Refrigerated Cybertruck Frunk?

JBee

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I think the best feature of the Cybertruck is that for lack of any certainty it can be whatever we want it to be! 🤪
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ajdelange

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I won't stoop to that level to show how he minimized the surface area,
The dimensions were taken from an Amazon ad for an actual catalytic converter. I used the area of one surface because both the top and the bottom cannot be pointed at the car body.

the actual emissivity and, most fundamentally,
Fluke (they make IR cameras and non contact thermometers) list stainless steel emissivities and ranging from 0.1 to 0.8 in the NIR. The average is 0.45. I used 0.5 as it's close to the average to simplify calculation. In fact the Amazon catalytic converter loos pretty shiny in its picture so when newly installed would have an emissivity closer to 0.1 but as it got grungier with age its emissivity would rise closer to 0.5.

... the temperature.
Well I'm no catalytic converter expert, that's for sure, but a little research tells me they typically operate at 400 °C. That's 752 °F which seems reasonable to me (I had EGT sensors on my airplane but that was so long ago I can't say I really remember). As the radiation goes as the 4th power of the temperature (in Kelvins) anyone can easily calculate the relative amount at any other temperature. I've never seen the components of the exhaust system on any ICE engine I have ever owned glow (but I have seen pictures of them glowing on high performance engines) so I think we are safe in assuming that the upper bound on EGT for anything we are likely to drive on the street is 800°C (1472 °F, 1073 K). At 800 °C the radiation would be 6.46 times what it is at 400 °C or 840 W. If your catalitic converter glows you can rephrase the question to "does any one else here think a kW heater under the car is a "big radiative cabin heater"?

The biggest lie of all is one of omission. He conveniently forgot to include the exhaust manifold, acting like the catalytic converter is so close to the engine the rest of the exhaust system forward of the catalyst doesn't matter.
The entire exhaust system is like one big radiative cabin heater that the A/C system must overcome.
I did not include the manifold first because it would be much more difficult to analyze its shape being that of, well, a manifold, second because the heat radiated from it does not reach the cabin and third because, being in the engine compartment, I was thinking of it as part of the engine - not part of the exhaust system.

Anyway, if we assume the manifold is glowing a wee bit (800°C) and in free space it would radiate 53 kW/m^2. If it had a surface area of 0.25m^2 that would mean 13.3 kW. Running a MX at 65 mph takes about 20 kW and if we assume an equivalent ICE vehicle takes 3 times this much we'd WAG the heat loss from such a vehicle at 40 kW.. The estimated 13.3 kW would be an appreciable part of that which our correspondent would have us believes all flows into the cabin. But of course it doesn't. It is blocked from even the interior of the engine compartment by heat shields which reflect most of it back into the engine where it is removed by the circulating coolant and subsequently dumped out the radiator.

So it is apparent that the manifold cannot radiate to the fire wall and the heat it does in fact radiate gets picked up by the cooling system as common sense tells us. This results in an engine compartment temperature of around 100 °C. If we keep the cabin at 20 °C then there is an 80 °C drop across the firewall and if it has an R factor of even 10 the flux through it will be but 8W/m^2. I really don't have any guess as to what the R factor for a typical fire wall is but I do note that the modern SUVs do insulate the fire wall not so much for heat (which says heat really isn't a problem, though you'd never know that from the outfits that sell after market fire wall insulation for cars that don't have it) but for noise. Thus it is apparent what the common sense of readers (who have it) already knew: the major load on auto A/C is the solar one.

A question for the common sense folks: Has anyone ever noticed heat coming out from under the dash (i.e. through the fire wall) if the heater is off? Here's my vote: No, not in any car I have ever driven or been a passenger in.
 

ajdelange

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Occam's razor proposes the simplest explanation. That a small one was used as a compromise is conjecture and imo not correct.
But the simplest explanation, to an engineer, is exactly that. Now Occam's razor doesn't guarantee that the simplest explanation is the correct explanation and you can't do any experiment to prove it. It's sort of like Sutton's law. The hypothesis with the highest liklihood is the one that's most probably correct.

'Tesla can't cool its cars - sometimes.'
Depends on circumstance, and I reckon the more accurate statement would be to replace the word 'Telsa' with 'Cars'
It's even broader than that. I tried to explain earlier but this is techie stuff and non techies are going to have trouble with it. When I put a sun room on my house the inspector failed the original framing because it was not designed to handle 100 mph winds. So the contractor added bracing to get it to the point where it will handle 100 mph winds. It is now more robust than it was but it won't handle 110 mph winds.
 
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rr6013

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The only information I'm aware of for the frunk was the picture displayed at the reveal. It looks decent sized. Since this is the only information we have, we can only assume it's correct, or assume it's wrong. I chose to assume it's correct until proven false.

1654731015652.png
SO ~about same size as VW Beetle?

Ok as long as front accommodates winch/snowplow structure and/or BullBar attachment.
 

ajdelange

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Heat subjectivity Is all in your feet. I joke not.
Ever willing to apply new knowledge to a problem at hand I put my bare feet on the inside of the fire wall whilst riding in an ICE vehicle earlier today. Common sense backed by physics wins again. No heat coming through from manifold or any other part of the engine.

And where was I going in an ICE vehicle? Why to the Tesla shop to pick up my X in for another repair (12V battery died).
 


HaulingAss

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The dimensions were taken from an Amazon ad for an actual catalytic converter. I used the area of one surface because both the top and the bottom cannot be pointed at the car body.

Fluke (they make IR cameras and non contact thermometers) list stainless steel emissivities and ranging from 0.1 to 0.8 in the NIR. The average is 0.45. I used 0.5 as it's close to the average to simplify calculation. In fact the Amazon catalytic converter loos pretty shiny in its picture so when newly installed would have an emissivity closer to 0.1 but as it got grungier with age its emissivity would rise closer to 0.5.

Well I'm no catalytic converter expert, that's for sure, but a little research tells me they typically operate at 400 °C. That's 752 °F which seems reasonable to me (I had EGT sensors on my airplane but that was so long ago I can't say I really remember). As the radiation goes as the 4th power of the temperature (in Kelvins) anyone can easily calculate the relative amount at any other temperature. I've never seen the components of the exhaust system on any ICE engine I have ever owned glow (but I have seen pictures of them glowing on high performance engines) so I think we are safe in assuming that the upper bound on EGT for anything we are likely to drive on the street is 800°C (1472 °F, 1073 K). At 800 °C the radiation would be 6.46 times what it is at 400 °C or 840 W. If your catalitic converter glows you can rephrase the question to "does any one else here think a kW heater under the car is a "big radiative cabin heater"?



I did not include the manifold first because it would be much more difficult to analyze its shape being that of, well, a manifold, second because the heat radiated from it does not reach the cabin and third because, being in the engine compartment, I was thinking of it as part of the engine - not part of the exhaust system.

Anyway, if we assume the manifold is glowing a wee bit (800°C) and in free space it would radiate 53 kW/m^2. If it had a surface area of 0.25m^2 that would mean 13.3 kW. Running a MX at 65 mph takes about 20 kW and if we assume an equivalent ICE vehicle takes 3 times this much we'd WAG the heat loss from such a vehicle at 40 kW.. The estimated 13.3 kW would be an appreciable part of that which our correspondent would have us believes all flows into the cabin. But of course it doesn't. It is blocked from even the interior of the engine compartment by heat shields which reflect most of it back into the engine where it is removed by the circulating coolant and subsequently dumped out the radiator.

So it is apparent that the manifold cannot radiate to the fire wall and the heat it does in fact radiate gets picked up by the cooling system as common sense tells us. This results in an engine compartment temperature of around 100 °C. If we keep the cabin at 20 °C then there is an 80 °C drop across the firewall and if it has an R factor of even 10 the flux through it will be but 8W/m^2. I really don't have any guess as to what the R factor for a typical fire wall is but I do note that the modern SUVs do insulate the fire wall not so much for heat (which says heat really isn't a problem, though you'd never know that from the outfits that sell after market fire wall insulation for cars that don't have it) but for noise. Thus it is apparent what the common sense of readers (who have it) already knew: the major load on auto A/C is the solar one.

A question for the common sense folks: Has anyone ever noticed heat coming out from under the dash (i.e. through the fire wall) if the heater is off? Here's my vote: No, not in any car I have ever driven or been a passenger in.
bla, bla, bla...
 

Crissa

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I think there is about a zero chance the Cybertruck's frunk will mimic the Lightening's frunk. The only way Cybertruck's frunk could do that would be to make the hood level like the Lightning's. And we know the top of the hood will be slanted, not level.
Also, remember at the lowest suspension height setting, the top of the Cybertruck nose is within a couple inches of the floor the Lightning frunk.

It would be cool if the bumper crush zone lifted, but... Not even the Lightning does that.

-Crissa
 

SparkChaser

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Also, remember at the lowest suspension height setting, the top of the Cybertruck nose is within a couple inches of the floor the Lightning frunk.

It would be cool if the bumper crush zone lifted, but... Not even the Lightning does that.

-Crissa
Just the grill, but that makes a big difference when sliding in a heavy box.

Tesla Cybertruck Refrigerated Cybertruck Frunk? K2IGMLB4F5DH7ILLDAAC3RNYKE
 

charliemagpie

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With the back full of whatever it is we put in work trucks.

MAYbe,,,,

A frunk fold down BBQ

That is what you do when you no longer have an ICE vehicle, but still include a front Grill lol


Tesla Cybertruck Refrigerated Cybertruck Frunk? 1654825051297
 


JBee

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Not if you could just... not have a grill?

-Crissa
lol I get it now.
If I simply didn't have a grill then Crissa wouldn't have to always be up in it? ;);):ROFLMAO:
 

JBee

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Ever willing to apply new knowledge to a problem at hand I put my bare feet on the inside of the fire wall whilst riding in an ICE vehicle earlier today. Common sense backed by physics wins again. No heat coming through from manifold or any other part of the engine.

And where was I going in an ICE vehicle? Why to the Tesla shop to pick up my X in for another repair (12V battery died).
The feet temperature "feeling" is a physiology thing, where the temperature of the body extremities dictates how one perceives body temperature, as these are also the parts of the body that have the worst and most distant circulation from the heart, and as such are the hardest to heat or cool. A bit like sitting in the back seat of an EV with the A/C condenser at the front.

So one of the tricks is to make sure you have good foot temperature control, so things like hydronic floor heating in houses actually mean you can have a couple of degree lower thermostat temperature without reducing comfort, because heat is being directly applied to where your body is coldest and it can't heat effectively. So if you want to save some energy dollars and save the planet to boot, for goodness sake put on some socks! 😎

Alternatively, placing them on a firewall can help too, but just make sure that firewall isn't on fire first, because of them pesky engine manifolds! Of course placing your "bear" feet on them is fine though. :rolleyes::LOL:
 

JBee

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So now I'm on the search for Model Y accessories... I would like a custom fit refrigerator for the MY frunk, or a conversion kit to make the frunk into a fridge. I've dabbled in some non-cfc systems before, but I'm looking for something easy and efficient to install, possibly even removeable, but if I have it I suppose I can also put stuff in there without turning it on.

Anyone know of a good aftermarket fridge that fits snug in the frunk?

I'm thinking that tapping the A/C line and putting a refridgerant to glycol or air heat exchanger on there would void the warranty and be expensive as a retrofit. Problem with that too is the car has to be on to run it, or in dog mode at least. If I do a self contained one with its own compressor it can run whenever, probably with less power, and without the car on, plus without voiding the warranty.

So now I have to start looking at MY disassembly videos to get an idea how much space is under the frunk tub. Should make for a decent little side project and something that could be transferred to a CT frunk too.
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