Cascaded Evaporator Ejector Cycle Without a Booster Compressor
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Solution Overview
Problem
Ejector refrigeration cycles face limitations in operational flexibility and efficiency due to high-side pressure control issues, leading to reduced coefficient of performance and increased power consumption, especially when trying to achieve multiple evaporation pressures without the need for additional compressors or multiple ejectors.
Innovation Solution
Incorporating a pump downstream of the condensing heat exchanger to create the necessary pressure differential between evaporative heat exchangers, eliminating the need for a booster compressor and allowing a fixed-geometry ejector to operate efficiently across a range of conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If a booster compressor is added to achieve two evaporation pressures, then the pressure differential between evaporators is achieved, but the overall power consumption of the cycle increases
Solution Approach 1:
The invention extracts and eliminates the booster compressor from the refrigeration cycle by using the ejector's suction nozzle to directly connect the low-temperature evaporator to the high-side of the cycle. The ejector uses the pressure differential created by the condensing heat exchanger and expansion valve to achieve the necessary pressure differential between evaporators without requiring additional compression power.
Solution Approach 2:
The ejector acts as an intermediary device that replaces the booster compressor. It uses the motive flow from the condensing heat exchanger to create suction and achieve the pressure differential needed for cascaded evaporation, thereby eliminating the need for mechanical compression while maintaining the pressure differential between evaporators.
2Adaptability or versatility
If multiple ejectors or an adjustable ejector are used to accommodate pressure changes, then the ejector can operate under varying conditions, but the device complexity increases
Solution Approach 1:
The invention makes the refrigeration cycle dynamic by allowing the ejector to operate across a range of conditions through the natural pressure differential created by the condensing heat exchanger and expansion valve. The system adapts to varying loads and temperatures without requiring multiple ejectors or adjustable mechanisms, as the pressure differential automatically adjusts with operating conditions.
Solution Approach 2:
The single ejector is designed to perform multiple functions: it creates the pressure differential for cascaded evaporation, mixes the refrigerant streams, and enables the booster-free operation. This multi-functional design eliminates the need for multiple specialized components while maintaining operational flexibility across varying conditions.
3Stress or pressure
If the outlet flow from the first evaporator is expanded to the lower evaporating pressure, then the second evaporation stage is achieved, but the efficiency is reduced compared to using a compressor
Solution Approach 1:
The invention utilizes phase transitions in the ejector where the high-pressure liquid refrigerant from the condensing heat exchanger partially vaporizes to create the suction effect. This phase change enables the ejector to pull vapor from the low-temperature evaporator and mix it with the liquid stream, achieving the pressure differential and cascaded evaporation effect without the energy loss associated with expansion valves or lack of compression.
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 operational flexibility and energy efficiency by maintaining optimal performance and reducing power consumption, while enabling the ejector to operate effectively without the need for additional compressors or multiple ejectors, thus improving the overall system efficiency.
Implementation Method 1
A pressure differential between the motive flow in line 102 upstream of the ejector 104 and the suction flow in line 118 is what allows the ejector 104 to operate
Implementation Method 2
Through the entrainment of suction flow in line 118 by the acceleration of the motive flow in line 102, the ejector 104 discharges these two flows at a pressure higher than the pressure in the heat exchanger 116
Implementation Method 3
Incorporating a pump downstream of the condensing heat exchanger to create the necessary pressure differential between evaporative heat exchangers
Implementation Method 4
Liquid from the flash tank 108 is evaporated in the heat exchanger 116 used to cool an external stream
Implementation Method 5
Vaporized refrigerant from a first evaporative heat exchanger 116
Implementation Method 6
Vapor from line 110 from the flash tank 108 is recompressed in the compressor 112 and subsequently condensed in a condensing heat exchanger 114 with heat rejection to an external heat sink
Data Source
AI summary
Systems and methods for implementing ejector refrigeration cycles with cascaded evaporation stages that utilize a pump to optimize operation of the ejector and eliminate the need for a compressor between the evaporation stages.