Commercial Refrigeration PID Control Using Suction Pressure Linearization
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Commercial refrigeration systems using PID controllers face inefficiencies due to the non-linear relationship between suction pressure and temperature, leading to costly tuning requirements and inefficient operation across varying temperature ranges.
Innovation Solution
A controller that converts suction pressure to an equivalent temperature, allowing for linear control over a range of temperatures, thereby enabling efficient operation without the need for frequent tuning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If PID control algorithm is used with suction pressure as control variable, then cooling capacity can be maintained to match refrigeration load, but control efficiency deteriorates due to non-linear relationship between suction pressure and temperature
Solution Approach 1:
The patent transforms the control variable from suction pressure to equivalent evaporator temperature. By using temperature as the control parameter instead of pressure, the system achieves linear control characteristics that improve PID controller efficiency while maintaining accurate cooling capacity matching to refrigeration load.
2Reliability
If PID control algorithm is used with suction pressure, then cooling control is achieved, but additional tuning cost increases due to non-linear operating parameters
Solution Approach 1:
The patent converts the non-linear suction pressure parameter into an equivalent temperature parameter that provides linear control characteristics. This transformation eliminates the need for extensive PID tuning for different operating conditions, reducing commissioning costs and simplifying system setup while maintaining reliable cooling control.
3Loss of information
If suction pressure is used as control variable, then temperature representation is obtained, but measurement precision deteriorates due to non-linear relationship over temperature range
Solution Approach 1:
The patent introduces an intermediary conversion process that transforms suction pressure measurements into equivalent evaporator temperatures using refrigerant pressure-temperature relationships. This intermediary step converts the non-linear pressure measurement into a linear temperature representation, improving measurement precision across the full operating temperature range.
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 solution ensures stable and efficient operation of commercial refrigeration systems by maintaining optimal cooling capacity across different temperature settings, reducing energy usage and extending compressor lifespan.
Implementation Method 1
The pressure sensor senses a suction pressure for the compressors
Implementation Method 2
determines a temperature equivalent to the sensed suction pressure
Data Source
AI summary
Methods, systems, and apparatus for linearizing control of a commercial refrigeration system. In an embodiment of the invention, a controller is configured to receive a non-linear sensed suction pressure and convert the suction pressure to a linear temperature equivalent. The linear temperature equivalent is used by the controller to achieve efficient system operation over an entire range of operating temperatures.