ME-601 Thermal Engineering and Gas Dynamics - Jun 2025 Question Paper

Under each question, How to answer lists the points an answer should cover, outlined by CampusPrep from the syllabus. Check the details against your textbook.

1. 7 Marks
   aDescribe the Velox boiler and its significance in high-pressure steam generation with a neat diagram.
   How to answer

   • Definition of Velox boiler as forced-circulation high-pressure boiler
   • Main components and constructional arrangement
   • Working principle with gas and water/steam circuit
   • Significance for high-pressure high-capacity steam generation
   • Neat labelled diagram
2. 7 Marks
   bWhat are the different classifications of steam generators? Explain them in detail.
   How to answer

   • Basis of classification: fire-tube vs water-tube, pressure, circulation, fuel, mobility etc.
   • Description of each major class with examples
   • Comparison of features and applications
   • Selection criteria for power plant use
3. 7 Marks
   aDefine boiler draught and its purpose. What are the advantages and disadvantages of artificial draught in boilers?
   How to answer

   • Definition of boiler draught and its purpose for combustion and flue gas removal
   • Types: natural vs artificial draught
   • Advantages of artificial draught: control, higher rate, economy
   • Disadvantages: capital, operating cost, maintenance, power consumption
4. 7 Marks
   bThe following data pertain to a steam power plant: Height of chimney 30 m, Draught produced = 16.5 mm of water gauge: Temperature of $360^{\circ} C$; Temperature of boiler house $= 28^{\circ} C$; Atmospheric pressure $= 1.013$ bar. Determine the quantity of air used per kg of fuel burnt in the boiler.
   How to answer

   • Chimney draught formula $h_w = 353 H(1/T_a - 1/T_g)(m_a+1)/m_a$ or equivalent
   • Convert temperatures to Kelvin and draught to water column
   • Solve for air-fuel ratio $m_a$
   • Result in kg air per kg fuel
5. 7 Marks
   aShow Rankine cycle on p-v and T-s diagrams and explain the process involved.
   How to answer

   • T-s and p-v plots of Rankine cycle with four processes
   • Pump, boiler, turbine, condenser processes
   • Explanation of constant pressure heat addition/rejection and isentropic expansion/compression
   • Efficiency expression
6. 7 Marks
   bExplain the working principle of a Feed Water Heater (FWH) in steam power plants. Differentiate between open-type and closed-type feed water heaters.
   How to answer

   • Purpose of feed water heating and working principle
   • Bleed steam heating concept
   • Open-type heater: direct mixing features
   • Closed-type heater: indirect heat exchanger features and differences
7. 7 Marks
   aA steam engine admits steam at a pressure of 5.6 bar and 0.9 dry. The cut off occurs at one-half stroke and pressure at release is 2.6 bar. The back pressure is 1 bar. Find the modified Rankine efficiency of the engine, assuming the pressure drop at release to take place at a constant volume. Neglect clearance volume.
   How to answer

   • Determine enthalpies/entropies at admission, cut-off, release and exhaust using steam tables
   • Account for constant-volume pressure drop at release
   • Calculate heat supplied and work done per cycle
   • Modified Rankine efficiency = work / heat supplied
8. 7 Marks
   bWhat is Mach number? Explain its significance in gas dynamics with examples.
   How to answer

   • Definition of Mach number $M = V/c$
   • Subsonic, sonic, supersonic regimes
   • Significance for compressibility, choking, shocks
   • Examples from nozzles, diffusers, aircraft
9. 7 Marks
   aExplain the concept of one-dimensional isentropic flow of ideal gases through a variable area duct.
   How to answer

   • Assumptions of one-dimensional isentropic flow
   • Governing continuity, momentum, energy equations
   • Effect of area change on Mach number in subsonic/supersonic flow
   • Convergent-divergent duct behaviour
10. 7 Marks
    bWhat is a diffuser? Explain its function and how it affects velocity and pressure in compressible flow.
    How to answer

    • Definition of diffuser
    • Function: kinetic energy to pressure energy conversion
    • Velocity decrease and pressure rise in subsonic vs supersonic flow
    • Applications in compressors and intakes
11. 7 Marks
    aClassify air compressors. Describe the working of single stage reciprocating air compressor.
    How to answer

    • Classification: reciprocating vs rotary, centrifugal vs axial, single vs multistage
    • Construction of single-stage reciprocating compressor
    • Suction, compression, delivery cycle with p-V diagram
    • Valves and clearance effects
12. 7 Marks
    bHow do rotary compressors differ from reciprocating compressors? Explain the working of a centrifugal compressor.
    How to answer

    • Differences: intermittent vs continuous flow, pressure ratio, size, vibration
    • Construction of centrifugal compressor: impeller, diffuser, casing
    • Working: kinetic energy imparted then diffused to pressure
    • Characteristics and applications
13. 7 Marks
    aA single stage, single acting reciprocating air compressor has a bore of 200 mm and a stroke of 300 mm. air at 1 bar and $20^{\circ}C$ and delivers it at 5.5 bar. If the compression follows the law $PV^{1.3} = C$ and clearance volume is 5 percent of the stroke volume Determine:

    1. i)The mean effective pressure;
    2. ii)the power required to drive the compressor, if it runs at 500 r.p.m.
    How to answer

    • Calculate stroke volume and clearance volume
    • Volumetric efficiency and mean effective pressure formula for polytropic compression
    • Indicated work per cycle from $p_m \times V_s$
    • Power = work per cycle × cycles per minute
14. 7 Marks
    bExplain the principles of operation of different types of jet condensers. Describe with sketch a low level jet condenser of the counter flow type.
    How to answer

    • Types of jet condensers: parallel vs counter flow, high vs low level
    • Principle of direct contact condensation
    • Construction and working of low-level counter-flow type
    • Neat sketch with water, steam, air pump connections
15. 7 Marks
    aExplain the supersaturated flow of steam through a nozzle and its effect on discharge and heat drop?
    How to answer

    • Concept of supersaturation and Wilson line
    • Delay in condensation in rapid nozzle expansion
    • Effect on discharge: increased mass flow
    • Effect on heat drop: reduced enthalpy drop
16. 7 Marks
    bWhat are the various sources of air leakage into a steam condenser? How does it affect the performance of the condensing plant?
    How to answer

    • Sources: dissolved air, leakage through joints, glands, valves
    • Effect on vacuum, heat transfer and condensate temperature
    • Effect on pump work and plant efficiency
    • Methods of air removal