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Heat-transfer Questions Set 2:

Quiz Mode

How many types of convection processes are there?

Solution:

The different regions of the boiling curve are:

1, 2, 4

1, 2, 3

1, 3, 4

2, 3, 4

Solution:

With the increase in plate height, film thickness:

Increases

Decreases

Increases exponentially

Remains the same

Solution:

In Buckingham's π Method of dimensional analysis, the dimensional formula of each π term is:

M⁰L⁰T⁰

M²L²T³

M¹L²T³

M¹L²T²

Solution:

In a long, hollow cylinder maintained at uniform but different temperatures on its inner and outer surfaces, the heat transfer takes place in which direction?

Axial

Radial

No heat transfer

Unpredictable

Solution:

If the convective heat transfer coefficient is 110 W/m²-K, density is 0.88 kg/m³, velocity is 50 m/s, and specific heat capacity (Cp) is 1.001 kJ/kg-K, then find the Stanton number.

5.648 × 10^-3

5.648 × 10^3

2.497 × 10^-3

2.497 × 10^3

Solution:

Energy strikes a vertical hemispherical plate with an intensity of 640 W/m². The absorptivity is three times the transmissivity and twice the reflectivity. Determine the rate of transmission.

236.74 W/m²

116.37 W/m²

187.87 W/m²

456.09 W/m²

Solution:

Two balls of the same material and finish have their diameters in the ratio of 2:1. If both are heated to the same temperature and allowed to cool by radiation, the rate of cooling of the bigger ball compared to the smaller one will be in the ratio of:

4:6

4:1

1:4

1:1

Solution:

The inner surface of a brick wall is at 50°C and the outer surface is at 25°C. The wall is 220 mm thick, and the thermal conductivity of the bricks is 0.51 W/m⋅K. What is the rate of heat transfer per square meter of the wall's surface area?

20.65 W/m²

32.75 W/m²

47.62 W/m²

57.95 W/m²

Solution:

An electric cable with an aluminum conductor (thermal conductivity, k = 250 W/mK) is to be insulated with rubber (thermal conductivity, k = 0.15 W/mK). The cable is located in air (heat transfer coefficient, h = 6 W/m²K). What is the critical thickness of the insulation?

30 mm

25 mm

20 mm

10 mm

Heat-transfer Questions Set 2:

How many types of convection processes are there?

Solution:

The different regions of the boiling curve are:

Solution:

With the increase in plate height, film thickness:

Solution:

In Buckingham's π Method of dimensional analysis, the dimensional formula of each π term is:

Solution:

In a long, hollow cylinder maintained at uniform but different temperatures on its inner and outer surfaces, the heat transfer takes place in which direction?

Solution:

If the convective heat transfer coefficient is 110 W/m²-K, density is 0.88 kg/m³, velocity is 50 m/s, and specific heat capacity (Cp) is 1.001 kJ/kg-K, then find the Stanton number.

Solution:

Energy strikes a vertical hemispherical plate with an intensity of 640 W/m². The absorptivity is three times the transmissivity and twice the reflectivity. Determine the rate of transmission.

Solution:

Two balls of the same material and finish have their diameters in the ratio of 2:1. If both are heated to the same temperature and allowed to cool by radiation, the rate of cooling of the bigger ball compared to the smaller one will be in the ratio of:

Solution:

The inner surface of a brick wall is at 50°C and the outer surface is at 25°C. The wall is 220 mm thick, and the thermal conductivity of the bricks is 0.51 W/m⋅K. What is the rate of heat transfer per square meter of the wall's surface area?

Solution:

An electric cable with an aluminum conductor (thermal conductivity, k = 250 W/mK) is to be insulated with rubber (thermal conductivity, k = 0.15 W/mK). The cable is located in air (heat transfer coefficient, h = 6 W/m²K). What is the critical thickness of the insulation?

Solution:

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