Question

16a) A triple glazed window consists of 3 clear glass
panes of 4 mm thickness each, separated by two
air cavities of 13 mm each in thickness. The
window area is 1.0 m2
. If the thermal conductivity
of the glass panes is 0.8 W•m-1•K-1 and of the air
cavities is 0.026 W•m-1•K-1 what is the total
thermal resistance of the window?
(A) 2.452 K•W-1
(B) 0.015 K•W-1
(C) 1.015 K•W-1
(D) 6004 K•W-1

16b)A heater provides 305 W of heating in the heated
space below which has a wall adjacent to an
unheated space which has only one external wall.
All the surfaces except walls A and B are
adiabatic. The U values for walls A and B are 1.5
W•m-2•K-1 and 3.0 W•m-2•K-1 and the surface areas
for walls A and B are each 11.3 m2
. Assume
steady state conditions and perfectly air tight
rooms. If the ambient temperature is -1oC what is
the temperature (T2) of the unheated room?(A) 7oC
(B) 8oC
(C) 17oC
(D) 18oC

16c)0.10 kmol of air is heated from 20oC to 50oC
in a closed cylinder. The change in enthalpy H
will be?
(A) 62.4 kJ
(B) 87.3 kJ
(C) 2.15 kJ
(D) 3.015 kJ

Answer 1