Shrouding clouds the issue, and well sealed shroud should reduce the physical advantage push has. But then so does the shape and seal, even 'ducting tighness' of 'ducted fan' type fans (which auto may not use, I'm also discussing computer fans, these issues have to do with static pressure also). Without shrouds, with leakage, push has clear flow advantages. But of course is bad for front rad in car if shrouded (since vehicle-speed flow is like extra fan capacity). Even with sealed shroud, pull should never do better, (unless at front) unless you are giving system some 'unfair" advantage overall. The 'funneling affect' works both ways because push still creates low pressure on intake side, but is better equipped to 'jump gaps' and creating positive pressure differential and should give pull no advantage. Push has a 'flow shear' advantage, that is basic advantage, that can be mostly negated if there is indeed a 'funnel shape' with large intake area. But in a straight 'tube', with 'gaps' (of certain dimensions) push (over-pressure) will flow air better than pull (under-pressure), due to shearing advantage. Flow of entire system can be super complicated with eddies, back-pressures, etc. In the end, it's really impossible to generalize, everything depends on everything, lol. But with simpler unshrouded systems, push should have at least a very small advantage. It should be noted that push has enormous flow advantage at higher pressure and greater restrictions...but this may have little (marginal) to do with a particular setup. This is easy to understand if you imagine a high flow fan connected to the end of a long tubular duct. It can push are through dramatically higher flow than it can pull it. This is because in push config is has several times the 'intake flow area', and only atmospheric pressure to create flow across any give intake area. . There seem to actually be 2 advantages to push 1. It can 'jump gaps' due to flow-column aka 'air curtain' affects. 2. 'unrestricted intake/atmospheric pressure leverage' as described in long duct example. An open fan intake can flow nearly spherical, where exhaust of fan is more columnar. If you restrict the intake with a rad you are working against this advantage, though again, it may be marginal due to particulars. The columnar exhaust will perform better (than the 'spherical intake) against a rad if no shrouds, or leaky shrouds, are used.
i can’t think of anyone putting shrouding in front of a radiator pusher fan or not. technically you’d still shroud the back to pressurize the shroud so air is drawn across the entire radiator
That's a is very simple that any Car Guy knows; Puller Fans as the Primary Cooling/AC fan. You can have an Auxiliary Pusher fan for additional AC cooling but not as the primary fan.
This is optimal as presented if you are running the fans all the time which street and race cars do not do (see explanation below). Performance street and race car fans work on a thermostat and therefore do not come until a set temp. That temp is not generally reached until your coolant temp is above 200 F. This does not happen except sitting stationary or moving slowly in traffic. Not things that happen on a race track. Once the car is moving at a reasonable speed the air moving through the radiator unassisted by the fans will keep the coolant temp in a happy place no fans needed. If you block all airflow except the area exposed to the puller fans, lets say that area is 70% of the total radiator surface area: Now you have choked 100% radiator area down to 70% during driving when the fans are not used which is most of the time and with a track car it's the most important time because you are beating on the car and need all the cooling you can get when the fans are off. It's actually worse than that because the shroud holding the puller is going to cause turbulence and allow less than 70% of the air to flow through when the fans are not on. What does it all mean? Yes, puller fans are better than pushers because: * The air being pulled though is more uniform and less restricted than the air being pushed at the radiator. ** The fans are not in the way of the air flow as it flows into the radiator when the car is moving with the fans off which is most of the time. * If the puller shroud is blocking off part of the free air flow out the other side when the fans are off you negate the previous stated benefit unless you use the fans all the time which at speed is bad idea because it's less efficient an less effective than the free air flowing through without the fan.
Shrouding clouds the issue, and well sealed shroud should reduce the physical advantage push has. But then so does the shape and seal, even 'ducting tighness' of 'ducted fan' type fans (which auto may not use, I'm also discussing computer fans, these issues have to do with static pressure also). Without shrouds, with leakage, push has clear flow advantages. But of course is bad for front rad in car if shrouded (since vehicle-speed flow is like extra fan capacity). Even with sealed shroud, pull should never do better, (unless at front) unless you are giving system some 'unfair" advantage overall. The 'funneling affect' works both ways because push still creates low pressure on intake side, but is better equipped to 'jump gaps' and creating positive pressure differential and should give pull no advantage. Push has a 'flow shear' advantage, that is basic advantage, that can be mostly negated if there is indeed a 'funnel shape' with large intake area. But in a straight 'tube', with 'gaps' (of certain dimensions) push (over-pressure) will flow air better than pull (under-pressure), due to shearing advantage. Flow of entire system can be super complicated with eddies, back-pressures, etc. In the end, it's really impossible to generalize, everything depends on everything, lol. But with simpler unshrouded systems, push should have at least a very small advantage. It should be noted that push has enormous flow advantage at higher pressure and greater restrictions...but this may have little (marginal) to do with a particular setup. This is easy to understand if you imagine a high flow fan connected to the end of a long tubular duct. It can push are through dramatically higher flow than it can pull it. This is because in push config is has several times the 'intake flow area', and only atmospheric pressure to create flow across any give intake area. . There seem to actually be 2 advantages to push 1. It can 'jump gaps' due to flow-column aka 'air curtain' affects. 2. 'unrestricted intake/atmospheric pressure leverage' as described in long duct example. An open fan intake can flow nearly spherical, where exhaust of fan is more columnar. If you restrict the intake with a rad you are working against this advantage, though again, it may be marginal due to particulars. The columnar exhaust will perform better (than the 'spherical intake) against a rad if no shrouds, or leaky shrouds, are used.
i can’t think of anyone putting shrouding in front of a radiator pusher fan or not. technically you’d still shroud the back to pressurize the shroud so air is drawn across the entire radiator
Keep up the good work man
That's a is very simple that any Car Guy knows; Puller Fans as the Primary Cooling/AC fan. You can have an Auxiliary Pusher fan for additional AC cooling but not as the primary fan.
Great description
Why would anyone put a pusher set with a shroud. Shrouds are for pullers
This is optimal as presented if you are running the fans all the time which street and race cars do not do (see explanation below).
Performance street and race car fans work on a thermostat and therefore do not come until a set temp.
That temp is not generally reached until your coolant temp is above 200 F.
This does not happen except sitting stationary or moving slowly in traffic. Not things that happen on a race track.
Once the car is moving at a reasonable speed the air moving through the radiator unassisted by the fans will keep the coolant temp in a happy place no fans needed. If you block all airflow except the area exposed to the puller fans, lets say that area is 70% of the total radiator surface area:
Now you have choked 100% radiator area down to 70% during driving when the fans are not used which is most of the time and with a track car it's the most important time because you are beating on the car and need all the cooling you can get when the fans are off.
It's actually worse than that because the shroud holding the puller is going to cause turbulence and allow less than 70% of the air to flow through when the fans are not on.
What does it all mean?
Yes, puller fans are better than pushers because:
* The air being pulled though is more uniform and less restricted than the air being pushed at the radiator.
** The fans are not in the way of the air flow as it flows into the radiator when the car is moving with the fans off which is most of the time.
* If the puller shroud is blocking off part of the free air flow out the other side when the fans are off you negate the previous stated benefit unless you use the fans all the time which at speed is bad idea because it's less efficient an less effective than the free air flowing through without the fan.
Incorrect sir