Ejector Refrigeration Cycle With Two-Stage Compression
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Solution Overview
Problem
Existing ejector refrigeration systems face inefficiencies in power consumption and refrigeration effect due to high compressor pressure ratios and suboptimal evaporator performance, particularly in achieving a two-phase state for enhanced heat transfer.
Innovation Solution
The system employs two compressors and an additional ejector and separator configuration, with a secondary compressor operating at a lower pressure ratio and mass flow rate, and a secondary ejector to optimize vapor pressure and refrigerant distribution, allowing for improved compressor efficiency and cycle efficiency by reducing the pressure ratio and enhancing evaporator performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single compressor is used in the ejector refrigeration system, then the system structure is simple, but the compressor pressure ratio is high leading to high power consumption
Solution Approach 1:
The single compressor is divided into two separate compressors: a first compressor that compresses refrigerant to an intermediate pressure, and a second compressor that further compresses the refrigerant to the final high pressure. This segmentation reduces the pressure ratio of each individual compressor, improving overall system efficiency and reducing power consumption while maintaining the required high-pressure output.
2Device complexity
If a single compressor operates at high pressure ratio, then the system is simple, but the refrigeration effect per unit mass flow is reduced
Solution Approach 1:
The compression process is segmented into two stages with an intermediate pressure level. The first compressor raises the pressure to an intermediate level, and the second compressor completes the pressure increase to the high-pressure side. This two-stage compression with intermediate cooling improves the refrigeration effect per unit mass flow by reducing the work required for compression and improving the efficiency of the ejector operation.
3Ease of operation
If the evaporator operates without achieving two-phase state, then the system operation is simple, but the heat transfer performance is suboptimal
Solution Approach 1:
The system performs preliminary action by using the ejector to create a two-phase refrigerant mixture before it enters the evaporator. The ejector mixes high-pressure liquid refrigerant with low-pressure vapor to produce a controlled two-phase flow that enters the evaporator, ensuring optimal heat transfer conditions are established before the refrigerant begins its heat absorption process in the evaporator.
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 reduces power consumption and increases refrigeration effect per unit mass flow, improving evaporator performance and potentially reducing the size of the evaporator while maintaining desired evaporator pressures.
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 which provides a mixing zone
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
The resulting combined flow 120 is a liquid/vapor mixture and 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 from the discharge port 26
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
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.