Question

The driving force for heat conduction is called as:

• A. Temperature gradient
• B. Concentration gradient
• C. Pressure gradient
• D. Velocity gradient

Hint:

Remember the standard transport driving forces: - Heat Conduction \(\rightarrow\) Temperature gradient - Mass Diffusion \(\rightarrow\) Concentration gradient - Fluid Flow \(\rightarrow\) Pressure gradient - Shear Stress \(\rightarrow\) Velocity gradient

Answer 1

The Correct Option is A

Concept: Transport phenomena involve the movement of physical properties like mass, energy, or momentum due to an imbalance or gradient within a medium. Heat transfer by conduction is governed by Fourier's Law of Heat Conduction, which relates the heat flux to the spatial variation of temperature.

Step 1: Analyzing Fourier's Law of Heat Conduction.
Fourier's Law states that the rate of heat transfer through conduction per unit area (heat flux, \(q\)) is directly proportional to the spatial temperature change. Mathematically, it is expressed as: \[ q = -k \frac{dT}{dx} \] where:
• \(q\) is the heat flux (\(\text{W/m}^2\)).
• \(k\) is the thermal conductivity of the material (\(\text{W/m}\cdot\text{K}\)).
• \(\frac{dT}{dx}\) is the temperature gradient along the direction of heat flow. The negative sign indicates that heat naturally flows down the gradient, from regions of higher temperature to regions of lower temperature.

Step 2: Identifying the driving potential for heat transfer.
In thermal systems, a heat flow cannot occur if the temperature is uniform throughout the material (\(\frac{dT}{dx} = 0\)). For heat to flow, a spatial variation in temperature must exist. Therefore, the temperature gradient acts as the direct driving force for heat conduction.

Step 3: Comparing with other physical gradients.
Let us review what the other gradients drive to clarify the distinctions:
• Concentration gradient (\(\frac{dC}{dx}\)): Acts as the driving force for mass diffusion (governed by Fick's Law).
• Pressure gradient (\(\frac{dP}{dx}\)): Acts as the driving force for bulk fluid flow through channels or pipes.
• Velocity gradient (\(\frac{du}{dy}\)): Acts as the driving force for momentum transport and shear stress within viscous fluids (governed by Newton's Law of Viscosity). Thus, the driving force for heat conduction is specifically the temperature gradient, matching option (1).