Physics

Problem

A freezer panel of area

0.60\,\text{m}^2

and thickness

20\,\text{mm}

must restrict steady heat gain to at most

20\,\text{W}

when the temperature difference between its two faces is

25\,\text{K}

. Which one of the following materials will satisfy the requirement? (Thermal conductivity

k

values are indicated.) a) Expanded polystyrene,

k = 0.030\,\text{W m}^{-1}\,\text{K}^{-1}

b) Aerogel blanket,

k = 0.015\,\text{W m}^{-1}\,\text{K}^{-1}

c) Gypsum board,

k = 0.17\,\text{W m}^{-1}\,\text{K}^{-1}

d) Glass wool,

k = 0.040\,\text{W m}^{-1}\,\text{K}^{-1}