Ventilation Module Stabilizing Film Heating via Coanda Guide Plate
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Solution Overview
Problem
Existing ventilation modules for foil bar systems suffer from unstable air flow conditions, leading to uneven heat transfer and mechanical property inconsistencies in plastic film railways.
Innovation Solution
The ventilation module design includes a foil catchment area, a foil exit area, and a first inflow nozzle arrangement with a slit nozzle and a back suction system with two suction channels. The intake areas are strategically placed to stabilize the air flow, ensuring a consistent heat transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If free jets are discharged directly onto the plastic film web, then heat transfer intensity increases, but flow stability deteriorates causing chaotic oscillation and uneven heating
Solution Approach 1:
A Coanda guide plate is introduced as an intermediary element between the free jet discharge and the plastic film web. The guide plate stabilizes the free jet flow by utilizing the Coanda effect, causing the jet to attach to and follow the plate surface, thereby eliminating chaotic oscillation while maintaining directed heat transfer to the film web.
Solution Approach 2:
The design changes the flow parameters by controlling the jet velocity and attachment angle to the guide plate. By optimizing these parameters, the free jet transitions from an unstable, oscillating state to a stable, attached flow that consistently follows the guide plate contour and delivers uniform heat transfer to the plastic film web.
2Temperature
If blow-out nozzles are positioned close to the plastic film web, then heat transfer efficiency improves, but transport system complexity increases due to safety margin requirements
Solution Approach 1:
The Coanda guide plate serves as a mediator that enables the blow-out nozzle to be positioned at an optimal distance from the plastic film web. The guide plate extends the thermal influence zone toward the film, allowing efficient heat transfer while maintaining sufficient clearance for the transport system, thereby reducing mechanical complexity.
3Temperature
If impact jets are used for heating, then heat transfer rate increases, but uniformity of heating deteriorates due to jet oscillation and tilting
Solution Approach 1:
The Coanda guide plate acts as a flow stabilizing intermediary that transforms the unstable impact jet into a controlled, attached flow. The jet follows the guide plate surface, ensuring consistent contact with the plastic film web across the width, thereby achieving uniform heating while maintaining high heat transfer rates.
Solution Approach 2:
The guide plate is designed with specific local geometries and angles optimized for different sections of the nozzle arrangement. This local optimization ensures that each section of the plastic film web receives uniformly distributed heat transfer, addressing regional variations in heating quality.
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 achieves a more stable and uniform heat transfer coefficient, reducing temperature fluctuations and enhancing the evenness of mechanical properties in the plastic film railway.
Implementation Method 1
at least one first blow-out nozzle arrangement (8) which is designed to blow air for heating or cooling in the direction of the plastic film web (2)
Implementation Method 2
at least one first suction back system (9) with at least two suction channels (10a, 10b) which is designed to suck air through the suction areas (11a, 11b) and the suction channels (10a, 10b)
Data Source
Figure 1
Figure 2A
Figure 2B
AI summary
The invention relates to a ventilation module (3) for a film stretching system (1) comprising at least one first outlet nozzle arrangement (8) having an outlet nozzle (8a), wherein the at least one outlet nozzle (8a) extends with its longitudinal direction (5) transverse or perpendicular to the withdrawal direction (4) of a plastic film web (2) and is oriented in parallel to the transport plane (7). A first return system (9) is provided with at least two extraction channels (10a, 10b), each having an extraction region (11a, 11b). The at least two extraction regions (11a, 11b) are spaced apart from one another in the withdrawal direction (4) and oriented in parallel to the transport plane (7). The at least one outlet nozzle (8a) of the at least one first outlet nozzle arrangement (8) is arranged between the first and the second extraction region (11a, 11b). The at least two extraction regions (11a, 11b) are arranged exclusively before and/or after the at least one first outlet nozzle arrangement (8) in the withdrawal direction (4) of the plastic film web (2).