• stoicmaverick@lemmy.worldEnglish
    13·
    4 hours ago

    Okay, who gets to be the lucky one to calculate the amount of time that thing could heat sink a pegged, modern, 120w TDP CPU before it throttles at 100C? I’ll give you a sticker.

    • Contramuffin@lemmy.worldEnglish
      3·
      25 minutes ago

      Was intrigued, so made a simulation to figure it out.

      TLDR: 592.2 seconds, or 9 minutes and 52.2 seconds. Very similar to the other comment, so it appears temperature differentials and heat loss to the air are somewhat minor effects compared to the sheer heat mass of the block

      Assumptions:

      • Copper’s heat conductivity is 400 W/m-K, and specific heat is 0.4 J/g-K, and density is 9000 kg/m^3, and these values do not change over the range of temperatures
      • Air’s heat transfer coefficient is 20 W/m^2-K and does not change over the range of temperatures
      • The surrounding air does not change in temperature and remains at room temperature (25 C)
      • The input wattage is actually 120 W and not just random marketing bullshit
      • The copper block’s size is 4 cm x 4 cm x 16 cm (same as other comment)
      • The temperature within the copper block differs only by the vertical axis; it is assumed that temperature does not change if you move horizontally into the block

      Modeling conditions:

      • The block is sliced into 100 equally-sized slices, stacked vertically.
      • Each slice starts off with a temperature of 25 C
      • 120 W is input directly into the bottom slice
      • Heat transfer is modeled between each slice
      • Heat loss into the air is modeled for each slice (top slice has more heat loss due to more contact with the air)
      • Temperature changes are calculated per millisecond
      • Final time is calculated by the total number of milliseconds it takes for the bottom slice to reach a temperature greater than 100 C

      According to this model, at the time that the CPU thermal throttles, the top of the block should be 85 C

    • KSP Atlas@sopuli.xyzEnglish
      32·
      4 hours ago

      Let’s assume the dimensions of the copper block are 40mm40mm160mm (I’m not taking the heat spreader into account here)

      That results in a volume of 256000mm3, or 256cm3

      Copper (at 20C) has a density of 8.935 g/cm3, so that’s roughly 2.28736kg of copper

      Copper has a specific heat capacity of 384.603 J/(kg K)

      Using E=cm∆t, we can figure out that it would take ≈ 70378J of energy to heat the copper block to 100C, starting at 20C

      With a TDP od 120W, that means it would take 586 seconds to heat the block to 100C, or 9m46s

      This is probably way off but I was bored

      • Contramuffin@lemmy.worldEnglish
        12·
        29 minutes ago

        Hmm, I think at minimum calculus will need to be involved here. Because we can’t just assume that the heat is spread evenly in the copper - it’ll likely be hotter at the bottom, leading to thermal throttling earlier than expected. On the other hand, there’s going to be heat dissipation into the air, which will help cool the block somewhat

        Edit: made a program to model heat transfer and heat loss. It seems to only affect final time by a handful of seconds. So actual time in real life is probably somewhere in the ballpark of 10 minutes

  • BCsven@lemmy.caEnglish
    641·
    5 hours ago

    Till it all gets to temp then it won’t do much. It needs some more surface area to convect heat better.

    With enough fins you don’t need fans.

    • cRazi_man@europe.pubEnglish
      16·
      9 hours ago

      Would a slow small fan still make a huge difference to the cooling here? Completely passive cooling seems like something that would only make sense in very specific professional environments (like needing an ultra low sound floor in an audiology chamber or recording studio).

      • fartographer@lemmy.worldEnglish
        49·
        8 hours ago

        I had a roommate who was getting his doctorate in chemical engineering, specifically focused on graphene. He was able to demonstrate how doping the materials in a heat sink to alter their ability to “release” heat, and then organizing these intentional hotspots along the length of the fins, you could create an active airflow using a stationary object.

        But then his lab manager killed his grant and instead put him on a project partnered with BMW to make their bumpers more marketable.

      • BCsven@lemmy.caEnglish
        5·
        5 hours ago

        The case has an opening for a vertical fan but it is not needed unless you do heavy gaming and run a high end GPU. For video rendering and other tasks the fins are rated to keep it at a decent temp.

        I have good hearing, and a HDD spinning or even a “silent” fan is still audible droning noise to me.

        This build is totally silent. The PSU is over-rated on purpose because it has a below 30% max draw mode that is fanless.
        So this case makes 0 noise.

    • Gork@sopuli.xyzEnglish
      11·
      8 hours ago

      With big enough copper block it might not matter (like the size of a house, but of the good quality stuff not that shit Ea-Nasir sells).

  • Jakylla@jlai.luEnglish
    24·
    9 hours ago

    A block of diamond would be even better (copper being at 401 W/mK, Diamond at 3320 W/(mK), almost 10x better)

    • rockSlayer@lemmy.blahaj.zoneEnglish
      54·
      9 hours ago

      But only 3-5 diamonds are generated per chunk, requires an iron pickaxe, and usually doesn’t start appearing regularly until Y level 14.

      Meanwhile copper can have up to 16 veins of copper per chunk, requires a stone pickaxe, and appears most frequently at Y=48.

      Copper is clearly more accessible for making ore blocks.

      Wait a sec, this isn’t !minecraft@lemmy.world

    • Zachariah@lemmy.worldEnglish
      8·
      9 hours ago

      with the way prices are going, carbon based heat dissipation may become the preferred option

      how pretty would it be if it was a tree-like crystal structure

        • SCmSTR@lemmy.blahaj.zoneEnglish
          3·
          2 hours ago

          Watts per milliKelvin? I wouldn’t think that would be a form of thermal capacity OR thermal dissipation, which is why I asked

          Edit:

          Looked it up…

          Apparently it’s “watt per meter-kelvin”, a/(the?) measurement of thermal conductivity.

          Per Wikipedia ( https://en.wikipedia.org/wiki/Thermal_conductivity_and_resistivity ):

          The thermal conductivity of a material is a measure of its ability to conduct heat. It is commonly denoted by k {\displaystyle k}, λ {\displaystyle \lambda }, or κ {\displaystyle \kappa } and, in SI units, is measured in W·m−1·K−1. It quantifies the proportionality between the heat flux (heat flow rate per unit area, W·m−2) and the temperature gradient (K·m−1) in the direction of heat transport.[1] The reciprocal of thermal conductivity is called thermal resistivity.

          Materials with high thermal conductivity transfer heat more efficiently than those with low thermal conductivity. Heat transport can arise from different microscopic mechanisms: In metals, thermal conductivity is typically dominated by free electrons, whereas in dielectric materials such as diamond it is largely due to lattice vibrations. Materials with high thermal conductivity are used in heat sink applications, while materials with low thermal conductivity, such as mineral wool or Styrofoam, are used for thermal insulation.

  • deliriousdreams@fedia.io
    3·
    8 hours ago

    I am suddenly reminded of that Tech Ingredients video on YouTube where he turned a A/C window unit into a liquid heat pump.