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Heat-transfer Questions Set 19:

Quiz Mode

How many modes of heat transfer are there?

Solution:

Which material has the lowest solar absorptivity?

Snow

Polished aluminum

Red brick

Aluminum foil

Solution:

For laminar flow, the Reynolds number should be:

Equal to 2300

Greater than 2300

Less than 2300

Less than 4300

Solution:

Which property is true for an opaque body?

Transmissivity is zero

Reflectivity is zero

Absorptivity is zero

Reflectivity is unity

Solution:

To find the Fourier's number, given the characteristic length, which of the following parameters is also required?

Area

Length

Thermal resistance

Thermal diffusivity

Solution:

Heat transfer takes place according to which of the following laws?

Newton's second law of motion

First law of thermodynamics

Newton's law of cooling

Second law of thermodynamics

Solution:

If the actual heat transfer rate from a fin is known, what other value is required to find the fin efficiency?

Total heat transfer from finned surface.

Maximum possible heat transfer rate.

Temperature difference.

Convective heat transfer coefficient.

Solution:

For a given thermocouple, find the time constant if the density is 8000 kg/m³, specific heat capacity (Cp) = 420 J/kg°C, radius (R) = 0.004 m, and heat transfer coefficient (h) = 40 W/m²°C. (Characteristic length, Lc = R/3).

120 seconds

112 seconds

200 seconds

70 seconds

Solution:

A thin metal plate of 4 cm diameter is suspended in atmospheric air whose temperature is 290 K. This plate attains a temperature of 295 K when one of its faces receives radiant energy from a heat source at the rate of 2 W. If the heat transfer coefficient on both surfaces of the plate is 87.5 W/m²K, calculate the energy lost by reflection.

0.8 W

0.3 W

0.9 W

0.10 W

Solution:

Which of the following statements regarding one-dimensional heat transfer is correct?

Steady-state is a function of x, y, t; Unsteady-state is a function of x

Steady-state is a function of x; Unsteady-state is a function of x, t

Steady-state is a function of y, z; Unsteady-state is a function of y

Steady-state is a function of x, t; Unsteady-state is a function of x

Heat-transfer Questions Set 19:

How many modes of heat transfer are there?

Solution:

Which material has the lowest solar absorptivity?

Solution:

For laminar flow, the Reynolds number should be:

Solution:

Which property is true for an opaque body?

Solution:

To find the Fourier's number, given the characteristic length, which of the following parameters is also required?

Solution:

Heat transfer takes place according to which of the following laws?

Solution:

If the actual heat transfer rate from a fin is known, what other value is required to find the fin efficiency?

Solution:

For a given thermocouple, find the time constant if the density is 8000 kg/m³, specific heat capacity (Cp) = 420 J/kg°C, radius (R) = 0.004 m, and heat transfer coefficient (h) = 40 W/m²°C. (Characteristic length, Lc = R/3).

Solution:

Solution:

Which of the following statements regarding one-dimensional heat transfer is correct?

Solution:

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