The plate heat exchanger has a compact structure, high heat exchange efficiency, small heat loss, large heat transfer area and heat transfer coefficient per unit volume. It is a new type of high-efficiency heat exchanger stacked by a series of metal sheets with a certain corrugated shape. A thin rectangular channel is formed between the plates for heat exchange. Compared with the shell and tube heat exchanger, the heat transfer coefficient is much higher under the same flow resistance and pump power consumption. What are the advantages of heat exchangers compared to shell and tube heat exchangers?
(1) High heat transfer coefficient. Since different corrugated plates are inverted to form a complicated flow channel, the fluid flows in a three-dimensional rotation in the flow channel between the corrugated plates. Turbulence can be generated at a low Reynolds number (generally Re = 50 ~ 200), so the heat transfer coefficient is high, which is generally considered to be 3 to 5 times that of the shell and tube type.
(2) Easy to clean. As long as the frame type plate heat exchanger is loosened, the plates are removed for mechanical cleaning, which is very convenient for the heat exchange process that requires frequent cleaning of equipment.
(3) The logarithmic average temperature difference is large, and the end temperature difference is small. The two fluids in the shell-and-tube heat exchanger cross-flow in the tube side and the shell side, and the correction coefficient of the log average temperature difference is small. Plate heat exchangers are mostly co-current or counter-current, and their correction factors are usually around 0.95. The flow of cold and hot fluid in the plate heat exchanger is parallel to the heat exchange surface and there is no side flow. Therefore, the temperature difference at the end of the plate heat exchanger is small, and the heat transfer to water can be lower than 1 ° C. The shell and tube heat exchanger is generally 5 ° C.
(4) Small footprint. The plate heat exchanger has a compact structure, and the heat exchange area per unit volume is 2 to 5 times that of the shell and tube type. It is also different from the shell-and-tube type in that it needs to reserve a maintenance place for drawing out the tube bundle. Therefore, to achieve the same heat exchange capacity, the area of the plate heat exchanger is about 1/5 ~ 1/8 of the shell and tube heat exchanger.
(5) Low price. Using the same material and the same heat exchange area, the price of plate heat exchanger is about 40% ~ 60% lower than that of shell and tube.