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Why cant I find a chart of materials where each point is a material, and the y axis is thermal conductivity and the x-axis is specific heat capacity
@GregWilson I wish this reply could have earned you 2 follows. Sadly I can only give one :) Thank you.
@freemo The relation between diffusivity (a) and specific heat (Cp) is:
a = k / (rho * Cp)
where k is conductivity, rho is density. So the X axis in this chart is inversely proportional to Cp, but also proportional to k (the y-axis!). The 45 degree dashed lines in the chart are isometric to volumetric specific heat.
@freemo Source: slide 14 of this (sorry for the spammy ad site - was the closest to original source I could find. I don't have a copy of Ashby's book handy): https://www.scribd.com/document/337935389/Ashby-Charts
@freemo If you have anyone in academia willing to help, many universities have a license to the modern incarnation of Ashby's tools, and can make custom charts with exactly the properties you want.
If I found it useful the company I run (or its non-profit depend on where its appropriate) could always probably afford a license. That said I do have a very strong preference for open-source tools that are standards based.
This actually answers what I suspected and wanted to answer. I was wondering if the chart would be nice and well ordered (and if so in what way) or just a random jumble with no real relationship... IT is interesting to see that like I suspected there is indeed a close correlation/pattern relating the two across materials.
I was also thinking how some material with really high specific heat capacity and high conductivity would be a very special thing to have, since you can store a lot of energy in it and get that energy out quickly, which in term of energy dynamics is a bit of a holy grail (like in electronics you tend to get one or the other and not both)
@freemo Not too many free lunches in nature. From this chart, the only way to get off the line common to all materials is structural - making a foam out of it. Not really an analog that can push you in the opposite direction, above the line.
@freemo without taking advantage of phase changes, that is...
@GregWilson The problem is foams have low conductivity but im imagining some super material with higher-than normal conductivity. I cant think of any sort of structure that would be the conceptual dual of a foam structure. Maybe some sort of degenerate matter like neutronium or something?
Actually now my brain is spinning... it would be super cool where neutronium/neutron star core material, would fall on a chart like this.
Sadly i have yet to find any of that on ebay, but ill keep it on my watchlist ;0
@freemo use a fluid. Water has a remarkably high specific heat and conductivity doesn't matter so much in a fluid because you can use forced convection to transport heat to the sink.
@khird Still think of the time it takes to extract heat energy from water, even with its relatively good characteristics. even with huge heat sinks getting the energy out of there is slow.
But more important my thinking here is not at all about practical useful, but rather the fundamental nature of the universe. It is a concept I wrote a lot about and have visited many times. In mathematical terms I am talking about Duals.
So in electronics there is the whole capacitor vs battery compromise, in that you can either have a high capacity and slow access to the energy, or low capacity but quick discharge (fast access). These two relatively constrain themselves through some fundamental law of nature i need to think more on. But it seems duals of it suggest its a fundamental idea in all of nature, so fundamental it fascinates me.
So in this case this seems as a dual expressing that same fundamental relationship, heat capacity is more or less a measure of how much energy i can git in some volume (thermal energy), and thermal conductivity is a measure of how fast you can pull that energy out (or put it in). So it seems like the thermal equivalent of a capacitor vs a battery, and I wondered if it had the same fundamental trade-off (as I suspected it did).
It seems it does...
I need to think more on this, but thats where my head is.
@freemo The style of chart you're looking for is an Ashby chart. With some google-foo, the closest flavor of Ashby chart to what you want I could find publicly available is this: