Refrigerated Cybertruck Frunk?

ajdelange

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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.
Other big problem with the Y is that the system is used as a source of heat as well as cooling so where to tap the liquid line would be a tricky question. This is the model with the Octovalve whose plumbing, or what I can see of it from Sandy Munro's video, looks pretty hairy.

So now I have to start looking at MY disassembly videos to get an idea how much space is under the frunk tub.
I don't think you will find much usable space under the tub as if there were available space they would probably make the tub bigger thus giving the owner more storage. Yes there is space but if you fill it I think you will be changing air flow.

I really think the best bet would be something like the current crop of portable fridges but designed to fit into a Y's frunk (and the other models too) by which I mean configured to fit into a space of the frunk's shape (which is not a rectangular solid) with the exhaust placed to avoid temperature buildup (if that's really a problem). Obviously Tesla should be involved but I don't think they would anticipate enough market to want to invest in this and, for the same reason, I doubt Dometic or ARB or any of the other manufacturers would either.

 

JBee

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Other big problem with the Y is that the system is used as a source of heat as well as cooling so where to tap the liquid line would be a tricky question. This is the model with the Octovalve whose plumbing, or what I can see of it from Sandy Munro's video, looks pretty hairy.



I don't think you will find much usable space under the tub as if there were available space they would probably make the tub bigger thus giving the owner more storage. Yes there is space but if you fill it I think you will be changing air flow.

I really think the best bet would be something like the current crop of portable fridges but designed to fit into a Y's frunk (and the other models too) by which I mean configured to fit into a space of the frunk's shape (which is not a rectangular solid) with the exhaust placed to avoid temperature buildup (if that's really a problem). Obviously Tesla should be involved but I don't think they would anticipate enough market to want to invest in this and, for the same reason, I doubt Dometic or ARB or any of the other manufacturers would either.
Hmm yeah sounds too complicated.

Maybe the easiest way to make a fridge out of the frunk is to put in a aerogel tub liner and make a lid that sits on top of it that houses the refrigeration unit (condenser, evaporator, compressor and contorl unit). Just need a local power connection then and you can remove the lid and liner whenever you don't need it.

Maybe it's also possible to vent out of the lid by compressing the frunk seal with a flat air duct. That way nothing has to be modded at all on the car. A 100l top loading fridge is actually super practical and similar to what I use for our monthly city shopping trips. You can get heaps in when you stack it.

Otherwise I wonder if it might be possible to duct just air from the cabin to the frunk somehow with a temperature controlled fan. Technically the A/C temperature should still work the same, it just might not be very efficient.

There's also the rear underfloor tub in the back that I was looking at. Not sure how big that is but the annoying thing with that is it would be underneath anything you put in the boot. Advantage is it would be cooled with the cabin A/C which would make it easier for the fridge compressor.
 

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I would take one of the small portable fridges and cut its workong parts out, line the tub with insulation, then attach it into the space under the tub, and fashion an insulated lid to fill the gap between the cooled area and the hood.

It's always easier to start a prototype with something that's built, even if the final product is better off custom.

-Crissa
 


JBee

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Putting these two (really the picture from the first) together I think I have your answer: Swamp Cooler!
I'm thinking of making a fridge accessory that replaces the plastic ring mounted on the hood of the MY to covert it into a fridge.

images (21).jpeg


The idea is to have a whole refrigeration system built into the plastic assembly that is mounted on the hood. Once installed it then comes down and seals against the aerogel insulated frunk tub, and can pump heat out of the frunk and out through the gaps around the bonnet. Just need to route power to the 12V system just behind the frunk tub.

If the fridge components need more space they can just lower into the frunk tub and reduce its volume a bit. I'm expecting the frunk to still be around 100l in size, which would be a pretty decent size. It shouldn't be to big an excersise, if the components are packaged compact enough it should actually be possible to makeup different apapter plates to fit all frunks on all Tesla, and even some non-Tesla models.
 
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firsttruck

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I'm thinking of making a fridge accessory that replaces the plastic ring mounted on the hood of the MY to covert it into a fridge.

images (21).jpeg


The idea is to have a whole refrigeration system built into the plastic assembly that is mounted on the hood. Once installed it then comes down and seals against the aerogel insulated frunk tub, and can pump heat out of the frunk and out through the gaps around the bonnet. Just need to route power to the 12V system just behind the frunk tub.

If the fridge components need more space they can just lower into the frunk tub and reduce its volume a bit. I'm expecting the frunk to still be around 100l in size, which would be a pretty decent size. It shouldn't be to big an excersise, if the components are packaged compact enouhh it should actually be possible to makeup different apadter plates to fit all frunks on all Tesla, and even some non-Tesla models.
The refrigeration system might add significant weight to the frunk cover.

The frunk cover hinges and hydraulic strut that holds the frunk cover in the open position may not be strong enough to support the weight of the entire refrigeration system.
 

JBee

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The refrigeration system might add significant weight to the frunk cover.

The frunk cover hinges and hydraulic strut that holds the frunk cover in the open position may not be strong enough to support the weight of the entire refrigeration system.
Yeah I was thinking that too. Maybe bundle it with a electric hood lift or a new set of struts. It will need to be mounted in such a way that it can detach and doesn't change the crumple dynamics of the hood.
 

firsttruck

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The refrigeration system might add significant weight to the frunk cover.
The frunk cover hinges and hydraulic strut that holds the frunk cover in the open position may not be strong enough to support the weight of the entire refrigeration system.
Yeah I was thinking that too. Maybe bundle it with a electric hood lift or a new set of struts. It will need to be mounted in such a way that it can detach and doesn't change the crumple dynamics of the hood.
Too much extra hardware & installation labor.

Your first idea was closer to being in a good direction.
The difference is go ahead and remove the Tesla factory seal but do not mount the refrigeration system to the frunk lid.

Your refrigeration system has it's own lid that covers the frunk tub top and that attaches/mounts into the frunk tub.

Your refrigeration system lid bottom seals to the top of frunk tub and prevents water from entering the frunk tub and the top of your refrigeration system lid has a seal that allows flow of intake air in the front edge and exhaust air on rear edge. This refrigeration system lid also provides some rubber support posts that support the center of the original frunk lid replacing some structural support that the original frunk lid seal to frunk tub surround contact area might have contributed ( for example if someone sat on the frunk lid or heavy snow load on frunk lid).
 
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JBee

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Too much extra hardware & installation labor.

Your first idea was closer to being in a good direction.
The difference is go ahead and remove the Tesla factory seal but do not mount the refrigeration system to the frunk lid.

Your refrigeration system has it's own lid that covers the frunk tub top and that attaches/mounts into the frunk tub.

Your refrigeration system lid bottom seals to the top of frunk tub and prevents water from entering the frunk tub and the top of your refrigeration system lid has a seal that allows flow of intake air in the front edge and exhaust air on rear edge. This refrigeration system lid also provides some rubber support posts that support the center of the original frunk lid (replacing some structural support that the original frunk lod seal to frunk tub surround contact area might have contributed ( for example if someone sat on the frunk lid or heavy snow load on frunk lid).
Yeah probably true. Just a frunk lid that has air ducting through the seals would be easier. It would still weigh about 4-5kg, but could just flip up and stand by itself. Could have a frame that attaches via a hinge to the tub insulation insert. But I also like the auto frunk hood...theres a few decent priced ones around $400, but I suppose that's extra cost that not everyone wants.

The whole HVAC assembly is just behind the frunk tub, a extra evaporator on there would be pretty cost effective in comparison. What would someone pay for a custom Tesla fridge accessory like that $500-700? A 100l fridge is pretty big for that type of vehicle.
 


charliemagpie

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Portable duel fridges around AU$1000 - $1500 for 75l-95l

Custom-made for a Tesla should be at least that.
 

JBee

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Portable duel fridges around AU$1000 - $1500 for 75l-95l

Custom-made for a Tesla should be at least that.
Yeah thats what I was thinking. US is a bit cheaper plus exchange rate. I got myself a Kings 95l one a few years ago, first one was a dud which I swapped under warranty, second one won't quit. Dual zone is excellent and sips power. Just a bit noisy for camper use.

Another thing I'm interested in is a decent 240V inverter setup on the MY, but I don't really like running 2-3kW off the 12V setup. V2X would be nice. CT just makes everything easier.
 

JBee

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Other big problem with the Y is that the system is used as a source of heat as well as cooling so where to tap the liquid line would be a tricky question. This is the model with the Octovalve whose plumbing, or what I can see of it from Sandy Munro's video, looks pretty hairy.



I don't think you will find much usable space under the tub as if there were available space they would probably make the tub bigger thus giving the owner more storage. Yes there is space but if you fill it I think you will be changing air flow.

I really think the best bet would be something like the current crop of portable fridges but designed to fit into a Y's frunk (and the other models too) by which I mean configured to fit into a space of the frunk's shape (which is not a rectangular solid) with the exhaust placed to avoid temperature buildup (if that's really a problem). Obviously Tesla should be involved but I don't think they would anticipate enough market to want to invest in this and, for the same reason, I doubt Dometic or ARB or any of the other manufacturers would either.
I've been looking around for more information on the cooling system on the MY. This is a screengrab from the Model MY teardown that gives a bit of insight, this diagram is from the 2018 M3 though not the MY to compare:

Tesla M3 2018 Cooling setup.png


On the MY though they have the Octovalve setup and only one single glycol radiator, the A/C condenser is a liquid glycol to refrigerant heat exchanger that is is cooled from the glycol radiator. That HEX as well as the chiller HEX sit on the octovalve assembly itself.

The Octovalve setup looks like this according to Untangleclub:

model-y-heat-pump-components-1024x592.jpg


So from the above it seems pretty clear that the glycol and refrigerant circuits are separated in such a way to allow for the most common forms of heat transfer depending on environment and equipment conditions. From what I can tell, because there is a cabin condenser and a cabin evaporator, there is actually a chance to use the cabin evaporator side and use the liquid refrigerant to run a HEX in the Frunk fridge. This is because the heat pump appears not to be reverse cycle which means there is always a cold side for the fridge. It should also not matter if the octovalve changes modes.

Because of this It's maybe also possible to take the glycol output of the chiller instead of the refrigerant line, meaning a much simpler thermostat controlled valve and a small liquid to air HEX could be used in the fridge, with a fan and maybe might need a glycol pump, depending on flow resistance on the rest of the system compared to the fridge HEX. The downside is there is no guarantee the chiller is actually being cooled, but this might be overcome by commanding the A/C to be on, which in turn it would likely be when it is also necessary to cool the fridge. If it's cold enough outside you wouldn't need to cool the fridge either.

There's enough space to mount either version on the outside of the frunk box next to the octovalve assembly so it won't change the usability of the frunk tub. It might also be possible to insulate the outside of the frunk tub as well, and have a insulated liner on the hood itself meaning that there will be no difference to the frunk.

This is how MY Octovalve is described to work:



part 2 (which is just heating modes):



and part 3:


It's interesting that it uses both the condenser and evaporator to dehumidify the air (like in a ICE) and that they operate at COP 1 when the temperature goes under -10C, which is not really that low, but I suppose where they operate at with this setup.

If the same system is used in the CT, I'm hopeful the with a few upgrades they don't only just have the bed HVAC as announced already, but also refrigeration of the frunk as well.
 
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ajdelange

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...they operate at COP 1 when the temperature goes under -10C, which is not really that low, but I suppose where they operate at with this setup.
While the theoretical COP at -10°C is about 9.8 in actual systems we can build economically closer to 1 is to be expected.

I just noticed, with great interest, that the heat absorbed by the radiator does NOT bring about a phase transition as it does in a conventional heat pump but simply warms water (glycol) which has been chilled by the chiller. I'd love to see the PH diagram for that!

there is actually a chance to use the cabin evaporator side and use the liquid refrigerant to run a HEX in the Frunk fridge. This is because the heat pump appears not to be reverse cycle which means there is always a cold side for the fridge. It should also not matter if the octovalve changes modes.
In a conventional (home heat pump) there are two heat exchangers and while such systems have "reversing valves" what they reverse is the order in which they are connected (not the direction of refrigerant flow through them). In other words they rearrange the HX positions on the refrigerant loop. The Octovalve system really does the same thing but now there are 4 HX on the refrigerant loop and 3 on the glycol side. Both types of systems use a compressor out of which comes hot gas whether the system is in a heating or cooling mode or, as with some Octovalve modes, both simultaneously. You can always (either system in any mode), tap the compressor exhaust and run it though a separate condenser and, as long as you can extract enough heat to obtain the phase change, obtain a separate source of liquid refrigerant. This can be run through a separate expansion valve and coil to refrigerate something.

Fascinating. Thanks for posting those. I certainly don't have the temerity to tap into a system that complex. Elon was quite right when he said it one of the most elegant bits of engineering he has ever seen.

 

 
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