# WBUT Question Papers CS Mechanical Science B Tech 2nd Sem June 2009

# WBUT Question Papers CS Mechanical Science

# B Tech 2nd Sem June 2009

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GROUP – A ( Multiple Choice Type Questions )

1. Cliooje the correct alternatives for any ten of the following

I) A perpetu&i motion machine is

a) a thermodynamic machine D) a not; tnermodynamlc machine

o) a reel machine

d) n hj’pothetical machine whose operation would violate the laws cf

thermodynamics.

u) Thermodymonic system may be defined as a quantity of matier upon whicn attention in focused for study if

**a) **it is only bounded by real surface

**b) **the boundary surface is constant in shape and volume

**0) **It Is not bounded by an imaginary surface

**1) **it is bounded by either real surface or imaginary surface, irrespective c?

shape or volume.

Li) The expression JPdv may be applied for obtaining won; of

a) non-ilow reversible process ij) steady iiow reversible process

teady flow non-reversible process

**d) **steady iiow adiabatic reversible process.

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CJ/4.TECH/SEM-2/ME-201/09 4

iv) The gas constant ( R ) is equal to the i

v;} aum of two specific heats b) difference ox I wo specific heats 1

c> product cl two specific heats d) none of these. L_.

v) Carnot cycle operates between the temperature of 100C K and 500 K Then th: efficiency of the cycle is

a) 50% b) more than 50% v

c) less than 50% d) none of these,

**vi) **In a reversible cycle, the entropy of the system u) increases h’j decreases

**c) **aoes not change

**d) **tlrst Increases then decreases

• * .

s) depends on the properties of working substance, vt!) Th,; ,i.;.ent heat of vaporisation at critical point is

i’jsa than iierc b) greater than zero

**e) **v-qual to zero d) all of these,

**viii) **Toe work output of theoretical Otto cycle

increases with increase in compression ratio b! increases with increase in pressure ratio c) increases wiiL increase in adiabatic index V u) follows all of these. .

**ix) **Atmospheric pressure is

**a) **Gauge Pr. – Absolute Pr. b) Absolute Pr. – Gauge Pr.

**c] **Absolute Pr. – Vacuum Pr. d) Gauge Pr. + Vacuum Pr.

’09/06)

V^{[1]} D PV |

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xii) During the throttling process

**a) **imtru&i energy does not change

**b) **pies does not change

**c) **entropy does not change

**d) **enthalpy does not change.

GROUP -B (Short Answer Type Questions }

Answer any three of the following questions.

**b) **What is the difference between a refrigerator and a heat pump ?

Establish the relation ; COP_{HP} = COP_{R} + 1.

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<. A c-025’r.^{[2]} vessel contains 0-3 kg of steam at 2 MPr. Determine ihe quality ai l enthalphy of steam. Given t_{t} = 212*2* C, Vj — 0*001177 :n/.<g. V_{g} – 0^{–}0995 i.i ,’kg, h_{f} = 90&’5 kJ/kg, h_{Ja} = 1888-7 kJ/kg, Sj = 2-447 kJ/kg.K, S_{/8} =“3 590 k J/kg.ft

State and prove Pascal’s Law of Pressure at a point of a fluid body.

**0 **St.uc Newton laws of viscosity.

**11) **A lcirge plate moves with speed u_{0} over a stationary plate on a layer of oil. 11 t i velocity profile is that of a parabola ( as shown In figure-1 ) with oil at the pUu’‘ havaig the velocity as the plates, what Is the shear stress on tY.z .novt.ig pk t from the ell ? ^{1} ■* ^{4}

GROUP -C ( Long Answer Type Questions )

Answer any three of the following questions.

a) Prove that P_{v} – tnRT where P = pressure

V * volume of m mass of gas

T = te.aperature

i< * characteristic gas constant.

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b) Write dowa the significance of universal gas constant ( R_{m} ) and prove that

R- —s. where, M molecular weight of the substance,

M

c) When 01421 kg of a gas is heated from 27’ C to 127“ C and it u observed that the gas requires 202 kg of heat at constant pressure and 142 kJ of heat at constant volume. j^ind me adiabatic characteristic of gas constant and moieculai weight of the gas, 4 f 2 : 4 + 5

c.. a; What is a steady How process ? Write the steady flew energy equation for a single steam entering and a single steam leaving a control volume and explain the various terms in it. Calculate work done from SFEE for turbine,

b) A turbine operates under steady flow condition and receiving steam at the following conditions :

. Pressure 1-2 MPa, Temperature – 188° C, Enthalphy 2785 kJ/kg,

velocity 33 3 m/sec and elevation 3 m.

Steam leave-; the turbine at the following state :

P = 20 kPa, 7 = 100 m/sec, enthalphy – 2512 kJ/kg and heat lost to the surrounding at the rate = 0-29 kJ/sec and the rate of steam flow through the turbine is 0 42 Kg/sec. What is the power output of the turbine in kW ?

2 + 3 + 2 r B

a) Derive an expression for continuity equation for a three dimensional steady incompressible flow.

b) A jet of water from a ’25 uun diameter nozzle is directed vertically upwards, assuming that jet remains steady and neglecting any loss of energy. What will be the diameter at a point 4-5 m above nozzle, if the velocity with which jet leaves the nozzle is 12 m/sec ? i

Jet of Water

Dia = 25 mm

Nozzle |

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velocity vector for a 2D incompressible iiow £ei! is givea

■ u J. State whether the flow is eontuiuous

discontinuous.

10. a) Draw the nature of p-v and T-s plots of a Ranklne cycle (with saturated sie.-m – •

■ tarbine inlet}. •

b) A lump of steel of mass 15 kg at 557“ C is dropped in J 20 kg oi oil ai ;a‘ J. : specific heats of steel and oil are 0-5 kJ/kg-K and 3-5 kJ/kg-K respective; Calculate the entropy change of the steel, oil and the universe.

‘ c) Two bodies each of equal mass m and heat capacity C are of tempe^ta e t\ aad T_{z} (7\ > T;») respectively. The first body is used as a source of revei .<

and the second as .the sink. Show that the maximum work obtainable

from such an umaigement is m_{c} « – ^fr_{2} j . 4 + 5 r

is,, a) Prove ttoat >V”^{f} » constant in .adiabatic process and ai-:r> ■r

b) Wiiat is cyclic .neat engine ? Find the efficiency of heat engine in terms of sourc ami sink temperature. .

Which change Is more effective to increase the efficiency of the engine.

■ 5 + 3 + 1 > 3

i2. a) Daiva m eaq^rc©-,vibn of actual discharge through a venturlraeter tube,

**b) **WHie Bernoulli’s equation and describe the various terms in it.

What are the assumptions involved in derivation of Bernoulli’s equation ?

f

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0) in the ligurc, the fluid flowing In (W^-12N/m^{3}) arid the manometric fluid is Mfriar.: Red oil ( specific gravity = 0-827 ). Assuming no lo.w. compute the flew r xte.

[Assuming V |

5 + ( 3 + 2 ) -. 5

**13.**a) Draw the rheokgical cur x for a class of Newtonian and non-Nt vto.iixui fluid

j) tcate aua prove hydrostatic iaw of fluid. What is the stagna ion pressure an a ] oint in a Juki flow ?

**c) **

Determine ihe pressure difference between points A and 8. Specilc gravities cf

**I **enzene, kevoacne and cur .ire 0-88, 0-82 and 1-2 x 10′^{3} res; tcivs’y.

Kerosine |

9 cm |

Water |

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