The Whiteboard

12:26 AM

@Weston.h @GlenH7 needs to verify this before I'll buy in; only a real engineer can affectively approve of such a product, the rest of us are either lucky or suckers

user41796

2:01 AM

@JimmyHoffa reasonably legit from a tech point of view; no idea if they're looking at a reasonable price point. Essentially, they're using that same blue goo that you see in ice packs for coolers. Except they're wrapping it in fashionable stainless steel instead of plastic. Having had one of those plastic ice pack coolers break on me, I can definitely see the value of stainless steel.

user41796

I didn't try to tear apart their numbers regarding "phase change" and temperatures. Some of that is definitely marketing hyperbole. Water goes through a "phase change" too when it transforms from liquid to ice.

user41796

@Chrislast Qt is pretty well standard with C++ at this point. C# == .NET framework and you have a number of choices like WPF, ASP's flavor of the week, and whatever else. If you want hard, stick with Qt and C++. The combination is not as well abstracted as .NET options are.

Jimmy Hoffa

@GlenH7 So it's like those ice cube shaped plastic freezer pouches in your drink except it doesn't leave the plastic flavor behind, and stainless steel is not really the ideal material for conduction I would think... but cheaper than brass or copper I guess

user20683

2:16 AM

@JimmyHoffa won't corrode like brass or copper

Jimmy Hoffa

Ah good point

user20683

remember, beer and wine are acidic

user55340

4:27 AM

@GlenH7 heat locked up in phase change is quite real.

user55340

(This is from a "I know of it" chemistry/physics background).

user55340

The 'heat of fusion' is the amount of energy you need to pump into something for it to change from solid to liquid.

user55340

For plain old water, this is 79.7 cal/gram. Or another way of looking at it, to take it from 0 C ice to 0 C water is the same amount of energy to take the same amount of water from 0 C water to 79.7 C water. Its quite a bit.

user55340

Enthalpy of fusion

The enthalpy of fusion or heat of fusion is the change in enthalpy resulting from heating a given quantity of a substance to change its state from a solid to a liquid. The temperature at which this occurs is the melting point. The 'enthalpy' of fusion is a latent heat, because during melting the introduction of heat cannot be observed as a temperature change, as the temperature remains constant during the process. The latent heat of fusion is the enthalpy change of any amount of substance when it melts. When the heat of fusion is referenced to a unit of mass, it is usually called the spe...

user55340

Water is a quite good option, the problem with it in this application would be that freezing it would make it expand. Thats a bad thing to have in your freezer.

user55340

4:32 AM

►

user55340

The "blue goo" in freezer pouches is often propylene glycol, and digging around thats 914 kJ/kg which is 218 cal/g -- you can see why its preferred over regular ice.

user55340

But also a useful melting point (that propylene glycol has a melting point of -59 C, so its not undergoing a phase change when warming things)

user55340

For comparison, the heat of vaporization of water is 539 cal/gram -- 1 gram of steam at 100 C has much more energy in it than 1 gram of water at 100 C. This is why steam burns can be very, very bad.

user41796

12:37 PM

@JimmyHoffa Metals are generally really good at conducting heat. Have a look here: engineeringtoolbox.com/thermal-conductivity-d_429.html. Stainless has the advantage of being somewhat trendy and will best resist fouling from whatever it's been put in. Plastics and stones pick up a flavor from whatever they've been in (as you've found).

user41796

@MichaelT I'm not arguing that point on the physics of it. My comment was more a bit of disgust with the marketing hyperbole. "Oooooh, looky here, we did MAGIC!!!!" But I accept that it's kickstarter and a degree of marketing is required in order to have a successful campaign.

user41796

The trick with picking a material in this case is picking something that is a) really good at heat extraction during phase change but that is b) not too terribly toxic in case some is accidentally ingested.

Ampt

@GlenH7 or just being too large to ingest, as they seem to have designed them to be

user41796

I am kind of curious to know how they're machining those shapes so they can inject whatever they're using but also provide a seamless look to them.

user41796

@Ampt - the risk is more from leaks. Plastics will almost always fail at some point. Metals can be dented and start to leak. Stainless shouldn't rust with normal usage and some care, but that's not foolproof.

Ampt

12:47 PM

good question as to how they're made....

user55340

2:04 PM

I've never looked at it before... I do have a rather neat gravitar identicon.

user55340

MichaelT, Eau Claire, WI

101 1

Ampt

what are those statments called in C where you have a check followed by two conditions that will chose based on the check? It's usually of the format `isTrue ? trueStatement : falseStatement

user55340

ternary

user55340

Or rather, its the ternary conditional... but there aren't that many other (I can't think of any) ternary operators.

user55340

Ternary operation

In mathematics, a ternary operation is an n-ary operation with n = 3. A ternary operation on a set A takes any given three elements of A and combines them to form a single element of A. An example of a ternary operation is the product in a heap. In computer science, a ternary operator (sometimes incorrectly called a tertiary operator) is an operator that takes three arguments. The arguments and result can be of different types. Many programming languages that use C-like syntax feature a ternary operator, ?:, which defines a conditional expression. Since this operator is often the only ex...

Ampt

2:12 PM

ternary operation

user55340

?:

In computer programming, ?: is a ternary operator that is part of the syntax for a basic conditional expression in several programming languages. It is commonly referred to as the conditional operator, inline if (iif), or ternary if. It originally comes from CPL, in which equivalent syntax for e1 ? e2 : e3 was e1 → e2, e3. Although many ternary operators are possible, the conditional operator is so common, and other ternary operators so rare, that the conditional operator is commonly (albeit incorrectly) referred to as the ternary operator. Conditional assignment ?: is used as foll...

Ampt

thank you!

are they frowned upon at all?

user55340

At one point, I changes the ?: all the way back to B in language definitions.

user55340

it depends on the context they are used in.

Ampt

Came across them in a code review

user55340

2:13 PM

return a?b:c; is likely good.

Ampt

and wasn't sure if I should say anything about them

yeah, thats the usage

user55340

I've also seen (as an exercise in obscufication) (a,b?c,d,e?f:h:g,i) -- the entire program was written in that style.

Ampt

Did anyone have to maintain that program or was it just an exercise

user55340

exercise.

Ampt

because I know a few guys who would do that to mess with a professor or two haha

user55340

2:15 PM

If you are interested in it, cm.bell-labs.com/cm/cs/who/dmr/kbman.html has the definition of B.

user55340

rvalue ::=
	( rvalue )
	lvalue
	constant
	lvalue assign rvalue
	inc-dec lvalue
	lvalue inc-dec
	unary rvalue
	& lvalue
	rvalue binary rvalue
	rvalue ? rvalue : rvalue
	rvalue ( {rvalue {, rvalue}0 }01 )

user55340

And then in BCPL... section 5.5 in cm.bell-labs.com/cm/cs/who/dmr/bcpl.pdf -- though it doesn't use the ?: notation.

user55340

And if you really want to be mean, in C or C++, an lvalue can be an expression too with a little bit of work.

user55340

*(c==5?&a:&b) = 10;

Jimmy Hoffa

@MichaelT I never realized was Ternary means, that makes it kind of stupid that we call the conditional "ternary" that's like calling increment the Unary operator, it's a name that has little to nothing to do with the purpose

user55340

2:27 PM

@JimmyHoffa But its the only one. There are several unary operators, so confusion may ensue from that (& and * and - being three I can think of off the top of my head in C).

Jimmy Hoffa

@MichaelT sure, it's still stupid though

user55340

then you could call it a ternary conditional... and be half way there.

Jimmy Hoffa

How about if we called the * the asterisk operator

@MichaelT That's fine, but it's almost always called the ternary operator

Now I am interested in that kickstarter. I have whiskey stones but frankly they don't hold the cold for a damn. Had better luck using those plastic ice cube things with the glycol in it, but they leave a plasticy flavor and aren't fit for hot drinks. Oo, there's a question; can you put those things in a hot drink to cool it off? Think iced tea without melting the ice watering it down

The metal might not take kindly to the heat if it has a sealed space inside

@GlenH7 how would stainless steel with a bubble inside respond to immersion in boiling water, expand without harm from the internal vaccuum?

@MichaelT What if they used a non-absorbent interior padding; the water would freeze inside of the padding then expand to press on the padding and not the metal. Probably not a long term solution, eventually the padding would be smushed enough that the water would freeze in contact with the metal and expand at that point

something like a thin memory foam layer around a rubber interior bubble that keeps the water out of the memory foam

then again, you're now insulating the conduction...

Ampt

of course depending on how strong the steal is you could just leave an air pocket to absorb some of the expansion

and compress the air.

Or use a gas that would allow for greater compression

Or use literally any other liquid than water, as it's the only one dumb enough to expand when it turns into a solid.

user55340

2:45 PM

@Ampt The nice thing with water, as mentioned, is that it has a very high heat of fusion and is non-toxic.

user55340

@JimmyHoffa I've seen decanters that have a glass tube that you put in them with ice in it. You get enough melt to get water in the tube that will then act as heat transfer to the ice.

user55340

@Ampt Gases are nearly ideal. They all have nearly the same volume at a given temperature.

Jimmy Hoffa

@MichaelT I'm always afraid of glasses for many of these things, the expansion/contraction pressures cause them to crack unless they're polycarbonate which doesn't have near the conduction of glass

user55340

When I start hunting into the 'food safe non-toxic refrigerant' area, they are rather tight lipped about it. So not sure exactly what it is...

Jimmy Hoffa

> Using biodegradable, non toxic, food safe Hycool® heat transfer fluids.

Just something that came up when I googled "food safe non-toxic refrigerant"

nothing to do with the kickstarter

user55340

2:55 PM

Nope, just that they're getting that stuff from somewhere... and its not the blue freezer gel packs (those are very not non-toxic).

Jimmy Hoffa

brings up another interesting question though; if they used something food safe it's likely far more degradable

so they may have a limited lifetime

I know it; their refrigerant: Air. Scammers.

user55340

If it is in a sealed environment, and given its also cold, the rate of decay may be on the order of decades.

Jimmy Hoffa

addcon.com/en/industrial/coolants/hycool

@MichaelT May, but it's also undergoing energy exchange which increases the rate of decay, and that aside it may be decades, or it may be years, in which case efficacy could diminish in the matter of months; it doesn't have to entirely degrade for it to become useless

user55340

Hmm... there's a way... msds sheets!

user55340

addcon.net/uploads/media/Hycool_din_GB.pdf

Jimmy Hoffa

2:59 PM

@MichaelT this is just a random refrigerant that meets their requirements; no saying they're using it

user55340

But it gets me to find out what it is...

Jimmy Hoffa

wait wait

it said non-toxic, but the MSDS first aid says:

> Immediately move the patient from the source of exposure. General first aid.
Move to fresh air, keep the patient warm and at rest. If unconscious: Loosen
tight clothing, place in stable position on one side. Give artificial respiration if
breathing has stopped. Contact a physician.

user55340

Its not necessarily the one they are using... I'm looking for other ones too.

Jimmy Hoffa

I do enjoy these inhalation instructions:

> Flush mouth, nose and throath with lots of water. Summon physician if
discomfort persists.

lots of water in the throath, and then The Physician will be summoned, he will glide 4 feet above the patient and humm

user55340

addcon.com/en/industrial/coolants/hycool/product-data

user55340

3:03 PM

It seems that thats the stuff... potassium formate in water.

Jimmy Hoffa

With a freezing point of -50 you aren't going to see any phase change in average beverage purposes

user55340

Nope. They might be going for the specific heat increase though... water is still quite high in that area.

Jimmy Hoffa

You could lower the potassium formate concentration and probably get a higher freezing point

ADDCON produces potassium formate of highest purity. It is available as solid or liquid product.

97 % potassium formate (42x25 kg, 500 kg Big Bag, 1000 kg Big Bag)
75 % potassium formate brine (1000 l IBC Container, bulk)

A kickstarter could definitely get their hands on this stuff to mix as they please for their own uses.

user55340

(Water is 4.186 joule/gram)... dunno.... maybe time to ask on chemistry.SE?

user55340

Different topic - dancing to sorting algorithms...

user55340

3:10 PM

►

user55340

There's quicksort for ya.

Jimmy Hoffa

We have 3 data points; 0% freezes at 0c, 30% freezes at -20c, and 50% freezes at -50c, so it's a non-linear progression, but there is a progression based on the amount of potassium formate you use. The average freeze sits at what, -5C? you could probably minimize the concentration to have a freezing point near the average freezer temperature to maximize the phase change requirement

Just have to be careful for those crazy people who keep their freezers at -20c, perhaps it would be better just to use the 30% concentration and call it a day

Or put sufficient warnings: Valid temperature X - Y, do not go below X.

@MichaelT This was the only way the hungarian university could figure out how to get the CS students to learn to dance?

user41796

@JimmyHoffa sufficiently thick steel wouldn't have any issue with expansion / contraction of the material inside. I would imagine / hope that they sized the steel accordingly. As @Ampt indirectly noted, the internal pressure within the steel shape would change. But that should be safely within the limits of the material.

Ampt

3:26 PM

Whatever they are using is light, as it apparently has half the density of soap stone

user55340

@GlenH7 Watch that ice bomb video... where water exploded an iron shell. I've seen it with a larger one that was 1" thick iron.

user41796

They do have an interesting balancing act between manufacturing cost and potential product liability.

Ampt

so either the material they are using is very light, or their stainless steel shell is very thin

Jimmy Hoffa

@GlenH7 Doesn't it have an affect that this will be an ongoing and moving pressure though? It would seem logical that repetitions over the course of 6 months might cause minor internal deformities which the freezing would continue to weaken because after the deformity is there the water will only keep finding it

user41796

@MichaelT I missed the link, I think.

user55340

3:27 PM

11 hours ago, by MichaelT

►

user41796

Oh, @Ampt - I use ternary's all the time. Simple ones are fine. Nesting beyond 2 (maybe 3) layers gets really ugly and shouldn't be done.

user41796

@MichaelT props, thanks. Watching it now

Jimmy Hoffa

@GlenH7 that's when lisp indenting becomes handy

if it's not clear enough I generally write my ternaries as

bla == bla
  ? arrr
  : or else!

so the beginning of the line for each of the options it's clear: this is the true case because the ? and this is the false case because the :

but that's only when doing it on a single line get's a little stretched

user41796

@MichaelT I'm nit-picking, it's 1/8" cast iron, not stainless steel. SS has a much higher (factor of 4) tensile strength than cast iron. And the extreme condition of that ice bath pushes all of the material into a different state. The iron will become much more brittle at those super low temperatures.

Jimmy Hoffa

@MichaelT they could also go for a denser liquid that may not be frozen but can store a large amount of energy, like maple syrup

user41796

3:36 PM

And now that I'm done nitpicking, that was a really cool video. ;-)

user41796

The phase diagram for the material would give a good hint as to how it should operate in "normal" beverage use conditions.

user41796

Phase diagram

A phase diagram in physical chemistry, engineering, mineralogy, and materials science is a type of chart used to show conditions at which thermodynamically distinct phases can occur at equilibrium. In mathematics and physics, "phase diagram" is used with a different meaning: a synonym for a phase space. Overview Common components of a phase diagram are lines of equilibrium or phase boundaries, which refer to lines that mark conditions under which multiple phases can coexist at equilibrium. Phase transitions occur along lines of equilibrium. Triple points are points on phase diagrams wh...

Jimmy Hoffa

They still aren't really taking advantage of "phase change" as they so ardently advertise unless it actually freezes, and I just don't see them actively freezing water, it's not even the expansion but the direction of the expansion, if it froze and expanded in a guided direction that would be one thing but waters expansion is in all directions when frozen, regardless of if some of those directions are held fast

user55340

@GlenH7 The demo that I saw back in college (when funding was plentiful) was a 1 foot diameter ball with 1" thick walls that was put in a box of dry ice. The instructor would put something heavy on it, in a blast shield thing and then continue the lecture from about the third row in.

Jimmy Hoffa

tensel strength or not; repeated freezings would cause weak points over time were it water

user55340

3:40 PM

The first few rows would be cringing (the amount of interest in a lecture is proportional to the likelyhood of the instructor getting hurt) and then it would go bang

Ampt

My guess: It's not water. The high specific heat doesn't offset the large problems that come with expanding solid form

user41796

@JimmyHoffa agreed, and that's a whole other area of material sciences with modeling that.

user55340

This is why CS lectures were so boring... no threat of injury for the instructor.

Jimmy Hoffa

@MichaelT Maybe he should have been spinning on his head the entire time

user41796

@MichaelT If you look at the phase diagram for water in the wikipedia link I posted, the pressure can jump by a factor well over 1000x at the temperature swings they showed.

user55340

3:42 PM

They tried some other ideas (rather than the big heavy iron sphere)... one was a thick walled pipe. They tested that one on the loading dock with about 200 lbs of weight on top of the box. It lifted the box 1 foot in the air from the explosion. They went back to the spheres.

user41796

pipes are nice because you can control which way it will explode. Generally the caps are the weak points.

Jimmy Hoffa

So the question remains, what non-water non-toxic substance has a near-water freezing point?

user41796

@JimmyHoffa question for skeptics.SE? :-)

Jimmy Hoffa

@GlenH7 how is this thermal expansion coefficient compared to water?

3-4 • 10-4 1/K
E.g.: approx.1%
thermal volume
expansion between
–10 and 20°C

You probably understand what that means. I don't even know what a coefficient is

user55340

@GlenH7 It was likely the directed force that was the problem... the thing is, that was a lot more force than they were willing to accept in a lecture hall.

Jimmy Hoffa

3:51 PM

@MichaelT They should just have a 1" thick polycarbonate box bolted to the floor of every lecture halls. (Because all lectures should involve occasional explosions)

user41796

@MichaelT more than I'd be willing to accept. :-) I once had a HS biology teacher who wanted me to hold a glass beaker upside down. He had filled it with hydrogen and was going to ignite it with a burning splint. I declined.

Jimmy Hoffa

@GlenH7 ...ah that's the intelligence training the growing minds of our country...god bless america

user41796

Thermal expansion

Thermal expansion is the tendency of matter to change in volume in response to a change in temperature. When a substance is heated, its particles begin moving more and thus usually maintain a greater average separation. Materials which contract with increasing temperature are unusual; this effect is limited in size, and only occurs within limited temperature ranges (see examples below). The degree of expansion divided by the change in temperature is called the material's coefficient of thermal expansion and generally varies with temperature. Overview Predicting expansion If an equat...

user41796

@JimmyHoffa glass + explosion + my bare hand == "I don't think so"

Jimmy Hoffa

@GlenH7 Yeah, and this is the guy teaching kids. Teaching degrees clearly need to be harder to obtain...

user41796

3:54 PM

@JimmyHoffa Honestly, he was pretty good at teaching biology. But he was also old school and didn't fully think through the liability of some of his actions. Someone else held the tube, and it was just fine. Personally, I wasn't willing to accept the risk.

user41796

But I tend to be a bit paranoid that way. Risk seemed to outweigh any potential benefit, so I acted accordingly

Jimmy Hoffa

Yeah, the only real benefit there is "Hey kids, look what I can do!" -- Surely he ran all the numbers to calculate the rate of energy exchange on the volume of hydrogen he had against the tensel strength of the beaker being held, so he knew it was safe. Surely.

Ampt

Besides, a little glass shrapnel to the hand never killed anyone.

Jimmy Hoffa

@GlenH7 does that thermal coefficient I pasted speak to the amount of expansion when frozen? A solution of water and anything anything would upon freezing still have the expansion of water, no? Though the freezing point may have changed and the expansion may not be the same; the water in the solution would still cause it to happen?

Jimmy Hoffa

4:15 PM

alternatively it could be a gas that liquefies around 0C utilizing that phase change instead... does liquid->gas take as much energy as solid->liquid?

user55340

@JimmyHoffa Thats the heat of vaporization, and it tends to be quite a bit more. The problem is you have either very high pressures or very high temperatures to get enough to make a difference.

Jimmy Hoffa

Pressures being uniformly distributed are much more easily contained though, gas tanks are a well studied and managed thing

user41796

water is a bit unique in that it expands when frozen. Most other things shrink when frozen

Jimmy Hoffa

And it depends on the substance, the nitrogen molecule being so tiny makes a very minimally expansive gas; the solid->gas probably wouldn't create near the pressures of others, granted I'm sure nitrogen is not what is used

user55340

@GlenH7 To an extent, that coincidence has allowed for water based life... otherwise you'd have the oceans freeze from the bottom up. This could be 'bad'

user41796

4:27 PM

while I'm not saying you couldn't do the same thing with a gas -> solid, it's a lot harder on the mfg process for materials handling

Jimmy Hoffa

@GlenH7 I get that; but what non-toxic non-water liquid freezes near waters freezing point? Water's a pretty special thing altogether, there likely aren't many other things that share it's safety properties with it's instability

I should be trolling Chemistry.SE with this right now, you guys are just engineers; what do you know about anything? The lowly construction workers of the science world!

backs away slowly

user41796

actually - you have a valid point

user41796

you need a materials science person to answer your question

user55340

The most we have to deal with liquids is immersion cooling...

user55340

user41796

4:33 PM

good engineers recognize the limits of their knowledge

user55340

1 hour ago, by MichaelT

(Water is 4.186 joule/gram)... dunno.... maybe time to ask on chemistry.SE?

Jimmy Hoffa

I really don't care about the kickstarter at this point, I'm just interested in figuring this out

Ampt

@MichaelT do you use immersion cooling?

user55340

@Ampt Nope. Being a mac guy, I don't have too many choices in hardware cases.

Jimmy Hoffa

@MichaelT Are you saying if you buy a Dell that there is one of the hardware case choices?

Ampt

4:39 PM

ah. I've got an i5 and 5ghz on water cooling but I've always been interested in immersion if it weren't for the need for a tank full of mineral oil

and for the fact that I'm not really sure where all that excess heat would go once it built up in the oil... there's not a heatsink that passes oil through it from what I can tell

and a decently sized radiator is going to have more surface area for cooling than a tank

user41796

@Ampt RE: surface area - that's arguable. The surface area of the tank in the photo above is all of the sides + the top. Technically the bottom contributes too, but I'll pretend it's a thermally dense material underneath it. Granted, you now have two thermal coefficients to worry about (mineral oil + tank material) but the overall surface area should be higher

Jimmy Hoffa

@GlenH7 My understanding was always the more appropriate method for immersion cooling was that you have the liquid heating up but pumping through something which dissipates the heat away and back in at sufficient speed as to cause full liquid change frequently

user41796

@JimmyHoffa yes, that general principle still applies

user41796

but another way of wrapping that around is the dissipation is just the sides of the tank

Jimmy Hoffa

Full conduction cooling is just inefficient compared to the gains you get with proper application of surface area, for instance 48' of copper tubing coiled into 3 feet is a lot of surface area

user41796

4:51 PM

exactly; and that's what the tank offers

user41796

let's say we have a radiator on a CPU. 2" across, 1" high fins, 20 fins total

user41796

total surface area of 2" * 1" * 20 fins * 2 sides = 80 square inches

Ampt

http://www.frozencpu.com/products/5327/ex-rad-110/Black_Ice_GTX_Xtreme_480_Radiator_-_Black.html?tl=g30c95s570
Width of 120mm and thickness of 54mm gives a surface area of 6480mm^s per fin

user41796

12" by 12" by 6" fish tank will have 144 si on just one side

Ampt

at 20 fins per inch and a length of 20 inches, that gives 400 fins * 6480mm is 2,592,000 mm^2

thats 4000 si if my math is correct

user41796

4:53 PM

@Ampt That's a big azz radiator....

Ampt

thats a 4x 120mm radiator. pretty standard

user55340

The next question is how fast can you conduct the heat away.

Ampt

and air is actively passed through the radiator. If there is no movement around that tank, their will be a thermal air buffer

from the radiator? most of them have fans that move about 85 cfm

and 4 would fit on that radiator

so 340 cfm

if not more

obviously a lot of the problem lies in getting the heat into the fins, but largely copper construction seems to help a lot

still not sure that a fish tank would keep up

user41796

@Ampt vs that radiator? It's a good question, yes.

user41796

mineral oil is about 4x more conductive than air

Ampt

5:00 PM

how about glass?

or acrylic?

wouldn't that be the real limiting factor?

user41796

more likely acrylic

user41796

and yes, it will have an effect

user41796

what's a standard fish tank size for this sort of thing? Or is there a standard size?

Ampt

uhhh

no clue. I would guess just like a 75 gallon tank?

Acryllic has a thermal conductivity of .2

user41796

List of thermal conductivities

In heat transfer, the thermal conductivity of a substance, k, is an intensive property that indicates its ability to conduct heat. Thermal conductivity is often measured with laser flash analysis. Alternative measurements are also established. Mixtures may have variable thermal conductivities due to composition. {| style="font-size:95%; text-align:right;" class="wikitable sortable" |- ! Material ! Thermal conductivity [W·m−1·K−1] ! Temperature [K] ! Electrical conductivity @ 293 K[Ω−1·m−1] ! Notes |- | |Acrylic Glass (Plexiglas V045i) | 0.17-0.19 | | - | |- | |A...

user41796

5:02 PM

looks like glass and acrylic aren't going to be the limiting factors

Ampt

nope

but that acrylic is transferring to the air

which isn't moving correct?

unless we think we can get a large enough difference to create a convection cycle

but most computer parts have an upper limit of about 80C

user41796

@Ampt probably a sufficient area that stagnation isn't a concern, but I've never set up a rig like that

Jimmy Hoffa

I still think it's just silly to aim for passive conduction and avoid the radiator pump when the efficiency difference is so drastic

user41796

@JimmyHoffa there's many ways to slice this up, no doubt

user41796

and a 5 gallon tank is ~ 16 x 8 x 10

user41796

5:07 PM

so that would be ~ 610 square inches (ignoring the bottom)

Jimmy Hoffa

the trick about the pump is while your surface area is significant for the tank walls yes, one cc of refrigerant pumped through 48' .5" of copper tube gets 48' * (pi * 2") of surface area to that one CC

user41796

but I'm seeing differing numbers on mineral oil. Air's k is .0257. If mineral oil is .162, that's a ~7x difference

Jimmy Hoffa

passive cooling only get's the surface area to each CC of the space on the acrylic it has access to

user41796

so we're back to comparable between the tank and that big azz radiator

Ampt

(it's not that big)

user41796

5:09 PM

@Ampt it's all relative. :-)

Ampt

frozencpu.com/products/15419/ex-rad-360/…

Jimmy Hoffa

the movement is important because it increases the surface area to volume ratio, stagnant refrigerant only has the surface area of current contact, moving refrigerant has current and future surface area to conduct to

Ampt

that's a big azz radiator

not sure what the fin density is on it though, so it would be hard to guess what kind of surface area we are talking ahout

about*

just kidding it has 18fpi in the title

user41796

fine. I'll get a 10 gal fish tank. ;-)

user41796

interesting range of conversation today

Jimmy Hoffa

5:12 PM

@GlenH7 Don't do it, you can only have a couple really small fish, more than a few and they start dying, luckily my kid didn't care when they died he just liked feeding them

user41796

materials science to hypercooling

user41796

@JimmyHoffa we had hermit crabs in ours. Probably should have put a lot more sand in the base

Ampt

13,192 mm^2 per fin, 18 fins per inch for a length of 17.2 inches gives a total surface area of 4,084,243 mm^2 or 6000 in^2

Jimmy Hoffa

On the bright side 10 gal' is good enough to support a shrimp, which my wife thought was totally gross and creepy, bonus is they like hiding so you just see tentacles sticking out of the filter or wherever. Totally worth the $6

user41796

fish tank + mineral oil are cheaper though. :-)

Ampt

5:14 PM

43.9583 square feet

user41796

I hadn't thought about raising shrimp at home. That's an interesting idea

Jimmy Hoffa

@GlenH7 Out of context, this statement begs questions that shouldn't be asked

Ampt

better star it for late comers to ponder over

user41796

not a whole lot of fun you can have with just a 10gal tank.

Ampt

true true

for cost it's cheaper

I was looking at making a fish tank the other day, but if I did it i would want to do it big

and I have no place for a big enough tank

user41796

5:15 PM

benefit there though is you can make it narrower

user41796

actual fish tanks end up being too deep to be practical for hypercooling, imo

Ampt

Oh, I meant for actual fish

I don't think I would ever do mineral oil because I tinker a lot

user41796

I don't think they'll do too well with mineral oil then

Ampt

and who wants to unsubmerge their parts from mineral oil

Jimmy Hoffa

@GlenH7 Pet store here has all fashion of odd stuff. I need to get a black light so the two neons I got glow properly.

@GlenH7 It would be an interesting sight for a couple moments; they might swim really quickly because of the viscosity before floating to the top

user41796

5:17 PM

did you string some optic tubing in there too? That would be pretty wicked looking

Jimmy Hoffa

They have a few different types of shrimp, clown fish, anemones et al

compare.ebay.com/like/…

that's a good idea @GlenH7..

0

Q: What non-toxic non-water substances have a freezing point very close to water's?

I was linked to a Kickstarter for a cooling ball to be placed in drinks which claims with constant marketing hyperbole how much it relies on "Phase Change" ! which is a neat concept and seems not unreasonable, but in thinking about it I'm failing to imagine (as I'm no chemist, and of ill educatio...

my identicon changed lately. Dunno why, must be using my attached gmail account instead of the attached openid on newer sites...

user41796

@JimmyHoffa saw that the other day and had wondered

Jimmy Hoffa

My new identicon sucks :|

Ampt

5:41 PM

@JimmyHoffa wouldn't the point at which it freezes and the point at which it melts be the same?

its the same operation in reverse

4

Q: Removing $\ce{Ti}$ from $\ce{Ta}$ Crucible

I'm trying to remove titanium filling from a tantalum crucible for a high-temperature effusion cell. I've managed to get a majority of the material out with tweezers, but some remains and is difficult to remove. I understand that sulfuric acid will corrode titanium, but not tantalum, and was co...

experimental-chemistry

stuff like that makes you realize how cool the world is

this guys problem of the day is trying to remove Titanium from a Tantalum crucible

and there are people who can help him

this must be what programmers looks like to laymen

Jimmy Hoffa

@Ampt Sure, but there's an acceptable range, the minimum acceptable point being what your typical freezer runs at, the maximum acceptable point being how cold you want the drink to be. 45F would be fine accept that it's so high your drink would get to 45 because having to commit phase change and 45 is too warm, 10F and your freezer wouldn't freeze it so phase change wouldn't play in.

Just tried to be clear about the acceptable range so that folks who know chemistry could think of some things that land in that range

Ampt

@JimmyHoffa point taken

Jimmy Hoffa

6:03 PM

@Ampt No, programmers rarely do anything that damn cool. Just as chemists rarely do; I'm sure the average chemists job is just as drab as the average programmers. How's them business rules coming along? Yep, just as quickly as when they were written in RPG, that's what I thought.

user41796

@JimmyHoffa - did you try using Wolfram Alpha to find a material that has the right freezing point and enthalpy?

Jimmy Hoffa

@GlenH7 Of course, because who doesn't immediately think of wolfram alpha when they have any general problem at all? ... :P

user41796

and speaking of boring, my day is being spent on chasing down DLL hell

Jimmy Hoffa

Good idea

@GlenH7 I am so happy I don't do builds anymore, and simultaneously happy I did them; I can sniff out assembly dependency resolution problems like a pig in a truffle farm

user41796

@JimmyHoffa yeah, it's amazing how they've so quickly supplanted the term "go google it". I never hear that anymore. It's always "go alpha that"

Jimmy Hoffa

6:09 PM

@GlenH7 I'm going to presume you're being as sarcastic as I was

user41796

@JimmyHoffa never.....

user41796

@JimmyHoffa it's a toolkit we're using. We get frequent drops from them with updates. But the updates frequently drop what we've already done. :-(

Jimmy Hoffa

Oh yeah, wolfram alpha is all over this problem, check this out:

freezing ponit of 32f - water

and then...

freezing point of 29f - water

Ampt

couldn't manage to weasel out a list of compounds that melt between -5 and 5

Jimmy Hoffa

Wolfram Alpha's water is way cooler than the water I'm familiar with, check it out... freezing point of 9f - water

user41796

6:15 PM

Wolfram Alpha is like talking to an engineer. All the knowledge is there, but you have to know how to get at it.

Ampt

?

way cooler than the water your familiar with how?

Jimmy Hoffa

@GlenH7 Not true, if you pay an engineer sufficiently they will talk in layman's terms

Ampt

it melts at 32f?

Jimmy Hoffa

no, when searching for freezing point of anything it just comes back with water

user41796

@JimmyHoffa I've yet to meet that threshold. :-)

Jimmy Hoffa

6:18 PM

@GlenH7 Hard work and practice slay the dragon. I think that's a thing.

user41796

This is what I get for always trying to find an efficient solution

user55340

6:31 PM

Jimmy Hoffa

0

A: Getting rid of immature windfallen apples

Apples, like practically all other organic waste, are ideal for composting. You can cover the apples with leaves, sawdust, other soil, etc., to prevent them being eaten by birds & insects and carried away from your compost pile. But in principle you need nothing but a little patience and soon you...

Alternatively...you could eat them...

user41796

@MichaelT - the ios question is opaque. I don't get what they're asking either.

user55340

@GlenH7 He wants someone to say "yes, its ok to target iOS 5 and ignore the new features of iOS 7 to keep that backwards compatibility."

user55340

I refuse to do marketing research for someone for whom I'm not getting paid, and don't even know what country he's in. There's just the suggestion that there's lots of old devices that can't run iOS 6.

user41796

@MichaelT precisely

user55340

6:39 PM

The link of user agent -> ios version is exactly what you want for this... say you're doing it, advertise it in the appropriate markets, and get the data about what iOS versions are hitting the page.

user55340

-1

Q: supporting iOS 5 and 6 versions and also 7

I think from my previous post I got idea how to write an app if I want both users of iOS5 and iOS6 to use it. Namely, I can set base SDK as 6.1 and deployment target as 5.0, and ensure I don't use iOS 6 specific methods (or use branching if I use iOS6 specific methods). Now, comes the question a...

ios objective-c

user55340

This is the third question about this you've asked in the past day. And the three questions you asked about this 2 days ago were all closed. 6 questions in 2 days on what version to support! — Abizern Aug 15 at 16:48

user55340

@Abizern: This is because I could not get a proper/definitive answer so far on any of these questions that would clear up my mind in this direction. — user2568508 yesterday

user55340

He'll be up to 9 if you count P.SE.

user41796

@MichaelT seriously. how many ways does he need to slice this one up? Several answers on SO address his question. And it's not like it's a complicated answer. "yes, target ios5 and be done with it already."

user55340

6:46 PM

My take on it is "get over iOS 5, target 6 or 7" -- iOS versions dont have the long tail like Android.

user41796

he may be in a place where there are loads of 1st & 2nd gen iPhones, so they may not be able to upgrade. But he ought to know that. And if that's the case then target 5 and be done with it already

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