thermodynamics banner 3Thermodynamics is both a branch of physics and an engineering science that deals with large scale reactions of a system that can be observed and measures and the relationship between properties such as energy, heat, pressure, temperaturework, etc. on a system.  A physicist is generally intrested in understanding the fundamentals of physics like matter and the laws of thermodynamics.  An engineer is generally intrested in the energy system and its surroundings.  Thermodynamics is mostly based on four universal laws found in the laws of thermodynamics.

There are three thermodynamic systems, open, closed and isolated:

  • Open system freely exchanges energy and matter with its surroundings. 
  • Closed system exchanges only energy with its surroundings, not matter.
  • Isolated system keeps the energy and matter within the system and everything else out.  No transfer in or out.

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Thermodynamics Glossary


  • Adiabatic process  -  The system should be treated as perfectly insulated so there is no heat transfer in or out of the system.  In this process energy is transfered outside the system only by work.
  • Amagat's law  -  States that the volume of a mixture is equal to the sum of the partial volume of its components.
  • Atmospheric air  -  The air in the atmosphere, which normally contains some water vapor.



  • Chemical energy  -  Is when two substances are combined or mixed together (atoms and molecules interacting) to produce a chemical reaction.
  • Closed system  -  Exchanges only energy with its surroundings, not matter.
  • Combustion  -  A reaction called rapid oxidation or burning produced with the right combination of a fuel, oxygen, and heat.
  • Combustion efficiency  -  The amoount of heat released during combustion divided by the heating value of the fuel.
  • Complete combustion  -  A combustion process in which all the carbon in the fuel burns to \(CO_2\), all the hydrogen burns to \(H_2O\), and all the sulfure (if any) burns to \(SO_2\).
  • Compression ratio  -  The ratio of the maximum volume to the minimum volume in a cylinder. 
  • Compressor  -  A device that forces air or gas into a smaller area increasing the volume and creating a usable force of energy.
  • Condenser  -  An outdoor part of the AC or heat pump that releases or collects heat.
  • Critical point  -  The point at which the saturated liquid and saturated vapor states are identical.
  • Critical pressure  -  The pressure of substance at the critical point.
  • Critical properties  -  The properties of a fluid at a location where Mach number is unity.
  • Critical ratio  -  The ratio of the stagnation to static properties when the Mach number is unity.
  • Critical temperature  -  The temperature of substance at the critical point.
  • Critical volume  -  The volume of substance at the critical point.


  • Dead state  -  When a system is in thermodynamic equilibrium with the envitonment.
  • Deficiency of air  -  When the amount of air is less than the stoichiometer amount.
  • Density  -  The ratio of the amount of matter in an object compared to its volume.
  • Dry air  -  Air that contains no water vapor.
  • Dynamic temperature  -  The kinetic energy per unit mass divided by the constant pressure specific heat and corresponds to the temperature rise during the stagnation process.


  • Efficiency  -  Is expressed in percentage and always less than 100%.
  • Enthalpy  -  Measures the sum of internal energy changes in heat under constant pressure of the system.
  • Enthalpy of combustion  - The enthropy of reaction during a steady-flow combustion process when 1 kmol (or 1 kg) of fuel is burned completely at a specific preasure and temperature and represents the amount of heat released.
  • Enthalpy departure  -  The difference between the enthalpy of a real gas and the enthalpy of the gas at an ideal state and it represents the variation of the enthalpy of a gas with pressure at a fixed temperatiure.
  • Enthalpy departure factor  -  The difference between the entropy of a real gas at a given pressure and temperature and the entropy of the gas at an ideal gas state at the same pressure and temperature.
  • Enthalpy of formation  -  The enthalpy of a substance at a specific state due to its chemical composition.
  • Enthalpy of reaction  -  The difference between the enthalpy of the products at a specific state and the enthalpy of the reactants at the same state for a complete reaction.
  • Entropy  -  Measures the unavailable energy in a heat system.
  • Entropy change of a closed system  -  The entropy transfer accompanting heat transfer and the entropy generation within the system boundaries.
  • Equilibrium  -  In a equilibrium state there are no unbalanced potentials, or driving forces within the system.


  • First law of thermodynamics  -  The total amount of energy in the universe is constant and that it can neither be created or destroyed. 


  • Gauge pressure  -  the difference between the absolute pressure and the local atmospheric pressure.
  • Geothermal heat pump  -  Uses the ground as the heat source.


  • Heat  -  A form of energy that causes physical change in what is being heated.  The lack of heat is cold.
  • Heat-driven system  -  Refrigerator systems whose energy input is based on heat transfer from an external source.
  • Heat exchanger  -  A device used to transer heat from one medium to another at different temperatures.  The heat transfer can be air or a liquid such as water or oil.
  • Heat transfer  -  The exertion of power that is created by heat, or the increase in temperature.  It is the transfer of heat from one system to another.  There are four ways to transfer heat: conduction, convection, mixing, and radiation.
  • Henry's law  -  One of the gas laws, at a constant temperature, the volume of a gas which will dissolve into a solution is directly porportional to the partial pressure of that gas above the solution in equilibrium with the liquid.


  • Ideal gas  -  Defined as one in which all collisions between atoms or molecules are perfectly elastic and in which there are no intermolecular attractive forces.
  • Ideal gas law  -  Used to predict pressure, temperature & volume changes in ideal gasses.
  • Ignition temperature  -  The minimum temperature to which a fuel must be brought to start the combustion.
  • Inert gas  -  A gas which does not normally combine chemically with the base metal or filler metal.
  • Internal energy  -  The total of all energies associated with the motion of the molecules in the system.
  • Isobaric process  -  the pressure is kept constant.  To do this, the volume needs to expand or contract in a way that any pressure change would be negated that would be caused by heat transfer in the system.
  • Isolated system  -  Keeps the energy and matter within the system and everything else out.  No transfer in or out.



  • Kinetic energy  -  The energy in moving objects or mass.  If it moves, it has kinetic energy.


  • Latent energy  -  The internal energy associated with the phase of a system.
  • Latent heat  -  The energy absorbed or released by a substance during a constant temperature or phase change from a solid to liquid, liquid to gas or vise versa.


  • Mass fraction  -  The ratio of the mass of one component in a mixture to the total mass of the minture.
  • Matter  -  When you look around, everything you see or may not see in the universe is made up of matter.  If it has a mass and takes up space, it is matter.



  • Open system  -  Freely exchanges energy and matter with its surroundings.


  • Potential energy  -  The possessed energy by a body due to its relative position in a gravitational field.
  • Pressure  -  It is the force exerted perpendicular to the surface of an object and is expressed as force per unit area.




  • Saturated vapor  -  A vapor at a temperature of the boiling point on the verge of condensing.
  • Second law of thermodynamics  -  States that heat cannot pass from a cold body to a hot one by a self-acting process without the help of an external influence.
  • Sensible heat  -  The heat added to a substance which increases its temperature but not the phase.
  • Solubility  -  The maximum amount of solid that can be dissolved in a liquid at a specific temperature.
  • Specific heat  -  The amount of heat required to raise the temperature of a material 1 degree.
  • Specific heat capacity  -  The amount of energy required to increase the temperature of the substance by 1°C.


  • Temperature  -  The amount of heat or cold, but it is neither heat or cold.  Temperature is expressed as a number that is related to energy and porportional to a type of energy, but it is not energy.
  • Thermal energy  -  Tthe exertion of power that is created by heat, or the increase in temperature.
  • Third law of thermodynamics  -  Is about the ability to create an absolute zero temperature, where the entropy approaches a constant minimum value.  It also states that it is not possible for any system to reach absolute zero.
  • Total energy  -  The sum of numerous forms of energy such as chemical, electrical, magnetic, mechanical, nuclear, potential, thermal, and etc.




  • Waste heat  -  Energy that must be dissipated to the atmosphere from a process such as the heat transfer from condensing steam in the condenser of a system power plant.





Display #
Heat Transfer by Convection
Heat Transfer by Radiation
Heat Transfer Coefficient
Heat Transfer Coefficient of a Pipe Wall
Heat Transfer Rate
Henry's Law
High Pressure Steam
Ideal Gas Law
Initial Temperature
Initial Volume
Instantaneous Velocity
Internal Energy
Isobaric Process
Isobaric Process - Enthalpy
Isobaric Process - Entropy
Isobaric Process - Entropy in Terms of Pressure and Volume
Isothermal Process
Latent Heat
Laws of Thermodynamics
Linear Thermal Expansion
Linear Thermal Expansion Coefficient
Linear Thermal Restrained Expansion
Liquid Vapor Mixture