Compressor Flooded Start Control Using Cycled On-Off Operation
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Solution Overview
Problem
Compressors in refrigeration systems face operational issues due to flooding with liquid refrigerant, leading to lubricant depletion and potential damage, especially during startup, as traditional crankcase heaters are inefficient and increase energy costs.
Innovation Solution
A system and method for flooded start control that uses ambient and compressor temperature sensors to implement short on/off cycles, allowing gradual pumping of liquid refrigerant and lubricant, reducing the need for crankcase heaters and minimizing lubricant depletion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If crankcase heaters are used to heat the compressor crankcase to prevent liquid migration, then liquid refrigerant migration is reduced, but energy consumption increases
Solution Approach 1:
The compressor uses its own operation cycles to naturally manage liquid refrigerant through gradual pumping, eliminating the need for external crankcase heaters. The system serves itself by using controlled on/off cycles to achieve liquid management without additional energy-consuming heating components.
Solution Approach 2:
The compressor operates in periodic on/off cycles that allow gradual pumping of liquid refrigerant. This periodic operation creates intervals where liquid can be managed and returned to the suction inlet, preventing flooded states without continuous energy input from heaters.
2Productivity
If the compressor operates continuously to pump out liquid refrigerant, then liquid removal is fast, but lubricant depletion occurs
Solution Approach 1:
The compressor uses periodic on/off cycles instead of continuous operation. During on-periods, liquid refrigerant is gradually pumped out; during off-periods, lubricant has time to return to the crankcase. This periodic action balances liquid removal with lubricant replenishment, preventing both flooding and lubricant depletion.
Solution Approach 2:
Before the compressor pumps out all liquid refrigerant, the system allows intervals where lubricant returns to the crankcase. This preliminary action of lubricant return prevents lubricant depletion before it occurs, maintaining proper lubrication during the liquid removal process.
3Productivity
If the compressor operates without lubrication to quickly remove liquid refrigerant, then liquid pumping is efficient, but compressor damage occurs
Solution Approach 1:
The compressor operates in periodic cycles that prevent continuous operation without lubrication. The on/off pattern ensures that during off-periods, lubricant returns to the crankcase, maintaining lubrication protection while still achieving liquid refrigerant removal during on-periods, thus preventing compressor damage.
Solution Approach 2:
The system prepares for potential lubricant depletion by using periodic cycles that allow lubricant return before complete depletion occurs. This beforehand cushioning ensures lubricant is replenished in advance, preventing the harmful condition of operating without lubrication and avoiding compressor damage.
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 enhances compressor operation by allowing sufficient time for lubricant return, reduces energy consumption, and decreases the risk of premature wear, thereby improving compressor reliability and extending its lifespan.
Implementation Method 1
liquid refrigerant in the refrigeration system generally migrates to the coldest component in the system
Implementation Method 2
the compressor lubricant is generally soluble with the liquid refrigerant. As such, when the compressor is flooded with liquid refrigerant, the lubricant normally present in the lubricant sump can dissolve in the liquid refrigerant
Implementation Method 3
crankcase heaters have been used to heat the crankcase of the compressor to prevent or reduce liquid migration to the compressor
Data Source
AI summary
A system and method for flooded start control of a compressor are provided. An ambient temperature sensor generates ambient temperature data and a compressor temperature sensor generates compressor temperature data. A control module receives the ambient temperature data and the compressor temperature data, determines whether the outdoor ambient temperature is rising faster than the compressor temperature, determines whether the outdoor ambient temperature is greater than the compressor temperature by more than a predetermined threshold for more than a predetermined time period, and, in response to the outdoor ambient temperature rising faster than the compressor temperature and the outdoor ambient temperature being greater than the compressor temperature by more than the predetermined threshold for more than the predetermined time period, 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.