How to optimize the heat transfer efficiency of plate heat exchanger

In recent years, the technology of plate heat exchangers has become increasingly mature. It has high heat transfer efficiency, small size, light weight, low fouling coefficient, easy disassembly, many types of plates, and a wide range of applications. It has been widely used in the heating industry. Plate heat exchangers are divided into detachable type, welded type, brazed type, plate and shell type and so on according to the assembly method. Because the detachable Plate Heat Exchanger is easy to disassemble and clean, and the area of the heat exchanger can be increased or decreased flexibly, it is widely used in heating projects. The detachable plate heat exchanger is limited by the heat resistance temperature of the rubber gasket. Improving the heat transfer efficiency of the heat exchanger and reducing the resistance of the heat exchanger should be considered at the same time, and the plate material and rubber gasket material and installation method should be selected reasonably to ensure the safe operation of the equipment and prolong the service life of the equipment.

1. Improve heat transfer efficiency

The plate heat exchanger transfers heat through the heat exchanger plates, the fluid is in direct contact with the plates, and the heat transfer methods are heat conduction and convection heat transfer. The key to improving the heat transfer efficiency of plate heat exchangers is to increase the heat transfer coefficient and the logarithmic mean temperature difference. To improve the heat transfer coefficient of the heat exchanger, only by increasing the surface heat transfer coefficient of the hot and cold sides of the plate at the same time, reducing the thermal resistance of the dirt layer, selecting plates with high thermal conductivity, and reducing the thickness of the plates can the heat transfer be effectively improved. The heat transfer coefficient of the device.

2. Improve the surface heat transfer coefficient of the plate

Since the corrugation of the plate heat exchanger can make the fluid turbulent at a small flow rate, it can obtain a high surface heat transfer coefficient, and the surface heat transfer coefficient is related to the geometric structure of the plate corrugation and the flow state of the medium. The waveform of the plate includes herringbone, straight, spherical and so on. After years of research and experiments, it was found that the herringbone plate with a triangular corrugated section shape (the largest sinusoidal surface heat transfer coefficient, uniform stress distribution under pressure, but difficult to process) has a higher surface heat transfer coefficient, and the corrugated The larger the included angle, the higher the flow velocity of the medium in the channel between the plates, and the larger the surface heat transfer coefficient.

3. Reduce the thermal resistance of the dirt layer

The key to reducing the thermal resistance of the fouling layer of the heat exchanger is to prevent fouling of the plates. When the scale thickness of the plate is 1 mm, the heat transfer coefficient decreases by about 10%. Therefore, attention must be paid to monitoring the water quality on both the cold and hot sides of the heat exchanger to prevent scaling of the plates and prevent impurities in the water from adhering to the plates. In order to prevent water theft and corrosion of steel parts, some heating units add chemicals to the heating medium, so attention must be paid to water quality and adhesives that cause sundries to contaminate the heat exchanger plates. If there are viscous debris in the water, special filters should be used for treatment. When choosing a medicament, it is advisable to choose a non-sticky medicament.

4. Choose plates with high thermal conductivity

Plate material can choose austenitic stainless steel, titanium alloy, copper alloy, etc. Stainless steel has good thermal conductivity, high strength, good stamping performance, is not easy to be oxidized, and its price is lower than titanium alloy and copper alloy. It is most used in heating engineering, but its resistance to chloride ion corrosion is poor.

5. Reduce the thickness of the plate

The design thickness of the plate has nothing to do with its corrosion resistance, but is related to the pressure bearing capacity of the heat exchanger. Thickened plates can improve the pressure bearing capacity of the heat exchanger. When the combination of herringbone plates is used, the adjacent plates are inverted and the corrugations are in contact with each other, forming a fulcrum with high density and uniform distribution. The sealing structure of the corners and edges of the plates has been gradually improved. Next, the smaller plate thickness should be selected as much as possible.