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Register Number: 3201
Name of the Candidate:
DIPLOMA EXAMINATION - 2010
(REFRIGERATION AND AIR CONDITIONING)
(PAPER – I)
110. THERMAL ENGINEERING
May.) (Time: 3 Hours
Maximum: 100 Marks
Answer any FIVE questions (5×20=100)
Steam table, Heat and Mass Transfer data books permitted
1. A fluid system undergoes a non flow frictionless following the pressure volume relation
as p = 4.5/v +2 where p is in bar and v is in m3. During the process, the volume changes
from 0.12 m3 to 0.04m3 and the system rejected 40kj of heat. Determine the change in
internal energy and enthalpy.
2. In a steady flow system, the working fluid flowing at 5kg/sc enters the system at 6 bar
with a velocity of 300m/s. Its internal energy is 150kj/kg and specific volume is 0.4
m3/kg. the pressure, velocity, internal energy and specific volume values at exit are
1.5bar, 150m/s, 100J/Kg and 1.26m3/kg respectively. The substance loses 5kj/kg heat as
it passes through the system. Determine the power of the system.
3. State and derive the expression of clauses theorem.
4. Draw a neat diagram of vapour compression refrigeration system and explain its working.
5. A large window glass 0.5 cm thick (k=0.78 W/ m K) is exposed to warm air at 25º C,
over its inner surface, with convection coefficient of 15 W/m2 K. The outside air is at =
15º C, with convection coefficient of 50 W/m2 K. Determine the heat transfer rate and
temperature at inner and outer surface of the glass.
6. Air at 10º C and at a pressure of 100 kPa is flowing over a plate at a velocity of 3m/s. if
the plate is 30cm wide and at temperature of 60º C. Calculate the following quantities at
x = 0.3m
Boundary layer thickness
Local friction coefficient
Heat transfer from the plate
7. Derive an expression for Nusselt number for laminar film condensation on a vertical
8. A heat exchanger is required to cool 55000 kg/h alcohol from 66º C to 40º C using
40000kg/h of water entering at 5º C. Calculate exit temperature of water, area and heat
transfer rate in parallel flow arrangement
Take U = 580 W/m2 K
Cp (alcohol) = 3760J/kg.K