Economized device control for refrigeration systems
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Refrigeration systems in transport vehicles face challenges in maintaining optimal temperature conditions to prevent spoilage or freezing of perishable items, and existing control methods may not efficiently operate in economized mode, risking component damage.
Innovation Solution
A refrigeration unit with an economizer solenoid valve control system that calculates and compares pressures to determine when to open or close the valve, ensuring operation in economized mode while avoiding high-density refrigerant injection, using a flow process that monitors and adjusts based on compressor middle stage pressure and flash tank pressure relative to critical refrigerant pressures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the refrigeration system operates in economized mode with existing control methods, then energy efficiency is improved, but component damage risk increases due to high-density refrigerant injection
Solution Approach 1:
The control system continuously monitors flash tank pressure and compressor middle stage pressure, using this feedback to dynamically adjust economizer solenoid valve operation. This ensures the system operates in economized mode only when pressure conditions are appropriate, preventing high-density refrigerant injection that could damage the compressor while maintaining energy efficiency when safe to do so.
Solution Approach 2:
The system changes operational parameters by comparing actual pressures (flash tank pressure Pft and middle stage pressure Pmid) against critical pressure values (Pcrit - dP1 and Pcrit + dP2). Based on these parameter comparisons, the control method dynamically switches between economized mode and standard mode, optimizing energy efficiency while preventing compressor damage from inappropriate high-density refrigerant injection.
2Reliability
If pressure monitoring and calculation operations are added to control the economizer solenoid valve, then component protection is improved, but system complexity increases
Solution Approach 1:
The control system uses existing pressure sensors and the controller's built-in processing capabilities to perform the additional monitoring and calculation functions. No separate dedicated components are added - the system serves its own protection needs using resources already present in the refrigeration control architecture, thereby improving reliability without proportionally increasing complexity.
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 allows the refrigeration unit to operate efficiently and safely in economized mode, optimizing capacity and avoiding potential compressor damage, ensuring consistent temperature control for perishable goods.
Implementation Method 1
A refrigeration unit with an improved economized mode operation and/or use. The method includes: calculating a predicted compressor middle stage pressure (Pmid); comparing the predicted compressor middle stage pressure (Pmid) to a first pressure value (Pcrit-dP1) and comparing a flash tank pressure (Pft) to a second pressure value (Pcrit+dP2)
Implementation Method 2
A transport refrigeration unit is used to maintain proper temperatures within a transport cargo space. The refrigeration unit includes a compressor, a condenser, an expansion valve, an evaporator
Implementation Method 3
The evaporator is supplied with refrigerant at a selected temperature from the flash tank. The evaporator fan blows air across the evaporator, thus cooling the air to a selected or predetermined temperature
Implementation Method 4
The condenser receives refrigerant from the compressor and condenses the refrigerant to a liquid state. The condenser fan blows air across the condenser
Implementation Method 5
The expansion valve is positioned between the condenser and the evaporator. The expansion valve creates a pressure drop and flash gas in the refrigerant line
Implementation Method 6
The compressor compresses refrigerant vapor from the evaporator to a high pressure and temperature state, delivering refrigerant to the condenser
Data Source
Figure 1A
Figure 1B
Figure 2
AI summary
Methods and systems for operating a refrigeration unit are provided. The methods and systems include measuring a first characteristic of a refrigeration unit, calculating a compressor middle stage pressure based on the first measured characteristic, determining if a first comparison and a second comparison are satisfied based on the first measured characteristic and the calculated compressor middle stage pressure, and opening an economizer solenoid valve when the first comparison and the second comparison are satisfied.