Conduction Along a Composite Bar

Conduction along a composite bar 

Objective :

•

To study the conduction of heat along a composite bar and evaluate the overall heat transfer coefficient. Theory:

•

For study flow along the bar, the heat flow through successive slabs is the same for reasons of continuity and hence from Fourier's law: Q

= U  * (T   HS   HS   A Where :

1 U 

=

 X  H   K  H 

+

−

 X S   K S 

T CS  )

+

........

U is over all heat coefficients for the composite wall and 1/U is the over  all resistance to heat flow.

•

Results :

Test no.

1

2

3

Q.w 

10

15

20

T 1 .C   .C 

43.1

49.1

60.1

1

T 2 .C   .C 

40.4

46.2

56.1

2

T 3 .C   .C 

37.8

44.8

53.8

3

T 7 7 .C   

18.9

19.5

21.6

7  

T 8 .C   .C 

17.5

17.6

19.2

8

T 9 .C   .C 

16.3

16.5

17.8

9

•

∆x.cm

Figures :

-1-

70 Calculations :

•

Sample of calculation:  At Q=15 w  A =

d 2

U  = 1

U 

4 Q

 A

=

 K  H 

939 .02

 K  s

(T  HS 

 x H 

1

=

0.025 2

× π   =

+

=

−

4

T CS  )

 x s  K  s 3

110

+

+

1

−

×

=

3.14

=

4.9 ×10

15 4.9 ×10

4

−

×

4

−

m2 1

(49 .1 −16 .5)

=

939 .02 w / m2 .C 

 xc



 Actual 

 K c 3

+

 K  s

3 110



56 .095 w / m.C 

 K  s= 45.326 w/m.C@ T= 17C ( Unit operation of chemical engineering) Q.(w)

K s   .(w/m.C)

10

56.360

24.34

15

56.095

23.76  

20

56.067

23.69

•

Error. %

Discussion :

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    C

-2-

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•

Conclusions :

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