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Heat-transfer Questions Set 7:

Quiz Mode

In sensible cooling of air, what is the coil efficiency?

1 - B.P.F.

B.P.F. - 1

Solution:

A cavity with a small hole will always behave as a

white body

black body

transparent body

opaque body

Solution:

What factors affect the convection heat transfer coefficient?

Surface geometry

Nature of fluid motion

Properties of fluid

All of the above

Solution:

A heat pump working on a reversed Carnot cycle has a coefficient of performance (COP) of 7. It takes 2 kW of work input. What is the refrigerating effect?

3 kW

4 kW

5 kW

12 kW

Solution:

Which type of heat exchanger configuration provides the best performance for the same heat transfer area and boundary conditions?

Parallel flow

Counter-flow

Cross-flow

All perform the same

Solution:

A flat plate with a surface area of 0.2 m² is maintained at a temperature of 150°C, while the surrounding air is at 25°C. If the convective heat transfer coefficient is 10 W/m²·K, calculate the heat transfer rate.

250 W

100 W

159 W

167 W

Solution:

A copper sphere with a diameter of 0.1 m is heated uniformly. If the thermal conductivity of copper is 400 W/(m·°C) and the temperature at the center of the sphere is 200°C, calculate the heat flux at the surface.

2000 W/m²

3000 W/m²

4000 W/m²

5000 W/m²

Solution:

A metal rod of length 0.5 m and cross-sectional area 0.01 m² conducts heat at a rate of 100 W. If the temperature difference between the ends of the rod is 50°C, determine the thermal conductivity of the material.

15 W/(m·°C)

18 W/(m·°C)

34 W/(m·°C)

20 W/(m·°C)

Solution:

The rate equation used to describe the mechanism of convection is called Newton's law of cooling. According to this law, the rate of heat flow by convection does not depend on:

Convective heat transfer coefficient

Surface area through which heat flows

Time

Temperature potential difference

Solution:

The shape factor for a complete rectangular furnace is given by the expression:

2/ d_x (a b + b c + c a) + 4 (0.64) (a + b +c) + 8 (0.45) d_x

2/ d_x (a b + b c + c a) + 4 (0.44) (a + b +c) + 8 (0.35) d_x

2/ d_x (a b + b c + c a) + 4 (0.34) (a + b +c) + 8 (0.25) d_x

2/ d_x (a b + b c + c a) + 4 (0.54) (a + b +c) + 8 (0.15) d_x

Heat-transfer Questions Set 7:

In sensible cooling of air, what is the coil efficiency?

Solution:

A cavity with a small hole will always behave as a

Solution:

What factors affect the convection heat transfer coefficient?

Solution:

A heat pump working on a reversed Carnot cycle has a coefficient of performance (COP) of 7. It takes 2 kW of work input. What is the refrigerating effect?

Solution:

Which type of heat exchanger configuration provides the best performance for the same heat transfer area and boundary conditions?

Solution:

A flat plate with a surface area of 0.2 m² is maintained at a temperature of 150°C, while the surrounding air is at 25°C. If the convective heat transfer coefficient is 10 W/m²·K, calculate the heat transfer rate.

Solution:

A copper sphere with a diameter of 0.1 m is heated uniformly. If the thermal conductivity of copper is 400 W/(m·°C) and the temperature at the center of the sphere is 200°C, calculate the heat flux at the surface.

Solution:

A metal rod of length 0.5 m and cross-sectional area 0.01 m² conducts heat at a rate of 100 W. If the temperature difference between the ends of the rod is 50°C, determine the thermal conductivity of the material.

Solution:

The rate equation used to describe the mechanism of convection is called Newton's law of cooling. According to this law, the rate of heat flow by convection does not depend on:

Solution:

The shape factor for a complete rectangular furnace is given by the expression:

Solution:

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