Register Number
SATHYABAMA UNIVERSITY
(Established under section 3 of UGC Act,1956)
Course & Branch :B.E - MECH/AUTO
Title of the Paper :Applied Thermal Engineering
Sub. Code :615402 (2006-07-08-09)
Date :27/04/2012
Max. Marks:80
Time : 3 Hours
Session :FN
Special Instructions: Use of approved refrigeration and airconditioning tables, steam table and charts are permitted
1.
PART – A
(10 x 2 = 20)
Answer All the Questions
Define the terms: Octane number and Cetane number.
2.
Discuss the scavenging in two stroke engine.
3.
Differentiate between brake thermal efficiency and indicated
thermal efficiency.
4.
Outline the purpose of Heat balance test in an IC engine.
5.
What do you mean by metastable flow?
6.
Enumerate some four applications of compressed air.
7.
In the absorption refrigeration cycles, why is the fluid in the
absorber cooled?
8.
Distinguish between heat pump and refrigerator.
9.
Moist air is passed through a cooling section where it is cooled
and dehumidified. How do the specific humidity of the air
change during this process?
10. What is dew point temperature?
PART – B
(5 x 12 = 60)
Answer All the Questions
11. (a) Discuss with suitable sketch the working of Magneto-ignition
system.
(b) Compare the relative advantages and disadvantages of four
stroke and two stroke cycle engines.
(or)
12. (a) Describe the phenomenon of detonation or knocking in SI
engine. How can it be controlled?
(b) Draw a simple carburetor and explain its function.
13. (a) Explain the method of supercharging in an I.C. engine.
(b) Describe with neat sketch the working of a multipoint fuel
injection system.
(or)
14. (a) An engine is required to develop 100 kW, the mechanical
efficiency of the engine is 86 % and the engine uses 55 kg/h of
fuel. Due to improvement in the design and operating conditions,
there is reduction in engine friction to the extent of 4.8 kW. If
the indicate thermal efficiency remains the same, determine the
saving in fuel in kg/h.
(b) Describe briefly the Morse test.
15. (a) Derive the condition for intermediate pressure of a two stage
air compressor with perfect intercooling.
(b) The dry and saturated steam at a pressure of 10.5 bar is
expanded isentropically in a nozzle to a pressure of 0.7 bar.
Determine the final velocity of the steam issuing from the nozzle,
when
(i) friction is neglected and
(ii) 10 % of the heat drop is lost friction. The initial velocity of
steam may be neglected.
(or)
16. (a) Obtain an expression for the volumetric efficiency of the
compressor.
(b) Determine the minimum number of stages required in an air
compressor which admits air at 1 bar, 270 C and delivers at 180
bar. The maximum discharge temperature at any stage is limited
to 1500 C. Consider the index for polytropic compression as
1.25 and perfect and optimum intercooling in between the stages.
Neglect the effect of clearance.
17. (a) A refrigerator uses R12 as the working fluid and operates on
an ideal vapor-compression refrigeration cycle between 0.12 and
0.7 MPa. The mass flow rate of the refrigerant is 0.05 kg/s.
Show the cycle on a T-s diagram with respect to saturation lines.
Determine
(i) the rate of heat removal from the refrigerated space and the
power input to the compressor
(ii) the rate of heat rejection to the environment, and
(iii) the COP.
(b) Explain the working of a simple ammonia-water absorption
refrigeration system with the help of neat sketch.
(or)
18. (a) Discuss the Bell-Coleman cycle with a suitable p-v and T-s
diagrams. Deduce an expression for its COP.
(b) A cold storage plant is required to store 20 tonnes of fish.
The temperature of the fish when supplied = 250 C; storage
temperature of fish required = -80 C; specific heat of fish above
freezing point = 2.93 kJ/kg K; specific heat of fish below
freezing point = 1.25 kJ/kg K; freezing point of fish = -30 C;
Latent heat of fish = 232 kJ/kg. If the cooling is achieved within
8 hours, find out:
(i) the capacity of the refrigerating plant,
(ii) Carnot cycle COP of the system;
(iii) If the actual COP is 1/3rd of the Carnot COP find out the
power required to run the plant.
19. (a) The air in a room has a dry bulb temperature of 220 C and a
wet bulb temperature of 160 C. Assuming a pressure of 100 kPa,
determine
(i) the specific humidity,
(ii) the relative humidity and
(iii) the dew point temperature.
(b) Explain with neat sketch: window air conditioner.
(or)
20. An office for seating 25 occupants is to be maintained at 240 C
DBT, 50 % RH. The outdoor conditions are 340 C DBT, 280 C
WBT. The various loads in the office are:
Solar heat gain
9.12 kW
Sensible heat gain per occupant
0.09 kW
Latent heat gain per occupant
0.105 kW
Lighting load
2.3 kW
Sensible heat load from other sources
11.63 kW
Infiltration load
14 m3/min
Assuming 40% fresh air and 60 percent of recirculated air
passing through the evaporator and the bypass factor of 0.15,
determine:
(a) Dew point temperature of the coil; and
(b) Capacity of the plant.