🔁 All frequently repeated questions from GTU exams (✅)
⭐ Unique but important conceptual ones
📘 UNIT 1: Basic Terminology and Energy
| Question | Tag |
|---|---|
| ✅ Define: System, Process, Heat, Work, Internal Energy, Enthalpy | ✅ |
| ✅ State and explain Zeroth law and First law of thermodynamics | ✅ |
| ✅ Define and classify Prime movers with examples | ✅ |
| ✅ Write short note on Renewable Energy Sources | ✅ |
| ✅ Discuss Global Warming and Ozone Depletion | ✅ |
| ⭐ Difference between open, closed, and isolated systems with examples | ⭐ |
| ⭐ Applications of solar, wind, hydro, and bio-fuels | ⭐ |
📘 UNIT 2: Properties of Gases & Steam
🔹 Gases:
| Question | Tag |
|---|---|
| ✅ Define and explain Boyle’s Law, Charles’s Law, Avogadro’s Law | ✅ |
| ✅ Derive relation: cp – cv = R | ✅ |
| ✅ Explain Isothermal, Adiabatic, and Polytropic processes | ✅ |
| ✅ Derive equation of perfect gas (PV = nRT) | ✅ |
| ⭐ Explain with sketch the p-V diagram of polytropic expansion | ⭐ |
🔹 Steam:
| Question | Tag |
|---|---|
| ✅ Define: Dryness fraction, Degree of Superheat, Enthalpy of Steam | ✅ |
| ✅ Explain the concept of steam formation using T-h diagram | ✅ |
| ✅ Classify and define wet, dry, and superheated steam | ✅ |
| ✅ Draw and explain Separating & Throttling calorimeter | ✅ |
| ⭐ State the function of Steam Tables and when to use them | ⭐ |
📘 UNIT 3: Heat Engines & IC Engines
🔹 Heat Engines:
| Question | Tag |
|---|---|
| ✅ Derive expression for Carnot efficiency | ✅ |
| ✅ Derive Otto cycle efficiency with P-V & T-S diagram | ✅ |
| ✅ Derive Diesel cycle efficiency with assumptions | ✅ |
| ✅ Compare Otto and Diesel cycles | ✅ |
| ⭐ State assumptions used in air-standard cycles | ⭐ |
| ⭐ Explain limitations of Carnot cycle | ⭐ |
🔹 Internal Combustion Engines:
| Question | Tag |
|---|---|
| ✅ Compare 2-stroke vs 4-stroke engine | ✅ |
| ✅ Classify IC Engines based on cycle, fuel, strokes | ✅ |
| ✅ Explain working of 4-stroke petrol and diesel engine with diagram | ✅ |
| ✅ List parts of IC engine and explain functions: Piston, Spark plug, Injector | ✅ |
| ⭐ Explain differences between SI and CI engines | ⭐ |
📘 UNIT 4: Boilers
| Question | Tag |
|---|---|
| ✅ Draw and explain Cochran boiler with labeled diagram | ✅ |
| ✅ Explain Babcock & Wilcox boiler construction and working | ✅ |
| ✅ List and explain Mountings & Accessories of boiler | ✅ |
| ⭐ Define Economizer, Superheater, Air preheater | ⭐ |
| ⭐ Advantages of Water-tube over Fire-tube boiler | ⭐ |
📘 UNIT 5: Air Compressors & Pumps
| Question | Tag |
|---|---|
| ✅ Compare Reciprocating vs Rotary compressors | ✅ |
| ✅ Define: Free air delivery, swept volume, volumetric efficiency | ✅ |
| ✅ Explain Centrifugal pump working with diagram | ✅ |
| ✅ Explain Priming and why it's required in centrifugal pumps | ✅ |
| ⭐ Explain working of Diaphragm pump with sketch | ⭐ |
📘 UNIT 6: Refrigeration and Air Conditioning
| Question | Tag |
|---|---|
| ✅ Explain Vapour Compression Refrigeration System with sketch | ✅ |
| ✅ Explain Domestic Refrigerator with labeled parts | ✅ |
| ✅ Difference between Window and Split A/C | ✅ |
| ⭐ Define and explain COP, 1 ton of refrigeration | ⭐ |
| ⭐ Draw diagram of Vapour Absorption System | ⭐ |
| ⭐ Explain working of Split A/C | ⭐ |
📘 UNIT 7: Couplings, Clutches, Brakes, Transmission
| Question | Tag |
|---|---|
| ✅ Explain construction and working of: |
-
Disc clutch,
-
Centrifugal clutch,
-
Cone clutch | ✅
✅ Explain Block brake, Shoe brake, Band brake | ✅
✅ Compare: Clutch vs Brake | ✅
✅ Compare Belt vs Chain vs Gear drive | ✅
✅ Explain functions and types of Couplings: Box, Flange, Flexible | ✅
⭐ Define Shaft, Spindle, Axle | ⭐
⭐ Draw fast and loose pulley and explain | ⭐
📘 UNIT 8: Engineering Materials
| Question | Tag |
|---|---|
| ✅ Define: Elasticity, Plasticity, Ductility, Toughness, Malleability | ✅ |
| ✅ Classify Ferrous vs Nonferrous metals with examples | ✅ |
| ✅ Properties and uses of Glass, Ceramics, Plastics, Graphite | ✅ |
| ⭐ Explain thermal and electrical properties of metals | ⭐ |
| ⭐ Define fatigue, resilience, stiffness | ⭐ |
📘 Unit Wise Numerical
📘 UNIT 2: Properties of Gases & Steam
🔹 Gas Laws, Thermodynamics & Polytropic Processes:
-
S24 Q2(c)
A gas initially at 510 kPa and volume of 142 liters undergoes a certain process after which the pressure and volume reach to 170 kPa and 275 liters respectively. There is enthalpy drop of 65 kJ. The specific heat at constant volume for this gas is 718 J/kg-K.
Calculate:
(1) Change in internal energy
(2) Specific heat at constant pressure
(3) Gas Constant
-
S23 Q2(c)
Air has a volume of 0.15 m³, pressure 1.5 bar, and temperature 107°C. It is compressed at constant pressure until its volume becomes 0.11 m³.
Determine:
(i) Temperature at the end of compression
(ii) Work done
(iii) Change in internal energy
(cp = 1.005 kJ/kg·K, cv = 0.718 kJ/kg·K)
-
W22 Q2(c)
1 kg of air at 7 bar pressure and 90°C undergoes a non-flow polytropic process. The law of expansion is pV^1.1 = constant. The pressure falls to 1.4 bar.
Calculate:
(1) Final temperature
(2) Work done
(3) Change in internal energy
(4) Heat exchange
(R = 287 J/kg·K, γ = 1.4)
-
W23 Q2(c)
A gas with P = 2.75 bar, V = 0.09 m³, T = 185°C changes at constant pressure to T = 15°C.
Find:
(i) Heat transferred
(ii) Work done
(R = 0.29 kJ/kg·K, cp = 1.005 kJ/kg·K)
-
W24 Q2(c)
1 kg of gas is compressed polytropically from 150 kPa, 290 K to 750 kPa. Law: pV^1.3 = C.
Find:
(i) Final temperature
(ii) Work done
(iii) Change in internal energy
(iv) Heat transferred
(v) Change in enthalpy
(R = 0.287 kJ/kg·K, cp = 1.001 kJ/kg·K)
🔹 Steam Calculations & Calorimetry:
-
S24 Q2 (Alt c)
Draw diagram of Separating Calorimeter. Determine the dryness fraction of steam after throttling from pressure 14 bar to 1.1 bar. The initial dryness fraction = 0.70
-
S23 Q3(c)
Steam initially dry saturated at 9 bar:
(i) Loses 50 kJ/kg at constant pressure – find new dryness fraction
(ii) Gains 150 kJ/kg at constant pressure – find degree of superheat
-
W20 Q4(c)
Internal energy of 1 kg of superheated steam at 10 bar and 280°C. Steam expands to 1.6 bar, dryness = 0.8.
(Cps = 2.1 kJ/kg·K)
-
W22 Q2(c)
Convert 4 kg water at 20°C to steam at 8 bar and 200°C
(Cps = 2.1 kJ/kg·K, Cp_water = 4.187 kJ/kg·K)
-
W24 Q2(c)
Data from separating & throttling calorimeter:
Water separated = 0.45 kg
Steam discharge = 7 kg
Main steam pressure = 1.2 MPa
Barometer = 760 mmHg
Manometer = 180 mmHg
Steam temp after throttling = 140°C
(Cps = 2.1 kJ/kg·K)
Find: Dryness fraction
📘 UNIT 3: Heat Engines & IC Engines
🔹 IC Engine Power, Efficiencies:
-
S24 Q3(c)
Diesel engine: 5 kW brake power at 1000 rpm. Mechanical efficiency = 75%. Indicated thermal efficiency = 30%. Diesel fuel: SG = 0.87, CV = 42700 kJ/kg
Find:
-
Fuel consumption (kg/h)
-
Brake thermal efficiency
-
Brake specific fuel consumption
-
W20 Q6(c)
Four-stroke oil engine with rope brake:
Effective brake wheel dia = 630 mm
Dead load = 200 N, Spring = 30 N
Speed = 450 rpm
Indicator diagram: Area = 420 mm², Length = 60 mm
Spring = 1.1 bar/mm
Cylinder = 100 mm × 150 mm
Fuel = 0.815 kg/h, CV = 42000 kJ/kg
Find: BP, IP, η_mech, η_bth, BSFC
-
W22 Q4(c)
Two-cylinder, four-stroke diesel engine:
Swept volume = 870 cm³
Speed = 300 rpm, Torque = 50 N·m
p_mean = 10 bar
Find: IP, BP, Mechanical efficiency
-
W23 Q5(c)
Petrol engine: Compression ratio = 6, Power = 15 kW
Brake thermal efficiency = 0.5 × air standard efficiency
CV = 41500 kJ/kg
Find: Fuel consumption
🔹 Carnot, Otto, Diesel Cycle Theoretical:
-
S24 Q3(c)
Diesel cycle: p1 = 1 bar, T1 = 27°C, Compression ratio = 14, heat addition = 7% of stroke volume
Find: Air standard efficiency (with p-v diagram)
-
W21 Q3(c)
Otto cycle: r = 6, T1 = 25°C, Tmax = 1150°C
Find:
(a) Heat supplied/rejected
(b) Net work
(c) Thermal efficiency
(γ = 1.4, cv = 0.778 kJ/kg·K)
-
W24 Q3(c)
2-stroke diesel engine:
Bore = 10 cm, Stroke = 15 cm
Speed = 1000 rpm
Torque = 58 N·m
η_mech = 80%, η_i_th = 40%, CV = 44000 kJ/kg
Find: IP, p_mean, BSFC
📘 UNIT 4: Compressors & Pumps
-
S23 Q5(c)
6-cylinder 4-stroke engine:
IP = 150 kW, piston speed = 300 m/min
Stroke/bore ratio = 1.25
p_mean = 650 kN/m²
Find: Crankshaft speed
-
W23 Q4(c)
Test on single-cylinder oil engine:
Dia = 270 mm, Stroke = 380 mm
p_mean = 6 bar, Speed = 250 rpm
Load = 1000 N, Brake dia = 1.5 m
Fuel = 10 kg/hr, CV = 44400 kJ/kg
Find: BP, IP, η_i_th
-
W20 Q3(c)
1.5 kg steam at 10 bar, 250°C expands to 2.8 bar, dryness = 0.9
Find: Change in internal energy
-
W21 Q3(c)
Isothermal compression of 1 kg gas from 1 bar, 17°C to 25 bar
R = 260 J/kg·K
Find: Final temperature, Work done, Change in enthalpy
📘 UNIT 5: Refrigeration & Air Conditioning
-
S20 Q4(c)
Energy consumed per month for:
COP = 5, Capacity = 2 TR, No. = 8 AC units
Run time = 4 hr/day
Find: Energy consumed
-
W21 Q5(c)
Construction and working of centrifugal compressor (descriptive with diagram)