Refrigeration Capacity Control to Prevent Compressor Wear
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Solution Overview
Problem
Existing refrigeration system control methods lead to significant wear on compressors due to synchronized temperature fluctuations in display cases, causing frequent compressor switching and pressure fluctuations, which can result in suction pressure going out of control when both compressor and load control strategies counteract or amplify each other.
Innovation Solution
A method to control refrigeration systems with a compressor rack of variable capacity by independently managing suction pressure and compressor capacity, where suction pressure is maintained within a range by controlling refrigerant flow into evaporators and compressor capacity is adjusted based on demand signals from refrigeration entities, avoiding conflicting control strategies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If hysteresis control strategy is used to maintain display case temperature within a band, then temperature control is achieved, but compressor wear increases due to synchronized temperature cycles and frequent switching
Solution Approach 1:
The invention segments the control of display case temperatures by introducing staggered deadbands for different display cases. Instead of using a uniform temperature band for all cases, each case is assigned a slightly different deadband range, which desynchronizes their temperature cycling patterns and prevents simultaneous compressor switching.
Solution Approach 2:
The control system preemptively adjusts the deadband settings before synchronization can occur. By pre-configuring staggered deadbands, the system prevents the development of synchronized temperature cycles rather than reacting to them after they emerge.
2Stress or pressure
If suction pressure is controlled by adjusting compressor capacity based on suction pressure feedback, then suction pressure stability is improved, but control conflict arises when both compressor and load control strategies counteract or amplify each other
Solution Approach 1:
The invention extracts the suction pressure control function from the compressor capacity control and relocates it to the load control side. By controlling refrigerant flow into evaporators based on suction pressure feedback rather than adjusting compressor capacity, the system eliminates the conflict between compressor and load control strategies.
Solution Approach 2:
The invention introduces an intermediary control mechanism that mediates between suction pressure requirements and compressor operation. Rather than direct compressor capacity adjustment, the system uses refrigerant flow control as an intermediary to achieve suction pressure stabilization without direct compressor intervention.
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 reduces compressor wear by decoupling suction pressure control from compressor capacity adjustments, ensuring stable temperature ranges and matching refrigeration supply with demand, thereby minimizing compressor switching and pressure fluctuations.
Implementation Method 1
the evaporators absorb more heat from the surrounding air when the suction pressure is relatively low
Implementation Method 2
the control valve is activated and starts controlling a flow of refrigerant into the evaporator
Data Source
AI summary
A method for controlling a refrigeration system with a variable compressor capacity, and at least two refrigeration entities, e.g. display cases, includes controlling suction pressure by either permitting or preventing the flow of refrigerant into the evaporators of one or more refrigeration entities. The method also includes controlling compressor capacity based on a signal derived from one or more properties of the one or more refrigeration entities, said signal reflecting a possible difference between the current compressor capacity and a current refrigeration demand of the refrigeration system. The method reduces wear on compressors by avoiding switching them ON or OFF to the largest extent possible, and also prevents problems relating to conflicting control strategies due to control parameters, e.g. suction pressure, being determined based on two or more controllable parts, e.g. compressors and flow of refrigerant into refrigeration entities.