Single-Circuit Mixed Refrigerant Freezing for -85°C Chambers
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Solution Overview
Problem
Conventional refrigerants used in freezing devices are harmful to the ozone layer and pose safety risks due to their combustibility, making it difficult to achieve extremely low temperatures without complex multistage systems and increased maintenance costs.
Innovation Solution
A non-azeotropic mixed refrigerant composition of R245fa, R600, R23, R116, R508A, or R508B is used, with specific weight ratios to create an incombustible refrigerant that can achieve temperatures below -80°C in a single-stage system, maintaining performance and safety while reducing production costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single-component refrigerant is used, then the structure is simple, but it is difficult to satisfy requirements for low boiling point, high critical temperature, and ozone layer protection simultaneously
Solution Approach 1:
The patent uses a composite refrigerant system consisting of two separate circuits: a first refrigerant circuit containing R134a for standard cooling operations, and a second refrigerant circuit containing R23 for achieving extremely low temperatures below -80°C. This composite approach allows each refrigerant to be optimized for its specific function while working together in a unified system.
2Temperature
If a multistage freezing system is used, then extremely low temperature below -80°C can be achieved, but the structure becomes complicated and enlarged with increased maintenance difficulty and running cost
Solution Approach 1:
The patent segments the refrigeration system into two independent but coordinated circuits: a first circuit for general cooling and a second circuit specifically for extreme low-temperature generation. The second circuit uses R23 refrigerant that evaporates at extremely low temperatures, allowing the system to achieve below -80°C without requiring multiple compression stages, thereby simplifying the overall structure while maintaining the capability for extreme cooling.
3Temperature
If conventional non-azeotropic mixed refrigerant containing ethane or ethylene is used, then extremely low temperature of -60°C or less can be achieved, but the refrigerant is combustible and has unsatisfactory safety and treating property
Solution Approach 1:
The patent replaces combustible refrigerants (ethane, ethylene) with R23 (trifluoromethane), which is non-combustible and chemically inert. R23 has a boiling point of -82°C, allowing it to achieve extremely low temperatures without the safety risks associated with combustible gases. This substitution maintains the temperature performance while dramatically improving safety and reliability.
4Ease of operation
If R134a is used in the first refrigerant circuit, then standard cooling is achieved, but it cannot achieve extremely low temperature below -80°C
Solution Approach 1:
The patent creates a multi-functional refrigeration system where the first circuit with R134a handles standard cooling operations, and the second circuit with R23 handles extreme low-temperature generation. Both circuits are integrated through a shared compressor and heat exchanger system, allowing the same hardware to perform multiple temperature ranges and functions, thereby achieving both ease of operation and extreme temperature capability.
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 solution allows for safe, reliable, and cost-effective achievement of extremely low temperatures, stabilizing food and biological specimens, and addresses environmental concerns by being incombustible and using a simpler system, enhancing refrigerant handling properties and reducing the risk of leaks.
Implementation Method 1
a multistage system is employed in which the refrigerant components are condensed in multiple stages
Implementation Method 2
a refrigerant discharged from a compressor is condensed and then evaporated to exert a cooling function
Implementation Method 3
a non-azeotropic mixed refrigerant constituted of two or more of components is used... the extremely low temperature is realized by ethane or ethylene having a remarkably low boiling point
Data Source
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AI summary
An object is to provide a freezing device in which a safely-treatable incombustible mixed refrigerant can be used and which can realize an extremely low temperature of -85°C or less in chamber by a simple structure. The freezing device comprises a single refrigerant circuit in which the refrigerant discharged from a compressor is condensed and thereafter evaporated to exert a cooling function and which allows heat exchange between the evaporated refrigerant and the condensed refrigerant, wherein there is introduced into the refrigerant circuit a non-azeotropic mixed refrigerant containing R245fa, R600, R23 and R14; a non-azeotropic mixed refrigerant containing R245fa, R600, R116 and R14; a non-azeotropic mixed refrigerant containing R245fa, R600, R508A and R14; or a non-azeotropic mixed refrigerant containing R245fa, R600, R508B and R14.