Neetu Singh: Steady State Heat Conduction Quiz

Steady State Heat Conduction

• The rate of heat conduction through a plane layer is proportional to the temperature difference across the layer and the heat transfer area, but is inversely proportional to the thickness of the layer.

Thermal Conductivity

• Thermal conductivity (k) is a measure of a material's ability to conduct heat.
• It is the rate of heat transfer through a unit thickness of the material per unit area per unit temperature difference.
• A high value of thermal conductivity indicates a good heat conductor, while a low value indicates a poor heat conductor or insulator.
• The thermal conductivity of a gas varies with the square root of the absolute temperature.

Heat Transfer through a Wall

• The rate of heat transfer through a wall can be calculated using the thermal conductivity of the wall material, the temperature difference, and the thickness of the wall.

Analogy between Thermal and Electrical Resistance

• There is an analogy between thermal and electrical resistance concepts.

Steady State Heat Conduction through a Composite Wall

• The overall heat transfer coefficient (U) is used to calculate the heat transfer through a composite wall.

Insulation on Radial System

• Adding insulation to a radial system (cylindrical/spherical shell) increases the conduction resistance of the insulation layer but decreases the convection resistance of the surface.
• The heat transfer from the pipe may increase or decrease, depending on which effect dominates.

Insulated Cylindrical Pipe

• The rate of heat transfer from the insulated pipe to the surrounding air can be expressed as a function of the inner radius, outer radius, temperature difference, and thermal conductivity.

Critical Thickness of Insulation

• The critical thickness of insulation is the outer radius of insulation that maximizes the heat transfer rate.
• If the outer radius is less than the critical value, adding more insulation will increase the heat transfer rate.
• If the outer radius is greater than the critical value, adding more insulation will decrease the heat transfer rate.

Determination of Optimum Thickness of Insulation

• The optimum thickness of insulation is based on the minimum total cost of insulation and heat lost.
• The cost of insulation increases roughly linearly with thickness, while the cost of heat loss decreases exponentially.
• The total cost decreases first, reaches a minimum, and then increases.