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Air - Specific Heat at Constant Temperature and Varying Pressure

Figures and table showing isobaric (Cp) and isochoric (Cv) specific heat of air at constant temperature and varying pressure ranging 0.01 to 10000 bara

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Specific heat or heat capacity (C) is the amount of heat required to change the temperature of a mass unit of a substance by one degree.

  • Isobaric heat capacity  (Cp) is used for air in a constant pressure (ΔP = 0) system.
  • Isochoric heat capacity  (Cv) is used for air in a constant-volume, (= isovolumetric or isometric) closed system.

The specific heat of dry air - CP and CV - will vary with pressure and temperature. This may influence on the accuracy of industrial air handling process calculations. When calculating mass and volume flow of air in heated or cooled systems with high accuracy - the specific heat (= heat capacity) should be corrected according values in the figures and table below.

See also Air Composition and molecular weightDensity at varying pressure, Density and specific weight at varying temperature, Diffusion Coefficients for Gases in AirDynamic (absolute) and kinematic viscosity, Prandtl Number, Specific heat at varying temperatureThermal ConductivityThermal Diffusivity, Properties at gas-liquid equilibrium conditions and Air properties, for other properties of air 

Specific Heat of dry air at constant temperature 20oC / 68°F at various pressures:

air pressure specific heat capacity
Air Cp Cv pressure heat capacity psiaBack to top
Specific Heat of dry air at selected temperatures at various pressures:
Air Cp pressure temperature bar
Air Cp pressure temperature psi
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Specific Heat of dry air at constant temperature 20oC / 68°F at varying pressures:

Pressure Isobaric heat capacity, Cp Isochoric heat capacity, Cv Specific Heat Ratio
[atm] [psia] [kPa] [kJ/(kg K)] [kWh/(kg K)] [kcal/(kg °C)],
[Btu/(lb °F)]
[kcal/(lb °F)] [kJ/(kg K)] [kWh/(kg K)] [kcal/(kg °C)],
[Btu/(lb °F)]
[kcal/(lb °F)] Cp/Cv
0.01 0.147 1.01325 1.0045 0.00027903 0.2399 0.1959 0.71740 0.00019928 0.1713 0.1399 1.4002
0.1 1.47 10.1325 1.0049 0.00027914 0.2400 0.1960 0.71763 0.00019934 0.1714 0.1399 1.4003
0.4 5.88 40.53 1.0053 0.00027925 0.2401 0.1960 0.71766 0.00019935 0.1714 0.1400 1.4008
11) 14.7 101.325 1.0061 0.00027947 0.2403 0.1962 0.71767 0.00019935 0.1714 0.1400 1.4019
7 102.9 709.28 1.0162 0.00028228 0.2427 0.1982 0.71913 0.00019976 0.1718 0.1402 1.4131
10 147 1013.25 1.0216 0.00028378 0.2440 0.1992 0.72005 0.00020001 0.1720 0.1404 1.4188
40 588 4053 1.0756 0.00029878 0.2569 0.2098 0.72858 0.00020238 0.1740 0.1421 1.4763
70 1029 7092.8 1.1305 0.00031403 0.2700 0.2205 0.73778 0.00020494 0.1762 0.1439 1.5323
100 1470 10132.5 1.1824 0.00032845 0.2824 0.2306 0.74703 0.00020751 0.1784 0.1457 1.5828

1) Standard atmosphere  

Unit conversion:

british thermal unit(International table) = [Btu(IT)], degree celcius = [°C], degree fahrenheit = [°F], degree kelvin = [K], degree rankin = [°R], joule = [J], kilocalorie(International table) = [kcal(IT)], kilogram = [kg], kilojoule = [kJ], kilowatthour = [kWh], mole = [mol], pound =[lb]

K in the units can be replaced by °C, and vise versa. °R in the units can be replaced by °F, and vise versa.

  • 1 Btu/(lb °F) = 1 Btu/(lb °R) = 1 kcal(IT)/(kg °C) = 1 kcal(IT)/(kg K) = 4186.8 J/(kg K) = 0.81647 kcal(IT)/(lb °F) = 1.163x10-3 kWh/(kg K)
  • 1 J/(kg K) = 1 J/(kg °C) = 2.3885x10-4 kcal(IT)/(kg oC) = 2.3885x10-4 Btu/(lb °F) = 1.9501x10-4 kcal(IT)/(lb °F)
  • 1 kcal(IT)/(kg °C) = 1 Btu/(lb °F) = 4186.8 J/(kg K) = 0.81647 kcal(IT)/(lb °F) = 1.163x10-3 kWh/(kg K)
  • 1 kcal(IT)/(lb °F) = 1.2248 Btu/(lb °F) = 1.2248 kcal(IT)/(kg °C) = 5127.9 J/(kg K)
  • 1 kJ/(kg K) = 1 kJ/(kg °C) = 1000 J/(kg K) = 1000 J/(kg °C) = 0.23885 kcal(IT)/(kg °C) = 0.23885 Btu/(lb °F) = 0.19501 kcal(IT)/(lb °F) = 2.7778x10-4 kWh/(kg K)
  • 1 kWh/(kg K) = 0.85985 kcal(IT)/(kg °C) = 0.85985 Btu/(lb °F) = 3.6 kJ/(kg K) 
  • 1 mol of air = 28.96546 g

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