Compressor Flooded Start Control Using Periodic On/Off Cycles
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Solution Overview
Problem
Compressors in refrigeration systems often become flooded with liquid refrigerant, leading to the dissolution of lubricant and potential damage due to operation without lubrication, which can reduce compressor reliability and lifespan.
Innovation Solution
The implementation of a flooded start control system that uses one or more short on/off cycles to gradually pump liquid from the compressor, allowing more time for refrigerant and lubricant to return before the compressor is emptied, thereby reducing the need for crankcase heaters and lowering energy consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the compressor operates continuously in a flooded state, then liquid refrigerant is quickly pumped out, but the compressor operates without lubrication causing damage to moving parts
Solution Approach 1:
The patent implements periodic on/off cycles during compressor startup when flooded with liquid refrigerant. The controller alternates between running and stopping the compressor motor for predetermined time periods, allowing liquid refrigerant to be gradually pumped out while preventing complete depletion of lubricant. This periodic operation resolves the contradiction by balancing rapid liquid removal with maintaining adequate lubrication throughout the startup phase.
2Reliability
If a crankcase heater is used to heat the compressor, then liquid migration is reduced, but energy costs increase
Solution Approach 1:
The patent enables the compressor to protect itself from flooding through automated periodic cycling during startup without requiring external heating assistance. The control system detects flooded conditions and autonomously implements the on/off cycling strategy, allowing the system to self-regulate liquid refrigerant management without consuming additional energy through crankcase heaters.
Solution Approach 2:
The patent changes the operational parameters of the compressor during flooded startup conditions by implementing variable on/off cycles with predetermined time periods. This dynamic parameter adjustment allows the system to adapt to flooded conditions and gradually pump out liquid refrigerant without maintaining continuous heating, thereby reducing energy consumption compared to traditional crankcase heater approaches.
3Quantity of substance
If the compressor is stopped for long periods, then liquid refrigerant migrates to the compressor, but frequent startup cycles increase wear
Solution Approach 1:
The patent implements periodic on/off cycling during startup that gradually reduces liquid refrigerant accumulation without requiring frequent prolonged shutdowns. By using controlled cycles with predetermined time periods, the system manages liquid migration while minimizing mechanical wear associated with frequent full shutdowns and restarts.
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 improves compressor operation by managing liquid refrigerant and lubricant more efficiently, reducing the risk of damage, and decreasing energy costs by minimizing the use of crankcase heaters.
Implementation Method 1
The compressor may include an electric motor coupled to the crankshaft
Implementation Method 2
the crankshaft drives an orbiting scroll member of a scroll set
Implementation Method 3
the orbiting scroll member engages with a stationary scroll member to compress a refrigerant gas
Implementation Method 4
The lubricant sump can collect lubricant that lubricates the moving parts of the compressor
Implementation Method 5
crankcase heaters have been used to heat the crankcase of the compressor to prevent or reduce liquid migration
Data Source
Figure 1A~1B
Figure 2A~2B
Figure 3
AI summary
A system and method for flooded start control of a compressor for a refrigeration system is provided. A temperature sensor generates temperature data corresponding to at least one of a compressor temperature and an ambient temperature. A control module receives the temperature data, determines an off-time period since the compressor was last on, determines an amount of liquid present in the compressor based on the temperature data and the off-time period, compares the amount of liquid with a predetermined threshold, and, when the amount of liquid is greater than the predetermined threshold, operates the compressor according to at least one cycle including a first time period during which the compressor is on and a second time period during which the compressor is off.