Chapter 3, Problem 23P

$\text{A 1}\text{.0 m }\times \text{ 1}\text{.5 m}$ double-pane window consists of two 4-mm-thick layers of glass $(k\text{ = 0}\text{.78 W/m}\text{.K)}$ and that are separated by a 5-mm air gap $(k_{air}\text{= 0}\text{.025 W/m}\text{.K)}\text{.}$ and The heat flow through the air gap is assumed to be by conduction. The inside and outside air temperatures are 20°C and -20°C, respectively, and the inside and outside heat transfer coefficients are

40 and 20 W/m² ⋅K. Determine (a) the daily rate of heat loss through the window in steady operation and (b) the temperature difference across the largest thermal resistance.