Heat Transfer Co-Efficient Calculation
Autor: Adnan • February 10, 2018 • 1,125 Words (5 Pages) • 594 Views
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Prandtl Number:
Equation 5[pic 15]
Reynold's Number:
Equation 6[pic 16]
Nusselt Number:
Equation 7[pic 17]
Using the above equations (5, 6 and 7):
For Cooling water:
Prandtl Number, Prcw = = = 4.981[pic 18][pic 19]
Reynold's Number, Recw = = = 48.318[pic 20][pic 21]
Nusselt Number. Nucw = = 6.146[pic 22]
Similarly, for product:
Prandtl Number, Prp = 4.527
Reynold's Number, Rep = 49.131
Nusselt Number, Nup = 5.979
Nusselt number can also be defined as:
Equation 8[pic 23]
where, h = film heat transfer co-efficient
Rearranging equation 8 in terms of h, gives:
Equation 9[pic 24]
Using the above equation the film transfer co-efficient for cooling water and product can be found as follows:
For cooling water, hcw = = = 449.32 Wm-2 °C-1[pic 25][pic 26]
Similarly for product, hp = 441.46 Wm-2 °C-1
The overall heat transfer co-efficient for the heat exchanger (UPHE1) can be calculated using the following equation (Coulson and Richardson Volume 6, Chapter 12):
Equation 10[pic 27]
All the values on the right hand side of equation 10 have been calculated above, as shown. Putting in these values and rearranging in terms of UPHE1 :
Overall heat transfer co-efficient, UPHE1 = [pic 28]
= 207.54 W m-2 °C-1
The heat transfer co-efficient have been calculated for old and new heat exchangers. The exchangers are compared and results analysed in the discussion section below.
For Coil in Reactor RV1
Table 2 Technical and Physical Data for Coil
Parameters
Notation
Units
Value
Internal Diameter Tube
di
Mm
4
Given
M
0.004
Internal Coil Area
Ai
m2
1.26E-05
=(π*di2)/4
Thickness of Tube
tt
Mm
1
Outside Diameter tube
do
Mm
6
=di+(2*tt)
M
0.006
Outside Coil Cross Sectional Area
Ao
m2
2.83E-05
Average Coil Diameter
dav
M
0.005
Length of Paddle
L
Cm
40
M
0.4
Turns of Coils
Nt
18
Thermal Conductivity Stainless Steel
Kw
W m-1C-1
16.7
Coil Width
dc
Cm
50
Number of Revolutions
N
rev/s
1
Assumed
Flow Rate Through Coil
F
l/min
5
Assumed
m3/s
8.33E-05
Velocity Through the Tube
u
m/s
6.63
=F/Ai
Reactor Diameter
dr
M
0.75
Equivalent Straight Length of Coil
Le
M
28.27
=π*dc*Nt
Total Heat Transfer Area
Aht
m2
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