Compressor with flooded start control
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Solution Overview
Problem
Compressors in refrigeration systems face operational issues when flooded with liquid refrigerant, leading to lubricant depletion and potential damage due to lack of lubrication during startup, which traditional crankcase heaters attempt to mitigate but are inefficient and energy-intensive.
Innovation Solution
A system and method for flooded start control that uses sensor data to manage compressor operation with on/off cycles, allowing gradual liquid removal and heat-up, reducing the need for crankcase heaters and minimizing lubricant loss, thereby extending compressor life and reducing energy consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If crankcase heaters are used to prevent liquid migration and flooded compressor state, then the compressor is protected from lubricant depletion, but energy consumption increases and the solution is less effective for fast liquid migration rates
Solution Approach 1:
The system performs preliminary detection of liquid migration rate before compressor startup and takes preventive action by adjusting startup parameters. The control module detects the liquid migration rate and, when fast migration is detected, implements a delayed startup or modified startup sequence that allows liquid to be pumped out first, preventing flooded conditions without requiring continuous heating.
Solution Approach 2:
The invention replaces the thermal field approach (crankcase heaters) with a control system that uses detection and timing control. Instead of continuously applying heat to prevent liquid migration, the system detects migration rates and uses controlled startup timing to manage liquid removal, substituting thermal protection with intelligent control.
2Productivity
If the compressor operates in a flooded state and quickly pumps out all liquid refrigerant and dissolved lubricant, then liquid removal is efficient, but the compressor operates without lubrication causing damage to internal moving parts
Solution Approach 1:
The system performs preliminary detection of liquid migration rate before compressor startup. When fast liquid migration is detected, the control module implements a delayed startup or modified startup sequence that allows liquid to be pumped out during the delay period, but controls the timing to ensure lubricant returns before full compression operation begins, preventing lubricant depletion.
Solution Approach 2:
The invention implements periodic control through delayed startup sequences and cyclic operation patterns. When flooded conditions are detected, the system uses a delay period followed by controlled startup cycles, allowing liquid removal during the delay and controlled operation cycles, ensuring lubricant returns during off-periods or delay periods before resuming normal operation.
3Quantity of substance
If traditional crankcase heaters are used to heat the crankcase, then liquid migration is reduced for slow rates, but the heating capacity is insufficient for fast liquid migration rates
Solution Approach 1:
The system dynamically adjusts compressor startup parameters based on real-time detection of liquid migration rate. When slow migration is detected, normal startup procedures are used. When fast migration is detected, the control module implements delayed startup or modified startup sequences, allowing the system to adapt its response to the actual migration conditions rather than using a fixed heating approach.
Solution Approach 2:
The invention implements feedback control by continuously monitoring liquid migration rate and adjusting startup parameters accordingly. The control module detects the migration rate and uses this information to determine the appropriate startup strategy, creating a closed-loop system that adapts to actual system conditions rather than relying on predetermined heating levels.
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 effectively manages liquid refrigerant and lubricant in compressors, enhancing operational efficiency, reducing energy costs, and prolonging compressor reliability by allowing gradual liquid removal and heat-up during startup.
Implementation Method 1
crankcase heaters have been used to heat the crankcase of the compressor to prevent or reduce liquid migration to the compressor
Implementation Method 2
the compressor may quickly pump out all of the liquid refrigerant, along with all of the dissolved lubricant, in the compressor
Implementation Method 3
the lubricant normally present in the lubricant sump can dissolve in the liquid refrigerant, resulting in a liquid mixture of refrigerant and lubricant
Data Source
AI summary
A system and method for flooded start control of a compressor having a crankcase heater are provided. A control module receives sensed data from a sensor, determines a current rate of liquid migration into the compressor, and compares the current rate with first and second predetermined thresholds. The control module operates the compressor in a flooded-start control mode, including operating the compressor according to at least one cycle with a first time period when the compressor is on and a second time period when the compressor is off. The control module operates the compressor in the flooded start control mode when the current rate is greater than the first predetermined threshold, activates the crankcase heater when the current rate is between the first and second predetermined thresholds, and operates the compressor without the flooded start control mode when the current rate is less than the second predetermined threshold.