UPSC ESE Mechanical Engineering Thermodynamics Syllabus

Thermodynamics syllabus — full chapter and topic list

Expand any chapter to see its topics and sub-topics. This is the whole examinable outline for Thermodynamics in UPSC ESE Mechanical Engineering, not a summary of it.

1. 1

   Basic Concepts

   3 topics

   • Thermodynamic Systems and Processes
   • Laws of Thermodynamics
   • Entropy and Availability
2. 2

   Thermodynamic Cycles

   3 topics

   • Carnot, Otto, Diesel, Dual Cycles
   • Rankine, Brayton Cycles
   • Refrigeration Cycles

Thermodynamics flashcards for UPSC ESE Mechanical Engineering

18 of 50 cards from the Thermodynamics deck — real questions with worked answers.

1. What is a thermodynamic system, and what are its three classifications based on mass and energy exchange with the surroundings?

   A thermodynamic system is a defined quantity of matter or region in space chosen for study, separated from the surroundings by a boundary. Three types: (1) Open system (control volume) — exchanges both mass and energy; (2) Closed system (control mass) — exchanges energy only, no mass; (3) Isolated system — exchanges neither mass nor energy.

2. Define an intensive property and an extensive property, giving two examples of each.

   Intensive properties are independent of system mass (e.g., temperature, pressure, density). Extensive properties depend on system mass (e.g., volume, internal energy, enthalpy). The ratio of two extensive properties (a specific property) is intensive, e.g., specific volume $v = \frac{V}{m}$.

3. What distinguishes a quasi-static (reversible) process from an irreversible process?

   A quasi-static process proceeds through a succession of equilibrium states infinitesimally close to one another, so it is internally reversible and can be drawn as a continuous path on a property diagram. An irreversible process passes through non-equilibrium states, generates entropy, and cannot be exactly reversed without leaving changes in the surroundings.

4. Name the four basic processes and state the property held constant in each.

   Isothermal process: constant temperature $T$. Isobaric process: constant pressure $p$. Isochoric (isometric) process: constant volume $V$. Adiabatic process: no heat transfer, $Q = 0$.

5. State the Zeroth Law of Thermodynamics and its significance.

   If two systems are each in thermal equilibrium with a third system, they are in thermal equilibrium with each other. Significance: it establishes temperature as a fundamental, measurable property and provides the basis for thermometry.

6. State the First Law of Thermodynamics for a closed system undergoing a process.

   Energy is conserved: the heat added to a system minus the work done by it equals the change in internal energy. $$Q - W = \Delta U$$ In differential form: $\delta Q = dU + \delta W$. For a cycle, $\oint \delta Q = \oint \delta W$.

7. Write the steady-flow energy equation (SFEE) for an open system with one inlet and one outlet.

   $$\dot{Q} - \dot{W}_s = \dot{m}\left[(h_2 - h_1) + \frac{V_2^{2} - V_1^{2}}{2} + g(z_2 - z_1)\right]$$ where $h$ is specific enthalpy, $V$ velocity, $z$ elevation, and $\dot{W}_s$ the shaft work.

8. Define enthalpy and explain why it is convenient in flow processes.

   Enthalpy is defined as $H = U + pV$ (specific: $h = u + pv$). It combines internal energy with flow work $pv$, so for open systems and constant-pressure processes the energy balance is expressed directly in terms of $h$, e.g., $Q = \Delta H$ at constant pressure.

9. What is the relationship $c_p - c_v = R$ for an ideal gas, and what is the ratio $\gamma$?

   For an ideal gas, $c_p - c_v = R$, where $R$ is the specific gas constant. The specific heat ratio is $\gamma = \frac{c_p}{c_v}$. Also $c_v = \frac{R}{\gamma - 1}$ and $c_p = \frac{\gamma R}{\gamma - 1}$.

10. For a reversible adiabatic (isentropic) process of an ideal gas, write the $p$–$V$ and $T$–$p$ relations.

    $$pV^{\gamma} = \text{constant}$$ $$T V^{\gamma - 1} = \text{constant}, \qquad \frac{T_2}{T_1} = \left(\frac{p_2}{p_1}\right)^{\frac{\gamma - 1}{\gamma}}$$

11. Write the work done during a reversible polytropic process $pV^{n} = \text{constant}$ for an ideal gas.

    $$W = \frac{p_1 V_1 - p_2 V_2}{n - 1} = \frac{mR(T_1 - T_2)}{n - 1}$$ valid for $n \neq 1$. For $n = 1$ (isothermal), $W = p_1 V_1 \ln\frac{V_2}{V_1}$.

12. State the Kelvin–Planck statement of the Second Law of Thermodynamics.

    It is impossible to construct a device operating in a cycle that produces no effect other than the extraction of heat from a single reservoir and the production of an equivalent amount of work. In other words, no heat engine can have 100% thermal efficiency.

13. State the Clausius statement of the Second Law of Thermodynamics.

    It is impossible to construct a device operating in a cycle whose sole effect is the transfer of heat from a lower-temperature body to a higher-temperature body. Heat cannot flow spontaneously from cold to hot without external work input.

14. Define thermal efficiency of a heat engine and the COP of a refrigerator and heat pump.

    Heat engine: $\eta = \frac{W_{net}}{Q_H} = 1 - \frac{Q_L}{Q_H}$. Refrigerator: $\text{COP}_R = \frac{Q_L}{W} = \frac{Q_L}{Q_H - Q_L}$. Heat pump: $\text{COP}_{HP} = \frac{Q_H}{W} = \frac{Q_H}{Q_H - Q_L}$. Note $\text{COP}_{HP} = \text{COP}_R + 1$.

15. State the Carnot theorem (Carnot's principle).

    (1) No engine operating between two reservoirs can be more efficient than a reversible (Carnot) engine operating between the same two reservoirs. (2) All reversible engines operating between the same two reservoirs have the same efficiency, independent of the working substance.

16. Write the efficiency of a Carnot engine and the COP of a Carnot refrigerator in terms of reservoir temperatures.

    Carnot efficiency: $$\eta_{Carnot} = 1 - \frac{T_L}{T_H}$$ Carnot refrigerator COP: $$\text{COP}_R = \frac{T_L}{T_H - T_L}$$ with temperatures in absolute (Kelvin) scale.

17. State the Clausius inequality and what it implies.

    $$\oint \frac{\delta Q}{T} \leq 0$$ Equality holds for a reversible cycle; the strict inequality holds for an irreversible cycle. It is the basis for defining entropy and proving entropy generation in irreversible processes.

18. Define entropy in terms of reversible heat transfer.

    Entropy change between two states is defined via a reversible path: $$dS = \left(\frac{\delta Q}{T}\right)_{rev}, \qquad S_2 - S_1 = \int_1^2 \frac{\delta Q_{rev}}{T}$$ Entropy is a property, so $\Delta S$ is path-independent.

See more Thermodynamics flashcards →

Planning Thermodynamics for UPSC ESE Mechanical Engineering

Thermodynamics (UPSC ESE Mechanical Engineering) FAQ