Laptop Temps and Humans at Altitude (HighLANder)

[KeltonDSMer]

Okay so after yesterday's WAN show it sounds like the HighLANder is very much a private event. I was stoked at the possibility of a public LAN where I could meet some of the best YT techies, but this actually seems way cooler. A badass crew hiking up a mountain with sweet Laptops to play games in the clouds, yell yeah!

 

This got me thinking. First, I hope you guys are able to bring some oxygen tanks along. Altitude sickness is real and it sucks. I know Linus and Luke are young and healthy, but tech enthusiests as a whole are not known for their stunning cardio. The air up there is only 2/3 the pressure compared to sea level. Trees are unable to grow at that altitude. Logan better not crack open a big stout ale or whatever up there, he will get wrecked!

 

So human body performance will take a hit, but what about the laptops themselves? We all know thermals are a huge limiting factor when it comes to performance capabilities of laptops. The cooling systems are always maxed out and now here is a situation that is pure torture. If the air is only 2/3 the density compared to sea level, wouldn't that in turn mean that the cooling capacity of the laptops are also reduced by the same fraction (of course assumnig equal ambient temps/humidity).

 

I am really curious to see if there will be an issue with heat dissipation. Anyone have some thoughts on this idea?

[Freaky_spider]

interesting question

 

Seeing that the fan will probably spin faster due to less air resistance, it will still probably suck in less air, but i dont think it will really impact temps too much

[cacra]

less air=less thermal conduction

[airdeano]

also at higher altitude, the air is thinner, but also the temperatures are lower.

so the ambient temp the laptop is in should result in lower overall idle and under

load temperatures.

[KeltonDSMer]

If the fans are voltage regulated, I could see them spinning faster due to the reduced resitance. However, if they are PWM controlled, wouldn't the RPM ranges remain constant (meaning flow volume is the same at altitude/sea level)?

 

 

also at higher altitude, the air is thinner, but also the temperatures are lower.

so the ambient temp the laptop is in should result in lower overall idle and under

load temperatures.

 

If the air is only 2/3 the density compared to sea level, wouldn't that in turn mean that the cooling capacity of the laptops are also reduced by the same fraction (of course assumnig equal ambient temps/humidity).

 

The temp difference is certainly a huge deal here, but this time of year the mountain top should actually have pretty similar temps to a climate controlled room (highs 20-25C). This factor is one of the reasons I brought up the discussion, if they fire up the machines by early afternoon the ambient temp actually could be close enough to "normal" rooms to make a worthwhile comparison.
 

[chicksoup]

Okay so after yesterday's WAN show it sounds like the HighLANder is very much a private event. I was stoked at the possibility of a public LAN where I could meet some of the best YT techies, but this actually seems way cooler. A badass crew hiking up a mountain with sweet Laptops to play games in the clouds, yell yeah!

 

This got me thinking. First, I hope you guys are able to bring some oxygen tanks along. Altitude sickness is real and it sucks. I know Linus and Luke are young and healthy, but tech enthusiests as a whole are not known for their stunning cardio. The air up there is only 2/3 the pressure compared to sea level. Trees are unable to grow at that altitude. Logan better not crack open a big stout ale or whatever up there, he will get wrecked!

 

So human body performance will take a hit, but what about the laptops themselves? We all know thermals are a huge limiting factor when it comes to performance capabilities of laptops. The cooling systems are always maxed out and now here is a situation that is pure torture. If the air is only 2/3 the density compared to sea level, wouldn't that in turn mean that the cooling capacity of the laptops are also reduced by the same fraction (of course assumnig equal ambient temps/humidity).

 

I am really curious to see if there will be an issue with heat dissipation. Anyone have some thoughts on this idea?

dude...I'm sorry to tell you that you are wrong. People aren't that sensitive to altitude and they're not going that high up. I live in Austria and go hiking and spend weekends in the mountains and I can only tell you that the air out on the mountains is much cleaner than in the city, but you're not going to get sick and have to be under medical supervision.

[Recon-UK]

I am with @airdeano though my laptop is hot at any altitude, had to ghetto rig a 120mm H100 corsair fan to it to stop it BSOD and thermal throttling.

[Recon-UK]

My time in the Army and doing exercises over brecon carrying around 60KG, the thinner air made no difference, and those hills go way up into the clouds in Wales.

 

[cacra]

My time in the Army and doing exercises over brecon carrying around 60KG, the thinner air made no difference, and those hills go way up into the clouds in Wales.

 

 

It did make a difference, you might not of noticed it but it was there.

[Recon-UK]

It did make a difference, you might not of noticed it but it was there.

It is feasible that it made a difference, but under such conditions and physical excursion, one may never truly realize there was a difference.

 

I can only relay what i experienced.

[Hyrikan]

It is feasible that it made a difference, but under such conditions and physical excursion, one may never truly realize there was a difference.

 

I can only relay what i experienced.

 

Come on in wales. Were talking about 1500m max?! They go up to Mt. Elbert which is 4,4km high. Up there the thinner air actually makes a difference, albeit not nearly enough to require oxygen or anything crazy like that. If you are skiing on a really high mountain you can already feel the difference, and my highest skiing location was only near 3000m.

[KeltonDSMer]

dude...I'm sorry to tell you that you are wrong. People aren't that sensitive to altitude and they're not going that high up. I live in Austria and go hiking and spend weekends in the mountains and I can only tell you that the air out on the mountains is much cleaner than in the city, but you're not going to get sick and have to be under medical supervision.

 

Dude, the people that have problems are not the people that live at altitude! I go up into the mountains all the time and don't get "sick", but people that aren't used to it can feel crummy really quickly. I go up over 1000 meters of vertical altitude in just 40 mins (from 5000-8500ft ) when I go play poker in Blackhawk and am just fine, but people that live at sea level their whole life are affected entirely differently. These guys aren't a bunch of pansies lol, but seriously an O2 tank would not be a silly thing to bring along!

 

I guess I was thinking of Elrich for the most part, didn't he recently have some health problems?

 

Anyway, the "human performance" thing was just kind of a mental segway of me being curious about heat exchanger performance as the fluid that the energy is moving towards decreses in density. I am simply courious to see if they have temp problems, not whether or not someone is going to croak walking up a big hill.

 

You guys are awesome

[Recon-UK]

Come on in wales. Were talking about 1500m max?! They go up to Mt. Elbert which is 4,4km high. Up there the thinner air actually makes a difference, albeit not nearly enough to require oxygen or anything crazy like that. If you are skiing on a really high mountain you can already feel the difference, and my highest skiing location was only near 3000m.

Only relaying my experience.

[Recon-UK]

Dude, the people that have problems are not the people that live at altitude! I go up into the mountains all the time and don't get "sick", but people that aren't used to it can feel crummy really quickly. I go up over 1000 meters of vertical altitude in just 40 mins (from 5000-8500ft ) when I go play poker in Blackhawk and am just fine, but people that live at sea level their whole life are affected entirely differently. These guys aren't a bunch of pansies lol, but seriously an O2 tank would not be a silly thing to bring along!

 

I guess I was thinking of Elrich for the most part, didn't he recently have some health problems?

 

Anyway, the "human performance" thing was just kind of a mental segway of me being curious about heat exchanger performance as the fluid that the energy is moving towards decreses in density. I am simply courious to see if they have temp problems, not whether or not someone is going to croak walking up a big hill.

 

You guys are awesome

Elric is diabetic.

 

You mean Elric of mobo.org right?

[Hyrikan]

Only relaying my experience.

 

Hard to relay on anything other, isn't it? But I have to assume that you also were quite trained when doing exercises like that which makes a big difference as well. As I said it's ridiculous to bring an oxygen tank up to 4400m  - no healthy human will need it, especially since they aren't lifting weights or similar up there.

[Recon-UK]

Hard to relay on anything other, isn't it? But I have to assume that you also were quite trained when doing exercises like that which makes a big difference as well. As I said it's ridiculous to bring an oxygen tank up to 4400m  - no healthy human will need it, especially since they aren't lifting weights or similar up there.

Very true

[juretrn]

My time in the Army and doing exercises over brecon carrying around 60KG, the thinner air made no difference, and those hills go way up into the clouds in Wales.

 

I'm sorry, but you Brits have no Idea what altitude means. The tallest hill in Wales is 1000 m and a bit, right? The air is barely any thinner at that altitude. I myself live on 600 m above sea level...

 

@Freaky_spider No, fans (EDIT: DO NOT spin)  faster with lower air density, since they depend on the speed of the phases changing in the electric motor. However, if the medium is too dense (like water), they will slow down.

[KeltonDSMer]

Elric is diabetic.

 

You mean Elric of mobo.org right?

 Oh no "h", yeah I was thinking of the guy from TOT. Shoot, my brother is a type I diabetic (auto immune...his own tcells attack his pancreas).

 

 

Forget about the O2 guys sheesh, I understand most people are fine at that altitude. I just know I would rather breathe some 100% O2 for five minutes as opposed to feeling like garbage for 24 hours if I was sensitive to thin air, that's all. It's okay, everything is going to be okay!

 

You guys are still awesome.

 

Edit: Mispelled breathe "breath"

[KeltonDSMer]

No, fans spin faster with lower air density, since they depend on the speed of the phases changing in the electric motor. However, if the medium is too dense (like water), they will slow down.

 

Oooo, can you help me understand this? I can understand a voltage regulated fan being able to spin faster at altitude for any given voltage, but how does this work with PWM control? Does PWM duty cycle not directly relate to fan RPM? Since the singal square wave is a constant frequency (like 24kHz or something), wouldn't 100% duty cycle be the same fan RPM regardless of resistance?

[juretrn]

A voltage regulated fan has a limit to how quick it spins. It cannot spin any faster than maximum speed, since that is not how a DC motor works. Even in vacuum.

 

Yes, RPM is directly correlated to PWM duty cycle. However, if the resistance is too great, the magnetic fields in the stator trying to pull the rotor in the desired direction might be unable to do so and the rotor might actually lag behind. A lot of the delivered energy, that would otherwise be directly used to spin the fan is now used to break the viscosity of a gas or liquid.

 

If you don't believe me, place a PWM fan in water, or, if you want to be really evil, in honey (or shampoo. or whatever dense liquid).

[KeltonDSMer]

A voltage regulated fan has a limit to how quick it spins. It cannot spin any faster than maximum speed, since that is not how a DC motor works. Even in vacuum.

 

Yes, RPM is directly correlated to PWM duty cycle. However, if the resistance is too great, the magnetic fields in the stator trying to pull the rotor in the desired direction might be unable to do so and the rotor might actually lag behind. A lot of the delivered energy, that would otherwise be directly used to spin the fan is now used to break the viscosity of a gas or liquid.

 

If you don't believe me, place a PWM fan in water, or, if you want to be really evil, in honey (or shampoo. or whatever dense liquid).

 

Why would I not believe you? That makes perfect sense that there is a threshold where a PWM fan will slow from it's max RPM if the fluid is too dense (oil PC pr what not). What is bothering me though is what happens on the other end of the spectrum, lower fluid density.

 

Wait a sec, I see now that a PWM fan at 100% duty cycle behaves just like a standard 3pin fan with 12volts to it (square wave is not a wave at this point, just solid 12v). For some reason I was under the impression that the motors were completely different.

 

I think I have it figured out, please tell me if this is wrong:

 

3pin PC fans are controlled by voltage, but the voltage is constant (5v,7v,12v). The PWM fans are always 12v, but can turn on and off really fast. This makes sense why PWM is a superior method of controlling PC fans, especially for low speeds. If a DC motor is designed for 12v, it might not even start at like 5v. Using PWM, the motor is able to opperate at the intended voltage, but it just isn't "on" all the time to bring the speeds down.

 

So, the laptops at the top of the mountain should be able to move a higher volume of air over the heat sinks compared to sea level (fans should spin faster at 100%). I still bet that the ratio of extra air volume does not quite make up for the decrease in density. My initial thoughts on this were assuming the laptop fans would spin at the same max speed regardless of air density, I now see this is unlikely to be the case.

 

Whatever is going on on the world of fluids, fans, and heat transfer, I still am left wondering how those fantastic pieces of equipment will fare up in the Rockies! Thanks everyone for chiming in, I really appreciate the entertaining and informative posts!

[juretrn]

Why would I not believe you? That makes perfect sense that there is a threshold where a PWM fan will slow from it's max RPM if the fluid is too dense (oil PC pr what not). What is bothering me though is what happens on the other end of the spectrum, lower fluid density.

 

 

I think I have it figured out, please tell me if this is wrong:

 

 

Whatever is going on on the world of fluids, fans, and heat transfer, I still am left wondering how those fantastic pieces of equipment will fare up in the Rockies! Thanks everyone for chiming in, I really appreciate the entertaining and informative posts!

Sorry. I have messed up my original post. Check it, I edited. I meant to say max speed, even in vacuum, doesn't go faster than, for example, 3000 rpm, if the motor is rated for 3000 rpm. The motor cannot go faster than the magnetic fields controlling it.

 

 

Wait a sec, I see now that a PWM fan at 100% duty cycle behaves just like a standard 3pin fan with 12volts to it (square wave is not a wave at this point, just solid 12v). For some reason I was under the impression that the motors were completely different

Basically, it's the same. A PWM motor only gets an additional line, which, if I am not mistaken, controls the opening of a BJT on the fan, which lets current through at the times when the PWM signal is at 1.

 

 

 

3pin PC fans are controlled by voltage, but the voltage is constant (5v,7v,12v). The PWM fans are always 12v, but can turn on and off really fast. This makes sense why PWM is a superior method of controlling PC fans, especially for low speeds. If a DC motor is designed for 12v, it might not even start at like 5v. Using PWM, the motor is able to opperate at the intended voltage, but it just isn't "on" all the time to bring the speeds down.

Correct. Though you can also undervolt a PWM fan if you like. 

 

 

So, the laptops at the top of the mountain should be able to move a higher volume of air over the heat sinks compared to sea level (fans should spin faster at 100%). I still bet that the ratio of extra air volume does not quite make up for the decrease in density. My initial thoughts on this were assuming the laptop fans would spin at the same max speed regardless of air density, I now see this is unlikely to be the case.

We might have had a bit of a misunderstanding . Your initial thoughts were correct. 

Cooling will be worse IMO, fans will be spinning at the same speeds, but with less air. 

[KeltonDSMer]

 

 

 

I am now all cleared up with the PWM control, thanks a bunch. I agree cooling will suffer, but I do think that the fan(s) will spin just a bit faster (a little more volume). I had originally thought the fan speed limitations were for a non-existent reason other than how i see it now. I was confused how PWM fans work but for this discussion I will treat them like any other DC motor with a load on it.

 

Looking at the torque curve of a DC motor (compared to shaft speed), it is a straight line (-slope). There is certainly a finite physical/electrical limit as far as shaft speed with no load (torque=0). They have peak force at 0 rpm, but fans "max out" somewhere in between, a sweet spot if you will. A 12v fan's motor puts out the same force as the air that is resisting the rotation, or it must be speeding up or slowing down. Now all of a sudden make the air 2/3 the mass/volume and the same 12v fan is putting out more force than the air resistance so it accelerates. As the RPM increases, so does the air resistance, yet the motor torque decreases. A new equilibrium of motor output=air resistance is realized quickly, but still at a higher RPM than at sea level. Note, the friction in the bearing also increases with speed, so the fan in turn has even less usable output as speeds increase. All of these changes are not happening at the total extremes of the RPM range (0RPM/max torque and no load/maxRPM) for the motor.

 

Does that babble make any sense? Basically I do think fans will spin a wee bit faster, but that it has little impact on overall cooling capacity of the laptops compared to the loss in air density.

[juretrn]

Yeah the difference might be 1-2 RPM IMO, hardly game-changing.

[Yoinkerman]

I've partied at 7500ft a few times, and electronics work fine.

People don't, however, and being weak and oxygen starved and super easy to get drunk and taking much longer to recover is real.