Views:0 Author:Site Editor Publish Time: 2020-03-25 Origin:Site
Selection requirements of plate heat exchanger
As we all know, the plate heat exchanger has been used more and more widely, and has widely replaced the heating and air-conditioning engineering of industrial and civil buildings. The correct selection of the plate heat exchanger can ensure the smooth implementation and use of the project. Now we will introduce the main points of the selection.
I. Structural material requirements
Because the heat exchanger surface of the plate heat exchanger is relatively thin compared to other heat exchanger surfaces, corrosion is basically meaningless. When converting from a shell and tube heat exchanger to a plate heat exchanger, the heat transfer surface sometimes requires the use of alloy materials. But in addition to the occasional use of high-strength alloy materials, thinner plates prove that higher heat exchange efficiency also means lower prices.
Ⅱ. Performance requirements
The performance requirements of plate heat exchange heat are mainly the ability of the temperature difference between the two different media of the heat exchanger to change the temperature of the medium, and heat exchange calculations need to be performed by professional personnel. If the design of the heat exchanger is accurate, it is performed according to the formula, but In most cases it is impossible to make the heat lengths exactly equal, so there will be a superheated surface area.
Ⅲ. Flow rate requirements
The large flow rate end of the plate heat exchanger is determined by the sum of the flow rates that may pass through the channel without exceeding the pressure drop limit. In the case of most media being water and other low flow rates, the interface pressure drop and interface speed are the limiting factors. The interface size of most brand plate heat exchangers is 300mm.
Ⅳ. The pressure drop requirements
The pressure drop plays an important role in the design of the plate heat exchanger. Due to the expensive construction of the pump and the limitation of the processing process, the pressure drop has been limited. Therefore, it is very important to effectively use the total pressure drop, and the plate pressure drop loss occurs near the hole and in the channel. If a multi-process system is used, the pressure drop is greatly increased.
Therefore, it is recommended to use a single-process system as much as possible to achieve a good heat exchange effect. The pressure drop generated by the channel is due to the friction between the medium and the plate, and it increases with the flow velocity in the channel. Generally speaking, the pressure is proportional to the square of the flow rate of the channel, and the channel generates heat transfer. Partly, therefore, the pressure drop near the hole and the interface should be kept small. According to experience, it cannot exceed 30% of the total pressure drop.
V. Pressure and temperature limit requirements
The plate heat exchanger is made of thin material, so it cannot withstand the changes in the longitudinal section and the problems caused by vibration, fatigue, and thermal effects. However, the thin plate material does limit the pressure and temperature limits of the plate heat exchanger. This problem is relatively solved by the direction of the corrugated pattern on the adjacent plate. There are many supporting points where the wave pattern of the plates are staggered, thus increasing the mechanical strength of the heat exchanger.
Ⅵ. blocking tendency requirements
Blocking is a phenomenon that heat exchangers can encounter. Blocking occurs when a material with low thermal conductivity is formed on the surface of the heat exchanger, because the resistance of the heat exchange system is increased by the silver color, so the heat exchange rate is reduced. And when the flowable interface path is reduced, the pressure drop will increase.
The plate heat exchanger is less likely to block, because the medium is evenly distributed, the degree of turbulence is high, and the surface of the plate is smooth. At the same time, the use of highly corrosion-resistant materials to manufacture flat plates can also reduce blocking.
Ⅶ. Performance requirements for maintenance and other conditions
Plate heat exchangers have certain advantages in maintenance. It is easy to detect blockages and corrosion, chemical and mechanical cleaning, and easy to repair.
As long as the frame and interface are appropriate, the heat exchange capacity can be expanded by increasing the number of plates. The bolt structure of the plate heat exchanger can meet the requirements of another working condition by increasing the length of the bearing rod. As long as the plates and gaskets are suitable for the new process fluid, the plate heat exchanger can be used for other purposes.
The technology level of plate heat exchangers has gradually improved, and the power consumption has become less and less, which has more satisfied the needs of most customers, whether in domestic heating or chemical processes. The system is more simplified, saving investment and operating costs. It is in line with the current energy conservation and emission reduction policies and deserves vigorous promotion.