Ron does the following information mean anything to you.....to me it's as clear as mud...(or in our case PC) ha
The R value or R-value is a measure of thermal resistance [1] used in the building and construction industry. Under uniform conditions it is the ratio of the temperature difference across an insulator and the heat flux (heat flow per unit area,
Properties required for good thermal mass
Ideal materials for thermal mass are those materials that have:
- high specific heat capacity,
- high density
Any solid, liquid, or gas that has mass will have some thermal mass. A common misconception is that only concrete or earth soil has thermal mass; even air has thermal mass (although very little.)
The equation relating heat energy to thermal mass is:
where Q is the heat energy transferred, Cth is the thermal mass of the body, and ÄT is the change in temperature.
For example, if 250 J of heat energy is added to a copper gear with a thermal mass of 38.46 J/°C, its temperature will rise by 6.50 °C.
--- In papercreters@yahoogroups.com, Ron Richter <ronerichter@...> wrote:
Since most of us are waiting for warmer weather to arrive to begin PC activities again, I also, am casting about for projects. I teach school (science) in a rural high school in Alaska. Even here the Science Fair looms on the horizon and so casting about for a project that has lots of science and math in it led me to look into the R value question.
Seems mostly the R value is the inverse of the conductivity of the sample being tested. What I have gleaned from my readings so far is that there are a couple of places that do these tests according to ASTM standards and that these "standards" change for almost every type of material tested. Sending hundreds of samples to Oakland National Testing Laboratory is not even feasible.
I have plenty of time and control over the process of making the samples. Can anyone tell us of a simple way to test the samples? Maybe what we get is a time differential for thermal transfer and not the actual R Value, but it could answer the question regarding compaction and what happens. I would love to know that when we say the R value may be higher in a compressed block than loose dried PC we are telling the truth and not guessing.
Any thoughts?
Ron
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