# State Engineering Service Mains Exam-2016

Paper II

1. (A) Final the heat transferred to a gas of 2 kg when it is heated mom 20 °C to 100 °C . The    specific heat of gas at constant  volume is given lay                                                 C = (0.5 + 0.005 T) kJ kg °C                                                                                               also find out the mean value of specific heat.

(B) A stone of mass 10 kg and tank containing 100 kg water are initially at same temperature. A stone above 100 m falls into the water. Considering the stone and water as a system, determine AU, APE, AKE \$ and W, When

(i)      the stone is about to enter the water

(ii)     the stone has come to rest in the tank.

(C)  In ii flow ink river a body is immersed at a depth of 3.5 in and the pressure on the upstream face of the body is found to be 35.30 kN/m² find the velocity of the river at that depth.

(D) If the velocity distribution in the boundary layer is given by determine the displacement thickness. the momentum thickness and the energy thickness.

(E) The temperature distribution across a wall 1 m thick at a certain instant of time is given by                                                                                                                        T(x)= a + bx + cx²

while a = 900 °C, b = -300 °C/m and C = -50 °C/m2.

A uniform heat generation q = 1000 W/m3 is present in the wall area of 10 m2 having the property K = 40 W/m K. Determine the rate of heat transfer entering the wall (x — 0) and leaving the wall (s — 1 m). Also calculate the rate of change of energy storage in wall.

(F) A system for heating water from an inlet temperature of 20 °C to an outlet temperature of 60 °C involves passing the water through a thick walled tube having inner and outer diameters of 20 and 40 mm. The outer surface of the tube is well  insulated  and electrical  heating within the wall provides for a uniform generation of heat of q = 10 W /m³. For a water mass flow rate of m = 0.1 kg/s, how long must the tube be to achieve the desired outlet temperature ?

Take Cp  = 4179 J/kg-    K.

(G) An engine working on otto-cycle has a volume of 0.5 m° pressure I bar and temperature of 27 °C at the beginning of the compression stroke. At the end of the compression stroke, the pressure is 10 bar, 210 kf of heat is added during constant volume heating process. Calculate the pressures, temperatures and volumes at salient points in the cycle.

(H) For a vapour compression refrigeration system, sketch p-h diagram on T-S diagram and express the coefficient of performance of the cycle in terms of enthalpies.

(I) Explain any three geometry statements and three motion statements in APT language.

(J) Explain the general application characteristics in an environment of material handling by robots.

2. (A) Three pipes of same length L, diameter D and friction factor f are connected in parallel. Determine the diameter of the pipe of length L and friction factor f which will carry the same discharge for’the same head

loss. Use the formula B= F x L x V² / 2gD

(B) Oil with a free stream velocity of 2 m/sec flows over a thin plate 2 m wide and 2 m long. Calculate the boundary layer thickness and the shear stress at the trailing end point and determine the total surface resistance of the plate. Take specific gravity as 0.86 and kinematic viscosity as l0-5 m2/sec.

3. (A) 0.5 kg of air, initially at 25 °C is heated at constant  pressure  until  the volume is doubled and is then  heated  at  constant  volume  until  the  pressure is doubled. For the  total  path,  find  the  work  transfer,  heat transfer and change in entropy.

(B) A plane wall is a composite of two materials  A & B. The wall of material  A  has uniform heat generation q = 1.5 x 106 W/m3, KA = 75 W/m K and thickness LA = 50 mm. The wall material  B has no generation with KB = 150 W/m-     K and  thickness LB = 20 mm. The inner surface of material  A is well insulated,  while the outer surface of material  B is cooled  by water  stream with T = 30 °C and h = 1000 W/m-K. Determine the temperature T0 of the insulated surface and the temperature of T2 of the cooled surface.

4. (A) Two large parallel planes having emissivities of 0.3 and 0.5 are maintained at 800 °C and 350 °C respectively. A radiation shield having an emissivity of 0.05 on both sides is placed between the two planes, calculate
(i)          heat transfer per m2 without shield

(ii)        the temperature of shield and                                                                                (iii)   heat transfer per m2 with shield.

(B) A vapour compression cycle with ammonia as refrigerant works between the limits of saturated suction temp. of —20 °C and saturated condensing temp. of 30 °C. lt is a simple saturated cycle and compression is isentropic, determine the work of compression per kg of ammonia. Compare the same if ammonia vapours leaving the evaporator at —20 °C is absorbed by water so that the mass concentration in the solution reaches about 40% and its solution is pumped to the condenser pressure.

Assume  specific  volume  of solution  to  be 0.001161  m3/kg.  Assume

h2 1420 kJ/kg and h3 = 1668 kJ/kg. (p-h chart values)

5. (A) During the test on 4-cylinder, 4-stroke petrol engine, the following readings are taken :

Diameter of the cylinder  80 mm, stroke of the piston = 100 mm. Speed of the engine 3000 rpm, Load on the hydraulic dynamometer 160 N, Dynamometer constant 20420 when speed is in rpm. Fuel consumption kg/hr. Cp of the fuel used 43000 kJ/kg. The temperature and pressure of the charge at the end of suction  stroke =  15 °C and  1  bar. ratio 13 1.

For  the  determination  of  the  mechanical  efficiency  of  the  engine, Morse test was carried out by shooting the spark  plugs  of  each cylinder successively without change of speed.  The  corresponding BP’s  of  the  engine  are  16.5,   16,  5.6  and   17.6  kW  respectively. Determine :

(i) The  BP,    Brake   mean  effective   pressure  and   Brake   thermal efficiency of the engine.(ii) Also find the mechanical efficiency and volumetric efficiency of the engine at suction condition.

(B) A gas turbine plant operates on Brayton cycle between temp. limit of 1100 °K and 310 °K. Calculate the maximum work done per kg of air (kJ/kg) and corresponding cycle efficiency.

6.(A) Kaplan turbine  develops  24647.6  kW  power at an average head of 39 meters. Assuming speed ratio of 2, flow ratio of 0.6, diameter of the boss equal to 0.35 times the diameter of the runner and an overall efficiency of 90%. Calculate the diameter, speed and specific speed of the turbine.

(B)    A simple turbo-jet unit operates with a turbine inlet temperature of 1100 K, a pressure ratio is 4 : 1 and air man flow of 22.7 kg/sec under design conditions. The following component efficiencies may be assumed :

 Isentropic compressor efficiency — 0.85 Isentropic turbine efficiency — 0.9 Propelling nozzle efficiency — 0.95 Transmission efficiency — 0.99 Combustion chamber pressure loss — 0.21

Calculate the design thrust and specific fuel consumption  when the unit is stationary at sea-level  where the ambient  condition  may  be taken as 1.013 bar and 288 K.
Cpa =   1.0035 , Yair = 1.4
Cpg =   1.147 , Ygas = 1.33
L.C.V. of the fuel = 43125 KJ/Kg. K.

7. (A) Explain the working of Raster Scan (Digital TO) as a graphics terminals for CAD.

(B)  Explain in the relationship of adoptive control machining  in computer aided Manufacturing.

(C) The work  table of a positioning system  is driven by a  lead screw having pitch = 6 mm. The lead screws  is connected to the output shaft of  stopper motor  through a gearbox  w hose ratio is 8 1. The stepper  motor   has 72 step angles. The table must wove a distance of 240 min morn its present position at a linear velocity of’ 540 mm/min. Determine the no. of pulses required to move the table and required motor speed.