Specific Internal Energy

on . Posted in Thermodynamics

Specific internal energy, abbreviated as u, is a thermodynamic property that represents the energy contained within a unit mass of a substance due to its molecular motion and interactions.  It's a measure of the microscopic kinetic and potential energies of the particles (atoms or molecules) within a substance.  Specific internal energy is an important concept in thermodynamics and plays a key role in understanding the behavior of materials and energy transfer in various processes.

In some situations, substances might undergo phase changes (such as melting, boiling, or condensing), and specific internal energy can change significantly without a change in temperature.  Specific internal energy is an essential concept in the analysis of energy transfer, heat transfer, and thermodynamic processes.  It's used to model and predict the behavior of substances in various contexts, such as engines, refrigeration systems, and chemical reactions.


Specific internal energy formula

\( u =  U\;/\;m \)     (Specific Internal Energy)

\( U =  u \; m  \)

\( m =  U\;/\;u\)

Symbol English Metric
\( u \) = specific internal energy \(Btu\;/\;lbm\)  \(kJ\;/\;kg\) 
\( U \) = internal energy \(Btu\) \( J \)
\( m \) = mass \( lbm \) \( kg \)


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Tags: Energy