Heat Transfer 2025 Assignment 1

Which of the following statements distinguishes heat transfer from thermodynamics?

• Heat transfer deals with the equilibrium states of a system

• Thermodynamics studies the rate of heat transfer

• Heat transfer analyzes the mechanisms and rates of heat flow due to temperature differences

• Thermodynamics involves transient processes only

Which is NOT a mode of heat transfer?

• Conduction

• Convection

• Radiation

• Heat

In Fourier’s law of conduction, the negative sign indicates:

• Heat flows from low to high temperature

• Heat flows in the direction of decreasing temperature

• Thermal conductivity is negative

• Temperature gradient is constant

Thermal conductivity k has the unit:

• W/m²·K

• W/m·K

• W/K
  

• J·s/m²

Which example represents natural convection?

• Cooling of hot electronic chips by a fan

• Circulation of warm air in a room heated by a radiator

• Pumping water in a boiler

• Airflow over an aircraft wing

According to the Stefan–Boltzmann law, the emissive power of a blackbody is proportional to:

• T²
  

• T³

• T⁴

• T

The general 1-D unsteady conduction equation (with heat generation) is:

• 
• 
• 
• 

For 1-D steady-state conduction in a solid with constant k and no heat generation, the governing equation reduces to:

• 
• 
• 
• 

The heat transfer coefficient hh in Newton’s law of cooling depends on:

• Only temperature difference

• Only surface area

• Geometry, fluid motion, and fluid properties

• Only type of material

Heat flows through a 2 m² plane wall of thickness 0.2 m, thermal conductivity k = 0.5 W/m·K, with a temperature difference of 40°C across it. The rate of heat transfer (Q) is:

• 50 W

• 100 W

• 200 W

• 400 W