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Heat-transfer Questions Set 4:

Quiz Mode

Which heat exchanger has the highest overall heat transfer coefficient?

Feed water heaters

Steam condensers

Alcohol condensers

Ammonia condensers

Solution:

A fin of finite length can be approximated as one of infinite length when the value of the product m * l is:

greater than 5

less than 1

between 1 and 5

zero

Solution:

When the absorptivity is α, reflectivity is ρ, and transmittivity is τ, which of the following is true for a diathermanous body?

α = 0, ρ = 0 and τ = 1

α = 0, ρ = 1 and τ = 0

α = 1, ρ = 0 and τ = 0

α + ρ = 1 and τ = 0

Solution:

In which of the following examples is steady-state heat transfer observed?

Electric bulb cools down due to the surrounding atmosphere

Boilers and turbines

Cooling of I.C. engine

Chilling effect of cold wind on a warm body

Solution:

If the mass flow rate specific heat product of both fluids in a heat exchanger is the same, and the hot fluid enters at 76°C and leaves at 47°C, while the cold fluid enters at 28°C and leaves at 55°C, find the effectiveness of the heat exchanger.

0.60

1.0

0.16

0.72

Solution:

To find the overall fin effectiveness, which additional parameter is required if the heat transfer from the base surface without fins is given?

Total heat transfer from finned surface.

Actual heat transfer from fin surface.

Convective heat transfer coefficient.

Temperature difference

Solution:

Which of the following statements about Prevost's theory of heat exchange is true?

Transfer of heat from low temperature body to high temperature body is not possible

Radiation does not require medium for heat transfer

None of the above

All the bodies above absolute zero emit radiation

Solution:

The tube surface temperature is maintained at 70 degrees Celsius, and the water is heated from an inlet temperature of 15 degrees Celsius to an outlet temperature of 45 degrees Celsius. Find the mean temperature of the water.

60 degrees Celsius

30 degrees Celsius

65 degrees Celsius

130 degrees Celsius

Solution:

In a particular Ingen-Hausz experiment setup, two rods made of different materials were coated with a uniform layer of wax all around. If the thermal conductivity of the first rod is twice the thermal conductivity of the second rod, what is the ratio of the lengths up to which the wax coating would melt in the two rods?

2.636 : 1

4 : 1

1.414 : 1

2 : 1

Solution:

Which of the following statements about heat transfer is incorrect?

Heat transfer in liquids and gases occurs primarily through convection.

The rate of heat flow through a body depends on the material of the body.

The thermal conductivity of solid metals increases with a rise in temperature.

The logarithmic mean temperature difference is not equal to the arithmetic mean temperature difference.

Heat-transfer Questions Set 4:

Which heat exchanger has the highest overall heat transfer coefficient?

Solution:

A fin of finite length can be approximated as one of infinite length when the value of the product m * l is:

Solution:

When the absorptivity is α, reflectivity is ρ, and transmittivity is τ, which of the following is true for a diathermanous body?

Solution:

In which of the following examples is steady-state heat transfer observed?

Solution:

If the mass flow rate specific heat product of both fluids in a heat exchanger is the same, and the hot fluid enters at 76°C and leaves at 47°C, while the cold fluid enters at 28°C and leaves at 55°C, find the effectiveness of the heat exchanger.

Solution:

To find the overall fin effectiveness, which additional parameter is required if the heat transfer from the base surface without fins is given?

Solution:

Which of the following statements about Prevost's theory of heat exchange is true?

Solution:

The tube surface temperature is maintained at 70 degrees Celsius, and the water is heated from an inlet temperature of 15 degrees Celsius to an outlet temperature of 45 degrees Celsius. Find the mean temperature of the water.

Solution:

Solution:

Which of the following statements about heat transfer is incorrect?

Solution:

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