Subject Code: 3110006
GUJARAT TECHNOLOGICAL UNIVERSITY
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BE - SEMESTER- I & II (NEW) EXAMINATION — WINTER 2019
Subject Name: Basic Mechanical Engineering
Time: 10:30 AM TO 01:00 PM
Date: 03/01/2020
Total Marks: 70
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Instructions:
- Attempt all questions.
- Make suitable assumptions wherever necessary.
- Figures to the right indicate full marks.
- Use of steam tables is allowable
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Q.1
(a) Define prime movers. Write any Four examples of the prime movers. [03]
(b) Define the terms: Hardness, Toughness, Ductility, Elasticity [04]
(c) List the non-convectional sources of energy. Prepare a short note on solar energy. [07]
Q.2
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(a) Distinguish between coupling and clutch. [03]
(b) Describe briefly using neat diagrams the types of belt drives. [04]
(c) Explain with neat sketch the Vapor Compression Refrigeration system. Also draw p-h and T-s diagram for the same. [07]
OR
(c) Classify Air Compressors. Explain construction and working of centrifugal pump with sketch. [07]
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Q.3
(a) Prove that the difference between two specific heats of gases is equal to its characteristic gas constant. [03]
(b) Differentiate between gas constant and Universal gas constant. [04]
(c) One kg of gas at a pressure of 100 kPa and temperature of 17 °C is compressed isothermally in a piston-cylinder arrangement to final pressure of 2500 kPa. The characteristic gas equation is given by the relation pV = 260 T per kg where T is in Kelvin. Find out (1) Final Volume (2) Compression Ratio (3) Change in enthalpy (4) Work done on the gas. [07]
OR
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Q.3 (a) One kg gas is compressed adiabatically by following the law pV? = C from initial temperature of 290K. The initial pressure of gas is 1 bar. The initial and final volumes of gas are 0.50 m3 and 0.05 m3 respectively. Find the final temperature and pressure of gas. Assume ?=1.4 [03]
(b) Write the uses of “Steam Tables” [04]
(c) Find the internal energy of 1 kg of steam at a pressure of 15 bar when steam is (1) Super-heated at a temperature of 400 °C and (2) Wet with dryness fraction of 0.9. Take specific heat of superheated steam as 2.1 kJ/kg-K. [07]
Q.4
(a) A diesel engine works on Diesel cycle with a compression ratio of 15 and cut off ratio of 1.75. Calculate the air standard efficiency. Assume ?= 1.4. [03]
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(b) Derive the equation for air standard efficiency of Otto cycle. [04]
(c) The following readings were observed during a test on Two Stroke Single Cylinder Diesel engine: [07]
Bore = 22cm
Stroke = 28cm
Speed = 350 rpm
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Effective brake drum diameter = 100 cm
Mean Effective Pressure = 3bar
Fuel consumption = 4kg/h
Calorific value of fuel = 43MJ/kg
Calculate: (1) Indicated Power (2) Brake Power (3) Mechanical Efficiency (4) Brake thermal Efficiency
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OR
Q.4 (a) Classify I.C. Engines. [03]
(b) Determine the brake thermal efficiency of an engine with following data: [04]
Brake Power = 80 kW
Fuel consumption rate = 20 kg/hour
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Calorific value of the fuel = 43 MJ/kg
(c) Discuss the construction and working of four stroke Petrol engines. [07]
Q.5
(a) Define the terms ‘Refrigeration’, “Ton of Refrigeration” and “Coefficient of Performance” [03]
(b) What is boiler? Compare fire tube boiler with water tube boiler. [04]
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(c) Explain with neat sketch, the construction and working of (1) Fusible plug (2) Air preheater. [07]
OR
Q.5 (a) Differentiate between reciprocating compressor and rotary compressor. [03]
(b) Differentiate between boiler mountings and accessories. [04]
(c) Discuss the construction details and working of Cochran boiler with neat sketch. [07]
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