Ejector refrigeration circuit and method of operating the same
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Solution Overview
Problem
In refrigeration circuits using ejectors, maintaining a sufficient pressure drop to ensure efficient refrigerant flow through the evaporator is challenging, especially in subcritical conditions, as conventional systems require pumps or increased vapor quality, which can reduce overall efficiency.
Innovation Solution
Incorporating a vapor quality sensor at the outlet of the heat rejection heat exchanger to control the ejector's operation, adjusting its parameters to maintain the required pressure lift without a pump, using variable geometry ejectors and a flash tank to optimize vapor and liquid separation, and employing multiple sensors for redundancy and accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a pump is added to maintain pressure in subcritical conditions, then the pressure stability is improved, but the device complexity increases
Solution Approach 1:
The patent removes the pump from the system by extracting the problematic component that caused complexity. Instead of adding a pump to maintain pressure, the invention uses a flash tank to separate vapor from liquid refrigerant, allowing the system to operate in subcritical conditions without additional pressure-maintaining equipment.
Solution Approach 2:
The invention changes the operating parameters by allowing the refrigerant to undergo phase change in the flash tank. By controlling the vapor quality and using the phase separation between liquid and vapor phases, the system maintains pressure stability through natural phase equilibrium rather than mechanical pumping.
2Power
If vapor quality is increased to improve ejector pressure lift, then the ejector efficiency is improved, but the compressor workload increases
Solution Approach 1:
The flash tank controls the vapor quality parameter of the refrigerant entering the ejector. By adjusting the degree of flashing (partial vaporization) in the flash tank, the system optimizes the vapor quality to provide sufficient pressure lift in the ejector while preventing excessive vapor that would increase compressor workload.
Solution Approach 2:
The system uses sensors to monitor vapor quality and provides feedback control to the flash tank operation. This feedback mechanism ensures that the vapor quality remains within the optimal range for ejector performance without over-vaporizing the refrigerant, thereby balancing ejector efficiency with compressor workload.
3Reliability
If multiple sensors are added for redundancy and accuracy, then the measurement reliability is improved, but the device complexity increases
Solution Approach 1:
The patent places sensors at specific critical locations in the system, particularly at the outlet of the flash tank where vapor quality is most important for ejector operation. Rather than distributing sensors throughout the entire system, the invention focuses measurement capabilities on the most critical parameters at the most critical locations.
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 ensures consistent refrigerant flow through the evaporator without additional pumps, simplifying the system, reducing costs and maintenance, and improving efficiency by optimizing vapor quality and compressor workload.
Implementation Method 1
the pressure difference between the high pressure inlet and the outlet of the ejector must be sufficient to draw the refrigerant fluid through the evaporator
Implementation Method 2
When an ejector is used as part of a refrigeration circuit, the cooled refrigerant from the condenser can enter the ejector at the high pressure inlet and is expanded to a lower pressure at the outlet of the ejector
Implementation Method 3
a heat rejection heat exchanger/condenser for condensing the refrigerant to a liquid
Implementation Method 4
heat absorption heat exchanger
Data Source
Figure 1
AI summary
An ejector refrigeration circuit 1 comprising: a two-phase circuit 2 comprising: a heat rejection heat exchanger 12 comprising an inlet 12a and an outlet 12b; and an ejector 14 comprising a high pressure inlet 14a, a low pressure inlet 14b and an outlet 14c; wherein the ejector high pressure inlet 14a is coupled to the heat rejection heat exchanger outlet 12b; and an evaporator 18 comprising an inlet 18a and an outlet 18b; wherein the outlet 18b of the evaporator 18 is coupled to the low pressure inlet 14b of the ejector 14; and wherein the ejector refrigeration circuit 1 further comprises a vapour quality sensor 20 positioned at the outlet 12b of the heat rejection heat exchanger 12.