Uninterruptible Power Supply | UPS
Fermi Dirac Distribution Function
Fault of Electric Cable
Energy Bands in Crystals
Gallium Arsenide Semiconductor
Atomic Energy Levels
Engineering Thermodynamics Part 1
Science of Engineering Thermodynamics Part 2
Basic Law of Conservation and First Law of Thermodynamics
Carnot Cycle and Reversed Carnot Cycle
Enthalpy Entropy and Second Law of Thermodynamics
Rankine Cycle and Regenerative Feed Heating
Rankine Cycle for Closed Feed Water Heaters and Rankine Cycle Cogeneration
Ideal Verses Actual Rankine Cycle
Rankine Cycle Efficiency Improvement Techniques
Steam Boiler | Working principle and Types of Boiler
Methods of Firing Steam Boiler
Fire Tube Boiler | Operation and Types of Fire Tube Boiler
Water Tube Boiler | Operation and Types of Water Tube Boiler
Steam Boiler Furnace Grate Firebox Combustion Chamber of Furnace
Feed Water and Steam Circuit of Boiler
Boiler Feed Water Treatment Demineralization Reverse Osmosis Plant Deaerator
Coal Combustion Theory
Fluidized Bed Combustion | Types and Advantages of Fluidized Bed Combustion
Steam Condenser of Turbine
Jet Condenser | Low Level High Level Ejector Jet Condenser
Surface Steam Condenser
Economics of Power Generation
Cooling Tower Useful Terms and Cooling Tower Performance
Cooling Tower Material and Main Components
Power Plant Fire Protection System
Hydrant System for Power Plant Fire Protection
Medium Velocity Water Spray or MVWS System for Fire Protection
Foam Fire Protection System
Fire Detection and Alarm System
Gas Extinguishing System
Electric Power Generation
Power Plants and Types of Power Plant
Thermal Power Generation Plant or Thermal Power Station
Hydro Power Plant | Construction Working and History of Hydro power plant
Nuclear Power Station or Nuclear Power Plant
Diesel Power Station
Why Supply Frequency is 50 Hz or 60 Hz?
Economiser in Thermal Power Plant | Economiser
MHD Generation or Magneto Hydro Dynamic Power Generation
Cogeneration | Combined Heat and Power
Thermoelectric Power Generators or Seebeck Power Generation
Cost of Electrical Energy
Gas Turbine Power Plant
Solar Energy Solar Electricity
Solar Energy System | History of Solar Energy
Types of Solar Power Station
Components of a Solar Electric Generating System
What is photovoltaic effect?
Staebler Wronski Effect
Working Principle of Photovoltaic Cell or Solar Cell
Characteristics of a Solar Cell and Parameters of a Solar Cell
Solar Cell Manufacturing Technology
What is a Solar PV Module?
What is Standalone Solar Electric System?
Steam Dryness Fraction
Superheated Steam and Steam Phase Diagram
Vapour Properties Mollier Chart Heat Capacities
What is Steam Flashing?
How to Calculate Steam Consumption During Plant Start Up
Effective Steam Distribution System
What is Water Hammer?
Basic Wind Energy
Wind Turbine | Working Types and History of Wind Turbine
Theory of Wind Turbine
Enthalpy Entropy and Second Law of Thermodynamics
- Internal Energy and First Law of Thermodynamics
- Cyclic and arbitrary process of a system
- Reversibility and Irreversibility
- Entropy and Entahlpy
- Second Law of Thermodynamics
Internal Energy and First Law of ThermodynamicsWhen energy of a molecule with in a system is associated with the property of the system, then it is termed as Internal Energy(u). Energy neither be created nor be destroyed and based on this principal system internal energy(u) changes whenever energy-crosses the system boundary.
Thus the first law of thermodynamics can be expressed as given below when heat/work interacts-with-the-system. In the above equation u is the internal energy per-unit-mass and q and w are heat and work per unit mass respectively. The sign convention adopted in the above equation is: dq > 0 (considered as positive) ⇒ Heat transfer to the system dq < 0 (considered as negative) ⇒ Heat transfer from the system dw > 0 (considered as positive) ⇒ work done by the system dw < 0 (considered as negative) ⇒ work done on the system
Cyclic and Arbitary Process of a SystemOne of the important form of First law of thermodynamics is obtained when We integration above equation for a cyclic process. A system said to be in cyclic process, when after undergoing random changes on account of heat/work returns to its original state. Points to ponder are:
- Integration of any state property differential is the difference of its limits.
- Final state is same as the original state and there is no change in internal energy of the system.
Arbitrary process of a systemIt is outcome of First law of thermodynamics and is related with the equation (1) if a system involves arbitrary process. In this equation q and w are the net heat transferred and net work for the process respectively, while uf & ui are final and initial values of internal energy(u). In a rigid and isolated adiabatic system (w=0, q=0), then its internal energy(u) remains unchanged. Then from eq(2) of a cyclic process
Reversibility and IrreversibilitySystem is said to be undergone a process when it initial state changes to final state. Properties like pressure, volume, enthalpy, temperature, entropy etc changes during a thermodynamic processes. Second law of thermodynamics categories the processes under two heads
- Ideal or reversible processes
- Natural or irreversible processes
IrreversibilityWhen actual processes fails to meet the requirements of reversibility, then the processes is called irreversible. In irreversibile process the initial state of the system & surrounding can’t be bring back to initial state from final state. Entropy of the system increases sharply in irreversible process and the value can’t be brought back to the initial value from the final value. Irreversibility persists on account of variation in pressure, composition, temperature, composition main caused by heat transfer, friction in solid and liquid, chemical-reaction. Professions are busy in putting their efforts to bring down the effects of irreversibility in processes and mechanisms.
Entropy and EnthalpyLike internal energy, Entropy and Enthaly are thermodynamic properties. The entropy is represented by symbol s and change in entropy Δs in kJ/kg-K. Entropy is a state of disorder. Entropy is the subject of second Law of thermodynamics which describes entropy change in system and surrounding with respect to Universe. Entropy is defined as ratio heat transfer to the absolute temperature in a system for a reversible thermodynamic path. Where qrev denotes heat transfer along a reversible path. Enthalpy (h) is the property of state and is defined as,
Where, h is specific Enthalpy, u is specific internal energy, v is specific volume, p is the pressure. From, equation (1) Therefore By differentiating the eq (4) and substituting it in above equation, then Both of above equations are related to changes in entropy for reversible processes on account of changes in internal energy and volume in former and to change in enthalpy and pressure in later equation. Since all quantities in these two equations are state properties, thus entropy is also a thermodynamic property.