Indoor Unit Air-Inlet Bar Arrangement to Reduce Draft Resistance
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Solution Overview
Problem
The indoor unit of an air-conditioning apparatus experiences increased draft resistance and performance degradation due to bars in the air inlet, which are difficult to form closely-spaced and thin, especially when a propeller fan is placed nearby, leading to inefficiencies in air suction.
Innovation Solution
The bars in the air inlet are arranged within a virtual cylinder projected from the propeller fan's boss, reducing their overlap with the fan blades and minimizing draft resistance, while ensuring the structural strength of the casing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If bars are provided in the air inlet to ensure the strength of the casing, then the structural strength is improved, but the draft resistance of sucked-in air increases and performance degrades
Solution Approach 1:
The patent applies local quality by making the bars have different properties in different regions: in the first region (overlapping with fan blades), the bars are arranged sparsely or not at all to minimize draft resistance, while in the second region (not overlapping with blades), the bars are arranged densely to ensure structural strength. This spatial variation in bar arrangement allows the casing to maintain strength while reducing resistance to air flow.
2Object-affected harmful factors
If closely-spaced thin bars are formed in the air inlet to serve as fan guard, then safety is improved, but manufacturing difficulty increases due to resin molding constraints
Solution Approach 1:
The patent segments the air inlet region into two distinct regions: a first region where bars are arranged sparsely or absent to facilitate easy molding and reduce draft resistance, and a second region where bars are arranged densely to provide fan guard functionality. This segmentation allows the design to meet safety requirements without the manufacturing complexity of forming closely-spaced thin bars throughout the entire air inlet.
3Object-affected harmful factors
If bars are arranged densely in the air inlet to prevent finger entry, then safety is improved, but draft resistance increases and air flow is degraded
Solution Approach 1:
The patent applies local quality by making the bars have different properties in different regions: in the first region (overlapping with fan blades), the bars are arranged sparsely or not at all to minimize draft resistance, while in the second region (not overlapping with blades), the bars are arranged densely to ensure structural strength. This spatial variation in bar arrangement allows the casing to maintain strength while reducing resistance to air flow.
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 arrangement suppresses the increase in draft resistance and maintains the performance of the air-conditioning apparatus by reducing turbulent wake flow and noise levels, ensuring efficient air suction and motor input.
Implementation Method 1
at least one fan is provided for producing a forced convection in the duct
Implementation Method 2
the bars formed in the air inlet increase the draft resistance of sucked-in air
Data Source
Figure 1~2
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AI summary
[Object] An object is to obtain an indoor unit of an air-conditioning apparatus, the indoor unit including a propeller fan in the vicinity of an air inlet, the indoor unit being capable of ensuring the strength of a casing and suppressing degradation of performance by reducing an increase in draft resistance of sucked-in air. [Solution] In an indoor unit 1 of an air-conditioning apparatus, at least one propeller fan 10 having a fan guard 50 is disposed downstream of an air inlet 130 formed at the top of the indoor unit 1. The air inlet 130 is provided with bars 140. Each of the bars 140 is located, in a vertical cross-section perpendicular to the longitudinal direction of the bar 140, within a virtual cylinder 13 obtained by projecting a boss 11 of the propeller fan 10 in the direction of the rotation axis of the propeller fan 10.