Process composition of plate heat exchanger
The heat exchanger plate is the core component of the heat exchanger. The forming process and material characteristics of the heat exchanger plate will have a direct impact on the heat exchanger gasket and heat exchange efficiency. Plate heat exchangers usually use water as the cooling medium. The heat exchanger plates are mostly made of stainless steel thin plates. The corrugated flow tips are pressed on the heat exchanger plates. The space between two adjacent heat exchanger plates is the medium. Runners, when cold and hot fluids flow on both sides of the heat exchanger plates, they exchange heat through the heat exchanger plates.
The special flow channel formed by the ripples between the plates of the heat exchanger makes the fluid turbulent under the condition of extremely low flow velocity (Reynolds coefficient R. about 200). The turbulence under low Reynolds coefficient has its own descaling effect, which is powerful Destroy the insulating boundary layer and reduce the thermal resistance of the liquid film on the interface. Under normal circumstances, the heat transfer coefficient K value of the plate heat exchanger is in the range of 3 000-6 000W/m”℃. At the same time, the two media flow almost completely countercurrent, and the heat transfer efficiency is high. Under the same heat exchange efficiency, the plate heat exchanger only needs 1/2-1/4 of the area of the shell-and-tube heat exchanger to achieve the same heat exchange effect.
After the plate heat exchanger is used for a period of 1-2 years (depending on the actual operating conditions), necessary disassembly, cleaning, and pressure testing are required. The heat exchanger plates that have problems such as deformation or perforation need to be replaced in time. During this process, the assembly of the heat exchanger plates must be arranged in strict accordance with the flowchart. The flow chart is designed according to the cooling process. The heat exchanger plates are connected in parallel or in series. Commonly used are single-process and dual-process (or multi-process combination) plate heat exchangers, and single-process plate heat exchangers. The medium inlet and outlet nozzles are usually fixed on one side of the pressure plate, and the heating medium and the cold medium are respectively arranged on one side of the vertical axis of the fixed pressure plate, and the same medium is on the left side or the right side at the same time. To
Short circuit or leakage of two media caused by the staggered heat exchanger plates. Single-process plates are viewed from the side of the heat exchanger gasket. The fluid flowing in from the right always flows out from the right; the fluid flowing in from the left always flows from the left. Outflow. For the herringbone corrugated heat exchanger plate, if the fluid flows in from the left, and the herringbone pattern points upward, the A-type heat exchanger plate, rotate the A plate 180 degrees along the axis perpendicular to the plate surface to become the B-type heat exchanger. Heater plates, fluid enters and exits from the right.
After the plate heat exchanger is disassembled and inspected, the plates need to be clamped again according to the requirements. If the heat exchanger plates need to be installed in order to further improve the heat exchange capacity, it should be sufficient
Taking into account the deformation strength of the fixed pressure plate and the movable pressure plate, the same level of experimental pressure is used. The number of heat exchanger plates increases and the pre-tightening force of the bolts also needs to be increased. When the elastic deformation of the pressure plates on both sides exceeds the allowable range, the seal In the plane compression, there is radial sliding, forming a dislocation. At this time, the seal fails, and the two media leaks outside or the internal fluid exchanges with each other, which cannot be used normally.
For plate heat exchangers that have not been put into use for a long time, it is usually necessary to properly relax the tension of the screw. The heat exchanger plates and heat exchanger seals lose the necessary elasticity after long-term pressure, and the seals are prone to failure and reduce the service life. The compression bolts of the heat exchanger are evenly distributed, and the plate heat exchanger needs to be clamped diagonally before installation, and the inner distance of the two compression plates is measured in real time to ensure that the two compression plates are basically parallel In the state, the deviation of the parallelism of the four corners is less than 2%, and the pre-tightening of the bolts is carried out in the order indicated in Figure 5.
In order to efficiently play the heat exchange efficiency, the two medium circulation of the plate heat exchanger adopts full countercurrent flow. In actual use, considering the offline spare parts matching problem of each hydraulic system, the exchanger with a larger heat exchange area will be used as a common part. For storage, there will be differences in the direction of the medium interface, cold and hot medium interchange interfaces or the same medium in and out of the same medium. Although this kind of problem will not be harmful to the formation of the seal, it will have a certain impact on the heat exchange efficiency.
1. The plate heat exchanger has strict requirements for the horizontal tension of the connecting screw, especially when hoisting a high-power heat exchanger with a heavier weight, a special hoisting position must be used. Unconventional hoisting methods have a bearing on the force structure of the screw. Certain damage, the heat exchanger plates are prone to misalignment. In addition, after large-scale plate heat exchange equipment is filled with cold and heat medium, the weight of the medium itself will increase significantly, and the installation of the equipment must also be placed on a certain level.
2. At the same time as the heat exchange between the cold and heat medium of the heat exchanger, the exposed heat exchanger plates also have a heat exchange process with the ambient air. The necessary space (above lm) is usually reserved around the heat exchanger. In order to form a smooth air flow environment, it is conducive to the play of heat exchange capacity.
