as to strengthen the convective heat transfer. For condensation heat transfer, in addition to timely removal of non condensable gas, some other measures can be taken, such as opening some longitudinal grooves on the tube wall or installing metal mesh to prevent the formation of liquid film. For boiling heat transfer, it has been proved that the surface roughness or the addition of additives such as ethanol and acetone can effectively improve the boiling heat transfer α。 Training: start up, stop operation and abnormal phenomenon treatment heat transfer device process heat transfer operation technology chemical engineering schematic diagram ● Shandong heat exchanger maintenance and start-up steps ● stop steps when stopping, stop the hot fluid first, then stop the cold fluid, and drain the liquid in the shell side and tube side, so as to prevent the heat exchanger from frost cracking and corrosion. Abnormal phenomena and treatment methods causes of abnormal phenomena treatment methods heat transfer efficiency decrease 1. Tube fouling or blockage 2. Pipeline or valve blockage 3. Non condensable gas or condensate increase 1. Cleaning or descaling 2. Clearing 3. Discharging non condensable gas or condensate 1. Tube corrosion or poor expansion quality 1. Replacement of new tube or expansion heat transfer operation technology 1 Tube corrosion or poor expansion quality 2. Too large temperature difference between shell and tube bundle 3. Tube was worn by baffle plate 1. Replace new tube or make up expansion 2. Make up expansion 3. Pipe replacement vibration 1. Pipeline vibration 2. Too fast fluid flow rate in shell side 3. Low rigidity of machine base 1. Strengthen pipeline 2. Adjust fluid flow 3. Crack at the connection between reinforced tube sheet and shell 1. Serious corrosion 2. Poor welding quality 3. Shell skew 1 Repair after qualification 2. Clean up and repair welding 3. Align ● train target and master the simulation operation of heat exchanger. The training objective is to master the simulation operation of heat exchanger. Training: heat exchanger simulation training, heat transfer operation technology, chemical engineering principle, working principle and operation process ● training steps of heat exchanger maintenance in Shandong Province (1) cold start-up (2) normal operation (3) normal shutdown (1) cold start-up (2) normal operation (3) normal shutdown heat transfer operation technology, chemical engineering principle