Discussion Overview
The discussion centers on the search for tabulated values of the heat capacity of air, specifically at low temperatures and pressures. Participants are looking for reliable data on the specific heat at constant pressure (c_{p}) and the ratio of specific heats (γ = c_{p}/c_{v}) in the gas phase, as existing resources primarily provide information at higher pressures.
Discussion Character
- Exploratory
- Technical explanation
- Debate/contested
Main Points Raised
- One participant requests tabulated values for c_{p} and γ at low temperatures and pressures, noting difficulty in finding such data.
- Another participant provides a link to a source with values down to -150°C, but these are at 1 atmosphere pressure.
- A different participant mentions finding data from NIST, but specifies that it pertains to the dew/bubble lines where air becomes liquid, not in the gas phase.
- One participant suggests a source for determining c_{p} and c_{v} for individual components of air, proposing that the overall values could be derived from partial pressures, though this remains uncertain.
- Another participant comments on the independence of specific heats from pressure, suggesting that tabular values from the Engineering Toolbox could be used for low pressure and temperature calculations, while acknowledging the limits of scientific accuracy.
- A participant mentions finding a book titled "Thermodynamic properties of air" that may provide the needed information.
Areas of Agreement / Disagreement
Participants express varying degrees of uncertainty regarding the availability and applicability of heat capacity data at low temperatures and pressures. While some sources are provided, there is no consensus on a definitive resource that meets the original request.
Contextual Notes
Participants note that the specific heats are largely independent of pressure, but this is contingent on the conditions of the gas phase. There are limitations regarding the applicability of certain tabulated values to low pressure scenarios.
