Two-Stage Refrigeration Cycle With Flash Gas Pressure Stabilization
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Solution Overview
Problem
Conventional refrigeration systems require multiple compressors and valves to manage both medium and low temperature refrigeration, leading to inefficiencies, increased vibration, and instability due to the need for complex pressure control and inadequate oil management.
Innovation Solution
A refrigeration system employing a two-stage compression process with an intermediate pressure expansion device and an oil management system that balances oil levels between compressor units, reducing the number of compressors and eliminating the need for an economizer stage, thereby simplifying pressure control and enhancing system stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple compressors and valves are used to manage both medium and low temperature refrigeration, then temperature control capability is improved, but device complexity increases and system stability deteriorates
Solution Approach 1:
The single compressor unit is designed to handle both medium temperature and low temperature refrigeration cycles through a two-stage compression process. The compressor performs multiple functions by compressing refrigerant to intermediate pressure for medium temperature circulation and to high pressure for low temperature circulation, eliminating the need for separate compressors for each temperature zone.
Solution Approach 2:
The compression process is divided into two stages with an intermediate pressure expansion device. The first stage compresses refrigerant to intermediate pressure, then the intermediate pressure expansion device expands it before the second stage compression to high pressure. This segmentation allows a single compressor to effectively manage both temperature zones.
2Adaptability or versatility
If multiple compressors and valves are used to manage both medium and low temperature refrigeration, then temperature control capability is improved, but vibration increases
Solution Approach 1:
Multiple compressor units are merged into a single compressor unit that performs both medium temperature and low temperature compression functions. This consolidation reduces the number of moving parts and compression mechanisms, thereby reducing overall system vibration while maintaining the capability to serve both temperature zones.
3Adaptability or versatility
If complex pressure control is implemented, then temperature control capability is improved, but system stability deteriorates
Solution Approach 1:
An intermediate pressure expansion device is introduced as a mediator between the two compression stages. This device stabilizes the pressure transitions by providing a controlled expansion point at intermediate pressure, reducing pressure fluctuations and improving system stability while enabling both medium and low temperature operations.
4Device complexity
If inadequate oil management is present, then system simplicity is maintained, but reliability deteriorates
Solution Approach 1:
An oil management system with feedback control is implemented to monitor and regulate oil distribution to the compressor units. The system detects oil levels and flow conditions, then automatically adjusts oil supply to ensure adequate lubrication, thereby improving reliability without requiring overly complex manual intervention systems.
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 system achieves reduced compressor count, lower vibration, and improved stability by maintaining constant refrigerant pressure, and automatic oil balancing ensures sufficient lubrication, reducing defects and energy consumption.
Implementation Method 1
an intermediate pressure expansion device (6) expands the high pressure refrigerant
Implementation Method 2
In the condenser/gas cooler 4, the refrigerant is cooled down against a secondary medium
Implementation Method 3
a condensation takes place in the condenser/gas cooler 4, such that this refrigerant circuit element is referred to as condenser
Implementation Method 4
the refrigerant is further expanded to a pressure between 30 and 35 bar in the first expansion device (12) and evaporated in a first evaporator (14)
Data Source
Figure 1
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AI summary
A refrigeration system (2) comprises a condenser/gas cooler (4), an intermediate expansion device (6) and a refrigerant collecting container (8); a normal refrigeration branch (10) connecting the refrigerant collecting container (8) to the condenser/ gas cooler (4) said normal refrigeration branch (12) comprising a first expansion device (12), a first evaporator (14) and a compressor unit (16) of the normal refrigeration branch (10); a freezing branch (18) connecting the refrigerant collecting container (8) to the the condenser/ gas cooler (4), said freezing branch (18) comprising a second expansion device (20), a second evaporator (22), and a first compressor unit (24) and a second compressor unit (26) of said freezing branch (18), the first and second compressor units (24, 26) of the freezing branch (18) being connected in series. A flash gas line (28) is provided connecting the gas space of the refrigerant collecting container (8) to the line connecting the first compressor unit (24) to the second compressor unit (26) of said freezing branch (18). Refrigerant conduits for connecting said elements and for circulating a refrigerant therethrough are also provided.