Rapid Hardening Systems
By R.C.Greener
Which Would You Rather Buy?
A or B
Benefits of Quick Hardening
• Better Freshness and Quality• Smoother Ice Cream Texture• Less Carton Damage in Storage and Distribution
Process• Less Chance of Product Skinning• Better Ice Cream Consistency Regardless of
Package Size or Shape• Lower Labor and Handling Costs• Inventory reduction - Ship directly from Hardener
Costs to Harden Rapidly
• More energy
• Higher Capital Investment
• Increased product shrinkage if design improper
Percentage of H2O Frozen at Various Draw/Fill TemperaturesDraw Temp % H2O Frozen
+25oF 33.0
+24oF 41.0
+23oF 47.0
+22oF 52.0
+21oF 56.0
+20oF 59.0
-15oF 90.0
Two Types of Hardening
Open Loop Closed Loop
Ice Cream Manufacturer Purchases Refrigeration
Ice Cream ManufacturerRefrigerates withSelf Contained System
CommonHardening Methods
CryogenicAir
ConvectionComb. Plate/
Air ConvectionPlateImmersion
Open Loop Closed Loop
Advantages of Cryogenic Hardening
• Lowest retention time for ice cream novelties & cakes
• Excellent ice cream texture
• Allows surface setting of novelty item prior to wrapping
• Superior overall quality for cake items
Disadvantages of Cryogenic Hardening
• Very expensive on a cost/lb basis
• Cost is proportional to location cryogenic medium processing
• Unit must meet sanitation demands
• Process requires expensive production room area
How Immersion & Plate Systems Harden
Ice CreamEvaporativeCondenser
MechanicalRefrigeration
System
Heat Transferred by Direct Conduction from Product to Refrigerant
Energy Transferred from Refrigerant to Atmosphere
Advantages of Immersion Hardening
• Best method to harden stick novelties
• Rapid hardening with resultant minimum retention times
• Automation allows high production rates
• High product quality
• Efficient heat removal process
Disadvantages of Immersion Hardening
• Single item process• Requires expensive production room area• Must meet sanitation requirements• Some units subject to high waste water
demands• Product shrinkage through process is relatively
high• High capital expense for single item manufacture
Advantages of Plate Hardener
• Makes near perfect squares and rectangles on 95% of production
• Rapid hardening with resultant minimum retention times
• Heat removal via conduction is very efficient• Requires minimal space in low cost ambient
warehouse environment• Low production shrinkage through hardening
process
Disadvantages of Plate Hardener
• Very limited item utility• Approximately 5% of product has shape
irregularities• High capital cost in plants where all volume can
not be hardened by plate process• Safety issue because refrigerant is in moving
hollow plate• Requires low refrigerant temperature
How Air Convection Hardens
Ice CreamMechanical
RefrigerationSystem
CoilEvaporativeCondenser
ColdAir
WarmAir
Conduction from Product to Air
Conduction FromProduct to Refrigerant
Conduction from Refrigerant to Atmosphere
Air Convection Significance
• Used for Hardening over 85% of Ice Cream in US.
• Used by over 95% of Ice Cream Manufacturers in US
Important Facts about Convection Hardening
• Product Draw or Fill Temperature
• Package Orientation during Hardening Process.
• Laminar Air Flow Vs. Turbulent air flow
• Air Vs. Heat Removal Index Temperature
• Product Spacing
Importance of Draw/Fill Temperatures
Draw Temp % H2O Frozen
+25oF 33.0
+24oF 41.0
+23oF 47.0
+22oF 52.0
+21oF 56.0
+20oF 59.0
-15oF 90.0
Air Flow Perpendicular to Pak Length
• Package: 4 – 56 oz.• Flavor: Choc. Peanut
butter cup.• Air Temp.: -25o F• Air Velocity: 1000 FPM• Core Temp In: +20.3o F• Core Temp Out: -0.4o F
• Retention Time =
5 Hr 48 Min
Air Flow Parallel to Pak Length
• Package: 4 – 56 oz.• Flavor: Choc. Peanut
butter cup.• Air Temp.: -25o F• Air Velocity: 1000 FPM• Core Temp In: +19.8o F• Core Temp Out: -1.3o F
• Retention Time =
4 Hr 18 Min
Draw Temp vs. Hardening Times
• Package: 4 – 56 oz. SqRd
• Flavor: Pumpkin Crème• Air Temp.: -23o F• Air Velocity: 1000 FPM• Core Temp In: +23.2o F• Core Temp Out: -0.1o F
• Retention Time =
5 Hr 28 Min
• Package: 4 – 56 oz. SqRd
• Flavor: Pumpkin Crème• Air Temp.: -23o F• Air Velocity: 1000 FPM• Core Temp In: +19.3o F• Core Temp Out: -0.2o F
• Retention Time =
4 Hr 4 Min
Laminar vs Turbulent Air Flow
Definitions:
Laminar Flow = Streamline flow in a viscous fluid near a solid boundary.
Turbulent Flow = Fluid flow in which the velocity at a given point varies erratically in magnitude and direction.
The requirement for an efficient air distribution system is
Conversion from Turbulent Flow
to
Laminar FlowLaminar Flow
What Causes Turbulent Flow?
1. Fans and other mechanical methods of moving air.
2. Obstructions to normal air flow.
3. Merging air patterns.
Advantages:
• Can provide excellent heat removal when hardening.
Disadvantages:
• Consumes greater amount energy (Fan BHP).• Increases static pressure resulting in reduced air flow (CFM) with
existing equipment.
Package Spacing
Package Rows should have a minimum of 2.00 inch space between rows for air flow.
Advantages of Pallet Hardener
• More mechanical simplicity than all other air convection hardeners
• Low capital investment• Hardens multiple package sizes• Low maintenance costs
Disadvantages of Pallet Hardener
• Mediocre to poor hardening results• Requires conscientious operator to insure
product quality• High labor costs• High product shrinkage• Can result in unattractive packaging
Advantages of Spiral Belt Hardener
• Highest degree of mechanical simplicity of automated air convection hardeners
• Good hardening when operated within design parameters
• Low to moderate capital investment• Hardens multiple package sizes simultaneously• Low production shrinkage through hardening process• Available in system sizes from 250 GPH
Disadvantages of Spiral Belt Hardener
• Belt loading limited to 10 lbs/ft of belt for good belt life
• High fan horsepower results in high energy demands and cost
• Requires low refrigerant temperatures• Very difficult to automate package handling in
high output plants• High maintenance costs (belt cost represents
35% of typical system cost)
Advantages of Tray between Continuous Chain
• Highest degree of mechanical simplicity of automated tray type air convection hardeners
• Double pass air system insures very good hardening• Moderate capital investment• Hardens multiple package sizes simultaneously• Low production shrinkage through hardening process• Very good package orientation adapts to automation• Efficient air system reduces energy requirement and cost• Available in systems as small as 250 GPH
Disadvantages of Tray between Continuous Chain
• Feed rates less than 2500 GPH • Not very suitable for simultaneous multiple line
productions• Higher maintenance costs than tray/transport
type systems
Advantages of Variable Retention Time (VRT)
Hardener
• Allows variable retention time for different size items
• Easily adapts to line automation• Maintains package orientation through the
hardening process• Hardens multiple package sizes simultaneously• Handles high production rates (up to 10,000
GPH)
Disadvantages of Variable Retention Time (VRT) Hardener
• Highest cost hardener• Complex program and operation• Higher product shrinkage through system• High static pressures require higher HP and
energy requirements & longer retention times• Inherent design results in higher maintenance
costs• Minimum size system is approx 1500 GPH
Multiple Tray Transport
Heart of the Multiple Tray Transport
2
3
4
5
1
The Transport
Advantages of Multiple Tray Transport
• Double pass air system insures very good hardening• Hardens multiple package sizes simultaneously• Very low production shrinkage through hardening
process w/ good design • Moderate mechanical simplicity of automated tray type
air convection hardeners• Moderate capital investment• Very low maintenance cost with long service life (40 +
years)• Very good package orientation adapts to automation• Efficient air system reduces energy requirement and cost• Available in sizes to 10,000 GPH
Disadvantages of Multiple Tray Transport
• No multiple retention time in standard form• Minimum size system is 750 GPH• More complex than spiral belt system• Higher product shrinkage w/ poor design
Advantages of Fusion Cell
• Combination conduction/convection system hardens faster than any air convection system
• Most efficient air hardening system -- rivals that of plate hardener
• Hardens multiple package sizes simultaneously• Very low production shrinkage through hardening process • Moderate mechanical simplicity of automated tray type air
convection hardeners• Overall capital investment lower than most air systems• Very low maintenance cost with long service life (30 + years)• Very good package orientation adapts to automation• Available in sizes to 10,000 GPH• Most compact of air convection hardeners• Allows same refrigerant suction temp for both freezer and
hardener
Disadvantages of Fusion Cell
• No multiple retention time in standard form• Minimum size system is 750 GPH• More complex than spiral belt system• Higher floor loadings than other air convection
types
Manual Hardener DesignFan Coil
Air Plenum
Carts or Wire Baskets w/ Rows of Ice Cream Paks
= Laminar Flow
Energy Consumption in Average Ice Cream Plant
• Mix Processing = 5 %
• Freezing = 35%
• Hardening = 45%
• Storage = 15%
Total = 100%
Real Energy Costs
• 1.0 HP motor w/ 16 Hr on/8 Hr off Cycle• 8 Hr off = .746 x .08 x 8 Hr x 250 da
= $ 119.36• 115 off day = .746 x .08 x 24 Hr x 115 da
= $ 164.72• Total Annual Energy Waste = $ 284.08
• Total Waste for 25 Motors = $ 7,102.00• Does not include: refrigeration losses
Individual Carton vs
Over Wrapped Package
TRI-Tray Hardening Test w/ Individual Sqround
Retention Time: 2 Hr. 13 Min.
TRI-Tray Hardening Test w/ (6) Overwrapped Sqrds
Retention Time: 4 Hr. 33 Min.
Design Objectives of Fast Hardener
• Rapid hardening to achieve uniform ice crystallization and improve quality.
• Improve package quality.• Ability to adapt to future packaging/marketing changes.• Lowest possible product shrinkage thru hardening
process.• Low energy demand.• Low power (kwh) requirement.• Low direct labor.• Low maintenance cost.• Adaptability to Automation.• Capital cost commensurate with operational savings.