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It is not very necessary but it is positioned like this because to make most of the moisture as low as possible in order to remove water droplets from air. As water enters the coil it is at lowest temp so most of the moisture is removed by most cooled coil
Hope this works
The reason behind that is the difference in the density between (chilled-in) and (chilled-out) water due to the Temperature difference of them,as a consequent,they put the water out which has less weight in the top of the coil.
Because this path from bottom to top consumes much time than from top to bottom; thereby reulting in effective heat exchange between the two media, chilled water that takes up the heat & air that evetually gives desired cooling.
not only in FCU but also in AHU,FAHU and HRU
it make it easer to guide all the air to the top(if any) and not to obstruct the natural flow of the air were it will produce turbulance in water. beside that this way is matching the standards of heat exchanger.
To have maximum Energy exchange
To let max air (If present) purge out of system
Universally applied for all Energy exchange systems.
Water enters from down going to up to insure full wet for whole internal cross section area of coil pipe in order to fill pipe with water completly without leaving any empty position inside the pipe that water can not reach.
In & out connections either be up & down. actually it depends upon direction of Flow from AHU fan. CHW return always be from Fan Air Flow direction being logic that the Air Temperature should decrease gradually from higher Temperature i.e CHW return to Lower Temperature i.e CHW Supply to avoid Turbulence. Therefore Air Flow from FAN must touch first CHW return pipe either it is up or down,it only depends upon Coil manufacturing.
It is very simple that when water travel from the bottom of the coil it reaches to the above outlet it exchange
the heat and condense the moisture.
Because of two reasone
thanks everyone i really appreciate your valuable reply, it is very important and useful for me,thank you again
The theory behind counter-flow, which explains why this is the case, is to keep the highest temperature difference across the coil while the air is going through it.
