heat transfer in canned liquid/particle mixtures subjected to axial agitation thermal processing...
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Heat Transfer in Canned Heat Transfer in Canned Liquid/Particle Mixtures Subjected To Liquid/Particle Mixtures Subjected To
Axial Agitation Thermal ProcessingAxial Agitation Thermal Processing
Department of Food Science and Agricultural ChemistryMcGill University
July 15 , 2008
CSBE Conference
Mritunjay Dwivedi & H.S. Ramaswamy
Most efficient method of food preservation
Principles of thermal processing:
Safety and shelf stability
Reduce the number of microorganisms of public health concern
Create an environment to suppress the growth of spoilage microorganisms
IntroductionIntroduction
Thermal ProcessingThermal Processing
Today the Consumer demands more than safe and self stable product
High Quality Convenience in end use
Introduction
Processors demand technology which is More efficient Cost effectiveHigh speed in natureHTST process is designed to meet the aforementioned processors and consumers demand
Minimizing the severity of heat treatmentPromoting product quality
Aseptic processing and Packaging (1)
Three Major developments in HTST processing
Thin Profile Packaging and Processing (2)
Three Major developments in HTST processing
Rotational retorts
Processing (3)
Three Major developments in HTST processing
Two Different Modes of Rotation in Agitation retorts
mg
mg
mg
mgmg
Axial Rotation (Continuous Operation) End over end rotation (Batch Operation)
Rotational Modes
Several Studies Conducted in End Over End Agitation
Processing
But very little information is available on axial agitation
processing
U and hfp
are commonly used
to quantify the heat
transfer process.
U : Overall heat transfer coefficient
hfp: Fluid to particle heat transfer coefficient
U
hfp
RetortLiquid
Particle
Process Parameters
Heat transfer in free axial agitation is it difficult
Attaching temperature sensors
Collection of data
Knowledge of U and hfp is important in predicting the particle center lethality
Overall ObjectiveOverall Objective
The overall objective of this presentation is to
carry out a detailed evaluation of heat transfer
to canned particulate fluids under rotary
processing
Heat transfer studies of particle-liquid mixtures canned foods in free axial mode
Modification of Stock rotomat similar to FMC steritort
CAGE
Attachments
RETORT SHELL
CAN
Detail – Attaching Cans in Axial Mode of Rotation
Modification of Stock RetortModification of Stock Retort
MethodologyMethodology
SUS Attachment
shellCage
32 Circuit HUB
S-28 NR rotating thermocouple
Tl
TlTl
Placement of cans in EOE and Axial Mode
EOE vs Free vs Fixed Axial
Heat transfer studies of particle-liquid mixtures canned foods in free axial mode
Modification of Stock rotomat similar to FMC steritort
Compare heat transfer rates between Axial and EOE mode
To data
logger
S-28 Ecklund Thermocouple
Results and Discussions
Development of a suitable methodology to measure
convective heat transfer coefficients in free axial mode
Ufixed hfpfixed Ufree hfpfree
273 575 491 759
146 245 564 947
152 316 462 697
256 476 563 875
136 227 356 572
145 259 474 790
279 589 360 496
142 243 478 706
210 390 581 945
345 719 395 653
191 314 455 777
199 405 458 629
344 632 343 637
189 307 527 886
198 348 450 759
381 797 450 788
201 337 454 726
246 449 452 785
185 298 445 779
81 115 448 761
Models (U & hfp Vs for free axial mode)
+Liquid temperature Data from wireless sensors (Free Axial)
Overall energy balance equation
22 123.903.2
875.446.3394.32776.00159.281
RC
RCRCTU ModeAxialFixed
22
......
78.582.1
581.5546.5575.2489.461
RC
RCRCTh ModeAxialfixed
U & hU & hfp (Free axial Mode)(Free axial Mode)Methodology to U & hfp
Results and Discussions
Evaluation of the effects of system parameters on heat transfer
coefficients with Newtonian fluids during axial rotation
Free Vs. Fixed Axial ModeEffect on hfp
Free Vs. Fixed Axial ModeEffect on hfp
0
100
200
300
400
500
600
700
800
900
1000
20 30 40
Particle Concentration (%)
hfp
(W/m
2K)
φ19 mm φ 22.25 mm φ 25 mm
Free Axial ModeEffect of Particle size and Conc. on U & hfp
Free Axial ModeEffect of Particle size and Conc. on U & hfp
0
100
200
300
400
500
600
700
800
900
20 30 40
Particle Concentration (%)
hfp
(W
/m2 K
)
Polypropylene Nylon Teflon
Free Axial ModeEffect of Particle density and Conc. on U & hfp
Free Axial ModeEffect of Particle density and Conc. on U & hfp
Results and Discussions
Dimensionless correlations for convective heat transfer
to canned liquid particulate mixture subjected to axial and
end-over-end rotations under natural and forced convection
Dimensionless correlations set up
Neural network models set up
Parameters Experimental range
Retort Temperature
Rotation speed
Can headspace
Test liquids
Test particles
Particle Size
Particle concentration
111.6,115,120, 125,128.40C
4,8,14,20,24 rpm
5 mm and 10 mm
Newtonian: 80,84,90,96,100 % glycerin solution
Polypropylene, Nylon and Teflon
0.019, 0.02225 and 0.254 meters
20 %, 30 % and 40 %
Dimensionless GroupsDimensionless Groups
Description Relationship Significance
Reynolds number
Visualize the flow characteristics of a liquid
Prandtl number Thickness of hydrodynamic to thermal
boundary layer (ν/α)
Nusset Number Heat transfer caused by convection
Froude number Resistance of an object
moving through liquid Grashof Number Flow characteristics over
an object
k
cP pr
k
hdNu ch
g
NdFr ch
2
2
3)(
chs dTTg
Gr
chud
Re
Regression Analysis usedRegression Analysis usedRegression Analysis usedRegression Analysis used
A multiple linear regression analysis for developing forced convection correlations
A step-wise multiple non-linear regression analysis was used to develop the mixed convection dimensionless correlations
Description Pure Forced Mixed Convection
R2 SS R2 SS
Free Axial U, with particle
0.85 213947 0.92 175873
Fixed Axial U, with particle 0.84 115585 0.93 84388
Free Axial hfp, with particle 0.80 180504 0.90 99453
Fixed Axial hfp, with particle 0.81 247587 0.95 126434
Free Axial U, without particle 0.96 39132
EOE, U without particle 0.81 577.57 0.97 224
Nu = A1 ( GrPr) A2 + A3 (ρp/pl )A5, (dp/Dc)A6, Re A7, Fr A8, PrA9, PCA10
Free Convection
Forced Convection
Fixed Axial Mode - With particles Free Axial Mode - With particles
hfp U hfp U
DC ANN DC ANN DC ANN DC ANN
MRE (%) 10.24 2.6 8.62 2.9 8.3 1.85 7.35 2.5
R2 0.92 0.98 0.92 0.97 0.95 0.99 0.95 0.98
End over end mode Free Axial Mode
U U
DC ANN DC ANN
MRE (%) 6.05 3.81 8.34 2.06
R2 0.97 0.98 0.95 0.99
Comparisons of errors for ANN models vs. Dimensionless correlations for liquid with particulates
Comparisons of errors for ANN models vs. Dimensionless correlations for liquid without particulates
Modification of the existing cage of the pilot stock rotomat was successful
Conclusions
U was significantly higher in case of axial mode than in EOE mode of agitation, contrary to study made
by Naveh and Kopleman (1980)
A methodology was developed for the measurement of U and hfp
subjected to free axial agitation.
With an increase in rotational speed, particle density and retort temperature,
there was an increase in the associated hfp and U values
T-Test showed no significant difference between the performance of standard thermocouples and wireless sensors.
Conclusions
Dimensionless correlations for mixed and pure forced convection were developed with and without particulates in Newtonian fluids during all modes of agitation
Higher coefficients of correlations showed that in all forced convection situations, the natural convection phenomenon continues to operate because of buoyant forces.
ANN models yielded better results those from the dimensionless correlations.
Thank YouThank You
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