Aryabhatta knowledge university
Sem. iv 2013 Time 3hr Full marks: 70
Thermodynamics
Attempt any five question in which question no 1 is
compulsory
1.
Choose the correct answer (any seven):
(a)
In case of free expansion between state -1 and
state -2 ,which of the following is correct considering no heat interaction?
(i)
U1 =U2
(ii)
W1-2 =0
(iii)
Q1-2 =0
(iv)
All of the above
(b)
The latent heat of vaporisation with increase in
pressure of water
(i)
Increases
(ii)
Remains constant
(iii)
Decreses
(iv)
None of the above
(c)
As differentials heat and work would be
described mathematically as
(i)
Inexact
(ii)
Exact
(iii)
Discontinuity
(iv)
Point function
(d)
Heat is being supplied to air in a cylinder
fitted with a frictionless piston held by a constant weight, the process is
(i)
Isochoric
(ii)
Isobaric
(iii)
Adiabatic
(iv)
Isothermal
(e)
Expansion of hot gases in an IC engine can be
approximated to an
(i)
Isochoric
(ii)
Isobaric
(iii)
Adiabatic
(iv)
Isothermal
(f)
A refrigerator and a heat pump operate between
same temperature limits. If the COP of refrigerator is 4, then the COP of heat
pump is
(i)
3
(ii)
4
(iii)
4.4
(iv)
5
(g)
A relation of vapour to enthalpy of
vapourisation is expressed in
(i)
van der walls equation
(ii)
Maxwell equation
(iii)
Carrier equation
(iv)
Clausius-clapeyron equation
(h)
For same maximum pressure and temperature among
Otto , diesel and dual cycles
(i)
diesel cycle is most efficient
(ii)
Otto
cycle is most efficient
(iii)
dual
cycle is most efficient
(iv)
None of the above
(i)
Thermal efficiency of rankine cycle can be
improved by steam
(i)
Reheating
(ii)
super
heating
(iii)
Regeneration
(iv) None
of the above
(j)
The process of removing moisture from air at
constant dry bulb temperature is known as
(i)
Sensible heating
(ii)
Sensible cooling
(iii)
Dehumification
(iv)
Humidification
2.
(a) define internal energy. Show that internal
energy is a property of a system.
(b) a cylinder contains 0.12 m3
of air at 1 bar and 90°c .It is compressed to 0.03 m3 .The final
pressure being 6 bar .Find the index of compression, increase in internal
energy and heat transferred. Take R= 0.287 KJ/kg-K and Cv=0.717KJ/kg-K
3.
(a) prove
the Kelvin planck and Clausius statement of the second law of thermodynamics
are equivalent to each other.
(b)
A reversed Carnot Cycle operating as a refrigerator has a capacity of
100 KJ/s while operating between
temperature limits of -20°c and 35°C. Determine (i) power input and (ii) COP .
What would be its efficiency if it runs as an engine?
4.
(a) state
and prove Clausius inequality.
(b)
During isothermal heat addition process of a Carnot cycle, 800 KJ heat
is added to the working fluid from a source of 527°c. Determine (i) change in entropy of the working fluid ,
(ii) change in entropy of the source and (iii)
total entropy change during the process.
5.
(a)
define the following:
(i)
Pure substance
(ii)
Saturation point
(iii)
Triple point and critical point
(b) A vessel of volume 0.04m3
contains a mixture of saturated water and saturated steam at temp of 250°C. The mass of liquid is 9 kg . Find
the enthalpy and the internal energy .
6.
In an air -standard dual cycle, the pressure and
temperature at beginning of compression are 1 bar and 57°C respectively. The
heat supplied in the cycle is 1250 KJ/kg, two third of this being added at
constant volume and rest at constant pressure. If the compression ratio is 16,
determine the air-standard efficiency.
7.
(a) give limitation of carnot vapour power cycle
and explain how Rankine cycle helps in overcoming them.
(b) A stem power plant running on Rankine
cycle has steam entering HP turbine at 20MPa, 500°c and leaving LP turbine at
90% dryness. Considering condenser pressure of 0.005 MPa and reheating
occurring up to the temperature of 500°C , determine the thermal efficiency of the cycle.
8.
(a) what do you mean by dry bulb and wet bulb
temperatures? When do d.b.t. ,w.b.t.and d.p.t. become equal?
(b) 10 m3 /min of air at 1 atm
and 20°C with 90% RH is mixed with 20 m3
/min of air at 1 atm and 40°C with 20% Rh. Calculate the resulting
state of mixture.
9.
(a)
Explain Maxwelll relation in thermodynamics .
(b) A gaseous mixture consists of 1 kg of
oxygen and 2 Kg of nitrogen at a pressure of 150 Kpa and a temperature of 20°C
. Determine the change in internal energy and enthalpy of the mixture when the
mixture is heated to a temperature of 100°C (i) at constant volume and (ii)
constant pressure.
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