ME-601 Thermal Engineering and Gas Dynamics - May 2024 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. 14 Marks
   Draw a neat sketch of Lamont Boiler, show flue gas and water path on it and have important path on the sketch.
   How to answer

   • Definition and working principle of Lamont boiler as forced-circulation high-pressure boiler
   • Labelled neat sketch showing drum, pump, evaporator tubes, superheater, economizer
   • Mark flue gas path and water/steam circulation path with arrows
   • List important parts and their functions
2. 14 Marks
   Define and explain followings.

   1. i)Heat balance sheet
   2. ii)Equivalent evaporation
   How to answer

   • Define heat balance sheet and its heat credit/debit items
   • Explain procedure to draw heat balance on per kg of fuel basis
   • Define equivalent evaporation and formula from and at 100°C
   • Give significance and example calculation
3. 14 Marks
   A steam turbine plant is supplied with steam at pressure of 17 bar and superheated to $100^{\circ}C$. The exhaust pressure is 0.06 bar. The temperature of condensate in the hot well is actually $33^{\circ}C$ ($V_{f} = 0.001$ $m^{3}/kg$) if the measured steam condensate is 5 kg/kWh and if generator efficiency is 96%, what is overall thermal efficiency of the whole plant?
   How to answer

   • Obtain h1, s1 for 17 bar 100°C superheated steam from steam tables
   • Determine Rankine cycle work, pump work using Vf, and heat supplied
   • Use specific steam consumption 5 kg/kWh to get indicated/thermal efficiency
   • Multiply by generator efficiency 96% for overall plant thermal efficiency
4. 14 Marks
   Explain the following.

   1. i)Mach Number
   2. ii)Mach Cone
   3. iii)Zone of action
   4. iv)Zone of silence
   How to answer

   • Define Mach number M = V/a and subsonic/supersonic regimes
   • Explain Mach cone geometry and Mach angle mu = sin^-1(1/M)
   • Define zone of action as region inside Mach cone influenced by disturbance
   • Define zone of silence as region outside Mach cone unaffected
5. 7 Marks
   aExplain working of reciprocating air compressors.
   How to answer

   • Describe construction: cylinder, piston, valves, crank drive
   • Explain suction, compression and delivery strokes with p-V diagram
   • Explain valve operation and single-acting cycle
   • State applications and limitations
6. 7 Marks
   bDeduce an equation of work input to reciprocating Air compressor without considering clearance.
   How to answer

   • Start from p-V diagram without clearance: 1-2 polytropic compression
   • Integrate work W = ∫V dp = n/(n-1) p1V1[(rp)^((n-1)/n)-1]
   • Express in terms of temperatures and mass: W = m R (T2-T1)/(n-1)
   • State power for given mass flow and isothermal efficiency reference
7. 5 Marks
   aA single stage reciprocating air compressor takes in $8 m^{3}/min$ of air at 1 bar and $30^{\circ}C$ and delivers it at 6 bar. The clearance is 5% of the stroke, the expansion and compression are polytrophic with the value of n = 1.3. Calculate Temperature of delivered air
   How to answer

   • Use polytropic relation T2/T1 = (p2/p1)^((n-1)/n)
   • Substitute p1=1 bar, p2=6 bar, T1=303 K, n=1.3
   • Calculate T2 in K and °C
   • Comment on delivery temperature rise
8. 5 Marks
   bVolumetric efficiency
   How to answer

   • Recall volumetric efficiency formula eta_v = 1 + C - C*(rp)^(1/n)
   • Substitute clearance 5% and pressure ratio 6
   • Compute numerical value in %
   • Relate to actual suction volume
9. 4 Marks
   cPower absorbed by the compressor
   How to answer

   • Find effective swept volume from volumetric efficiency and intake
   • Use work formula with clearance: W = n/(n-1) p1 V_actual [(rp)^((n-1)/n)-1]
   • Convert to power in kW using 8 m³/min flow
   • State power absorbed by compressor
10. 7 Marks
    aDiscuss types of condensers.
    How to answer

    • Classify condensers: jet vs surface, parallel/counter flow
    • Describe evaporative, air-cooled and water-cooled types
    • Give neat sketches and working of each
    • Compare advantages, applications
11. 7 Marks
    bDiscuss effect of friction on flow through nozzles define nozzle efficiency.
    How to answer

    • Explain friction losses: reduced kinetic energy, increased entropy/dryness
    • Define nozzle efficiency as ratio of actual to isentropic enthalpy drop
    • Give velocity coefficient and efficiency relations
    • Show effect on h-s diagram and mass flow
12. 14 Marks
    Dry saturated steam at 6.5 bar with negligible velocity expands isentropically in a convergent divergent nozzle to 1.4 bar and dryness fraction of 0.95. Determine the final velocity of steam from the nozzle if 13% heat is lost in friction, find the % reduction in final velocity.
    How to answer

    • Get h1 for dry saturated steam at 6.5 bar, h2 for 1.4 bar x=0.95 from tables
    • Calculate isentropic velocity C = sqrt(2*(h1-h2)) with negligible inlet velocity
    • Apply 13% heat loss to get actual enthalpy drop and actual velocity
    • Compute % reduction = (C_isen - C_actual)/C_isen x 100