IJCPE Vol.9 No. 2 (June 2008) 

 

 

 
Iraqi Journal of Chemical and Petroleum Engineering 

 Vol.9 No.2 (June 2008) 43-50 
ISSN: 1997-4884 

 

Simulation of Wiped Film Evaporator 

Adil A. Al-Hemiri
*
, Emad F. Mansour 

**
 and Jamal A.L. Al-Ani 

** 

*
Chemical Engineering Department, College of Engineering, University of Baghdad. 

**
 Chemistry and Petrochemical Industries Research Administration, Ministry of Science and Technology. 

Abstract 

   

A mathematical model and associated computer program were developed to simulate the steady state operation of 

wiped film evaporators for the concentration of glycerol-water solution. In this model, various assumptions were made 

to facilitate the mathematical model of the wiped film evaporator. The fundamental phenomena described were: sensible 

heating of the solution and vaporization of water. Physical property data were coded into the computer program, which 

performs the calculations of this model. Randomly selected experiments were carried out in a small scale wiped film 

evaporator from ALVAL COMPANY, using different concentrations of the glycerol solution (10, 30 and 50 Wt. %) for 

different feed rates (30, 50, 80, 100 and 120 l/h) and two values of steam jacket pressure (2 and 4 atm) to compare 

between experimental and simulation results. The statistical analysis gave correlation coefficient of 0.9972, average 

absolute error of 2.2527 % and F-test of 0.9639 which showed the high accuracy of the simulation work. 

Keywords: Wiped film evaporator, Evaporators, Simulation of film evaporators

Introduction 

Evaporation is one of the main methods used in chemical 

industry for concentration of aqueous solutions that 

means the removal of water from solution by boiling the 

liquor in a suitable type of evaporator and withdrawing 

the vapor (Coulson & Richardson,1983). The objective of 

evaporation is to concentrate a solution consisting of non-

volatile solute and a volatile solvent. In the 

overwhelming majority of evaporations the solvent is 

water. Normally, in evaporation the thick liquor is the 

valuable product and the vapor is condensed and 

discarded. 

Agitated thin film evaporators, wiped film evaporators, 

are designed to spread a thin layer or film of liquid on 

one side of a metallic surface, with heat supplied to the 

other side. The unique feature of this equipment is not the 

thin film itself, falling and rising-film evaporators use 

thin liquid layers, but rather the mechanical agitator 

device for producing and agitating the film (APV, 2000). 

Conventional heat transfer equipment may not be well 

suited for certain evaporation applications, particularly 

those involving heat sensitive products, viscous material 

or chemical constituents that exhibit fouling or foaming 

tendencies. For products like these, mechanically agitated 

thin-film evaporators are often selected over more 

conventional evaporators because of their batter process 

economics and performance (Mutzenburg, 1965). 

For these applications, the heat transfer is not actually 

wiped or scraped but a highly agitated thin film is spread 

on to the metallic heat-transfer surface.  

Agitation has the benefits in thin film equipment other 

than liquid turbulence. The blades assure even 

distribution of the liquid over the metal heat transfer 

surface; they eliminate any channeling of liquid as the 

liquid flows down the evaporator; the considerable 

shearing effect decreases the apparent viscosity of most 

liquids, thus improving internal heat and mass transfer 

(Parker, 1965).
 
Also the heat transfer coefficient will be 

improved due to two reasons: 

 Turbulence is included in the bulk of the fluid 

and near to the transfer surface reducing the 

effects of the resistance to heat transfer at the 

wall, 

  Secondly where the surface is actually being scraped, 

the adhering film process liquid is constantly being 

University of Baghdad 

College of Engineering 
Iraqi Journal of Chemical 

and Petroleum Engineering 

 



Simulation of Wiped Film Evaporator 

 

44 
IJCPE Vol.9 No. 2 (June 2008) 

 

removed from the wall and distributed into the bulk of the 

liquid. At the same time fresh material is being presented 

to clean heat transfer surface. 

The heat flux and the evaporation capacity are affected 

by changes both in temperature drop and in the overall 

heat transfer coefficient. The temperature drop is fixed by 

the properties of the steam and the boiling liquid and 

except for the effect of hydrostatic head is not a function 

of the evaporator construction. The overall heat transfer 

coefficient, on the other hand, is strongly influenced by 

the design and the method of operation of the evaporator. 

In most services, a well-designed and properly specified 

unit can achieve a heat flux of 31550-78875 W/m
2
 when 

processing typical organic, and as high as 157750 W/m
2
 

in some aqueous applications (Abichandani et al , 1987).  

The overall resistance to heat transfer between the steam 

and the boiling liquid is the sum of five individual 

resistances: the steam-film resistance; the two scale 

resistance, inside and outside the tubes; the tube wall 

resistance; and the resistance from the boiling liquid. The 

overall coefficient is represented by equation (1). In most 

evaporators the fouling factor of the condensing steam 

and the resistance of tube wall are very small, and they 

are usually neglected in evaporator calculation. In 

agitated-film evaporator the tube wall is fairly thick so 

that the resistance may be a significant part of the total 

((Abichandani et al , 1987).  

 

 

1 1 1 1 1 1

w o io i

iw o

K K KU h h

LL L

    
                       (1) 

 

Due to the difficulty of measuring the individual film 

coefficient in an evaporator, experimental results are 

usually expressed in terms of overall coefficients. These 

are based on the net temperature drop corrected for 

boiling-point elevation. The overall coefficient, of course, 

is influenced by the same factors influencing individual 

coefficients; but if one resistance (say, that of the liquid 

film) is controlling, large changes in the other resistance 

have almost no effect on the overall coefficient (Freese & 

Glover, 1979). 

Freese & Glover, (1979), also,  reviewed a number of 

wiped film evaporators pilot-plants test on typical solvent 

recovery application performed at atmospheric conditions 

with steam as the heating medium. He showed that the 

overall heat transfer coefficient (U) ranging from 570-

850 W/m2ºC. 

Parker (1965) reported the variation in the value of 

overall heat transfer coefficient for a thin film scraped 

surface evaporator (TFSSE) between 1134 and 1985 

W/m2.ºC. 

Sangrame et al. (2000) studied the concentration of 

tomato pulp in a thin film scraped surface evaporator; the 

main body of the evaporator was 1.4 m high and 0.22 m 

in diameter. They found that for water as the feed, the 

overall heat transfer coefficient and evaporation rate 

ranged within 476.9-939 W/m2.ºC and 14.7-30.7 kg/h, 

respectively For tomato pulp, overall heat transfer 

coefficient, evaporation rate and final concentration 

(from 5.9% total solid initial concentration) were varied 

between 625.6- 910.9 W/m2.ºC, 13.22-33.72 kg/h and 

8.02-19.21 % TS, respectively. The range of operating 

parameters were: feed flow rate 40.8-51.0 kg/h, steam 

temperature 65-80 ºC and rotor speed 355 rev/min. The 

optimum process parameters for the concentration of 

tomato pulp at 355 rpm rotor speed were found to be 40.3 

kg/h feed flow rate and 73 ºC steam temperature. The 

optimum process parameters could give 840 W/m2.ºC 

overall heat transfer coefficient, 27 kg/h evaporation rate 

and 18 % total solids. 

Chuaprasert et al. (1999) and Chawankul et al. (2001) 

studied the steady state simulation of concentrating sugar 

syrup and orange juice respectively in ATFE using 

AspenPlus simulation program to develop the needed 

model. A rigorous heat exchanger model, Heatx followed 

by the rigorous 2-phase flash model, flash2, was used to 

simulate the dominant effects of the ATFE. 

The heat exchanger model was used to simulate the 

evaporator and required the heat transfer area (A), and the 

overall heat transfer coefficient (U). The output stream 

from the heat exchanger, a 2-phase stream consisting of 

concentrated orange juice and waster vapor, was fed to 

the 2-phase flash unit operating at the same pressure. The 

thermo-physical properties of both systems were not 

available in the Aspen Plus databank. They were 

therefore, determined experimentally and modeled as 

function of temperature and solid content. Heat transfer 

coefficients were predicted using correlations and 

measured from process measurements. Experimental and 

simulation results were compared and showed good 

agreement.   

 

 

MATHEMATICAL TREATMENT 

 
Several assumptions are taken in order to facilitate the 

mathematical treatment used in the development of the 

simulation software. These assumptions are summarized 

as follows: 

   *    Steady state operation. 

   *    Plug flow unit with no backmixing and no radial 

mixing. 

   *   Adiabatic Mode of Operation.  

   *   Negligible Energy Input from the rotating wiper 

blades. 

 



Adil A. Al-Hemiri, Emad F. Mansour and Jamal A.L. Al-Ani  

 

45 
IJCPE Vol.9 No. 2 (June 2008) 

 

The wiped-film evaporator for concentration of glycerol-

water solution is divided into two sections according to 

the primary phenomenon occurring therein: sensible 

heating of the solution, and vaporization of water. The 

governing material and enthalpy balance equations for 

each of these sections are presented below (Smith & Van 

Ness, 1987). 

In the sensible heating section, the solution stream is 

heated from its feed temperature to its initial boiling 

point; no phase change in this section and no change in 

the mass flow rate of solution stream occur. In an 

enthalpy balance about a (dz) increment in this section: 

 

Rate of Input H qd                  (2) 

d H
Rate of Output H z

d z
                  (3) 

Where    P RH WC t t  ,  

And        i i sd q U D t t z     

With no accumulation term, the rate of input must equal 

the rate of output, and the differential enthalpy balance 

equation is 

dH
dq z 0

dz
                  (4) 

Or 

 
 p R

i i s

d W C t t
U a t t d z d z 0

d z

 
 

    (5) 

Neglecting any change in Cp over a dz increment and 

recognizing that tR = constant then 

 i i s p
d t

U D t t W C 0
d z

      (6) 

 

 
Equation (6) can be integrated analytically between the 

limits of t = tF and t = tBP if Ui and Cp are assumed 

constant over this interval. Admittedly this is not true, but 

the height or length of the preheating zone is quite small, 

which is generally less than 10% of the total height or 

length of the heat transfer zone, in the proposed 

applications. Hence, average values of Ui and Cp based 

upon their values at the feed temperature and at the initial 

boiling point can be used in the equation. Integration of 

this equation then yields: 

 

 

 

s f

i s Bp

t tW Cp
Δ z ln

U t tiD

 
  

 
 

                       (7) 

 
Equation (7) thus determines the required height or length 

(z) of the preheating section.  

Once boiling commences, the boildown ratio function 

developed previously enters into the calculations. The 

temperature of the solution stream is incremented in 

uniform step sizes of (t). The mass flow rate in (kg/h) 

of this stream at any temperature greater than the initial 

boiling point is computed from the boildown ratio as 

follows: 

 

25ρ FW
BDR

                                                                  (8) 

and 

F
25

25

ρ F
F

ρ
                                                (9) 

 The rate of water vaporized over the z 

increment corresponding to the temperature increase t is 

then given by: 

   t t tV W W                                  (10) 

The enthalpy balance equation in this section 

has one additional output term (Smith & Van Ness, 

1987).  

Rate of Input H q                                   (11) 

v
d H

Rate of Output H z r H z
d z

 
     

 
          (12) 

where  

d V d W
r

d z d z
                                 (13) 

Subtracting the output term from the input term and 

equating the difference to zero, 

v
d H

q z r H z
d z

 
    
 

                            (14) 

Or 

 
 p R

i i s v

d W C t t
U a t t z z r H z 0

d z

 
 

             (15)

  



Simulation of Wiped Film Evaporator 

 

46 
IJCPE Vol.9 No. 2 (June 2008) 

 

Again neglecting any change in Cp over an increment 

then:  

   i i s p p R v
d t

U a t t W C C t t r r H 0
d z

           (16) 

                                                                              

Thermodynamically, however, for water 

 v p RH C t t                   (17) 
Where ( is the heat of vaporization of water at the 

temperature t. 

Equation (16) can then be rewritten as 

 i i s p
d t

U a t t W C r 0
d z

                  (18) 

Using average values of the variable values of Ui, W, Cp 

and , based upon their values at beginning and end of 

the finite t increment, then equation (19) can be written 

in the following finite difference form: 

 
P

i i s

W C Δ t
Δz

U a t t λr


 
             (19) 

Finally, after approximating r with
Δz

ΔV
, equation (20) 

can be solved to yield the  

 
P

i i s

λ ΔV WC Δt
Δz

U a t t





             (20) 

This equation determines the increment height or length 

required to heat up the vaporized solution stream from t 

to (t+t) at which water is vaporized at the rate of ΔV  
kg/h.  

Experimental Work 

The liquids used in this work are non-ionic water 

supplied from Al-Mansour Factory and glycerol from 

Vegetable Oils Company. Different concentrations (10, 

30, and 50 wt % glycerol solutions) were prepared by 

weighing method. Liquid viscosities varied from 0.6-

135.5 mPa.s, these values were measured using a Fann V-

G meter (Baroid) at 50 °C, which was applicable for this 

range. Liquid densities varied from 985-1240 kg/m3. 

These values were found by measuring the mass of a 

known volume (Pycnometer) at 50 °C. 

Saturated steam, supplied from a fire tube steam 

generator, with different pressure (2-5 atm) was used as 

the heating media in the jacket of the evaporator. 

Tap water (flowing at a pressure of 2 atm gauge and 

ambient temperature) was used as the cooling media in 

heat exchanger, sealing ring of the vacuum pump and the 

rotary shaft. 

Experiments were carried out in wiped film evaporator 

supplied from ALVAL Engineering Company. The 

evaporator consisted from the following parts: 

-Main body of evaporator (STRATAVAP Model 8005).  

-Graduated glass bottom. 

-Separator cyclone. 

-Condenser. 

-Knock-out pot. 

-Rotor drives (STRATAVAP Rotor). 

-Vacuum pump (water ring sealing type). 

-Different types of pumps for transfer solutions. 

The equipment was erected on a steel structure supplied 

with an electrical board for controlling and operating the 

different parts of the system. The system's utilities 

included steam supply, electrical stock and cooling water 

for sealing and cooling were all connected to the system. 

The main body of evaporator consisted of a jacketed 

cylinder with an inside diameter of 25 cm and active 

length of 116 cm made of stainless steel 316 L; the jacket 

was made from the same material with steam inlet pipe 

and outlet pipe for the condensate. The steam feeding 

pipe to the jacket had an inside diameter of 2.54 cm made 

from carbon steel with a regulating valve to control the 

pressure of steam in the jacket. As for the outlet pipe, it 

was made from carbon steel having the same diameter 

connected to a steam trap to permit the condensate steam 

only to exit from the jacket.  

In the top of main body of the evaporator a motor with a 

gearbox was installed to reduce the speed, fitted with 

belts to transfer rotation from motor to rotor parts of 

evaporator. The rotor part consisted of a shaft along the 

active part of the evaporator with a hung wiper equipped 

vertically to the shaft. A mechanical seal in the entrance 

of the shaft to the system existed to prevent the leakage 

of gases and vapors from the evaporator. At the end of 

evaporator a graduated glass dish bottom end was 

installed to collect the produced concentrated solution.  

 

Table 1 Experimental Result. 

Run  

No. 

Feed 

Conc. 

(Wt. 
%) 

Pressure 

Depression 

(mmHg) 

Steam 

Pressure 

(atm) 

Feed 

Flow 

Rate 
(l/h) 

       Final 

concentration 

    (Wt %) 

1.  10 40 4 50 95 

2.  10 40 4 30 98.5 

3.  10 100 4 80 94 

4.  10 100 4 100 89 

5.  10 180 4 120 41 

6.  30 40 4 30 99.4 

7.  30 40 4 50 99.5 

8.  30 120 4 100 95 

9.  10 60 2 30 97 

10.  10 100 2 50 94 

11.  10 100 2 80 58 

12.  10 180 2 100 26 

13.  50 40 4 80 99.1 

14.  50 40 4 100 99 



Adil A. Al-Hemiri, Emad F. Mansour and Jamal A.L. Al-Ani  

 

47 
IJCPE Vol.9 No. 2 (June 2008) 

 

Results and Discussion 

 

The effect of operating parameters on the performance of 

wiped film evaporator was studied using a simulation 

software. The studied parameters included: pressure 

depression, saturated steam pressure and feed volumetric 

flow rate. Experiments were performed using different 

concentrations of glycerol-water solution (10-50 wt. %) 

and different feed flow rate (30-120 l/h). The results of 

the experiments conducted in the present study are given 

in table(1). 

   The simulation program was proven to be successful by 

comparing with randomly selected practical experiments. 

Where statistical analysis showed that the average 

absolute error, F-test and correlation coefficient of  

2.25%, 0.997 and 0.964 respectively.   

     During the experimentation and analysis, two distinct 

zones were recognized; preheating and evaporation. The 

preheating zone did not exceed 10% of the total 

evaporator length for all cases studied.  

      

Effect of Pressure Depression 

 Five levels of pressure depression were chosen; these 

values were 80,120,160,200 and 400 mm Hg (for a 

rotation speed of 480 rpm and a steam pressure of 4 

atmospheres). 
   The effect of pressure depression on the final 

concentration of glycerol and the influence of feed 

volumetric flow rate is shown in figure (1). It can be 

seen, as it should be, that the final concentration of 

glycerol increases with increasing the vacuum, i.e. 

lowering pressure depression. As the flow rate is 

increased the effect of pressure depression seems to be 

less effective. A decrease in the final concentration is 

noticed as the flow rate is increased (beyond 50 l/h) for 

all pressure depression levels , but it was , practically, 

constant below that. Similar results were obtained by 

Chawankul et al (2001) who studied the concentration of 

orange juice experimentally and compared the results 

with a simulation software using ASPEN PLUS. 

     Figure (2) shows the axial distribution of the overall 

heat transfer coefficient at the two extreme values of 

pressure depression used (80 and 400 mm Hg) for a feed 

flow rate of 100 l/h, a rotation speed of 480 rpm and a 

steam pressure of 4 atmospheres. It can be seen that the 

overall heat transfer coefficient increased with increasing 

pressure depression and a maximum value was noticed at 

the point separating the preheating zone from the 

vaporization zone (5-10 cm. from entry). This is due to 

the decrease in the thermal conductivity of vapors 

compared to liquids. 

 

 

 

Effect of Steam Pressure 

      The effect of steam pressures (2, 3, 4 and 5 atm.) on 

the final concentration for different flow rates is shown in 

figure (3). These results were obtained at 480 rpm and 80 

mm Hg pressure depression. It can be observed that the 

final concentration increased with increasing steam 

pressure due to the increase of the temperature difference 

between the utility side (steam side) and the feeds side 

that caused enhancement of the evaporation rate. At low 

feed flow rate (below 50 l/h) the effect of steam pressure 

was not significant but increasing the feed flow rate 

beyond 100 l/h had caused the effect of steam pressure to 

be less pronounced. 

    Comparison of the effect of steam pressure with that of 

pressure depression, show that the effect of the latter, as 

expected, is sharper and more significant. 

    Figure (4) shows the axial distribution of the overall 

heat transfer coefficient at the extreme cases of steam 

pressure used (2 and 5 atm.). The results show that the 

overall heat transfer coefficient increased with decreasing 

steam pressure; this is due to the fact that at the lower 

pressure, the temperature difference is larger. 

 

 Effect of Rotation Speed 

      Figure (5) illustrates the effect of the speed of rotation 

and feed flow rate on the final concentration of glycerol.  

Results indicate that increasing the feed flow rate caused 

in decreasing the final glycerol concentration and that 

increasing the speed of rotation caused significant 

increase in the final concentration; this increase was 

noticed to be lower at high feed flow rate. Similar results 

were found by Komori et al (1988). 

      The effect of the speed of rotation on the axial 

distribution of the overall heat transfer coefficient is 

illustrated in figure (6). The figure show that the heat 

transfer coefficient reached a maximum at the point 

separating the preheating zone from the evaporation zone 

and it increased with increasing the speed of rotation. 

However the effect of the rotational speed was found to 

be less pronounced than the other parameters considered. 

These results were obtained for 480 rpm, 4 atm steam 

pressure and 100 l/h feed flow rate.  

 

 

 

 

 

 

 

 

 

 



Simulation of Wiped Film Evaporator 

 

48 
IJCPE Vol.9 No. 2 (June 2008) 

 

Volumetric flow rate, l/h

0 100 200 300 400 500

F
in

a
l 
C

o
n
c
e
n
tr

a
ti
o
n
, 
w

t.
 %

0

20

40

60

80

100

2 atm

3 atm

4 atm

5 atm

Fig. 1: Final concentration varies flow rate at different     

pressure depression 

 

 

Volumetric flow rate, l/h

40 60 80 100 120 140 160 180 200 220

F
in

a
l 
c
o

n
c
e

n
tr

a
ti
o

n
, 
w

t.
 %

0

20

40

60

80

100

80 mm Hg

120 mm Hg

160 mm Hg

200 mm Hg

400 mm Hg

 

Fig. 1, Final concentration versus flow rate at different pressure depression 

 

Evaporator length, cm

0 20 40 60 80 100 120

U
, 

W
/m

2
 K

400

500

600

700

800

900

1000
80 mm Hg

400 mm Hg

 

Fig. 2, Axial distribution of overall heat transfer coefficient at different 

pressure dispersion (feed flow rate = 100 l/h) 

 
Fig. 2: Axial distribution of over all heat transfer 

coefficient at different pressure dispersion (Feed flow 

rate =100 l/h) 

Volumetric flow rate, l/h

0 100 200 300 400 500

F
in

a
l 
C

o
n
c
e

n
tr

a
ti
o

n
, 
w

t.
 %

0

20

40

60

80

100

2 atm

3 atm

4 atm

5 atm

 
Fig. 3: Final concentration versus flow rate at 

different steam pressure 

 

Fig. 4: Axial distribution of overall heat transfer 

coefficient at different steam pressure (feed flow rate = 

100 l/h) 

Fig. 5: Final concentration versus flow rate at 

different RPM 

 

 

 

 

 

 

 

 

 

 

 

 
Fig. 6: Axial distribution of overall heat transfer coefficient 

at different RPM (feed flow rate = 100 l/h) 

 

 

Evaporator length, cm

0 20 40 60 80 100 120

U
, 
W

/m
2
 K

400

500

600

700

800

900

1000
2 atm

5 atm

Volumetric flow rate, l/h

0 100 200 300 400 500

F
in

a
l 
C

o
n
c
e
n

tr
a

ti
o

n
, 
w

t.
 %

0

20

40

60

80

100

120 RPM

240 RPM

480 RPM

960 RPM

Evaporator length, cm

0 20 40 60 80 100 120

U
, 

W
/m

2
 K

200

400

600

800

1000

1200
120 RPM

960 RPM



Adil A. Al-Hemiri, Emad F. Mansour and Jamal A.L. Al-Ani  

 

49 
IJCPE Vol.9 No. 2 (June 2008) 

 

CONCLUSIONS 
       The required height or length (z) of the preheating 

section was shown to be estimated using equation (7). 

       The equation that determines the increment height or 

length required to heat up the vaporized solution stream 

from t to (t+t) at which water is vaporized at the rate of 

ΔV  kg/h is given by equation (20). 
       The success in applicability of the designed 

simulation program was proven by the comparison with 

randomly selected practical experiments. Statistical 

analysis of the comparison showed that the average 

absolute error, correlation coefficient and F-test were 

2.253 %, 0.997, and 0.964 respectively. 

       Two distinct zones of operation were observed; 

preheating and evaporation. And at the point of separation 

of these two zones the value of heat transfer coefficient 

reached a maximum. The range of the overall heat transfer 

coefficient observed in this study was 176-1263 W/m
2 0

K. 

       Increasing the pressure depression decreased the final 

concentration of the product but increased the heat 

transfer coefficient.  

       Altering the steam pressure did not affect the final 

concentration significantly, but increasing it caused a 

lowering in the value of the heat transfer coefficient. 

      Increasing the speed of rotation increased the final 

concentration and, also, increased the heat transfer 

coefficient, where a 66% increase was observed when 

increasing the speed from 120 to 960 rpm.   

 

 

Nomenclature 

 
a : Heat transfer area                               m

2   
 

BDR : Boil down ratio                             --- 

Cp : Specific heat of fluid                   kJ/kg
 0
K 

D : Column diameter                                m 

F : Mass flow rate                                     kg/s 

      h : Heat transfer coefficient                    kJ/m
2 
s

 0
K                

H : Heat input by flow of fluid stream       kJ/s 

K : Thermal conductivity                       kJ/m
3
 s 

0
K                   

L : Thickness                                              m 

q : Heat input by conduction through wall    kJ/s 

 r :Defined by equation (13)                      kg/ms 

t : Temperature                                          
°
 K 

U : Overall heat transfer coefficient         kJ/m
2 
s 

0
K                  

V : Rate of vaporization                              kg/s 

W : Flow rate defined by equation (8)        kg/s 

 z : Column height                                        m 

Greek Letters 

     λ : Latent heat of vaporization                    kJ/kg 

     ρ : Density                                                  kg/m
3
  

     π : Pi                                                            ---- 

Subscripts    

Bp : Boiling point 

F : Fluid 

i : Inside 

o : Outside 

R : Reference 

      s : Steam 

      v : Vapour 

      w : Wall 

      25 : At 25 
°
C  

                         

REFERENCE 

 
1. Abichandani H., Sharma S.C., and Heldman D.R., 

(1987) “Hydrodynamics and Heat Transfer in 

Thin Film Scraped Surface Heat Exchanger: 

A Review”, Journal of Food Process 

Engineering, 9, 143-172.  

2. APV Company, "Evaporator Handbook", 
(2000) 4

th
 Edition, EHB-955, www.apv.com. 

3. Chawankul N., Chuaprasert S., Douglas P.L. and 
Luewisutthichat W., (2001) "Simulation of an 

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