Q3.In a condenser of a power plant, the steam condenses at a temperature of 60o C .
The cooling water enters at 30o C and leaves at 45o C . The logarithmic mean
temperature difference (LMTD) of the condenser is
Answer : Option BExplaination / Solution:
Flow configuration in condenser as shown below.
Answer : Option DExplaination / Solution:
Heat and work are path functions.
Since δQ and δW are dependent on path followed between two given end states
of a thermodynamic process undergone by system.
Q5.A pipe of 25mm outer diameter carries steam. The heat transfer coefficient
between the cylinder and surroundings is 5W /m2K . It is proposed to reduce the
heat loss from the pipe by adding insulation having a thermal conductivity of
0.05W/mK. Which one of the following statements is TRUE?
Answer : Option CExplaination / Solution: No Explaination.
Q6.The contents of a well-insulated tank are heated by a resistor of 23Ω in which
10A current is flowing. Consider the tank along with its contents as a
thermodynamic system. The work done by the system and the heat transfer to
the system are positive. The rates of heat (Q), work (W) and change in internal
energy (∆U) during the process in kW are
Q7.Figure shows the schematic for the measurement of velocity of air (density =
1.2kg /m3 ) through a constant–area duct using a pitot tube and a water-tube
manometer. The differential head of water (density = 1000 kg /m3) in the two
columns of the manometer is 10mm. Take acceleration due to gravity as 9.8m / s2. The velocity of air in m/s is
Answer : Option CExplaination / Solution:
From Bernoulli’s equation
Q8.The values of enthalpy of steam at the inlet and outlet of a steam turbine in a
Rankine cycle are 2800kJ/kg and 1800kJ/kg respectively. Neglecting pump work,
the specific steam consumption in kg/kW-hour is
Answer : Option AExplaination / Solution:
Work done by the turbine
W = 2800 – 1800 = 1000 kJ/kg = 1000 kW-s/kg
Specific fuel consumption = (1/1000)×3600 = 3.6 kg / kw-hr
Q9.The ratios of the laminar hydrodynamic boundary layer thickness to thermal
boundary layer thickness of flows of two fluids P and Q on a flat plate are 1/2
and
2 respectively. The Reynolds number based on the plate length for both the flows
is 104. The Prandtl and Nusselt numbers for P are 1/8
and 35 respectively. The
Prandtl and Nusselt numbers for Q are respectively