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Assembly and disassembly of plate heat exchanger

Assembly and disassembly of plate heat exchanger

2022-09-30

The newly purchased heat exchanger has been installed as a whole and can be installed as a whole. If it is not necessary, it shall not be disassembled. The removal and reinstallation of plate heat exchanger are very meticulous work, which should be carried out by experienced personnel according to certain rules to ensure good sealing and normal use after installation. Improper assembly, disassembly and installation will cause poor sealing and even plate deformation and damage, which is difficult to recover. Before dismantling the heat exchanger, the original thickness of the plate group shall be measured with a steel ruler at the upper, lower, left and right corners of the equipment and recorded. This thickness shall be restored as much as possible during re installation. If the number of plates is increased or decreased, the correct total thickness shall be calculated first. For example, with 80 BR50 plates, the nominal thickness is 80 × (３．８+0.６)=３５２mm The difference between the thickness after installation and compaction and the nominal value shall be less than 1%, and the thickness of the above example shall be 347~357mm. Plate heat exchanger is usually compressed into a whole with 6~12 bolts. During assembly and disassembly, these bolts shall be tightened or loosened evenly and evenly without uneven tightness. When removing the loosening bolt, loosen the middle bolt first and then the four corners. At the beginning, it should be 1~2 turns each time, more later, and repeated several times until it is completely released. During the relaxation process, the total thickness of the plate shall be measured at the four corners. The left and right deviations shall not exceed 10mm, and the upper and lower deviations shall not exceed 25mm.

What are the characteristics of gas flow in the heat exchanger?

What are the characteristics of gas flow in the heat exchanger?

2022-09-30

The heat exchanger has different thermal characteristics due to different gas flow modes. Under the condition that the temperature of exhaust gas entering the heat exchanger is the same, the air can be preheated to a higher temperature by counter current than by forward current. Under the same other conditions, the heat transfer of countercurrent heat exchanger is larger than that of downstream heat exchanger, and its structure is more compact than that of downstream heat exchanger. From the working conditions of the heat exchanger wall, the forward flow type is more favorable. Because the temperature of the heat exchanger wall is almost the same for both ends of the parallel flow heat exchanger, its maximum temperature is lower than that of the counter flow heat exchanger, the heat exchanger is not easy to be deformed or damaged, and the material requirements are not high. On the counter flow heat exchanger, the wall temperature at the high temperature end is close to the exhaust gas population temperature, and the temperature difference between the two ends is large. This puts forward higher requirements for the material of the wall, and due to the large temperature difference at both ends, it is easy to deform and damage. In practical application, most heat exchangers adopt countercurrent mode.

Plate heat exchanger uses corrosion inhibitor to achieve anti-corrosion maintenance effect

Plate heat exchanger uses corrosion inhibitor to achieve anti-corrosion maintenance effect

2022-09-30

How to maintain and prevent corrosion of plate heat exchanger during use? After knowing the various causes of heat exchanger corrosion, how to select appropriate anti-corrosion measures to achieve the goal of efficient use of equipment. According to the corrosion related conditions, the following anti-corrosion methods are proposed: corrosion inhibitors are mainly introduced here. Use corrosion inhibitor to prevent corrosion. The combination of corrosion inhibitor and cathodic inhibitor can give satisfactory and economical anti-corrosion effect. Chromate zinc polyphosphate: polyphosphate is used because it has the function of cleaning metal surface and corrosion inhibition. Polyphosphate can be partially converted into orthophosphate, which meets with calcium to form colloidal cation, which has the effect of inhibiting the formation of impurities in plate heat exchanger. Chromate zinc phosphonate: This method uses sodium phosphonate instead of polyphosphate, which is similar to the previous method. The scale that is about to be formed is effectively inhibited by carbamate phosphate, and the precipitation of calcium salt can be controlled even if the pH value is 9. Chromate zinc hydrolyzed polyacrylamide: due to the dispersion of hydrolyzed polyacrylamide of cationic copolymer, the scale in plate heat exchanger can be prevented from turning into dirt.

How to improve the heat exchange efficiency of plate heat exchanger

How to improve the heat exchange efficiency of plate heat exchanger

2022-09-30

Plate heat exchanger is a wall heat exchanger. The cold fluid transfers heat through the plates of the heat exchanger. The fluid directly contacts the plates. The heat transfer mode is heat conduction and convection heat transfer. The key to improve the heat transfer efficiency of plate heat exchanger is to improve the heat transfer coefficient and logarithmic average temperature difference. 1. To improve the heat transfer coefficient of the heat exchanger, the only way to effectively improve the heat transfer coefficient of the heat exchanger is to simultaneously increase the surface heat coefficient of the hot and cold sides of the plate, reduce the thermal resistance of the scale layer, select the plate with high thermal conductivity and reduce the thickness of the plate. (1) Improve the surface heat transfer coefficient of plates Because the ripple of plate heat exchanger can make the fluid turbulent at a small flow rate, it can obtain a higher surface heat transfer coefficient, which is related to the geometric structure of plate ripple and the flow state of the medium. The waveform of the plate includes herringbone, straight, spherical, etc. After years of research and experiments, it is found that the herringbone plate with triangular corrugated section has a higher surface heat transfer coefficient, and the greater the included angle of the corrugated, the higher the medium velocity in the flow path between the plates, and the greater the surface heat transfer coefficient. (2) Reduce the thermal resistance of the dirt layer The key to reduce the thermal resistance of the fouling layer of the heat exchanger is to prevent the plate structure. When the thickness of the plate structure is 1mm, the heat transfer coefficient decreases by about 10%. Therefore, attention must be paid to monitoring the water quality at both cold and hot ends of the heat exchanger to prevent the plate structure and prevent impurities in the water from adhering to the plate. In order to prevent water theft and steel corrosion, some heat supply units add chemicals to the heating medium. Therefore, attention must be paid to the water quality and viscous chemicals, which may cause impurities to contaminate the heat exchanger plates. If there are viscous impurities in the water, special filters shall be used for treatment. When selecting the medicament, it is better to select the medicament without viscosity.

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