Multi-Stage Compressor Oil Balancing in Refrigeration Cycles
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Solution Overview
Problem
In refrigerating cycle apparatuses with multiple compressors, oil unbalance occurs due to differential oil flow during multi-stage compression, leading to frictional losses, increased power consumption, and potential compressor damage, especially when compressors are connected in series, and existing solutions complicate the structure and reduce cooling efficiency.
Innovation Solution
A refrigerating cycle apparatus with a controller and oil balancing device that determines oil concentration in compressors and uses a refrigerant switching valve to redistribute oil between primary and secondary compressors based on integrated driving time or oil level sensors, ensuring balanced oil distribution through specific oil collection and balancing algorithms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple compressors are connected in series for multi-stage compression, then compression efficiency is improved, but oil unbalance occurs between compressors leading to increased frictional loss and power consumption
Solution Approach 1:
An oil balancing container is introduced as an intermediary device between the first and second compressors. This container collects excess oil from the first compressor and supplies it to the second compressor, acting as a mediator to redistribute oil and eliminate the oil unbalance that causes increased frictional loss and power consumption in multi-stage compression systems
Solution Approach 2:
The system changes the oil distribution parameter by using a solenoid valve to control oil flow direction. During defrosting operation, the solenoid valve redirects oil flow to accumulate oil in the oil balancing container, which then supplies oil to the second compressor during normal operation, thereby adjusting oil parameters to reduce frictional loss
2Reliability
If an oil balancing container is separately installed outside the compressors, then oil unbalance between compressors is resolved, but the apparatus occupies more space and has complicated structure with increased flow resistance
Solution Approach 1:
The oil balancing container is merged with the refrigerant circulation system by positioning it at the discharge side of the first compressor and integrating it with existing refrigerant pipes. The container utilizes the pressure differential of refrigerant flow to automatically control oil movement, eliminating the need for separate complex oil balancing mechanisms and reducing overall system complexity
Solution Approach 2:
The oil balancing container serves multiple functions: it acts as an oil collection reservoir, an oil distribution mechanism, and a pressure equalization chamber. By integrating these functions into a single component that leverages existing refrigerant flow patterns, the system achieves reliable oil balancing without adding separate dedicated devices for each function
3Duration of action of moving object
If oil is discharged from compressors into the refrigerating cycle during operation, then compression continues, but oil accumulates in one compressor causing lack of oil in other compressors
Solution Approach 1:
The system implements periodic oil balancing through timed defrosting cycles. During these periodic defrosting intervals, the solenoid valve redirects refrigerant and oil flow to accumulate oil in the oil balancing container. This periodic action ensures that oil is redistributed to the second compressor before the next compression cycle, maintaining reliable oil distribution during continuous operation
Solution Approach 2:
The oil balancing container pre-accumulates oil during defrosting periods before it is needed for the second compressor's compression cycle. This preliminary action of storing oil in advance ensures that the second compressor receives adequate oil supply at the start of each compression cycle, preventing oil deficiency and maintaining reliability
Data Source
AI summary
A refrigerating cycle apparatus and a method of operating the same are provided. For a refrigerating cycle having a plurality of compressors connected in series for multi-stage compression, an inner space of each compressor and a pipe of the refrigerating cycle may be connected via an oil collection pipe, and oil may be discharged into the refrigerating cycle by pressure reversal during a pressure balancing operation, so as to allow the discharged oil to be collected into a high-stage compressor or a low-stage compressor. Accordingly, an amount of oil may be uniformly maintained in each of the plurality of compressors to prevent losses due to friction and/or increases in power consumption due to a lack of oil in one or more of the compressors. The structure of a device and pipes for performing oil balancing between the compressors may be simplified to enhance efficiency of the compressors.