Tubular juice heater design calculation with online calculator
The shell and tube multipass tubular juice heater consists of an assembly of tubes, the juice circulates through the tubes, and the vapour outside them. The juice to pass a certain number of times from bottom to top and from top to bottom of the heater by restricting the juice each time to a few of the tubes.
There are two principal designs of tubular juice heaters, the horizontal and the vertical, both are use in sugar Industry. The Vertical juice heaters are preferred because they occupy less floor space, are subject to less formation of scales and provide better facilities for cleaning.
Shell and Tube Multipass Heat Exchanger Design  Tubular juice heater design calculation with online calculator
Construction Parameters of Tubular Juice heater:
 The cylindrical shell containing the tube plates is extended at each end beyond the tube plate, the extended portion being divided into compartments by baffles.
 The heated media (juice) circulates through out tubes and heating media (vapours) circulated on shell side.
 The first compartment which is for juice inlet and last compartment which is for juice outlet. These two are located upper portion each compartment provides for two passes of upward and downward flow. If there are 22 tubes per pass, for example, there will be 44 tubes for each compartment, 22 for upward and 22 for downward flow.
 The shell and doors are material of construction( MOC ) consider as MS mild steel and for tube generally used Brass or SS304.
 Heat transfer coefficient plays an important role to find the heating surface calculation of the heater.
 Number of passes always should be consider even number.
 The legment of the tube plate generally consider 12mm for juice heater design.
 The prapotional factor of the tubes consider 0.6 to 0.8 for multiple passes of heater.
 Air vents and drain cocks shell be provide for each compartment.
 Juice velocity in tubes generally consider from 1.6 t0 2.0 m/sec. And heating media velocity consider as per the bleed vapour. The lower velocity of the juice in heater would foul more rapidly. For the high velocities the passage of the juice through the heater causes a marked pressure drop, which rapidly becomes prohibitive.
 Tubes have a diameter in the range of 38 to 50 mm. Tube lengths may vary between 3 m and 6 m. Longer tube designs lead to lower pressure drops at the same liquid velocity because of the reduced number of passes.
 The temperature different between outlet of the heated media(Juice) and condensate of the heating meadia(vapour) is called approach of the heater.
 The approach temperature depends upon heating media (bleed vapour), type of heater (Dead end or dynamic type). It is vary from 5 to 12^{o}C.
 For dynamic or vapour line juice heater the approach temperature comes upto 5 to 8^{o}C. For turbine exhaust or 1^{st} bleed vapours the approach comes 5 to 8^{o}C. The lower bleed vapours the temperature approach taken 8 to 12^{o}C
 Efficient removed to be required for condensate water and non condensable gases.
 Condensate outlets from the heater should be sufficient to ensure that the velocity of flow of the water does not exceed 1 m/s.
 The non condensible gases (NCG) removal purpose to be provide for every 10m^{2} heating surface area required minimum 1cm^{2} area.
 Heaters are tested, according to the intended permissible working pressure is 2.5 bars on shell side means vapour side and 6 bars on tube side means juice side.
 The dynamic type tubular juice heater having outlet vapour line along with the inlet vapour line. So the heating media having two connections of inlet and outlet. The heat transfer coefficient is higher in the dynamic type heater due vapour sweeping effect.
 In the dynamic type tubular juice heater outlet vapour line dia design for 70 to 100% on total vapour demand. So for the inlet vapour line dia designed for 70 to 200% on total vapour demand of the juice heater.
Heat Transfer Coefficient:
To know about fundamental concepts of heat transfer coefficient purpose go through the below link.
Heat transfer coefficient for shell and tube heat exchanger.
HTC depends upon
 Thermal conductivity of the tube metal.
 Diameter and the thickness of the tube.
 Clean lines of the tube surface from the inside and outside.
 Density, Velocity, viscosity & temperature of Juice to be heated.
 Efficient removal of condensate water and non condensable gases.
 Scale formation and its thickness over the tube surface
For complete information of Heat transfer coefficient calculation purpose please go through the below link
Juice Heater Heat Transfer Coefficient Calculation.
Thermal conductivity for different metals
Material Thermal conductivity in Kcal/m^{2}/hr/^{o}C
Copper 324.74
Aluminum 177.04
Brass 84.30
M.S 38.70
S.S 14.00
For simplification of the finding heat transfer coefficient (HTC) purpose our technologist proposed number formulas. Out of that the below mentioned formula is most popular for dead end type juice heaters. This formula have taken from HANDBOOK OF CANE SUGAR ENGINEERING by E. HUGOT.
K = 6 x Tv x [U / 1.8] ^{0.8}
This formula applicable only for dead end type sugar industry juice heater design.
Here K = HTC in Kcal/m^{2}/hr/^{o}C
Tv = vapour temperature in ^{o}C
U = Velocity of juice in m/sec
Heating Surface calculation of tubular juice heater
Fundamental formula :
Heat received by heated media(juice) = Heat rejected by heating media( vapour)
Q =M x Cp x ΔT = K x S x ΔTm
Where
Q = Heat transferred in kCal/hr
M= Quantity of material to be heating or cooling in kg/hr
Cp = Specific heat of material in Kcal/kg/^{o}C
ΔT = Temperature difference from inlet to outlet of the heated material in ^{o}C
S = Heat transfer surface area in m^{2}
ΔTm = LMTD = Log Mean Temperature Difference
K = Overall heat transfer Coefficient Kcal/m^{2}/hr/^{o}C
Ti / To = Hot fluid inlet/outlet (vapour)
ti / to = Cold fluid inlet/outlet (Juice)
ΔT = to – ti
^{ }
ΔTinlet = Ti – ti ( Co current Flow)
ΔT outlet = To – to (Co current Flow)
Here Heating media is vapour and utilize only the latent heat only so heating media inlet and outlet temperatures are same. So it is to be take as Tv
Design formulas of shell and tube multipass heater
Here we calculate with consider with the example.
To find the heat transfer coefficient by using above formula i.e K = 6 x Tv x [U / 1.8] ^{0.8 }
or to be calculate as per the standard formulas like below
Shell and tube Heater Heat Transfer Coefficient Calculation.
According to the heat transfer coefficient we can heating surface easily by the above formula.
S.no  Particulars  Sign and formulas  Values  UOM  
Data to be required for calculation  
1  Crushing rate  TCH  210  TCH  
2  Juice % cane  P  102  %  
3  Velocity of Juice  Vj  1.8  m/sec  
4  Density of juice  ρ  1.06  gm / ml^{3}  
5  Tube OD  OD  45  mm  
6  Tube Thickness  Tk  1.2  mm  
7  Tube ID  ID  42.6  mm  
8  Tube length  L  4000  mm  
9  Specific heat of juice  Cp  0.9  Kcal/Kg/^{o}C  
10  Legment  Lg  12  mm  
11  Vapour inlet temperature  Tv  85  ^{o}C  
12  Juice inlet temperature  ti  60  ^{o}C  
13  Juice outlet temperature  to  75  ^{o}C  
14  Tube plate thickness  Tb  25  mm  
15  Velocity of vapour  Vv  40  m/sec  
16  Heater Heating Surface  S  250  m^{2}  
17  Velocity of condensate  Vc  1  m/sec  
18  Proportional factor  β = 0.7 to 0.8  0.7  
19  Latent heat of vapour 

548.24  kcal/Kg  
20  Specific volume of vapour  μ  2.83  M^{3}/kg  
Calculation part  
1  Number of tubes per pass  
Volume of the juice  M = (TCH x P) / ( ρ x 3600)  0.0561  M^{3}/sec  
Area of the one tube  A = 0.785 x ID^{2}  0.0014  M^{2}  
M / ( A x Vj)  21.89  tubes/pass  
i.e  22.00  
2  Number of the tubes  
Mean Dia  Dm = OD – Tk  43.8  
Effective tube length  L m = L – 2 x Tb – 2 x 5  3940  
Number of the tubes  N t = S / ( π x Dm x Lm )  461.36  
i.e  462.00  no.s  
3  Number of Passes  n = Nt / tubes per pass  21.00  
3  Number of passes should be always taken even number ( n )  22  
As Per Even number of passes Heater parameters to be calculated  
4  No. of compartments  Top side = n/2 +1  12  
Bottom side = n/2  11  
5  Actual number of tubes  Nt = n x tubes per pass  484  no.s  
6  Actual heating surface  S = π x Dm x Lm x Nt 
262  m^{2}  
7  Actual velocity  Vj = M / Area of one pass  1.79  m/sec  
8  pressure drop across the juice heater  0.0025 x n x Vj^{2} x ( L/ ID +3)  17.10  MWC  
9  Tube plate dia  
Pitch  Pt = OD + Legment + Tube Tolerance(0.5mm) + Hole Tolerance(0.1mm)  57.6  
Tube plate Area  At = 0.866 x Pt^{ 2} x Nt / β  1.99  m^{2}  
Take 10% extra  2.19  m^{2}  
Tube plate dia  Dt = SQRT ( At / 0.785)  1668  mm  
10  Dia of juice inlet pipe  
Area Aj = M / Vj  0.031  m^{2}  
Dj = SQRT ( Aj / 0.785)  0.199  mtrs  
i.e  200  NB  
11  Vapour inlet Dia  Qj x Cp x ΔT = W x λ  mtrs  
Qj = TCH x P x 1000  214200  Kg/hr  
ΔT = to ti  15  ^{o}C  
W = weight of the vapour  5274.515  kg/hr  
Qv = W x μ /3600  4.146  M^{3}/ sec  
Av = Qv / Vv  0.104  m^{2}  
Take 10% extra  0.114  m^{2}  
Dv = SQRT ( Av / 0.785)  0.381  mtrs  
i.e  400  NB  
12  Condensate pipe Dia  
Qc = weight of the condensate = W  0.00147  M^{3}/sec  
Ac = Qc/ Vc  0.00147  M^{2}  
Take 50% extra for free removal  0.00220  M^{2}  
Dc = SQRT ( Ac /0.785)  0.053  mtrs  
i.e  75  mm  
13  NCG pipe line dia  
Cross section area of pipe  For every 10m^{2} Heating surface required 1 cm^{2} area to be required ( An )  26.23  cm^{2}  
SQRT (( An/4) / 0.785)  2.89  cm  
NCG pipe line dia  4 no.s NCG points and each having  32  mm  
14  Calendria shell thickness  (P* Di / (2*F*J – P) ) + C  
Maximum allowable pressure  P (Hydraulic test pressure)  3  kg/cm^{2}  
ID of the Juice heater  Di  1668  mm  
Allowable stress  F  1400  kg/cm^{2}  
Welding Joint efficiency  J  0.75  
Corrosion allowance  C = 1.5 for calendria shell  1.5  mm  
Calendria shell thickness  3.89  mm  
Say  4  mm  
But as per standard specification 12mm for longitude of equipment  
15  Tube plate thickness  f x G x SQRT((0.25 x P)/F) + C  
Corrosion allowance  C = 3.0mm for tube plate  3  mm  
Allowable stress  F  1400  kg/cm^{2}  
Maximum allowable pressure  P  3  kg/cm^{2}  
Modulus factor for MS sheet  Es  2100000  kg/cm^{2}  
Modulus factor for SS sheet  Et  1900000  kg/cm^{2}  
ID of the shell  G  1668  mm  
Thickness of the shell  ts  12  mm  
Thickness of tube  tt  1.22  mm  
OD of the tube  do  45  mm  
Do = OD of the calendria sheet  Do = ID + 2 x shell thickness  1692  mm  
Number of tubes  Nt  484  no.s  
K  K =( Es x ts x (Do ts)) /(Nt x Et x tt x(do tt))  0.862174  
f = safety factor  f = SQRT ( K / (2 + 3K))  0.433567  
Tube plate thickness  19.74  mm  
But as per standard specification 25mm for tube plate  
16  Thickness of the cover plate  tc = Gc x SQRT ( K x P /f ) + C.A  
ID of the shell  Gc  1668  mm  
For flat joint  K = 0.3  0.3  
Design Pressure  P  3  kg/cm^{2}  
Allowable stress  f  1400  kg/cm^{2}  
Corrosion allowance  C = 1.5mm for cover plate  1.5  mm  
Thickness of the cover plate  43.79  mm  
But as per the Indian practice to given 32mm cover plate with adequate stiffening is sufficient 
Tubular juice heater online calculator
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