Deck-Mounted Cascade Heat Exchanger for Freezer Space Efficiency
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Solution Overview
Problem
Conventional refrigeration systems for ultra-low temperature freezers occupy valuable space and have limited efficiency due to the large size of heat exchangers and insufficient insulation, which restricts the maximization of cooling/storage space.
Innovation Solution
A two-stage refrigeration system with a split-flow brazed plate heat exchanger located within an insulated enclosure in the deck of the freezer, allowing for adequate insulation and efficient heat transfer between refrigerants, maximizing interior space and improving efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a single-pass coiled heat exchanger is used, then heat exchange between refrigerants is achieved, but the heat exchanger occupies large space and reduces cooling/storage space
Solution Approach 1:
The patent transitions from a single-pass coiled heat exchanger to a multi-pass serpentine heat exchanger configuration. This dimensional change in the flow path allows for more efficient heat exchange within a compact footprint, maximizing the use of available space between the inner and outer cabinet walls while maintaining effective thermal transfer between the first and second refrigerants.
Solution Approach 2:
The heat exchanger is nested within the limited space between the inner freezer chamber walls and the outer freezer cabinet. The serpentine configuration allows the heat exchanger to be folded and positioned in a compact manner, fitting into the available gap space without requiring additional external volume, thus preserving maximum cooling/storage space while achieving adequate heat exchange surface area.
2Loss of energy
If insulation around the heat exchanger is increased, then heat exchange efficiency is improved, but the cooling/storage space is reduced
Solution Approach 1:
The patent optimizes the insulation thickness parameter to a specific range that balances thermal efficiency with space constraints. By carefully selecting the insulation thickness, the system achieves adequate thermal isolation for efficient heat exchange between refrigerants while minimizing the space occupied by insulation, thereby preserving maximum cooling/storage volume within the cabinet structure.
3Loss of energy
If the heat exchanger is positioned alongside or behind the walls, then heat exchange is achieved, but valuable cooling/storage space is lost
Solution Approach 1:
The patent positions the heat exchanger in the horizontal plane between the inner and outer cabinet walls rather than vertically alongside or behind walls. This dimensional repositioning utilizes the available gap space more effectively, converting vertical wall-space usage into horizontal inter-wall space usage, thereby preserving valuable cooling/storage volume while maintaining heat exchange functionality.
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
The system achieves higher efficiency and maximizes cooling/storage space by positioning the heat exchanger in the deck, allowing for better insulation and optimized heat transfer, thereby enhancing the overall performance of ultra-low temperature freezers.
Implementation Method 1
Heat is transferred from the second refrigerant to the first refrigerant through a heat exchanger that is in fluid communication with the two stages of the refrigeration system
Implementation Method 2
Heat is transferred from the second refrigerant to the first refrigerant through a heat exchanger
Implementation Method 3
The first stage transfers energy (i.e., heat) from the first refrigerant to the surrounding environment through a condenser
Implementation Method 4
an insulated enclosure supported within the deck and a split-flow heat exchanger that is in fluid communication with the first and second fluid circuits and which is located within the insulated enclosure
Data Source
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AI summary
A refrigeration system (20) is provided for use with an ultra-low temperature freezer (10) having a deck (14) and a refrigerated cabinet (16) supported above the deck (14). The system (20) has a first refrigeration stage (24) and a second refrigeration stage (26). The first stage (24) defines a first fluid circuit for circulating a first refrigerant (34). The first stage (24) has a first compressor (50), a condenser (54) and a first expansion device (58) that is in fluid communication with the first fluid circuit. The second stage (26) defines a second fluid circuit for circulating a second refrigerant (36). The second stage (26) has a second compressor (70), a second expansion device (74) and an evaporator (78) that is in fluid communication with the second fluid circuit. The system (20) includes an insulated enclosure (150) supported within the deck (14) and a split-flow heat exchanger (44) that is in fluid communication with the first and second fluid circuits and which is located within the insulated enclosure (150).