Fri, 20 Jul 2018 07:31:45 +0000
Brazed plate heat exchanger
Brazed plate heat exchanger is a new type of high efficiency heat exchanger which is vacuum brazed by a series of metal sheets with a certain corrugated shape. A thin rectangular channel is formed between the various sheets, and heat is exchanged through the sheets. Compared with the conventional shell-and-tube heat exchanger, the heat transfer coefficient is much higher under the same flow resistance and pump power consumption, and there is a tendency to replace the shell-and-tube heat exchanger within the applicable range.
A wall-mounted heat exchanger in which a heat transfer surface is formed by a sheet material. This type of heat exchanger is compact in structure and has a large heat transfer area per unit volume. The main types are:
1.Spiral plate heat exchanger: It is made of two parallel metal plates which are kept at a certain interval, and the cold and hot fluids respectively flow in the spiral passages on both sides of the metal plate. The heat transfer coefficient of the heat exchanger is high (about 1 to 4 times higher than that of the shell-and-tube heat exchanger), and the average temperature difference is large (because the cold and hot fluids can be completely countercurrent flow), the flow resistance is small, and the knot is not easy to knot. Scale; but maintenance is difficult. The use pressure does not exceed 2 MPa.
2. Flat heat exchanger： A corrugated sheet of a certain shape and a gasket are alternately laminated and assembled by frame clamping. The cold and hot fluids respectively flow through the flow channels on both sides of the corrugated plate, and exchange heat through the plates. The corrugated board is usually made of a thin plate of stainless steel, aluminum, titanium, molybdenum or the like having a thickness of 0.5 to 3 mm. The advantage of the flat heat exchanger is that the heat transfer coefficient is high (about 2 to 4 times higher than that of the shell-and-tube heat exchanger), it is easy to remove and wash, and the number of plates can be increased or decreased to adjust the heat transfer area. The operating pressure is usually not more than 2 MPa and the operating temperature is not more than 250 °C.
3. Plate fin type heat exchanger: They are composed of heat exchanger plates bundled in a header tank with inlet and outlet of cold and hot fluids. The bundle of plates is alternately laminated by flat plates and corrugated fins and brazed. The cold and hot fluids flow through the sides of the plate to exchange heat, and the fins increase the heat transfer area, which promotes the turbulence of the fluid and enhances the equipment. The plate-fin heat exchanger has a very compact structure (heat exchange area of 4400 m2/m3), good heat transfer effect and pressure of up to 15 MPa. However, its manufacturing process is complicated, the flow path is small, and the internal leakage is not easy to repair, so it is limited to clean non-corrosive fluids, such as heat exchangers for air separation.
Key words: Brazed plate heat exchange, heat exchanger vacuum brazing, heat exchanger, Plate fin type heat exchanger, Flat heat exchanger,