Understanding the Second Law of Thermodynamics

Second Law of Thermodynamics

Describes energy directionality and irreversibility.

Thermal Reservoir

System maintaining constant temperature during heat transfer.

Clausius Statement

Heat cannot transfer from cooler to hotter without work.

Kelvin-Plank Statement

No cycle can produce work from a single reservoir.

Reversible Process

Idealized process with no change to surroundings.

Irreversible Process

Actual processes that cannot return without external work.

Internal Irreversibilities

Irreversibilities occurring within the system.

External Irreversibilities

Irreversibilities occurring outside the system.

Quasi-Equilibrium Process

Internally reversible process with no internal irreversibilities.

Power Cycle

Cycle producing net work transfer from heat.

Heat Transfer In (Qin)

Heat absorbed from the hot reservoir.

Heat Transfer Out (Qout)

Heat released to the cold reservoir.

Thermal Efficiency (η)

Ratio of work output to heat input.

Coefficient of Performance (β)

Efficiency measure for refrigeration cycles.

Coefficient of Performance (γ)

Efficiency measure for heat pump cycles.

Carnot Cycle

Cycle with two adiabatic and two isothermal processes.

Carnot Efficiency

Efficiency equal to 1 - TC/TH.

Carnot Corollary 1

Reversible cycles have higher efficiency than irreversible.

Carnot Corollary 2

All reversible cycles between same reservoirs have same efficiency.

Carnot Corollary 3

Coefficients of performance for refrigeration and heat pumps are equal.

Clausius Inequality

Cycle integral of heat transfer over temperature is non-positive.

Irreversibility Measure (σ)

Represents irreversibility in a thermodynamic cycle.

Energy Balance Equation

Wcycle = Qin - Qout for thermodynamic cycles.

Refrigeration Cycle

Cycle that removes heat from a cold reservoir.

Heat Pump Cycle

Cycle that transfers heat to a warm reservoir.

Friction

Factor causing irreversibility in thermodynamic processes.

Unrestrained Expansion

Irreversible process where gas expands freely.

Mixing of Substances

Irreversible process involving different compositions.

Chemical Reaction

Irreversible process resulting in new substances.

Electric Current Flow

Irreversible process through resistance.