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Improvement of plate heat exchanger efficiency

2021-12-02Industry News428

The heat exchanger has high heat transfer efficiency, small size, light weight, low fouling coefficient, convenient assembly,

a wide range of plates and a wide range of applications, and is widely used in the heating industry. Plate heat exchanger can

be divided into removable type, welded type, brazed type, plate shell type, etc. according to the assembly mode. The detachable

plate heat exchanger is convenient for assembly and cleaning, flexible for increasing or decreasing the area of the heat exchanger,

and is widely used in heat supply projects. The removable plate heat exchanger is limited by the heat resistance temperature of the

rubber gasket, and is suitable for water to water heat transfer.

The cold and hot fluid transfers heat through the plates of the heat exchanger, which is a cross wall heat exchanger. The fluid is in

direct contact with the plate, and the heat transfer mode is heat conduction and convection 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.

To improve the heat transfer coefficient of the heat exchanger, the external heat transfer coefficient of the cold and hot sides of the plate can

only be increased at the same time. The heat transfer coefficient of heat exchanger can be effectively improved by selecting plates with high

thermal conductivity and reducing the thickness of plates.

1. The heat transfer coefficient of the fouling layer is reduced by about 10% to reduce the thermal resistance of the fouling layer. Therefore,

the key to reducing the thermal resistance of the fouling layer of the heat exchanger is to prevent the fouling of the plates. When the thickness

of plate scaling is 1mm. Attention must be paid to monitoring the water quality on both sides of the heat exchanger to prevent the plates from

scaling and to prevent impurities in the water from adhering to the plates. In order to prevent water theft and corrosion of steel parts, some heat

supply units add chemicals to the heating medium, so it is necessary to pay attention to the water quality and adhesives that cause impurities to

contaminate the heat exchanger plates. If there are viscous impurities in the water, special filters shall be used for treatment. When selecting the

medicament, it is better to select the medicament without viscosity.

2. Improve the external heat transfer coefficient of the plate The external heat transfer coefficient is related to the geometric structure of the plate

ripple and the flow state of the medium. The waveform of the plate includes herringbone, straight, spherical, etc. After years of research and experiments,

it is found that the ripple of the plate heat exchanger can make the fluid produce turbulent Reynolds number – 150 at a small flow rate, so it can obtain a

higher external heat transfer coefficient. The shape of corrugated section is triangular and sinusoidal. The external heat transfer coefficient is the largest,

the pressure drop is small, and the stress distribution is uniform when pressed, but it is difficult to process. The herringbone plate has a higher external

heat transfer coefficient, and the larger the included angle of the ripple is, the higher the medium flow rate in the flow path between the plates is, and

the greater the external heat transfer coefficient is.

3. The reduction of plate thickness is related to the pressure bearing capacity of the heat exchanger. If the plate is thickened, the design thickness of the

plate is independent of its corrosion resistance. It can improve the pressure bearing capacity of heat exchanger. When herringbone plate combination is

adopted, adjacent plates are inverted and the ripples contact each other, forming a fulcrum with large density and uniform distribution. The plate corner

piece L and edge sealing structure have been gradually improved, so that the heat exchanger has a good pressure bearing capacity. The maximum pressure

bearing capacity of domestic detachable plate heat exchanger has reached 2.5 MPa. The thickness of the plate has a great impact on the heat transfer coefficient.

When the thickness is reduced by 0.1 mm, the total heat transfer coefficient of symmetric plate heat exchanger increases by about 600 W/mK. When the pressure

bearing capacity of the heat exchanger is met, the thickness of the plate should be as small as possible.

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