Air Wall Slit Layout to Prevent Misting and Icing
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Solution Overview
Problem
Existing air wall devices for thermal separation between cold and warm spaces are ineffective in preventing misting and icing, and fail to maintain a high degree of sealing, especially when bridging significant temperature differences, due to low flow stiffness and inefficient heat resistance.
Innovation Solution
A device with a primary blower unit generating a high-speed, thin air stream through a narrow slit, combined with a suction unit and secondary air streams, maintains a high flow stiffness and effectively prevents heat transfer, using a cavity with a prismatic form and passive control valves to ensure constant airflow and prevent icing, while adjusting slit dimensions for optimal efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a wide blower slit is used to generate sufficient airflow, then the air wall can cover the passage opening, but the flow speed decreases and the air wall becomes easily disrupted by pressure differences
Solution Approach 1:
The patent changes the key parameter from slit width to slit height to achieve the desired airflow characteristics. By making the slit narrow in the horizontal direction (3-10mm) but extended in the vertical direction (30-100mm), the invention maintains high flow velocity while providing sufficient coverage area through the vertical extension rather than horizontal widening
2Strength
If the air stream is made thin and high-speed, then the flow stiffness increases and heat transfer is reduced, but the coverage area decreases
Solution Approach 1:
The patent resolves this contradiction by transitioning from a horizontal coverage approach to a vertical coverage approach. The narrow horizontal slit (3-10mm) produces a thin, high-speed stream with high stiffness, while the vertical extension (30-100mm) provides the necessary coverage area. This dimensional reorientation allows simultaneous achievement of flow stiffness and coverage
3Ease of operation
If the blower slit is positioned on one side of the passage opening, then vehicles can pass through without obstruction, but the air wall effectiveness is reduced
Solution Approach 1:
The patent positions the narrow vertical slit at the leading edge (suction side) of the passage opening, creating a preliminary high-velocity air barrier before vehicles enter. This preliminary action establishes a strong air wall that maintains sealing effectiveness while allowing vehicle passage, as the high velocity stream resists disruption by incoming vehicles
4Temperature
If a high degree of sealing is achieved to bridge large temperature differences, then thermal separation is improved, but misting and icing occur in the passage opening
Solution Approach 1:
The patent changes the airflow parameters by using a narrow vertical slit to generate high-velocity stream (15-30 m/s) with thin profile. This high velocity prevents stationary heat transfer situations that cause condensation, while the thin profile reduces the volume of cold air mixing with warm ambient air, thereby preventing misting and icing while maintaining thermal separation
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 device achieves a high degree of thermal separation with negligible heat transfer across a 25°C temperature difference, reducing misting and icing, and maintaining air curtain effectiveness with lower perceived airflow and improved energy efficiency.
Implementation Method 1
a primary blower unit positioned on one side of the passage opening and having primary blower fan means and a primary blower slit which connects thereto
Implementation Method 2
a stationary heat-transfer situation cannot occur in the air wall, as is the case at relatively low flow speeds. Effective mixing and heat diffusion between the warm and cold sides adjacently of the air wall is in fact effectively precluded
Implementation Method 3
This document describes a technique which cannot prevent the formation of mist in the passage opening and icing on, among other parts, the floor of the cold store
Data Source
Figure 1
Figure 2A-1~2A-2
Figure 2B
AI summary
A device for generating an air wall comprises a primary blower slit for generating a flat primary air stream in a passage opening mutually separating two spaces with different temperatures. Two adjacent air streams with the same direction and speed are added to the primary air stream. The primary air stream has a temperature between those of the secondary air streams. The absolute humidity of the air of the primary air stream is at least equal to that of the cold secondary air stream and lower than that of the warm secondary air stream. The air speed of the primary air stream amounts to at least 15 m/s. The width of the primary blower slit lies in the range of 15-40 mm. The length of the primary blower slit in the direction of the air stream lies roughly in the range of 5-40 cm, preferably 10-30 cm. No mixing occurs hereby occurs between the primary air stream Sp and the second secondary air stream Ss2 on the side of the warm space, whereby condensation (misting and vaporization) and/or sublimation (icing) is prevented.