# 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

05 Mass

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“^{1}T^{-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-x^{2} yt + y ^{2}z – ( 2 xyz + yz^{2} ) 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.

|tt-2S’LJ33(til

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 T_{2} keeping T_{r} constant.

b) State Clausius inequality.

c) A mass of m kg of liquid ( specific heat * C_{p}) at a temperature T j is mixed with an equai m^ss of the same liquid at a temperature T_{2} ( 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 m
^{3}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 C_{p} =1.047 and C _{u} – 0.775 kJ/kg K for the gas.

b) A rigici cioscd tank of volume 3m^{3} 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$lpme_{t}andexpte‘.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.

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