中文(简体) 1、 Optimization design direction
In recent years, the technology of plate heat exchanger is becoming more and more mature. Because of its high heat transfer efficiency, small volume, light weight, low fouling coefficient, convenient disassembly, many kinds of plates and wide application range, it has been widely used in the heating industry. Plate heat exchanger can be divided into detachable type, welding type, brazing type, plate shell type, etc. Because the detachable plate heat exchanger is easy to disassemble and clean, and the area of the heat exchanger is flexible, it is widely used in heating engineering. The removable plate heat exchanger is limited by the heat-resistant temperature of rubber gasket and is suitable for water-water heat transfer. This paper studies the optimal design to improve the efficiency of movable plate heat exchanger.
Improving the efficiency of plate heat exchanger is a comprehensive economic benefit problem, which needs to be determined after technical and economic comparison. At the same time, consider improving the heat transfer efficiency of the heat exchanger and reducing the resistance of the heat exchanger, and reasonably select the sheet material, rubber gasket material and installation mode to ensure the safe operation of the equipment and prolong the service life of the equipment.
2、 Yes,. Optimization design method
2.1 improve heat transfer efficiency
Plate heat exchanger is a kind of wall heat exchanger. Hot and cold fluids transfer heat through the plates of the heat exchanger. The oil is in direct contact with the plate. The heat transfer modes are heat conduction and convective 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 In order to improve the heat transfer coefficient of the heat exchanger, only increasing the surface heat transfer coefficient on both sides of the plate, reducing the thermal resistance of the dirt layer, selecting the plate with high thermal conductivity and reducing the thickness of the plate can effectively improve the heat transfer coefficient of the heat exchanger.
A. Improving the heat transfer coefficient of flat plate surface
Because the ripple of the plate heat exchanger can make the fluid turbulent under small flow (Reynolds number - 150), higher surface heat transfer coefficient can be obtained. The surface heat transfer coefficient is related to the geometric structure of the plate ripple and the flow state of the medium. The plate waveform includes herringbone, flat, spherical, etc. after years of research and experiments, it is found that the cross-section shape of the ripple is triangular (sinusoidal), surface heat transfer coefficient, small pressure drop and uniform stress distribution under pressure. However, herringbone plate with difficult processing has higher surface heat transfer coefficient. The larger the included angle of ripple, the higher the medium velocity in the channel between plates and the larger the surface heat transfer coefficient.
B reduce the thermal resistance of the dirt layer
The key to reduce the thermal resistance of fouling layer of heat exchanger is to prevent fouling of plate heat exchanger. When the plate thickness is 1mm, the heat transfer coefficient decreases by about 10%. Therefore, attention must be paid to monitoring the water quality on both sides of the heat exchanger to prevent scaling and sundries in the water from adhering to the plate. Some heating devices add chemicals to the heating medium to prevent water loss and steel corrosion. Therefore, it must be noted that water quality and viscous agents will cause impurities to pollute the heat exchanger plate. If there are viscous impurities in the water, it shall be treated with a special filter. When selecting agents, non viscous agents shall be selected.
C select plates with high thermal conductivity
Austenitic stainless steel, titanium alloy and copper alloy can be selected as plates. Stainless steel has good thermal conductivity, the thermal conductivity is about 14.4w / (m · K), high strength, good stamping performance, not easy to oxidize, and the price is lower than that of titanium alloy and copper alloy. It is mainly used in heat supply engineering, but its resistance to chloride ion corrosion is poor.
