A composite slab consists of two layers having thermal conductivities K and 2K and thicknesses x and 4x, respectively. Its outer surfaces are maintained at T₂ and T₁, where T₂>T₁. In steady state the heat-transfer rate is written as H=f[AK(T₂-T₁)/x]. Find f.

Question

G1 Physics · Accepted Answer

The two layers are in series. Their thermal resistances are R₁=x/(KA) and R₂=4x/(2KA)=2x/(KA). Thus Rtotal=3x/(KA), so H=(T₂-T₁)/Rtotal=AK(T₂-T₁)/(3x). Therefore f=1/3. Option D.

A composite slab consists of two layers having thermal conductivities K and 2K and thicknesses x and 4x, respectively. Its outer surfaces are maintained at T₂ and T₁, where T₂&gt;T₁. In steady state the heat-transfer rate is written as H=f[AK(T₂-T₁)/x]. Find f.

A composite slab consists of two layers having thermal conductivities K and 2K and thicknesses x and 4x, respectively. Its outer surfaces are maintained at T₂ and T₁, where T₂>T₁. In steady state the heat-transfer rate is written as H=f[AK(T₂-T₁)/x]. Find f.