Energy, Energy Transfer, and General Energy Analysis Flashcards

Vocabulary-style flashcards covering the fundamental concepts of energy forms, heat transfer, work, the first law of thermodynamics, and environmental impacts of energy conversion.

Total energy ($E$)

The sum of all forms of energy a system can possess, including thermal, mechanical, kinetic, potential, electric, magnetic, chemical, and nuclear.

Macroscopic forms of energy

Energy forms that a system possesses as a whole with respect to some outside reference frame, such as kinetic and potential energies.

Microscopic forms of energy

Energy forms related to the molecular structure of a system and the degree of molecular activity.

Internal energy ($U$)

The sum of all the microscopic forms of energy in a system.

Kinetic energy ($KE$)

The energy that a system possesses as a result of its motion relative to some reference frame.

Potential energy ($PE$)

The energy that a system possesses as a result of its elevation in a gravitational field.

Mass flow rate ($\text{m}$)

The amount of mass flowing through a cross section per unit time, calculated as $\text{m} = \rho \text{V}_{\text{avg}} A$ ($kg/s$).

Sensible energy

The portion of the internal energy of a system associated with the kinetic energies of the molecules.

Latent energy

The internal energy associated with the phase of a system.

Chemical energy

The internal energy associated with the atomic bonds in a molecule.

Nuclear energy

The amount of energy associated with the strong bonds within the nucleus of the atom itself.

Thermal energy

The sum of sensible and latent internal energy forms.

Heat transfer

An energy interaction recognized at the system boundary where the driving force is a temperature difference.

Work

An energy interaction recognized at the system boundary where the driving force is not a temperature difference, typically associated with a force acting through a distance.

Mechanical energy

The form of energy that can be converted to mechanical work completely and directly by an ideal mechanical device such as an ideal turbine.

Conduction

The transfer of energy from the more energetic particles of a substance to the adjacent less energetic ones as a result of interaction between particles.

Convection

The transfer of energy between a solid surface and the adjacent fluid that is in motion, involving the combined effects of conduction and fluid motion.

Radiation

The transfer of energy due to the emission of electromagnetic waves (or photons).

Path functions

Variables such as heat and work whose magnitudes depend on the path followed during a process as well as the end states, characterized by inexact differentials ($\text{d}$).

First law of thermodynamics

The conservation of energy principle stating that energy can be neither created nor destroyed during a process, only change forms.

Energy balance

The principle that the net change in total energy of a system during a process equals the difference between the total energy entering and leaving the system ($E_{in} - E_{out} = \text{E}_{system}$).

Stationary Systems

Systems where velocity and elevation remains constant ($\text{AKE} = 0$ and $\text{APE} = 0$), leading to $\text{E} = \text{U}$.

Lower heating value ($LHV$)

The amount of heat released when fuel is burned and the combustion products are cooled to room temperature, where water leaves as a vapor.

Higher heating value ($HHV$)

The amount of heat released when fuel is burned and water in the combustion gases is completely condensed, recovering the heat of vaporization.

Lighting efficacy

The amount of light output in lumens per Watt ($W$) of electricity consumed.

Smog

A pollutant made up mostly of ground-level ozone ($O_3$), carbon monoxide ($CO$), particulate matter, and volatile organic compounds (VOCs).

Acid rain

Precipitation resulting from sulfur oxides and nitric oxides reacting with water vapor and other chemicals in the atmosphere in the presence of sunlight.

Greenhouse effect

The process where glass or atmospheric gases allow solar radiation in but block infrared radiation from leaving, causing thermal energy build-up.