Thermodynamics

Explore the zeroth law of thermodynamics and thermal equilibrium, and learn how various temperature measuring instruments—liquid-in-glass thermometers, gas thermometers (constant-volume and constant-pressure), thermocouples, electrical resistance thermometers, and pyrometers—determine temperature.

Explore the history of temperature scales, compare Celsius and Fahrenheit via water's melting and boiling points at atmospheric pressure, and introduce Kelvin and linear interconversion formulas.

Explore the ideal gas equation PV = nRT and the distinction between the universal constant R and the characteristic constant R*, varying with molecular weight, illustrated by air and CO2.

Explore the relation between specific heats at constant pressure and constant volume, noting similar values for liquids and solids, while gases show differences; derive gamma as Cp/Cv and Cp−Cv=R.

Construct a pressure-volume diagram for an ideal gas, showing PV = constant, horizontal and vertical lines, and P inversely proportional to V, with compression and expansion paths.

Construct temperature-entropy diagrams to show isothermal and isentropic lines; relate constant pressure and constant volume heat transfer using cp and cv, and compare temperature changes for gases.

Apply first law of thermodynamics to cycles, linking heat and work with the mechanical equivalent of heat. Contrast closed and open systems, derive energy balance for non-flow and flow processes.

Apply the first law to non-flow closed systems. Derive ∫ P dV for a piston; isochoric processes have zero work; relate P and T for an ideal gas.

Analyze work in a closed system using a piston-cylinder with gas; apply w = ∫ P dV for expansion and -∫ P dV for compression.

Explore the isobaric process at constant pressure, where heating raises temperature and volume, increasing entropy, while calculating work and heat using p v t relations.

Maintain a constant temperature in an isothermal process, where p ∝ 1/v. Compute the work as W = C ln(v2/v1); heat added equals work, ΔU = 0, and entropy increases.

Isentropic process in air-standard cycles: use pv^gamma = c to relate pressure, volume, and temperature, derive p2/p1 and t2/t1, and compute work with zero heat transfer.

Explore the polytropic process in thermodynamics, deriving P V^n = constant, calculating work with W = (P2V2 - P1V1)/(1 - n), and linking temperature, internal energy, and enthalpy changes.

Analyze an ideal gas undergoing a constant pressure process followed by a constant volume step, yielding a final-to-initial volume ratio of 3/4 (0.75).

Explore why heat and work are boundary phenomena and path-dependent, not exact differentials, contrasting them with state functions like internal energy and enthalpy.

Explore how the internal energy of an ideal gas depends on temperature, emphasizing that internal energy is a function of temperature for ideal gases.

Calculate the work for an isothermal compression of an ideal gas in a piston-cylinder, from V1 0.4 m3 to V2 0.1 m3 at P1 100 kPa, yielding about -55.45 kJ.

An ideal gas undergoes a reversible path where pressure varies linearly with volume, from p1=100 kPa, v1=0.2 m³ to p2=200 kPa, v2=0.1 m³, giving a work magnitude of 15 kJ.

Heat an insulated tank with a resistor; it has zero heat transfer, and the lecture computes a 2.3 kW electrical input with negative work and an internal energy change.

Master the steady flow energy equation by applying its five assumptions—constant mass flow, uniform composition, only work and heat interactions, and a time-invariant state—through a control-volume energy balance.

Apply the steady flow energy equation across boilers, EV operator coils, condensers, compressors, turbines, pumps, and nozzles to relate heat transfer, work, and enthalpy changes.

Compute the turbine power and heat rejection for a gas turbine using mass flow rate ṁ = A v / v, inlet area, inlet and outlet velocities, and specific volume.

Analyze an air compressor with inlet 1 bar, v1 0.185 m3/kg, outlet 7 bar, v2 0.16 m3/kg, and internal energy change of 90 kj/kg, with heat rejection 60 kj/s, to estimate power.

This lecture explains work done in open and closed thermodynamic systems, using the steady-flow energy equation, pv diagrams, and process families—isochoric, isobaric, isothermal, isentropic, and polytropic—and their respective work formulas.

Explain the second law of thermodynamics via the Kelvin-Planck and Clausius statements, showing why perpetual motion machines of the second kind cannot exist, and highlight heat pump and a refrigerator.

Describe a heat engine: Q1 from a high-temperature reservoir, Q2 to a low-temperature reservoir, producing work W = Q1 − Q2; compare actual and ideal efficiencies.

Explains a heat pump between cold exterior and warm room, extracts heat from outside, delivers to the room using work, and defines the coefficient of performance as Q1 over W.

Explain how a refrigerator uses work to remove heat from a cold space into a warm surround, define the cooling effect and cop, and contrast heat pumps with refrigerators.

Explore how refrigerators and heat pumps produce cooling and heating effects between thermal reservoirs, the ton of refrigeration (3.5 kW), and analyze two heating engines in series.

Analyze and solve GATE level problems on heat engines, heat pumps, and refrigerators using the second law, coefficient of performance calculations, reversible cycles, and heat transfers between reservoirs.

Explore entropy as a measure of heat's ability to do work. Relate molecular randomness to reversibility and introduce Carnot efficiency and the Clausius inequality.

Explain the entropy change for a closed system using the first law, deriving ΔS with temperature–volume, temperature–pressure, and pressure–volume forms that involve CV, CP, and R.

Explore entropy changes across isochoric, isobaric, isothermal, and polytropic processes in thermodynamics, deriving formulas using Cv, Cp, gamma, and temperature ratios.

Explore how entropy changes in a system, surroundings, and the universe, with positive, negative, or zero system entropy changes, and how the universe's entropy never decreases, increasing in irreversible processes.

Explain availability (exergy) and irreversibility, showing how maximum work comes from heat transfer with the surroundings and how the universe's entropy governs available energy.

Explore availability or available energy as the maximum work obtainable when a system interacts with its surroundings, and analyze irreversibility through entropy of the universe and losses in availability.

examines the availability of an open system via a control volume, dead state with surroundings, and maximum possible work from the steady flow energy equation.

Explore pure substances and phase transitions by tracing heating ice to water to steam at atmospheric pressure, detailing sensible and latent heat, specific heats, and dryness fraction concepts.

Explore phase-change diagrams in thermodynamics, including sublimation, fusion, and vaporization curves on P-T and P-V plots, triple and critical points, and the Meyler chart for specific enthalpy and entropy.

Clarify the critical point with inflection and zero slope, and identify correct statements about saturated liquid, saturated vapor, and compressed liquid. Apply PV and temperature–enthalpy insights to solve gate problems.

Develop core partial differential equation techniques using x, y, z as variables and derive thermodynamic relations. Explore Maxwell relations that link pressure, volume, and temperature with enthalpy.

Explore the first law of thermodynamics for closed and open systems, linking internal energy to heat and work, and derive Helmholtz and Gibbs functions with their differential forms.

Derive Maxwell's relations from the first and second laws of thermodynamics. Relate temperature, pressure, volume, and entropy; this captures 16 equations and 18 total equations.

Explore entropy as a function of temperature and volume, derive the first entropy equation via Maxwell relations, and relate heat transfer at constant volume to cv.

Explains the Clausius-Clapeyron equation derived from the Maxwell relation, applied to liquid–vapor phase change on a temperature–pressure diagram, using saturated liquid and vapor curves and latent heat of vaporization.

Study throttling through a porous plug, an irreversible, insulated process where enthalpy remains constant as pressure drops and volume rises, highlighting the Joule–Thomson coefficient and inversion curve.

Explore how the joule-thomson coefficient determines heating or cooling during throttling, and relate it to the inversion curve and saturation pressure and saturation temperature.