Process Challenge Device Flow Shaping for Narrow Channel Simulation
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Solution Overview
Problem
Conventional Process Challenge Devices (PCDs) used for evaluating decontamination processes in medical and laboratory instruments with narrow channels face challenges in simulating realistic cleaning conditions, leading to inaccurate results due to unrealistic fluid flow parameters and potential incorrect tag orientation, which complicates the evaluation of biofilm growth and contamination removal.
Innovation Solution
A PCD design featuring a hollow capsule with a flow shaping part and a tag holding part that ensures correct tag orientation and maintains consistent fluid flow velocity and direction, simulating the internal geometry of narrow channels, thereby preventing turbulence and allowing for non-destructive evaluation of contamination formation and removal processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional PCDs use rectangular tags placed inside cylindrical capsules for cleaning evaluation, then the device structure is simple, but the fluid flow parameters become unrealistic and turbulence occurs due to sudden geometry changes
Solution Approach 1:
The capsule is divided into distinct functional segments: a flow shaping part with gradual geometry transitions and a tag holding part with specific constraints. This segmentation allows each part to optimize its function - the flow shaping part maintains laminar flow by avoiding sudden changes, while the tag holding part ensures proper tag positioning and orientation.
Solution Approach 2:
Different parts of the capsule have different geometric characteristics optimized for their specific functions. The flow shaping part features gradual curvature changes and optimized cross-sections to maintain laminar flow, while the tag holding part has specific constraints to ensure correct tag orientation. This local optimization of geometric quality resolves the contradiction between simplicity and flow simulation accuracy.
2Productivity
If tags are positioned in the middle of the capsule where flow velocity is highest, then the tag is exposed to maximum fluid flow, but the flow is split into two streams creating unrealistic cleaning conditions
Solution Approach 1:
The tag holding part creates an asymmetric flow configuration where the tag is positioned to create a single stream flowing over one side of the tag, rather than splitting the flow into two streams. This asymmetric positioning mimics the unidirectional flow pattern found in narrow channels, ensuring that the cleaning conditions simulated are realistic while still providing adequate contamination removal evaluation.
3Volume of moving object
If the capsule creates a large increase in internal diameter when fluid enters, then the capsule can accommodate the tag, but unwanted turbulence results from the sudden geometry change
Solution Approach 1:
The flow shaping part employs smooth curved transitions and gradual geometry changes rather than sharp angles or sudden expansions. The capsule cross-section gradually increases from the inlet to the tag holding part, maintaining laminar flow conditions. This curved, gradual transition geometry allows the capsule to accommodate the tag while preventing turbulence, resolving the contradiction between volume accommodation and flow stability.
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
The PCD design provides a more realistic simulation of fluid flow within narrow channels, ensuring accurate evaluation of contamination removal and formation processes, reducing the risk of healthcare-acquired infections and improving cleaning performance by maintaining consistent fluid velocity and orientation, thus facilitating standardised and repeatable results without damaging the equipment.
Implementation Method 1
The internal flow parameters inside the capsule are often very different from the narrow tubes that they are designed to scrutinise. They are characterised by much lower fluid velocity inside the capsule and unwanted turbulence resulting from significantly changing the internal geometry
Data Source
Figure 1~4
AI summary
A process challenge device and method for evaluation of contamination forming and removal processes inside of narrow and hollow channels comprising sample, capsule having an inlet connector, a flow shaping element and an internal cavity, a lock – or end cap – for each capsule securing the sample inside the cavity. The tag being located in the capsule against one of the walls of the internal cavity that is shaped not to change the parameters of the fluid flow while it flows into said cavity and over the face of the sample simulating the flow through an equivalent narrow channel. Methods characterised by said process challenge device being loaded with a matching sample containing contamination for evaluation of effectiveness of a cleaning processes or blank sample for evaluation of contamination formation processes on said sample when exposed to cleaning of contaminated fluid flowing through the inside of the capsule's cavity.