Multi-Ejector Refrigeration Circuit Control to Prevent Reverse Flow
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Solution Overview
Problem
Existing control systems for ejector refrigeration circuits experience efficiency loss due to reverse flow when high pressure fluid and outlet fluid flow back to the secondary low pressure inlet, necessitating an improved control system that optimizes machine performance while preventing ejector reverse flow.
Innovation Solution
A system with a controller that generates maps based on predefined conditions, adjusting the opening percentages of multiple ejectors in an ejector refrigeration circuit to maintain a constant refrigerant flow rate and minimize reverse flow, using controllable variable ejectors connected in parallel configuration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If existing control systems operate ejectors dynamically, then the system can adapt to varying conditions, but reverse flow occurs when high pressure fluid and outlet fluid flow back to the secondary low pressure inlet, causing efficiency loss
Solution Approach 1:
The control system continuously monitors the operating conditions of the ejectors and adjusts the opening percentages based on real-time feedback. This feedback mechanism allows the system to maintain optimal performance across varying conditions while preventing reverse flow by detecting and responding to conditions that would cause high pressure fluid to flow back to the secondary low pressure inlet.
Solution Approach 2:
The system dynamically adjusts the opening percentages of multiple ejectors based on real-time operating conditions rather than using fixed positions. This dynamic control allows the ejectors to adapt to changing refrigeration loads and environmental conditions while maintaining efficient operation and preventing reverse flow through continuous optimization.
2Power
If multiple ejectors are used to improve compression efficiency, then the load on the compressor is reduced, but the control complexity increases and reverse flow risk increases
Solution Approach 1:
The compression function is segmented across multiple ejectors rather than using a single ejector or relying solely on the compressor. Each ejector handles a portion of the refrigerant flow, with independently controllable opening percentages. This segmentation allows the system to maintain high compression efficiency while distributing the control tasks across multiple components.
Solution Approach 2:
The control system adjusts the opening percentages of multiple ejectors as controllable parameters to optimize system performance. By varying these parameters based on operating conditions, the system achieves efficient compression across different loads while maintaining simple control logic through standardized adjustment patterns.
3Productivity
If ejector opening percentages are frequently adjusted to optimize performance, then the coefficient of performance is improved, but the number of ON/OFF switches increases reducing system robustness
Solution Approach 1:
The control system adjusts ejector opening percentages in periodic cycles rather than continuously, optimizing performance at key operating points. This periodic adjustment strategy maintains high coefficient of performance while reducing the frequency of actuator operations, thereby minimizing wear and improving system reliability.
Solution Approach 2:
The system uses a staged approach where ejectors are opened partially in sequence rather than all at once or to full opening. This partial action strategy allows fine-tuned control of refrigerant flow while reducing the number of complete ON/OFF cycles, thereby improving robustness while maintaining productivity.
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
Enhances the overall efficiency and robustness of the refrigeration system by minimizing ON/OFF switches and maintaining consistent refrigerant flow, thereby optimizing the coefficient of performance (COP).
Implementation Method 1
the ejectors improve efficiency in the refrigeration system by utilizing a high pressure to help compress a low pressure gas
Implementation Method 2
the ejectors include a primary high pressure inlet, a secondary low pressure inlet, and an outlet. When an ejector is used as part of the refrigeration system, the cooled refrigerant from the condenser enters each of the ejectors at the high pressure inlet and is expanded to a lower pressure at the outlet of each of the ejectors
Implementation Method 3
each of the plurality of maps is associated with a corresponding temperature of a heat rejecting heat exchanger
Data Source
Figure 1A
Figure 1B
Figure 2
AI summary
A system (100) for controlling a plurality of ejectors (101) in an ejector refrigeration circuit includes the plurality of ejectors (101) and a controller (104). Each of the plurality of ejectors (101) include a primary high pressure input port (101a), a secondary low pressure input port (101b), and an output port (101c). The controller (104) is coupled to each of the plurality of ejectors (101) and adapted to generate a plurality of maps (200, 200A, 200B, 200C) based on a set of predefined conditions. Each of the plurality of maps (200, 200A, 200B, 200C) is associated with a corresponding temperature of a heat rejecting heat exchanger (105). The controller (104) identifies a first map (200A) from the plurality of maps (200, 200A, 200B, 200C) associated with a first temperature of the heat rejecting heat exchanger (105) and an input signal from a first ejector (101') indicative of a flow rate of a refrigerant fluid through the first ejector (101'). Finally, the controller (104) adjusts opening percentages of the plurality of ejectors (101) based on the identified first map (200A).