Basic Concepts In Thermodynamic Flashcards
Define system, surroundings and system boundary
System refers to a region or space for study. Can be closed or open system.
Surroundings refer to the external of the system.
Boundary separates system for surroundings. Can be fixed or movable
Define open and closed system and their characteristic. Sketch a typical closed and open system
Closed system refers to no energy or mass crossing boundary.
> fixed quantity of matter
> energy can be transferred across boundary (heat/work)
> boundary movable (irregular volume)
Open system has a fixed but movable control volume boundary.
> a selected region in space
> involves mass flow
> energy can cross boundary
Eg. water heater
What is an isolated system
Isolated system refers to a system that is free from influence of external force
Define extensive and intensive properties
Extensive:
> depend on size
> mass, volume, energy
Intensive:
> independent on size of system
> value is not additive
> pressure, temperature, specific vol
What are specific properties and which is the reason for using specific properties
Specific properties refer to per unit mass of the system. They are intensive properties
SG = p / pfresh water
Define state of a system. How it is characterized and its relationship with a process
State system refers to a condition of a system. Described by a required number of properties. Change of one property = change the state of the system
Define equilibrium and different types of balances
Equilibrium = a state in which opposite forces are balanced
> Mechanical (forces, pressure)
Thermal (equality of temp)
Chemical (no further chemical potential change)
Phase (no change in mass of each phase)
What is a state postulate and simple compressible system
Number of properties required to fix a state of system is given by the state postulate.
Simple postulate is a simple compressible system specifies by 2 independent, intensive properties
How is a process defined and how a number of processes make up a thermodynamic cycle
Process refers to change undergone by a system from one state to another. Need to specify initial and final state, path, interaction with surroundings
What is a reversible and irreversible process
Reversible; system and its surroundings restored into initial states
Irreversible; friction, unrestrained expansion of a fluid, heat transfer through temp diff, mixing two substances
Name and define all “iso-“ processes as well as the reversible and adiabatic process and draw them on a common P-V graph
Isothermal: temp is constant
Isobaric: pressure is constant
Isochoric: specific vol is constant
Reversible and adiabatic: reversible without heat trf
How is a steady-flow process defined
Steady flow process is defined as no change with time
Which are the different forms of energy
Energy = macroscopic forms + microscopic forms
Discuss the difference between absolute, gage and vacuum pressures and how these are calculated
Absolute pressure
> actual pressure at a given position
> Pabs = Patm + Pgage
Gage pressure
> how much above or below is the pressure with respect to atmospheric pressure
> Pgage = Pabs -Patm
Vacuum pressure
> pressures below atmospheric
> Pvac = Patm - Pabs
