Selection of plate and gasket for plate heat exchanger
Heat exchanger is a high-efficiency and energy-saving heat exchanger has high heat transfer coefficient, compact structure, less material consumption, diversity, easy maintenance and other advantages, the application domain expands gradually, has been widely used in machinery, electric power, metallurgy, chemical, textile, beverage, town heating and other industries and fields, showing strong competitiveness.
Plate heat exchanger with metal plate (general thickness of 05 ~ 1 0mm) for the heat exchanger components, from stainless steel, industrial pure titanium or other materials of thin plate. Usually, the plate is pressed into a variety of groove type or corrugated shape, which can increase the stiffness of the plate, to prevent the deformation of the plate under pressure, but also enhance the degree of turbulence of the fluid, increasing the heat transfer area. Each of the four corners of the plate with a hole around the plate around the hole and pressure sealing gasket groove, and according to the needs of a gasket placed in the hole week slot, to allow fluid or prevent fluid into the surface between the role of the channel. If the number of the sheet in accordance with the requirements of heat exchanger are orderly arranged in the bracket, and with a fixed plate and a movable plate by a pressing screw pressed in the adjacent plates formed by fluid passages, and the orifice of the four corners of the plate. The gasket
1, the combination of plate form
According to the market research of plate heat exchanger, the plate shape of the plate heat exchanger manufacturers in our country is mainly based on the vertical herringbone corrugation. The herringbone corrugation is divided into a transverse herringbone ripple and a longitudinal herringbone corrugation. The flow of fluid in the channel formed by the above two types of plates can form a net flow, but the flow resistance and heat transfer coefficient are different. When the horizontal herringbone corrugated plate sheets, plates formed by fluid in the passage is relatively smooth, flow resistance is small, the pressure drop is very low, but the heat transfer coefficient than the longitudinal plate shape ripple slightly lower, so it is suitable for low flow rate, high viscosity, high rate of flow the occasion. When the plates with longitudinal shape ripple (the corrugation angle of 120 DEG), easy to produce turbulent flow formed in the plates of channel flow, high heat transfer coefficient, which can produce the ideal heat exchange effect, its main disadvantage is the pressure drop is relatively large, so it is only suitable for pressure too big, not suitable for high viscosity, low flow resistance.
2, the structure of the plate form
As the key component of plate heat exchanger, the reasonable design of the plate will directly affect the heat transfer performance, the resistance drop and the pressure bearing capacity of the plate. At present, there are more than one hundred kinds of core structure, the main form of the ripples are: herringbone ripple (including horizontal herringbone wavy and vertical herringbone ripple), horizontal ripple, vertical ripple, oblique ripple, etc.. The plate structure of heat exchanger production in China, the vast majority of the chevron bellows, which belongs to the typical structure of the network flow pattern, which is characterized in a fluid passage between the plates, staggered with contacts in these contacts between fluid flow around a spiral shaped path, resulting in strong disturbance. If the flow degree of the fluid is increased, the thickness of the bottom layer of the laminar flow can be reduced, and the convection heat transfer coefficient of the phase transition can be effectively improved, so as to achieve the purpose of increasing the heat transfer coefficient. The results show that when the Reynolds number is Re=20 ~ 200 and the flow velocity is from 02 to 0 5m/s, the fluid enters the turbulent state and has a high heat transfer coefficient. To this end, the board on the uniform, the wrong floor layout of the contacts, and appropriately reduce the spacing, in addition to greatly enhance the overall stiffness of the plate, but also can withstand a large pressure difference.
3, the sealing structure analysis
In the heat exchanger design, the overall structure of the plate has a very close relationship with the seal seal strength, reasonable structure design can not only improve the plate stiffness, improve the compression performance of plate heat exchanger, but also to ensure good sealing. The sealing structure is composed of a sealing groove plate and gasket, gasket sealing properties (physical properties, chemical properties and Technology) and the sealing groove form, gasket compression ratio is three elements of seal design.
At present, the domestic and foreign design of all kinds of plate sealing groove are in the form of plane, as shown in Figure 3a. The utility model has the advantages of simple structure, simple structure, easy bonding and good stability of the sealing gasket in the sealing groove. But there are also disadvantages, for example, when the sealing gasket and sealing groove, the alignment must be quite accurate, not allowed to have offset, otherwise in the clamping, sealing gasket will be out of the sealing groove and the effect of loss of seal. In view of this situation, this paper has done a lot of research and experiments on the sealing groove form, developed a new type of structure, the sealing gasket, stability when assembling positioning, improve sealing groove stiffness, reduces the clamping force of the assembly process, reduce the deformation of the plate. The results show that the years of use, the sealing groove form good effect, has great value of popularization.
4, sealing gasket
The gasket is an important part of the heat exchanger, when assembling the first adhesive gasket is stuck in the groove plate, and the hole in the peripheral grooves in the fluid flow according to the need to place the gasket, so as to allow or prevent fluid between the plates into the channel, to achieve the purpose of heat exchange. Sealing gasket material, structure and compression ratio is directly related to the sealing effect of plate heat exchanger. At present, the commonly used gasket materials are synthetic rubber and asbestos rubber two categories. Synthetic rubber commonly used nitrile rubber, three ethylene propylene diene rubber and fluorine rubber. The physical properties of the synthetic rubber gasket are mainly under the working condition
