# CUSAT Thermal Engineering II Question Paper April 2009

BTS(C) -IV-09-0I4-K

B. Tech. Degree IV Semester Examination, April 2009

ME 403 THERMAL ENGINEERING II

(1999 Scheme)

Time: 3 Hours                                   Maximum Marks: 100

I                      (a) E:xp!ain the term “quality of steam’’. Differentiate between wet, dry saturated and super heated steam. (8)

(b) A steam power plant works between 40 bar and 0.05 bar. If the steam supplied is dry saturated and the cycle of operation is Rankine, find:

(i) Cycle efficiency

(ii) Specific steam consumptiop.

Show the Cycle on T – S Plane.                                                                                                                (12)

OR

II                    a)  What are the effects of friction on the flow through a steam nozzle? Explain with the help of h – s diagram.                                                                                                                                                                       (8)

b) Estimate the mass flow rate of stem in a nozzle with the following data :

Inlet pressure and temperature – 10 bar and 200° C;

Back pressure = 0.5 bar; Throat diameter = 12 mm.                                                                (12)

III                  a) What is the fundamental difference between the operation of impulse and reaction turbines? Explain the same with neat sketches.                                                                                                                                                 (8)

( b) Steam at 300 m/s is supplied to a single stage impulse turbine through a nozzle. The nozzle angle is 25°. The mean diameter of the blade rotor is 100 cm and it has a speed of 2000 rpm. Find suitable blade angles if there is no axial thrust.

If the blade velocity coefficient is 0.9 and the steam flow rate is 10 kg/s, find the power developed.       (12)

OR

IV                 (a)  Derive an expression for the thermal efficiency of a gas turbine plant.                                               (10) (b)  A gas turbine plant with a pressure ratio of 1 : 5 takes in air at 15° C. The maximum temperature is 600° C and develops 2200 kW. The turbine and compressor efficiencies are equal to 0.85. Taking Cp = 1 kJ/kg.K and Cv = 0.714 kJ/kg.K; determine

(i)  Actual overall efficiency of the turbine

(ii)  Mass of air circulated by the turbine.                                                                                (10)

V                    a) Draw a neat sketch of air – refrigeration system working on Bell-Coleman cycle and explain its working.        (10)

b) An air-refrigerator working on Bell-Coleman Cycle operates between pressure limits of 1.05 bar and 8.5 bar. Air is drawn from the cold chamber at 10° C, compressed and then it is cooled to 30° C before entering the expansion cylinder.

The expansion and compression follow the lane PV1.3constant. Determine the theoretical c.o.p. of the system.   (10)

OR

VI                  (a) State the properties of a good refrigerant. What are the common refrigerants used? (10)

(Turn over)

(b)       A R-12 vapour compression refrigeration system has a condensing temperature of 50° C and

evaporating temperature of 0° C. The refrigeration capacity is 7 TR.

The liquid leaving the condenser is saturated liquid and the compression is isentropic. Determine.

(i) power required to drive the compressor.

(ii) COP of the system.

Use the properties of R-12 as listed in the table below.  (10)

 Temp, j Pressure ! Hf Hg Sf Sg CC) (bar) | KJ/kg KJ/kg KJ/kg-K KJ/kg-K 50 12.199 j 84.868 206.298 0.3034 0.6792 n ‘j 3.086 ! 36.022 [187.397^ 0.1418 0.6960 Take enthalpy at tiie end of compression = 210 kJ/kg

VII                9a) Define the term by-pass’ factor used tor cooling and heating coil and derive the expression for the same.    (10)

(b)  40m3 of air per minute at 31° C DBT and 18.5° C WBT is passed over the cooling coil whose surface temperature is 4,4° C. The cooling coil capacity is 3.56 TR under the givei condition of air. Determine DBT and WBT of the air leaving the cooling coil                                                    (10)

OR

VIII              (a) Explain, with a neat diagram, fin air-conditioning system required in winter season. (10) b) A theatre of 1200 seating capacity is to be air-conditioned for Summer Condition for the following data.

Outdoor conditions 30° C DBT and 55% RH

Required conditions :   20° C DBT and 60% RH

Amount of air supplied :     0.25 m3/min/person.

Find the sensible heat, latent heat removed from the air per minute and sensible heat factor for the system. (10)

IX                  (a) What are the differences between steam power plant and gas turbine power plant

concerning their fundamental working.                                                                                                     (10)

(b) Discuss the vai ious types of ash handling system.                                                                                             (10)

OR

X                    (a)  Draw a neat diagram of a boiling water reactor and discuss its relative advantages

: and disadvantages over pressurized water reactor.                                                                                  (10)

(b)  Explain the general layout of a hydro electric power plant.                                                                                 (10)