Thin-Profile Air Conditioner Layout to Prevent Outlet Backflow

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Solution Overview

Problem

Air-conditioning devices with a thin shape, where the depth dimension is greater than the height dimension, face issues with air flow instability and backflow due to close proximity of the heat exchanger and fan, leading to increased air flow resistance and condensation risks, especially during cooling.

Innovation Solution

The air-conditioning device is designed with a cuboid-shaped main body where the inlet port is on the upper surface and the outlet port is on the lower front surface, featuring a cross-flow fan and a heat exchanger with specific inclination angles and dimensions to minimize backflow, including a ratio of main body height to fan outer diameter between 2.2 and 2.7, and a fan inlet angle between 150° and 180°, which stabilizes air flow and reduces motor power consumption.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Area of stationary object

If the main body is formed in a thin shape with depth dimension greater than height dimension, then the installation surface area on wall surface is suppressed and no sense of incongruity is produced in indoor interior, but the heat exchanger and fan are in close proximity on the fan inlet side causing air flow resistance to increase and back flow to occur

Engineering Contradiction:
Improveinstallation surface areaVSAvoidair flow stability
Core Design Contradiction:
Area of stationary objectVSReliability

Solution Approach 1:

The patent reorients the thin dimension from vertical (height) to horizontal (depth) direction. The main body has depth dimension D greater than height dimension H, allowing the device to be thin in the wall-mounted direction while providing sufficient internal space in the depth direction to separate the heat exchanger and fan, thus resolving the contradiction between compact installation area and stable air flow.

Inventive Principle:
Principle #17Another dimension (Dimensionality change)

2Area of stationary object

If the main body is formed in a thin shape with depth dimension greater than height dimension, then the installation surface area on wall surface is suppressed, but the distance between main body outlet port and outer periphery of fan is small on the fan outlet side causing fan blow output flow to become instable and back flow to occur

Engineering Contradiction:
Improveinstallation surface areaVSAvoidfan blow output flow
Core Design Contradiction:
Area of stationary objectVSProductivity

Solution Approach 1:

By making the depth dimension D greater than height dimension H, the patent creates sufficient space in the depth direction to position the fan at an optimal distance from the outlet port. This dimensional reorientation allows the fan outlet to be positioned such that the distance to the outlet port is adequate, ensuring stable blow output flow while maintaining a thin profile for wall installation.

Inventive Principle:
Principle #17Another dimension (Dimensionality change)

3Reliability

If the fan inlet region is small due to close proximity of heat exchanger and fan, then the air is not readily taken in in a uniform manner, but increasing the distance requires larger main body dimensions

Engineering Contradiction:
Improveair intake uniformityVSAvoidmain body volume
Core Design Contradiction:
ReliabilityVSVolume of moving object

Solution Approach 1:

The patent utilizes the depth dimension D (greater than height H) to create sufficient spacing between the heat exchanger and fan in the depth direction. This allows the fan inlet region to be adequately sized for uniform air intake while keeping the height dimension small for thin-profile installation, thus resolving the contradiction between air intake uniformity and main body volume.

Inventive Principle:
Principle #17Another dimension (Dimensionality change)

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 prevents backflow at the outlet port, ensures stable air flow, and enhances energy efficiency while maintaining a slim profile, reducing the risk of condensation on the fan and improving overall performance and installation flexibility.

Implementation Method 1

a heat exchanger (7) which generates conditioned air by transmitting the heating energy or cooling energy of a refrigerant to the air

Methodology Applied
Scientific EffectHeat exchange: Heat Exchanger

Implementation Method 2

a cross-flow fan (8) which draws in air taken in from the inlet port (2b) and blows out the air towards the outlet port (3)

Methodology Applied
Scientific EffectFluid flow: Fan

Data Source

PatentEP3412979B1Air-conditioning device
Publication Date: 2023.09.20 MITSUBISHI ELECTRIC CORP
  • EP3412979B1 patent drawingFigure 1
  • EP3412979B1 patent drawingFigure 2~3
  • EP3412979B1 patent drawingFigure 4~6

AI summary

In an air-conditioning device 100, back flow is less likely to occur at an outlet port in relation to an inlet resistance, and the air-conditioning device 100 includes: a main body 1 having an inlet port 2b and an outlet port 3; a cross-flow fan 8 provided inside the main body; and a heat exchanger 7 provided inside the main body 1, wherein the main body 1 includes at least a front surface 1a, a rear surface 1c, an upper surface 1b and a lower surface 1d, the inlet port 2b is formed in the upper surface 1b, a ratio H/Df between the main body height dimension H and the fan outer diameter Df is 2.2 to 2.7, and an angle of inclination β between a rear part of an front upward inclination section 7a' of the heat exchanger 7 and a vertical direction is 30° to 45°.