Mechanical Engineering - Heat Transfer, Refrigeration and Air Conditioning - Discussion
Discussion Forum : Heat Transfer, Refrigeration and Air Conditioning - Section 5 (Q.No. 31)
31.
A composite slab has two layers of different materials with thermal conductivities k1 and k2. If each layer has the same thickness, then the equivalent thermal conductivity of the slab will be
k1 k2
k1 + k2
Discussion:
10 comments Page 1 of 1.
Debnath said:
5 years ago
dQ = AdT/summation (x/k1 +x/k2).
KAdT/(x+x) = AdT.k1.k2/x(k1+k2).
K/2 = k1k2/(k1+k2).
K = 2k1k2/(k1+k2).
KAdT/(x+x) = AdT.k1.k2/x(k1+k2).
K/2 = k1k2/(k1+k2).
K = 2k1k2/(k1+k2).
(1)
SURU said:
5 years ago
Composite means series.
Total resistance equal to add all.
2x/kA =x/kA+x/kA.
So, answer D is correct.
Total resistance equal to add all.
2x/kA =x/kA+x/kA.
So, answer D is correct.
Harsh said:
5 years ago
Option D is correct.
Since R eq= R1+R2 so substituting the values of R we will get option D.
Since R eq= R1+R2 so substituting the values of R we will get option D.
Gaurav said:
5 years ago
Option C is for equivalent spring deflection. Here the answer is D.
Joy said:
6 years ago
D is correct.
However, there shouldn't be the 2 in the numerator.
However, there shouldn't be the 2 in the numerator.
Abhilash said:
8 years ago
D is correct. I agree with the Given answer.
Dixit said:
7 years ago
No, K1.k2/k1+k2 is the right option.
Akash said:
6 years ago
It should be (k1.k2)/(k1+k2).
Ankit said:
6 years ago
Answer should be K1K2/K1+K2.
Debashis said:
8 years ago
Answer C is correct.
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