There's plenty of interesting stuff going on there while I was forcing my car's rear to work finally... I need an elephant on the rear axle to find the balance if anyone is interested 'how it's going'
So let me write some words about the HX topic
CAEdevice wrote: ↑24 Sep 2019, 21:55
machin wrote: ↑24 Sep 2019, 21:26
Do you think the cooling fins on their heat exchangers are:
1, at 90 degrees to the front face of the H-Ex (so the air has to go through a sort of ‘S’ shaped path through the H-Ex) or
2, do you think they’re aligned parallel with the floor so the air flows more or less horizontally through the H-Ex?
Which assumption does Mantium Flow use? If it’s arrangement 2 that would explain why angling the heat exchanger past 45 degrees has a detrimental effect on flow...
....Looks like I might need to redesign mine....
Very good question.
I have been thinking about the fins for two years.
MVRC HXs are modeled as porous media, with Darcy coefficients referred to a local coordinate system in order to simulate fins that are NORMAL to the HX (and measurement) surface. Last year I could never make rotated HXs work (HXs were more efficient if normal to the movong direction of the car) ... so I had the same doubts.
machin points:
1. in general air-fluid radiators/HX have a core with fins normal to the flat frontal surface, although some F1 teams (I guess Mercedes) have this frontal area curved.
2. if that would be the case it would be really hard to manufacture the core because fins would need to be properly trimmed in the tanks area
In any CFD if you calculate porous media for car radiators you follow what CAEdevice explained. I had a quick look on porous media definition in MVRC cases, and it looks like that in directions other than normal, there's "0", shouldn't it be negative value to give "infinite resistance" in these directions? I had some doubts already with few of my simulations about air passing through HX.
Regarding fins behind HX - that's of course connected with back pressure, when radiator is more straight then you can see more of it's area from the back (if your outlet is big enough); with high angled ones air which went through HX "meets" the wall (upper part of sidepod or floor), and that raises locally the pressure, reducing performance of flow through. That's why fins behind radiator are there: to direct immediately the flow to the exit.
I must admit that I've chose other-way-around HX setting, and I guess I will keep it for this season (unless I won't find any elephant to sit on my RW, so I would need to redefine side/rear of the car). So because of such setting air from my radiators basically got stuck just above the floor, add to it small outlet like in Spa-spec and power loss disaster guaranteed (so let's guess what was my solution to get missing power % before Japan
)
If it comes to tight channel on the edge of the radiator - I'm still trying to fully understand that design, as it's seen on many other racecars... actually radiators were never my favorite parts in terms of racecars aero, so I need to catch up with some points here and there.
For small F1 radiator outlets I can only tell that these teams use high efficient radiator technology (double pass/microtubes) with properly calculated cooling circuits. I think you can get a feeling seeing this Ferrari (Manor) microtube intercooler:
https://www.youtube.com/watch?v=LS47125tUzk
