Blowing & suction type force convection

[Aria]

Which one the better eficiency for heat transfer, suction or blowing type for force convection?

[Tesla]

Hi Aria
For cooling I think forced convection is more efficient due to the air increasing in temp by a degree or two from pressure increase, which in turn increases temp difference. In stating that I see a lot of AHUs with induced convection. It would depend also on the characteristics of the fan curve too. In heating mode I think induced convection would be better for the same reason. That's just my thoughts but we would appreciate a design engineers opinion here please. I often asked myself the same question when I saw the two different approaches for heat transfer when I was younger.

[mad fridgie]

like most things in HVACR industry, a simple answer really can not be given.
For example on a cooling unit, it is in theory better to force the air through the evap, as far as heat load goes.The fan energy is directly absorbed by the evap, but on the other hand and generally talking inducing the air through the evap coil gives more even air distribution through the coil block, so should give a better overall heat transfer and normally allows for a greater throw of air out of the coil.

[Sandro Baptista]

The fan energy is directly absorbed by the evap,...

Only part of the energy dissipated by the fan and all energy dissipated by the motor fan, due to a non-electric efficiency.


For freezing tunnels I like to use blow type evaporator because it allows an even air outlet and the product dehydrates less.

[mad fridgie]

[QUOTE=Sandro Baptista;229655]Only part of the energy dissipated by the fan and all energy dissipated by the motor fan, due to a non-electric efficiency.

Correct, I do class a fan as the "blade and motor combination", poor choice of words, wish I was taught decent english, damn the UK education system,

[Sandro Baptista]

Don't hurry by that :) . The important is that you understand the principles.

[Aria]

So, it means, blowing and suction type is same efficiency? just depend on fan & motor fan combination?
if we talk based on type of flow (laminar & turbulent), which one of type that have better efficiency if used in condenser?