Whats the difference between flooded and non flooded shell and tube type of evaporators?
Answer:
I guess you are referring to a tube and shell arrangement, and by evaporators, that you mean a refrigeration system. The flooded (Liquid filled) shell will definitely have a better heat transfer ability for cooling the tubes. The flooded shell is generally only flooded to the point of covering the tubes and the top of the vessel is constructed as a separator to prevent liquid carryover from the vapor line.
I am familiar with a propane refrigeration system used in a gas processing plant. The refrigeration compressor has a suction pressure setpoint, which controlls the pressure of the vapor of the evaporator (chiller). The level in the chiller is controlled by a simple level control valve that feeds the propane into the shell side. If the evaporation occurs faster, it just feeds faster. The liquid in the shell makes for good heat transfer and since it is at it's boiling point, is also agitated, which also helps for good heat transfer.
Evaporators are not only used in refrigeration. How do you think the cheap concentrated orange juice you can buy is made? It is sent through evaporators to evaporate some of the water. An evaporator is, at its simplest, a coil sitting in a bath of hot liquid. As the tub-side liquid passes through, some (or all) of the liquid will evaporate. You can ofcourse have the heating medium in the tubes, and the liquid to be evaporated in the shell.
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