System and method for lubricant separation and return control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In HVACR systems with multiple compressors connected in parallel, lubricant separation and return are inefficient, leading to low lubricant levels in compressor manifolds when compressors are staged off, due to gaseous heat transfer fluid flowing through inactive compressors and limited bypass areas, preventing lubricant drainage into the sump.
Innovation Solution
A lubricant separator is used to separate the heat transfer fluid into a lubricant-rich and a lubricant-free portion, with the lubricant-rich portion directed to the compressor sumps via a dedicated conduit and the lubricant-free portion allowed to pass through to the suction inlets, preventing lubricant from entering the suction conduit and ensuring it drains directly into the sump, and a lubricant transfer conduit system with pressure differentials manages lubricant flow between compressors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If gaseous heat transfer fluid flows through inactive compressors, then the compressors can be staged off for load management, but lubricant drainage into the sump is prevented due to limited bypass areas
Solution Approach 1:
The suction conduit is segmented into two separate paths: a lubricant return path with sufficient bypass area leading to the sump, and a suction path leading to the compressor inlet. This segmentation allows gaseous heat transfer fluid to flow through the compressor for staging operations while lubricant can drain independently through the dedicated return path without being restricted by limited bypass areas.
Solution Approach 2:
A lubricant return conduit acts as an intermediary pathway between the suction conduit and the sump. This separate conduit provides adequate bypass area specifically for lubricant flow, decoupling the lubricant drainage function from the suction flow path and enabling effective lubricant return even when compressors are staged off.
2Quantity of substance
If lubricant separator directs lubricant-rich portion to suction conduit, then lubricant can reach compressors, but lubricant levels become unmanageable and reliability decreases
Solution Approach 1:
The lubricant separator output is segmented into two distinct paths: the lubricant-rich portion is directed to the lubricant return conduit leading to the sump, while the lubricant-free portion is directed to the suction conduit. This segmentation ensures proper lubricant distribution and prevents excessive lubricant accumulation in the compressor manifold, maintaining reliable lubricant level management.
3Productivity
If dedicated lubricant return conduit is implemented, then lubricant drainage efficiency improves, but device complexity increases
Solution Approach 1:
The lubricant return conduit is merged with the existing suction conduit system at the lubricant separator location, rather than creating a completely separate system. The lubricant-rich portion from the separator combines with the return flow in the dedicated conduit, while the lubricant-free portion continues to the suction inlet. This merging approach improves lubricant drainage efficiency while minimizing additional system complexity by integrating with existing components.
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 effectively manages lubricant levels across all load steps and conditions, improving compressor reliability by ensuring lubricant is directed into the sump instead of rerouting through the suction line, maintaining adequate lubrication and preventing lubricant loss.
Implementation Method 1
The lubricant sump is disposed at a relatively vertically lower portion of the compressor such that lubricant can be collected in the lubricant sump via gravitational force
Implementation Method 2
The second fluid outlet includes a nozzle disposed within a flow passage of the lubricant separator such that a space is maintained between an outer surface of the nozzle and an inner surface of the flow passage
Data Source
AI summary
An HVACR system includes first and second compressors arranged in parallel, a condenser, an expansion device, an evaporator, and a lubricant separator fluidly connected. The first compressor includes a first lubricant sump and a first suction inlet. The second compressor includes a second lubricant sump and a second suction inlet. The lubricant separator is disposed between the evaporator and the first and second compressors, and includes a fluid inlet and two fluid outlets. A first of the two fluid outlets is fluidly connected to at least one of the first and second lubricant sumps. A second of the two fluid outlets is fluidly connected to the first and second suction inlets. The second fluid outlet includes a nozzle disposed within a flow passage of the lubricant separator such that a space is maintained between an outer surface of the nozzle and an inner surface of the flow passage.