New fan efficiency opinion

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I bought a new fan for my car - Derale 17119. I don't need a new on but I like to have extra stuff and it is cheap enough to have as a spare. The fan in my car is 19" and very likely not original.
Comparing the new and old fans, the dimensions are the same but the notable difference is that the old one has a continuous curved blade while the new one has it bended in three straight sections - probably the difference is due to manufacturing costs. Now my question is, will there be a difference in efficiency between them? The basic difference seems to be how the blade is curved. I don't know if the leading and trailing angles are the same. In the picture the old one is on the left and the new one on the right.

20220115_105341.jpg
 

Tnfastbk

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Here is a simple explanation of your question

Optimisation of efficiency of axial fans

N.P. Kruyt, ... R. Faasen, in Fluid Machinery Congress 6-7 October 2014, 2014

6 WINDTUNNEL TESTING​

Prototypes of the new fan blades have been manufactured and tested in the windtunnel at Vostermans Ventilation. Here the angular velocity Ω of the impeller, the flowrate Q, the fan torque T and the static pressure difference Δp between chamber at inlet and at outlet have been measured. The power required to run the fan (excluding the electrical motor) is given by
(5)Pin=ΩT
The flow rate Q and the pressure rise ∆p are expressed in nondimensional form by the flow coefficient φ and the pressure rise coefficient ψ
(6)φ=v¯xutipψ=Δp12ρutip2
where the (mean) axial velocity v¯x=Q/A.
The efficiency ηtt* is based on measured quantities (i.e. flowrate Q, angular speed Ω, torque T, pressure rise ∆p), and accounts for the power required to increase the pressure and to accelerate the fluid. It is defined by
(7)ηtt*=QΔp+12ρv¯x2Pin
The measured pressure rise ∆p as a function of flowrate Q is shown in dimensionless form in Figure 3 (left), while the efficiency ηtt* is shown in Figure 3 (right). Results are shown for the original reference fan as well as for the optimized fan.
3-s2.0-B9780081001097500029-f02-03-9780081001097.jpg

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Figure 3. Performance characteristics of reference and optimised fan. Left: dimensionless pressure rise; right: efficiency.
These results for the efficiency show a significant increase of measured fan efficiency of about 4% of the optimised fan, in comparison with the performance of the reference fan.
Since the tip, inlet and outlet regions have not been included in the flow analysis in the preceding Section, it has not been attempted to compare the computed pressure rise and efficiency for the flow from inlet to outlet of the fan blade section (i.e. excluding inlet and outlet) with the corresponding measured values.
 
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I have the 18” version on my car and it definitely pushes more air than the original stock flex fan. Had it on my car for about 3-4 years now. I did have a problem with getting hot on a day that was over 90 degrees. But that was in stop and go crawling traffic at the Woodward Dream Cruise last year. Once I got off Woodward and on a street that I could drive at normal speed the temp went back down to normal.
 
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Here is a simple explanation of your question

Optimisation of efficiency of axial fans

N.P. Kruyt, ... R. Faasen, in Fluid Machinery Congress 6-7 October 2014, 2014

6 WINDTUNNEL TESTING​

Prototypes of the new fan blades have been manufactured and tested in the windtunnel at Vostermans Ventilation. Here the angular velocity Ω of the impeller, the flowrate Q, the fan torque T and the static pressure difference Δp between chamber at inlet and at outlet have been measured. The power required to run the fan (excluding the electrical motor) is given by
(5)Pin=ΩT
The flow rate Q and the pressure rise ∆p are expressed in nondimensional form by the flow coefficient φ and the pressure rise coefficient ψ
(6)φ=v¯xutipψ=Δp12ρutip2
where the (mean) axial velocity v¯x=Q/A.
The efficiency ηtt* is based on measured quantities (i.e. flowrate Q, angular speed Ω, torque T, pressure rise ∆p), and accounts for the power required to increase the pressure and to accelerate the fluid. It is defined by
(7)ηtt*=QΔp+12ρv¯x2Pin
The measured pressure rise ∆p as a function of flowrate Q is shown in dimensionless form in Figure 3 (left), while the efficiency ηtt* is shown in Figure 3 (right). Results are shown for the original reference fan as well as for the optimized fan.
3-s2.0-B9780081001097500029-f02-03-9780081001097.jpg

Sign in to download full-size image
Figure 3. Performance characteristics of reference and optimised fan. Left: dimensionless pressure rise; right: efficiency.
These results for the efficiency show a significant increase of measured fan efficiency of about 4% of the optimised fan, in comparison with the performance of the reference fan.
Since the tip, inlet and outlet regions have not been included in the flow analysis in the preceding Section, it has not been attempted to compare the computed pressure rise and efficiency for the flow from inlet to outlet of the fan blade section (i.e. excluding inlet and outlet) with the corresponding measured values.
Do you have access to the actual paper? I am curious about the differences between the optimized and reference?
 
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I think it is hard to determine any efficiency between these two designs without actual testing.
As I was looking around I found this paper. They tested blade pitch, distance from radiator and cowl clearance. By far, the blade pitch had the greatest effect on flowrate. The distance from radiator had some effect and the cowl clearance hardly any.
1469941499501.gif
 

Don C

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The efficiency of the fan will also be affected by whether or not a fan shroud is being used and the clearance between the blade tips and the shroud.
It's explained better in this video than I can in a post.
 
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As for the 19" on your 71 M code, that would have been put on by someone else. If your car has the original shroud, the opening is only 19", so I'm not sure how you are getting a Derale 19" fan in there.
The 18" Derale along with the Hayden fan clutch, draws a lot more air than the original 4 blade factory fan by far. A good upgrade for my car.
 
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As for the 19" on your 71 M code, that would have been put on by someone else. If your car has the original shroud, the opening is only 19", so I'm not sure how you are getting a Derale 19" fan in there.
The 18" Derale along with the Hayden fan clutch, draws a lot more air than the original 4 blade factory fan by far. A good upgrade for my car.
Geoff, the cowl had a section cut at the bottom. Then I had to cut a bit more after replacing my transmission which increased the engine angle. Overall it fits very well after cutting.
 
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Geoff, the cowl had a section cut at the bottom. Then I had to cut a bit more after replacing my transmission which increased the engine angle. Overall it fits very well after cutting.
Tony that's good to know. Actually now I remember you mentioning that before. All good then.
 
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