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Open Ceiling Containing Phase Change Material

This invention relates to an open ceiling system which contains phase change materials ("PCMs") for controlling the climate, particularly the temperature, in rooms or other spaces of a building.

Controlling the climate in buildings to maintain comfortable levels has traditionally been effectuated by air conditioning systems providing heated or cooled, recirculated air. These systems have high energy costs to operate, and they need effective filtering mechanisms to avoid creating a "sick building" syndrome.

Other climate control systems have used metal ceiling panels, in which circuits of closed ducts that contain heated or cooled water or glycol are placed on or in the panels atop a false ceiling. Depending on the temperature of the medium running through these ducts, these ducted systems either heat or cool the underlying spaces or plenums in their buildings. In case of cooling, such a system drops a "blanket' of cold (but still-standing) air into the underlying plenums or absorbs heat radiated upwardly by the underlying plenums. Such ducted ceiling systems require highly heat-conductive components and duct circuits that are 100% water-tight. Also, relatively sophisticated control systems are needed to make such ducted systems work. Moreover, these ducted systems are difficult to install because of their inherent complexity.

Alternatively, the use of PCMs in ventilated or open ceilings has been proposed to overcome the problems associated with air conditioning systems and ducted ceiling systems.

WO 01/38810 describes one such ceiling system in which steel or aluminum cells containing PCMs are hung from the structural ceiling of a building within a space or room. The PCM-containing cells can be installed horizontally as a false (or lower) ceiling and thereby serve as ceiling tiles, or the cells can be hung vertically

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as baffles. The melting temperature of the PCMs is between 20 and 25 C. Although natural ventilation can be used, a supply air fan and an exhaust air fan are installed on an outer wall of the room (or the facade of the building). In daytime, excess heat is absorbed by the PCMs in the cells without the need for extra ventilation beyond the fresh air requirements of the room. At night, cold outside air is directed at the space between the cells and the structural ceiling by the supply air fan. The exhaust air fan is used suck out air heated by the PCM- containing cells. The supply and exhaust fans are used to increase the convection heat-transfer coefficient of the cells' surfaces and enhance the heat discharge of the cells.

Similarly, WO 03/102484 describes a ceiling system for a room with an air inlet and an air outlet for natural ventilation and two horizontal planes of PCM- containing bodies, hung one above the other from the structural ceiling of the building. The air inlet is in the same plane as the PCM-containing bodies, so that the air will flow along the bodies. In this system, additional heating and cooling devices must be placed inside the room to meet the total energy (heating/cooling) demand of the room which cannot be entirely met by the PCM- containing bodies.

Likewise, WO 03/102484 describes a ceiling system for a room with PCM- containing bodies, conventional elements for heating and cooling air before it is blown over the bodies, and a heat exchanger. The design of this system will normally be such that the PCM-containing bodies will take care of at most about 50% of the heating or cooling requirements of the room.

In addition, EP 1 371 915 describes a conventional system of closed (or cassette) metal ceiling panels, on which are provided relatively small, sealed bags or pouches of PCMs. Thereby, the PCMs absorb heat from the space below the panels to provide a cooling blanket during the day. However, a so-

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called climate or chilled air conditioning system is needed to enhance the performance of the PCMs in order to provide sufficient cooling of a room.

Accordingly it is an object of this invention to overcome or ameliorate the disadvantages of the ceiling systems of WO01/38810, WO03102484 and EP 1 371915 and, where possible, to provide a ceiling system with a sufficient quantity of PCMs and sufficient heat transfer surfaces to control passively the climate of a room equipped with such a system .

To this end, the invention provides an open ceiling system with integrated PCMs for conditioning the climate in an underlying space in a building with the PCMs and, where practical, using ambient air for melting and regenerating the PCMs. This system includes: a horizontally-extending carrying structure; a lower layer of horizontally-extending parallel elongated lower ceiling panels attached to the carrying structure with open linear gaps or slots extending vertically and along the length of each lower ceiling panel between adjacent lower ceiling panels; the lower ceiling panels collectively defining an upper plenum in the building above the underlying space and a lower plenum in the underlying space; PCMs on the lower ceiling panels; and means for providing an air pressure difference between the upper and lower plenums.

The invention thus can be used to solve the problems of using PCMs in existing ceiling systems by allowing for passive climate control of such systems without the need for additional air conditioning or forced air systems. The invention thereby can optimize heat transfer, acoustical performance and installation/demounting procedures. In this regard, The vertically-extending linear gaps or slots, between the lower ceiling panels, can provide:

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maximum energy transfer, particularly heat transfer, between the PCMs on the panels and air moving between the upper and lower plenums; maximum ventilation of the plenums; and enhanced sound absorption.

According to one aspect of the invention, the profile of the lower ceiling panels allows them to be installed on carriers that run transversely to the length of the panels with ventilating gaps between the panels in a so-called linear ventilated ceiling configuration. Thereby, the lower ceiling panels profile allows air to flow directly over the PCMs on the panels.

According to another aspect of the invention, energy transfer to and from the PCMs on the lower ceiling panels is further enhanced by providing the PCMs in one or more elongated pouches on each panel, so that the pouches are surrounded or enclosed in the cross-sectional widthwise profile of the panel. Advantageously, such energy transfer can be still further enhanced by increasing the width and the height of the lower ceiling panels to maximize their surface areas exposed to air moving between the upper and lower plenums due to any difference in air pressure between the upper and lower plenums and by increasing the width and the height of the PCMs which contact the width and the height of the panels. Also advantageously, the lower ceiling panels can have an internal U-shaped reinforcing profile and the PCM pouches can be provided between the ceiling panels and their internal U-shaped profiles to increase the panel surface exposed to air moving between the upper and lower plenums and absorbing heat from the underlying space.

According to still another aspect of the invention, the total PCM load of the ceiling system can be increased (e.g., doubled) by having a multi-layer linear ceiling system. Advantageously, the lower layer is adjacent to the underlying plenum or space (e.g., room), to be cooled and/or heated, and has a first percentage of

openness in the gaps between adjacent lower ceiling panels which should be at least 5% but no more than 30%, especially 10 to 25 %, particularly 15 to 20%. Also advantageously, the lower layer carries 2 to 20 kg of PCMs per square meter of structural ceiling surface, especially 5 to 15 kg/m ² , particularly 8 to 12 kg/m ² .

According to yet another aspect of the invention, the ceiling system has at least another, e.g., upper, layer of horizontally-extending linear ceiling panels which is above the lower layer of ceiling panels and on which are PCMs. Advantageously, the upper layer is mounted atop the carrying structure holding the lower layer of ceiling panels to provide additional PCMs and additional heat transfer surfaces with no additional carrying structure. Also advantageously, the upper ceiling panels of the upper layer extend transversely to the lower ceiling panels of the lower layer. Further advantageously, the upper ceiling panels are of equal or lesser width than the lower ceiling panels. Still further advantageously, the upper layer has an openness that is equal to, or greater than, the openness of the lower layer. Yet further advantageously, if the upper and lower ceiling panels extend in the same direction, the gaps between adjacent upper ceiling panels are slightly off-set relative to the gaps between adjacent lower ceiling panels, so that air flow, and hence heat transfer, between the layers is enhanced.

According to another aspect of the invention, the ceiling system has at least a third, e.g., top, layer of ceiling panels which is above the lower and upper layers of ceiling panels and on which are PCMs. Advantageously, the top ceiling panels of the top layer are vertically-extending baffled panels containing PCMs. Also advantageously, the top ceiling panels are mounted on the top of the upper plenum, on a building's structural ceiling.

According to a further aspect of the invention, PCM pouches on the lower layer of ceiling panels and on the optional upper layer of ceiling panels are of limited thickness (or height when placed flat atop the ceiling panels). Advantageously,

the thickness of the PCM pouches used on the ceiling panels of the lower and upper layers is no more than 20 mm and no less than 2 mm, especially 5 to 15 mm, particularly 8 to 12 mm.

The invention will be further described by reference to the accompanying drawings, in which:

- Figure 1 is a schematic cross-section of a ceiling system of the invention, viewed along the length of its ceiling panels containing PCMs;

- Figure 2 is a schematic partial cross-section of a first embodiment of the ceiling system of Figure 1 , viewed transversely of the length of the horizontally-extending linear ceiling panels of its lower layer of panels; different panels with different loads of PCMs are shown;

- Figure 3 is a partial perspective view of the lower ceiling panels of Figure 2;

- Figure 4 is a perspective view of the lower ceiling panels of Figure 2, from which the PCMs have been deleted for clarity; and

- Figure 5 is a perspective view of a second embodiment of the ceiling system of Figure 1 , with upper and lower layers of ceiling panels; and

- Figure 6 a cross-sectional view of a third embodiment of the ceiling system of Figure 1 , with three layers of ceiling panels.

Figure 1 shows a building's structural ceiling 1 holding a ventilated or open ceiling system, generally 2, beneath it. A ventilation opening 3 is provided adjacent the structural ceiling 1 in an upper plenum 7 over a lower or false, linear ceiling 9 of the ceiling system 2. The linear ceiling 9 covers a lower plenum 8 which can be a room or other space in the building. The linear ceiling 9 is suspended from the structural ceiling 1 by vertically-extending connector rods 11 which hold horizontally-extending profiled metal stringers or panel carriers 13. A plurality of horizontally-extending, parallel elongated linear ceiling panels 15 are attached in a conventional manner to the stringers 13 with open linear gaps or slots (not shown) extending vertically and along the length of each panel 15

between adjacent panels. Each panel 15 holds a quantity of PCMs 17 as described below. The panels 15 are preferably made of metal, especially aluminum or steel. The linear Luxalon ® ceiling panels of Hunter Douglas are particularly well suited for carrying the PCMs 17, contained in plastic pouches. For example, pouches containing suitable PCMs with different specific temperature ranges are commercially available in different sizes, e.g., from Climator AB of Skovde, Sweden under the trademark ClimSel.

The ceiling system 2 of this invention can use a passive system - without air conditioning - to control the climate, particularly the temperature, in the lower plenum 8 of a building's space. In this regard, the ventilation opening 3, which could be located in the building's fagade, allows ambient outside air 5 to be led, day and/or night, into the upper plenum 7 to regenerate PCMs 17 on the ceiling 9 that melt, in use, during the day. Alternatively, open windows in the lower plenum 8 at night can be used to allow cool ambient outside air 5 to be led (through the gaps between the ceiling panels) into the upper plenum 7 to regenerate PCMs 17 on the ceiling 9 that have melted during the day.

However, if desired, ambient outside air, or even cooled air conditioned air, can be "force ventilated" in a conventional manner (e.g., with fans or pumps) into the upper plenum 7, then through the gaps between the ceiling panels, and then into the lower plenum 8. In this regard, forced air ventilation systems are standard in most large buildings such as office buildings, public buildings, airport terminals and the like in order to provide a minimum number of total air-body regeneration cycles per 24 hours. The number of such cycles is often prescribed in order to prevent the 'sick building' syndrome. When a certain PCM load in a building has to be regenerated, the number of air regeneration cycles can be increased during the night.

In order to have sufficient heat transfer capacity for a room or other space in a lower plenum 8 beneath the ceiling 9 without excess weight bearing on the

ceiling, a total of 10 to 30 kg of PCMs per square meter of the surface of the ceiling 9 (or the underlying floor surface of the lower plenum) are generally used on the ceiling 9, preferably a total of 15 to 25 kg/m ² .

Figures 2 to 4 show schematically a first embodiment 109 of a linear ceiling which can be used as the linear ceiling 9 of Figure 1 and for which corresponding reference numerals (greater by 100) are used below for describing the same parts or corresponding parts.

As seen from Figure 2, the linear ceiling 109 is formed by a plurality of horizontally-extending parallel elongated linear ceiling panels 115A, 115B, 115C and 115D. These ceiling panels are held by conventional horizontally-extending multi-panel stringers 113 above the panels. Open linear gaps 114 extend vertically and along the length of each panel 115A-115D between adjacent panels as mounted on the stringers 113. Each panel 115A-115D has a generally U-shaped cross-section with a pair of inturned flanges 119 and 121 at its open top for cooperation with flanges 123 on the stringers 113. Within the generally U- shaped cross-section of each panel are PCMs, generally 117, preferably sealed in plastic pouches. The linear ceiling 109 is well adapted to support the required load of PCMs 117 and provide a sufficient degree of openness for needed air flow around the surfaces of the panels and the PCMs. If desired, the stringers 113 can be strengthened and enlarged , e.g., at 113A, to hold more or heavier panels, e.g., 117A, and/or loads of PCMs, e.g., 117A.

The left most ceiling panel 115A in Figure 2 is provided with an inner U-shaped profile 125 that is separately attached to the stringer 113. The inner profile 125 has an outer cross-sectional shape that corresponds to, but is spaced inwardly of, the inner cross-sectional shape of the ceiling panel 115A. This forms an intermediate U-shaped space 127 between the ceiling panel 115A and its inner profile 125. As a result, PCMs 117A can be provided in a generally U-shaped form in the panel 115A, to cover its bottom surface 133 and its left and right

upstanding walls 135, 137 and the outer surface of the internal profile 125. This allows the use of PCMs 117A of a relatively small thickness of approximately 15 mm. The U-shaped space 127 also allows the PCMs to have additional heat transfer surfaces on the panel 115A and allows for extra air flow through this panel for proper temperature control of a lower plenum 8, even without "forced air" ventilation .

Representative dimensions of a linear ceiling 109 provided with only ceiling panels like the left most ceiling panel 115A of Figure 2 (with the inner profile 125) are as follows:

- Panel 115A height : 39 mm,

- Panel 115A width: 30mm,

- Width of gap 114 (between panels): approximately 20 mm.

- Linear ceiling 109 surface: approximately 40% open relative to structural ceiling surface.

- Internal profile 125 height : 28mm,

- Internal profile 125 width: 10mm,

- Thickness of U-shaped PCMs 117A: 10 mm, and

- PCM load: approximately: 8 kg/m2

The ceiling panel 115B, adjacent the left most ceiling panel 115A, has the same cross-sectional shape and size as the left most ceiling panel 115A but no internal U-shaped profile. As a result, its load of PCMs 117B has a generally U-shaped form and covers the bottom surface 133B of the ceiling panel 115B and its left and right upstanding walls 135B, 137B. The advantage of this embodiment is that there is no additional profile needed, while still providing added surface area and air flow. However, it is believed that the PCMs 117B, when heated and melted, will not retain the U-shape by themselves unless produced in such a form. A linear ceiling 109 provided with only ceiling panels like the ceiling panel 115B could have the same dimensions, gap width 114 and PCM load as a ceiling 109 with only ceiling panels like the left most ceiling panel 115A.

The next adjacent ceiling panel 115C is provided with an unshaped PCM load 117C. The PCMs 117C mainly cover the bottom 133C of the ceiling panel 115C and a portion of the height of its left and right side walls 135C and 137C. A linear ceiling 109 provided with only ceiling panels like the ceiling panel 115C could have the same dimensions and widths of gaps 114 as a ceiling 109 with only ceiling panels like the left most ceiling panel 115A and could have a PCM load of approximately 8 kg /m2 and a thickness of PCMs of approximately 15mm.

The right most ceiling panel 115D shown in figure 2 is loaded with double the amount of PCMs 117D loaded on the adjacent panel 115C ₁ i.e. approximately 16 kg/m2. Although the additional PCMs will provide the panel 115D with a greater cooling capacity, the cooling capacity will not be double that of the adjacent ceiling panel 115C. This is caused by the diminished air flow capacity of the right most panel 115D as its load of PCMs take up space that cannot be used for air flow. Also the thicker load of PCMs of approximately 30 mm of the right most panel 115D is less efficient in its heat transfer capabilities since it conduction of the heat to the center of the PCM-load will take more time. Also in thicker PCM loads, the constituents of the mixture of PCMs can separate under the influence of gravity. The risk of this separation increases after a few hundred freeze-thaw cycles, which in case of a ceiling in a building would indicate a risk of lesser "cooling" performance within a year or so from its installation.

Figure 4 shows ceiling panels 115E, 115F, 115G, 115H, 1151 of different widths and heights which can be used in the PCM-loaded linear ceiling 109 of Figures 2 and 3. (PCMs are not shown in Figure 4.) The left most panel 115E in Figure 4 has the same dimensions as the panels 115A-D in Figures 2 and 3. The adjacent second panel 115F is of lesser height and preferably is 30mm wide and 15mm high. The other three panels 115G, 115H, 1151 have progressively increasing widths but the same height as the second panel 115F. All these panels 115E, 115F, 115G, 115H, 1151 are well known and used commercially in both ventilated

and closed, linear ceilings. Shown above the ceiling panels of Figure 4 is one of the stringers 113, holding the panels with gaps 1 14 between them, and one of the connector rods 111 , holding the stringer on a building's structural ceiling by means of a conventional clip 112.

Of course, the wider the ceiling panels 115G-115I, the less the degree of openness of i) the gaps 114 between the panels and ii) the ceiling 109 as a whole. On the other hand, wide and relatively low ceiling panels provide flat PCM layers 117A-117D, which is beneficial to the heat transfer properties of the ceiling 109.

Figure 5 shows a second embodiment 309 of a linear ceiling which can be used in place of the linear ceiling 109 of Figures 2-4 and for which corresponding reference numerals (greater by 200) are used below for describing the same parts or corresponding parts.

The ceiling 309 has a lower first layer 309A of horizontally-extending parallel elongated linear ceiling panels 315K and an upper second layer 309B of horizontally-extending parallel elongated linear ceiling panels 315L. The lower layer 309A is held by horizontally-extending stringers 313, mounted on vertically- extending connector rods 311 , attached to a building's structural ceiling (not shown). The upper second layer 309B is mounted atop the stringers 313 and its ceiling panels 315L extend transversely to the ceiling panels 315K of the lower first layer.

Each of the lower ceiling panels 315K of the lower layer 309A has a generally U- shaped cross-section and intumed flanges 319 (not visible in Figure 5) and 321 at its open top for cooperation with flanges 323 on the stringers 313. The stringers 313 hold adjacent lower ceiling panels 315K apart with a gap 314A between them, so that the lower first layer 309A has approximately 7.5% openness. Preferably, as shown in Figure 5, the lower ceiling panels 315K are

wide, e.g. 185 mm, but have little height, e.g., 25mm. Several pouches of PCMs 317A are stacked within the U-shaped cross-section of each of the lower ceiling panels 315K. Each pouch preferably is approximately 300 mm long, 80 mm wide and 8 mm high and contains approximately 300gr of PCMs 317A . Approximately 6 or 7 PCM-containing pouches can be stacked per linear meter of each lower panel 315K which means a total PCM load of the lower first layer 309A (with its openness of 7.5% ) that is 9 kg/m ² .

Each of the upper ceiling panels 315L of the upper layer 309B also has a generally U-shaped cross-section and are attached to the top of the stringers 313, e.g., with screws. If desired, each stringer 313 could include panel clips for snap-fitting the upper panels 315L to the stringers. The stringers 313 hold adjacent upper ceiling panels 315L apart with a gap 314B between them.

Depending on the total PCM load that the ceiling 309 needs to obtain proper temperature control of the lower plenum 8 , e.g., a room, the width of the gaps 314B between the upper panels 315L and the total surface area of the upper panels can be varied. For example, if approximately 3 pouches of 300 grams of PCMs 317B are fit on each upper panel 315L and if the upper layer 309B carries approximately 9 kg/ m ² of PCMs 317B , the ceiling 309 as shown in Figure 5 would have a total PCM-load of at least 18 kg/m ² .

Preferably, the openness of the upper layer 309B is at least equal to the openness of the lower layer 309A, e.g., approximately 7.5% openness. Also preferably, the gaps 314B between the upper panels 315L are off-set relative to the gaps 314A between the lower panels 315K, so as to facilitate more airflow between the two layers for enhanced heat transfer.

In the ceiling 309 of Figure 5, the same size and type of pouches of PCMs 317A, 317B are generally provided on both the lower and upper, ceiling panels 315K, 315L However if the size of the PCM pouches is customized to the dimensions

of the ceiling panels used, the number of pouches that fit on the ceiling panels can be optimized and the PCM-load can be maximized.

Figure 6 shows a third embodiment 509 of a linear ceiling which can be used in place of the linear ceiling 309 of Figure 1 and for which corresponding reference numerals (greater by 200) are used below for describing the same parts or corresponding parts.

The ceiling 509 has a lower first layer 509A of horizontally-extending parallel elongated linear ceiling panels 515K, an upper second layer 509B of horizontally- extending parallel elongated linear ceiling panels 515L, and a top-most third layer 509C of elongated parallel linear ceiling panels 515M. The lower layer 509A is held by horizontally-extending stringers 513, mounted on connector rods 511, attached to a building's structural ceiling 1. The upper layer 509B is mounted atop the stringers 513 and its upper ceiling panels 515L extend parallel to the lower ceiling panels 515K of the lower layer 509A . Adjacent lower ceiling panels 515K are held on the stringers 513 with a gap 514A ₁ between them, and adjacent upper ceiling panels 515L are mounted on the stringers 513 with a gap 514B, between them. Each of the lower and upper ceiling panels 515K and 515L has a generally U-shaped cross-section, and pouches of PCMs 517 are stacked within their U-shaped cross-sections.

The top layer 509C can be formed by horizontally-extending panels that have generally U-shaped cross-sections, such as are used as the lower and upper ceiling panels 515K and 515L ₁ and that contain pouches of PCMs. However, the top layer 509C is preferably formed by a plurality of vertically-extending hollow baffle panels 515M. The baffle panels 515M are preferably of equal length and are parallel to one another. Within the baffle panels 515M are PCMs, preferably sealed within plastic pouches (not shown). The baffle panels 515M can be suspended in a conventional manner by metal hangers 521 from a building's structural ceiling, above the upper ceiling panels 515L.

This invention is, of course, not limited to the above-described specific embodiments which may be modified without departing from the scope of the invention or sacrificing all of its advantages. In this regard, the terms in the foregoing description and the following claims, such as "left", "right", "front", "rear", "vertical" and "horizontal" have been used only as relative terms to describe the relationships of the various elements of the invention. For example, although preferred PCM loads and percents openness for the ceilings 109 and 309 of Figures 2 to 5 have been specified above, these parameters can be changed to suit differing use and climate requirements and differing upper and lower plenums of building spaces.

Also, the types of PCMs can be varied for differing use and climate requirements and differing upper and lower plenums of building spaces. In this regard, in offices and residential rooms in Europe, preferred PCMs are solid up to about 22 C. (which is considered the lower limit of human comfort), start to melt at temperatures over about 22 C, are completely liquid at about 28 C (which is considered the upper limit of human comfort), and have a temperature absorption peak between about 25 and 28 C.

Furthermore, the ceilings 309 or 509 of Figures 5 and 6 could be provided with additional vertically-extending hollow baffle panels, like the vertically-extending hollow baffle panels 515M of Figure 5, directly above upper layer 309B or 509B of ceiling panels 315L or 515L (e.g., below the baffle panels 515M of the top layer 509C of Figure 6). Such additional baffle panels could contain PCMs, preferably sealed within plastic pouches. Each of such additional baffle panels could also include a circumferential rectangular frame attached to the top of the stringers 313 or 513 or to the vertically-extending ceiling rods 311 or 511 , holding the stringers on the structural building ceiling.