The plate heat exchanger is a high-efficiency heat exchanger made up of a series of metal sheets with a certain corrugated shape. The plate heat exchanger is a partition wall heat exchanger. The cold fluid transfers heat through the heat exchanger plates, and the fluid directly contacts the plates. The heat transfer methods are heat conduction and convection heat transfer. The key to improving the heat transfer efficiency of the plate heat exchanger is to increase the heat transfer coefficient and the logarithmic average temperature difference.
(1) Increasing the heat transfer coefficient of the heat exchanger is to increase the surface thermal coefficient of the plates on both sides of the cold and heat, reduce the thermal resistance of the scale layer, and select plates with high thermal conductivity to reduce the thickness of the plates.
(2) Increase the logarithmic mean temperature difference
Plate heat exchangers have counter-current, co-current and mixed-flow types. Under the same working conditions, the logarithmic mean temperature difference is large in countercurrent flow and small in downstream flow, and the mixed flow pattern is between the two. The method to increase the logarithmic average temperature difference of the heat exchanger is to use countercurrent or mixed flow as much as possible, increase the temperature of the hot side fluid as much as possible, and reduce the temperature of the cold side fluid.
(3) Determination of the position of the inlet and outlet pipes
For the plate heat exchanger arranged in a single process, the fluid inlet and outlet pipes are arranged on the side of the fixed end of the heat exchanger for convenient maintenance. The greater the temperature difference of the medium, the stronger the natural convection of the fluid, and the more obvious the impact of the formed retention zone. Therefore, the inlet and outlet positions of the medium should be arranged according to the hot fluid up and down, and the cold fluid up and down to reduce the impact of the stagnation zone and improve the heat transfer efficiency.