Dual-Ejector Heat Pump Flow Switching for Cooling and Heating
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Solution Overview
Problem
Ejector refrigeration systems face limitations in efficiently managing refrigerant flow and pressure ratios, leading to suboptimal refrigeration effects and evaporator performance, particularly in switching between cooling and heating modes.
Innovation Solution
The system incorporates two ejectors optimized for respective modes, with controllable valves and actuators to manage refrigerant flowpaths, allowing for efficient operation in both cooling and heating modes by reversing the roles of heat exchangers and using asymmetric ejector designs to tailor performance for specific conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a single ejector design is used for both cooling and heating modes, then device complexity is reduced, but refrigeration efficiency and evaporator performance deteriorate due to inability to optimize for specific conditions
Solution Approach 1:
The single ejector is divided into two separate ejectors, each optimized for specific operational modes (cooling and heating). This segmentation allows each ejector to have tailored nozzle geometries and flow characteristics that maximize efficiency for its designated mode, resolving the contradiction between adaptability and complexity by using multiple specialized components rather than one general-purpose component
Solution Approach 2:
The system dynamically switches between different ejector configurations based on operational mode requirements. Through controllable valves and actuators, the system can reverse refrigerant flowpaths and activate the appropriate ejector for current conditions, enabling adaptability while maintaining optimized performance for each mode
2Productivity
If refrigerant flow and pressure ratios are not optimized, then system simplicity is maintained, but refrigeration efficiency and evaporator performance deteriorate
Solution Approach 1:
Different portions of the refrigerant circuit are optimized for specific functions: the first ejector is optimized for cooling mode with its nozzle geometry and flow characteristics, while the second ejector is optimized for heating mode. This local optimization of flow management in different system segments achieves high refrigeration efficiency without requiring complex centralized control
Solution Approach 2:
The system changes operational parameters (flow direction, pressure ratios, temperature differentials) based on mode requirements. By using controllable valves to reverse refrigerant flowpaths and actuators to adjust ejector operations, the system optimizes parameters for each mode, achieving high productivity while maintaining manageable complexity through parameter control rather than structural complexity
3Reliability
If heat exchanger roles are not reversed between modes, then system simplicity is maintained, but heat transfer performance deteriorates in non-optimal modes
Solution Approach 1:
The heat exchangers dynamically reverse their operational roles between cooling and heating modes through controllable valves that redirect refrigerant flow. The first heat exchanger serves as the primary heat exchanger in cooling mode and as the secondary heat exchanger in heating mode, and vice versa for the second heat exchanger. This dynamic role reversal ensures optimal heat transfer performance in both modes while using the same physical components, achieving reliability without adding separate heat exchangers for each mode
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 refrigeration efficiency by optimizing refrigerant flow and pressure ratios, reducing power consumption, and allowing for compact evaporator design, while maintaining high heat transfer performance across modes.
Implementation Method 1
The pressure reduction caused to the primary flow by the motive nozzle helps draw the secondary flow 112 into the outer member.
Implementation Method 2
The outer member also has a divergent section or diffuser 118 downstream of the elongate throat or mixing section 116. The resulting combined flow 120 is a liquid/vapor mixture and decelerates and recovers pressure in the diffuser 118
Implementation Method 3
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).
Implementation Method 4
In the normal cooling mode, refrigerant along the leg 80 absorbs heat from water along the leg 82.
Data Source
AI summary
A vapor compression system (200; 400; 600; 700; 800; 900; 1000) comprises a plurality of valves (260, 262, 264; 260) controllable to define a first mode flowpath and a second mode flowpath. The first mode flowpath is sequentially through: a compressor (22); a first heat exchanger (30); a first nozzle (228; 624); and a separator (48), and then branching into: a first branch returning to the compressor; and a second branch passing through an expansion device (70) and a second heat exchanger (64) to the rejoin the flowpath between the first heat exchanger and the separator. The second mode flowpath is sequentially through: the compressor; the second heat exchanger; a second nozzle (248; 625); and the separator, and then branching into: a first branch returning to the compressor; and a second branch passing through the expansion device and first heat exchanger to the rejoin the flowpath between the first heat exchanger and the separator.