Compressor Oil Return Control by Adjusting Working Fluid Velocity
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Solution Overview
Problem
Refrigeration systems face challenges in efficiently managing oil return during low-load conditions, leading to oil logging in suction lines and reduced energy efficiency, as existing methods are complex and costly due to varying piping configurations.
Innovation Solution
A control system that adjusts operation parameters, such as compressor frequency and pressure set points, using processing devices and sensors to increase the velocity of the working fluid and oil flow rate, thereby enhancing oil return to compressors and simplifying piping design with uniform line sizing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional oil return methods are used with varying piping configurations, then oil can be returned to the compressor, but the system complexity and installation cost increase significantly
Solution Approach 1:
The patent changes the parameter of working fluid velocity by adjusting compressor operating frequency. When the compressor operates at lower frequencies, the working fluid velocity decreases, allowing oil to separate and return to the compressor naturally through the suction line without requiring complex piping configurations or additional oil return equipment.
2Use of energy by moving object
If compressor frequency is reduced to match load demand, then energy efficiency improves, but oil logging occurs in suction lines
Solution Approach 1:
The system continuously monitors compressor operating frequency and working fluid velocity, and adjusts the compressor frequency accordingly. When oil logging is detected or predicted (at low frequencies), the system provides feedback to adjust the frequency to prevent oil accumulation, thus maintaining both energy efficiency and preventing harmful oil logging effects.
3Ease of manufacture
If uniform piping sizes are used across all capacity points, then design and installation costs are reduced, but the system must operate efficiently across a wide range of conditions
Solution Approach 1:
The patent applies dynamic control of compressor operating frequency to adapt the system performance across different capacity points. By dynamically adjusting the frequency, the system maintains optimal working fluid velocity and oil return characteristics regardless of the capacity point, enabling uniform piping to perform effectively across all operating conditions.
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 solution effectively prevents oil logging, improves energy efficiency, and reduces design and installation costs by standardizing piping sizes across a wide range of capacity points.
Implementation Method 1
increasing 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.