Cascade Refrigeration Pressure Control for HFO-1123 Stability
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Solution Overview
Problem
Refrigeration cycle apparatuses using CO2 refrigerant have lower coefficient of performance (COP) and higher global warming potential (GWP) compared to HFC-based refrigerants, and there is a lack of established techniques for operating refrigeration cycles with HFO-1123 refrigerant, which undergoes disproportionation, limiting safety, cost reduction, and energy efficiency improvements.
Innovation Solution
A multi-stage cascade refrigeration cycle apparatus that maintains the low-stage refrigerant, such as HFO-1123, at a pressure lower than its disproportionation pressure, using a refrigerant mixture like HFO-1123 and HFO-1234yf, and controlling the high-stage refrigerant to optimize COP and GWP, thereby reducing the likelihood of disproportionation and enhancing safety, cost-effectiveness, and energy efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If CO2 refrigerant is used as low-stage refrigerant, then the refrigeration cycle can operate, but the COP is lower and GWP is higher compared to HFC-based refrigerants
Solution Approach 1:
The patent changes the refrigerant type from CO2 to HFO-1123, altering the chemical composition parameter to achieve both lower GWP and comparable COP. This parameter change allows the system to meet environmental requirements while maintaining energy efficiency.
2Reliability
If HFO-1123 refrigerant is used as low-stage refrigerant, then safety is improved and pressure resistance requirements are reduced, but the refrigerant undergoes disproportionation
Solution Approach 1:
The patent changes the pressure parameter to maintain it below the disproportionation pressure threshold of HFO-1123. By controlling the operating pressure within a specific range, the system achieves both safety improvements and compositional stability, preventing the harmful disproportionation reaction.
3Ease of manufacture
If HFO-1123 refrigerant is used as low-stage refrigerant, then cost is reduced, but there is no established technique for operating the refrigeration cycle
Solution Approach 1:
The patent establishes specific operating parameters including pressure control below disproportionation pressure, temperature ranges, and pressure ratio limitations. These parameter specifications provide a clear operational framework that simplifies the implementation and operation of HFO-1123-based refrigeration cycles.
4Productivity
If low-stage refrigerant pressure is increased to improve cooling capacity, then the cooling performance improves, but the refrigerant undergoes disproportionation
Solution Approach 1:
The patent identifies and controls the pressure parameter to remain below the disproportionation pressure of HFO-1123. This parameter constraint ensures that cooling capacity can be optimized within safe operating limits without triggering the disproportionation reaction, balancing performance and stability.
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 apparatus operates safely and efficiently with improved COP and reduced GWP, similar to HFC-based systems, while maintaining the low-stage refrigerant below its disproportionation pressure, thus enhancing safety, reducing costs, and minimizing environmental impact.
Implementation Method 1
a cascade condenser exchanging heat between the low-stage refrigerant in the low-stage condenser and the high-stage refrigerant in the high-stage evaporator
Data Source
AI summary
A refrigeration cycle apparatus includes: a low-stage refrigeration cycle including a low-stage compressor, a low-stage condenser, a low-stage pressure reducing device, and a low-stage evaporator, and circulating low-stage refrigerant; a high-stage refrigeration cycle including a high-stage compressor, a high-stage condenser, a high-stage pressure reducing device, and a high-stage evaporator, and circulating high-stage refrigerant; a cascade condenser exchanging heat between the low-stage refrigerant in the low-stage condenser and the high-stage refrigerant in the high-stage evaporator, and a controller. The low-stage refrigerant is a refrigerant that undergoes disproportionation. The low-stage refrigerant is maintained at a pressure lower than a disproportionation pressure at which the low-stage refrigerant undergoes disproportionation.