Ejector
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Solution Overview
Problem
Ejector refrigeration systems face inefficiencies due to large area ratios in controllable nozzles, leading to overexpansion and associated losses in efficiency, particularly when trying to maintain optimal pressure ratios for refrigerant flow.
Innovation Solution
The introduction of a mechanism to vary both the throat and exit areas of the motive nozzle using a needle and actuator system, allowing for simultaneous control of the effective areas to maintain optimal expansion ratios and reduce energy losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a controllable nozzle with large area ratio is used in the ejector, then the pressure ratio can be adjusted, but overexpansion occurs leading to efficiency losses
Solution Approach 1:
The nozzle is divided into two independently controllable sections: a throat section with adjustable area and an exit section with adjustable area. This segmentation allows separate control of the two critical dimensions, enabling precise matching of the area ratio to operating conditions and preventing overexpansion while maintaining adaptability.
Solution Approach 2:
The nozzle transitions from a fixed geometry to a dynamically adjustable geometry through actuators that independently control the throat area and exit area. This dynamic capability allows the nozzle to adapt its area ratio in real-time to match varying operating conditions, optimizing expansion and eliminating efficiency losses from overexpansion.
2Stress or pressure
If the throat area is reduced to control pressure ratio, then the expansion ratio changes, but the exit area remains fixed causing mismatched expansion
Solution Approach 1:
The nozzle geometry is segmented into throat and exit sections with independent control mechanisms. When pressure ratio control is needed, only the throat area is adjusted while the exit area remains constant, or both are adjusted in coordinated fashion. This segmentation decouples the two area controls, allowing precise pressure ratio management without unintended changes to expansion ratio.
Solution Approach 2:
The nozzle operates by independently changing geometric parameters (throat area and exit area) to control flow characteristics. By selectively adjusting the throat area while holding exit area constant, or by coordinating both adjustments, the system can achieve desired pressure ratios with matched expansion ratios, preventing productivity loss from expansion mismatch.
3Device complexity
If a fixed geometry nozzle is used, then the structure is simple, but the ejector cannot adapt to varying operating conditions
Solution Approach 1:
The nozzle transitions from fixed geometry to dynamically adjustable geometry through the addition of actuators and control mechanisms. While this increases device complexity, it enables the ejector to adapt to varying operating conditions by adjusting throat and exit areas in response to changing system requirements, optimizing performance across different operating points.
Solution Approach 2:
The adjustable nozzle design provides multi-functionality, allowing the same nozzle structure to serve multiple operating conditions that would otherwise require different fixed-geometry nozzles. By incorporating independent throat and exit area control, the nozzle can be configured for various pressure ratios and expansion ratios, making the ejector system universally applicable across diverse operating scenarios.
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 approach enables partial compensation for inefficiencies caused by large area ratios, improving the overall efficiency of the ejector refrigeration system by adjusting the expansion ratio and maintaining optimal operating conditions.
Implementation Method 1
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 2
The pressure reduction caused to the primary flow by the motive nozzle helps draw the secondary flow into the outer member.
Implementation Method 3
The resulting combined flow decelerates and recovers pressure in the diffuser while remaining a mixture.
Data Source
AI summary
An ejector has a primary inlet, a secondary inlet, and an outlet. A primary flowpath extends from the primary inlet to the outlet and a secondary flowpath extends from the secondary inlet to the outlet, merging with the primary flowpath. A motive nozzle surrounds the primary flowpath upstream of a junction with the secondary flowpath. The motive nozzle has a throat and an exit. In one group of embodiments, an effective area of the exit is variable. In others, the needle may extend downstream from a flow control portion or may have an upstream convergent surface of a flow control portion.