Thermodynamic definitions Flashcards
How do Gasoline Engines - 4 stroke - operate ?
Four stroke engines operate with a cycle that has 2 complete revolution per complete cycle
How do Diesel Engines operate ?
- also uses the 4-stroke cycle
- differs in its ignition system, engines uses heat generated by compressions to auto-ignite
What is the gas turbine ?
It has a very good power to weight ratio and is thus used for aircraft propulsion
Why are combined cycle gas turbines used ?
The ease of natural gas handling alongside quick spin up times make it economically viable
Thermodynamics
The science of energy
First law of thermodynamics
That energy cannot be created or destroyed but can only change forms
Second law of thermodynamics
It asserts that energy has a quality as well as a quantity and actual processes occur in the direction of decreasing quality of energy
System
A quantity of matter or a region in space chosen for study
Surroundings
The mass or region outside the system
Boundary
The real or imaginary surface that separates the system from its surroundings
Closed system
A fixed amount of mass, and no mass can cross its boundary
Open system
Both mass and energy can cross the boundary of a control volume
Intensive properties
Those that are independent of the mass of a system, temperature, pressure and density
Extensive properties
Those whose values depend on the size of the system
Specific properties
Extensive properties per unit mass
Equilibrium
A state of balance
Thermal equilibrium
If the temperature is the same throughout the entire system
Mechanical equilibrium
If there is no change in pressure at any point of the system with time
Phase equilibrium
If a system involves two phases and when the mass of each phase reaches and equilibrium level and stays there
Chemical equilibrium
If the chemical composition of a system does not change with time, that is, no chemical reactions occur
State postulate
The state of a simple compressible system is completely specified by two independent, intensive properties
Isothermal process
A process during which the temperature remains constant
Isobaric process
A process during which the pressure remains constant
Isochoric process
A process during which the specific volume remains constant
Cycle
A process during which the initial and final states are identical
Quasistatic or quasi-equilibrium process
When process proceeds in such a manner that the system remains infinitesimally close to an equilibrium state at all times
Steady-flow process
A process during which a fluid flows through a control volume steadily
Zeroth law of thermodynamics
If two bodies are in thermal equilibrium with a third body, they are also in thermal equilibrium with each other
Ice point
A mixture of ice and water that is in equilibrium with air saturated with vapor at 1 atm pressure
Steam point
A mixture of liquid water and water vapor in equilibrium at 1 atm pressure
Pressure
A normal force exerted by a fluid per unit area
Absolute pressure
The actual pressure at a given position it is measured relative to absolute vacuum
Gage pressure
The difference between the absolute pressure and the local atmospheric pressure
Vacuum pressures
Pressures below atmospheric pressure
Pascal’s law
The pressure applied to a confined fluid increases the pressure throughout by the same amount
