Cross-flow Tray Segmentation for Liquid Distribution
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Solution Overview
Problem
High-capacity cross-flow trays face issues with uniform liquid distribution and recirculation of liquid, leading to reduced separation efficiency and undesirable entrainment at low liquid flow rates.
Innovation Solution
The design incorporates a weir system and splash walls to direct liquid flow uniformly across the tray deck, with discharge openings positioned predominantly downstream to prevent recirculation, ensuring liquid is carried over the weir and distributed sequentially to cans, promoting plug flow and reducing entrainment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If liquid is uniformly distributed to each can, then high flow capacity is achieved, but at low liquid flow rates the liquid becomes readily entrained in the vapor stream forming spray which diminishes separation efficiency
Solution Approach 1:
The tray deck is divided into multiple zones with sequential liquid delivery paths, and cans are grouped within zones. Liquid is segmented to be delivered to specific groups of cans in sequence rather than uniformly to all cans simultaneously, allowing control over liquid distribution patterns to prevent entrainment while maintaining flow capacity
Solution Approach 2:
Different regions of the tray deck are assigned different functions: inlet areas for liquid introduction, active areas with cans for vapor-liquid interaction, and outlet areas for liquid removal. The liquid distribution is locally optimized in each zone to achieve appropriate liquid loading on cans without excessive uniform distribution that causes entrainment
2Device complexity
If liquid flows directly from inlet to downcomer, then simple flow path is achieved, but liquid tends to be recirculated to each can rather than flowing in desired plug flow pattern across the tray
Solution Approach 1:
The tray deck is segmented into multiple zones separated by outlet areas and downcomers. Liquid flow is divided into sequential segments that progress through each zone in order, preventing direct short-circuiting from inlet to downcomer and ensuring plug flow pattern through proper zonal progression
Solution Approach 2:
Outlet areas and intermediate downcomers act as mediators between inlet areas and final outlet regions. These intermediary structures control liquid progression through the tray, forcing liquid to flow sequentially through each zone rather than allowing direct recirculation paths
3Ease of operation
If discharge openings are positioned on all sides of cans, then liquid can exit freely, but liquid exits may be recirculated back to the same cans reducing efficiency
Solution Approach 1:
Discharge openings in the can walls are positioned asymmetrically, predominantly on the downstream side of each can rather than uniformly distributed around the circumference. This asymmetric positioning directs liquid discharge away from upstream cans, preventing recirculation while maintaining adequate liquid exit capability
Solution Approach 2:
Instead of positioning discharge openings to maximize liquid exit freedom in all directions, the design inverts the approach by strategically positioning openings predominantly downstream to prioritize prevention of recirculation, accepting slightly restricted exit freedom in exchange for improved separation efficiency
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 mass transfer and heat exchange efficiency by ensuring uniform liquid distribution and minimizing recirculation, thereby improving separation efficiency across the tray deck.
Implementation Method 1
A weir is positioned between a first group of cans in a first zone on the tray deck and a second group of cans in a second zone on the tray deck to cause liquid to be delivered to the cans in the first group of cans before being delivered to the second group of cans
Implementation Method 2
The discharge openings are also positioned predominantly or entirely on a downstream side of the cans so that liquid exiting through the discharge openings is carried over the weir and onto the tray deck in the second zone
Implementation Method 3
A plurality of vapor openings positioned in the tray deck allows the upward passage of vapor through the tray deck
Implementation Method 4
The trays include a deck surface in which a plurality of openings are provided to allow an ascending fluid stream, typically a vapor stream, to pass through the tray deck and interact with a liquid stream flowing horizontally across the deck surface. The vapor-liquid interaction that occurs on this active area of the deck surface forms a froth that facilitates the desired mass transfer and/or heat exchange between the liquid and vapor streams
Implementation Method 5
A swirling motion is imparted to vapor ascending within the can using swirl vanes positioned within the cans
Data Source
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AI summary
A cross-flow tray is provided with a tray deck and groupings of cans separated by weirs. The cans have walls that surround vapor openings in the tray deck. Openings are provided in the walls to allow liquid to enter the cans from the tray deck. Additional openings are provided in the walls to allow liquid to exit the cans. Swirlers positioned within the cans induce a centrifugal swirling motion to the vapor and liquid to facilitate mass transfer and/or heat exchange between the vapor and liquid within the cans.