Continuous IQF Freezing with Fluidized and Fixed Bed Stages
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Solution Overview
Problem
Current individual quick freezing (IQF) technologies, such as fluidized bed tunnels, result in slow freezing due to limited transfer coefficients, leading to the formation of extracellular crystals that damage cell walls and reduce the organoleptic quality of frozen food products.
Innovation Solution
A continuous freezing process combining a fluidized bed section and a fixed bed section, where products are initially frozen on the periphery in a fluidized bed with a coolant air flow speed V1, followed by core freezing in a fixed bed with a coolant air flow speed V2 greater than V1, allowing for efficient and uniform freezing without the need for independent control of two air flows.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If fluidized bed freezing is used with air speeds of 2 to 3 m/s, then products can be kept in suspension and fluidized, but the convection coefficients are limited to 30 to 60 W.m-2 and freezing time becomes long (7 to 9 minutes for green beans)
Solution Approach 1:
The freezing process is divided into two distinct phases: fluidized bed freezing phase where products are suspended for initial freezing, and fixed bed freezing phase where products are pressed against the support for rapid core freezing. This segmentation allows each phase to optimize its function without compromise.
Solution Approach 2:
The system dynamically transitions between two operational states: fluidized state for initial freezing and fixed state for rapid core freezing. The air flow rate is dynamically adjusted to switch between these states, optimizing heat transfer coefficients at each stage.
2Ease of operation
If slow freezing is used in fluidized bed tunnels, then products can be kept in suspension, but extracellular crystals are formed which tear apart cell walls and reduce organoleptic quality
Solution Approach 1:
The freezing process is divided into two distinct phases: fluidized bed freezing phase where products are suspended for initial freezing, and fixed bed freezing phase where products are pressed against the support for rapid core freezing. This segmentation allows each phase to optimize its function without compromise.
Solution Approach 2:
The system dynamically transitions between two operational states: fluidized state for initial freezing and fixed state for rapid core freezing. The air flow rate is dynamically adjusted to switch between these states, optimizing heat transfer coefficients at each stage.
3Adaptability or versatility
If two independent air flows are used for fluidized bed and fixed bed freezing sections, then both freezing modes can be implemented, but device complexity and control requirements increase
Solution Approach 1:
A single air flow source serves both the fluidized bed section and the fixed bed section. By adjusting the air flow rate, the system can switch between operating modes without requiring independent control systems for each section, thereby reducing complexity.
Solution Approach 2:
The air flow system is designed to perform multiple functions: it can operate at lower speeds to fluidize products in the first section, and at higher speeds to press products against the support in the second section. This multi-functionality eliminates the need for separate control systems.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This process significantly reduces freezing time, enhances the quality of frozen products by minimizing cell damage, and maintains the organoleptic characteristics of fruits and vegetables, with convection coefficients reaching up to 300 W/m²°C, resulting in faster and more effective freezing compared to traditional methods.
Implementation Method 1
placing a layer of products in dynamic suspension under the lift of a coolant air flow of speed V1
Implementation Method 2
pressing the layer of products against the support under the force of a coolant air flow with a speed V2
Implementation Method 3
subjecting the products to an ascending flow of cold air... convection coefficients reach 30 to 60 W.m-2
Implementation Method 4
obtain freezing of the products at their periphery... obtain the products being completely frozen to the core
Data Source
Figure 1
Figure 2
Figure 3
AI summary
The installation (1) has a fixed bed type deep freezing section (3) including a plating unit to plate a layer of food products (P) against a support (31) under effort of refrigerant air flow (34) at speed to obtain total freezing at a core of the products, where the plating unit is formed of a ventilation unit (32) and a refrigeration unit (33). An upper conveyor (35) sends the products towards the section (3) and a fluidized bed type deep freezing section (2), where the refrigerant air flow of the speed is raised so as to plate the products against a lower surface of a belt of the conveyor.