Professor Barry Crittenden
Department of Chemical Engineering
University of Bath, Bath, UK, BA2 7AY
INTENSIFIED HEAT TRANSFER TECHNOLOGIES FOR ENHANCED HEAT RECOVERY - INTHEAT
INTHEAT KICK-OFF MEETING 17 DECEMBER 2010
INTHEAT KICK-OFF MEETING 17 DECEMBER 2010
1. Bath and its University
2. INTHEAT work packages
3. Experimental capability
4. CFD capability
5. Fouling & threshold model capability
6. Compensation plot
OUTLINE
INTHEAT KICK-OFF MEETING 17 DECEMBER 2010
Population 85,000(with two Universities)
UNESCO World Heritage City
Excellent transport links
40 km from Bristol International Airport
160km west of London
CITY OF BATH
INTHEAT KICK-OFF MEETING 17 DECEMBER 2010
Received Charter in 1966
Located on a hill overlooking the City of Bath
13,000 students, including 3,400 international students
from over 100 countries
THE UNIVERSITY OF BATH
Modern campus-based university on a 81 hectare site
Consistently within the top 10 UK universities in national league tables
Research-driven, with high quality teaching and a small, friendly campus
Three Faculties:Engineering & Design
Science Humanities & Social Science
&School of Management
Department of Chemical Engineering
(9 West)
INTHEAT KICK-OFF MEETING 17 DECEMBER 2010
Work Package
Title Months(Bath)
WP1 Analysis of intensified heat transfer under fouling*
14
WP2 Combined tube-side & shell-side heat exchanger enhancement
1
WP3 Heat exchangers made of plastic material 0
WP4 Design, retrofit and control of intensified heat recovery networks
9
WP5 Putting into practice 4
WP6 Technology transfer 4
WP7 Project management 0
INTHEAT WORKPLAN TABLES
* Lead: Bath
INTHEAT KICK-OFF MEETING 17 DECEMBER 2010
Overall objective: Enhancing our understanding of heat exchange under fouling
▪ To develop an advanced CFD tool to improve the heat exchanger performance by adjusting both operating conditions and equipment geometry
▪ To gain in-depth understanding of fouling mechanisms and kinetics of fouling through experiments
Task 1.1: Experimental fouling investigation
Task 1.2: CFD research on heat transfer
Task 1.3: Testing of possible anti-fouling additives
Deliverable D1.1: Report on technical review of fouling and its impact on heat transfer (Month 3)
Deliverable D1.2: Report on experimental fouling investigation and CFD research on
heat transfer enhancement (Month 12)
Participant Short name Person-months
1 PIL 1.5
2 CALGAVIN 4
3 SODRU 2.5
4 MAKATEC
5 OIKOS
6 UNIMAN 3
7 UNIBATH 14
8 UPB 2
9 UNIPAN 6
10 EMBAFFLE
Total 33
INTHEAT WORK PACKAGE 1
INTHEAT KICK-OFF MEETING 17 DECEMBER 2010
FOULING CAN BE VERY COMPLEX AND EXPENSIVE
INTHEAT KICK-OFF MEETING 17 DECEMBER 2010
23
0 m
m a
ppro
xim
ate
ly
t wb t ws
t bulk
INS
UL
AT
ION
INS
UL
AT
ION
© 2008 University of Bath, England
t wm
Fil Level
Finger (Mild Steel)BS 070M20
Section A-A
26.00 Ø
73
.00
twm
twb
tws Hea
ted
Re
gio
n0
– 60
0 W
Heat Flux0 – 120 kW m2
Fouling Region
19.00
A A
Up to 30 bar
Up to 300oC bulk
Up to 400oC surface
Up to 120 kW/m2 flux
q
TTR sostf
EXPERIMENTAL FACILITY
INTHEAT KICK-OFF MEETING 17 DECEMBER 2010
TYPICAL FOULING CURVE (CRUDE B, ≈ 6 WT% ASPHALTENE)
-0.02
0
0.02
0.04
0.06
0.08
0.1
0.12
0 1 2 3 4 5 6 7
Time (hours)
Rf
m
2 K
kW-1
Rf Petronas (b) - Asphaltene 6 % wt
Linear (y = 0.0181x - 0.021 R2 = 0.9193)
-
http://www.imperial.ac.uk/crudeoilfouling20 February 2008
B.D.Crittenden, M.Yang, A.Young & W. Hall
NB tso ≈ 375 ºC,tbulk= 260 ºC
Shear Stress ≈ 0.5 Pa
= 5.0 E -06 m2 K kJ -1
Stirred cell conditions: 500 W & 200 rpm (Tso≈ 375oC; Reynolds Number = 12700)
For comparison: BP Rotterdam; Downey et al., 1992
Initial fouling rate = 3.5 E-07 m2K kJ-1;Tso = 260oC; Re = 30,000
INTHEAT KICK-OFF MEETING 17 DECEMBER 2010
ARRHENIUS PLOT FOR PETRONAS B (@ 200 RPM)
y = -5.9629x - 3.2528R2 = 0.9182
-12.8
-12.6
-12.4
-12.2
-12
-11.8
-11.6
-11.4
1.4 1.42 1.44 1.46 1.48 1.5 1.52 1.54 1.56 1.58 1.6
ln (
dR
fo/d
t)
EA = 49.47 kJ mol-1
ln (dRf / dt) = A – E/RT
1000/T (K)
INTHEAT KICK-OFF MEETING 17 DECEMBER 2010
EFFECT OF SURFACE SHEAR STRESS ON FOULING RATE (CRUDE A)
Shear stresses are obtained by CFD simulation for different stirring speeds
-1.00E-08
-8.00E-09
-6.00E-09
-4.00E-09
-2.00E-09
0.00E+00
2.00E-09
4.00E-09
6.00E-09
8.00E-09
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8
Surface shear stress (Pa)
dR_f
/dt (
m^2
K J^
-1)
600 K 610 K 620 K 630 K 640 K 650 K 660 K
Increasing the wall shear stress decreases the rate of fouling for any given surface temperature.
Negative fouling with existing deposits can occur for low surface temperatures and high surface shear stresses; this means fouling deposit being removed by surface shear stress.
INTHEAT KICK-OFF MEETING 17 DECEMBER 2010
PETRONAS B: 2D CFD SIMULATION FLOW & TEMPERATURE FIELDS
200 rpm, 500W, 106 kW/m2
Streamlines are shown in both gas and oil phases
INTHEAT KICK-OFF MEETING 17 DECEMBER 2010
SIMULATION FOR ACTUAL 3-D GEOMETRY
Petronas B, 500W, average heat flux: 106 kW m-2, 200 rpm
Velocity field Temperature field
INTHEAT KICK-OFF MEETING 17 DECEMBER 2010
Velocity field
Z (flow direction)
0 0.013
Tube (19mm ID) with medium density inserts (hiTRAN)
Linear flow rate: 1m/s, bulk temperature: 423K
Vertical slice
CFD SIMULATION FOR FLUID FLOW IN TUBE WITH INSERTS
INTHEAT KICK-OFF MEETING 17 DECEMBER 2010
WALL SHEAR STRESS DISTRIBUTION
0.00
10.00
20.00
30.00
40.00
50.00
60.00
0 0.002 0.004 0.006 0.008 0.01 0.012 0.014 0.016
Position in z direction
Sh
ea
r s
tre
ss
(P
a)
0.5m/s 0.7m/s 1m/s 1.5m/s
Shear stress data are obtained from the velocity gradient and the turbulent viscosity by CFD simulation
Z position begins at just behind the loop edge, ends at the same position of the next loop
INTHEAT KICK-OFF MEETING 17 DECEMBER 2010
PARTICLE SEDIMENT TEST AT CAL GAVIN
Sediments seem to form behind the loop where the shear stress is a minimum
INTHEAT KICK-OFF MEETING 17 DECEMBER 2010
EQUIVALENT VELOCITY CONCEPT FOR ENHANCED SURFACES
Equivalent velocity = 0.2461x2 + 1.1369xR2 = 0.999
00.5
1
1.52
2.53
3.5
44.5
5
0 0.5 1 1.5 2 2.5 3
Velocity - Tube w ith inserts (m/s)
Eq
uiv
alen
t b
are
tub
e ve
loci
ty (
m/s
)
0
5
10
15
20
25
30
35
40
45
Sh
ear
stre
ss (
Pa)
■: Velocity; ¤: Shear stress
Obtain equivalent bare tube velocity by matching surface shear stress of enhanced surface with that of a bare tube
Example: hiTRAN medium density insert
INTHEAT KICK-OFF MEETING 17 DECEMBER 2010
APPLICATION OF THE MODEL DEVELOPED FOR FOULING IN BARE TUBE TO TUBE WITH INSERTS
▪ Modified Yeap’s model – replace the velocity in the fouling suppression term with wall shear stress. This model is capable of modelling the effect of velocity more accurately including the velocity maximum behaviour seen for Maya crude
▪ Using equivalent linear velocity in the fouling growth term:
▪ Adopting the concept of equivalent linear velocity would allow the fouling data obtained from experiments with bare tubes to be used for prediction of the fouling in tubes with inserts.
wm
ssfm
sfmf CRTETCuB
TuCA
dt
dR
)/exp(1 3/23/13/123
3/43/23/2
INTHEAT KICK-OFF MEETING 17 DECEMBER 2010
MODEL APPLICATION
0.00001
0.0001
0.001
0.00001 0.0001 0.001
Actual fouling rate (Km2/wh)
Pre
dic
ted
fo
uli
ng
rate
(K
m2/w
h)
Experimental data using Maya crude oil in both a bare tube and a tube fitted with medium density hiTRAN insert (Crittenden et al. 2009).
Activation energy E = 50.2 kJ/mol by curve fitting
INTHEAT KICK-OFF MEETING 17 DECEMBER 2010
THRESHOLD CONDITIONS
For a bare tube and tube fitted with an insert
500
510
520
530
540
550
560
3.00 3.50 4.00 4.50 5.00
Velocity/Equivalent velocity (m/s)
Th
resh
old
tem
per
atu
re (
K)
Experimental Model predicted
Experimental data using Maya crude in bare tube and tube fitted with medium density insert (Don Phillips 1999).
INTHEAT KICK-OFF MEETING 17 DECEMBER 2010
COMPENSATION PLOT FOR ALL CRUDE OIL FOULING
-20
-10
0
10
20
30
40
50
0 50 100 150 200 250 300
EA (kJ mol-1)
ln[A
(m2 K
/ kJ
)]Crude ACrude BMaya crude oil (Crittenden et al. 2009)Kuwaiti crude oil (Bennett et al. 2009)Desalted crude oil (Knudsen et al. 1999)Shell Westhollow crude oil (Panchal et al. 1999)Exxon refinery crude oil (Scarborough et al. 1979)Shell Wood River crude oil (Panchal et al. 1999)
baEAn A
□: New points added – Crude A
Whether the effect is “true” or “false” is not known at present but is probably “false”.
Crittenden B D, Kolaczkowski S T, Takemoto T and Phillips D Z, Crude oil fouling in a pilot-scale parallel tube apparatus, J Heat Transfer Eng, 30: 777-785, (2009)
INTHEAT KICK-OFF MEETING 17 DECEMBER 2010
ISSUES RELATING TO APPARENT ACTIVATION ENERGY
Apparent activation energies increase with increasing wall shear stress (ie with velocity & Re).
Phenomenon has been observed before for reaction and crude oil fouling systems:
Crittenden B D, Hout S A, Alderman N J, Model experiments of chemical reaction fouling, TransIChemE 65A: 165-170, (1987).
Crittenden B D, Kolaczkowski S T, Takemoto T and Phillips D Z, Crude oil fouling in a parallel tube apparatus, J Heat Transfer Eng 30: 777-785, (2009).
Bennett C A, Kistler R S, Nangia K, Al-Ghawas W, Al-Hajji N and Al-Jemaz A, Observation of an isokinetic temperature and compensation effect for high temperature crude oil fouling, J Heat Transfer Eng 30: 794-804, (2009).
Young A, Venditti S, Berrueco C, Yang M, Waters A, Davies H, Hill S, Millan M and Crittenden B D, Characterisation of crude oils and their fouling deposits, J Heat Transfer Eng (in press, 2011).
Apparent activation energies increase also with fouling threshold temperatures.
Threshold fouling models must use apparent activation energies; if actual activation energies are used then they must be modified using shear stress (or velocity or Re) such as Ebert & Panchal.
This begs the question: how can the actual activation energy be determined for use in the Ebert & Panchal, Epstein, and Yeap models?
INTHEAT KICK-OFF MEETING 17 DECEMBER 2010
CONCLUSION
Batch stirred cell can be used to provide crude oil experimental data under various conditions of bulk temperature, surface temperature and surface shear stresses. Threshold conditions can be obtained. Chemicals can be added but long-term non-fouling experiments are not desirable. Within limits, the cell can be used with enhanced surfaces.
3-D CFD modelling allows predictive study of geometric changes including the use of enhanced surfaces.
Using the concept of equivalent velocity, a model that has been validated for a bare tube can then be applied to a tube with enhanced surfaces. Moreover, the fouling threshold conditions can be predicted.
Temperature and heat flux distributions can also be simulated by CFD.
Enhanced external surfaces need to be studied in much the same way. Some experimental validation would, in principle, be possible by adding a simple enhancement to the heat transfer surface of the batch stirred cell.
INTHEAT KICK-OFF MEETING 17 DECEMBER 2010
QUESTIONS?