Deck-Mounted Split-Flow Heat Exchanger for Ultra-Low Freezers
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Solution Overview
Problem
Conventional refrigeration systems for ultra-low temperature freezers are inefficient due to the large space requirements of heat exchangers and limited insulation, which compromises the available cooling and storage space.
Innovation Solution
A refrigeration system with a split-flow heat exchanger located within an insulated enclosure in the deck of the freezer, utilizing a brazed plate heat exchanger design that allows for vertical flow paths and adequate insulation, maximizing space efficiency and heat transfer.
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 heat exchanger is repositioned from a horizontal configuration alongside or behind freezer walls to a vertical configuration within the deck structure. This dimensional change allows the heat exchanger to utilize the vertical space in the deck, reducing its horizontal footprint and thereby maximizing the cooling/storage space while maintaining heat exchange functionality.
Solution Approach 2:
The heat exchanger is nested within the deck structure of the freezer, integrating it into the existing framework rather than placing it as a separate external component. This nesting approach allows the heat exchanger to occupy space that would otherwise be structural or unused, minimizing the impact on cooling/storage volume.
2Loss of energy
If insulation is placed around the heat exchanger, then heat transfer efficiency is improved, but the cooling/storage space is reduced
Solution Approach 1:
The insulated enclosure containing the heat exchanger is nested within the deck structure of the freezer. This integration allows the insulation to be positioned in space that would otherwise be structural or unused, providing thermal insulation benefits while minimizing the encroachment on cooling/storage volume.
Solution Approach 2:
By positioning the heat exchanger vertically within the deck and providing insulation around it in this configuration, the system achieves efficient heat transfer while utilizing vertical space rather than horizontal storage space. The insulation is arranged around the vertically-oriented heat exchanger, maximizing thermal efficiency without significantly reducing the horizontal cooling/storage area.
3Loss of energy
If the heat exchanger is placed alongside or behind freezer walls, then heat exchange is achieved, but valuable cooling/storage space is lost
Solution Approach 1:
The heat exchanger is extracted from its conventional position alongside or behind freezer walls and repositioned to the deck area. This extraction from the traditional location allows the heat exchanger to utilize the deck space, which is otherwise not available for cooling/storage, thereby preserving maximum storage volume while maintaining heat exchange functionality.
Solution Approach 2:
The heat exchanger is moved from a horizontal placement along walls to a vertical placement within the deck structure. This dimensional repositioning utilizes the vertical dimension of the deck space, effectively removing the heat exchanger from competition with horizontal cooling/storage space while maintaining its heat exchange function.
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 configuration enhances the efficiency of the refrigeration system by allowing for increased insulation around the heat exchanger and maximizing the interior space of the freezer, resulting in improved cooling performance and space utilization.
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
The heat exchanger is of a counter-flow type. The first refrigerant may enter the heat exchanger proximate a lower portion thereof and exit the heat exchanger proximate an upper portion thereof, such that the first refrigerant flows generally in an upward direction within the heat exchanger. Additionally, or alternatively, the second refrigerant may enter the heat exchanger proximate an upper portion thereof and exit the heat exchanger proximate a lower portion thereof, such that the second refrigerant flows generally in a downward direction within the heat exchanger.
Implementation Method 3
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
Implementation Method 4
the heat exchanger may have a plurality of stacked plates that define flow paths for the first and second refrigerants through the heat exchanger. In a specific embodiment, the heat exchanger is in the form of a brazed plate heat exchanger.
Data Source
AI summary
A refrigeration system is provided for use with an ultra-low temperature freezer having a deck and a refrigerated cabinet supported above the deck. The system has a first refrigeration stage and a second refrigeration stage. The first stage defines a first fluid circuit for circulating a first refrigerant. The first stage has a first compressor, a condenser and a first expansion device that is in fluid communication with the first fluid circuit. The second stage defines a second fluid circuit for circulating a second refrigerant. The second stage has a second compressor, a second expansion device and an evaporator that is in fluid communication with the second fluid circuit. The system includes 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.