Blowing VS sucking type fans

[A.Mortezania]

Dear Friends,

As you know most evaporator and condenser fans are sucking type fan instead blowing type fan.
I now these rules :
1 – In some cases Fan of condensers sucks air and throws it on semi-hermetic compressor and maybe help to cool these compressors better (Most of compressors such as hermetic and scroll types are suction cool and they be cool just by suction return and no need to cool by condenser fan)

2 – Fan and evaporator coil should have counter-current flow to reach to maximum heat transfer (We can change structure of coil, Put suction collector near to inlet air of blowing fan then twice this type of evaporator would be counter-current)

If we put these two above topics away, Why most (or always) fan of condensers/evaporators are sucking type instead blowing type ?

Sincerely yours.

[Brian_UK]

The reason you want to use draw-thru air flow is due to the uniform flow pattern this creates over a coil. A blow-thru design has areas of the coil where higher air velocity occurs directly in front of the fan. On those adjacent areas farther away from the fan discharge the air velocity will tend to be much lower.

The different air flow patterns through the coil affect the heat transfer and eventually the capacity is degraded.

Mind you, there is a manufacturer who created a blast freezer that reduced cooling times by reversing the airflow so that each end of the cooling chamber received the coldest air at alternative times.

[narkom]

Induced-draft design provides more even distribution of air across the bundle, since air velocity approaching the bundle is relatively low.
This design is better suited for exchangers designed for a close approach of product outlet temperature to ambient-air temperature.
Induced-draft units are less likely to recirculate the hot exhaust air.

[cadwaladr]

Sucking air over the condensor is the only way even as you say some compressors are suction cooled moving the air around a compressor does no harm only benefits it's operation.

[Rob White]

.

At a more basic level it also helps with maintenance.
Trying to clean a condenser or evaporator on the inside
of the housing is a nightmare so having the dirt, dust and
Debris on the outside is a lot easier to clean.

Rob

.

[A.Mortezania]

Thanks guys for your clear replies

[B G Scott]

Do a little test for your self, place a smoke generator on the suction side of a fan and observe the ait flow in and out, you will see the turbulent nature of the air on the discharge side.