Manipal University 2007-2nd Sem B.E Industrial Production & Engineering I(MANUFACTURING ENGG.) (MAKE-UP) - Question Paper

III SEM. B.E. (MANUFACTURING ENGG.) DEGREE (MAKE-UP) exam
SUBJECT : ENGINEERING THERMODYNAMICS (MME-221 )

Reg.No.

MANIPAL INSTITUTE OF TECHNOLOGY

(A Constituent Institute of MAHE -Deemed University)

Manipal - 576 104

III SEM. B.E. (MANUFACTURING ENGG.) DEGREE (MAKE-UP) EXAMINATION

JAN. 2007

SUBJECT : ENGINEERING THERMODYNAMICS (MME-221 ) REVISED CREDIT SYSTEM (05/01/2007)

Time: 3 Hours.    MAX.MARKS: 50

Instructions to Candidates:

Answer ANY FIVE FULL questions.

Use of Thermodynamic data hand book/steam tables is permitted.

IA)    State the first law of Thermodynamics applied to a

i)    Cycle

ii)    Non flow process

iii)    Flow process.

IB)    Prove that entropy is a property of a system.

IC)    The heat capacity at constant pressure of a certain system is a function of temperature only and may be expressed as

41.87

^Cp (t +100)

Where t is the temperature of the system in C. The system is heated while it is maintained at a pressure of 1 atmosphere until its volume

3    3

increases from 2000 cm³ to 2400 cm³ and its temperature increases from 0C to 100C. Find

i)    The magnitude of the heat interaction.

ii)    Change in internal energy of the system.

State and prove claussius Inequality.

A heat engine operating between two reservoirs at 1000 K and 300 K is used to drive a heat pump which extracts heat from the reservoir at 300 K at a rate twice that at which the engine rejects heat to it. If the efficiency of the engine is 40% of the maximum possible and the C.O.P. of the heat pump is 50% of the maximum possible, find

i)    Temperature of the reservoir to which the heat pump rejects heat.

ii)    Rate of heat rejection from the heat pump if the rate of heat supply to the heat engine is 50 KW.    (07)

3A) Obtain an expression for the minimum work of compression for a two

stage reciprocating air compressor with perfect intercooler.    (04)

3B) At the inlet to a certain nozzle, the enthalpy of the fluid is 3000 KJ/Kg, velocity is 60 m/s. At the discharge end, the enthalpy is 2762 KJ/Kg.

The nozzle is horizontal and there is negligible heat loss from it. Find

i)    The velocity at exit of the nozzle.

ii)    The mass flow rate if the inlet area is 0.1 m² and the specific volume at inlet is 0.187 m³/Kg.

iii)    The exit area of the nozzle if the specific volume at the nozzle exit is 0.498 m³/Kg.    (06)

4A) With usual notations, obtain an expression for the air standard efficiency of a diesel cycle in terms of compression ratio, cut-off ratio and ratio of specific heats. State the assumptions made for deriving this expression.    (05)

4B) In an air standard Otto cycle, the compression ratio is 7. The compression begins at 35C, 0.1 MPa. The maximum temperature of the cycle is 1100C. Find

i)    The temperature and pressure at the cardinal points of the cycle.

ii)    The heat supplied per Kg of air.

iii)    The work done per Kg of air.

iv)    The cycle efficiency.

v)    The mean effective pressure of the cycle.    (05)

5A) Critically evaluate the merits and demerits of the different refrigerants

used in vapour compression refrigeration system.    (03)

5B) A Freon -12 refrigerator producing a cooling effect of 20 KW operates on a simple vapour compression cycle with pressure limits of 1.509 bar and 9.607 bar. The vapour leaves the evaporator dry saturated and there is no under cooling. Determine the power required by the machine. If the compressor operates at 3000 rpm and has a clearance volume of 3% of stroke volume, determine the piston displacement of the compressor. For compressor assume that the compressor follows the law pv¹³ = constant. Find also the bore & stroke of the compressor if the bore to stroke ratio is 0.95. Show the process on a (07) T-S diagram.

6A) Derive expressions for temperature distribution, under one dimensional steady state heat conduction for the following systems.

i) Composite wall ii) Sphere.    (06)

6B) A 150 m steel steam pipe has inside diameter of 120mm and outside diameter of 160mm. It is insulated at the outside with asbestos. The steam temperature is 150C and the air temperature is 20C. The heat transfer coefficient for steam is 100 W/m²C and for air is 30 W/m²C.

The thermal conductivity of steel is 42 W/mC & that of asbestos is 0.8 W/mC. If the heat loss is to be limited to 2.1 KW/m^2, find the thickness of the asbestos insulation required.    ⁽⁰⁴⁾

(MME-221)    Page 2 of 2

Attachment: manipal-university-2007-b-e-industrial-production--amp--engineering-3442-1.pdf

Earning:   Approval pending.