Compressor Oil Return Control Using Periodic High-Speed Operation
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Solution Overview
Problem
Refrigeration systems face challenges in efficiently managing oil return to compressors, particularly during low-load conditions, which can lead to oil logging in suction lines and reduced energy efficiency.
Innovation Solution
A method that involves a processing device receiving operation information from compressors and comparing it to thresholds, adjusting operation parameters to increase the velocity of the working fluid or the flow rate of oil in the piping assembly, thereby enhancing oil return to the compressors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the refrigeration system operates at low-load conditions, then energy consumption is reduced, but oil logging occurs in suction lines reducing compressor efficiency
Solution Approach 1:
The system implements periodic high-speed operation cycles where the compressor periodically increases its operating speed to a high-speed state for a predetermined time period, even during low-load conditions. This periodic high-speed action creates sufficient oil flow velocity to prevent oil logging in the suction lines, while the compressor returns to normal low-speed operation between these periods, maintaining overall energy efficiency.
Solution Approach 2:
The system dynamically adjusts the compressor operating speed between a normal operating speed and a high operating speed based on detected oil return conditions. The control device monitors oil flow velocity and automatically transitions the compressor to high-speed operation when oil logging is detected, and returns to normal speed when oil return is sufficient, creating a dynamic adaptation to varying load conditions.
2Reliability
If the compressor operates at high speed continuously, then oil return to compressor is improved, but energy consumption increases
Solution Approach 1:
The system implements periodic high-speed operation cycles where the compressor periodically increases its operating speed to a high-speed state for a predetermined time period, even during low-load conditions. This periodic high-speed action creates sufficient oil flow velocity to prevent oil logging in the suction lines, while the compressor returns to normal low-speed operation between these periods, maintaining overall energy efficiency.
Solution Approach 2:
The system changes the operating speed parameter of the compressor between two distinct states: a normal operating speed for energy-efficient operation and a high operating speed for ensuring adequate oil return. The control device adjusts this parameter dynamically based on monitored conditions, switching between parameter values rather than maintaining a continuous variable adjustment.
3Reliability
If complex piping configurations are used to return oil to compressor, then oil return is improved, but device complexity increases
Solution Approach 1:
The system uses the compressor's own operating characteristics to achieve oil return. By utilizing the velocity of the refrigerant suction flow and periodically increasing compressor speed, the system creates self-generated oil flow that returns oil to the compressor without requiring additional active components or complex piping configurations. The compressor essentially services its own oil return needs through its normal operation cycles.
Solution Approach 2:
The invention extracts the active oil return mechanism from the piping system and places it in the compressor operation itself. Instead of using separate pumps, valves, or complex piping arrangements to actively return oil, the system extracts the oil return function from the compression process by utilizing the refrigerant flow velocity and periodic high-speed operation to naturally propel oil back to the compressor.
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 approach helps prevent oil logging, simplifies piping design, and improves energy efficiency by ensuring effective oil return to the compressors even during low-load conditions.
Implementation Method 1
Changing the operation parameter increases at least one of: (i) a velocity of a working fluid in a piping assembly fluidly coupled to the one or more compressors, or (ii) a flow rate of an oil in the piping assembly flowing into the one or more compressors
Data Source
AI summary
A method includes receiving, by a processing device and from a variable frequency drive coupled to one or more compressors, operation information of the one or more compressors. The method also includes comparing the operation information of the one or more compressors to an operation threshold and determining that the operation information satisfies the operation threshold. The method also includes changing, based on the determination that the operation information of the one or more compressors satisfies the operation threshold, an operation parameter of a component of the refrigeration system. Changing the operation parameter increases at least one of: (i) a velocity of a working fluid in a piping assembly fluidly coupled to the one or more compressors, or (ii) a flow rate of an oil in the piping assembly flowing into the one or more compressors.