An experimental facility is constructed to measure the thermal conductivity of various building materials. The apparatus

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An experimental facility is constructed to measure the thermal
conductivity of various
building materials. The apparatus is designed so that there is only
one-dimensional
heat transfer between two parallel isothermal surfaces of the
material being tested.
A 20 cm x 20 cm x 5 cm concrete slab is placed in the unit. The two
isothermal walls,
which are 5 cm apart, are held at uniform temperatures of 50 oC and
20 oC. The rate
of the steady heat transfer between the two surfaces is 132 W. The
thermal
conductivity of the slab is:
a) 10.1 W/m.K
b) 2.5 W/m.K
c) 5.5 W/m.K
d) 8.3 W/m.K
e) 13.4 W/m.K