Pirani gauge. Answer to Critics.

For me, the only valid criticism of Tom Shula's interviewis that a Pirani gauge filament typically has low emissivity; ε ~ 0.05. But earth has an emissivity close to 1. Emissivity: ε ~ 0.95 (on average).

In his original presentation, Tom provided a chart with 100 mW power loss at 760 Torr (1 atmosphere). labeled with sp→(for surface pressure). The chart also showed a power loss due to radiation of just below 0.4 mW (at 0.001 Torr and less). That is the red horizontal line labeled: COMBINED RADIATIVE AND END LOSSES

Assume: with a Pirani filament of ε = 0.05, the power loss associated with IR emission = 0.4 mW. Multiply both power and emissivity by 19. 19 x 0.4 = 7.6. It's perfectly legitimate to multiply like this because emissivity is a simple scalar multiplier in the Stefan-Boltzmann Law.

So we can expect a Pirani filament of ε = 0.95 has a power loss associated with IR emission = 7.6 mW; and that this will be seen at low vacuum ≤ 0.001 Torr. [Note 0.001 = 1E-03 in the diagram]. Where the red line and green curve meet horizontally. This is the pressure where all power loss is associated with COMBINED RADIATIVE AND END LOSSES, and we assume the end losses are negligible.

Had we used a Pirani gauge with a filament, ε = 0.95 the we expect a base radiative emission of 7.6mW. This would give a similar chart to that above but the red horizontal line would pass through 7.6mW on the vertical axis, and the green curve would still meet the red line at 1E-03 = 0.001 Torr.

So:
  total power loss at 1 atmosphere (760 Torr) is 100 mW.
  power loss due to radiation is 7.6 mW

This estimate gives a radiative heat loss = 7.6% which is still far less than the 79% climate catastrophe modelers give us; although still 19 times what Tom originally estimated. It still falsifies the greenhouse effect; but less dramatically.

We can, in fact, use a Pirani gauge with a high emissivity filament (such as an oxidized alloy of nickel; 80Ni:20Cr, ε = 0.9, or 20Ni:25Cr:55Fe alloy, ε = 0.90 to 0.97 ). It just so happens that oxidized NiChrome wire is available. But we'll need to calibrate it for ourselves. We'd need to make our own chart of power used versus gas pressure. Or, at the very least, to run the experiment twice - at atmospheric surface pressure ( ~ 760 Torr), and at high vacuum of, say, 0.001 Torr (or less). At such low pressure ALL power loss is assumed to be due to IR emitted.

Or, provided we know the precise emissivity of our Pirani gauge filament, we can just scale it as I did above.