HVAC Unit Insert with Labyrinth Passageway for Noise Attenuation
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Solution Overview
Problem
Residential and commercial HVAC or heat pump units produce undesirable noise, particularly from fans and compressors, which is challenging to reduce in compact designs and often requires costly installation methods.
Innovation Solution
An acoustically absorbing insert with a labyrinth passageway and perforated panels is integrated into the HVAC or heat pump housing, forcing sound waves to reflect multiple times before entering the duct system, utilizing materials like foam to absorb sound and reduce parasitic losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If conventional duct silencers, liners and wraps are used for noise reduction, then noise attenuation is achieved, but installation costs increase and feasibility is reduced in existing home installations
Solution Approach 1:
The noise attenuation features are built into the HVAC unit itself during manufacturing, before installation. The insert with labyrinth passageways and acoustically absorbing material is pre-integrated into the housing, eliminating the need for costly post-installation duct modifications and making the system feasible for existing home installations.
Solution Approach 2:
An insert acting as an intermediary component is introduced between the noise-generating components (fan, compressor) and the duct system. This insert with its labyrinth passageways and absorbing material serves as a mediator that attenuates noise before it enters the ductwork, providing cost-effective noise reduction without requiring complex duct modifications.
2Volume of moving object
If HVAC units are designed to be compact, then space efficiency is improved, but noise reduction becomes more challenging in the confined space
Solution Approach 1:
The noise attenuation insert is nested within the existing HVAC housing, utilizing the available internal space efficiently. The labyrinth passageways and absorbing material are integrated into the housing structure itself, fitting compactly around the fan and compressor without requiring additional external space, thus maintaining compact unit dimensions while achieving effective noise reduction.
Solution Approach 2:
The labyrinth passageways utilize three-dimensional space within the housing by creating multiple turns and reflections in the noise path. This dimensional approach allows sufficient noise attenuation length to be achieved within the compact housing volume by routing sound waves through a tortuous path rather than a straight line.
3Object-generated harmful factors
If sound waves are forced through a labyrinth passageway with multiple reflections, then noise attenuation is improved, but parasitic losses from secondary flows increase
Solution Approach 1:
Acoustically absorbing porous materials are used to line the labyrinth passageways. These materials absorb sound energy through friction and viscous effects within their porous structure, providing noise attenuation while minimizing the generation of harmful secondary flows. The porous structure dissipates acoustic energy without creating significant pressure drops or parasitic losses.
Solution Approach 2:
The characteristics of the labyrinth passageways are optimized by adjusting parameters such as passage width, turn radius, and reflecting surface geometry. These parameter changes allow the design to achieve sufficient noise attenuation through multiple reflections while minimizing flow separation and secondary flows that would cause parasitic energy losses.
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 solution effectively minimizes noise production from the HVAC unit itself, reducing installation costs and achieving greater noise reduction than conventional methods, especially in confined spaces, and can be retrofitted or integrated into existing units.
Implementation Method 1
The insert is formed of an acoustically absorbing material... the acoustically absorbing material both absorbs sound and reduces parasitic losses from secondary flows within the passageway
Implementation Method 2
forcing a sound wave traveling through the HVAC or heat pump housing to pass through a labyrinth passageway that causes the sound wave to be reflected multiple times
Implementation Method 3
The panels are supported on a surface of the passageway and are configured (e.g., tuned) to attenuate noise at one or more predetermined frequencies
Data Source
AI summary
An environmental control unit, such as an HVAC or heat pump unit, includes an insert disposed within the device housing that provides noise attenuation features. The insert defines air flow paths within the housing. The insert may be formed of a foam material and may include multiple foam blocks that cooperate to form a serpentine passageway therein. The passageway includes multiple turns. The features further include perforated sheet metal panels disposed in the passageway at strategic locations. The perforations are shaped and dimensioned to correspond to the frequencies to be attenuated.