Ejector system and methods of operation
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Solution Overview
Problem
Ejector refrigeration systems face inefficiencies due to the baseline ejector being oversized for typical operating conditions, leading to reduced efficiency and potential damage from high-side pressures, and existing control methods lack flexibility in managing refrigerant flow and pressure across the system.
Innovation Solution
The introduction of a bypass flowpath that rejoins the primary flowpath upstream of the separator, allowing for a smaller, more efficient ejector and incorporating a control system with a variable orifice expansion valve and controller to manage refrigerant flow, reducing compressor temperature and pressure, and optimizing the system's operation by adjusting the fraction of flow through the bypass path based on sensed pressures and temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a baseline ejector is used to handle maximum anticipated load conditions, then the system can manage high-side pressures, but the ejector becomes oversized for typical operating conditions leading to reduced efficiency
Solution Approach 1:
The refrigerant flow is segmented into two paths: a primary path through the ejector for typical conditions, and a bypass path for maximum load conditions. This segmentation allows the ejector to be sized appropriately for normal operation while the bypass handles peak demands, resolving the contradiction between ejector size and efficiency.
Solution Approach 2:
The system dynamically switches between the ejector-only path and the bypass path based on operating conditions. The bypass flowpath is activated when high-side pressures indicate maximum load conditions, allowing the system to adapt its configuration to maintain ejector efficiency across varying operating conditions.
2Object-affected harmful factors
If the ejector is sized for maximum load conditions, then high-side pressure management is possible, but the ejector operates inefficiently at typical conditions
Solution Approach 1:
The flowpath is segmented into an ejector path and a bypass path, allowing the ejector to handle only the portion of flow necessary for efficient operation at typical conditions, while the bypass handles excess flow during maximum load conditions.
Solution Approach 2:
The bypass flowpath acts as an intermediary path that diverts excess refrigerant flow away from the ejector during maximum load conditions, preventing the ejector from operating inefficiently while still allowing the system to manage high-side pressures effectively.
3Productivity
If a bypass flowpath is added to the system, then ejector efficiency and compressor temperature management improve, but device complexity increases
Solution Approach 1:
The bypass flowpath serves multiple functions: it improves ejector efficiency by preventing oversized operation, manages compressor temperature during high load conditions, and provides a simple alternative path for refrigerant flow. This multi-functionality justifies the added complexity by delivering multiple benefits from a single structural addition.
Solution Approach 2:
The bypass flowpath acts as an intermediary structure that connects existing system components (compressor discharge to separator or evaporator inlet) without requiring major system redesign, thereby adding functionality with relatively minimal increase in overall device 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 configuration enhances the system's efficiency by allowing the ejector to operate more efficiently at normal conditions, reduces compressor temperature, and prevents damage by managing high-side pressures, while also enabling a smaller evaporator and separator, thus improving overall refrigeration performance.
Implementation Method 1
a bypass flowpath bypassing the motive nozzle and rejoining the first flowpath at essentially separator pressure but away from the separator
Implementation Method 2
increasing a fraction of the total flow passed along the bypass flowpath so as to reduce a compressor temperature
Implementation Method 3
The primary refrigerant flow enters the inlet and then passes into a convergent section of the motive nozzle. It then passes through a throat section and an expansion (divergent) section through an outlet of the motive nozzle. The motive nozzle accelerates the flow and decreases the pressure of the flow.
Implementation Method 4
The pressure reduction caused to the primary flow by the motive nozzle helps draw the secondary flow into the outer member
Implementation Method 5
The outer member also has a divergent section or diffuser downstream of the elongate throat or mixing section. The resulting combined flow is a liquid/vapor mixture and decelerates and recovers pressure in the diffuser while remaining a mixture.
Implementation Method 6
Upon entering the separator, the flow is separated back into the flows and the flow passes as a gas through the compressor suction line as discussed above. The flow passes as a liquid to the expansion valve
Implementation Method 7
The flow may be expanded by the valve (e.g., to a low quality (two-phase with small amount of vapor)) and passed to the evaporator
Implementation Method 8
Within the evaporator, the refrigerant absorbs heat from a heat transfer fluid (e.g., from a fan-forced air flow or water or other liquid) and is discharged from the outlet as the aforementioned gas
Implementation Method 9
In the heat rejection heat exchanger, the refrigerant loses/rejects heat to a heat transfer fluid (e.g., fan-forced air or water or other fluid)
Data Source
AI summary
A vapor compression system (200; 300; 400) has: a compressor (22); a first heat exchanger (30); a second heat exchanger (64); an ejector (38); separator (48); and an expansion device (70). A plurality of conduits are positioned to define a first flowpath sequentially through: the compressor; the first heat exchanger; the ejector from a motive flow inlet through (40) an outlet (44); and the separator, and then branching into: a first branch returning to the compressor; and a second branch passing through the expansion device and second heat exchanger to a secondary flow inlet (42). The plurality of conduits are positioned to define a bypass flowpath (202; 302; 402) bypassing the motive flow inlet and rejoining the first flowpath at essentially separator pressure but away from the separator.