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Which of the following would lead to a reduction in thermal resistance?
1. In conduction; reduction in the thickness of the material and an increase in the thermal conductivity.
2. In convection, stirring of the fluid and cleaning the heating surface.
3. In radiation, increasing the temperature and reducing theemissivity.
Codes:
1. In conduction; reduction in the thickness of the material and an increase in the thermal conductivity.
2. In convection, stirring of the fluid and cleaning the heating surface.
3. In radiation, increasing the temperature and reducing theemissivity.
Codes:
- a)1, 2 and 3
- b)1 and 2
- c)1 and 3
- d)2 and 3
Correct answer is option 'B'. Can you explain this answer?
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Verified Answer
Which of the following would lead to a reduction in thermal resistance...
Ans. (b) 1. In conduction, heat resistance = Δ x/kA
Thus reduction in thickness and increase in area result in reduction of thermal resistance.
2. Stirring of fluid and cleaning the heating surface increases value of h, and thus reduces thermal resistance.
3. In radiation, heat flow increases with increase in temperature and reduces with reduction in emissivity. Thus thermal resistance does not decrease.
Thus 1 and 2 are correct.
Thus reduction in thickness and increase in area result in reduction of thermal resistance.
2. Stirring of fluid and cleaning the heating surface increases value of h, and thus reduces thermal resistance.
3. In radiation, heat flow increases with increase in temperature and reduces with reduction in emissivity. Thus thermal resistance does not decrease.
Thus 1 and 2 are correct.
Most Upvoted Answer
Which of the following would lead to a reduction in thermal resistance...
Reduction in Thermal Resistance
In order to understand the reduction in thermal resistance, let's first discuss the concept of thermal resistance. Thermal resistance is a measure of how difficult it is for heat to flow through a material or a system. It depends on various factors such as the thickness of the material, its thermal conductivity, the surface condition, and the temperature difference across the material.
1. Conduction: Reduction in Thickness and Increase in Thermal Conductivity
Conduction is the transfer of heat through direct contact between solids. In this case, reducing the thickness of the material and increasing its thermal conductivity would lead to a reduction in thermal resistance.
- Reduction in Thickness: By reducing the thickness of the material, the distance for the heat to travel decreases, resulting in a lower thermal resistance. This is because heat can be conducted more easily through a thinner material.
- Increase in Thermal Conductivity: Thermal conductivity is a property of the material that determines its ability to conduct heat. By increasing the thermal conductivity, the material becomes more efficient at transferring heat, resulting in a lower thermal resistance.
2. Convection: Stirring of Fluid and Cleaning the Heating Surface
Convection is the transfer of heat through the movement of fluids (liquids or gases). In this case, two factors can lead to a reduction in thermal resistance: stirring of the fluid and cleaning the heating surface.
- Stirring of Fluid: By stirring the fluid, the stagnant boundary layer near the heating surface is disrupted, allowing fresh fluid to come into contact with the surface. This enhances the heat transfer and reduces the thermal resistance.
- Cleaning the Heating Surface: Any dirt, scale, or other contaminants on the heating surface can act as an insulating layer, impeding the heat transfer. By cleaning the heating surface, the thermal resistance is reduced as the heat can be transferred more effectively.
3. Radiation: Increasing Temperature and Reducing Emissivity
Radiation is the transfer of heat through electromagnetic waves. In this case, increasing the temperature and reducing the emissivity can lead to a reduction in thermal resistance.
- Increasing Temperature: According to Stefan-Boltzmann's law, the rate of heat transfer through radiation is proportional to the fourth power of the absolute temperature. Therefore, by increasing the temperature, the heat transfer through radiation increases, resulting in a lower thermal resistance.
- Reducing Emissivity: Emissivity is a measure of how effectively a surface emits thermal radiation. By reducing the emissivity, the surface emits less radiation, leading to a decrease in thermal resistance.
Based on the above explanations, the correct answer is option 'B' which includes reduction in thickness and increase in thermal conductivity (conduction) as well as stirring of fluid and cleaning the heating surface (convection).
In order to understand the reduction in thermal resistance, let's first discuss the concept of thermal resistance. Thermal resistance is a measure of how difficult it is for heat to flow through a material or a system. It depends on various factors such as the thickness of the material, its thermal conductivity, the surface condition, and the temperature difference across the material.
1. Conduction: Reduction in Thickness and Increase in Thermal Conductivity
Conduction is the transfer of heat through direct contact between solids. In this case, reducing the thickness of the material and increasing its thermal conductivity would lead to a reduction in thermal resistance.
- Reduction in Thickness: By reducing the thickness of the material, the distance for the heat to travel decreases, resulting in a lower thermal resistance. This is because heat can be conducted more easily through a thinner material.
- Increase in Thermal Conductivity: Thermal conductivity is a property of the material that determines its ability to conduct heat. By increasing the thermal conductivity, the material becomes more efficient at transferring heat, resulting in a lower thermal resistance.
2. Convection: Stirring of Fluid and Cleaning the Heating Surface
Convection is the transfer of heat through the movement of fluids (liquids or gases). In this case, two factors can lead to a reduction in thermal resistance: stirring of the fluid and cleaning the heating surface.
- Stirring of Fluid: By stirring the fluid, the stagnant boundary layer near the heating surface is disrupted, allowing fresh fluid to come into contact with the surface. This enhances the heat transfer and reduces the thermal resistance.
- Cleaning the Heating Surface: Any dirt, scale, or other contaminants on the heating surface can act as an insulating layer, impeding the heat transfer. By cleaning the heating surface, the thermal resistance is reduced as the heat can be transferred more effectively.
3. Radiation: Increasing Temperature and Reducing Emissivity
Radiation is the transfer of heat through electromagnetic waves. In this case, increasing the temperature and reducing the emissivity can lead to a reduction in thermal resistance.
- Increasing Temperature: According to Stefan-Boltzmann's law, the rate of heat transfer through radiation is proportional to the fourth power of the absolute temperature. Therefore, by increasing the temperature, the heat transfer through radiation increases, resulting in a lower thermal resistance.
- Reducing Emissivity: Emissivity is a measure of how effectively a surface emits thermal radiation. By reducing the emissivity, the surface emits less radiation, leading to a decrease in thermal resistance.
Based on the above explanations, the correct answer is option 'B' which includes reduction in thickness and increase in thermal conductivity (conduction) as well as stirring of fluid and cleaning the heating surface (convection).
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Which of the following would lead to a reduction in thermal resistance?1. In conduction; reduction in the thickness of the material and an increase in the thermal conductivity.2. In convection, stirring of the fluid and cleaning the heating surface.3. In radiation, increasing the temperature and reducing theemissivity.Codes:a)1, 2 and 3b)1 and 2c)1 and 3d)2 and 3Correct answer is option 'B'. Can you explain this answer?
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