Vapor compression system with refrigerant-lubricated compressor
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Solution Overview
Problem
Centrifugal compressors face challenges in operating without a dedicated oil system, requiring effective lubrication methods that do not interfere with heat transfer or other operations, while maintaining efficient refrigerant delivery to bearings.
Innovation Solution
A vapor compression system with dual lubricant flowpaths and a shared pump, controlled by sensors measuring outlet pressure, vibration, or motor current, to selectively switch between lubricant sources from the heat rejection and heat absorption heat exchangers, ensuring optimal lubrication and refrigerant flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a dedicated oil system is used for compressor lubrication, then reliable bearing lubrication is achieved, but oil interference with heat transfer and system complexity increase
Solution Approach 1:
The patent merges the lubrication function with the existing refrigerant circulation system by using refrigerant as the lubricant carrier. The refrigerant absorbs oil vapor in evaporator regions and delivers it to compressor bearings, eliminating the need for a separate dedicated oil system while maintaining reliable bearing lubrication.
Solution Approach 2:
The refrigerant serves multiple functions simultaneously: it acts as the working fluid for heat transfer, as a carrier for oil transport, and as a cooling medium. This multi-functionality eliminates the need for separate dedicated oil circulation systems, reducing overall system complexity while maintaining lubrication reliability.
2Loss of energy
If oil is removed from the system to prevent heat transfer interference, then heat transfer efficiency improves, but bearing lubrication reliability deteriorates
Solution Approach 1:
The refrigerant acts as an intermediary carrier that transports oil vapor from evaporator regions where oil would interfere with heat transfer, to compressor bearings where lubrication is needed. This mediator approach allows oil to be delivered to bearings without being present in large quantities in heat transfer zones, maintaining both heat transfer efficiency and lubrication reliability.
Solution Approach 2:
The system uses the refrigerant's natural circulation and phase change properties to automatically transport oil vapor to bearings. The refrigerant absorbs oil vapor in low-pressure regions and delivers it to high-pressure bearing zones, creating a self-regulating lubrication system that maintains reliability without requiring additional oil management components.
3Device complexity
If refrigerant-lubricated bearings are used without a dedicated oil system, then system complexity is reduced, but maintaining high-quality refrigerant delivery to bearings becomes difficult
Solution Approach 1:
The system incorporates sensors that monitor refrigerant conditions and oil vapor distribution, providing feedback to control mechanisms. This feedback loop ensures that refrigerant quality is maintained and oil vapor is properly delivered to bearings, compensating for the absence of a dedicated oil system and maintaining precise control over lubrication quality.
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 solution enables efficient lubrication of compressor bearings without a dedicated oil system, maintaining high-quality refrigerant delivery and minimizing oil interference with heat transfer operations, thus enhancing the overall performance and efficiency of the compressor system.
Implementation Method 1
a sensor positioned to measure at least one of an outlet pressure, vibration, and motor current of the lubricant pump
Implementation Method 2
a sensor positioned to measure at least one of an outlet pressure, vibration, and motor current of the lubricant pump
Data Source
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AI summary
A vapor compression system (20; 400; 420) comprises: a compressor (22) having a suction port (40) and a discharge port (42); a heat rejection heat exchanger (58) coupled to the discharge port to receive compressed refrigerant; a heat absorption heat exchanger (88); a first lubricant flowpath (120, 126) from the heat rejection heat exchanger to the compressor; a second lubricant flowpath (121, 126) from the heat absorption heat exchanger to the compressor; at least one lubricant pump (190); and a controller (900) configured to control lubricant flow along the first lubricant flowpath and the second lubricant flowpath based on a sensed fluctuation.