Question

A grey body is one whose absorptivity 1. does not vary with temperature and wavelength of...

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.

Homework Answers

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

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