Fluid Mechanics and Thermal Sciences - Online Test
Q1. Water (Cp = 4.18 kJ/kg.K) at 80℃ enters a counter flow heat exchanger with a mass flow rate of
0.5 kg/s. Air (Cp = 1 kJ/kg.K) enters at 30℃ with a mass flow rate of 2.09 kg/s. If the
effectiveness of the heat exchanger is 0.8, the LMTD (in ℃) is
Answer : Option C
Explaination / Solution:
Q2. A large tank with a nozzle attached contains three immiscible, inviscid fluids as shown.
Assuming that the changes is h1, h2 and h3 are negligible, the instantaneous discharge velocity is
Answer : Option A
Explaination / Solution:
No Explaination.
Q3. A refrigerator operates between 120 kPa and 800 kPa in an ideal vapor compression cycle with R134a
as the refrigerant. The refrigerant enters the compressor as saturated vapor and leaves the condenser as saturated liquid. The mass flow rate of the refrigerant is 0.2 kg/s. Properties for R-134a
are as follows: 
The rate at which heat is extracted, in kJ/s from the refrigerated space is
Answer : Option A
Explaination / Solution:
No Explaination.
Q4. A refrigerator operates between 120 kPa and 800 kPa in an ideal vapor compression cycle with R134a as the refrigerant. The refrigerant enters the compressor as saturated vapor and leaves the condenser as saturated liquid. The mass flow rate of the refrigerant is 0.2 kg/s. Properties for R-134a are as follows:
The power required for the compressor in kW is
Answer : Option C
Explaination / Solution:
No Explaination.
Q5. Air enters an adiabatic nozzle at 300 kPa, 500 K with a velocity of 10 m/s. It leaves the nozzle at
100 kPa with a velocity of 180 m/s. The inlet area is 80 cm2. The specific heat of air Cp is 1008
J/kg.K.
The exit temperature of the air is
Answer : Option C
Explaination / Solution:
Q6. Air enters an adiabatic nozzle at 300 kPa, 500 K with a velocity of 10 m/s. It leaves the nozzle at
100 kPa with a velocity of 180 m/s. The inlet area is 80 cm2. The specific heat of air Cp is 1008
J/kg.K.
The exit area of the nozzle in is
Answer : Option D
Explaination / Solution:
No Explaination.
Q7. Specific enthalpy and velocity of steam at inlet and exit of a steam turbine,
running under steady state, are as given below:
Specific enthalpy (kJ/kg) Velocity(m/s)
Inlet steam condition 3250 180
Exit steam condition 2360 5
The rate of heat loss from the turbine per kg of steam flow rate is 5 kW.
Neglecting changes in potential energy of steam, the power developed in kW by
the steam turbine per kg of steam flow rate, is
Answer : Option C
Explaination / Solution:
Q8. Water is coming out from a tap and falls vertically downwards. At the tap
opening, the stream diameter is 20mm with uniform velocity of 2 m/s.
Acceleration due to gravity is 9.81m / s2. Assuming steady, inviscid flow,
constant atmospheric pressure everywhere and neglecting curvature and surface
tension effects, the diameter is mm of the stream 0.5m below the tap is
approximately
Answer : Option B
Explaination / Solution:
No Explaination.
Q9. A steel ball of diameter 60 mm is initially in thermal equilibrium at 1030 C° in a
furnace. It is suddenly removed from the furnace and cooled in ambient air at
30 C° , with convective heat transfer coefficient h=20 W / m2 K. The thermophysical
properties of steel are: density ρ = 7800 kg / m3, conductivity k = 40 W/mK and specific heat c=600 J/kgK. The time required in seconds to cool
the steel ball in air from 1030 C° to 430 C° is
Answer : Option D
Explaination / Solution:
Q10. A flywheel connected to a punching machine has to supply energy of 400 Nm
while running at a mean angular speed of 20 radians/s. If the total fluctuation of
speed is not to exceed ±2% , the mass moment of inertia of the flywheel in kg m2− is
Answer : Option A
Explaination / Solution:
