Indoor Unit Air Guide Design to Reduce Heat Exchanger Pressure Loss

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Solution Overview

Problem

In existing indoor air-conditioning units, the non-uniform air velocity distribution across the heat exchanger leads to increased pressure loss and noise, and the enlargement of diffusers to address this issue results in insufficient improvement due to pressure losses and turbulence, often causing vortices.

Innovation Solution

The design includes an air-sending portion with a rectangular air outlet and a guide portion with open side regions between the air outlet and the heat exchanger, which helps in uniformizing the air velocity distribution and reducing pressure loss by preventing vortices.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Area of stationary object

If the heat exchanger width is made larger than the air outlet width, then the heat exchange area is increased, but the air velocity distribution becomes non-uniform and pressure loss increases

Engineering Contradiction:

Improveheat exchanger areaVSAvoidpressure loss

Core Design Contradiction:

Area of stationary objectVSLoss of energy

Solution Approach 1:

The air outlet is divided into multiple outlets arranged in the width direction, with each outlet connected to a corresponding section of the heat exchanger. This segmentation ensures that air velocity is distributed uniformly across the heat exchanger width, preventing non-uniform flow patterns and reducing pressure loss while maintaining adequate heat exchange area.

Inventive Principle:

Principle #1Segmentation

2Length of moving object

If the diffusers are enlarged to reduce the distance between air outlets and heat exchanger, then the air flow path is shortened, but the air passages are sharply enlarged causing pressure loss

Engineering Contradiction:

Improvedistance from air outlet to heat exchangerVSAvoidpressure loss

Core Design Contradiction:

Length of moving objectVSLoss of energy

Solution Approach 1:

The diffuser passages are designed with curved transition sections instead of sharp enlargements. The curved geometry allows air flow to transition smoothly from the air outlets to the heat exchanger, reducing turbulence and pressure loss while maintaining a compact distance between the air outlets and heat exchanger.

Inventive Principle:

Principle #14Spheroidality (Curvature)

3Stability of the object's composition

If guides are added to the diffusers to help air streams spread, then air flow distribution is improved, but pressure loss occurs in the guides

Engineering Contradiction:

Improveair flow distributionVSAvoidpressure loss

Core Design Contradiction:

Stability of the object's compositionVSLoss of energy

Solution Approach 1:

The air outlets are pre-positioned and oriented to discharge air directly toward the heat exchanger surface. This preliminary arrangement of air discharge direction eliminates the need for additional guiding structures, allowing air streams to spread naturally along the heat exchanger while minimizing pressure loss.

Inventive Principle:

Principle #10Preliminary action

4Length of moving object

If the air passages are sharply enlarged at diffusers, then the distance is reduced, but air streams do not spread along wall surfaces causing pressure loss

Engineering Contradiction:

Improvedistance from air outlet to heat exchangerVSAvoidpressure loss

Core Design Contradiction:

Length of moving objectVSObject-generated harmful factors

Solution Approach 1:

The diffuser passages incorporate curved transition sections that guide air streams to follow the wall surfaces smoothly. This curved geometry prevents flow separation and ensures that air streams adhere to the passage walls, reducing pressure loss while maintaining a short distance to the heat exchanger.

Inventive Principle:

Principle #14Spheroidality (Curvature)

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 design enhances efficiency and reduces noise by ensuring a uniform air velocity distribution and minimizing pressure loss, thereby improving air volume and static pressure effects.

Implementation Method 1

gas sent from the air outlet of the air-sending portion to the heat exchanger is rectified so that the pressure loss can be reduced

Methodology Applied

Scientific EffectFlow rectification:

Implementation Method 2

the pressure loss can be reduced. Further, a vortex region generated in the vicinity of the air outlet of the air-sending portion can be reduced

Methodology Applied

Scientific EffectPressure loss reduction:

Implementation Method 3

a heat exchanger, which is configured to exchange heat with gas sent from the air-sending portion

Methodology Applied

Scientific EffectHeat exchange: Heat Exchanger

Data Source

PatentUS11262098B2Indoor unit and air-conditioning apparatus

Publication Date: 2022.03.01 MITSUBISHI ELECTRIC CORP

AI summary

An indoor unit according to the present invention includes: an air-sending portion, which includes a casing having a rectangular air outlet and accommodating an impeller including a plurality of blades; a heat exchanger, which is configured to exchange heat with gas sent from the air-sending portion; and a guide portion, which includes an upper guide defining a passage for the gas and being arranged between an upper edge portion of the air outlet and an upper end portion of the heat exchanger and a lower guide defining a passage for the gas and being arranged between a lower edge portion of the air outlet and a lower end portion of the heat exchanger, and is open at side regions of the guide portion.