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Principle:
On tank of several litres contents is equipped of one tap tube & one manometer containing one low density liquid column.
the tank is filled up of dry air & a light depression against the external atmosphere, is generated by suction. This
corresponds to the level difference h1 on the manometric column.
After having expected the gas to set to the thermal balance with the external atmosphere, tap R is open. When the
pressure balance is established the tap is closed. During the tap opening, the external air got inside the tank &
adiabatically (?) compressed the gas, which pressure set from H0 – h1 to H0, atmospheric pressure. This isentropic
compression heated the gas. It is represented on diagram P, V by course MN’.
After having closed the tap, the internal air comes back to the room temperature, cooling at constant volume. During this
experiment, depression h2 is generated at the manomerter.
This transformation is represented on the diagram by segment N’N. MN displays one isotherm section
corresponding to the room temperature.
h1/(h1 – h2)
This ratio is actually equal to the M angular coefficients ratio of the MN’ isentropic curve & MN isotherm curve.
When operating with a gas & not with air, it is well advised to generate inital superpressure instead of depression, in order
to avoid the external air coming inside the tank & mixing with the gas. Both successive transformations are then made in
the opposite direction: isentropic triggering followed by constant volume re-heating. The same formula does apply”.
G. Bruhat. 5th edition
Dimension: 370 x 370 x 750 mm.
Weight: 8,5 kg.