Flash Tank Spiral Chamber Layout for Transcritical Phase Separation
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Solution Overview
Problem
Refrigerant vapor compression systems operating in transcritical cycles face challenges in efficiently separating refrigerant flow into liquid and vapor portions due to increased pressure differences and vibrations, which affect system capacity and efficiency, especially in transport refrigeration applications where size constraints and varying ambient conditions are prevalent.
Innovation Solution
A transport refrigeration refrigerant vapor compression system with a flash tank having a unique internal structure, including an upper, middle, and lower chamber, and a helical spiral member, which enhances phase separation by establishing specific fluid passages and equalization holes to manage refrigerant flow and reduce phase mixing caused by vibrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional flash tank is used in transcritical refrigerant cycle, then the system can operate in transcritical mode, but the separation of refrigerant phases is inefficient due to increased pressure differences and vibrations
Solution Approach 1:
The flash tank interior is divided into three chambers (upper, middle, lower) with specific fluid passages between them. This segmentation allows differentiated treatment of vapor and liquid phases, with the upper chamber collecting vapor, the lower chamber collecting liquid, and the middle chamber serving as a transition zone. The segmentation improves phase separation efficiency by providing dedicated spaces for each phase while maintaining the ability to handle transcritical pressure differences.
Solution Approach 2:
A helical spiral member is introduced into the flash tank, creating a three-dimensional spiral flow path for refrigerant. This dimensional addition transforms simple vertical flow into a rotational spiral pattern, enhancing phase separation through centrifugal effects and extended flow path length. The helical structure increases the residence time and separation distance for vapor-liquid separation, directly addressing the inefficiency caused by vibrations and pressure differences.
2Volume of moving object
If the flash tank size is reduced to meet transport refrigeration space constraints, then the system fits within size limitations, but phase separation performance deteriorates
Solution Approach 1:
The helical spiral member creates a three-dimensional flow path within the limited flash tank volume, effectively increasing the separation path length and residence time without increasing the external dimensions of the tank. This allows efficient phase separation to occur within a compact volume suitable for transport refrigeration applications.
Solution Approach 2:
The middle chamber acts as an intermediary zone between the upper and lower chambers, providing a transition area where vapor-liquid separation can occur progressively. This intermediary space allows the system to achieve effective separation with a smaller overall tank volume by distributing the separation process across multiple zones rather than requiring a single large chamber.
3Productivity
If the refrigerant pressure difference between gas cooler and evaporator is increased in transcritical mode, then the system can operate efficiently in transcritical cycle, but the phase separation becomes more difficult
Solution Approach 1:
The three-chamber configuration with controlled fluid passages allows the system to handle large pressure differences by providing gradual pressure equalization paths. The middle chamber serves as a pressure transition zone, and the specific fluid passages are designed to manage the pressure differential between upper and lower chambers, enabling effective separation even when the overall pressure difference between gas cooler and evaporator is high.
Solution Approach 2:
The middle chamber acts as a pressure intermediary, allowing gradual pressure equalization between the high-pressure upper chamber and low-pressure lower chamber. This intermediary zone prevents sudden pressure changes that would disrupt phase separation, enabling the system to maintain efficient separation performance despite the large overall pressure differential required for transcritical operation.
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 improves the separation of refrigerant phases, increases system capacity, and optimizes energy efficiency by maximizing enthalpy differences across the evaporator, while minimizing the size of system components and maintaining performance under varying conditions.
Implementation Method 1
a helical spiral member extending about said vertical support tube and defining a continuous spiral fluid flow passage
Implementation Method 2
said interior volume divided into an upper chamber, a lower chamber and a middle chamber
Implementation Method 3
the refrigerant separates into a liquid refrigerant component and a vapor refrigerant component
Implementation Method 4
an upper equalization hole passing through said support tube and a lower equalization hole passing through said support tube
Data Source
Figure 1
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Figure 3
AI summary
A refrigerant vapor compression system includes a flash tank disposed in the refrigerant circuit intermediate a refrigerant heat rejection heat exchanger and a refrigerant heat absorption heat exchanger. The flash tank has a shell defining an interior volume having an upper chamber, a lower chamber and a middle chamber. A first fluid passage establishes fluid communication between the middle chamber and the upper chamber and a second fluid passage establishing fluid communication between the middle chamber and the lower chamber. An inlet port opens to the middle chamber. A first outlet port opens to the upper chamber and a second outlet port opens to the lower chamber.