Convert BTU per Pound-Rankine to Joules per Kilogram-Kelvin

The BTU per Pound-Rankine (symbol: BTU/(lb·°R)) is a unit of specific entropy. An imperial specific-entropy unit equal to approximately 4,186.8 J/(kg·K) — numerically very close to (and traditionally used as numerically interchangeable with) the kJ/(kg·K) value, since BTU/(lb·°R) and kJ/(kg·K) have a conversion factor of exactly 4.1868 / 4.184 ≈ 1.0007 (a coincidence of imperial unit definitions). BTU/(lb·°R) is the dominant unit in US-edition steam tables (Keenan-Keyes-Hill, NIST/ASME Steam Tables US-customary printing), US-edition thermodynamics textbooks (Cengel-Boles, Moran-Shapiro-Boettner US editions; Borgnakke-Sonntag), ASHRAE Handbook tables (refrigerant data through 2024 edition still dual-lists), and US petroleum/refining process design per API and GPSA Engineering Data Book. Reference values: saturated liquid water at 70°F: s_f ≈ 0.0746 BTU/(lb·°R); saturated steam at 14.7 psia (1 atm boiling point): s_g ≈ 1.7567 BTU/(lb·°R); the entropy of vaporization at 1 atm s_fg ≈ 1.4446 BTU/(lb·°R). Convert BTU/(lb·°R) to kJ/(kg·K) by multiplying by 4.1868; the near-unity conversion is why dual-unit thermodynamics textbooks need only one decimal of precision to map between systems.

It belongs to the imperial measurement system.

BTU per Pound-Rankine are commonly used in turbine design, refrigeration analysis, and power plant engineering.

The Joule per Kilogram-Kelvin (symbol: J/(kg·K)) is a unit of specific entropy. The SI unit of specific entropy (entropy per unit mass) per ISO 80000-5 §5-19.1 — used in steady-flow thermodynamics where the relevant entropy quantity is normalized to the mass flow rate through a control volume (nozzles, turbines, compressors, heat exchangers). J/(kg·K) is the universal output unit for computational thermodynamics libraries: CoolProp (open-source Helmholtz-energy-based property library), NIST REFPROP (the gold-standard reference fluid property database), IAPWS-IF97 industrial-formulation steam tables, and commercial process simulators (Aspen Plus, ChemCAD, HYSYS, ProMax). Dimensionally identical to specific heat capacity c_p in J/(kg·K), but physically distinct — entropy is a state function representing energy spreading, while c_p is a heat-flow response coefficient. Reference values per IAPWS-IF97: liquid water at 25°C has s ≈ 367 J/(kg·K); steam at 200°C and 1 bar has s ≈ 7,834 J/(kg·K); R-134a saturated vapor at 25°C has s ≈ 1,718 J/(kg·K); dry air at 25°C and 1 bar has s ≈ 6,876 J/(kg·K) (relative to reference state). Used universally in CFD strong-form energy-equation post-processing (ANSYS Fluent, OpenFOAM, STAR-CCM+).

It belongs to the metric measurement system.

Joules per Kilogram-Kelvin are commonly used in turbine design, refrigeration analysis, and power plant engineering.