Two-Phase Flow Cleaning for Narrow Medical Channels
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Solution Overview
Problem
Current methods for cleaning the internal surfaces of narrow diameter channels, such as endoscopes and medical devices, face limitations in achieving high cleaning levels due to the limited viscous shear forces generated, especially when dealing with long narrow tubes that cannot tolerate high pressures.
Innovation Solution
A two-phase cleaning method involving the creation of surface flow entities with three-phase contact lines and associated menisci, which detach contaminants by sliding along the channel surface, using specific flow regimes like Rivulet Droplet Flow (RDF), Discontinuous Plug Flow (DPF), and Discontinuous Plug Droplet Flow (DPDF), without predispersing the cleaning medium as droplets and minimizing annular films and foam.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional liquid flow cleaning methods are used, then the cleaning process is simple and automated, but the viscous shear forces generated are insufficient to remove strongly adherent contaminants
Solution Approach 1:
The patent changes the flow regime parameters from conventional bulk liquid flow to two-phase flow with specific gas and liquid flow rates. By adjusting the gas flow rate to create surface flow entities and controlling the liquid flow rate to form rivulets or plugs, the system generates enhanced viscous shear forces at the channel surface while maintaining ease of automated operation
Solution Approach 2:
The patent applies pneumatic principles by introducing a gas phase that flows through the channel to create surface flow entities. The gas flow generates shear forces and entrains liquid to form rivulets, plugs, or droplets that slide along the channel surface, significantly enhancing cleaning effectiveness compared to liquid flow alone
2Manufacturing precision
If two-phase flow with entrained droplets is used to improve cleaning, then contaminant removal increases, but the pressure required exceeds the maximum ratings of sensitive medical devices
Solution Approach 1:
The patent applies local quality by creating surface flow entities that concentrate cleaning action at the channel surface rather than using bulk flow throughout the entire channel volume. The gas flow and liquid rivulets/plugs are configured to interact primarily at the wall surface where contaminants are located, generating high cleaning effectiveness with low overall pressure requirements
Solution Approach 2:
The patent segments the liquid phase into discrete rivulets, plugs, or droplets that flow along the channel surface rather than using continuous bulk liquid flow. This segmentation allows the cleaning action to be distributed along the channel length while maintaining low pressure, as each segment acts independently to remove contaminants
3Area of stationary object
If liquid cleaning medium is predispersed as droplets in gas, then cleaning coverage increases, but the method becomes less effective for creating surface flow entities with three-phase contact lines
Solution Approach 1:
The patent inverts the conventional approach by not predispersing liquid as droplets in gas before entering the channel. Instead, the liquid is introduced separately and allowed to form surface flow entities (rivulets, plugs) that naturally interact with the gas phase within the channel, creating effective three-phase contact lines at the surface
4Manufacturing precision
If high gas flow rates are used to generate surface flow entities, then cleaning effectiveness improves, but excessive foam and annular films are formed
Solution Approach 1:
The patent employs periodic or pulsed flow regimes where gas and liquid are introduced in alternating or controlled sequences. This periodic action allows surface flow entities to form and act on contaminants without continuous foam generation, as the flow conditions are not constantly maintained at levels that would produce excessive foam and annular films
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 method achieves high levels of cleaning at pressures below 35 psi, suitable for sensitive medical devices, by effectively detaching contaminants through hydrodynamic and capillary forces, ensuring thorough coverage of the channel surface without forming wetting films or excessive foam.
Implementation Method 1
surface flow entities having three-phase contact lines and associated menisci, which detach contaminants with which they come in contact from the internal surface of the channel
Implementation Method 2
achieves high levels of cleaning at pressures below 35 psi, suitable for sensitive medical devices, by effectively detaching contaminants through hydrodynamic and capillary forces
Implementation Method 3
A two-phase cleaning method involving the creation of surface flow entities with three-phase contact lines and associated menisci, which detach contaminants by sliding along the channel surface, using specific flow regimes like Rivulet Droplet Flow (RDF), Discontinuous Plug Flow (DPF), and Discontinuous Plug Droplet Flow (DPDF)
Data Source
AI summary
A method for cleaning an internal surface of a narrow diameter channel includes steps of: flowing a liquid cleaning medium and a gas through the narrow diameter channel under a flow regime that creates surface flow entities in contact with and sliding along the internal surface of the narrow diameter channel, the surface flow entities having three-phase contact lines and associated menisci, the surface flow entities detaching contaminants with which they come in contact from the internal surface of the narrow diameter internal surface of the narrow diameter channel; and rinsing the internal surface of the narrow diameter channel to remove residual liquid cleaning medium and detached contaminants from the channel.