Plate-fin heat exchanger working principle
Plate-fin heat exchangers use flat plates and fins as heat exchangers for heat transfer elements. It is mainly composed of a bundle of plates and a head. There are several channels in the bundle. Fins are placed between the two plates of each channel and sealed with seals on both sides. Depending on the way the fluid flows, the cold and hot fluid passages are stacked, aligned and brazed into one piece, ie, bundled. The two fluid flow modes include countercurrent, crossflow and wrong counterflow.
Commonly used fins are available in the form of straight, porous, serrated and corrugated.
The main advantages of the plate-fin heat exchanger are: 1 high efficiency. Due to the disturbance of the fluid by the fins, the boundary layer constituting the thermal resistance is continuously updated, and the heat transfer coefficient is generally three times that of the shell-and-tube heat exchanger; and at a small temperature difference (1.5 to 2 ° C), the heat (cold) amount The recycling effect is good. It works best for gas-gas heat exchange. 2 compact. Since most of the heat is transferred through the fins through the flat plate, the heat transfer area per unit volume of the equipment can reach 1500 m / m. 3 Light weight When the heat transfer area is the same, the weight is close to 1/5 of the shell-and-tube heat exchanger. 4 sturdy. Since the bundle is a one-piece piece and the fins support between the two plates, they can withstand higher working pressures. In addition, simultaneous heat transfer of multiple fluids can be achieved in the same device.
However, the plate-fin heat exchanger has a narrow passage and is easy to block, which is difficult to clean and repair, and the manufacturing process is complicated. It is mostly made of aluminum alloy, and can also be made of copper, stainless steel and titanium. Because aluminum has good low temperature performance and light weight, aluminum plate-fin heat exchangers are especially suitable for deep cryogenic equipment such as oxygen, ethylene and helium liquefaction, and can also be used in power plants. Aluminum plate-fin heat exchangers are typically used where the design pressure is less than 6.3 MPa and the design temperature is +200 to -270 °C. China, the United States, the United Kingdom, and Japan have all produced plate-fin heat exchangers. The development trend of plate-fin heat exchangers is to improve fin precision and brazing quality, increase varieties and specifications, and strengthen research on fin performance, multi-stream flow and heat transfer mechanism under phase-change conditions.