Flash Tank Pressure Control for CO2 Ejector Refrigeration
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Solution Overview
Problem
Conventional refrigeration systems maintain constant flash tank pressure, which can lead to inefficiencies and increased energy usage, particularly in transcritical systems with ejectors, as they do not dynamically adjust pressure based on temperature changes.
Innovation Solution
A controller dynamically adjusts the pressure set point of the flash tank in a transcritical refrigeration system based on the gas cooler outlet temperature, increasing or decreasing the pressure difference (Δp) to optimize the efficiency of the ejector and parallel compression, thereby enhancing overall system efficiency and reducing energy consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If constant flash tank pressure is maintained, then system stability is preserved, but energy efficiency deteriorates due to inability to adapt to temperature changes
Solution Approach 1:
The patent implements dynamic pressure control by adjusting the flash tank pressure setpoint based on gas cooler outlet temperature. The controller modifies the pressure setpoint upward when temperature increases and downward when temperature decreases, transforming the static pressure maintenance system into a dynamic adaptive system that optimizes energy efficiency while maintaining operational stability.
Solution Approach 2:
The patent changes the pressure parameter of the flash tank dynamically based on temperature conditions. By adjusting the pressure setpoint as a variable parameter rather than maintaining it constant, the system adapts to changing thermal conditions, improving energy efficiency without compromising system reliability.
2Productivity
If flash tank pressure is increased to improve ejector efficiency, then ejector performance improves, but system complexity increases due to dynamic control requirements
Solution Approach 1:
The patent employs feedback control where the controller continuously monitors gas cooler outlet temperature and adjusts the flash tank pressure setpoint accordingly. This feedback mechanism enables the system to automatically optimize ejector efficiency based on real-time temperature conditions without requiring complex manual intervention or sophisticated control algorithms.
Solution Approach 2:
The system performs self-adjustment of flash tank pressure based on temperature feedback, eliminating the need for external complex control systems. The controller autonomously modifies pressure setpoints to maintain optimal ejector performance, making the system self-regulating and reducing overall control 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 dynamic pressure control improves the efficiency of the refrigeration system by aligning it with optimal operating conditions for either the ejector or parallel compressor, depending on temperature, resulting in more efficient operation and reduced energy usage.
Implementation Method 1
A gas cooler is operable to cool the CO2 refrigerant discharged from the medium temperature compressor and the parallel compressor
Implementation Method 2
A flash tank of the transcritical refrigeration system is operable to supply the CO2 refrigerant, in liquid form
Implementation Method 3
A low temperature compressor is operable to compress the CO2 refrigerant discharged from the low temperature refrigeration case
Data Source
AI summary
In certain embodiments, a transcritical refrigeration system provides refrigeration by circulating carbon dioxide (CO2) refrigerant through the system. A flash tank of the transcritical refrigeration system is operable to supply the CO2 refrigerant, in liquid form, to a low temperature refrigeration case and a medium temperature refrigeration case. A low temperature compressor is operable to compress the CO2 refrigerant discharged from the low temperature refrigeration case. A medium temperature compressor, a parallel compressor, and an ejector are each operable to compress the CO2 refrigerant discharged from the medium temperature refrigeration case, the CO2 refrigerant discharged from the low temperature compressor, and/or CO2 flash gas discharged from the flash tank. A gas cooler is operable to cool the CO2 refrigerant discharged from the medium temperature compressor and the parallel compressor. A controller is operable to dynamically adjust a pressure set point for the flash tank.