Question

The shape factor in radiative heat transfer depends on:

• A. Surface temperatures only
• B. Surface emissivities only
• C. Geometry and relative orientation of surfaces
• D. Thermal conductivity of surfaces

Hint:

Think of the shape factor as a line-of-sight calculation.
How much one surface "sees" another depends only on their shapes, positions, and orientations, making it a purely geometric parameter.

Answer 1

The Correct Option is C

Step 1: Understanding the Question:
The question asks about the physical parameters that determine the shape factor (also known as the view factor or configuration factor) in radiation heat transfer.

Step 2: Key Formula or Approach: This is a conceptual question. The shape factor \(F_{ij}\) is defined as the fraction of radiation leaving surface \(i\) that is directly intercepted by surface \(j\).

Step 3: Detailed Explanation:

• The shape factor is a purely geometric quantity that describes how two surfaces see each other.

• It is derived mathematically by integrating the solid angles between the differential areas of the two surfaces.

• Because it is based entirely on geometry, the shape factor depends only on the shapes of the surfaces, their sizes, the distance separating them, and their relative spatial orientation.

• It does not depend on physical surface properties such as temperature (Option A), emissivity (Option B), or thermal conductivity (Option D).

Step 4: Final Answer:
The shape factor in radiative heat transfer depends on the geometry and relative orientation of the surfaces.