Shandong Zhilin Environmental Protection Technology Co., Ltd.

How can the heat transfer efficiency of a plate heat exchanger be improved?

Release time:

2020-05-13 17:13

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Plate heat exchangers are wall-type heat exchangers. Hot and cold fluids transfer heat through the heat exchanger plates. The fluids are in direct contact with the plates. Heat transfer is achieved through thermal conduction and convection. The key to improving the heat transfer efficiency of a plate heat exchanger is to improve the heat transfer coefficient and the logarithmic mean temperature difference. To improve the heat transfer coefficient of the heat exchanger, it is necessary to simultaneously improve the surface heat transfer coefficients on both the hot and cold sides of the plate, reduce the thermal resistance of the fouling layer, select plates with high thermal conductivity, and reduce the thickness of the plates to effectively improve the heat transfer coefficient of the heat exchanger.

　　How can we improve the heat exchange efficiency of plate heat exchangers? Let's have a brief introduction from our plate heat exchanger manufacturer's customer service.
　　Improving Heat Transfer Efficiency
　　Plate heat exchangers are wall-type heat exchangers. Cold and hot fluids transfer heat through the heat exchanger plates. The fluids are in direct contact with the plates; heat transfer is achieved through thermal conduction and convection. The key to improving the heat transfer efficiency of a plate heat exchanger is to increase the heat transfer coefficient and the logarithmic mean temperature difference.
　　To improve the heat transfer coefficient of the heat exchanger, it is necessary to simultaneously increase the surface heat transfer coefficients on both the hot and cold sides of the plates, reduce the thermal resistance of the fouling layer, select plates with high thermal conductivity, and reduce the thickness of the plates to effectively improve the heat transfer coefficient of the heat exchanger.
　　Reducing the Thermal Resistance of the Fouling Layer
　　The key to reducing the thermal resistance of the fouling layer in the heat exchanger is to prevent scaling on the plates. When the scale thickness on the plates reaches 1 mm, the heat transfer coefficient decreases by about 10%. Therefore, it is necessary to monitor the water quality on both the hot and cold sides of the heat exchanger to prevent scaling on the plates and prevent foreign matter from adhering to the plates. Some heating units add agents to the heating medium to prevent water theft and corrosion of steel components. Therefore, attention must be paid to water quality and the contamination of heat exchanger plates caused by adhesives. If there are viscous impurities in the water, a special filter should be used for treatment. When selecting agents, non-viscous agents should be preferred.
　　Selecting Plates with High Thermal Conductivity
　　Plate materials can be selected from austenitic stainless steel, titanium alloys, copper alloys, etc. Stainless steel has good thermal conductivity (approximately 14.4 W/(m•K)), high strength, good stamping performance, is not easily oxidized, and is less expensive than titanium alloys and copper alloys. It is widely used in heating engineering, but its resistance to chloride ion corrosion is poor.
　　Reducing Plate Thickness
　　The design thickness of the plates is not related to their corrosion resistance but to the pressure-bearing capacity of the heat exchanger. Thicker plates improve the pressure-bearing capacity of the heat exchanger. When using a herringbone plate combination, adjacent plates are inverted, and the corrugations are in contact, forming dense and evenly distributed support points. The plate corner holes and edge sealing structure have been gradually improved, giving the heat exchanger good pressure-bearing capacity. The maximum pressure-bearing capacity of domestic detachable plate heat exchangers has reached 2.5 MPa. Plate thickness significantly affects the heat transfer coefficient. Reducing the thickness by 0.1 mm increases the overall heat transfer coefficient of a symmetrical plate heat exchanger by approximately 600 W/(m•K) and an asymmetrical one by approximately 500 W/(m•K). Provided the pressure-bearing capacity of the heat exchanger is met, the thinnest possible plates should be used.
　　Improving the Surface Heat Transfer Coefficient of the Plates
　　Because the corrugations in plate heat exchangers can cause turbulence in the fluid at lower flow rates (Reynolds number ≈ 150), a higher surface heat transfer coefficient can be obtained. The surface heat transfer coefficient is related to the geometric structure of the plate corrugations and the flow state of the medium. Plate shapes include herringbone, straight, and spherical. Years of research and experiments have shown that herringbone plates with a triangular cross-section (sinusoidal surfaces have a large heat transfer coefficient and low pressure drop, uniform stress distribution under pressure, but are difficult to process) have a higher surface heat transfer coefficient. The larger the angle of the corrugations, the higher the flow rate of the medium in the inter-plate flow channel, and the greater the surface heat transfer coefficient.
　　We hope this introduction helps you understand plate heat exchangers. Please continue to follow us for more product information.

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