Regarding falling film heat exchangers
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There are three MVR evaporators in the unit; it can be observed that there are two pipes at the top of the evaporators – one is the outlet pipeline of the circulation pump, while the other pipe is directly connected to the tank below. I want to know how a falling film evaporator works and how to ensure that the liquid film falls evenly What is that pipe that bypasses the heat exchanger directly used for? I only know that the wall thickness of that tube is very thin, around 0.5mm.
Vapor exchange evaporation draws the unevaporated liquid into a film.
The even distribution of the liquid film is ensured by the liquid distributor inside the equipment as well as the verticality of the heat exchange tubes. That bypass pipe should be a vapor equilibrium line, which also helps to ensure a steady flow of the liquid
The condensate water generated by the heating and evaporation of the product stream, along with some of the steam and the steam remaining after heating the feed stream, are all separated using a separator. The condensate water flows out from the lower part of the separator and is used to preheat the product entering the stream
The liquid feed enters the dispersion disk through the feed pipe and then overflows from the gaps between its teeth; it falls onto the upper distribution disk through the gap between the dispersion disk and the retaining ring, where it undergoes initial distribution. Subsequently, it flows across the sieve plates on the upper, middle, and lower distribution disks before reaching the plate bridges of the tube sheet, from where it overflows into the downcomer, flowing down along its inner wall in a film-like manner to achieve uniform film distribution. There is also horizontal tube falling film concentration nowadays; its heat transfer coefficient is higher than that of vertical tube falling film concentration, its working principle differs significantly, and its performance in practical applications is quite good.