Question

A grey body is one whose absorptivity |
1. does not vary with temperature and wavelength of the incident ray 2. is equal to its emissivity 3. varies with temperature 4. varies with wavelength of the incident ray |

A liquid is in equilibrium with its vapor at its boiling point. On an average, the molecules in the liquid and gaseous phases have equal |
1. potential energy. 2. kinetic energy. 3.temperature. 4. intermolecular forces of attraction. |

A liquid of density 1000 kg/m3 flows through a pipe diameter 1 inch at velocity of 1.5 m/s, given friction factor 0.00025, calculate the frictional pressure drop per unit length? |
1. 88.5 N/m2 2. 80.5 N/m2 3. 10 N/m2 4. 100 N/m2 |

A methanol-water vapor liquid system is at equilibrium at 60 °C and 60 kPa. The mole fraction of methanol in liquid is 0.5 and in vapor is 0.8. Vapor pressure of methanol and water at 60 °C are 85 kPa and 20 kPa respectively. Assuming vapor phase to be an ideal gas mixture, what is the activity coefficient of water in the liquid phase? |
1. 1.2 2. 1.6 3. 7.5 4. 0.3 |

A piece of metal of specific gravity 13.6 is placed in mercury of specific gravity 13.6, what fraction of it’s volume is under mercury? |
1. the metal piece will be immersed in mercury by half 2. the metal piece will simply float over the mercury 3. metal piece will sink to the bottom 4. whole of the metal piece will be immersed with its top surface just at mercury level |

A rhinoceros is weighed on a large 2 m x 2 m scale at the zoo. If the rhinoceros weighs 40 000 N, how much pressure is exerted on the pad beneath the scale? |
1. 160 kPa 2. 404 kPa 3. 10 kPa 4. 100 kPa |

Calculate the total power requirement for a mass flow rate of 5 kg/s, and a static head of 5 m. Efficiency of pump is 70%. |
1. 35.7 W 2. 5.0 W 3. 25.7 W 4. 15.7 W |

Capacity (in tons/hr) of jaw/gyratory crusher is equal to (where, L = length of the receiving opening, cm S = greater width of the discharge opening, cm) |
1. 0.01 L.S 2. 0.087 L.S 3. L.S/0.087 4. L.S |

Convection heat transfer happens predominantly due to |
1. Conduction in the boundary layer 2. Bulk motion of the fluid 3. Newton’s law of cooling 4.high viscosity |

Dietus-Boelter equation used for the determination of heat transfer coefficient is valid |
1. Laminar internal flow 2. Laminar external flow 3. Turbulent external flow 4. Turbulent internal flow |

Effectiveness - NTU method is applied whenever |
1. Maximum heat transfer possible needs to be calculated 2. exit temperatures of both hot & cold streams needs be calculated 3. accurate results are needed 4. efficiency of the heat exchanger needs to be calculated |

For an evaporator or condenser, LMTD for a parallel flow is |
1. greater than that of counter flow 2. lesser than that of counter flow 3. same as that counter flow 4. greater than cross flow |

Answer all MCQs correctly with proper explanation.

Answer #1

1) A grey body is one whose absorptivity:-

correct ans: 1) does not vary with temperature and wavelength of the incident ray

Explanation: From the definition of grey body "If grey body is defined as a substance whose monochromatic emissivity and absorptivity are independent of wavelength"

2) A liquid is in equilibrium with its vapor at its boiling point. On an average, the molecules in the liquid and gaseous phases have equal:

Ans- 3) Temperature

10) Dietus-Boelter equation used for the determination of heat transfer coefficient is valid:

ans: 4) Turbulent internal flow

11) Effectiveness - NTU method is applied whenever

ans: 1) Maximum heat transfer possible needs to be calculated

there is a plate with 2ft width, 4ft length and 130°F
of the surface temperature. awater with 50°F of temperature flows
on this plate with 9ft/s velocity. Calculate the average heat
transfer coefficient and the convective heat loss in this plate.
For the calculation please use the following constant
properties.
heat conductivity(k)=0.36 Btu/(hr ft °F)
viscosity=5.14×10^(-4) lbm/(ft s)
density=62.11 lbm/(ft^(3))
Pr=5.12
Nu=0.036×Pr^(1/3)×Re^(2/3):laminar flow
Nu=0.036×Pr^(1/3)×(Re^(0.8)-23200):turbulent flow

1-The temperature value inside a reactor in the treatment plant
is 30 0C during operation. The outdoor temperature in the winter
period is 5oC. The wall thickness of the reactor is 0.10 m and its
area is 20 m2. Air and reactor wall heat transfer coefficients and
conductivity are given below.
reactor = 20W / m2.K, creator = 0.8 W / m.K; outdoor environment =
10 W / m2.K
a. Under these conditions, calculate the heat loss value from the...

1) An isentropic flow: a) has no heat transfer, b) does not
allow temperature to change, c) can occur in a real physical
problem, d) can only occur when the fluid is at rest.
2) Based on the first law of thermodynamics (assuming no
chemical reactions, i.e. just a simple gas like air or helium): a)
changing the flow velocity can heat the flow, b) moving a solid
body through a fluid can heat the fluid, c) compressing a perfectly...

4.1A membrane made of 0.1 mm thick soft rubber separates pure O2
at 1 atm and 25oC from air at 1.2 atm pressure. Determine the mass
flow rate of O2 through the membrane per unit area and the
direction of flow.
Molar flow rate of oxygen is given by: ???? = ???????? / ???
(????1 ? ????2 )
where S is solubility of oxygen in rubber.
The mass diffusivity of oxygen in rubber at 298 K is DAB = 2.1...

1 . A 100 kg person has a body temperature of 37°C. Hypothermia
occurs at 35°C . He loses heat at a rate of 300 W to his
surroundings for two hours . Use a specific heat of 3.500 j kg-1
k-1 for the humans tissue . If the metabolic for an activity is 280
W . Find the change in temperature for this activity.
a) 6.9 °C
b) 1.7 °C
c) 0.04 °C
d) 5.4 °C
2. Jack is...

1.
Find values of residual enthalpy for ethylene at 400 K and 25 bar
using Peng-Robinson equation of state.
2. Find values of residual Gibbs energy, enthalpy and entropy
for n-heptane at 500 K and 100 bar using Virial equation of
state.
3. Estimate the values of Compressibility factor, enthalpy and
entropy for Benzene and cyclohexane if it compressed from 650 K and
60 bar to 500 K and 110 bar.
4. Calculate ΔU and ΔH for 1 kg of...

1. An oven chimney is
made of brick with a heat transmission coefficient 1.1 W/mK 10 cm
thick. Since the shaft exterior radiation beam coefficient is 0.8
and the flue gas temperature is 350°C, the external ambient
temperature is 25°C and the outer ambient heat transport
coefficient is 20 W/m2K;
a) Calculate the shaft exterior
temperature.
b) In order to reduce the risk of burn
injury that may occur in the body, the shaft is asked to be below
55°Cve...

1. Mark the correct answer.
Select one:
a. The resistivity of a superconductor is infinite.
b. The resistivity of a conductor increases as the temperature
decreases.
c. None of the other options is correct.
d. The electric current is the rate of flow of electric charge,
I=ΔQ/ΔtI=ΔQ/Δt.
2. Mark the correct statement.
Select one:
a. None of the other options is correct.
b. A compass needle must be made out of ferromagnetic
material.
c. A compass needle need not be...

1) A nozzle is a device for increasing the velocity of a
steadily flowing stream of fluid. At the inlet to a certain nozzle
the enthalpy of the fluid is 3025 kJ/kg and the velocity is 60 m/s.
At the exit from the nozzle the enthalpy is 2790 kJ/kg. The nozzle
is horizontal and there is negligible heat loss from
it.
(i) Find the velocity at the nozzle exit.
(ii) If the inlet area is 0.1 m2 and specific volume...

Procedure Reaction 1: Dissolving the Copper 1. Obtain a clean,
dry, glass centrifuge tube. 2. Place a piece of copper wire in a
weighing paper, determine the mass of the wire and place it in the
centrifuge tube. The copper wire should weigh less than 0.0200
grams. 3. In a fume hood, add seven drops of concentrated nitric
acid to the reaction tube so that the copper metal dissolves
completely. Describe your observations in the lab report. (Caution,
Concentrated nitric...

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