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M. Muttakin et al.
Heat transfer
fluid inlet
Lf
Wf
Hf
Lm
Fig. 8.10 A module of a finned-tube heat exchanger
Let us consider a bed containing N m number of modules. Length of each module
is L m, and each module contains N t a number of tubes having outside and inside
diameters D m,o and D m,i respectively. If the tube material density is denoted by ρ t ,
the total mass of the tubes can be determined by,
M t =
π
4
D
2
m,o − D
2
m,i
L m N t ρ t
(8.39)
If L f , H f and W f are the fin’s length, height and width respectively, the fin surface
area that is in contact with the adsorbent can be calculated from,
A f = L f H f −
π
4
D
2
m,o N t
(8.40)
If there are N f number of fins in each module and the density of the fin material
is ρ f , the total mass of the fins can be expressed by,
M f = A f W f ρ f N f
(8.41)
Now, let us assume C p,t , C p,f and C p,s are the specific heat capacities of tube
material, fin material and silica gel. If M bed is the amount of adsorbent used in each
bed, we can write,
MC p
bed
=
M t C p,t + M f C p, f
N m + M bed C s
(8.42)
The adsorbent bed goes through adsorption, desorption, mass recovery and heat
recovery phases. Hence the model equations for each phase is narrated in the following sub-sections.