A thermally-enhanced, insulated component for use with an HVAC system includes a component having an outer surface usable with an HVAC system, the component being substantially filled with an insulating material. A thin, dimensionally stable layer of thermal barrier material having opposed surfaces is disposed inside the component at a predetermined distance from the outer surface of the component. The thermal barrier layer is in contact with the insulating material on at least one surface of the opposed surfaces. When the outer surface of the component is subjected to an elevated temperature, the thermal barrier layer maintains a sufficient temperature differential between the surface of the opposed surfaces of the thermal barrier layer facing opposite the outer surface and the surface of the opposed surfaces of the thermal barrier layer facing the outer surface so that the insulating material produces a reduced rate of smoke.

FIELD OF THE INVENTION

The present invention is directed to thermally-enhanced HVAC constructions or components, and more particularly, is directed to thermally-enhanced foam-filled HVAC constructions or components.

BACKGROUND OF THE INVENTION

Heating, ventilation and air conditioning (“HVAC”) systems are commonly used in many climate control applications. Air Handling Units (AHUs) are one of several components in HVAC systems. They are an important component as the AHU houses a number of components used in the system to provide forced air for climate control in a particular structure. AHU components typically include motors, heating/cooling coils, and blowers as well as the required interface connections to these components to effect such climate control.

The AHU is an enclosed interconnected framed panel structure. The framed panel structures have insulated panels that are supported between framing members, also referred to as raceways, to define interconnected rectangular compartments. Typically, the insulating material used in the panel is polyurethane foam that may be installed as a block, or injected as a foam, which cures to form a core within the panel.

Polyurethane foam insulation has superior insulating and indoor air quality (“IAQ”) properties versus fiberglass insulation. Although fiberglass has been the insulation of choice in many industries, foam insulation has become favored over fiberglass due to its reduced construction costs and increased energy savings potential. Foam insulation is currently heavily utilized in many industries, including household appliances (refrigerators, freezers), walk-in coolers (grocery stores, food processing plants) and HVAC units (AHUs and packaged products). However, a significant drawback to foam-insulated products is smoke generation when subjected to elevated temperatures, such as those generated during a fire. Smoke generation, or smoke spread, by foam-insulated panels is significantly increased with panels having thicknesses exceeding approximately one-half inch to one inch, depending upon the type of insulating material used, which thickness is typically exceeded to provide adequate insulating performance. While additives may be added to the foam insulation mixture to enhance flame retardant characteristics, those same chemicals typically adversely affect the smoke spread characteristics.

Flame and smoke generation indexes are predominantly measured utilizing a test conducted in accordance with the procedure outlined by the American Society for Testing and Materials in ASTM E 84-01, “Standard Test Method for Surface Burning Characteristics of Building Materials” (the National Fire Protection Agency in NFPA 255, the American National Standards Institute/Underwriters Laboratories in ANSI/UL 723 and the Uniform Building Code in UBC 8-1).

The index is based on a standard that is given a value of 100, such as red oak having a pre-determined moisture content. Therefore, any measured index value is compared to the standard value, and typically, fractional portions of the standard value are selected as classifications within an industry. Different industries permit differing levels of flame and smoke generation. The walk-in cooler industry, for instance, uses standards that allow a smoke generation index as high as 450 per ASTM E84, which can be easy to achieve, but uses a flame spread designation that is typically classified as Class I, which corresponds to a flame spread index of no higher than 25, or one-fourth of the index of red oak. Thus, walk-in cooler industry places more emphasis on the rate of flame spread as a measure of safety.

A low flame spread index can be achieved in foam-filled panels by mixing the foam with readily available flame-retardants. Foam insulation for panels and walls with one-half inch thickness or less typically contains a minimal amount of foam insulation material, thus enabling the panel to pass the common 25 flame and 50 smoke index requirements of NFPA 90A per ASTM E84. However, foam-insulated panels and walls greater than one-half inch in thickness must typically use additional materials or components to minimize heat transfer, and lower smoke generation index values to meet the above smoke index requirement, or utilize agency listings (UL, Environmental Technology Laboratory (“ETL”)) to provide “proof” of safety. To provide the required amount of insulation, panels used with HVAC systems must typically be substantially thicker than one-half inch.

Per standard building codes, the outer casing material of panels for HVAC systems must typically provide a 15-minute flame barrier, such that the flame does not come into direct contact with the insulating material, if present, which is typically flammable material. However, even with outer casing materials that provide a 15-minute barrier, the flame/smoke performance characteristics of the panel typically do not sufficiently improve. That is, without an additional thermal barrier material or component, a foam panel insulation system will not meet the 25/50 flame/smoke generation requirements of NFPA 90A per ASTM E84.

What is needed is a thermal barrier material or component that can be used with household appliances, walk-in coolers and HVAC units and provides improved flame/smoke performance characteristics.

SUMMARY OF THE INVENTION

The present invention relates to a thermally-enhanced component for use with an air handling unit including a substantially enclosed structure having an interior surface and an exterior surface. At least one sheet of a non-woven ceramic material has opposed surfaces being disposed inside the structure at a predetermined distance from the exterior surface of the structure, the at least one sheet being configured to provide a thermal barrier. Insulating material is disposed inside the structure and in contact with at least one surface of the at least one sheet, the insulating material having a predetermined rate of smoke generation at a predetermined temperature. Wherein upon the exterior surface of the structure being subjected to the predetermined temperature sufficient to produce smoldering of the insulating material disposed inside the structure, the at least one sheet providing a sufficient temperature differential between the opposed surfaces of the at least one sheet to reduce the predetermined rate of smoke generated by the insulating material. For purposes herein, smoldering is defined as to burn sluggishly, with or without flame, and often with much smoke, or to be consumed by smoldering. Thus, the terms “smolder” and “consume” when used in the context of the insulating material are understood to characterize the condition of insulating material that produces smoke in response to the insulating material being exposed or subjected to sufficient heat.

The present invention further relates to a thermally-enhanced component for use with an HVAC system including a substantially enclosed structure having an interior surface and an exterior surface, the structure being substantially filled with an insulating material. At least one sheet of a non-woven ceramic material having opposed surfaces is disposed inside the structure at a predetermined distance from the exterior surface of the structure, the at least one sheet being configured to provide a thermal barrier. Insulating material is disposed inside the structure and in contact with at least one surface of the at least one sheet, the insulating material having a predetermined rate of smoke generation at a predetermined temperature. Wherein upon the exterior surface of the structure being subjected to the predetermined temperature sufficient to produce smoldering of the insulating material disposed inside the structure, the at least one sheet provides a sufficient temperature differential between the opposed surfaces of the at least one sheet to reduce the predetermined rate of smoke generated by the insulating material.

The present invention also relates to a thermally-enhanced component for use with an HVAC system including a substantially enclosed structure having an interior surface and an exterior surface. At least one sheet of a non-woven ceramic material has opposed surfaces being disposed inside the structure at a predetermined distance from the exterior surface of the structure, the at least one sheet being configured to provide a thermal barrier. Wherein upon the exterior surface of the structure being subjected to a reduced temperature associated with refrigeration cycles, the at least one sheet provides a sufficient temperature differential between the opposed surfaces of the at least one sheet such that condensation is substantially prevented from forming along the exterior surface of the structure.

The present invention additionally relates to a component for separating different regions of a structure including a substantially enclosed structure having an interior surface and an exterior surface. At least one sheet of a non-woven ceramic material having opposed surfaces is disposed inside the structure at a predetermined distance from the exterior surface of the structure, the at least one sheet being configured to provide a thermal barrier. Insulating material is disposed inside the structure and in contact with at least one surface of the at least one sheet, the insulating material having a predetermined rate of smoke generation at a predetermined temperature. Wherein upon the exterior surface of the structure being subjected to the predetermined temperature sufficient to produce smoldering of the insulating material disposed inside the structure, the at least one sheet providing a sufficient temperature differential between the opposed surfaces of the at least one sheet to reduce the predetermined rate of smoke generated by the insulating material.

The present invention further relates to a component for separating different regions of a structure which includes a substantially enclosed structure having an interior surface and an exterior surface. At least one sheet of non-woven ceramic material having opposed surfaces is disposed inside the component at a predetermined distance from the outer surface of the component to form a thermal barrier layer. The thermal barrier layer is in contact with the insulating material on at least one surface of the opposed surfaces of the thermal barrier layer. Upon the outer surface of the component being subjected to an elevated temperature sufficient to produce smoldering of insulating material, the thermal barrier layer maintains a sufficient temperature differential between the opposed surfaces of the thermal barrier layer such that a reduced rate of smoke, if any, is produced.

An advantage of the present invention is improved flame/smoke performance characteristics for household appliances, walk-in coolers and air conditioning units.

A yet further advantage of the present invention is insulated panels having improved acoustic attenuation characteristics in household appliances, walk-in coolers and air conditioning units.

A still further advantage of the present invention is that it that may prevent the formation of condensation on the outer surfaces of HVAC components, such as drain plumbing or drain pans in an AHU.

DETAILED DESCRIPTION OF THE INVENTION

One embodiment of an AHU10that incorporates a thermally enhanced component or construction of the present invention is depicted inFIG. 1. AHU10is an enclosed framed panel structure12, or has a series of interconnected framed panel structures12. Each framed panel structure12preferably defines a rectangular compartment that is configured to enclose or house components, which provide forced air for climate control in a particular structure. AHU components typically include motors, heating/cooling coils, and blowers as well as the required interface connections to these components to effect such climate control. Framed panel structures12have a plurality of insulated panels300that are each structurally and sealingly supported by a raceway frame22. Each raceway frame22is comprised of a plurality, of raceways20, preferably four, that are interconnected by corner members200.

Referring toFIGS. 2,3and16, in a preferred embodiment of the present invention, raceway20defines a closed geometric profile including a first surface26which extends to a substantially squared first recess28, a second surface30extending into a substantially squared second recess32, a first closing portion33extending from first recess28, a second closing portion34extending from second recess32, a substantially squared third recess35extending from second closing portion34, first closing portion33and third recess35terminating at a common flange36. First and second surfaces26,30have a common edge38and are substantially perpendicular to each other. The collective profile defined by first surface26and first recess28is a mirror image of the collective profile defined by second surface30and second recess32about a plane40(plane of symmetry) passing through common edge38that bisects angle39between first and second surfaces26,30. Preferably, first and second surfaces26,30are orthogonal, thus, angle39is ninety degrees and plane40is forty five degrees from each of first and second surfaces26,30.

To form a preferably rectangular raceway frame22using the raceways20, four mutually perpendicular, coplanar raceways20are interconnected end-to-end by corner members (not shown). By then interconnecting two opposed raceway frames22end-to-end using four raceways20, wherein the end of each raceway20is connected to a corresponding corner of each of the two raceway frames22, a rectangular framework is formed which defines a preferably rectangular structural framework for AHU10.FIG. 16shows two adjacent raceway frames22having a common raceway21that is common to each of the two raceway frames22. Each of the raceway frames22includes a phantom outline70,72, defining a peripheral recess that is provided to receive a respective insulated panel300therein. Thus, a typical rectangular structural framework, which defines six open raceway frames22, becomes an enclosed, interconnected framed panel structure upon receiving a respective insulated panel300in each of the peripheral recesses of the six raceway frames22. By virtue of the symmetry of raceway20, a single raceway profile may be used for each raceway20that is used to construct the structural framework for AHU10to provide identical, continuous peripheral seams or recesses for structurally securing each side of each insulated panel. While the above design for the raceway20is preferred, it is to be understood that any suitable design for raceway20can be used.

Secured to the inner surface of raceway20is a thermal barrier layer or material41. The thermal barrier layer41may be secured to the inner surface by an adhesive applied to the side of the thermal barrier layer41that is placed in contact with the inner surface, or by a tape or fasteners. In other words, any means may be used to secure the thermal barrier layer41to the inner surface of the raceway20that is compatible with foam material, such as injected foam material, and does not prevent operation of the thermal barrier layer41. Preferably, thermal barrier layer41has an uncompressed thickness from about 17 to about 20 mils (0.017 to 0.020 inches), although layers of reduced thickness, layers of increased thickness, and/or multiple layers of different thicknesses may also be used. It is also understood that the thickness of the layer may vary as installed, and/or the layer thickness may vary due to the compressive forces associated with installation, such as a high pressure foam injection process, as discussed in further detail below. The thermal conductivity of thermal barrier layer41is a function of thickness. The thermal barrier layer41can preferably be a plurality of non-woven ceramic fibers that form a lightweight, flexible sheet, e.g., is Nextel®, which is a registered trademark of 3M Company.

Preferably, the thermal barrier layer41is dimensionally stable over an extremely broad range of temperatures, and can withstand continuous temperatures of at least 2,200° F. without melting. It is also preferable that the fibers are non-respirable, and maintain their structural integrity and flexibility, even after the binders used during processing have worn off upon exposure to elevated temperatures.

While the thermal barrier layer41may be applied to the inner surface of the raceway20prior to forming the raceway20, alternately, the thermal barrier layer41may be preformed to a desired configuration, such as a sock, and slid into the closed geometry defined by the raceway20. In one embodiment, the thermal barrier layer41can span substantially the entire inner surface of the raceway20in order to meet particular flame and smoke index requirements. However, these requirements may also be achieved by affixing strip(s) of the thermal barrier layer41onto the inner surface of the raceway20, either prior or subsequent to forming the raceway20, partially covering the inner surface of the raceway20. In another embodiment, the remaining portion of the minor surface of the raceway20can be covered when either or both of the inner surfaces of the first and second surfaces26,30are at least partially covered. This is because the first and second surfaces26,30are the two primary surfaces exposed to the outside conditions once the raceway20is assembled to form the interconnected frame22.

Referring toFIG. 4, two adjacent raceway frames22each receiving the corresponding insulated panel300are shown, which raceway frame22has raceways20that are interconnected by corner members200. Common to each raceway frame22is the raceway20that is located at the common corner, which raceway being referred to as a common raceway21. One raceway frame22peripherally receives each of the four sides of the exterior skin316of its corresponding insulated panel300in second recess32formed in each raceway20. While the other raceway frame22also peripherally receives the four sides of the exterior skin316of its corresponding insulated panel300, two of the four sides of the exterior skin316are received in first recess28that is formed in two of the raceways20, and the remaining two sides of the exterior skin316are received in second recess32. Common raceway21(and each of the other vertically oriented raceways20) can simultaneously secure one side of each of two different insulated panels300, one side of insulated panel300being supported in first recess28, and one side of insulated panel300being supported in second recess32.

To increase the efficiency of the heating and cooling system, raceways20are injected with insulating material (not shown). Since the insulating material is preferably applied to substantially completely fill the interior of the raceways20, the formation of condensation is likewise significantly eliminated which is a major cause of corrosion for the raceways20, which are typically composed of metal, such as stainless steel or a galvanized coating applied to a steel alloy.

Referring toFIGS. 4-7, insulated panel300is provided for insertion in the first and/or second recesses28,32formed along the raceways20that are interconnected by corner members200to form framed structures22used with AHUs. Insulated panel300of the present invention is constructed using a minimum of parts and may be sized according to a customer's individual needs to define any number of different aspect ratios and dimensions, preferably down to at least one inch increments, while still complying with structural stiffness standards, assembled air leakage standards, and desired flame and smoke index requirements. Additionally, a single panel construction may be employed irrespective the location of the panel in the AHU. That is, ceiling, wall and floor panel constructions are the same.

Fixture302is preferably constructed of sheet metal, such as stainless steel, although other materials for use in HVAC systems that are sufficiently formable or moldable with sufficient strength and heat resistant properties may also be used. Fixture302comprises a centrally positioned base304having opposed risers306extending from sides of base304in a direction perpendicular to base304, which risers306further extend to outwardly (or inwardly) directed coplanar flanges308. A thermal barrier layer305is preferably similar or identical to the material previously discussed for use with the raceways20and is secured to base304. However, the thermal barrier layer305may extend to partially or totally cover any combination of risers306, flanges308and opposed end risers310and coplanar inwardly or outwardly extending end flanges313. When opposed risers306, flanges308, end risers310and end flanges313are rotated into a desired position, which opposed risers306and end risers313being substantially perpendicular to base304, the assembled fixture302resembles a rectangular block with an opening into the block due to the space between opposed flanges308and end flanges313. That is, if the opposed flanges308, and/or the opposed end flanges313extend inwardly, the opening in the assembled fixture302is defined by the space between the opposed flanges308and/or the opposed flanges313. However, if the opposed flanges308and/or the end flanges313extend outwardly, the opening in the assembled fixture302is defined by the space between the opposed risers306and opposed end risers310. As shown inFIG. 6, the opposed flanges308extend inwardly, while opposed end flanges313extend outwardly. A layer of foam tape312, such as polyethylene tape, having opposed adhesive layers314is applied along outside surfaces311,313of each respective flange308and end flange313for bonding fixture302to the exterior skin316. This foam tape312also has a low thermal conductivity, and serves as a thermal barrier to conduction. Alternately, other bonding methods or materials may be employed having similar physical properties.

Exterior skin316, which is preferably a substantially flat rectangular plate, includes a thermal barrier layer317. Although the thermal barrier layer317may have a rectangular shape that further includes an aspect ratio that is substantially similar to that of the exterior skin316, the thermal barrier layer317may have any geometric shape, and may further include apertures of any predetermined size, shape and pattern, or lack of a pattern, so long as the thermal barrier operates or functions as discussed below. The exterior skin316is then positioned over fixture302, the length of overhang318between the ends of the exterior skin316and the corresponding sides and ends of the fixture302preferably being substantially the same. Preferably, the thermal barrier layer317is both positioned along the exterior skin316and sized to fit within the footprint defined by the combination of the ends of the flange308, the riser ends313, the risers306and the end risers310of the fixture302, which defines the smallest surface area. In other words, the thermal barrier layer317is preferably substantially centered with respect to the exterior skin316and the fixture302. However, it may not be necessary to center the thermal barrier317within the footprint defined by the ends of the flange308, the riser ends310, the risers306and the end risers310of the fixture302on the inner surface of exterior skin316if the thermal barrier317can be configured into a tape that functions similar to tape312. In one embodiment, the thermal barrier layer317can be formed into a tape and have a size with substantially the same dimensions as the exterior skin316. That is, both the thermal barrier layer317and the exterior skin316can be cut simultaneously, saving manufacturing assembly time that might otherwise be expended centering the thermal barrier layer317on the inner surface of the exterior skin316. Alternately, the tape312may be applied to the thermal barrier material317, in which case the thermal barrier layer317can be sized to have substantially the same dimensions as the exterior skin316. Once the exterior skin316is bonded to the fixture302by virtue of the tape312or by the thermal barrier layer317, the assembled exterior skin316, tape312(or thermal barrier tape317) and fixture302collectively define a closed interior chamber320for receiving insulating material322therein.

The insulating material322, such as polyurethane foam, is injected by an injection gun (not shown) inside the chamber320through apertures (not shown) formed in the exterior skin316using a specially configured press to ensure the fixture302and the exterior skin316are sufficiently supported against the force of the insulating material322that is injected at an elevated pressure level. The volume of the chamber320is calculated prior to the injection operation. A precise amount of insulating material322is injected into the chamber320by correcting for the ambient conditions at the time of injection as it is desirable to completely fill the chamber320with insulating material322. Since the flow rate of the injected insulating material322through the injection gun is a known value, the duration of flow is the variable parameter which is precisely controlled to achieve the proper amount of injected insulation material322. To provide a favorable bonding interface between the inner surfaces of the chamber320and the expanding, injected insulating material322, the press platens that secure the exterior skin316and the fixture302may be heated, preferably up to about 100° F. for polyurethane foam material. Once the injection process is completed and the injected insulation material322has cured, the insulated panel300is installed in the AHU frame structure.

While desirable, it is not necessary for there to be a bonding interface between the inner surfaces of the chamber320and the expanding, injected insulating material322. This is because the injected insulating material322substantially fills the chamber320, providing significant rigidity that is sufficient for the insulated panels300to meet rigorous strength/deflection requirements. However, it may be possible to provide a combination of thermal barrier layers305,317having reduced sizes with respect to their corresponding inner surfaces such that both the desired flame and smoke index requirements and increased rigidity and strength are achieved. Alternately, any combination of thermal barrier layers305,317of various sizes, shapes and arrangements may further contain a plurality of apertures (not shown) formed in either or both of the thermal barrier layers305,317in either a patterned or non-patterned arrangement to also provide increased rigidity and structural strength while continuing to satisfy the desired flame and smoke index requirements.

Alternately, referring toFIG. 15, which is otherwise identical toFIG. 7except as shown, the insulated panel300incorporates a divider326that is secured in a substantially mutual parallel attitude with the fixture302and the panel316. The divider326substantially bisects the enclosed chamber320defined by the fixture302into two portions that are of substantially equal volume. Optionally, multiple dividers326may be used to further divide the enclosed chamber320into additional portions of reduced volume. Preferably, the divider326is a plate of substantially coplanar construction that may be secured in its position by spot welding the edges of the divider326to the corresponding portion of the inner surfaces of the riser306. Alternately, the divider326could include extensions (not shown) for insertion into apertures formed in the risers306, a set of grooves (not shown) formed in the inner surface of the riser306to receive the opposite ends of the divider326, adhesive, or any mechanical, chemical or electrical means to secure the divider326in its desired position prior to the injection of foam material. Preferably, the divider326incorporates a plurality of venting apertures (not shown) and/or in the fixture302or the panel316sufficient to substantially equalize the forces acting on the opposed surfaces of the divider326during the foam injection process. Since the divider326divides the enclosed chamber320into two smaller, substantially equal portions, the thickness of either of the portions being approximately one inch in a preferred embodiment, the problems associated with smoke generation may be significantly reduced. For example, if injected polyurethane foam is used, the panel300may then be able to meet the desired smoke generation index without the thermal barrier layer317. However, even if the panel300requires the thermal barrier layer317, it is believed that the thermal barrier layer317may be of significantly reduced size, (i.e., surface area) or thickness than previously required when used in panel300without the divider326.

Two separate tests, referred to as Experimental Run 1 and Experimental Run 2, respectively, were conducted in accordance with NFPA 90A per ASTM E84. For each test, three panels measuring 22⅞ inches wide by 22 feet 2¼ inches in total length were arranged horizontally with the three panels being joined end-to-end in the test furnace, simulating a ceiling installation in an AHU. The panels were conditioned in an atmosphere for 28 days at 70° F., 50% humidity prior to testing. The calibration material used to obtain zero index values for the flame spread and smoke indices was mineral fiber-reinforced cement board; red oak decks were used to obtain 100 index values for the flame spread and smoke indices.

FIG. 9shows a cross section of each of the three panels of Experimental Run 1. InFIG. 9, the thermal barrier305has a pair of opposed thermal barrier extensions319, which are not present in the thermal barrier layer41inFIG. 7. A single sheet or layer of each of the thermal barriers305,317having an uncompressed thickness of about 0.018 to about 0.020 inch were used in Experimental Run 1.

FIG. 10shows a cross section of each of the three panels of Experimental Run 2. InFIG. 10the thermal barrier317is overlaid by a thermal barrier328, the thermal barrier305is overlaid by a thermal barrier330and opposed thermal barrier extensions319are each overlaid by a pair of opposed thermal barrier extensions332. Each of the overlying thermal barrier layers was substantially the same size and thickness as its respective thermal barrier layer. Thus, double sheets or layers of each of the thermal barriers305,330and thermal barriers317,328each of about 0.018 to about 0.020 inch were used in Experimental Run 2.

FIGS. 11 and 12show the test results for the smoke index and the flame spread index, respectively, for Experimental Run 1by comparing red oak to the insulated panels over the duration of the testing (10 minutes), the insulated panels being identified as “Specimen”. Red oak represents both a smoke index and a flame spread index of 100, as previously discussed. The insulated panel produced more smoke than red oak, producing a higher level of light obscuration than red oak inFIG. 11. The smoke spread index based onFIG. 11was calculated and rounded to a value of 195. This calculated smoke spread index value was a notable improvement as compared to a value of 205 that was obtained for a similar insulated panel having no thermal barriers. In addition to the smoke spread index value reduction,FIG. 11shows that almost three and one-half minutes elapsed before a significant increase in light obscuration occurred. This was about a one minute improvement as compared to the test results for the insulated panel having no thermal barriers, or a percentage increase of about 40 percent. In practical terms, this notable improvement means that in a building fire, individuals attempting to flee the building may be provided additional time before significant smoke production and accumulation occurs, which improves the chances for escape. Additionally, the insulated panel produced significantly lower flame spread readings than red oak throughout the duration of the test inFIG. 12. The flame spread index based onFIG. 12was calculated and rounded to zero, which calculated index value was significantly less than the permissible index value of 25.

FIGS. 13 and 14, show the test results for the smoke index and the flame spread index, respectively, for Experimental Run 2 by comparing red oak to the insulated panels over the duration of the testing (10 minutes), the insulated panels being identified as “Specimen”. Red oak represents both a smoke index and a flame spread index of 100, as previously discussed. The insulated panel produced significantly less smoke than red oak over substantially the entire test duration, producing a consistently lower level of light obscuration than red oak inFIG. 13. The smoke spread index based onFIG. 13was calculated and rounded to a value of 5. This calculated smoke spread index value was significantly less than the desired index value of 50. In addition to the significant smoke spread index value reduction,FIG. 13shows that for the duration of the test, ten minutes, no significant increase in light obscuration occurred. This was at least about a seven and one-half minute improvement as compared to the test results for the insulated panel having no thermal barriers, or a significant percentage increase of about 400 percent. It is also possible that the improvement could have been significantly greater than about seven and one-half minutes because the test was halted after ten minutes, but prior to the occurrence of significant light obscuration due to smoke spread. In practical terms, this improvement means that in a building fire, individuals attempting to flee the building should be provided a markedly increased time before significant smoke production and accumulation occurs, which should likewise greatly improve the individuals' chances for escape from the building. Further, the insulated panel produced significantly lower flame spread readings than red oak throughout the duration of the test (10 minutes) inFIG. 14. The flame spread index based onFIG. 14was calculated and rounded to zero, which calculated index value was significantly less than the permissible index value of 25.

The test results for Experimental Run 1 indicate that the single thermal barrier layer317applied to the inner surface of the exterior skin316, and the single thermal barrier layer305applied to the inner surface of the fixture302of the insulated panel300provided notable smoke spread improvements over an insulated panel with no thermal barrier layers. Stated another way, Experimental Run 1 increased the amount of time by about 40 percent, i.e., about one minute, before significant smoke spread occurred due to the insulating material322being partially consumed by exposure to sufficiently elevated temperatures over an insulated panel with no thermal barrier layers. While the test results for Experimental Run 1 were notable, the smoke spread test results for Experimental Run 2 were significantly improved over Experimental Run 1.

To aid in analyzing the results, specifications of the insulating material used in the insulating panels in Experimental Runs 1 and 2 are provided below. In addition to the particular type of insulating foam material used for each of these tests, the particular geometry of the panels tested (the panel thickness being about 2 inches), corresponded to compressive forces of about 400 psi that were associated with injection of the foam. The insulating foam material had a density of about 2.2 pounds per cubic foot, a compressive strength measured in a direction perpendicular to rise (i.e., the direction of the panel thickness) of about 9 to about 13 psi, a modulus of about 220 to about 420 psi, and a shortened curing time since a heated fixture was used during the injection/curing process. With this combination of materials and conditions, the insulating material was designed to forcibly expand during the initial injection, exerting a high magnitude of compressive forces in all directions within the panel, but to discontinue application of the compressive forces during the curing process. That is, during the curing process, the forces associated with the injection and expansion of the foam material would essentially cease, but there would be substantially no shrinkage of the foam material. Stated another way, once the injection process was completed, the foam material substantially filled the closed interior chamber of the insulated panel.

In summary, the foam injection process subjected a high magnitude of compressive forces, approximately 400 psi, to the surfaces of the enclosed interior chamber and anything within the enclosed interior chamber. Upon completion of the injection process, the curing process followed, permitting substantially no shrinkage of the foam material. A resilient material, such as the thermal barrier layers305,317was probably compressed (its thickness reduced) during the injection process. The injection process was followed by the curing process, in which the foam material substantially retained the volume achieved during the injection process. Therefore, without shrinkage of the foam material during or after curing, the only remaining way for either of the resilient thermal barrier layers305,317to increase its thickness from its compressed thickness after the injection process, was for the reactive expansion forces in the thermal barrier layers305,317to exceed the compressive strength of the foam material. That is, the residual restorative forces within the thermal barrier layers305,317associated with the thermal barrier layers expanding to their original uncompressed thickness must be greater than the compressive strength of the foam material, or the thermal barrier layers would continue to be constrained to their compressed thickness.

As previously noted, the compressive strength perpendicular to the direction of rise (i.e., the thickness direction) for the foam material was from about 9 to about 13 psi. Therefore, it is highly likely that the thickness of each of the thermal barrier layers during the tests would be substantially the same as their compressed thickness. Thus, it is believed that the thermally insulative properties of the thermal barrier layers are dependent on the thickness of the thermal barrier layers when tested. Yet, despite the believed reduction in thermal performance, the insulated panel construction, which included thermal barrier layers, provided a notable improvement over an insulated panel construction that lacked the thermal barrier layers.

Test results also appear to clearly indicate in Experimental Run 2 that a desired smoke spread index value can be achieved by adding a second thermal barrier layer328over the thermal barrier layer317that was secured to the exterior skin316. The stacking of two thermal barrier layers317,328, despite the layers being compressed during the injection process as previously discussed, provides sufficient additive thermal performance, possibly due to the effective thickness of compressed thermal barrier material layers317,328after the foam has been injected. In an alternate embodiment of insulated panel300, thermal barrier layers305,330as well as thermal barrier layer extensions319,332are removed, thus leaving thermal barrier layers317,328. However, it is believed that the sizes of thermal barrier layers317,328may be reduced in size, and even have apertures formed therein while still achieving desired smoke and flame indexes.

In addition to permitting the insulated panels300to satisfy the desired flame and smoke index requirements, the thermal barrier layers317,328, and alternately, thermal barrier layer305, possibly including thermal barrier extensions319or further possibly including respective overlying layers330and/or thermal barrier extension layers332, may also provide improved acoustic attenuation performance. The insulated panels300without the thermal barrier layer may have a significant coincidence effect, which occurs at its critical frequency. Coincidence is defined as a significant reduction in sound transmission loss (i.e., a significant increase in the transmission of sound) through a partition that occurs at critical frequency. The critical frequency is the frequency at which the wavelength of sound in air equals the flexural bending wavelength in the partition or material. Stated another way, coincidence occurs when the wavelength of sound in air, projected on the plane of the panel300, matches the bending wavelength of the panel300. Coincidence is typically limited to flat panels. At coincidence, the panel300may be substantially transparent to sound at certain frequencies, such as about 1,000 Hz although panel thickness, aspect ratio and other factors may significantly change this frequency. Internal damping, if any, may help control the insertion loss. Without dampening, the insulating material322is tightly bonded to the inner surfaces of the fixture302and the exterior skin316, the insulated panel300acting as a homogenous plate. That is, the insulating material322bonds the fixture302and the exterior skin316tightly together so that they move as one plate.

Any combination of the thermal barrier layers305,317and thermal barrier extensions319may provide some dampening of the coincidence reduction at about 1,000 Hz, or other frequencies at which coincidence reduction occurs. Where the thermal barrier layers305,317and/or thermal barrier extensions319are not be sized to substantially match the size of its corresponding fixture302or exterior skin316, or have apertures formed in the thermal barrier layers305,317, as previously discussed, the corresponding bond between the thermal barrier layer305,317and/or thermal barrier extensions319and its corresponding fixture302or exterior skin316is reduced. Due to this reduced bond, it is believed that the insulated panel300will no longer move as one plate. By no longer moving as one plate, coincidence of the panel300is reduced, thereby improving acoustic performance.

Referring toFIG. 19, acoustic tests were performed for three different panel constructions over a range of eight octave band frequencies. An octave band is a defined as a range of frequencies where the highest frequency of the band is twice that of the lowest frequency. For example the 125 Hz octave band represents the range of frequencies from 88.5 Hz to 177 Hz, 177 Hz being twice that of 88.5 Hz. The center frequency of each octave band listed along the x-axis ofFIG. 19is defined by the following equation:
fc=sqrt(f1×f2)  [1]
f1is the lowest band frequency and f2is the highest frequency of the octave band. Applying equation [1] to the above-referenced octave band values yields the 125 Hz center frequency value. The first panel was of conventional construction, having no thermal barrier layers (TBLs). The second panel had two layers of thermal barrier material applied to one inside surface of the panel, such as thermal barrier layer317inFIG. 7. The third panel was similar to the second panel, except the third panel also had two layers of thermal barrier material applied to a second inside surface of the panel, such as thermal barrier layer305inFIG. 7.

As shown inFIG. 19, adding the thermal barrier layers significantly increased the amount of sound power insertion loss normally associated with the coincident frequency for the flat panels, which was about 1,000 Hz. For example, the second panel showed greater than a 14 percent increase in sound power insertion loss over the first panel at the coincident frequency. Similarly, the third panel showed about a 42 percent increase in sound power insertion loss over the first panel. Therefore, test results indicate the effects of coincidence can be significantly mitigated by the use of the thermal barrier layers of the present invention.

Referring toFIG. 8, insulated roof assembly400provides a sloped roof surface for use with AHU structures of the present invention to prevent the formation and accumulation of standing water on the top of the AHU structures which are installed outside and subjected to the rigors of environmental exposure, such as rain or snow. Insulated roof assembly400is preferably of unitary construction comprising two sloped halves402abutting along the mid span404of the roofline, typically referred to as the peak of the roof. Each sloped half402includes a fixture406and an exterior skin408, similar to that previously discussed for insulating panel300. Similar to insulated panel300, roof assembly400defines a closed chamber410for receiving injected insulating material412therein. That is, upon assembling fixture406to exterior skin408, the collective interfacing surfaces including sloped surfaces415and flanges428of exterior skin408, and a base407, ends418, and flanges426of fixture406define closed chamber410. For similar reasons of additional stiffness and strength, as well as enhanced insulating properties for insulated panel300, insulating material412is injected inside closed chamber410of roof assembly400in a manner substantially similar to that previously discussed for insulating panel300.

Also, similar to the insulated panel300, the roof assembly400can include any combination of thermal barrier layers430,432. The thermal barrier layer430is preferably applied to the inner surface of the exterior skin408, and thermal barrier layer432is preferably applied to the inner surface of the base407. It is also to be understood that either or both of the thermal barrier layers430,432may extend to at least partially cover the inner surface of other portions of the fixture406and the exterior skin408of the roof assembly400, such as the flanges428, the ends418, or any other portion of the roof assembly400having an exposed inner surface inside the roof assembly400.

Aside from enabling foam-filled AHU structural components to meet the desired flame and smoke index requirements, the thermal barrier layer may be similarly used with gas, steam, and electrical heat components. These components include but are not limited to, freezer panels in appliances, such as refrigerators and freezers, commercial freezers, both enclosed and open units (such as those in supermarkets), any plumbing associated with any of the above, fire doors and the like, especially those using insulating foam material. However, as will be discussed in greater detail below, at least some of these components, such as drain pans, which may have no insulating foam material, can make advantageous use of the thermal barrier layer.

Despite its minimal thickness, the thermal barrier layer has the ability to maintain a significant temperature differential between its opposite surfaces, especially when one side is subjected to high temperature. That is, if one side of the thermal barrier layer is subjected to an elevated temperature of about 1,100° F., for example, the opposite surface of the thermal barrier layer is maintained at a temperature of approximately 650° F., resulting in a temperature differential of about 450° F. If multiple thermal barrier layers are stacked, then the temperature differential between the surface of the first thermal barrier layer that is subjected to the high temperature, and the opposite surface of the stacked thermal barrier layer that is furthest from the first thermal barrier layer, is greater than the temperature differential between opposite surfaces of the single thermal barrier layer.

At other temperatures, a temperature differential of about 440° F. results between opposite surfaces of a single thermal barrier layer when the one surface is subjected to an elevated temperature of about 750° F., and a temperature differential of about 230° F. results between opposite surfaces of a single thermal barrier layer when the one surface is subjected to an elevated temperature of about 400° F. Therefore, over a broad temperature range, the thermal barrier layer reduces heat transmission by about 35 percent to about 45 percent.

In other words, even in the absence of insulating foam, where used, the thermal barrier layer operates to help moderate and thereby protect components exposed to elevated or reduced temperature environments. In elevated temperature environments, the thermal barrier layer is interposed between the elevated temperature environment and components that are to be protected from the elevated temperature environment. The thermal barrier layer is intended to minimize the temperature of the surface facing the protected components, which reduces both the flame spread and the smoke spread of the protected components. Similarly, in reduced temperature environments, such as those associated with refrigeration cycles, the thermal barrier layer is interposed between a reduced temperature environment and components that are to be protected from the reduced temperature environment. The thermal barrier layer may maximize the temperature of the surface facing the protected components.

Among the possible benefits of the thermal barrier layer maximizing the temperature of the surface facing the protected components, in addition to efficiency of operation of HVAC systems, is the substantial reduction, if not prevention, of condensation that collects on HVAC component surfaces. Condensation is defined as the conversion of a substance (i.e., water) from the vapor state to a denser liquid or solid state usually initiated by a reduction in temperature of the vapor. Due to the reduced temperatures of the surfaces of HVAC components, ambient air passing in contact with these components are likewise cooled, which reduces the ability of the air to retain moisture (water), resulting in the formation of condensation on these surfaces. The amount of water formed by condensation can be significant, often requiring systems or techniques for removal, at increased cost to the user. Additionally, condensation is a source of corrosion of metallic components, and if the condensation collects beneath a HVAC unit, such condensation may be the source of structural damage.

To minimize condensation, the thermal barrier layer may be protectively secured or applied to or adjacent to the inner surface of the HVAC component, such as a drain pan, such that the thermal barrier layer is not directly exposed to the operations associated with the surface of the HVAC component to prevent possible contamination from or damage to the thermal barrier layer. Alternately, the thermal barrier layer may be disposed within the HVAC component during its manufacture.

For example,FIGS. 17-18illustrate an embodiment of an insulated panel500, which is otherwise the same as insulated panel300as previously discussed, but is specifically configured for use as a floor panel in the AHU10. In other words, the insulated panel500not only performs the same functions as the insulated panel300, but the insulated panel500is also specially configured to provide a drain pan for collecting and removing condensation that collects on its outer surface512. The condensation collected by the insulated panel500initially forms on cooling coils (not shown) that are positioned within the AHU10above the insulated panel500. During operation of the cooling coils, air passing along the cooling coils is cooled sufficiently to lose its ability to retain moisture, the moisture (condensation) being deposited as droplets on the surface of the cooling coils. The condensation continues to accumulate on the surface of the cooling coils, and once the droplets combine to reach a sufficient size, due to gravity, the condensate droplets fall from the surface of the cooling coils, and accumulate upon the outer surface of the insulated panel500.

To facilitate the collection and removal of this condensation from the insulated panel500, the outer surface512of the sheet metal fixture502is provided with a first sloped portion503and a second sloped portion505. The first sloped portion503and the second sloped portion505are formed during the manufacture of the insulated panel500, such as by a narrow blade550that is brought into deforming contact with the fixture502as the blade550travels in a direction552. For reference, an undeformed profile501or outline of the fixture502is provided. While it may be preferable for the first and second sloped portions503,505to be formed prior to injection of insulating material, it may also be possible to form the first and second sloped portions503,505after the injection process.

The first sloped portion503includes a proximate half of the outer surface512of the fixture502, and the second sloped portion505includes the remaining distal half of the outer surface512of the fixture502. Each of the first and second sloped portions503,505are represented as substantially V-groove profiles, although other profiles may also be used. The first sloped portion503begins with a proximal V groove518and transitions to and terminates at a midspan V groove528. A base504, which defines the base of the V groove contour formed in the first sloped portion503, connects the base of the proximal V groove518to the base of the V groove528. The second sloped portion505begins with the midspan V groove528and transitions to and terminates at a distal V groove538. A base506, which defines the base of the V groove contour formed in the second sloped portion505, connects the base of the midspan V groove528to the base of the distal V groove538.

The proximal V groove518is preferably defined by a pair of opposed proximal corners510that are connected at a proximal corner point508. The proximal corner point508is positioned at a depth of “D1” below the undeflected panel profile501, which depth D1preferably being about one-fourth of an inch. At a predetermined distance “L1” as measured along the undeflected panel profile501, which is substantially in the direction of the base504, is a center point507that is preferably positioned at the center of the undeflected panel profile501of the fixture502. Thus, L1is preferably one-half of the distance “L2” which is the length of the groove as measured along the undeflected profile501. The center point507is preferably positioned at a depth of “D2” below the undeflected panel profile501, which depth D2preferably being about one-half inch. To trace the midspan V groove528, the base of the midspan groove528, which is defined by the center point507, connects opposed midspan edges520. The midspan edges520are coincident with the outer surface512.

The first sloped portion503is defined on its proximal end by the proximal V groove518, the proximal corners510of the proximal V groove518coinciding with the outer surface512. Thus, while proceeding distally along base504toward the midspan V groove528of the fixture502from the proximal V groove518, the proximal corners510of the proximal V groove518, which transition to the midspan edges520of the midspan V groove528, remain coincident with the outer surface512. Stated another way, the surface of the first sloped portion503coincides with the proximal half of the outer surface512. It is noted that the slope of the base504of the transitioning V grooves corresponding to the first sloped portion503may be determined by calculating the difference between the center point507and the proximal corner point508(D2-D1) divided by L1.

The second sloped portion505transitions uninterrupted from the first sloped portion503since the second sloped portion505is defined on its proximal end by the midspan V groove528, which coincides with the distal end of the first sloped portion503. Similar to the first sloped portion503, the second sloped portion505continues to coincide with the distal half of the outer surface512. In other words, while proceeding distally along base506toward the distal V groove538of the fixture502from the midspan V groove528, the midspan edges520of the midspan V groove528, which transition to the distal corners530of the distal V groove538, remain coincident with the outer surface512. Stated another way, the surface of the second sloped portion505coincides with the distal half of the outer surface512. The distal V groove538is defined by a pair of opposed distal corners530which are joined at the base of the V groove538at a distal corner point509. The distal corner point509is positioned a distance “D3” below the undeflected surface501, which depth D3preferably being about one and one-half inch. Thus, the base of the transitioning V grooves for the second sloped portion505can be traced along the base506between the center point507and the distal corner point509. It is noted that the slope of the base506of the transitioning V grooves corresponding to the second sloped portion505may be determined by calculating the difference between the center point507and the distal corner point509(D3-D2) divided by the difference between L2and L1(L2-L1). The increase slope506provides for improved removal of condensation from the outer surface512of the fixture502.

In operation, condensation falling onto the sloped outer surface512of the fixture502of the insulated panel500will be urged, by force of gravity, to proceed along the V grooves defined by the first and second sloped portions503,505. Upon passing the distal corner point509of the fixture502, the condensation passes through a passage formed in a raceway (not shown) to exit the AHU10.

While the concept of forming a two-tiered V groove in the insulated panel500eliminates additional components, the significant depth of distal corner point509as compared to the total thickness of the insulated panel500, identified as “THK”, which is typically about 2 inches for an undeflected panel profile in a preferred embodiment, leaves only about one-half inch of remaining thickness adjacent the distal end of the distal half of the panel. This reduced thickness means there is likewise less insulating material522at the distal region of the insulated panel500to insulate the lower surface of the exterior skin516. Without sufficient insulation, the lower surface of the exterior skin516, which is the surface of exterior skin516that faces in a direction away from the fixture502, may drop to a temperature that will cause condensation to form along the lower surface of the exterior skin516. This condensation, which flows from beneath the AHU, is unattractive, may promote the growth of mold, may provide a slipping hazard, and may promote corrosion of the AHU.

To substantially reduce, if not prevent, condensation from forming along the lower surface of the exterior skin516, a thermal barrier layer517may be secured to the inner surface of the fixture502. In this application, the thermal barrier layer517maintains a sufficient temperature differential between the surface of the thermal barrier layer517facing the outer surface512of the fixture502and the opposite surface of the thermal barrier layer517such that condensation is substantially prevented from forming along the lower surface of the insulated panel500.

One skilled in the art can appreciate that the thermal barrier layer may also be protectively secured or applied to or adjacent to the outer surface of the HVAC component or anywhere within the casing or housing of the HVAC component so long as the thermal barrier layer functions to sufficiently raise the surface temperature of the HVAC component surface exposed to surrounding ambient conditions to substantially minimize, if not prevent, the formation of condensation on the surface of the HVAC component. HVAC components include, but are not intended to be limited to ducting, drains, drain pans, or any associated components having a reduced surface temperature. Further, this invention is not limited to HVAC components, and is contemplated to include components on which condensation forms, such as plumbing or containers that hold substances of reduced temperature, the reduced temperature not being the result of an HVAC system, such as water collection from a source having a reduced temperature.

It is further appreciated that any foam-filled enclosed container for use in the construction of walls or partitions for residential or commercial structures can incorporate the thermal barrier layer of the present invention.

Additionally, the thermal barrier layer of the present invention may be used with household appliances, walk-in coolers, refrigerated display cases and HVAC units.