Processing of liquid foods using UV Taylor-Couette flow reactor

VISHWESH KELKAR TATIANA KOUTCHMA BRIAN PARISI NATIONAL CENTER FOR FOOD SAFETY & TECHNOLOGY ILLINOIS INSTITUTE OF TECHNOLOGY CHICAGO Performance characterization of Taylor-Couette Flow UV Reactor (TCFR) for liquid foods

Performance characterization of Taylor-Couette Flow UV Reactor (TCFR) for liquid foods
What is a Liquid Food?
a. Definition
b. Types of liquid foods
1. Newtonian fluids
2. Non-Newtonian fluids
Food Safety
a. Center for Disease Control (CDC)
b. US Food and Drug Administration
21 CFR 120

Ultraviolet Irradiation
a. Definition – Waves which range between wavelengths of 200 to 400nm and can be further divided into UVA (320-400 nm), UVB (280-320 nm) and UVC (200-280 nm) are called Ultraviolet (UV) radiation.
b. Working Mechanism –
- DNA of cell of a sequence of four constituent bases known as purines and pyrimidines linked together in a double- stranded helix.
- When UVC radiation is absorbed by the pyrimidine bases it permits a unique photochemical reaction, which leads to dimerization of adjacent pyrimidines
- Disruption in the structure of the DNA makes it unable to
replicate and hence results in inactivation of microbial cell.
Eλ, radiant energy at a given wavelength λw, kJ/Einstein;
C , speed of light, 3×10 8 m/s;
h , Planck's constant, 6.626×10 -34 J·s;
Av , Avogadro's number, 6.023×10 23 photons/Einstein.

Taylor Couette Flow:
Flow of fluid in the gap between two infinitely long concentric cylinders, on or both of which are rotating along their common axis is called as Taylor-Couette flow.
G.I.Taylor found that a parameter known as Taylor number rises above a threshold value of 1708, and the gap between the cylinders is much smaller than radii, the flow is unstable.
The streamlines of low Taylor number Taylor-Couette flow are
circular. Following figure is a flow from a radial viewpoint
Once the flow becomes unstable, it is dominated by large toroidal
vortices, stacked one on top of the other, called Taylor vortices.
Taylor Number is given by,

Taylor-Couette Flow Reactor (TCFR)
-- Arrangement consists of two concentric cylinders, with inner rotating called rotor and outer stationary as stator.
-- Liquid flows through the annulus of rotor and stator, with UV lamps arranged around the stator.
-- Flow in the Taylor Couette flow

Experimental Set-up

Experimentation
Following goals were defined for carrying ut performance characterization of the reactor.
1. Goal 1: Comparison of momentum transfer achieved using smooth surface rotor as against wavy surface rotor in Taylor-Couette laminar flow for test fluids
a) Tap water b) Food grade viscous liquid
2. Goal 2: Experimentation on processing of non-Newtonian and Newtonian liquid with the variations in the rotor type arrangement in the TCFR.

Goal 1: Comparison of momentum transfer achieved using smooth surface rotor as
against wavy surface rotor in Taylor-Couette laminar flow for water as a test
liquid.
Part [A]
To compare residence time and residence time distribution between smooth surface and wavy surface rotors.
Constant parameter: Liquid to be treated – Tap water.
Variable parameters: following, changing one at a time –
Shape of rotor i.e. smooth rotor and wavy surface rotor.
Rpm/ angular frequency of rotor.
Flow rate though annulus between rotor and stator.
Injection dye used: Food grade caramel liquid.

Standard Curve for calculation of caramel
Dye concentration
Performance characterization of Taylor-Couette Flow UV Reactor (TCFR) for liquid foods Std Dye Sample - Abs, A Conc.% Sample 1.375 1.695 1 0.32 0.4255 2 0.078 0.1064 3 0.019 0.0266 4

Part [A]
Results: - Smooth Surface Rotor
Performance characterization of Taylor-Couette Flow UV Reactor (TCFR) for liquid foods RPM/ Flow rate 100 150 200 0.04 lpm 70.05 ±0.1 60.58 ±0.1 57.97 ±0.1 0.06 lpm 54.49 ±0.2 51.31 ±0.15 51.07 ±0.5 0.08 lpm 50.88+0.14 50.10 ±0.1 49.90 ±0.1 RPM 100 150 200 Taylor no. 265.47 398.20 530.93 Gap width, d meter 0.0025 0.0025 0.0025 Angular Frequency Ω Rps 10.467 15.7 20.934

Part [A]
Results: - Smooth Surface Rotor

Part [A]
Results: - Wavy Surface Rotor
Performance characterization of Taylor-Couette Flow UV Reactor (TCFR) for liquid foods RPM/ Flow rate 100 150 200 0.04 lpm 61.43 ±0.1 63.55 ±0.16 69.72 ±0.1 0.06 lpm 55.02 ±0.1 55.21 ±0.2 55.90 ±0.1 0.08 lpm 47.59 ±0.05 47.67 ±0.2 48.91 ±0.2 RPM 100 150 200 Taylor no. 265.47 398.20 530.93 Gap width, d meter 0.0025 0.0025 0.0025 Angular Frequency Ω Rps 10.467 15.7 20.934

Part [A]
Results: - Wavy Surface Rotor

Part [A] – Smooth Rotor
Performance characterization of Taylor-Couette Flow UV Reactor (TCFR) for liquid foods Angular Frequency, Rpm Time, Sec Flow rate Flow rate Flow rate 0.04 lpm 0.06 lpm 0.08 lpm 100 70.05 54.49 50.88 150 60.58 51.31 50.10 200 57.97 51.07 49.90

Part [A] – Wavy Rotor
Performance characterization of Taylor-Couette Flow UV Reactor (TCFR) for liquid foods Angular Frequency, Rpm Time, Sec Flow rate Flow rate Flow rate 0.04 lpm 0.06 lpm 0.08 lpm 100 61.43 55.02 55.02 150 63.55 55.21 47.67 200 69.73 55.90 48.91

Goal 1: Comparison of momentum transfer achieved using smooth surface rotor as
against wavy surface rotor in Taylor-Couette laminar flow for food grade
liquid as a test liquid.
Part [B]
To compare residence time and residence time distribution between smooth surface and wavy surface rotors.
Constant parameters : Liquid to be treated – Food grade viscous liquid.
: Flow rate of 0.25 liter per min
: Angular frequency of 200 rpm
Variable parameters: following, changing one at a time –
Shape of rotor i.e. smooth rotor and wavy surface rotor.
Viscosity of the liquid.
Injection dye used: Food grade caramel liquid.

Part [B] – Smooth Rotor

Part [B] – Wavy Rotor

Part [B]
Viscosity cP Residence Time, Sec Wavy Smooth 43.20 58.72 49.97 63.20 80.70 70.93 81.40 95.49 89.32 106.60 123.83 115.36

Goal 2: Experimentation on processing of non-Newtonian and Newtonian liquid with the variations in the rotor type arrangement in the TCFR.
Part [A]
Non-Newtonian (viscous) semi-transparent liquid model will be inoculated with E. coli K 12
Constant parameters : Liquid to be tested: Food grade viscous liquid.
: absorbance of the viscous liquid to be treated
: angular frequency
Variable parameters: Changing one at a time
Shape of the rotor, i.e. smooth/wavy rotor
Flow rate through annulus/gap between rotor and stator.
Viscosity

Goal 2: Experimentation on processing of non-Newtonian and Newtonian liquid with the variations in the rotor type arrangement in the TCFR.
Part [B]
Non-Newtonian (viscous) semi-transparent liquid model will be inoculated with E. coli K 12
Constant parameters : Liquid to be tested: Tap water.
: absorbance of the viscous liquid to be treated
: angular frequency
Variable parameters: Changing one at a time
Shape of the rotor, i.e. smooth/wavy rotor
Flow rate through annulus/gap between rotor and stator.

Goal 2:
Following results were obtained based on the experimentation.
Microbial inactivation data using smooth and wavy surface rotors
Test Fluid Rotor Angular Frequency, Rpm Flow rate, liter/min Complete Inactivation Yes/No Viscous liquid 81.6 cP Wavy 100 0.25 Yes Viscous liquid 81.6 cP Wavy 200 0.25 Yes Viscous liquid 81.6 cP Smooth 100 0.25 Yes Viscous liquid 81.6 cP Smooth 200 0.25 Yes Viscous liquid 44.4 cP Wavy 200 0.25 Yes Viscous liquid 44.4 cP Smooth 200 0.25 Yes Tap Water Wavy 200 0.04 Yes Tap Water Smooth 100 0.04 Yes Tap Water Wavy 200 0.08 Yes

Conclusions:
-- Comparison of momentum transfer achieved using smooth surface rotor as against wavy surface rotor in Taylor-Couette laminar flow
When tap water was used as test fluid, for the smooth surface rotor, maximum residence time of 70.05 sec was achieved at the flow rate of 0.04 liter per minute and 100 rpm angular frequency of rotor where as when wavy surface rotor was used, the maximum residence time of 69.73 sec was achieved at the flow rate of 0.04 liter per minute and 200 rpm angular frequency of the rotor.
Also, when the fluid was passed through the reactor with wavy rotor having no angular frequency, the residence time achieved was 120 sec. But the reactor did not get washed off completely from the dye.
Taylor number achieved using Taylor-Couette flow reactor was 187.71 which was low than the critical value of 1708. Hence the flow the achieved was laminar Taylor Couette flow.
When viscous liquid was tested for the residence time of the dye, it was found that the residence time increased with increasing syrup viscosities. Wavy rotor gave maximum residence time of 123.83 sec compared to smooth surface rotor of 115.36 second.

Conclusions:
-- Experimentation on processing of non-Newtonian liquids with the variations in the rotor type arrangement
Complete inactivation of E.coli K12 was achieved in viscous liquid of 81.6 cP and 44.4 cP viscosities using smooth as well as wavy surface rotor at 0.25 liter per minute flow rate.
When tap water was used as a test fluid, complete inactivation of E.coli K12 was achieved using smooth and wavy surface rotors at 0.04 liter per minute and 0.08 liter per minute flow rate.

Bibliography
‘ Juice Irradiation with Taylor-Couette Flow:UV Inactivation of E. coli ’; L.J.Forney a* , J. A. Pierson b , and Z. Ye a ; a- School of Chemical and Bimolecular Engineering ,Georgia Institute of Technology, Atlanta,GA, 30332, b- Electro-Optics, Environment, and Materials Laboratory-Food Processing Technology , Division, Georgia Tech Research Institute, Atlanta, GA, 30332
‘ Biodosimetry of Escherichia coli Inactivation in Model Juices with regard to dose distribution in Annular UV reactors’; T. Koutchma and B. Parisi
‘ UV Disinfection Between Concentric Cylinders’; Zhengcai Ye, School of Chemical and Bimolecular Engineering Georgia Institute of Technology, May 2007
‘ Inactivation efficiency of UV treatment of juices’; T. Koutchma 1 , C. Adhikari 1 , and E. G. Murakami 2 . (1) National Center for Food Safety and Technology, Illinois Institute of Technology, 6502 S. Archer Road, Moffett Campus, Summit-Argo, IL 60501, (2) National Center for Food Safety and Technology, FDA, 6502 S. Archer Road, Summit-Argo, IL 60501

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