Punjab Technical University 2009-2nd Sem B.Tech Elements of Mechanical Engineering, B Tech ester, Regular , , - Question Paper

Time: three Hours
Maximum Marks: 60

Instruction to Candidates:
1) Section- A is Compulsory.
2) Attempt any 5 ques. from Section- B & C
3) choose at lowest 2 ques. from part - B & C

part – A [Marks 2*10=20]

a) What do you understand by Quasi-static process? How it is achieved?

b) explain concept of thermal equilibrium.

c) Write and discuss analytical expression applicable for a process and cycle.

d) elaborate non flow processes? provide suitable examples.

e) explain equivalence of different statements of 2nd legal regulations of thermodynamics.

f) What is air standard efficiency?

g) Differentiate ranging from mechanism and machine.

h) What is Poissons ratio?

i) define creep and fatigue.

j) What do you understand by throttling process?

part - B [ Marks : eight Each]

Q2) (a) describe wok. Show that work done six pdV.

(b) The pressure quantity correlation for a non flow reversible process is provided by p: (S-4V) bar, where V is in m3. If 150 kJ of work is supplied to the system, determine the final pressure and quantity. Take initial- quantity : 0.6 m3.

Q3) Air initially at 6kPa pressure 800K temperature and occupying a quantity of 0.1m3 is compressed isothermally till the quantity is halved and further it goes compression at constant pressure till the quantity is halved again. Sketch the process on p-V diagram and make computations for total work done and total heat interaction for the 2 processes. presume ideal gas behavior for air and
Take 0.005kJ/kgK .

Q4) A centrifugal pump delivers 2750kg of water per minute from initial pressure of 0.8 bar absolute to a final pressure of 3.8 bar absolute T. The suction is two m beneath and delivery is five m above the center of pump. If the suction and delivery pipes are of I five cm and 10c m diameter respectively make computations for power needed to run the pump. Density of water: 1000kg/m3.

Q5) 2 reversible heat engines E, and E1 are organizes in series ranging from a hot reservoir at temperature T of 600 K and a cold reservoir at temperature T of 300K . Engine E receives 500k J of heat from reservoir at T. Assuming that both engines have equal thermal efficiency determine:

(a) The temperature at which heat is rejected by E, and is received by engine E1.

(b) The thermal efficiency of every engine.

(c) Work done by engine E and E1.

(d) The heat rejected by engine E to cold reservoir.

part - C [ Marks : eight Each]

Q6) A reversible heat engine operates between8 75 K and 310 K and drives areversible refrigerator operating between3 10K and 255K . The engine receives 2000k J of heat and the net work output from the arrangement equals 350 kJ. Make computations for cooling effect.

Q7) (a) What is cut off ratio it affects the air standard efficiency of diesel cycle?

(b) With the help of p-V and TS diagram show that for identical maximum pressure and heat input

Q5) (a) describe velocity ratio, mechanical advantage and efficiency of a machine.

(b) The upper block of the differential pulley block has 2 pulleys of diameter 250 mm and 200 mm. What load will be lifted by this machine by the application of an effort equal to 20 N? Take efficiency of the system as 60 percent.

Q9) 2 vertical rods of steel and copper are firmly secured at their upper ends and lie at a distance of 100c m apart. every rod is of three m length and 30 mm in diameter. A horizontal rigid cross bar connects the lower ends of the rod and on it is placed a load of 40kN. Determine:

(a) Location of the load on the cross bar if it remains horizontal even after being loaded.

(b) What will be the inclination of the cross bar if the load is hung at its mid span?

Take E for steel: two x lO5 N/mm2, E for copper: one x 105 N/mm2

Earning:   Approval pending.