About this previous year paper
This question paper is designed for students studying Engineering Thermodynamics, Refrigeration, Heat Transfer, and Power Plant Engineering. It tests deeper conceptual understanding, numerical accuracy, and the ability to apply thermodynamic laws to real engineering situations. The paper includes topics ranging from basic thermodynamic properties to advanced refrigeration cycles, entropy analysis, steam tables, Rankine cycle, availability, and irreversibility.
The question paper is divided into three major sections: A, B, and C, ensuring a holistic evaluation of theoretical knowledge, descriptive writing skills, problem-solving skills, and application of thermodynamic principles.
SECTION A — Short Conceptual Questions (20 Marks)
Section A contains 10 short-answer questions (each of 2 marks). These questions evaluate the student’s ability to recall and explain basic thermodynamic definitions and principles.
The topics include:
1. Continuum Concept in Thermodynamics
Understanding matter as a continuous distribution without molecular gaps—an essential assumption in classical thermodynamics.
2. State, Path, and Cycle
Basic terms used to describe thermodynamic systems and processes.
3. COP (Coefficient of Performance)
Students must define COP and derive the relationship between:
COP of refrigerator
COP of heat pump
4. Clausius Theorem
Fundamental to the second law of thermodynamics and entropy.
5. Helmholtz & Gibbs Functions
The question tests understanding of thermodynamic potentials used for equilibrium analysis.
6. Coefficient of Volume Expansion
Important property of real substances undergoing heating.
7. First Law Efficiency vs Second Law Efficiency
Comparison of energy-based vs exergy-based efficiency.
8. Saturation, Subcooled Liquid, Superheated Vapour
Basic definitions from steam cycles and phase-change processes.
9. Unit of Refrigeration
Ton of refrigeration and its significance.
10. Types of Refrigerants
Chemical names, classification, and modern eco-friendly refrigerants (R-134a, R-410A, etc.).
This section tests core conceptual clarity, fundamental definitions, and thermodynamic understanding.
SECTION B — Descriptive + Numerical Questions (30 Marks)
Students must answer any three questions (each 10 marks).
These questions emphasize problem-solving, derivation, thermodynamic laws, and steam property analysis.
B(a) Isolated System + Temperature Concept + Numerical on Air Expansion
Difference between heat, temperature, and internal energy
Rigid insulated tank (adiabatic) expansion
Maximum work using thermodynamic relationships
This question tests first law analysis, ideal gas relations, and adiabatic process logic.
B(b) Derivation of Entropy Equation
Deriving the change in entropy for an ideal gas:
ΔS=Rln(V2V1)+Cvln(T2T1)\Delta S = R \ln\left(\frac{V_2}{V_1}\right) + C_v \ln\left(\frac{T_2}{T_1}\right)ΔS=Rln(V1V2)+Cvln(T1T2)
Tests mathematical formulation and understanding of entropy, a key thermodynamic property.
B(c) Joule-Thomson Coefficient + Inversion Curve
Students must explain:
Throttling process
Cooling/heating region
Inversion curve significance in liquefaction systems
Related to refrigeration & gas liquefaction.
B(d) Steam Property Numerical
Given steam initially at high pressure:
Constant volume expansion
Calculation of dryness fraction
Final internal energy
Entropy change
Work done
Uses steam tables, constant-volume process, and property diagrams.
B(e) Actual Vapour Compression Cycle
Students must sketch:
Actual vs ideal VCR cycle on P–h and T–s diagrams
Effect of evaporator pressure (superheat)
Effect of condenser pressure (subcooling)
This evaluates understanding of refrigeration performance and COP variations.
SECTION C — Applied Thermodynamics & Advanced Problems (20 Marks)
Section C consists of 4 advanced questions, each with two options.
Students must answer one part from each question (10 marks each).
Q3 — Thermodynamic Cycles or Equation of State Problems
(a) PMM-II & Quasi Static Expansion Numerical
Discusses impossibility of Perpetual Motion Machine of Second Kind
Gas undergoing quasi-static expansion
Internal energy equation given
Find maximum internal energy and net heat transfer
Tests knowledge of energy interactions, work, quasi-static laws, and U = f(P,V) relations.
(b) Three-Process Cycle Numerical**
Given:
Compression with PV = constant
Heat rejection
Work input/output interactions
Students must compute:
Q12Q_{12}Q12
Q31Q_{31}Q31
This question evaluates the application of the first law of thermodynamics over cycles.
Q4 — Heat Engine & Heat Pump / Entropy of Universe
(a) Combined Heat Engine + Heat Pump System
Understanding:
Energy flows
Efficiency & COP
Heat interactions in combined systems
(b) Entropy Change of Universe
Two cases:
Copper block dropped in lake
Two copper blocks exchanging heat
Tests deep understanding of second law, entropy, and irreversibility.
Q5 — Clausius-Clapeyron Relation / Availability & Irreversibility
(a) Clausius-Clapeyron
Fundamental equation used for phase-change diagrams, vapour pressure curves.
(b) Air Cooling in a Pressure Vessel
Students calculate:
Availability (exergy) in initial & final state
Irreversibility of a real process
This tests a student’s mastery of exergy analysis, a high-level thermodynamic concept.
Q6 — Rankine Cycle or Psychrometric Chart
(a) Moisture at Turbine Exit
Compute:
Maximum allowable boiler pressure
Rankine efficiency
Based on 15% moisture limit
Requires strong understanding of steam power plants.
(b) Psychrometric Processes
Explaining:
Heating & dehumidification
Cooling & humidification
Sensible heating
Sensible cooling
Uses psychrometric charts and HVAC principles.
Q7 — Refrigeration Cycles (Carnot / Bell-Coleman)
(a) Reversed Carnot Cycle
Discuss:
PV & TS diagrams
Limitations of ideal Carnot refrigeration cycle
(b) Air-Refrigeration (Bell-Coleman) Cycle Numerical**
Calculate:
COP
Refrigerating effect
Uses ideal gas relations and compressor/cooler processes.