ft·lbf/(lb·°R)
foot pound-force per pound-Rankine
The foot pound-force per pound-Rankine is 5.380320456 J/(kg·K). It is not really a specific heat unit; it is the unit US thermodynamics texts quote the specific gas constant in, and the gas constant shares its dimensions. Air is 53.35 ft·lbf/(lb·°R), which is the same statement as 287.1 J/(kg·K).
| 1 ft·lbf/(lb·°R) | 5.3803205 J/(kg·K) |
Where the unit came from
The unit exists because early US engineering thermodynamics kept mechanical work in foot-pounds and heat in BTU, refusing to admit they were the same quantity. The mechanical equivalent of heat, 778.17 ft·lbf per BTU, is the bridge between this unit and BTU/(lb·°R).
Solvers that use specific heat capacity