Are you sure about "no part of the fan inside the shroud".... I mean look at every vehicle made... that has a mechanical radiator fan, along with the shroud. Most if not all have the fan either partially (sbout 75%) inside the shroud or, almost the entire fan inside the shroud. I don't think you are correct on this point.
While I'm no engineer....a fan shroud allows the fan to be more efficient when pulling air across the radiator. A fan shroud is for the purposes of controlling air flow across the radiator....it (in my words) acts something like a funnel.... in that it allows the fan to pull air direclty through the radiator...in place of pulling air from a 360 degree area that surrounds an unshrouded fan.
A vehicle with with a shroud will outcool a vehicle without hands down. Add air conditiong to the mix and with no shroud you'll just see higher temps.
Look at any cooling application that has fans.... most if not all have some type of shroud. If the fan is not at least partially inside the shroud you have really lost the effectiveness of the fand shroud.
You can do a simple test... take your fan shroud off a vehcile with a mechanical fan.... on a hot day see how it runs.... in stop and go and at speed, do the same with the shroud and see what happens.
A fan shroud...allows the fan to pull air direclty across and through the radiator and condensor, it also make the fan more effecient in its operation, ..along with the fact that the fan is partially if not totally inside the shroud. If you just have a fan that sitting out there with no shroud....its not going to be nearly as efficient.
I can't say that I've ever seen any car / truck with a mechanical fan, where the fan does not have a shroud (radiator). Many of the electric fans have a mini-shroud built in to their OEM housings.
Now if you bolt a electric fan to the rear of the radiator, then I don't see much of a difference.
Not trying to argue the point, but I just can't buy the premise that an unshrouded fan is as efficient as one that is shrouded. The entire purpose of the shroud is to have the fan partially if not totally caputred inside of the shroud, if you don't do that, then I don't see why you would have a fan shroud in the first place.
I have never seen any automotive OEM application that uses a mechanical radiator fan, where you (1) did not have a radiator fan shroud, and (2) where the fan was not partially or totally inside the fan shroud. I would be interested in knowing what type of vehicle with mechanical cooling does not use a radiator fan shroud, where the fan is not partially or totally inside the shroud.
Am I to understand your point in that you are saying that no part of the fan (according to your source) should be inside the shroud itself? in other words... you should have a radiator...then a shroud...and then a fan, but no time its the fan inside the shroud? There must be more to this article like some reference to ambient temp, static air pressure in front and to the rear of the radiator, air flow...etc.
My view is that the shroud acts like a funel in that it facilitates the air way, and controls the area of "suction" of the fan, it also controls the air path or area that the fan pulls air from. With a shroud, the fan can only pull air across the radiator and condensor, it cannot "grab" air from sources in a 360 degree radius outside of the shrouds diminisions...
** Not trying to argue the point... I'm not following the point in regard to the shroud not capturing at least part of the fan blade **
I interested in understanding how you can cool more efficiently without a shroud, or without the fan blade being partially caputred by the shroud .
I'll be building a shroud for the new 350HP+ stroker 
