The heat transfer coefficient can be increased and the area of Heat Exchanger can be reduced by increasing the average velocity of medium in the flow channel between plates.However, increasing the flow rate will increase the resistance of the heat exchanger, and increase the power consumption and equipment cost of the circulating pump.The power consumption of circulating pump is proportional to the third power of medium flow rate. It is not economical to obtain a slightly higher heat transfer coefficient by increasing the flow rate.When the flow of hot and cold medium 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 hot mixing plate
The corrugated geometrical structure of the two sides of the hot mixing plate is the same. The plate is divided into hard plate (H) and soft plate (L) according to the included Angle of herringbone corrugated, and the included Angle (generally 120).> 90.Is a hard plate, including an Angle (generally 70.Left and right) less than 90.For soft board.The surface heat transfer coefficient of hot mixing plate hard plate is high, the fluid resistance is large, the soft plate is opposite.Hard plate and soft plate can be combined to form high (HH), medium (HL), low (LL) three characteristics of the flow channel, to meet the needs of different working conditions.
When the flow rate of hot and cold medium is relatively large, the hot mixing plate is used instead of symmetric single flow
The heat exchanger can reduce the plate area.The diameter of the corner holes on both sides of the hot and cold mixing plate is usually equal. When the flow ratio of the hot and cold medium is too large, the pressure loss of the corner hole on the side of the cold medium is great.
Asymmetric Plate heat exchanger is used
The symmetrical Plate Heat Exchanger is composed of the same corrugated geometrical structure on both sides of the plate, forming a plate heat exchanger with the same cross-sectional area of cold and hot flow channels.According to the heat transfer characteristics and pressure drop requirements of hot and cold fluids, the asymmetrical plate heat exchanger changes the geometrical structure of the two sides of the plate and forms the plate heat exchanger with different cross-sectional areas of the hot and cold flow channels. The corner hole on one side of the wide flow channel is larger in diameter.The heat transfer coefficient of the asymmetric plate heat exchanger decreases slightly, and the pressure drop decreases greatly.
Adopt multi-process combination
Can use multi-process combination arrangement, when the flow of hot and cold medium is large.In order to increase the flow rate and obtain a higher heat transfer coefficient, more processes are used on the side of small flow.The large flow side uses less flow to reduce heat exchanger resistance.The multi-flow combination presents a mixed flow type, and the average heat transfer temperature difference is slightly lower.The fixed end plate and the movable end plate of the multi-flow combination plate heat exchanger have nozzles, and the workload is large during maintenance.
A heat exchanger bypass pipe is provided
When the flow rate of the hot and cold medium is relatively large, a bypass pipe can be set at the inlet and outlet of the heat exchanger on the side of the large flow rate to reduce the flow rate into the heat exchanger and reduce the resistance.In order to facilitate adjustment, a regulating valve should be installed on the bypass pipe.The countercurrent arrangement should be adopted to make the temperature of the cold medium outlet heat exchanger higher and ensure that the temperature of the cold medium after the outlet of the heat exchanger confluent can meet the design requirements.The heat exchanger bypass pipe can ensure the heat exchanger has a higher heat transfer coefficient, reduce the heat exchanger resistance, but the regulation is a little complicated
