Definitions Flashcards
Closed System
No mass can cross boundary but energy can cross via work and heat transfer.
Open System
Mass and energy can cross boundary
Isolated system
No mass or energy can cross boundary. No influence by surroundings on system
Intensive property
Independent of mass of system. e.g: Pressure, Velocity, Temperature, Density
Extensive property
Changes if system is halved. Eg :Volume, Mass, Momentum
Equilibrium
All substances have the same properties.
Steady State
No properties in a certain position in a system change with time.
Isobaric
Constant pressure process
Isochoric
Constant volume process
Isothermic
Constant temperature process
Zeroth law of thermodynamics
When two bodies have equality of temperature with a third body, they in turn have equality of temperature with each other.
Absolute pressure
Pressure relative to a vacuum, always positive
Atmospheric pressure
101 Kapaa, or 1 bar
Gage Pressure
Pressure relative to atmospheric pressure, can be positive or negative
Specific volume
The inverse of density
Pure Substance
Homogenous/ same chemical composition no matter what phase
Phase
Solid, liquid or Gas
State of a system
Defined when two independent intensive properties are know. If we know P and v we can determine T
Compressed liquid
Temperature and Pressure are independent
Gas or Superheated Vapor
Temperature and Pressure are independent
Mixed phase (liquid + vapor) (saturated region)
Pressure and Temperature are not independent
Thermal energy Reservoir
Heat source or sink with large thermal capacity
Heat engine
Converts heat to work
Kevin-Planck Statement
No heat engine can have a thermal efficiency of 100%
Clausius Statement
Refrigerator can’t operate without being plugged in
Carnot hear engine
The efficiency of an irreversible heat engine is always less than the efficiency off a Carnot heat engine operating between the same temp. Reservoirs
Adiabatic Process
A process occurring without heat transfer
Can involve work
