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TECHNO-ECONOMIC STUDY OF SIMPLIFIED COOLING TIME ESTIMATION METHODS APPLIED ON TWO-PHASE YOGURT MANUFACTURING TECHNOLOGY
- M. Okulić, M. Ožegović and I. Zlatanović
TECHNO-ECONOMIC STUDY OF SIMPLIFIED COOLING TIME ESTIMATION METHODS - - PowerPoint PPT Presentation
TECHNO-ECONOMIC STUDY OF SIMPLIFIED COOLING TIME ESTIMATION METHODS - - PowerPoint PPT Presentation
IIR Student Competition International Congress of Refrigeration ICR2015 ICR2015 Yokohama, Japan TECHNO-ECONOMIC STUDY OF SIMPLIFIED COOLING TIME ESTIMATION METHODS APPLIED ON TWO-PHASE YOGURT MANUFACTURING TECHNOLOGY M. Okuli, M.
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IMPORTANT PARAMETERS
Thermo-physical properties of food
(heat conductivity, density and heat capacity)
Packaging material (size and shape)
(plastic cup, carton box, cellophane, ...)
Cooling medium
(water, air,...)
Refrigerant propeties
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SIMPLIFIED COOLING TIME CALCULATION METHODS
1. Cooling time estimation method based on f and j factors 2. Cooling time estimation method based on „Equivalent Heat Transfer Dimensionality“ (EHTD)
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Cooling time estimation method based on f and j factors
f and j factors represent the slope and intercept, of the temperature history curve. Factor j is a measure of the lag between the onset of cooling and the exponential decrease in the temperature of the food. Factor f represents the time required to
- btain a 90% reduction in the non-
dimensional temperature difference (Y).
10 20 30 40 50 60 0.1 0.2 0.3 0.4 0.6 0.8 1.0 2.0 f j
a i a
T T Y T T , min. Y
ln 2.303 f Y j
- Cooling time
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Calculation of f and j factors for irregulary shaped products
– shape factor – f factor – j factor
2 2 2 1 4 2
1 1 8 3 25 . A A L G
2 1 2
303 . 2 M L f
2 1
0388 .
892 .
M
e j
H A1 A2 L
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Cooling time estimation method based on „Equivalent Heat Transfer Dimensionality“ (EHTD)
Cooling time estimation method based on EHTD is based on the comparison of the total heat transfer to the heat transfer through the shortest dimension.
2 2
3 ln c L j E Y
4 3 4 3
1.85 1.85 Bi E Bi E E
- Cooling time
- EHTD factor
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Typical diary supply chain scheme
Farm Transport Diary
(processing factory)
Transport Distribution depots Transport Consumer Cold chain Retail
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Two-phase yogurt manufacturing technology
Reception
- f the raw milk
Filtration Separation Cream Skim milk Standardization
to acheive the desired % of fat content
Pasteurization
30 min at T=85oC 10 min at T=95oC
Homogenization
mixing at 15 Mpa and cooling to T=43oC
Starter culture insertion
at T=43oC
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Small blast freezers Storage cold room
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Yogurt palette packaging Small blast freezer interior
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CALCULATION RESULTS Estimation method based on f and j factors
Input data: Cooling time: 56.58 minutes
- Dimension of yogurt cup (diameter 2∙L and height H)
Ø55 x 63 mm
- Shortest distance between cup center and cup surface
L=0.0275 m
- The minimum cross sectional area containing L
A1=0.02375 m2
- The cross sectional area that is orthogonal to A1
A2=0.003465 m2
- Biot number
Bi=1.368
- The geometry index
G=0.801
- The characteristic value
M1
2=1.48
- Factor f
f=13169
- Factor j
j=0.842
- The fractional unaccomplished temperature difference
Y=0.465
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CALCULATION RESULTS Estimation method based on EHTD
Input data: Cooling time: 53.11 minutes
- Yogurt cup radius
L=0.0275 m
- Biot number
Bi=1.368
- Value of ω
ω =1.776
- Form factor for Bi=0
E0=2.74
- Form factor for Bi→ ∞
E∞=2.04
- (second shortest dimension of food item)/(shortest
dimension of food item) β1=1.15
- (longest dimension of food item)/(shortest dimension of
food item) β2=1.15
- Factor j
j=0.842
- The fractional unaccomplished temperature difference
Y=0.465
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The yogurt cup radius variation impact on cooling time
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