Ejector Refrigeration Cycle With Dual Compressors for Pressure Ratio Control
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Solution Overview
Problem
Ejector refrigeration systems face limitations in optimizing compressor efficiency and refrigeration effect per unit mass flow, particularly in achieving reduced power consumption and improved evaporator performance, due to fixed pressure ratios and lack of control over the ejector's operation.
Innovation Solution
The system incorporates a first and second compressor, a heat rejection heat exchanger, an ejector, a separator, and a second separator with a second ejector, allowing for optimized pressure ratios and control through temperature and pressure sensors, enabling improved compressor efficiency and cycle efficiency by adjusting the vapor pressure entering the ejector secondary inlet.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single ejector is used in the refrigeration system, then the system structure is simple, but the compressor efficiency and refrigeration effect per unit mass flow cannot be optimized
Solution Approach 1:
The single ejector is divided into two separate ejectors: a first ejector connected to the compressor outlet and a second ejector connected to the evaporator outlet. This segmentation allows each ejector to perform specialized functions - the first ejector optimizes compression while the second ejector enhances refrigeration effect, thereby resolving the contradiction between structural simplicity and refrigeration performance.
2Stability of the object's composition
If the ejector operates at fixed pressure ratio, then the system operation is stable, but the compressor efficiency and power consumption cannot be optimized
Solution Approach 1:
The system introduces variable geometry nozzles in both ejectors that can dynamically adjust the pressure ratio according to operating conditions. This dynamic adjustment capability allows the system to optimize compressor efficiency and power consumption while maintaining stable operation through controlled adaptability, resolving the contradiction between operational stability and energy optimization.
3Device complexity
If the evaporator directly feeds the compressor, then the system structure is simple, but the evaporator cannot operate in two-phase state and superheating is required
Solution Approach 1:
Two ejectors are introduced as intermediary devices between the evaporator and compressor. The first ejector receives refrigerant from the compressor outlet and the second ejector receives refrigerant from the evaporator outlet, allowing the evaporator to operate in two-phase state without direct feeding to the compressor. This intermediary arrangement eliminates the need for superheating while maintaining simple system structure, resolving the contradiction between structural simplicity and heat transfer performance.
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
This configuration enhances compressor efficiency and total cycle efficiency by optimizing pressure ratios, reducing power consumption, and improving refrigeration effect per unit mass flow, while allowing for flexible operation in various refrigeration applications.
Implementation Method 1
The pressure reduction caused to the primary flow by the motive nozzle helps draw the secondary flow 112 into the outer member
Implementation Method 2
As the flow 103 exits the outlet 110, it begins to mix with the flow 112 with further mixing occurring through the mixing section 116
Implementation Method 3
The resulting combined flow 120 is a liquid/vapor mixture and decelerates and recovers pressure in the diffuser 118
Implementation Method 4
decelerates and recovers pressure in the diffuser 118
Implementation Method 5
Upon entering the separator, the flow 120 is separated back into the flows 103 and 112
Implementation Method 6
gaseous refrigerant is drawn by the compressor 22 through the suction line 56 and inlet 24 and compressed and discharged
Implementation Method 7
In the heat rejection heat exchanger, the refrigerant loses/rejects heat to a heat transfer fluid (e.g., fan-forced air or water or other fluid)
Implementation Method 8
Within the evaporator 64, the refrigerant absorbs heat from a heat transfer fluid (e.g., from a fan-forced air flow or water or other liquid)
Implementation Method 9
The flow 112 passes as a liquid to the expansion valve 70. The flow 112 may be expanded by the valve 70 (e.g., to a low quality (two-phase with small amount of vapor))
Data Source
Figure 1~2
Figure 3
Figure 4
AI summary
A system has first and second compressors (22, 180), a heat rejection heat exchanger (30), an ejector (38), a heat absorption heat exchanger (64), and a separator (48). The heat rejection heat exchanger (30) is coupled to the compressor to receive refrigerant compressed by the compressor. The ejector (38) has a primary inlet (40) coupled to the heat rejection exchanger (30) to receive refrigerant, a secondary inlet (42), and an outlet (44). The separator (48) has an inlet coupled to the outlet of the ejector to receive refrigerant from the ejector. The separator has a gas outlet (54) coupled to the compressor (22) to return refrigerant to the first compressor. The separator has a liquid outlet (52) coupled to the secondary inlet of the ejector to deliver refrigerant to the ejector (38). The heat absorption heat exchanger (64) is coupled to the liquid outlet of the separator to receive refrigerant. The second compressor (180) is between the separator and the ejector secondary inlet.