Engineering ToolBox - Resources, Tools and Basic Information for Engineering and Design of Technical Applications!

Gases - Ratios of Specific Heat

Ratios of specific heat for gases with constant pressure and volume processes.

Sponsored Links

Internal Energy

For an ideal gas the internal energy - u - is a function of temperature. A change in internal energy can be expressed as

du =cv dT                            (1)

where

du = change in internal energy (kJ/kg)

cv = specific heat for gas in a constant volume process (kJ/kgK)

dT = change in temperature (K)

Specific heat cv varies with temperature but within moderate temperature changes the specific heat - cv - can be regarded as constant.

Enthalpy

For an ideal gas the enthalpy - h - is a function of temperature. Change of enthalpy can be expressed as

dh = cp dT                         (2)

where

dh = change in enthalpy (kJ/kg)

cp= specific heat for gas in a constant pressure process (kJ/kgK

Specific heat cp can within moderate temperature changes be regarded as constant.

The enthalpy in a fluid is defined as:

h = u + p / ρ                           (3)    

where

h = enthalpy  (kJ/kg)

u = internal energy    (kJ/kg)

p = absolute pressure (Pa)

ρ = density (kg/m3)

Combining (3) and the Ideal Gas Law:

h = u + R T                         (4)

where

R = the individual gas constant (kJ/kgK)

Change in enthalpy can be expressed by differentiating (4):

dh = du + R dT                      (5)

Dividing (5) with dT:

(dh / dT) - (du / dT) = R                         (6)

Modifying (6) with (1) and (2):

cp - cv = R                                 (7)

The difference cp - cv is constant for an ideal gas.

Ratio of Specific Heat

The Ratio of Specific Heat can be expressed as:

k = cp / cv                                  (8)

where

k = Ratio of Specific Heat

Ratio of Specific Heat for some gases:

Gases - Ratios of Specific Heat
Gas Ratio of Specific Heat
- k -
Acetylene 1.30
Air, Standard 1.40
Ammonia 1.32
Argon 1.66
Benzene 1.12
N-butane 1.18
Iso-butane 1.19
Carbon Dioxide 1.28
Carbon Disulphide 1.21
Carbon Monoxide 1.40
Chlorine 1.33
Ethane 1.18
Ethyl alcohol 1.13
Ethyl chloride 1.19
Ethylene 1.24
Helium 1.66
N-heptane 1.05
Hexane 1.06
Hydrochloric acid 1.41
Hydrogen 1.41
Hydrogen chloride 1.41
Hydrogen sulphide 1.32
Methane 1.32
Methyl alcohol 1.20
Methyl butane 1.08
Methyl chloride 1.20
Natural Gas (Methane) 1.32
Nitric oxide 1.40
Nitrogen 1.40
Nitrous oxide 1.31
N-octane 1.05
Oxygen 1.40
N-pentane 1.08
Iso-pentane 1.08
Propane 1.13
R-11 1.14
R-12 1.14
R-22 1.18
R-114 1.09
R-123 1.10
R-134a 1.20
Steam (water) 1.33
Sulphur dioxide 1.26
Toluene 1.09

The Ratio of Specific Heat is dimensionless and the value is the same in the SI and the Imperial system of units.

Sponsored Links

Related Topics

  • Fluid Mechanics

    The study of fluids - liquids and gases. Involving velocity, pressure, density and temperature as functions of space and time.

Related Documents

Sponsored Links

Search

Search is the most efficient way to navigate the Engineering ToolBox.

Engineering ToolBox - SketchUp Extension - Online 3D modeling!

3D Engineering ToolBox Extension to SketchUp - add parametric components to your SketchUp model

Add standard and customized parametric components - like flange beams, lumbers, piping, stairs and more - to your Sketchup model with the Engineering ToolBox - SketchUp Extension - enabled for use with older versions of the amazing SketchUp Make and the newer "up to date" SketchUp Pro . Add the Engineering ToolBox extension to your SketchUp Make/Pro from the Extension Warehouse !

Translate this Page

Translate this page to Your Own Language .

About the Engineering ToolBox!

Privacy Policy

We don't collect information from our users. More about

Citation

This page can be cited as

  • The Engineering ToolBox (2003). Gases - Ratios of Specific Heat. [online] Available at: https://www.engineeringtoolbox.com/specific-heat-ratio-d_608.html [Accessed Day Month Year].

Modify the access date according your visit.

3D Engineering ToolBox - draw and model technical applications! 2D Engineering ToolBox - create and share online diagram drawing templates! Engineering ToolBox Apps - mobile online and offline engineering applications!

Unit Converter

















































3.15.9

Sponsored Links
.