Thermodynamics Flashcards
Basic Concepts
What is thermodynamics?
System
Surroundings
Boundary
Types of system
Microscopic Approach or Statistical Approach
Macroscopic Approach or Classical Approach
Pure substance
Property of a system
State of a system
Simple Compressible System
State function (Point function) and Path function
Thermodynamics Equilibrium
Process
Irreversible and Reversible processes
Quasi- Static process
Thermodynamic Cycle
Gibbs Phase Rule
Zeroth Law of thermodynamics
Thermometric Principle (Thermometric Property) Resistance Thermometer (Thermistor) Thermocouples Constant Volume Gas Thermometer Constant Pressure Gas Thermometer
Temperature Scale
Basic Concepts
What is thermodynamics?
Science of energy transfer & its effect on properties of system.
Basic aim of thermodynamics is to convert heat (disorganised form of energy) into work (organised form of energy) in an efficient manner.
System
Surroundings
Boundary
Types of system
Closed, Open, Isolated
Microscopic Approach or Statistical Approach
The behaviour of individual molecules is taken into consideration.
Macroscopic Approach or Classical Approach
The average behaviour of molecues is taken into consideration.
Pure substance
a substance having homogeneous chemical composition & chemical aggregation.
Property of a system
Intensive and Extensive
State of a system
The state of a simple compressible system is completely specified by twoindependent, intensive properties
Simple Compressible System
A system is called a simple compressible system in the absence of electrical, magnetic, gravitational, motion, and surface tension effects.
State function (Point function) and Path function
Thermodynamic Equilibrium
A system is said to be in thermodynamic equilibrium if it is in mechanical, thermal & chemical equilibrium
Mechanical equilibrium - equality of forces/ pressure
Chemical equilibrium - equality of chemical potential
Thermal equilibrium - equality of temperature
Process
Irreversible and Reversible processes
A process when reversed in direction follows the same path as that of the forward path without leaving any effect on system & surrounding is called a reversible process. It is the most efficient. Friction is one of the reasons which makes the process irreversible.
Quasi- Static process
A process carried out at infinitesimal pace is called quasi static process. A friction-less quasi static process is a reversible process.
Thermodynamic Cycle
When initial point & final point of a system is same, after undergoing processes, it is said to have undergone a Thermodynamic cycle.
Gibbs Phase Rule
Relates P, F, C
Zeroth Law of thermodynamics
If a body is in thermal equilibrium with two other bodies, then the other two bodies are in thermal equilibrium with each other.
Thermometric Principle (Thermometric Property)
The property that helps in finding temperature is called Thermometric property.
Resistance Thermometer (Thermistor)
Based on wheatstone bridge principle. Resistance plays the role of themometric property.
Thermocouples
Based on seeback effect. EMF plays the role of thermometric property.
Seeback effect - when two dissimilar metals are joined to form two junctions & if these two junctions are kept at different temperatures an emf is generated which is proportional to the temp. difference between two junctions.
Constant Volume Gas Thermometer
Pressure is the thermometric property
Constant Pressure Gas Thermometer
Volume is the thermometric property
Temperature Scale
Previous - reference 2 temp. ice pt and steam pt.
Now - 1 i.e triple pt. temp. (0.01 degree C)
4 laws of Thermodynamics
4 Laws of Thermodynamics
- Zeroth law, concept of temp.
- The first law, also known as Law of Conservation of Energy, states that energy cannot be created or destroyed in an isolated system.
- The second law of thermodynamics states that the entropy of any isolated system always increases.
- The third law of thermodynamics states that the entropy of a pure crystalline substance at absolute zero temperature is zero.
Properties of Pure Substances
Critical Pt.
saturated state - saturated liquid, saturated vapour
wet vapor -
dryness fraction - quality of mixture
sub-cooled or under-cooled
super-heated vapor
sensible heat -
latent heat -
Enthalpy & Entropy for above regions
Melting, Freezing, Sublimation, Vaporization, Condensation
triple point on P-T and P-V
Triple point and critical point ______ on P-T diagram
Triple point and Critical point ______ on P-V diagram
Reference state in steam tables for U and S
Mollier diagram
Clausius
Clausius-Clapeyron Eq.
Mixture of Ideal Gases
Properties of Pure Substances
Critical Pt.
Point at which saturated liquid curve & saturated vapour curve meet.
saturated state - saturated liquid, saturated vapour
change of phase may occur without change in temperature & pressure.
wet vapor -
both liquid & vapour exists in equilibrium
dryness fraction - quality of mixture
ratio of mass of vapour to the mass of liquid vapour mixture.
sub-cooled or under-cooled
when actual temperature is less than saturation temperature corresponding to that pressure.
super-heated vapor
when actual temp. is greater than saturation temp. corresponding to that pressure.
sensible heat -
Heat transfer associated with temperature change
latent heat -
Heat transfer associated with phase change
Enthalpy & Entropy for above regions
Melting, Freezing, Sublimation, Vaporization, Condensation
S to L - Melting L to S - Freezing S to V - Sublimation V to S - De-Sublimation/ Ablimation L to V - Vaporization V to L - condensation
triple point on P-T and P-V Fixed point (fixed temp. & pressure) at which S, L & V co-exists in equilibrium.
Triple point and critical point both are points on P-T diagram
Triple point is a line & Critical point is point on P-V diagram
Reference state in steam tables for U and S
Mollier diagram
h-s chart
Clausius
Clausius-Clapeyron Eq.
Mixture of Ideal Gases
Energy Interactions
Thermodynamic Work -
Work Transfer -
Convention of work transfer
Generalized Eqn for Closed System Work Transfer
(Non-flow work)
Non-flow or closed system work for various processes
const. volume (isochoric)
const. Press. (isobaric)
const. Temp. (isothermal)
Adiabatic (No heat transfer)
Polytropic
Representation of various processes on pv diagram
for both compression zone and expansion zone
Slope of adiabatic curve and isothermal curve
Power producing cycles -
Power absorbing cycles -
Integrals under p-v plane give ___ interactions and
Integrals under t-s diagram gives ___ interactions
Heat
specific heat capacity at const. P and const. V
I law of thermodynamics (law of conservation of energy)
for isolated systems
for closed systems undergoing a cycle
for closed systems undergoing any process (reversible or irreversible)
for closed systems undergoing reversible process
for closed stationary system undergoing any process
SFEE - Energy Conservation Equation for Open Systems/ CV
PMM I
Enthalpy
Heat transfer in various Non-flow or closed system processes const. vol. const. P isothermal polytropic adiabatic
Energy Interactions
Thermodynamic Work -
work is said to be done by the system if the sole effect on things external to the system can be equated to raising of weights without actual rising of weights.
Work Transfer -
wt is a boundary phenomenon. wt occurs only when it crosses the boundary.
Convention of work transfer
work done by the system is +ve and work done on the system is -ve
Generalized Eqn for Closed System Work Transfer
(Non-flow work) pdv
Non-flow or closed system work for various processes
const. volume (isochoric) w=0
const. Press. (isobaric) w=p(v2-v1)
const. Temp. (isothermal) w= pv ln(v2/v1)
Adiabatic (No heat transfer)w= p1v1-p2v2 / gamma-1
Polytropicw= p1v1-p2v2/ n-1
Representation of various processes on pv diagram
for both compression zone and expansion zone
Slope of adiabatic curve and isothermal curve
Power producing cycles -Clockwise
Power absorbing cycles -Anti-clockwise
Integrals under p-v plane give work interactions and
Integrals under t-s diagram gives heat interactions
Heat
Energy Interaction due to temperature difference is known as heat.
specific heat capacity at const. P and const. V
I law of thermodynamics (law of conservation of energy)
for isolated systems
dE=0
for closed systems undergoing a cycle
delQ = delW
for closed systems undergoing any process (reversible or irreversible)
delQ = dE + delW
for closed systems undergoing reversible process
delQ = dE + pdv
for closed stationary system undergoing any process
delQ = du + delW
SFEE - Energy Conservation Equation for Open Systems/ CV
PMM I
A machine which develops work continuously without consuming some other form energy is called PMM I . Its is impossible to built a PMM I as it violates 1st law.
Enthalpy
sum of internal and flow energy
Heat transfer in various Non-flow or closed system processes const. vol. const. P isothermal polytropic adiabatic
2nd law of thermodynamics
2nd law of thermodynamics -
Thermal Energy Reservoirs -Source and Sink
Kelvin Plank Statement -
PMM II -
Heat Engine -
Clausius Statement -
Refrigerator -
Heat Pump-
Relation between CoP of Refrigerator and Heat Pump
Carnot Cycle -
Carnot’s Theorem -
Clausius Inequality -
Entropy -
Entropy generation -
Combined I and II law relations Tds relations -
slope of const. P and const. V lines on T-S diagram -
Entropy change for an Ideal Gas -
Entropy change for reservoir -
Entropy change for finite body -
2nd law of thermodynamics
2nd law of thermodynamics -
Entropy of an isolated system can never decrease over time.
Thermal Energy Reservoirs -Source and Sink
Reservoir which can supply and absorb heat energy without undergoing any change in temperature.
Kelvin Plank Statement -
It is impossible to develop a device operating on a cycle which produces work continuously by exchanging heat with a single reservoir.
PMM II -
A device that operates on a cycle and produces work continuously by exchanging heat with a single reservoir. 100 efficiency not possible (as heat is low grade energy & work is high grade energy).
Heat Engine -
HE is a device which converts part of heat energy into work and rejects the remaining to surroundings.
Clausius Statement -
It is impossible to develop a device which operates on a cycle and transfer heat from low temperature to high temperature without any external work input.
Refrigerator -
A device to maintain temperature lower than the surroundings.
Heat Pump-
A device to maintain temperature greater than surroundings.
Relation between CoP of Refrigerator and Heat Pump
Carnot Cycle -
thermodynamic cycle with 2 isothermal processes & 2 isentropic processes
Carnot’s Theorem -
No engine operating between two heat reservoirs can be more efficient than a Carnot engine operating between those same reservoirs.
Clausius Inequality -
cyclic integral of delta Q by T is less than or equal to 0
Entropy -
ds = delta Q by T
Entropy generation -
Combined I and II law relations Tds relations -
slope of const. P and const. V lines on T-S diagram -
Entropy change for an Ideal Gas -
Entropy change for reservoir -
Entropy change for finite body -
Available Energy
Available Energy -
Availability -
Availability function -
for open system -
for closed system -
Irreversibility -
Guoy-stodala theorem
Gibbs function
Helmholtz function
Thermodynamic Relation
3 theorems
Maxwells Relations -
Clapeyron’s equation
Clausius Clapeyron equation
2 Tds equations
Cp-Cv equations
Energy Equation
Joules Law -
Joule Thompson Coefficient -
Available Energy
Available Energy -
Maximum possible amount of work that can be extracted from a system is called Available energy.
Availability -
Maximum work obtained from a system when it comes in equilibrium with atmospheric conditions.
Availability function -
for open system - H - T0S
for closed system - U + P0V - T0S
Irreversibility -
Loss of available energy due to dissipation of energy or entropy generation.
Guoy-stodala theorem
Irreversibilty is proportional to entropy generation
Gibbs function
gives maximum work for open system
G = H - TS
Helmholtz function
gives maximum work for closed system
F = U - TS
Thermodynamic Relation
3 theorems
Maxwells Relations -
GPHSUVFT
Clapeyron’s equation
relation comes using maxwell relation del P by del T at const v
Clausius Clapeyron equation
modified form of Clapeyron’s equation
2 Tds equations
Cp-Cv equations
Energy Equation
Joules Law -
Internal energy of an ideal gas is not a function of pressure & volume and only function of temperature.
Joule Thompson Coefficient -
Slope of isenthalpic curve on T-P diagram
