WBUT Exam Papers CS Mechanical science
B Tech Sem 2nd 2008 .
[ Full Marks : 70
GROUP – A (M ultiple Choice Type Questions)
C i- jcse the cciTccl al ten natives for the following :
it Which Ci ci’ic follow mg is an intensive thermodyn .or.U- property ?
a) V’tivuoa b) Temperature
c) M ;s;s d) Energy.
ii) For i ;i in cv. rsible process, change in entropy is
a} greater than dQ/T b) less than dQ/T
c) zero d) equal to cQ/T,
ill) Durii;g ihrotiilng, which of the following quantity dca,. not change ?
a) Internal energy b) Entit y
c) Prussia e d) Enthalpy
Work di ine in a free expansion is .
a) Positive b) Negf.u/c
c) Zero d) Maxii.um.
A cycle v/ith constant volume heat addition and constant volume heat rejectic i is
00/B JV Jh. i- i ‘.AO-t Jl/06 . 4 ■
ii =3 dtioulli s equation deals with the conservation of
c, Energy ^ Work
C ontinuity aquation is based oh the principle of condi rvatloh of Mass b) Momentum
o; Eierjy d)
K Pitot tube is used for measuring
.4 Stau of fluid : o>
c) Density of fluid d)
Dynamic viscosity has dimensions of
a) MLT’2 b)
c) ML“1T-2 ti
GROUP -B ( Short Answer Type Qutatot* ) Answer any three of the followin’.
2, Statw the first law of thermodynamics for a closed system undergoing t tyck ^
‘ p.c .ess. . . . ‘s
3, l;..i Iain thermodynamic equilibrium.
4, ‘riic fluid flow is given by V-x2 yt + y 2z – ( 2 xyz + yz2 ) k. Show that tliis s a < ox possible steady incompressible flow. Calculate Jje velocity ar^ci acceler^ io*..
(2,1,3). . «:■ _ ■■ ‘
5, Diaw a block diagram of vapour compression re.rigeration cycle and also l: c v _c responding P-V and T-S plots.
o. >tve B – moulli’s equation form first principles, stating tl e assumptions.
;. .1 plain PM..1-1 and PMM-2.
GROUP-C (Loaf Answer Type Questions)
Answer any three of the following, 3 x 15 » *5
- a) Which is *t more effective way of increasing the eflucienc y of a Carnot engine to increase source temperatue ( T y ), keeping sin’: temperature ( T% ) constant or
to decrease T2 keeping Tr constant.
b) State Clausius inequality.
c) A mass of m kg of liquid ( specific heat * Cp) at a temperature T j is mixed with an equai m^ss of the same liquid at a temperature T2 ( Tj > ) and the system is thermally insulated. Show that the entropy charge of tfcw vaJverse is given by
and prove that this is necessarily positive. 3 + 2 + 10
- a) Derive the expression for efficiency of an Otto cycles and show the process on
p-V and T-s planes.
b) For the same compression ratio, explain why the efficlenc/ of Otto cycle is greater than that of Diesel cycle.
c) In a diesel engine the’compression ratio is 13 : 1 and fuel is cut off at 8% of f h stroke. Find the air standard efficiency of the engine. Take y for ir « 1.4
. . 5 + 3 + 2 + 5
- a) A gas occupies 0.024 m3 at 700 kPa and 95’C. It is expanded in the non-flow
process according to the law pv 12 = constant to a pressure of 70 kPa after which it is heated at a constant pressure back to its original temperature. Sketch the process on the p-V and T-s diagrams and calculate for the whole process the work done and the heat transferred.’Taka Cp =1.047 and C u – 0.775 kJ/kg K for the gas.
b) A rigici cioscd tank of volume 3m3 contains 5 kg of wet * t un at a pressure o) 200 kPa The tank is heated until the steam becomet dry saturated. Determine the pressure and the heat transfer to the tank. 8 t 7
- it) Write the steady flow energy equation for a single steam entering and su^te
&t~aialeaving a control y$lpmetandexpte‘.a toe vart<m terms.
» ) ivt the inlet to a nozzle, ^e, enthalpy of.the iluid pacing is 3000 kJ/’tg .uva velocity is 60 m/s. At the exit, the eii&ialpy is 2762 teJ/kg. The nczzl it horiKontal and there is n^ligible heat loss,
I) Find tlie velocity at the nozzle exit * ‘
ii) The inlet area is 0.1 m 2 £ind the specific volume tit inle H 187 l|>\ Find the mass flow rate. ‘
ill) If the specific volume at the nozzle exit is 0.498 m 3/kg, find s.- * e –it ;u &; of the nozzle. , ^
- u) Derive Euler’s equation of motion alon^a ttreainliae,
b) A venturimeter has inlet and throat diameters of 300 mm and 150 nw . V ‘*•. flows tlirough it at the rate of O.Q65m 3/@ and the differential gauge is defk : . by 1.2 m. The specific gravity of the m&iiometric liquid is 1.6. De terrain dbu; coefficient of discharge of the venturimeter.
o) A Jet of water from a 25 mm diameter nozzle is directed vertically upw r is Assuming that the jet remains circular and neglecting any loss of energy, w.u will be the diameter of the jet at a point 4.5 m above the nozzle, if the jet U a /e &e nozzle with a velocity of 12 m/s ? £-r j- ‘
- a) A circular disk of diameter d is slowvy ruteaed in a liquid of viscosity ^ at a n:a-
distance h from a fixed surface. Derive an expression for the iorqu necessary to maintain an angular velocity o>,
b) Distinguish between the follow :
laminar and turbulent flow
it) compressible and incompressible fluid ii) static pressure and stagnation pressure
ivj viscous and inviscid fluid. 7 + 3
14, Write short notes on any three of the following : 3×5
Pitot tube , *
L) Orifice meter
Point function and path function a. Streamline, streakline and pathline.