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Ways to Reduce the Resistance of Welded Heat Exchanger Fin Tube

2021-11-12
Ways to reduce the resistance of Welded Heat Exchanger Fin Tube
Increasing the average flow velocity of the medium in the plate flow channel can increase the heat transfer coefficient and reduce the area of the heat exchanger. However, increasing the flow rate will increase the resistance of the heat exchanger and increase the power consumption of the circulating pump and the equipment cost. The power consumption of the circulating pump is proportional to the third power of the medium flow rate. It is not economical to increase the flow rate to obtain a slightly higher heat transfer coefficient. When the flow of cold and hot media is relatively large, the following methods can be used to reduce the resistance of the heat exchanger and ensure a higher heat transfer coefficient.
Adopt thermal mixing plate
The geometric structure of the corrugation on both sides of the thermal mixing plate is the same. The plates are divided into hard plates and soft plates (L) according to the angle of the herringbone corrugation. The angle greater than 90° is the hard plate, and the angle less than 90° is the soft plate. The surface heat transfer coefficient of the hard plate of the thermal mixing plate is high, and the fluid resistance is large, while the soft plate is the opposite. The combination of hard board and soft board can form high (HH), medium (HL), and low (LL) runners with three characteristics to meet the needs of different working conditions.
When the flow of cold and heat medium is relatively large, the use of a heat mixing plate can reduce the plate area than a symmetrical single-process heat exchanger. The diameters of the corner holes on the hot and cold sides of the heat mixing plate are usually the same. When the flow ratio of the cold and heat medium is too large, the pressure loss of the corner holes on the side of the cold medium is large.
Adopt asymmetrical plate heat exchanger
The symmetrical plate heat exchanger is composed of plates with the same corrugated geometry on both sides of the plate, forming a plate heat exchanger with equal cross-sectional areas of the cold and hot runners. According to the heat transfer characteristics and pressure drop requirements of the cold and hot fluids, the asymmetric plate heat exchanger changes the wave geometry on both sides of the plate to form a plate heat exchanger with different cross-sectional areas of the cold and hot runners. The corner hole has a larger diameter. The heat transfer coefficient of the asymmetrical plate heat exchanger decreases slightly, and the pressure drop is greatly reduced.
Multi-process combination
When the flow rate of the cold and heat medium is large, a combination of multiple processes can be used, and more processes are used on the side of the small flow rate to increase the flow rate and obtain a higher heat transfer coefficient. On the large flow side, fewer processes are used to reduce the resistance of the heat exchanger. Mixed flow patterns appear in the combination of multiple processes, and the average heat transfer temperature difference is slightly lower. Both the fixed end plate and the movable end plate of the heat exchanger with multi-process combination are taken over, which requires a lot of work during maintenance.
When the flow of cold and heat medium is relatively large, a bypass pipe can be installed between the inlet and outlet of the heat exchanger on the side of the large flow to reduce the flow into the heat exchanger and reduce the resistance. In order to facilitate adjustment, a regulating valve should be installed on the bypass pipe. This method should adopt a countercurrent arrangement to make the temperature of the cold medium exiting the heat exchanger higher, and to ensure that the temperature of the cold medium after the confluence of the heat exchanger outlet can meet the design requirements. The bypass pipe of the heat exchanger can ensure that the heat exchanger has a higher heat transfer coefficient and reduce the resistance of the heat exchanger, but the adjustment is slightly more complicated.
Heat Exchanger Fin Tube