Mechanical Engineering Answers

Four kg of water is placed in an enclosed volume of 1m^3. Heat is added until the temperature is 150∘C. Find

( a) the pressure,

(b )the mass of vapor, and

(c) the volume of the vapor.

During the execution of a reversible nonflow process, the work done is -165 kJ. If the initial volume is 0.845 cu.m. and the pressure varies as p = -730V + 690 kPaa, where V is in cu.m.

The exhaust gases on leaving cylinders were passed through an exhaust gas calorimeter and raised the temperatures of 215kg of water from 15°c to 61°c.determin break thermo efficiency

A piston of 46 mm diam moves concentrically in a cylinder of 50 mm diam. The cylinder is filled with water and when the piston moves into the cylinder the water flows through the gap surrounding the piston. If the velocity of the piston is 75 mm/s relative to the cylinder, what is the velocity of the flow through the gap.

1. A pipe 0.093 m² in area, carries a discharge of 0.283 m² / s of water. If it enlarges suddenly to 0.372 m² and if the pressure in the smaller section is 4.8 kN / m², find (a) the head lost, (b) the pressure in the larger part, (c) the power needed to force the water through the enlargement.

2.Water is siphoned out of a reservoir using a bent pipe (DEF) that is 24 m long and 25 mm in diameter. The end D is below the water surface and 150 mm above the base of the reservoir. The length DE is vertical and 9 m long and EF is 15 m long and the free end F is 1.5 m below the base of the reservoir. Assuming a barometric pressure of 10.3 m of water and that siphon action at E ceases when the absolute pressure is 1.8 m of water, determine the limiting velocity of water in the pipe and the depth of water in the tank when siphon action ceases. Assume that the loss of head in friction per metre is 0.5 v² / 2g where v = velocity in the pipe. 

1. A piston of 46 mm diam moves concentrically in a cylinder of 50 mm diam. The cylinder is filled with water and when the piston moves into the cylinder the water flows through the gap surrounding the piston. If the velocity of the piston is 75 mm/s relative to the cylinder, what is the velocity of the flow through the gap.

2. A 100 mm diam pipe carrying 1.8 m² / min of water suddenly enlarges to 150 mm diam. Find (a) the loss of head due to the sudden enlargement, (b) the difference in pressure in kN / m² in the two pipes taken between points just outside the area of disturbance due to change of section. The axis of the pipe is horizontal.

3.Water flows down a straight inclined pipe. At a point A, 45 m above datum, the section of the pipe suddenly doubles in area. The pressure in the smaller pipe at A is 860 kN / m² and the velocity of flow in the larger pipe is 2.4 m / s. Find the pressure in kN / m² at a point B which is 2.5 m above datum.

With increasing emphasis on energy conservation, there is an obvious move to construct buildings using methods and materials that do not absorb much heat from external sources. Discuss some of the developments in this field and the new ways/materials being employed for this purpose.

A single cylinder four stroke internal combustion engine develops 30 kW at 300 rev/min. The

turning-moment diagram for the expansion and compression strokes may be taken as two isosceles

triangles, on bases 0 to π and 3π to 4π radians respectively, and the net work done during the

exhaust and inlet strokes is zero. The work done during compression is negative and is one quarter

of that during expansion. Sketch the turning moment diagram for one cycle and find the maximum

value of the turning moment during expansion. If the load remains constant, mark on the diagram

the points of maximum and minimum speed. Also find the moment of inertia, in kg m 2

, of a flywheel

to keep the speed fluctuation within ±1.5 per cent of the mean speed.

. A machine press is worked by an electric motor, delivering 2.25 kW continuously. At the

commencement of an operation, a flywheel of moment of inertia 50 kg m 2 on the machine is

rotating at 250 rpm. The pressing operation requires 4.75 kJ of energy and occupies 0.75 second.

Find the maximum number of pressing that can be made in 1 hour and the reduction in speed of the

flywheel after each pressing. Neglect friction losses.

A shaft fitted with a flywheel rotates at 250 rpm and drives a machine the resisting torque of

which varies in a cyclic manner over a period of three revolutions. The torque rises from 675 Nm to

2700 Nm in a uniform manner during 0.5 revolution and remains constant for 1 revolution, the cycle

being then repeated. If the driving torque applied to the shaft is constant and the flywheel has a

mass of 450 kg and a radius of gyration of 0.6 m, find the power necessary to drive the machine and

the percentage fluctuation of speed.