Compressor Bearing Cooling via Purge Unit Refrigerant Supply
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Solution Overview
Problem
In refrigeration systems, particularly in oil-free centrifugal compressors, there is a challenge in ensuring consistent refrigerant flow to bearings for cooling and lubrication, which can lead to insufficiencies and inefficiencies in the compressor's operation.
Innovation Solution
A vapor compression system is designed with a purge unit that includes a vapor inlet line, a return line for contaminant-depleted refrigerant, and a supply flowpath extending to the bearings, allowing for controlled refrigerant delivery to the bearings, either through a mechanical pump or gravity feed, with a controller managing the flow to maintain optimal refrigerant levels and pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If refrigerant is directed to bearings for cooling and lubrication in oil-free centrifugal compressors, then bearing cooling and lubrication is achieved, but refrigerant flow insufficiency and inconsistency occur
Solution Approach 1:
The purge unit is pre-filled with refrigerant before compressor operation begins. This preliminary action ensures that refrigerant is immediately available for bearing cooling and lubrication from startup, eliminating the delay and flow inconsistency that would otherwise occur while the system establishes refrigerant circulation.
Solution Approach 2:
The purge unit acts as an intermediary reservoir between the refrigerant system and the bearings. It receives refrigerant from the refrigerant system and delivers it to the bearings through dedicated feed passages, mediating the flow to ensure consistent delivery regardless of fluctuations in the main refrigerant system.
2Ease of operation
If a mechanical pump is used to deliver refrigerant to bearings, then refrigerant flow control is improved, but device complexity increases
Solution Approach 1:
The purge unit is designed to deliver refrigerant to the bearings through gravity feed and pressure differential without requiring an additional mechanical pump. The unit self-regulates refrigerant flow to the bearings using the existing system pressure and gravity, eliminating the need for extra pumping components while maintaining adequate flow control.
3Use of energy by moving object
If the purge unit operates intermittently, then energy consumption is reduced, but refrigerant supply to bearings may become insufficient
Solution Approach 1:
The purge unit is pre-filled with refrigerant before the compressor operates and maintains a reservoir of refrigerant ready for delivery. This preliminary preparation ensures that even when the purge unit operates intermittently, there is always refrigerant available in the unit to supply the bearings, maintaining reliable supply while allowing energy-efficient intermittent operation.
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 ensures reliable refrigerant supply to the bearings, enhancing the compressor's efficiency and performance by maintaining optimal refrigerant levels and pressure, thereby improving the overall operation of the refrigeration system.
Implementation Method 1
A flow of refrigerant is diverted from the main refrigerant flowpath and passed into a purge tank where it is cooled to condense refrigerant while leaving noncondensable contaminants in vapor form
Implementation Method 2
A first heat exchanger is coupled to the discharge port to receive refrigerant driven in a downstream direction
Implementation Method 3
An expansion device is downstream of the first heat exchanger
Implementation Method 4
A second heat exchanger is downstream of the expansion device and coupled to the suction port to return refrigerant
Data Source
AI summary
A compressor (22) has a housing assembly (40) with a suction port (24), a discharge port (26), and a motor compartment (60). An electric motor (42) has a stator (62) within the motor compartment and a rotor (64) within the stator. The rotor is mounted for rotation about a rotor axis (500). One or more working impellers (44) are coupled to the rotor to be driven by the rotor in at least a first condition so as to draw fluid in through the suction port and discharge the fluid from the discharge port. An inlet guide vane (IGV) array (174) is between the suction port (24) and the one or more impellers (44). One or more bearings (66, 68) support the rotor (64) and/or the one or more impellers (44). A purge unit (400) has a vapor inlet line (410) for receiving a refrigerant flow and a return line (414, 417A, 417B) for returning a contaminant-depleted refrigerant flow. A supply flowpath (407A, 407B) for supplying refrigerant to the bearings extends from the purge unit.