A picture window has dimensions of 1.40 m×2.50 m and is made of glass 5.20 mm thick. On a winter day, the temperature of the outside surface of the glass is −20.0∘C, while the temperature of the inside surface is a comfortable 19.5∘ C. (a) At what rate is heat being lost through the window by conduction? (b) At what rate would heat be lost through the window if you covered it with a 0.750-mm-thick layer of paper (thermal conductivity 0.0500wm⋅k

Question

A picture window has dimensions of 1.40 m×2.50 m and is made of glass 5.20 mm thick. On a winter day, the temperature of the outside surface of the glass is −20.0∘C, while the temperature of the inside surface is a comfortable  19.5∘ C. (a) At what rate is heat being lost through the window by conduction? (b) At what rate would heat be lost through the window if you covered it with a 0.750-mm-thick layer of paper (thermal conductivity 0.0500wm⋅k

Debbie Moore · Accepted Answer

We can calcualte the thermal resistance via  R=LK  =0.52×10−2 m0.8 Wm⋅K  =6.5×10−3m2⋅KW  The rate of heat loss can be determined from  H=AR[TH−TC]  =1.4 m×2.5 m×[19.5−(−20)]K6.5×10−3m2⋅KW  =2.1×104 W

Bertha Jordan · Accepted Answer

b. Kpaper=0.05 Wm⋅K, Lpaper=0.075 cm After converting the window with paper there will be additional thermal resistance Rt=Rglass+Rpaper for Rpaper Rpaper=LK =0.075×10−2 m0.05 Wm⋅K =0.015 m2⋅KW Rt=0.015+6.5×10−3 =0.0125 m2⋅KW To calculated the rate of heat loss, calculate Rtask H=AR[TH−TC] =1.4 m×2.5 m×[19.5−(−20)]0.0125 m2⋅KW =6.4×103 W

A picture window has dimensions of 1.40\ m\times2.50\ mZS

Answered question

Answer & Explanation

New Questions in Other