Two-Stage Linear Compressor Control for Economizer Flow Ratio
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Solution Overview
Problem
Refrigeration systems using existing scroll and screw compressors face inefficiencies due to oil usage, fixed volume ratios, and compromised performance in economizer cycles, which affect cooling capacity and efficiency in display cases.
Innovation Solution
A control system for a dual-piston linear compressor that operates in an economizer cycle, using sensors to measure operating conditions and adjust piston stroke or frequency to achieve optimal volume flow ratios and secondary evaporating temperatures for maximum efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If scroll compressors use oil for operation, then lubrication is provided, but inefficient performance occurs due to oil film on evaporator and condenser surfaces
Solution Approach 1:
The patent extracts the oil lubrication function from the compression process by using a scroll compressor design that operates without oil, eliminating the harmful oil film deposition on heat exchange surfaces while maintaining reliable operation through alternative lubrication methods
2Device complexity
If scroll compressors operate with fixed volume ratio, then structural simplicity is maintained, but efficiency is compromised in economizer cycle
Solution Approach 1:
The patent applies dynamics by making the volume ratio adjustable rather than fixed, allowing the compressor to optimize its compression ratio according to operating conditions in the economizer cycle while maintaining structural simplicity through a controlled adjustment mechanism
3Productivity
If existing compressors operate in economizer cycle, then refrigeration capacity is increased, but efficiency is compromised due to fixed volume ratio
Solution Approach 1:
The patent changes the volume ratio parameter dynamically to optimize both refrigeration capacity and system efficiency in the economizer cycle, allowing the compressor to adapt its compression characteristics to match varying operating conditions and maximize performance
4Adaptability or versatility
If linear compressor provides variable capacity control, then cooling demand matching is improved, but device complexity increases
Solution Approach 1:
The patent implements variable capacity control through dynamic adjustment of piston stroke and frequency in the linear compressor design, enabling the system to match cooling demand while managing complexity through efficient control mechanisms
Data Source
AI summary
A refrigeration system includes a two-stage linear compressor having a first piston disposed in a first cylinder and a second piston disposed in a second cylinder. The linear compressor is operable in an economizer cycle wherein the first piston operates as a first stage of the economizer cycle and the second piston operates as a second stage of the economizer cycle. A controller is coupled to the linear compressor to control a volume flow ratio of the linear compressor. The controller stores a plurality of coefficients of performance for a range of particular operating conditions of the linear compressor and each coefficient of performance corresponds to a desired volume flow ratio and a desired secondary evaporating temperature. Based upon measured operating conditions of the linear compressor, the controller determines a highest coefficient of performance from the plurality of coefficients of performance and varies operation of at least one of the first and second pistons to achieve the desired volume flow ratio.