Question

Two infinite parallel plates are placed at a certain distance apart. An infinite radiation shield is inserted between the plates without touching any of them to reduce heat exchange between the plates. Assume that the emissivities of plates and radiation shield are equal. The ratio of the net heat exchange between the plates with and without the shield is
1. 1/2
2. 1/3
3. 1/4
4. 1/8

Answer 1

Correct Answer - Option 1 : 1/2

Concept:

Heat transfer relation when emissivities of plates and shield is same:

\(\frac{{{{\left( Q \right)}_{with\;shield}}}}{{{{\left( Q \right)}_{without\;shield}}}} = \frac{1}{{N + 1}}\)

where N is the number of shields.

Calculation:

Given:

N = 1

\(\frac{{{{\left( Q \right)}_{with\;shield}}}}{{{{\left( Q \right)}_{without\;shield}}}} = \frac{1}{{N + 1}} = \frac{1}{{1 + 1}} = \frac{1}{2}\)