Heat Transfer 2025 Assignment 2

What is thermal diffusivity?

• The ability of a material to store thermal energy

• The rate of heat transfer through a material

• The measure of heat generation in a material

• The ratio of thermal conductivity to heat capacity

What does a material with high thermal diffusivity do?

• Is a poor conductor of heat

• Responds quickly to temperature changes

• Stores heat efficiently

• Has low thermal conductivity

In one-dimensional steady-state conduction, what is assumed about heat generation?

• It is maximum

• It is constant

• It varies with time

• It is negligible

What analogy exists between heat diffusion and electrical charge?

• Conduction is like current

• Heat is like voltage

• Thermal resistance is like electrical resistance

• Temperature is like charge

What is the thermal resistance for convection derived from?

• The second law of thermodynamics

• The first law of thermodynamics

• Newton’s law of cooling

• Fourier’s law of heat conduction

What does the equivalent thermal circuit for a plane wall represent?

• The material properties of the wall

• The temperature difference across the wall

• The thermal resistance of the wall

• The heat transfer rate through the wall

What is the overall heat transfer coefficient U used for?

• To calculate thermal resistance

• To analyze fluid motion

• To determine temperature differences

• To express heat transfer in composite systems

What causes thermal contact resistance?

• Fluid motion

• Temperature differences

• Material thickness

• Surface roughness effects

How can contact resistance be reduced?

• By increasing surface roughness

• By increasing the gap between surfaces

• By selecting a fluid with low thermal conductivity

• By using a fluid with high thermal conductivity

What is the purpose of extended surfaces in heat transfer?

• To reduce heat transfer

• To enhance heat transfer between a solid and fluid

• To insulate the solid

• To increase thermal resistance