Electric cars and cooling drag

[JulianEdgar]

Originally Posted by aerohead

PhD Joseph Katz shared some helpful numbers in 2017.
For his 'generic' automobile of Cd 0.355:
* ' cooling drag' was 0.024.
* 'engine bay' drag was 0.048.
* or, 0.072 combined!
-------------------------------------------------------------------------------------
This would partially explain a BEV's drag advantage, as it can have an essentially 'ideal' belly pan, compared to an ICE variant of the same model.
* Underbody & Chassis is 0.085 for ICE.
--------------------------------------------------------------------------------------
General Motors pubished Cd 0.36 for the SPARK ICE, and Cd 0.325 for SPARK EV.
Delta- 35-counts.
--------------------------------------------------------------------------------------
The Coventry University Audi A2 measured:
* belly pan = 16.2-counts
* grille-block = 27.3-counts
* under wheel arch seal = 3.6-counts
-------------------------------------------------------------------------------------
Chevrolet Division published for their 2013 Malibu:
* lower grille shutters = 7-counts
* closed upper grille = 7-counts
* center outboard belly pan = 10-counts
-------------------------------------------------------------------------------------
The 2013 Dodge Dart radiator shutters were good for 0.005.
--------------------------------------------------------------------------------------
Ford published that their 1st-gen Fusion cooling system carried a 0.025 penalty.
--------------------------------------------------------------------------------------
100% grille-block on Spirit meant a delta- 0.027.
--------------------------------------------------------------------------------------
I believe that Adrian Gaylard mentioned a Land Rover with a 0.048 cooling system.
--------------------------------------------------------------------------------------
Hucho spoke of 2% drag cooling systems.
-------------------------------------------------------------------------------------
The circa 2012 IVECO Class-8 ' Glider' Tractor has a non-aspirated cooling system, using bat-wing, heat-dissipating gap-filler panels behind the cab. ) My new Energy Star refrigerator uses this technology.
-------------------------------------------------------------------------------------

There are other random numbers published. I don't have all that organized.

Sorry if I miss the point, but none of the data you have quoted gives us a percentage cooling drag for any EV, does it?

[aerohead]

Originally Posted by JulianEdgar

Sorry if I miss the point, but none of the data you have quoted gives us a percentage cooling drag for any EV, does it?

Reporting is spotty.
' figured, anyone that interested would look into it.
The 2007, Cd 0.21, Ford/Buckeye, Fusion 999, hydrogen fuel cell, Bonneville LSR car was an EV.
Cd 0.34, minus 0.024 for the cooling gives a Delta- 7.05% drag reduction with respect to the ICE Fusion it's based upon.
Spirit was simulated as a zero-porosity BEV. In its cleanest configuration, the cooling drag deletion meant a 13.17% drag reduction.
Some BEVs are not liquid-cooled. The degree of body porosity and delta-Cd would have to be taken on a case-specific basis.
With respect to the IVECO, it's obviously possible to have a liquid-cooled BEV with zero- aerodynamic drag cooling and heat-pump systems.
Presently, there's not much being reported about it in the lay literature. And what is, is complicated by the presence of active shutters.

[JulianEdgar]

Forgive me for being frustrated, but it has been said time and time again here that BEVs have very low / no cooling drag.

The only available evidence that I have been able to find does not support that.

So in response to my post, we have:

• a few acknowledgements and thoughtful posts eg the temperature ratio of coolant versus atmospheric
• a range of denials
• a lot of irrelevant information (eg cooling drag for internal combustion engine cars)
• the purported change in cooling drag for internal combustion engine cars if they were hypothetical BEVs that needed no cooling (huh?)
• people who apparently think the size of the grille represents the percentage of cooling drag
• people who think that comparing the ICE version against the BEV version of a car somehow gives percentage cooling drag for the BEV version
• people who say my sample was too small / biased / etc... but have no alternative data

- and so on.

Honestly, what is the point of trying to correct misapprehensions here with actual, real, wind tunnel data?

[freebeard]

What's the point? Indeed.

I've noticed that a few people here seem to believe that the cooling system drag of battery electric vehicles is very low, or even zero.

The original assertion wasn't supported. But you trolled up, by my count, eleven responses and sorted them into seven buckets. Three types of comments, three type of people and one thing you don't understand.

The best suggestion I see is heat pumps for cooling, which might could lead to a discussion of Tesla's Octovalve.

[JulianEdgar]

Originally Posted by freebeard

What's the point? Indeed.

The original assertion wasn't supported. But you trolled up, by my count, eleven responses and sorted them into seven buckets. Three types of comments, three type of people and one thing you don't understand.

Sorry, are you saying that people here haven't been suggesting the BEV cooling drag is zero or very low? I've lost count of posts that say, "If it were an electric vehicle then its Cd would be [and then the poster reduces the cooling drag to zero]."

I was always a bit puzzled by this, then when I saw the real figures, I realised that appears to be completely wrong.

Maybe you just don't notice what people post here?

[freebeard]

That's probably it.

I've lost count of posts that say, "If it were an electric vehicle then its Cd would be [and then the poster reduces the cooling drag to zero]."

Could you find an example? aerohead excluded?

[ME_Andy]

I take the point that EV's can have significant drag well. More cooling drag than their ICE counterparts - I have issues with that. That is all.

[ME_Andy]

The original post has been edited so this discussion is almost worthless now.

[freebeard]

Disagree.

I pointed out the typo at 5:54. It was corrected the same minute! The first pushback was an hour and a half later.

Not that I got a Thanks for my help.

[JulianEdgar]

Originally Posted by ME_Andy

I take the point that EV's can have significant drag well. More cooling drag than their ICE counterparts - I have issues with that. That is all.

I didn't say that!

I said:

"But the fact remains that cooling drag on electric cars appears to be similar, or even greater, than on traditional internal combustion engine cars."

No where is there anything in my statement about "their counterparts".

Measured cooling drag on ICE cars varies from about 0.5 per cent to about 12 per cent.

The two BEV cars for which I have data show a cooling drag of 8 and 16 per cent.

To say it again: I've noticed that a few people here seem to believe that the cooling system drag of battery electric vehicles is very low, or even zero.

I don't think that is right.