• Throttlor – Joule–Thomson Effect physics T-shirt
  • Throttlor – Joule–Thomson Effect physics T-shirt
  • Throttlor – Joule–Thomson Effect physics T-shirt
  • Throttlor – Joule–Thomson Effect physics T-shirt
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ThrottlorJoule–Thomson Effect

Throttlor – Joule–Thomson Effect Physics T-Shirt

$29.99 USD
$29.99 USD
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Size
S–5XL
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How do you liquefy air? A real gas expanding through a throttle changes temperature. Nitrogen cools a little with each pass, so liquefiers recycle the cooled gas step by step until it condenses. Helium warms instead, being far above its roughly 40 K inversion temperature. Joule and Thomson measured the effect in the 1850s. Pixel-art unisex tee; equation, symbols and sources in the physics panel below.

Color
Size

Size guideS–5XL · inches

Details

Size & fitS–5XL

Unisex heavy cotton (Gildan 5000), classic fit.

SizeWidthLengthSleeve
S182815.1
M202916.5
L223018
XL243119.5
2XL263221
3XL283322.4
4XL303423.7
5XL323525

Measurements in inches, ±1.5 in tolerance.

ShippingFree US

Free US shipping · $10 flat shipping outside the US. Printed to order for you.

Delivery times & where we ship

Returns & replacements21 days

Every item is printed to order, so we can’t accept returns or exchanges for change of mind, or if you ordered the wrong size or colour.

Print defect, misprint, damage or the wrong item? We’ll send a free replacement, or a refund if you prefer. Report it within 21 days of delivery with a photo; no need to send it back.

Full refund & replacement policy

The physics

Push a real gas through a porous plug from high pressure to low, with no heat going in or out, and its temperature changes. Below its inversion temperature it cools.

James Joule and William Thomson (later Lord Kelvin) measured this in the 1850s. The molecules attract each other, so as the gas expands they do work against that attraction and slow down. Enthalpy stays fixed; temperature drops.

It is how fridges work and how air, nitrogen and helium are liquefied. Squeeze through. Chill out.

Equations

\[\mu_{\text{JT}} = \left(\frac{\partial T}{\partial p}\right)_H = \frac{V}{C_p}\left(T\alpha - 1\right)\]
\[T_{\text{inv}} \approx \frac{2a}{R\,b}\quad\text{(van der Waals, low pressure)}\]
SymbolMeaningUnit
\(\mu_{\text{JT}}\) Joule–Thomson coefficient: temperature change per pressure drop at constant enthalpy \(\mathrm{K/Pa}\)
\(T\) temperature \(\mathrm{K}\)
\(p\) pressure \(\mathrm{Pa}\)
\(H\) enthalpy \(\mathrm{J}\)
\(V\) volume \(\mathrm{m^3}\)
\(C_p\) heat capacity at constant pressure \(\mathrm{J/K}\)
\(\alpha\) thermal expansion coefficient \(\mathrm{K^{-1}}\)
\(T_{\text{inv}}\) inversion temperature, below which expansion cools the gas \(\mathrm{K}\)
\(a, b\) van der Waals constants (attraction, excluded volume) \(\mathrm{Pa m^6 mol^{-2}, m^3 mol^{-1}}\)
\(R\) gas constant \(\mathrm{J mol^{-1} K^{-1}}\)

Sources

  1. Joule & Thomson (1854) On the thermal effects of fluids in motion, Part II, Phil. Trans. R. Soc. Lond. 144, 321
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