Adjustable Noise Attenuation Device for Use in Blow Through Air Handler/Furnace with Mixed Flow Blower Wheel

Abstract

An HVAC system comprises an air flow path, a heat exchanger in the air flow path, a blower in the air flow path to move air through the heat exchanger, and at least one Helmholtz resonator in the air flow path. The Helmholtz resonator may be placed in numerous places throughout the air flow path. The Helmholtz resonator may be adjustable. The Helmholtz resonator further may be automatically adjustable. The automatic adjustment may be based on a characteristic of at least one of the blower or the air in the air flow path. Characteristics of air moving through the air flow path may include airspeed, absolute pressure, a pressure change through a portion of the HVAC system, or an audio characteristic. The automatic adjustment may be based on a feedback pressure or an electrical signal from a sensor. The system may have multiple Helmholtz resonators.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority under 35 U.S.C. 119(e) to U.S. Provisional Patent Application No. 62/013,693 filed on Jun. 18, 2014 by Groskreutz, et al. and entitled “Adjustable Noise Attenuation Device for Use in Blow Through Air Handler/Furnace with Mixed Flow Blower Wheel,” the disclosure of which is hereby incorporated by reference in its entirety.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

REFERENCE TO A MICROFICHE APPENDIX

Not applicable.

BACKGROUND

Heating, ventilation, and air conditioning systems (HVAC systems) generally comprise one or more heat exchangers generally referred to as “condensers” that may comprise a condenser coil, and may be associated with one or more compressors and one or more fan assemblies. In operation, a compressor may compress refrigerant and discharge superheated refrigerant (i.e., refrigerant at a temperature greater than a saturation temperature of the refrigerant) to the condenser coil. As the refrigerant passes through the condenser coil, a fan assembly may be configured to selectively force air into contact with the condenser coil. In response to the air contacting the condenser coil, heat may be transferred from the refrigerant to the air, thereby desuperheating the refrigerant and/or otherwise reducing a temperature of the refrigerant. In some cases, the temperature of the refrigerant within the condenser coil is reduced to a saturation temperature of the refrigerant. Continued removal of heat from the refrigerant at the saturation temperature in combination with appropriately maintained pressure within the condenser coil may result in transforming some or all of the gaseous phase refrigerant to liquid phase refrigerant.

Refrigerant may generally exit the condenser coil in a liquid phase and/or a gaseous and liquid mixed phase. The refrigerant may thereafter be delivered from the condenser coil to a refrigerant expansion device where the refrigerant pressure is reduced and after which, the refrigerant is selectively discharged into a so-called evaporator coil of the HVAC system that may provide a cooling function.

Likewise, an HVAC system may comprise a heat generating section. The heat that is generated is used to heat air passing through the heat generating section. The heat may be generated via burning natural gas, burning coal, electric resistance wiring, and other methods that are well known in the art.

Whether being used for heating or cooling, the core function of the HVAC system is to move air either over the condensers or through the heat generating section, thereby altering the temperature of the air. The air is then distributed as desired. The air is moved using a blower of some type.

SUMMARY

In an embodiment, an HVAC system comprises an air flow path, a blower in the air flow path, a heat exchanger in the air flow path, and at least one Helmholtz resonator operably connected to the air flow path. The at least one Helmholtz resonator may be positioned in the air flow path of the blower. The HVAC system may also include a duct downstream or upstream of the heat exchanger. The duct may comprise at least one wall, and the at least one Helmholtz resonator may be operably connected to the wall. The HVAC system may also include an air inlet orifice, and the at least one Helmholtz resonator may be operably connected to the air inlet orifice. The Helmholtz resonator may be adjustable.

In an embodiment, an HVAC system comprises an air flow path, a blower in the air flow path, a heat exchanger in the air flow path, and at least one Helmholtz resonator operably connected to the air flow path. The at least one adjustable Helmholtz resonator is configured to adjust automatically based on a characteristic of at least one of the blower or an air stream downstream of the blower. The at least one characteristic of the air moving through the HVAC system may comprise airspeed, absolute pressure, a pressure change through a portion of the HVAC system, or an audio characteristic. The at least one adjustable Helmholtz resonator may be configured to adjust based on a feedback pressure, an electrical signal from a sensor, and/or a speed of the blower. The air flow path further may comprise an inner fan housing, the inner fan housing may comprise at least one wall, and the Helmholtz resonator may be positioned in a wall of the inner fan housing.

In an embodiment, a method of reducing noise in an HVAC system comprises moving air through an air flow path in the HVAC system using a blower, generating a noise signal having acoustic energy in response to the blower moving the air, moving the air past a Helmholtz resonator operably connected to the blower, and dampening the acoustic energy of the noise signal with the Helmholtz resonator in response to moving the air past the Helmholtz resonator. The HVAC system comprises: the blower and a heat exchanger. The method may also include adjusting the Helmholtz resonator in response to changes in at least one audio characteristic of the air. The adjusting may be performed automatically. The adjusting may be based on a feedback pressure, and the feedback pressure may be a pressure differential between a pressure downstream of the blower and a pressure upstream of the blower. The adjusting may be based on an electrical signal from a sensor associated with the blower. The adjusting may comprise changing a volume of the Helmholtz resonator. The adjusting may be based on a speed of the blower. The Helmholtz resonator may be built into a wall that is a portion of a duct ahead of the blower or in an air inlet orifice.

These and other features will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present disclosure and the advantages thereof, reference is now made to the following brief description, taken in connection with the accompanying drawings and detailed description:

FIG. 1 is a simplified schematic diagram of an HVAC system according to an embodiment of the disclosure;

FIG. 2 is a simplified schematic diagram of the air circulation paths of the HVAC system of FIG. 1;

FIG. 3 is a simplified schematic diagram of a portion of another HVAC system according to an embodiment of the disclosure;

FIG. 4 is a simplified schematic diagram of a portion of another HVAC system according to an embodiment of the disclosure;

FIG. 5 is a simplified schematic diagram of a portion of another HVAC system according to an embodiment of the disclosure;

FIG. 6 is a simplified schematic diagram of a portion of another HVAC system according to an embodiment of the disclosure.

DETAILED DESCRIPTION

In the drawings and description that follow, like parts are typically marked throughout the specification and drawings with the same reference numerals, respectively. In addition, similar reference numerals may refer to similar components in different embodiments disclosed herein. The drawing figures are not necessarily to scale. Certain features of the invention may be shown exaggerated in scale or in somewhat schematic form and some details of conventional elements may not be shown in the interest of clarity and conciseness. The present invention is susceptible to embodiments of different forms. Specific embodiments are described in detail and are shown in the drawings, with the understanding that the present disclosure is not intended to limit the invention to the embodiments illustrated and described herein. It is to be fully recognized that the different teachings of the embodiments discussed herein may be employed separately or in any suitable combination to produce desired results.

One problem with some HVAC systems is that at certain constant speeds they can create problematic noise that can be bothersome or irritating to people exposed to that noise.

Referring now to FIG. 1, a simplified schematic diagram of an HVAC system 100 is shown according to an embodiment of the disclosure. HVAC system 100 generally comprises an indoor unit 102, an outdoor unit 104, and a system controller 106. The system controller 106 may generally control operation of the indoor unit 102 and/or the outdoor unit 104. As shown, the HVAC system 100 is a so-called heat pump system that may be selectively operated to implement one or more substantially closed thermodynamic refrigeration cycles to provide a cooling functionality and/or a heating functionality.

Indoor unit 102 generally comprises an indoor heat exchanger 108, an indoor fan 110, and an indoor metering device 112. In an embodiment, indoor heat exchanger 108 is a plate fin heat exchanger configured to allow heat exchange between refrigerant carried within internal tubing of the indoor heat exchanger 108 and fluids that contact the indoor heat exchanger 108 but that are kept segregated from the refrigerant. In other embodiments, indoor heat exchanger 108 may comprise a spine fin heat exchanger, a microchannel heat exchanger, or any other suitable type of heat exchanger.

In an embodiment, the indoor fan 110 is a centrifugal blower comprising a blower housing, a blower impeller at least partially disposed within the blower housing, and a blower motor configured to selectively rotate the blower impeller. In other embodiments, the indoor fan 110 may comprise a mixed-flow fan and/or any other suitable type of fan. The indoor fan 110 is configured as a modulating and/or variable speed fan capable of being operated at many speeds over one or more ranges of speeds. In other embodiments, the indoor fan 110 may be configured as a multiple speed fan capable of being operated at a plurality of operating speeds by selectively electrically powering different ones of multiple electromagnetic windings of a motor of the indoor fan 110. In yet other embodiments, the indoor fan 110 may be a single speed fan. While illustrated and described as a single indoor fan 110, a plurality of fans may be present in any system, and each of the fans may be the same or different than any of the other fans.

In an embodiment, the indoor metering device 112 is an electronically controlled motor driven electronic expansion valve (EEV). In alternative embodiments, the indoor metering device 112 may comprise a thermostatic expansion valve, a capillary tube assembly, and/or any other suitable metering device. The indoor metering device 112 may comprise and/or be associated with a refrigerant check valve and/or refrigerant bypass for use when a direction of refrigerant flow through the indoor metering device 112 is such that the indoor metering device 112 is not intended to meter or otherwise substantially restrict flow of the refrigerant through the indoor metering device 112.

Outdoor unit 104 generally comprises an outdoor heat exchanger 114, a compressor 116, an outdoor fan 118, an outdoor metering device 120, and a reversing valve 122. In an embodiment, outdoor heat exchanger 114 is a spine fin heat exchanger configured to allow heat exchange between refrigerant carried within internal passages of the outdoor heat exchanger 114 and fluids that contact the outdoor heat exchanger 114 but that are kept segregated from the refrigerant. In other embodiments, outdoor heat exchanger 114 may comprise a plate fin heat exchanger, a microchannel heat exchanger, or any other suitable type of heat exchanger.

In an embodiment, the compressor 116 is a multiple speed scroll type compressor configured to selectively pump refrigerant at a plurality of mass flow rates. In alternative embodiments, the compressor 116 may comprise a modulating compressor capable of operation over one or more speed ranges, a reciprocating type compressor, a single speed compressor, and/or any other suitable refrigerant compressor and/or refrigerant pump.

In an embodiment, the outdoor fan 118 is an axial fan comprising a fan blade assembly and fan motor configured to selectively rotate the fan blade assembly. In other embodiments, the outdoor fan 118 may comprise a mixed-flow fan, a centrifugal blower, and/or any other suitable type of fan and/or blower. The outdoor fan 118 is configured as a modulating and/or variable speed fan capable of being operated at many speeds over one or more ranges of speeds. In other embodiments, the outdoor fan 118 may be configured as a multiple speed fan capable of being operated at a plurality of operating speeds by selectively electrically powering different ones of multiple electromagnetic windings of a motor of the outdoor fan 118. In yet other embodiments, the outdoor fan 118 may be a single speed fan. While illustrated and described as a single outdoor fan 118, a plurality of outdoor fans may be present in any system, and each of the fans may be the same or different than any of the other fans.

In an embodiment, the outdoor metering device 120 is a thermostatic expansion valve. In alternative embodiments, the outdoor metering device 120 may comprise an electronically controlled motor driven EEV similar to indoor metering device 112, a capillary tube assembly, and/or any other suitable metering device. The outdoor metering device 120 may comprise and/or be associated with a refrigerant check valve and/or refrigerant bypass for use when a direction of refrigerant flow through the outdoor metering device 120 is such that the outdoor metering device 120 is not intended to meter or otherwise substantially restrict flow of the refrigerant through the outdoor metering device 120.

In an embodiment, the reversing valve 122 is a so-called four-way reversing valve. The reversing valve 122 may be selectively controlled to alter a flow path of refrigerant in the HVAC system 100 as described in greater detail below. The reversing valve 122 may comprise an electrical solenoid or other device configured to selectively move a component of the reversing valve 122 between operational positions.

In an embodiment, the system controller 106 may generally comprise a touchscreen interface for displaying information and for receiving user inputs. The system controller 106 may display information related to the operation of the HVAC system 100 and may receive user inputs related to operation of the HVAC system 100. However, the system controller 106 may further be operable to display information and receive user inputs tangentially and/or unrelated to operation of the HVAC system 100. In some embodiments, the system controller 106 may not comprise a display and may derive all information from inputs from remote sensors and remote configuration tools. In some embodiments, the system controller 106 may comprise a temperature sensor and may further be configured to control heating and/or cooling of zones associated with the HVAC system 100. In some embodiments, the system controller 106 may be configured as a thermostat for controlling supply of conditioned air to zones associated with the HVAC system 100.

In some embodiments, the system controller 106 may also selectively communicate with an indoor controller 124 of the indoor unit 102, with an outdoor controller 126 of the outdoor unit 104, and/or with other components of the HVAC system 100. In some embodiments, the system controller 106 may be configured for selective bidirectional communication over a communication bus 128. In some embodiments, portions of the communication bus 128 may comprise a three-wire connection suitable for communicating messages between the system controller 106 and one or more of the HVAC system 100 components configured for interfacing with the communication bus 128. Still further, the system controller 106 may be configured to selectively communicate with HVAC system 100 components and/or any other device 130 via a communication network 132. In some embodiments, the communication network 132 may comprise a telephone network, and the other device 130 may comprise a telephone. In some embodiments, the communication network 132 may comprise the Internet, and the other device 130 may comprise a smartphone and/or other Internet-enabled mobile telecommunication device. In other embodiments, the communication network 132 may also comprise a remote server.

The indoor controller 124 may be carried by the indoor unit 102 and may be configured to receive information inputs, transmit information outputs, and otherwise communicate with the system controller 106, the outdoor controller 126, and/or any other device 130 via the communication bus 128 and/or any other suitable medium of communication. In some embodiments, the indoor controller 124 may be configured to communicate with an indoor personality module 134 that may comprise information related to the identification and/or operation of the indoor unit 102. In some embodiments, the indoor controller 124 may be configured to receive information related to a speed of the indoor fan 110, transmit a control output to an electric heat relay, transmit information regarding an indoor fan 110 volumetric flow-rate, communicate with and/or otherwise affect control over an air cleaner 136, and communicate with an indoor EEV controller 138. In some embodiments, the indoor controller 124 may be configured to communicate with an indoor fan controller 142 and/or otherwise affect control over operation of the indoor fan 110. In some embodiments, the indoor personality module 134 may comprise information related to the identification and/or operation of the indoor unit 102 and/or a position of the outdoor metering device 120.

In some embodiments, the indoor EEV controller 138 may be configured to receive information regarding temperatures and/or pressures of the refrigerant in the indoor unit 102. More specifically, the indoor EEV controller 138 may be configured to receive information regarding temperatures and pressures of refrigerant entering, exiting, and/or within the indoor heat exchanger 108. Further, the indoor EEV controller 138 may be configured to communicate with the indoor metering device 112 and/or otherwise affect control over the indoor metering device 112. The indoor EEV controller 138 may also be configured to communicate with the outdoor metering device 120 and/or otherwise affect control over the outdoor metering device 120.

The outdoor controller 126 may be carried by the outdoor unit 104 and may be configured to receive information inputs, transmit information outputs, and otherwise communicate with the system controller 106, the indoor controller 124, and/or any other device via the communication bus 128 and/or any other suitable medium of communication. In some embodiments, the outdoor controller 126 may be configured to communicate with an outdoor personality module 140 that may comprise information related to the identification and/or operation of the outdoor unit 104. In some embodiments, the outdoor controller 126 may be configured to receive information related to an ambient temperature associated with the outdoor unit 104, information related to a temperature of the outdoor heat exchanger 114, and/or information related to refrigerant temperatures and/or pressures of refrigerant entering, exiting, and/or within the outdoor heat exchanger 114 and/or the compressor 116. In some embodiments, the outdoor controller 126 may be configured to transmit information related to monitoring, communicating with, and/or otherwise affecting control over the outdoor fan 118, a compressor sump heater, a solenoid of the reversing valve 122, a relay associated with adjusting and/or monitoring a refrigerant charge of the HVAC system 100, a position of the indoor metering device 112, and/or a position of the outdoor metering device 120. The outdoor controller 126 may further be configured to communicate with a compressor drive controller 144 that is configured to electrically power and/or control the compressor 116.

The HVAC system 100 is shown configured for operating in a so-called cooling mode in which heat is absorbed by refrigerant at the indoor heat exchanger 108 and heat is rejected from the refrigerant at the outdoor heat exchanger 114. In some embodiments, the compressor 116 may be operated to compress refrigerant and pump the relatively high temperature and high pressure compressed refrigerant from the compressor 116 to the outdoor heat exchanger 114 through the reversing valve 122 and to the outdoor heat exchanger 114. As the refrigerant is passed through the outdoor heat exchanger 114, the outdoor fan 118 may be operated to move air into contact with the outdoor heat exchanger 114, thereby transferring heat from the refrigerant to the air surrounding the outdoor heat exchanger 114. The refrigerant may primarily comprise liquid phase refrigerant and the refrigerant may flow from the outdoor heat exchanger 114 to the indoor metering device 112 through and/or around the outdoor metering device 120 which does not substantially impede flow of the refrigerant in the cooling mode. The indoor metering device 112 may meter passage of the refrigerant through the indoor metering device 112 so that the refrigerant downstream of the indoor metering device 112 is at a lower pressure than the refrigerant upstream of the indoor metering device 112. The pressure differential across the indoor metering device 112 allows the refrigerant downstream of the indoor metering device 112 to expand and/or at least partially convert to a two-phase (vapor and gas) mixture. The two phase refrigerant may enter the indoor heat exchanger 108. As the refrigerant is passed through the indoor heat exchanger 108, the indoor fan 110 may be operated to move air into contact with the indoor heat exchanger 108, thereby transferring heat to the refrigerant from the air surrounding the indoor heat exchanger 108, and causing evaporation of the liquid portion of the two phase mixture. The refrigerant may thereafter re-enter the compressor 116 after passing through the reversing valve 122.

To operate the HVAC system 100 in the so-called heating mode, the reversing valve 122 may be controlled to alter the flow path of the refrigerant, the indoor metering device 112 may be disabled and/or bypassed, and the outdoor metering device 120 may be enabled. In the heating mode, refrigerant may flow from the compressor 116 to the indoor heat exchanger 108 through the reversing valve 122, the refrigerant may be substantially unaffected by the indoor metering device 112, the refrigerant may experience a pressure differential across the outdoor metering device 120, the refrigerant may pass through the outdoor heat exchanger 114, and the refrigerant may reenter the compressor 116 after passing through the reversing valve 122. Most generally, operation of the HVAC system 100 in the heating mode reverses the roles of the indoor heat exchanger 108 and the outdoor heat exchanger 114 as compared to their operation in the cooling mode.

Referring now to FIG. 2, a simplified schematic diagram of the air circulation paths for a structure 200 conditioned by two HVAC systems 100 is shown. In this embodiment, the structure 200 is conceptualized as comprising a lower floor 202 and an upper floor 204. The lower floor 202 comprises zones 206, 208, and 210 while the upper floor 204 comprises zones 212, 214, and 216. The HVAC system 100 associated with the lower floor 202 is configured to circulate and/or condition air of lower zones 206, 208, and 210 while the HVAC system 100 associated with the upper floor 204 is configured to circulate and/or condition air of upper zones 212, 214, and 216.

In addition to the components of HVAC system 100 described above, in this embodiment, each HVAC system 100 further comprises a ventilator 146, a prefilter 148, a humidifier 150, and a bypass duct 152. The ventilator 146 may be operated to selectively exhaust circulating air to the environment and/or introduce environmental air into the circulating air. The prefilter 148 may generally comprise a filter media selected to catch and/or retain relatively large particulate matter prior to air exiting the prefilter 148 and entering the air cleaner 136. The humidifier 150 may be operated to adjust a humidity of the circulating air. The bypass duct 152 may be utilized to regulate air pressures within the ducts that form the circulating air flow paths. In some embodiments, air flow through each bypass duct 152 may be selectively regulated by each respective bypass damper 154, while air flow delivered to each of zones 206, 208, 210, 212, 214, and 216 through air supply ducts 234, 236, 238, 240, 242, and 244, respectively, may be selectively regulated by corresponding optional zone dampers 156. In some embodiments, return air flow to lower zone return plenum 218 may flow through return ducts 220, 222, and 224 and may be selectively regulated by return dampers 246, 248, and 250, respectively. In some embodiments, return air flow to upper zone return plenum 226 may flow through return ducts 228, 230, and 232 and may be selectively regulated by return dampers 252, 254, and 256, respectively. In other embodiments, return air through return ducts 220, 222, 224, 228, 230, and 232 may be selectively aided by controllable, variable speed return fans 258, 260, 262, 264, 266, and 268, respectively.

Each HVAC system 100 may also further comprise a zone thermostat 158 and a zone sensor 160. In some embodiments, a zone thermostat 158 may communicate with the system controller 106 and may allow a user to control a temperature, humidity, and/or other environmental setting for the zone in which the zone thermostat 158 is located. Further, the zone thermostat 158 may communicate with the system controller 106 to provide temperature, humidity, and/or other environmental feedback regarding the zone in which the zone thermostat 158 is located. In some embodiments, a zone sensor 160 may also communicate with the system controller 106 to provide temperature, humidity, and/or other environmental feedback regarding the zone in which the zone sensor 160 is located. In addition, in some embodiments, the system controller 106 may also monitor temperature, humidity, and/or other environmental settings for the zone in which the system controller 106 is located.

In some embodiments, the system controllers 106 may be configured for bidirectional communication with each other and may further be configured so that a user may, using any of the system controllers 106, monitor and/or control any of the HVAC system 100 components regardless of which zones the components may be associated with. Further, each system controller 106, each zone thermostat 158, and each zone sensor 160 may comprise a humidity sensor and/or a temperature sensor. As such, it will be appreciated that structure 200 is equipped with a plurality of humidity sensors and/or a plurality of temperature sensors in a plurality of different locations. Accordingly, each system controller 106, zone thermostat 158, and zone sensor 160 may comprise a wired or wireless connection depending on the configuration of the HVAC system 100. In some embodiments, a user may effectively select which of the plurality of humidity sensors and/or plurality of temperature sensors is used to control operation of one or more of the HVAC systems 100.

While HVAC systems 100 are shown as a so-called split system comprising an indoor unit 102 located separately from the outdoor unit 104, alternative embodiments of an HVAC system 100 may comprise a so-called package system in which one or more of the components of the indoor unit 102 and one or more of the components of the outdoor unit 104 are carried together in a common housing or package. The HVAC system 100 is shown as a so-called ducted system where the indoor unit 102 is remotely located from the conditioned zones, thereby requiring air ducts 234, 236, 238, 240, 242, and 244 to route the circulating air.

HVAC systems are constantly being improved in various ways. One undesirable characteristic of HVAC systems is that they can produce noise, sometimes at levels that are not enjoyable to people nearby. Helmholtz resonators can be used in an HVAC system to reduce the acoustic energy of certain frequencies of sound coming from the system.

Referring now to FIG. 3, a simplified schematic diagram of a portion 300 of an HVAC system is shown according to an embodiment of the disclosure. The portion 300 can be part of either an indoor or outdoor unit, though the indoor unit is more likely to have noise issues. Included in portion 300 is a section of upstream ductwork 302, an air intake orifice 304, a heat exchanger 306, a blower 308, a downstream section of ductwork 310 and a Helmholtz resonator 312. Elements 302, 304, 306, 308 and 310 together comprise an air flow path 318. As stated above, a complete HVAC system would also include numerous other components, such as controllers, filters, etc.

The moving of air along the air flow path 318 is accomplished primarily by the blower 308. The air is moved into the upstream ductwork 302, through the air intake orifice 304, through the blower 308, through the heat exchanger 306, and then out through the downstream ductwork 310.

While in FIG. 3 the blower 308 is shown being proximate the heat exchanger 306, the blower could be placed in other locations relative to or within the air flow path 318, so long as the blower 308 is able to move air through the air flow path 318. For instance, the blower could be located before or in the upstream ductwork 302, in or after the downstream ductwork 310, or other locations that would move air through the air flow path 318. A preferred system may have more than one blower 308 moving air through the air flow path 318. Further, multiple blowers could be located in different locations. The blower 308 could be a more traditional forward curve blower, or it preferably could be a mixed flow type blower as described in more detail herein. Mixed flow type blowers offer significant efficiency benefits compared to forward curve blowers, but they also can produce noise in specific frequencies. This noise may be unpleasant to some people who are exposed to it.

The blower 308 further comprises blades 314 set within an inner fan housing 316. To optimize performance of the blower 308, the blades 314 are set very close to the surface of the inner fan housing 316. By being set very close, the blades 314 create a chopping effect on the air moving along the air flow path 318, and thereby, a certain frequency of sound, which may be related to the rotational speed of the blades 314.

The Helmholtz resonator 312 is shown in the downstream ductwork 310. The Helmholtz resonator 312 can also be in other locations in the airstream, such as in the upstream ductwork, in the air inlet orifice, or in the inner fan housing. The Helmholtz resonator 312 can be of various forms and configurations as are well known in the art, such as a tube, a perforated honeycomb sheet, or other structure. The Helmholtz resonator 312 can be a separate unit that is installed into the system, or it may be comprised partially or completely by various surfaces already present in the system, such as walls, etc., thereby reducing the number of parts needed and possibly the cost of the resonator. Multiple Helmholtz resonators can be used in the system.

A Helmholtz resonator (or Helmholtz oscillator, as it is also known) is a container of gas (usually air) with an open hole (or neck or port). A volume of air in and near the open hole vibrates because of the ‘springiness’ of the air inside. A common example is an empty bottle. To illustrate how it works, air moving across the top of the bottle causes the air inside to vibrate. The vibration is due to the ‘springiness’ of air. When compressed, the pressure of the air in the bottle increases and the air tends to expand back to its original volume. Consider a ‘lump’ of air at the neck of a bottle. The passing air jet can force this lump of air a little way down the neck, thereby compressing the air inside. That pressure now drives the ‘lump’ of air out but, when it gets to its original position, its momentum takes it outside the body a small distance. This rarifies the air inside the body, which then sucks the ‘lump’ of air back in. It can thus vibrate like a mass on a spring. The jet of air passing over the opening is capable of deflecting alternately into the bottle and outside, which provides the power to keep the oscillation going.

Helmholtz resonators make a somewhat restrictive specific frequency of sound, depending on the volume of the resonator, the length of the neck, and the area of the opening. The equation for calculating the resultant frequency is

$f=\frac{v}{\pi }\times \sqrt{\frac{A}{\mathrm{VL}}}$

where f is the resultant frequency, v is the velocity of sound, V is the volume of the resonator, A is the area of the opening, and L is the length of the neck. Thereby, one can change the frequency being issued from it by varying any of the variables V, A or L.

A Helmholtz resonator can be used to absorb and/or cancel a particular frequency. This is, if the Helmholtz resonator has a frequency set at the problematic frequency one wishes to dampen, the acoustic energy of the frequency in the passing air can stimulate resonance in the Helmholtz resonator, thereby taking away energy at the desired frequency from the acoustic energy in the passing air. Hence, it may be beneficial to have a Helmholtz resonator present in the air flow path 318 to at least partially dampen the acoustic energy of a problematic frequency caused by the fan blades 314 interacting with the inner housing surface 316.

If the blower operates only at one speed, then it is a relatively simple process to calculate the problematic frequency and design a Helmholtz resonator to cancel or reduce the energy of the problematic frequency. If the blower operates at various speeds, it may be that different problematic frequencies arise at different blower speeds. In such a situation, it may be desirable to use an adjustable Helmholtz resonator. That is, and referring again to FIG. 3, the blower 308 can use a variable speed motor. Thereby, the blower 308 may generate different frequencies of sound in the airflow at different speeds, at least some of those differing frequencies being problematic to people proximate the HVAC system. It may be that only one frequency is problematic, and hence a fixed Helmholtz resonator is sufficient. But if there are multiple possible problematic frequencies, a variable Helmholtz resonator can be included in the air stream.

While Helmholtz resonators can be tuned numerous ways, specifically by varying one or more of the variables V, A and L, typically the easiest and simplest variable to alter would be the volume. Referring now to FIG. 4, a simplified schematic diagram of a portion 400 of an HVAC system is shown according to an embodiment of the disclosure. Included in portion 400 is a section of upstream ductwork 402, an air intake orifice 404, a heat exchanger 406, a blower 408, a downstream section of ductwork 410, a Helmholtz resonator 412, and a controller 414. Elements 402, 404, 406, 408 and 410 together comprise an air flow path 420. The controller 414 controls both the blower 408 and the Helmholtz resonator 412. The Helmholtz resonator 412 comprises a tube with a movable bottom section 416 to allow the volume of the resonator to be varied. While shown in this particular configuration, one can readily see that there are any number of ways to vary the volume V.

Through testing prior to installation of the unit, the potential problematic frequencies can be correlated with the various speeds of the blower 408, and the appropriate volume V can be calculated to yield the desired result. In operation, the controller 414, which may already by controlling the speed of blower 408, may also control the volume V of the Helmholtz resonator 412 to optimally reduce the acoustic energy of various problematic frequencies in the air flow path 420.

The volume V of the Helmholtz resonator can also be dynamically and/or selectively adjusted during use. Referring now to FIG. 5, in another embodiment, a simplified schematic diagram of a portion 500 of an HVAC system is shown according to an embodiment of the disclosure. Included in portion 500 is a section of upstream ductwork 502, an air intake orifice 504, a heat exchanger 506, a blower 508, a downstream section of ductwork 510, a Helmholtz resonator 512, a controller 514 and a sensor 516. Elements 502, 504, 506, 508 and 510 together comprise an air flow path 520. The sensor 516 is able to sense a characteristic of the air in the air flow path 520. That characteristic could be an actual measurement of frequencies, or some other characteristic that would allow one to determine what frequencies are present in the air flow path 520. The controller 514 is operably connected to the Helmholtz resonator 512, and able to control the volume V. The Helmholtz resonator 512 comprises a tube with a movable bottom section 518 to allow the volume V of the resonator to be varied. The controller 514 is able to control the position of the movable bottom section 518, and hence the volume V. The sensor 516 is likewise connected to the controller 514. The controller 514 then uses the data provided by the sensor 516 to determine a preferable position for the movable bottom section 518, and moved it to that position accordingly.

In the alternative, the controller 514 could be combined with either the Helmholtz resonator 512, or the sensor 516. Or, the controller 514 could be part of the main controller that controls the fan, not shown.

The portion 500 may include more than one sensor, to measure, e.g., pressure at various points in the air flow path 520. The collected information may possibly be useful as an alternative way to estimate the frequency of sounds in the air flow path 520.

While the Helmholtz resonator 512 is shown in this particular configuration, one can readily see that there are any number of ways to vary the volume V. Likewise, one could also choose to vary the length of the neck L, or the area of the opening A.

It is also possible to allow manual adjustment of the Helmholtz resonator 512. This would be accomplished by connecting the controller 514 to a dial (not shown) that would be accessible to a person listening to the HVAC system. Thereby, the fine tuning could be by ear.

Referring now to FIG. 6, in another embodiment, a simplified schematic diagram of a portion 600 of an HVAC system is shown according to an embodiment of the disclosure. Included in portion 600 is a section of upstream ductwork 602, an air intake orifice 604, a heat exchanger 606, a blower 608, a downstream section of ductwork 610, a Helmholtz resonator 612, an air inlet filter 614 and a pitot tube 616. Elements 602, 604, 606, 608, 610 and 614 together comprise an air flow path 620. Air entering the air flow path 620 experiences a pressure drop across the air inlet filter 614. The air also experiences a pressure rise across the blower 608. With moving air the total air pressure (static+dynamic pressure) is higher than the static air pressure. The inlet to the Helmholtz resonator 612 “sees” static air pressure at the air intake orifice 604 (low pressure area). A pitot tube 616 or similar device may be oriented to “see” total air pressure at the blower discharge (high pressure area). The pressure differential between the static air inlet pressure and the total air discharge pressure may be utilized to actuate a device that changes the volume of the Helmholtz resonator. For example, a piston 618 inside the Helmholtz resonator 612 may move based on the pressure differential experienced. The portion 600 may also include a controller, not shown, that may use the pressure differential to determine a setting for the piston 618 and move piston 618 accordingly. The pressure differential may also be used to activate a device that changes other features of the Helmholtz resonator in order to change the operating frequency of said device.

At least one embodiment is disclosed and variations, combinations, and/or modifications of the embodiment(s) and/or features of the embodiment(s) made by a person having ordinary skill in the art are within the scope of the disclosure. Alternative embodiments that result from combining, integrating, and/or omitting features of the embodiment(s) are also within the scope of the disclosure. Use of broader terms such as comprises, includes, and having should be understood to provide support for narrower terms such as consisting of, consisting essentially of, and comprised substantially of. Accordingly, the scope of protection is not limited by the description set out above but is defined by the claims that follow, that scope including all equivalents of the subject matter of the claims. Each and every claim is incorporated as further disclosure into the specification and the claims are embodiment(s) of the present invention.

Claims

1. An HVAC system comprising:

an air flow path;

a blower in the air flow path;

a heat exchanger in the air flow path; and

at least one Helmholtz resonator, operably connected to the air flow path.

2. The HVAC system of claim 1, wherein the at least one Helmholtz resonator is positioned in the air flow path of the blower.

3. The HVAC system of claim 1, further comprising a duct downstream or upstream of the heat exchanger, the duct comprising at least one wall, the at least one Helmholtz resonator operably connected to the wall.

4. The HVAC system of claim 1, further comprising an air inlet orifice, wherein the at least one Helmholtz resonator is operably connected to the air inlet orifice.

5. The HVAC system of claim 1, wherein the Helmholtz resonator is adjustable.

6. An HVAC system comprising:

an air flow path;

a blower in the air flow path;

a heat exchanger in the air flow path; and

at least one Helmholtz resonator, operably connected to the air flow path,

wherein the at least one adjustable Helmholtz resonator is configured to adjust automatically based on a characteristic of at least one of the blower or an air stream downstream of the blower.

7. The HVAC system of claim 6, wherein the at least one characteristic of the air moving through the HVAC system comprises airspeed, absolute pressure, a pressure change through a portion of the HVAC system, or an audio characteristic.

8. The HVAC system of claim 6, wherein the at least one adjustable Helmholtz resonator is configured to adjust based on a feedback pressure.

9. The HVAC system of claim 6, wherein the at least one adjustable Helmholtz resonator is configured to adjust based on an electrical signal from a sensor.

10. The HVAC system of claim 6, wherein the at least one adjustable Helmholtz resonator is configured to adjust based on a speed of the blower.

11. The HVAC system of claim 6, wherein the air flow path further comprises an inner fan housing, the inner fan housing comprising at least one wall,

wherein the Helmholtz resonator is positioned in a wall of the inner fan housing.

12. A method of reducing noise in an HVAC system, the method comprising:

moving air through an air flow path in the HVAC system using a blower, wherein the HVAC system comprises: the blower and a heat exchanger;

generating a noise signal having acoustic energy in response to the blower moving the air;

moving the air past a Helmholtz resonator operably connected to the blower; and

dampening the acoustic energy of the noise signal with the Helmholtz resonator in response to moving the air past the Helmholtz resonator.

13. The method of claim 12, further comprising adjusting the Helmholtz resonator in response to changes in at least one audio characteristic of the air.

14. The method of claim 13, wherein the step of adjusting is performed automatically.

15. The method of claim 13, wherein the step of adjusting is based on a feedback pressure.

16. The method of claim 15, wherein the feedback pressure is a pressure differential between a pressure downstream of the blower and a pressure upstream of the blower.

17. The method of claim 13, wherein the step of adjusting is based on an electrical signal from a sensor associated with the blower.

18. The method of claim 13, wherein the step of adjusting comprises changing a volume of the Helmholtz resonator.

19. The method of claim 12, wherein the step of adjusting is based on a speed of the blower.

20. The method of claim 12, wherein the Helmholtz resonator is built into a wall that is a portion of a duct ahead of the blower or in an air inlet orifice.