Fan coil unit noise reduction structure

Abstract

This utility model discloses a noise reduction structure and unit for a fan coil unit, relating to the field of air conditioning technology. The noise reduction structure includes a perforated panel and a closed back panel arranged from the outside in, which are enclosed by a supporting frame to form a main noise reduction cavity filled with noise-absorbing cotton. Its innovation lies in the inclusion of a resonant noise reduction unit fixed inside the perforated panel. This unit consists of an open box and a resonant panel with micropores, forming a Helmholtz resonant cavity for reactive noise reduction of low-frequency noise. The supporting frame is an internally hollow, flow-guiding structure to reduce airflow resistance. This utility model, through the combination of resistive and reactive noise reduction, solves the problems of poor low-frequency noise absorption, easy airflow disturbance, and insufficient structural stability in existing technologies, achieving a balance between efficient wideband noise reduction, low flow resistance, and high structural stability.

Description

Technical Field

[0001] This utility model relates to the field of fan technology, and in particular to a noise reduction structure for fan coil units. Background Technology

[0002] Fan coil units, as terminal devices in central air conditioning systems, are widely used in various buildings. The quietness of their operation is an important indicator of indoor environmental quality. During operation, the motor and fan system of the unit generate broadband aerodynamic noise and structural vibration noise. Especially when the air volume is too large or the actual operating resistance of the system is less than the design residual pressure, the noise will exceed the standard, seriously affecting the user experience.

[0003] In existing technologies, noise reduction is often achieved by incorporating sound-absorbing structures into the unit's enclosure. For example, Chinese patent document CN206291447U discloses a sound-absorbing structure that uses a sound-absorbing cavity and sound-absorbing cotton between two panels. This structure utilizes the principle that sound waves entering the cavity through sound-absorbing holes are absorbed by the sound-absorbing material to reduce noise. However, this structure primarily relies on the resistive sound-absorbing properties of the sound-absorbing cotton, which is effective for mid-to-high frequency noise but has limited absorption efficiency for low-frequency noise. This is because low-frequency noise has long wavelengths and strong penetrating power, making it difficult for porous materials alone to effectively dissipate its energy. Therefore, developing a sound-absorbing structure capable of efficiently absorbing low-frequency noise is a pressing technical problem in this field. Summary of the Invention

[0004] The purpose of this invention is to provide a noise reduction structure for fan coil units, which can overcome the shortcomings of the existing technology.

[0005] To achieve the above objectives, a noise reduction structure for a fan coil unit is provided, comprising: a perforated panel and a closed back plate arranged sequentially from the outside to the inside, wherein the perforated panel and the closed back plate are connected by a support frame and enclosed to form a main noise reduction cavity, and the main noise reduction cavity is filled with noise reduction cotton. One or more resonant noise reduction units are fixedly installed on the inner side of the perforated panel. The resonant noise reduction unit includes an open box and a resonant panel that forms one side wall of the box. The resonant panel has several micro-holes. The box has a sealed cavity that communicates with the micro-holes, forming a Helmholtz resonant cavity. The resonant panel is closely attached to or parallel to the inner wall of the perforated panel and is spaced apart. The resonant noise reduction unit is located in the main noise reduction cavity and is wrapped with noise reduction cotton.

[0006] According to the aforementioned fan coil unit noise reduction structure, the thickness of the resonant panel is 0.8mm to 2.0mm, the pore diameter of the micropores is 0.5mm to 3mm, and the opening rate is 0.5% to 3%; the micropores are circular holes, slits, or combinations thereof, and the parameters are designed based on the specific low-frequency peak noise frequency during the operation of the fan coil unit.

[0007] According to the aforementioned fan coil unit noise reduction structure, the depth of the coverless box, i.e. the depth of the Helmholtz resonant cavity, is 20mm to 60mm; the open end of the coverless box is fixed to the inside of the perforated panel by bonding, welding or snap-fitting.

[0008] According to the aforementioned fan coil unit noise reduction structure, the supporting frame is an internally hollow flow-guiding supporting frame with a streamlined or airfoil-shaped structure on its windward side; the supporting frame completely covers the joint between the perforated panel and the closed back plate, and forms a continuous sealed frame along the circumference of the noise reduction structure.

[0009] According to the aforementioned fan coil unit noise reduction structure, the internal cavity of the support frame is filled with noise reduction material; the support frame is integrally injection molded from plastic or composite material, and its internal cavity is divided into multiple non-interconnected sub-chambers.

[0010] According to the aforementioned fan coil unit noise reduction structure, the thickness of the main noise reduction cavity is 30mm to 80mm, and the density of the noise reduction cotton is 30kg / m³ to 60kg / m³. The noise reduction cotton is centrifugal glass wool, rock wool, or polyester fiber cotton, and it is filled with a gradient density in the main noise reduction cavity, that is, the density of the area near the perforated panel is lower than the density of the area near the closed back panel.

[0011] According to the aforementioned fan coil unit sound-absorbing structure, it also includes a foam layer, which is disposed between the sound-absorbing cotton and the sealed back panel, and has a thickness of 10mm to 25mm; the foam layer is a polyurethane foam layer that is injected and cured on-site, and it is tightly bonded to the sealed back panel and the sound-absorbing cotton to form a composite layer that has both sound insulation and heat preservation functions.

[0012] A fan coil unit includes a housing and a motor and a duct casing disposed within the housing. The housing features at least one panel employing a noise-reducing structure as described in any one of claims 1 to 7. The noise-reducing structure is specifically disposed on the return air surface, the outlet air surface, or at a position directly opposite the motor and the duct casing of the housing, to specifically reduce noise radiation from the main noise sources.

[0013] This utility model has the following beneficial effects: 1. Compared with existing technologies, this utility model features an independent Helmholtz resonance silencing unit. This unit consists of a resonant panel designed with specific parameters and a coverless housing. It can generate strong resonance against specific low-frequency peak noise generated during fan operation, converting sound energy into heat energy, thus achieving precise reactive silencing. This effectively compensates for the shortcomings of relying solely on sound-absorbing cotton to treat low-frequency noise, complementing the resistive silencing of the main silencing cavity. This achieves synergistic and efficient absorption of broadband noise, especially persistent low-frequency noise, significantly improving the overall quietness of the unit.

[0014] 2. Compared with existing technologies, this utility model significantly enhances the overall structural rigidity and stability by embedding the resonant silencing unit within it and forming an interlocking wrapping structure with the silencing cotton, as well as employing a continuous sealed frame design that completely covers the panel edges. This structure can better withstand vibrations and wind pressure impacts during unit operation, effectively preventing loose connections and air leakage risks caused by component fatigue and deformation. This not only ensures the long-term stability of silencing performance but also reduces maintenance requirements and extends the service life of the unit. Attached Figure Description

[0015] The present invention will be further described below with reference to the accompanying drawings and embodiments; Figure 1 This is a schematic diagram of the noise reduction structure of the fan coil unit of this utility model; Figure 2 This is a cross-sectional schematic diagram of the noise reduction structure of the fan coil unit of this utility model; Figure 3 This is a top view schematic diagram of the noise reduction structure of the fan coil unit of this utility model; Figure 4 This is a front view of the noise reduction structure of the fan coil unit of this utility model.

[0016] Legend: 1. Support frame; 2. Perforated panel; 3. Resonance panel; 4. Open box; 5. Main silencing cavity; 6. Enclosed back panel. Detailed Implementation

[0017] This section will describe in detail the specific embodiments of the present utility model. The preferred embodiments of the present utility model are shown in the accompanying drawings. The purpose of the drawings is to supplement the textual description with graphics, so that people can intuitively and vividly understand each technical feature and the overall technical solution of the present utility model, but they should not be construed as limiting the scope of protection of the present utility model.

[0018] Reference Figure 1-4 The present invention relates to a noise reduction structure for a fan coil unit. This structure, as an independent plate, can be used to replace or form the side plate, top plate, or front panel of the fan coil unit housing.

[0019] Specifically, the silencing structure includes a perforated panel 2 and a closed back plate 6 arranged sequentially from the outside to the inside. The perforated panel 2 and the closed back plate 6 are connected by a support frame 1 and enclosed to form a main silencing cavity 5. In this embodiment, the support frame 1 is a hollow, flow-guiding frame with a streamlined cross-section, integrally injection molded from ABS engineering plastic. The frame 1 completely covers the joint between the perforated panel 2 and the closed back plate 6, forming a continuous sealed frame along the circumference of the silencing structure, effectively preventing air leakage and noise leakage.

[0020] The main anechoic chamber 5 is filled with centrifugal glass wool with a density of 48 kg / m³ as sound-absorbing material. As a preferred embodiment, the centrifugal glass wool is filled with a gradient density: the area near the perforated panel 2 is filled with a lower density cotton (about 30 kg / m³), while the area near the closed back panel 6 is filled with a higher density cotton (about 60 kg / m³). This structure is more conducive to the absorption of broadband sound energy.

[0021] The core innovation of this invention lies in the following: multiple resonant noise reduction units are bonded and fixed to the inner side of the perforated panel 2 using epoxy resin adhesive. Each resonant noise reduction unit consists of an open-top box 4 and a resonant panel 3. The resonant panel 3 is 1.2mm thick and has evenly distributed 1.5mm diameter circular holes with an opening ratio of 1.8%. The parameters of these micro-holes were determined based on targeted calculations of the low-frequency noise peak around 500Hz for a certain type of fan coil unit. The resonant panel 3 is parallel to the inner wall of the perforated panel 2, spaced approximately 5mm apart. The depth of the open-top box 4 (i.e., the depth of the Helmholtz resonant cavity) is 35mm. After installation, all these resonant noise reduction units are completely located within the main noise reduction cavity 5 and are tightly wrapped by centrifugal glass wool, forming an organic whole.

[0022] To further enhance sound insulation and thermal insulation performance, a 15mm thick in-situ injected polyurethane foam layer (not shown separately in the figure, but can be considered as part of the main sound-absorbing cavity 5) is installed between the centrifugal glass wool and the closed back panel 6. After curing, this foam layer is tightly bonded to the closed back panel 6 and the sound-absorbing cotton, forming a rigid composite structure that significantly enhances the strength of the entire sound-absorbing panel.

[0023] Unless otherwise specified, the constituent units of this utility model are obtained from conventional commercial channels or manufactured by conventional methods. Their specific structure, working principle, and possible control methods and spatial arrangement methods can adopt conventional choices in the field and should not be regarded as the innovation of this utility model. This is understandable to those skilled in the art, and this utility model patent will not be further elaborated in detail.

[0024] Working principle: When the fan coil unit is running, the broadband noise generated impacts this noise reduction structure.

[0025] Mid-to-high frequency noise: Most sound waves enter the main silencing cavity 5 through the holes in the perforated panel 2. When the sound waves propagate through the crisscrossing glass wool fibers, they are converted into heat energy and dissipated due to friction and viscous resistance, thus achieving efficient resistive silencing.

[0026] Specific low-frequency noise: The sound wave also passes through the perforated panel 2 and excites the resonant silencing unit behind it. When the frequency of the sound wave is consistent with the natural frequency of the Helmholtz resonator formed by the micro-holes on the resonant panel 3 and the cavity of the housing, the air column at the neck of the resonant cavity (at the micro-hole) will vibrate violently, rubbing against the hole wall and thus consuming a large amount of sound energy, achieving targeted resistance silencing of specific low-frequency peaks.

[0027] The streamlined design of the supporting frame 1 ensures smooth airflow and avoids secondary noise caused by structural turbulence.

[0028] By combining the above-mentioned "resistive noise reduction" and "resistive noise reduction", this utility model achieves efficient control of wide-frequency noise of fan coil units, especially low-frequency noise that is difficult to deal with.

[0029] The embodiments of the present utility model have been described in detail above with reference to the accompanying drawings. However, the present utility model is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present utility model.

Claims

1. A sound attenuation structure for a fan-coil unit, comprising: include: A perforated panel and a closed back panel are arranged sequentially from the outside to the inside. The perforated panel and the closed back panel are connected by a support frame and enclosed to form a main sound-absorbing cavity. The main sound-absorbing cavity is filled with sound-absorbing cotton. One or more resonant noise reduction units are fixedly arranged on the inner side of the perforated panel. The resonant noise reduction unit includes an open box and a resonant panel that forms one side wall of the box. The resonant panel has several micro-holes. The box has a sealed cavity that communicates with the micro-holes, forming a Helmholtz resonant cavity.

2. The noise reduction structure for a fan coil unit according to claim 1, characterized in that, The thickness of the resonant panel is 0.8 mm to 2.0 mm, the pore size of the micropores is 0.5 mm to 3 mm, and the porosity is 0.5% to 3%.

3. The noise reduction structure for a fan coil unit according to claim 1, characterized in that, The depth of the uncovered box, i.e. the depth of the Helmholtz resonant cavity, is 20mm to 60mm.

4. The noise reduction structure for a fan coil unit according to claim 1, characterized in that, The supporting frame is a hollow, flow-guiding supporting frame with a streamlined or airfoil-shaped structure on its windward side.

5. The noise reduction structure for a fan coil unit according to claim 1, characterized in that, The internal cavity of the supporting frame is filled with sound-absorbing material.

6. The noise reduction structure for a fan coil unit according to claim 1, characterized in that, The thickness of the main sound-absorbing cavity is 30mm to 80mm, and the density of the sound-absorbing cotton is 30kg / m³ to 60kg / m³.

7. The noise reduction structure for a fan coil unit according to claim 1, characterized in that, It also includes a foam layer, which is disposed between the sound-absorbing cotton and the sealed back panel, and has a thickness of 10mm to 25mm.

8. A fan coil unit, comprising a housing and a motor and a duct casing disposed within the housing, characterized in that, At least one panel of the enclosure adopts a sound-absorbing structure as described in any one of claims 1 to 7.

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