Opinions, if you'd be so kind. (getting long and nerdy)

[SpyderTracks]

I do believe there's a very small amount of liquid within the heatpipes, although not universally I don't think:

Laptops 101: Understanding what goes into designing an efficient laptop cooling solution

Designing and implementing an efficient thermal system in a laptop requires a lot of R&D and proper selection of each individual component in the system to ensure all components perform to their full potential. That’s why MSI's flagship GT76 laptop can ru

www.msi.com

 

[SpyderTracks]

I saw this video by GamersNexus on heatpipes at the factory, it's well worth a look, quite interesting the different manufacturing standards:

 

[Scott]

Makes perfect sense. It's weight saving after all (I knew there had to be a trade off somewhere).

Liquid is heavy, not as heavy as copper but not as light as air.
Liquid exchanges heat well, not as well as copper but miles better than air.

To get to a happy medium, they use a small amount of liquid as an ever exchanging vapour. Not as efficient as water or copper, but clearly better than air.

Quite clever actually....... water is still better though

 

[keithbeaks]

Wow. I'll need to read all of this more than once twice to understand it fully.

Thanks for taking the time to post so much!! Its nice to know what is actually happening inside the case, when my PC arrives!

 

[g85]

a'ight, now we're getting nerdy, i like it!

really love your detailed response @Scott
no apology necessary @Grinty

i hate to be that guy, but i did in the initial post state my prejudicial views on water cooling, and gave you my reasons why, and said i'm stubbornly not changing my mind, and yet we've somehow managed to turn this entire thread in to a watercooling discussion.

I'm perhaps not as daft about thermodynamics as you may presume scott. I don't have a degree in it, but i do have a-level physics, i was a chef for half a decade in some top restaurants before i knackered my back, and science and temperature go hand in hand in the kitchen. oh, so you can cook a steak? fire hot. big whoop.

i know all about the specific heat of water, it's capabilities in terms of thermal transfer, and i would often quote Q=m cp delta T at chefs who had no idea what i was on about. (that is to say, the amount of energy is directly related to the mass times specific heat of a given substance times the change in temperature - useful not only in the kitchen, but general daily life).

This is a long and round about way of saying I already know why water cooling is technically better. still, do i want water anywhere near my system? no. i'm not crazy overclocking, and i'm looking at the low-mid tier CPUs rather than the mid-high.

air cooling will be fine, scott, as you yourself have stated. it's not going to be the best in your opinion, but it will be the best in mine, and that's kind of the point really isn't it?

@SpyderTracks thanks for that gamer's nexus vid, i need something to help me drift off tonight! i love steve, but god damn does he drone in that scripted voice all over those benchmark results for 45 minutes at a time.

g85

p.s. does this make me a water-racist?

 

[SpyderTracks]

thanks for that gamer's nexus vid, i need something to help me drift off tonight! i love steve, but god damn does he drone in that scripted voice all over those benchmark results for 45 minutes at a time.

First few times I watched him I couldn’t get past the monotonous tones, but the more I listened, the more I realised just how clever he is. I now watch their reviews religiously, meticulous testing methodologies, although I usually skip to freeze frames for the results.

 

[Grinty]

This could be a teachable moment though, so if you find anything on it... please post up as I would be genuinely interested to know

I'm not the best person to explain this but I'll have a go.

Heat conducts into the liquid at the hot end of the pipe and turns it into vapour. The vapour travels to the cold end, where it condenses and runs down the inside of the pipe back to the hot end. The vapour isn't simply diffusing - there's a pressure gradient inside the pipe because you're "producing" gas at the hot end and "consuming" it at the cold end. Most heat-pipes also have some kind of wicking structure on their inner surface so they're not entirely relying on gravity to return the working fluid to the hot end, but they are generally much more efficient when the hot end is at the "bottom".

All of this basically adds up to much better energy transfer over a temperature gradient than you'd expect from the properties of the working fluid itself - it could be a near-perfect insulator in both liquid and gas form and still work. You could also move a huge amount of heat across a near-zero temperature gradient as long as it was centred on the boiling point of the fluid.

You could even think of a heat pipe as a really cleverly designed AIO cooler, where you don't need an active pump because it's using the energy from the hot thing to push the fluid around the system.

EDIT: Just realised I missed the crucial bit of information! A liquid at its boiling point contains less energy than the corresponding gas at the same temperature, so by boiling the liquid at the hot end it takes heat energy from the CPU (without necessarily changing temperature), and when it condenses that energy is transferred to the radiator.

 

[Grinty]

Just had a look at the Wikipedia page for "Heat pipe", where I found this interesting tid-bit:

"The advantage of heat pipes over many other heat-dissipation mechanisms is their great efficiency in transferring heat. A pipe one inch in diameter and two feet long can transfer 3.7 kW (12.500 BTU per hour) at 1,800 °F (980 °C) with only 18 °F (10 °C) drop from end to end. Some heat pipes have demonstrated a heat flux of more than 23 kW/cm², about four times the heat flux through the surface of the sun."

 

[Scott]

I'm not the best person to explain this but I'll have a go.

Heat conducts into the liquid at the hot end of the pipe and turns it into vapour. The vapour travels to the cold end, where it condenses and runs down the inside of the pipe back to the hot end. The vapour isn't simply diffusing - there's a pressure gradient inside the pipe because you're "producing" gas at the hot end and "consuming" it at the cold end. Most heat-pipes also have some kind of wicking structure on their inner surface so they're not entirely relying on gravity to return the working fluid to the hot end, but they are generally much more efficient when the hot end is at the "bottom".

All of this basically adds up to much better energy transfer over a temperature gradient than you'd expect from the properties of the working fluid itself - it could be a near-perfect insulator in both liquid and gas form and still work. You could also move a huge amount of heat across a near-zero temperature gradient as long as it was centred on the boiling point of the fluid.

You could even think of a heat pipe as a really cleverly designed AIO cooler, where you don't need an active pump because it's using the energy from the hot thing to push the fluid around the system.

It makes perfect sense. It's definitely not better than solid copper but that would cost an absolute fortune. Water, again, would be significantly better, but not while stagnant. Air is awful.... as are most (probably all) gasses.

It's actually pretty clever, it creates a "water" flow through pipes without the pump.

It's definitely not as efficient as moving water, or as efficient as solid copper would be, but as a trade off it's a fantastic solution. makes perfect sense so thanks for highlighting it

 

[Grinty]

It's definitely not better than solid copper

Also from Wikipedia: "The effective thermal conductivity varies with heat pipe length, and can approach 100 kW/(m⋅K) for long heat pipes, in comparison with approximately 0.4 kW/(m⋅K) for copper."

 

[g85]

this thread is maturing like a fine wine

 

[Scott]

This is a long and round about way of saying I already know why water cooling is technically better. still, do i want water anywhere near my system? no. i'm not crazy overclocking, and i'm looking at the low-mid tier CPUs rather than the mid-high.

air cooling will be fine, scott, as you yourself have stated. it's not going to be the best in your opinion, but it will be the best in mine, and that's kind of the point really isn't it?

You think of yourself as being a stickler........ "better" has been my sticking point all along. The AIO is better, there's no getting away from it. The air cooler is more than suitable and will do the job fine.... I've never argued this point. The semantics of which is best is not up for debate with me.... even given your uses and every scenario you can give, the AIO will be better...... it's just not necessary to be satisfactory to your requirements. I am absolutely fine with your decision, the reasoning you put forward was always a point of contention for me but the end result is a system that will function admirably so there's no qualms there

 

[g85]

still going on, eh Scott?

"the AIO will be better..." yeah, for you.

 

[Scott]

Also from Wikipedia: "The effective thermal conductivity varies with heat pipe length, and can approach 100 kW/(m⋅K) for long heat pipes, in comparison with approximately 0.4 kW/(m⋅K) for copper."

That's a misinterpretation of what I mean....

A solid pipe would take longer to heat soak than a vapour filled copper pipe. If you can dissipate the heat effectively enough at the end of the copper pipe, it would be far harder to saturate the cooling solution.

Unfortunately.... once it's saturated, there's no way to lower the temp quickly so with a CPU it makes complete sense to use the vapour filled chambers as simply throttling the speed will immediately lower the temperature. With a solid lump of copper the reaction time would be far slower (as the slow dissipation rate will match the slow saturation rate).

Every day is a school day

 

[keithbeaks]

Misinterpretation/misrepresentation...

 

[Grinty]

That's a misinterpretation of what I mean....

Sorry about that. I'm still not quite sure what you meant in that case.

From my perspective, everything between the CPU die and the radiator is just there to transfer heat as effectively as possible, measured in Watts per Kelvin (or whatever units you prefer). In that sense heat pipes are "better" than solid copper or any other bulk material by an enormous margin. They could be better than water cooling but I haven't been able to find the information that would let me make a comparison.

I don't quite follow what you mean by heat soak or saturating the cooling solution but the impression I get is that they're related to the radiator taking some time to change temperature and the rate you can dump heat off the radiator, both of which have nothing to do with how the heat got to the radiator in the first place. If I've misunderstood then please explain, as I've clearly got some learning to do today too!

 

[g85]

see? we're all learning when we open our minds to the possibilities.

@Grinty i believe what he means directly relates to my Q=m cp delta T. the higher the mass, the slower the change in temperature.

 

[Grinty]

@Grinty i believe what he means directly relates to my Q=m cp delta T. the higher the mass, the slower the change in temperature.

Ah, so that's how well something stores heat, in which case yes, heat pipes are junk because there's barely any mass to them! XD

 

[g85]

@Grinty yeah, but there's a reason old french chef's pans are copper! speed!

(specific heat and delta T are two separate variables)

 

[Scott]

Apparently my work here is done

Well, almost...

It doesn't just come down to storing heat, but dissipating heat. The 100kW/m is a fantastic feat but what happens when it gets to the end of the pipe, or the cross section.... it heats up rapidly. The amount of heat it can store is limited by the mass of the storage and the dissipation of the end.

To think about it simplistically, if the CPU put out 100kW, this heat would be very quickly transferred throughout the entire body... vapour magic... unfortunately, this would instantly heat-soak the mass as it cannot dissipate this heat quickly enough to the external body (the outside air). we all know that heat exchange to air is really poor. This is the reason for the absolutely huge fins on the end of the copper pipes (heat sink).

Now, if the pipes were solid, they would dissipate the heat at a slower rate 0.4kw/m, but it would take a LOT more time for the saturation of the material to actually reach the temperature of the CPU.

If you think about it, if you go with the Wikipedia page, it's effectively saying that the CPU could output 100kw and the cooling solution could handle it with ease (well, it's not... but it could be misinterpreted as such). It can't, it'll get it to the heatsink very quickly.... but after that we are limited by the copper/air heat exchange. The cooling solution will soak quicker due to how efficient it is at sharing the heat, but how poor it is at exchanging it. A solid unit would take much longer to soak, but be less reactive to change.

Not sure if that makes sense..... it does in my head but it's late haha.