The brazed plate heat exchanger is a new type of high-efficiency heat exchanger made of a series of metal sheets with a certain corrugated shape stacked and brazed. Thin rectangular channels are formed between various plates, and heat exchange is performed through the plates. Compared with conventional shell-and-tube heat exchangers, its heat transfer coefficient is much higher under the same flow resistance and pump power consumption, and it tends to replace shell-and-tube heat exchangers within the applicable range.
A partitioned wall heat exchanger that uses plates to form the heat transfer surface. This type of heat exchanger has a compact structure and a large heat transfer area per unit volume. Its main types are:
① Spiral plate heat exchanger It is made of two parallel metal plates kept at a certain distance, and the cold and hot fluids flow in the spiral channels on both sides of the metal plates respectively. This kind of heat exchanger has a high heat transfer coefficient (about 1 to 4 times higher than that of a shell-and-tube heat exchanger), a large average temperature difference (because the cold and hot fluid can be used for complete countercurrent flow), small flow resistance, and is not easy to condense. Dirt; but difficult to maintain. The operating pressure does not exceed 2MPa.
② Flat-plate heat exchanger It is composed of corrugated thin plates of a certain shape and gaskets alternately superimposed, and assembled by clamping with a frame. The cold and hot fluids flow through the flow channels on both sides of the corrugated plate respectively, and exchange heat through the plates. Corrugated plates are usually punched from stainless steel, aluminum, titanium, molybdenum and other thin plates with a thickness of 0.5-3mm. The advantage of the plate heat exchanger is that it has a high heat transfer coefficient (about 2 to 4 times higher than that of the shell-and-tube heat exchanger), easy to disassemble and wash, and the number of plates can be increased or decreased to adjust the heat transfer area. The operating pressure usually does not exceed 2MPa, and the operating temperature does not exceed 250°C.
③ Plate-fin heat exchanger: It is composed of heat exchange plate bundles enclosed in a header box with cold and hot fluid inlet and outlet. The plate bundle is made of flat plates and corrugated fins alternately laminated and fixed by brazing. The cold and hot fluids flow through both sides of the plate to exchange heat, and the fins increase the heat transfer area, promote the turbulence of the fluid, and enhance the equipment. The structure of the plate-fin heat exchanger is very compact (the heat exchange area reaches 4400m2/m3), the heat transfer effect is good, and the working pressure can reach 15MPa. However, its manufacturing process is complicated, the flow channel is small, and the internal leakage is not easy to repair, so it is limited to clean and non-corrosive fluids, such as heat exchangers for air separation.