Hall Ticket No:
Question Paper Code: A3313
VARDHAMAN COLLEGE OF ENGINEERING
(AUTONOMOUS) B. Tech IV Semester Regular/Supplementary Examinations, May 2018
(Regulations: VCE-R15) BASIC MECHANICAL ENGINEERING
(Electrical and Electronics Engineering) Date: 18 May, 2018 FN
Time: 3 hours
Max Marks: 75
Answer ONE question from each Unit
All Questions Carry Equal Marks
Unit I
1.
State first law of thermodynamics applicable to the closed system undergoing a cycle and a change of state. Also mention the limitations of first law.
7M
In a system 80KJ of heat is supplied from state 1 to state 2 by a constant volume process. The internal energy at state 1 is 90KJ. The system rejects 95KJ of heat from state 2 to state 3 by constant pressure process and 30KJ of work is done on it. The system is brought back from state 3 to state 1 by a reversible adiabatic process. Calculate the adiabatic work and the values of internal energy at state 2 and state 3.
8M
2.
Sketch the Carnot cycle on P-V and T-S diagrams and derive an expression for its efficiency in terms of source and sink temperatures.
8M
A fluid expands in a frictionless closed system from a volume of 0.1m3 to 0.16m3 in such a manner that the pressure is given by where C is constant. The initial pressure is 300kpa. Calculate the amount of work done.
7M
Unit II
3.
Explain the importance of vapour pressure.
3M
Calculate specific weight, mass density, specific volume and specific gravity of a liquid having a volume of 4m3 and weighing 29.43kN. Assume missing data suitably.
12M
4.
Derive hydrostatic law of pressure.
7M
The right limb of a simple U-tube manometer containing mercury is open to the atmosphere while the left limb is connected to a pipe in which a fluid of specific gravity 0.9 is flowing. The centre of the pipe is 12cm below the level of mercury in the right limb. Find the pressure of fluid in the pipe if the difference of mercury level in the two limbs is 20 cm.
8M
Unit III
5.
What is the need of draft tube?
3M
A reaction turbine works at 450rpm under a head of 120m. Its diameter at inlet is 1.2m and the flow area is 0.4m2. The angle made by the absolute and relative velocities at inlet is 200 and 600 respectively with the tangential velocity. Determine:
i. The discharge through the turbine
ii. Power developed
iii. Efficiency
Assume radial discharge at outlet.
12M
6.
Differentiate between reaction and impulse turbine.
5M
An inward flow reaction turbine running at 500rpm has an external diameter is 700mm and a width of 180mm. If the guide vanes are at 200 to the wheel tangent and the absolute velocity of water at inlet is 25m/s, find:
i. Discharge through the turbine
ii. Inlet vane angle
10M
Cont…2
2
Unit IV
7.
Define specific speed of a centrifugal pump and derive an expression for the same with usual notations.
7M
A centrifugal pump delivers water against a net head of 14.5m and a design speed of 1000rpm. The vanes are curved back to an angle of 300 with the periphery. The impeller diameter is 300mm and outlet width 50mm. Determine the discharge of the pump if manometric efficiency is 95%.
8M
8.
Explain with a neat sketch the working of a reciprocating pump.
8M
A single acting reciprocating pump running at 50rpm delivers 0.01m3/s of water. The diameter of the piston is 200mm and stroke length 400mm. Determine:
i. The theoretical discharge of the pump
ii. Co-efficient of discharge and
iii. Slip and the percentage slip of the pump
7M
Unit V
9.
Derive an expression for temperature distribution and heat transfer in a sphere under one dimensional steady state condition using general heat conduction equation.
8M
A steam pipe of 100mm outer diameter is covered with two layers of insulating material each 25mm thick, one having thermal conductivity thrice the other. Determine the percentage increase in heat loss when the better insulating material is inside than when it is outside.
7M
10.
What is the physical significance of critical radius of insulation? Derive an expression for the same for a sphere.
6M
Steam flows through a pipe of internal diameter. 150mm and wall thickness 10mm. The pipe is insulated with two layers, the inner layer of thickness 25mm with a material having thermal conductivity 0.233W/m-k and the outer layer has thickness of 40mm and the material has a conductivity of 0.1163W/m-k, pipe material has thermal conductivity of 46.51W/m-k. Determine the heat loss through the pipe per meter length if the inner wall temperature is 2000C and the outer surface temperature is 500C. Also find the temperature at the surface between insulations.
9M