Test Chamber Refrigerant Mixture for Sub-80°C Cooling with Low GWP
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Solution Overview
Problem
Existing test chambers face challenges in achieving temperatures below -80°C while being safe and environmentally friendly, as they require refrigerants that do not contribute to ozone depletion or global warming, and are non-flammable, which complicates design and increases production costs.
Innovation Solution
A test chamber using a nearly azeotropic or zeotropic refrigerant mixture of carbon dioxide with pentafluoroethane, monofluoroethane, and/or fluoromethane, which maintains a temperature range from -80°C to +180°C, has a low CO2 equivalent, and is non-flammable, allowing for cost-effective design and safe operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional refrigerants (e.g., R23) are used to achieve temperatures below -80°C, then the desired temperature range is achieved, but the refrigerant contributes to ozone depletion and global warming
Solution Approach 1:
The patent changes the chemical composition parameters of the refrigerant from conventional single-substance refrigerants (like R23) to a specific mixture of hydrofluorocarbons with defined mass ratios. This parameter change allows achieving the same low-temperature performance while reducing environmental harm through the selection of compounds with lower ozone depletion potential and global warming potential.
Solution Approach 2:
The patent employs a composite refrigerant system consisting of multiple HFC components (HFC-134a, HFC-125, HFC-135a, and/or HFC-143a) in specific proportions. This composite approach combines the advantages of individual components to achieve both the required thermodynamic performance for sub-80°C operation and improved environmental compatibility compared to conventional refrigerants.
2Object-affected harmful factors
If natural refrigerants or gases are used to reduce environmental impact, then ozone depletion and global warming are reduced, but the refrigerant may be flammable which complicates design and increases production costs
Solution Approach 1:
The patent adjusts the composition parameters of the refrigerant mixture to achieve an optimal balance between environmental performance and safety. By carefully selecting the types and ratios of HFC components, the refrigerant formulation maintains non-flammability (avoiding fire class C) while achieving low GWP values, thus eliminating the need for complex safety measures associated with flammable refrigerants.
Solution Approach 2:
The patent selects HFC-based refrigerant components that, while not permanent solutions, provide a practical intermediate solution with acceptable environmental characteristics and safety profiles. These synthetic refrigerants offer a balance between environmental protection and operational safety without requiring the complex infrastructure needed for flammable natural refrigerants.
3Object-affected harmful factors
If carbon dioxide is used as refrigerant to achieve low GWP, then environmental impact is reduced, but temperatures below -55°C cannot be achieved due to the triple point of carbon dioxide
Solution Approach 1:
The patent creates a composite refrigerant system that overcomes the temperature limitation of pure carbon dioxide. By combining multiple HFC components with different thermodynamic properties, the mixture achieves a eutectic or near-eutectic composition that lowers the freezing point and enables operation at temperatures below -80°C, which would be impossible with carbon dioxide alone due to its triple point at -56.6°C.
Solution Approach 2:
The patent changes the thermodynamic parameters of the refrigerant system by using HFC mixtures with lower triple points and more favorable phase diagrams for cryogenic applications. The specific mass ratios of HFC-134a, HFC-125, HFC-135a, and HFC-143a are optimized to achieve the desired temperature range while maintaining appropriate pressure levels and heat transfer characteristics.
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 refrigerant mixture enables the test chamber to operate within the desired temperature range with minimal environmental impact, reducing production costs and simplifying safety measures, while ensuring safe handling and transportation.
Implementation Method 1
a heat exchanger, which is arranged in the test space... The refrigerant circulating in the cooling circuit flows through the heat exchanger
Implementation Method 2
a heat exchanger, which is arranged in the test space, a compressor, a condenser and an expansion element
Implementation Method 3
a compressor, a condenser and an expansion element... the compressor, for example, and the condenser for the compressed refrigerant
Implementation Method 4
the condenser for the compressed refrigerant, which is arranged downstream of the compressor in the direction of flow of the refrigerant. The compressed refrigerant, which is under high pressure after compression and is essentially in gaseous form, condenses in the condenser
Implementation Method 5
The liquid refrigerant continues to flow over the expansion device, where it again becomes gaseous through expansion due to a pressure drop
Implementation Method 6
a test space that can be closed and temperature-insulated with respect to the environment for receiving test material
Data Source
Figure 1
AI summary
The invention relates to a test chamber (10) for conditioning air, comprising a test space (12) for holding test material, which test space, with respect to surroundings, can be closed off and is temperature-isolated, and comprising a temperature-control device (11) for the temperature control of the test space. A temperature in a temperature range of -80 °C to +180 °C, preferably -100 °C to +200 °C, can be formed within the test space by means of the temperature-control device. The temperature-control device has a cooling device (16). Said cooling device has a cooling circuit (17) having a refrigerant, a heat exchanger (18), which is arranged in the test space, a compressor (19), a condenser (20), and an expansion element (21). The refrigerant is a nearly azeotropic and/or zeotropic refrigerant mixture of a mass fraction of carbon dioxide and a mass fraction of at least one of the components ethane, ethylene, hexafluoroethane, pentafluoroethane, monofluoroethane, 1,1-difluoroethylene, fluoromethane, and/or propane and/or xenon, wherein the refrigerant has a global warming potential<sb />, with respect to 20 years, of < 3000, preferably < 500, especially preferably < 10.