Composite Refrigerant Circuit to Prevent CO2 Dry Ice Clogging
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Solution Overview
Problem
The high boiling point of carbon dioxide (R744) leads to its solidification into dry ice in refrigerant circuits, causing clogs and disrupting refrigerant circulation, which results in temperature rises in refrigeration apparatuses designed for ultralow temperatures.
Innovation Solution
A refrigerant composite material is used, comprising a first refrigerant with a boiling point between -89.0°C and -78.1°C, such as difluoroethylene (R1132a) or ethane (R170), mixed with carbon dioxide (R744) and a second refrigerant like difluoromethane (R32) that is soluble in carbon dioxide at lower temperatures, to prevent dry ice formation and enhance refrigeration performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If carbon dioxide (R744) is used as a refrigerant, then global-warming potential is reduced and thermal conductivity is improved, but carbon dioxide solidifies into dry ice at ultralow temperatures causing pipe clogs and disrupting refrigerant circulation
Solution Approach 1:
The patent uses a composite refrigerant system consisting of carbon dioxide (R744) mixed with a first refrigerant (ultralow temperature range refrigerant with boiling point -89.0°C to -78.1°C) and a second refrigerant (soluble in carbon dioxide at temperatures below its boiling point). This composite formulation allows the system to maintain the low GWP and high thermal conductivity of CO2 while preventing dry ice formation through the presence of components that remain liquid at ultralow temperatures.
Solution Approach 2:
The patent changes the physical-chemical parameters of the refrigerant system by selecting specific components with defined boiling points and solubility characteristics. The first refrigerant has a boiling point between -89.0°C and -78.1°C, and the second refrigerant is selected based on its solubility in carbon dioxide at temperatures below -78.4°C, thereby controlling the phase behavior to prevent solidification while maintaining refrigeration effectiveness.
2Productivity
If carbon dioxide (R744) proportion in the refrigerant composite material is increased, then refrigeration performance is improved, but the risk of dry ice formation and pipe clogs increases
Solution Approach 1:
The patent optimizes the compositional parameters of the refrigerant composite material by specifying that carbon dioxide constitutes 30-80 mass% of the total refrigerant. This parameter range is carefully selected to maximize refrigeration performance through CO2's high thermal conductivity while maintaining sufficient proportions of the first and second refrigerants to prevent dry ice formation. The solubility relationship between the second refrigerant and carbon dioxide at ultralow temperatures is exploited to keep the mixture in liquid phase.
3Temperature
If a single refrigerant with low boiling point is used, then ultralow temperature cooling is achieved, but global-warming potential is high and inflammability is a concern
Solution Approach 1:
The patent replaces single-component refrigerants with high GWP or inflammability concerns (such as ethane R170 with GWP=3 or other hydrocarbon refrigerants) with a composite refrigerant formulation. The mixture includes carbon dioxide (GWP=1, non-flammable) as the base, combined with first and second refrigerants that provide the necessary ultralow temperature performance. This composite approach achieves the required cooling temperatures while significantly reducing global-warming potential and eliminating inflammability risks associated with pure hydrocarbon refrigerants.
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 effectively prevents dry ice formation, ensuring stable refrigeration performance even with high carbon dioxide proportions, improving refrigeration efficiency and reducing global-warming potential while increasing thermal conductivity and compressor suction density.
Implementation Method 1
an evaporator, and a refrigerant composite material containing a first refrigerant of an ultralow temperature range refrigerant having a boiling point of not less than -89.0°C and not more than -78.1°C, carbon dioxide (R744), and a second refrigerant that is soluble in carbon dioxide (R744) at a temperature lower than a boiling point of carbon dioxide (R744)
Implementation Method 2
a second refrigerant that is soluble in carbon dioxide (R744) at a temperature lower than a boiling point of carbon dioxide (R744)
Data Source
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AI summary
Provided is a refrigerating device capable of effectively eliminating problems due to the formation of dry ice from carbon dioxide (R744). A refrigerant composition comprising a first refrigerant that is a very low temperature range refrigerant with a boiling point of no less than -89.0°C and no more than -78.1°C, carbon dioxide (R744), and a second refrigerant that is soluble with carbon dioxide (R744) at temperatures lower than the boiling point of carbon dioxide (R744) is used as a refrigerant in a low temperature side refrigeration circuit (6) of a refrigerating device (R). The first refrigerant is ethane (R170), for example, and the second refrigerant is difluoromethane (R32), for example.