Refrigeration Cycle Oxygen Adsorption for HFO Stability
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Solution Overview
Problem
Refrigeration cycle devices using low global warming potential (GWP) hydrofluoro olefin (HFO) refrigerants face issues with chemical stability and oxidation degradation due to adsorption by zeolites, which also adsorb refrigerant molecules, leading to potential resolution and degradation.
Innovation Solution
Incorporating an oxygen adsorption device with synthetic zeolite having a pore diameter larger than oxygen and smaller than HFO refrigerant molecules to selectively adsorb oxygen, preventing refrigerant oxidation and resolution, while using a separate water adsorption device to manage water content and minimize refrigerant adsorption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If zeolite with pore diameter larger than oxygen molecular diameter is used for physical adsorption, then oxygen adsorption speed is improved, but refrigerant molecules are also adsorbed leading to resolution and degradation
Solution Approach 1:
The patent applies local quality by creating a gradient in pore diameter distribution within the zeolite structure. The zeolite contains pores with different diameters, where smaller pores selectively adsorb oxygen molecules while larger pores allow refrigerant molecules to pass through without adsorption. This spatial differentiation of pore sizes enables selective adsorption based on molecular dimensions, resolving the contradiction between fast oxygen adsorption and refrigerant stability.
2Object-affected harmful factors
If zeolite is used as adsorbent for oxygen removal, then oxidation degradation is prevented, but refrigerant molecules are adsorbed and potentially resolved by catalysis
Solution Approach 1:
The patent utilizes porous materials with specifically controlled pore diameter distribution. The zeolite's porous structure is engineered to have a bimodal or broad pore size distribution, creating distinct pathways: smaller pores that selectively trap oxygen molecules through physical adsorption, and larger pores that permit refrigerant molecules to pass through without interaction. This porous material design enables selective adsorption based on molecular size differences, preventing both oxidation and refrigerant degradation.
3Reliability
If chemical adsorption is used to remove oxygen and carbon dioxide, then resolution of refrigerant is prevented, but adsorption speed is slower compared to physical adsorption
Solution Approach 1:
The patent applies segmentation by dividing the adsorption function into two distinct mechanisms operating within the same zeolite structure: physical adsorption in smaller pores for rapid oxygen removal, and chemical adsorption in larger pores or on specific active sites for thorough removal of oxygen and carbon dioxide. This segmentation of adsorption mechanisms allows the system to achieve both fast initial adsorption speed and complete refrigerant protection without resolution.
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 configuration effectively prevents refrigerant oxidation and resolution, enhancing the reliability and stability of the refrigeration cycle device by ensuring selective adsorption of oxygen without adsorbing the HFO refrigerant, thus maintaining the refrigerant's integrity and extending the device's operational lifespan.
Implementation Method 1
Adsorbent for the physical adsorption tends to reversibly adsorb an adsorption target faster than adsorbent for chemical adsorption
Implementation Method 2
The pore diameter of a pore included in the synthetic zeolite is larger than the molecular diameter of oxygen and smaller than the molecular diameter of the hydrofluoro olefin
Data Source
AI summary
An air conditioner which includes a compressor, an outdoor heat exchanger, an outdoor expansion valve, and an indoor heat exchanger that have been successively connected by a pipeline, and in which a hydrofluoroolefin-containing refrigerant is to be used, the air conditioner being characterized in that an oxygen adsorption device in which a synthetic zeolite is used as an adsorbent has been disposed somewhere in the pipeline, the synthetic zeolite having a pore diameter which is larger than the size of the oxygen molecule but smaller than the size of the hydrofluoroolefin molecule.