Here's the fermi question: if instead of the conventional aluminum block + heated lid system, we were to pack the sample tubes into a volume of copper particles, and in turn pack these into a box with surfaces that are a either conductive heater/coolers like those for the aluminum block in the conventional design or vents with fans that can blow air into or out of the box and through the copper matrix, then:
1) what distribution of the copper particles' shapes and masses is optimal for thermocycling the tubes? Spheres? Chain? Random chunks? Big, small, or a mixture?
2) if the thermocyclers have identical power supplies, which system is more efficient, and by how much? 1.2x, 2x, 10x, 100x... Whatever the answer I think it will be an interesting surprise.
Consider a hot air convection thermocycler: is it better to preheat the airstream away from the sample and maximize air speed, or is the reduced effectiveness of the slower airspeed that results from packing the heater around the samples offset from conductive heat transfer?
Mac
---------- Forwarded message ---------
From: Mac Cowell <mac@diybio.org>
Date: Thu, Feb 11, 2016 at 2:32 PM
Subject: Re: Copper beads as thermocycling "block" - Was: [DIYbio] What do open source PCRs need?
To: John Griessen <john@industromatic.com>According to wolfram alpha, copper is 6 times more thermally conductive than tin (400 W/mK vs 67 W/mK).That's pretty big. Now I want to run the experiment.We use a solid tin, and a solid aluminum thermocycling block vs copper beads packed all around the tubes. Even if the beads lose 80% of their thermal conductivity due to airspace and poor contact, they will still be conducting (theoretically) 0.20 * 400 W/mK = 80 W/mK, which is more than the solid tin.Additionally, I would like to see what effect forcing air through the copper matrix has on the cooling rate...I'm not a physicist, anyone else want to explain how this is really going to work?On Thu, Feb 11, 2016 at 1:48 PM John Griessen <john@industromatic.com> wrote:If you do any casting with plaster of paris you need to dry it completely before pouring hot metal, or the steam coming out can
splash the hot metal at you. (never experienced that and never want to -- always poured dry molds) Ambient conditions can get
plaster looking dry, but not dry enough -- needs oven time after days of air drying, or more oven time from start.
JG
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