AU628369B2

AU628369B2 - Passive heat transfer building panel

Info

Publication number: AU628369B2
Application number: AU40151/89A
Authority: AU
Inventors: Robert Kenneth Prudhoe
Original assignee: Individual
Current assignee: Individual
Priority date: 1988-08-22
Filing date: 1989-08-22
Publication date: 1992-09-17
Anticipated expiration: 2009-08-22
Also published as: AU4015189A

Description

628369 Form COMMONWEALTH OF AUSTRALIA PATENTS ACT 1952-62 COMPLETE SPECIFICATION

(ORIGINAL)

FOR OFFICE USE: Application Number: Lodged: Complete Specification Lodged: Accepted: Published: Priority: Related Art: Class Int. Class TO BE COMPLETED BY APPLICANT Name of Applicant: Address of Applicant: Actual Inventor: Address for Service: TO BE COMPLETED BY APPLICANT ROBERT KENNETH PRUDHOE 36 Princes Street, St Kilda, Victoria, Australia ROBERT KENNETH PRUDHOE R.K. MADDERN ASSOCIATES, 345 King William Street, Adelaide, South Australia, Australia Complete Specification for the invention entitled: "PASSIVE HEAT TRANSFER BUILDING PANEL" The following statement is a full description of this invention, including the best method of performing it known to me.

This invention relates to a building panel suitable for use in building and room construction and which in use passively transfers heat from the internal volume of a structure comprising these panels, to the external of the structure, but which does not allow a significant reverse transfer.

Some equipment, for example electronic telephone equipment, which generates heat in its operation is adversely affected if its temperature rises above specific limits. Heat removal using a refrigeration plant heat pump system is in many cases the only practical, or economically acceptable method of removing the heat to control the electronic equipment within required temperature limits and continuous use of refrigeration plant to prevent excessive temperature rise of the air within an enclosed insulated room can be very expensive to operate.

It is an object of the invention to provide a highly efficient heat transfer building panel where heat passes through the panel from the warm side of the panel to the cool side, the panel acting as an effective insulator to heat flow S in the reverse direction.

Briefly, this invention consists of a panel structure S characterised by its ability to transfer heat preferential in one direction through the panel comprising, side walls and edge walls forming a sealed hollow building panel having first and second walls opposed to each other, a two phase heat-transfer fluid partially filling said panel, valve means to control the internal vapour pressure of said panel, Swherein under conditions of temperature differential between the external surface of said first and second side walls and a controlled internal vapour pressure, upon sufficient heat energy being imparted through said first opposed wall to convert the two phase heat-transfer fluid into a vapour state, vapour migrates to said second opposed wall and condenses thereon into a liquid state thereby preferably transferring heat energy in one direction from said first to said second opposed wall.

-2i -r~-rt~i U CCIC-I.~L S r It is highly desirable for the walls and ceiling of the building to have a special construction which can reduce the hours of operation of the refrigeration plant to minimise wear *o.

-2a- -2aoooo oooo oo /28 and tear on the refrigeration plant, and to save energy. To achieve this objective, it would be very practical for the walls and ceiling of the equipment room to act as a thermal diode which can transmit heat from the inside of the room to the outside when the outside air temperature is low, and to act as an insulator to heat flow when the outside air temperature is excessively hot.

The use of the walls and ceiling suitably constructed from special thermal diode panels according to this invention can fit together in modules and transmit heat from the warm side of the panel to the cool side of the panel would enable the building/cooling system to take advantage of the natural cooling in times of low ambient temperature, whilst during excessively hot periods of weather, the building fabric made from these panels would act as an insulator to heat gain from the outside, and thus reduce the heat load on the air .se conditioning means for the room.

Such a wall and ceiling construction reduces the need for e the refrigeration plant to operate when the outside air temperature is cool whilst during hot weather the solar heat gain from outside to the inside of the building will be reduced due to the insulation effect of the proposed panel. This will oooo S minimise the cooling load on the refrigeration plant and save energy and operating costs, whilst the reliability of the 25 overall building/cooling system to control the temperature of e.o. the electronic equipment will be enhanced.

In a similar way specifically for the purpose of heating of buildings during cool weather it is highly advantageous to

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construct sections of the walls and roof structures of buildings from special highly efficient thermal diode panels which can fit together and transmit the suns energy directly into building enclosures via these panels whilst acting as very good thermal insulators to the interior trapped atmosphere at night or during periods when it is cool or cold outside. The usage of panels in accordance with the invention effectively reduces the amount of alternative energy source usage needed, with consequent savings in energy costs.

The use of the invention for a particular application as to whether it is used for cooling or heating of a building -3mw_ -re I- ir -u.

enclosure will depend directly on the method used to install the panels in the walls, ceiling or roof structure of a building.

The panel acts as a thermal diode, that is heat being transferred only in one direction as a result of the introduction of a suitable two phase liquid into the sealed panel, where upon on the hot side of the panel the liquid absorbs heat and changes phase to vapour, wherein because of the differential from one side to the other of the panel of the vapour-pressure, the vapour migrates and condenses on the cooler side of the panel giving up its latent heat to be emitted from the cooler side of the panel. The liquid then by gravity returns to the hot side to a reservoir of the fluid to 6!9.0: repeat the process. Preferably it is a feature of the panel that the pressure within the sealed panel is suitably low to reduce the vaporization temperature of the liquid and enable heat transfer to occur at or below room temperatures consistent with the panels application.

eeoc o: Furthermore, it is a further feature of the panel that when used as a wall panel the means by which the two phase heat-transfer fluid is distributed to the higher regions of the panel and concomitantly evenly distributed on the surface area on the inside volume of the structure comprising the panels, a wick is desirably used.

A wick suitable for this purpose may comprise a plurality 0 0" of twills or of a mesh structure. The wick will be chosen to

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maximize the capillary head and ensure that the wick permeability will allow maximum liquid and vapour capacity in conjunction with optimum thickness to minimize heat transfer resistance.

A panel incorporating a wick will allow operation of the panel at angles to the vertical.

Careful choice of panel, wick and liquid to match the required heat transfer characteristics is required to ensure compatibility; this choice being well considered by those knowledgable in the art.

The operation of the panel in accordance with the present invention, will now be described with reference to the accompanying drawings and embodiments, -4- I _J Fig 1 Shows a section view of a panel, according to the invention; Fig 2 shows a lower first side of a panel; Fig 3 shows an alternative shape to Fig 2; Fig 4 shows an alternative shape to Fig 2; Fig 5 shows further alternative shapes to Fig 2; Fig 6 shows a section side view of a panel; Fig 7 shows a section view of a room having ceiling panels according to the invention; Fig 8 shows a section view of adjoining room incorporating ceiling panels according to the invention; Fig 9 shows a section view of novel wall construction incorporating panels according to the invention; Fig 10 shows a perspective view of a building enclosure 5 incorporating wall and ceiling panels according to the invention; and Fig 11 shows a section view of a wall panel according to the invention.

Fig 1 is a section view of a typical panel, which may be used as a ceiling panel, in accordance with the present invention. First side, 1, the bottom and a second side, 2, the top of the panel are made from any suitable material with satisfactory heat transfer characteristics and physical properties. In this embodiment a copper material is used alternatively thin plastic, polybutylene, polyethylene, •5 aluminium, stainless steel or other suitable material which is strong, durable and cannot pass moisture or gas and has low resistance to heat transfer is useable dependent on the compatibility considerations and the desired heat transfer characteristics of the panel.

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The inside of the panel is airtight and contains an amount of a suitable two phase heat-transfer liquid 3, which can boil at a specific temperature dependant on the pressure of vacuum which exists within the totally sealed panel. The panel contains a valve, 4, which makes it possible to adjust the pressure of the liquid/vapour mixture inside the panel to any desired pressure, prior to installation of the panel or alternatively, if desired during operation. In this embodiment the liquid is acetone.

~e It will be appreciated that by reducing the pressure inside the panel, the liquid sitting on the bottom of the panel will boil and vaporise at a lower temperature. Likewise, it will also be appreciated, that increase of the pressure exerted on the liquid/vapour mixture inside the panel, will increase the boiling temperature of the liquid which is contained inside the panel. Thus allowing similar panels to be used in a variety of situations by variance of one easily adjustable condition of the panel. When the liquid, 3, begins to boil the latent heat of vaporisation to permit this phase change will be absorbed from the warm air which is above the boiling temperature of the liquid, and adjacent with the underside of side, 2, of the panel.

will Careful choice of materials and manufacturing tolerances will ensure the panel remains air and vapour tight and will S lengthen its serviceable life.

In this regard satisfactory materials for example for external fabrication of the panel in this embodiment would be copper although aluminium, stainless steel may be used.

5O56 To enable the panel to be used in conditions requiring low internal pressures a suitable stiffener or support may be necessary to maintain the panel shape.

60:0" Stiffening to make the panel robust is achieved in this oe. embodiment by supporting the panel with a framework, 5, and using a sufficient number of small balls, 6, made from any l 0o suitable material to fill or partially fill the panel.

Alternatively, a plastic moulded waffle type grid may be used.

Choice of the material from which this support means is made will be in accordance with compatibility requirements. It will be appreciated that the large number of small balls, 6, which are plastic in this embodiment will also act as an insulator to heat transfer in either direction.

It will also be appreciated that the balls, 6, will need to have low surface tension, so that the liquid which has condensed on side, 2, can easily fall down through the balls, 6, or other suitably shaped objects to the bottom evaporator plate, This figure showing a horizontally disposed panel for the purposes of example.

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0r The heat transfer mechanisms is as explained previously and in this embodiment will transfer the heat from say a computer room to the ceiling cavity for forced air transference to the atmosphere.

It is desirable that the lower evaporator plate, 1, has a suitable configuration to assist accumulation and boiling of the liquid. In this regard it is desirable to manufacture plate, 1, so that the heat transfer area may be maximised whilst maintaining adequate strength within the panel.

Likewise it is also desirable if the upper condenser plate also has a similar type of configuration to also maximise surface area and exposure of the condensing area of the vapour to the outside atmosphere.

Fig 2 shows an embodiment of a lower plate, 1, construction which will assist liquid accumulation and increase S the exposed surface area of such a plate. Thus warm air inside S the enclosure or room which is above the boiling temperature of the liquid inside the panel is adjacent continuous hollow fin arrangements, 7, and which increases the effective surface area of the panel, whilst providing a suitable reservoir for the liquid, 3, to accumulate within the panel. It will be appreciated that such a lower plate configuration is also applicable to the upper condensing side of the panel.

A variety of configurations will be apparent to those 25 conversant in the art. For example the Vee shaped fins, 8, and, 9, as shown in Fig 3 and the corrugations of the surface shown in Fig 4 or any of the other shapes, 10, 11, and, 12, as shown in Fig 5 may be manufactured to enhance thermal performance and mechanical strength if aesthetically ;0 acceptable.

A multiplicity of panels can be positioned together to increase the overall surface area of heat transfer using a modular panel jointing system as shown by example in Figs 1 and 6. A tongue, 13, and groove, 14, are shown by way of example in these Figs 1 and 6.

Some applications of panels according to the invention are now shown by way of example: Fig 7 illustrates the inside, 20, of a building, 21, where the walls, 22, and, 23, and floor are constructed of 4d 7-

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materials and the ceiling of the enclosure, 20, is constructed with a number of panels, 24, 25, 26, 27, and, 28,. The building enclosure, 20, contains some heat emitting equipment, 29, which may be electronic equipment, and the airconditioning unit, 30, is used, to remove both the equipment heat and externally gained heat from the building enclosure. Above the panels is shown a sun shade, 31, which minimises the solar heat gain to the building enclosure.

In such an application the panels transmit heat from the inside of the enclosure, 20, to the outside during the period when the outside ambient air temperature is low compared to the internal building temperature. The panels will also act as an effective insulator to heat flow at times when the outside ambient air temperature is hotter than the internal enclosed j5 temperature. In such an application the panel will assist in a passive removal of heat from the enclosure when it is cool outside, thus reducing the period of operation of the refrigeration plant, Another application of the panel is shown in the illustration of Fig 8 where the panel is used to help cool down go a thermal storage medium such as phase change chemicals (PCC) contained in pipes or like constructions, 42, at times when the outdoor temperature is cool. External building temperature is thus sufficiently low and the stored cooling device in a room may be used via an automatically operated fan system, 44, and, to cool a building enclosure, 20, when it gets too hot for example when the refrigerated cooling plant, 23, fails.

When the outside air is cold enough the fan, 43, turns on and heat is transmitted through ceiling panels, 41, from room, 40, to the outside ambient which in turn cools down the PCC cool storage medium or other thermal storage media to some desired temperature depending on control settings. The ceiling panels, 41, thus may provide a thermal diode ceiling to create a cooling down of the thermal storage medium.

Thus in the event of the refrigerated air conditioning plant, 30, failing and room, 20, becoming too hot, thermostat, 46, will turn on fans, 44, and, 45, to circulate air between rooms, 20, and, 40, where the excess heat from room, 20, is absorbed into the cool thermal storage media, 42, contained 8- 555

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A0 f coi I 2 within room, 40, the whole process acting as a heat transfer of the excess heat from room, 20, into room, 40, thus act as a backup cooling system.

The illustration in Fig 9 shows yet another method of application for panels utilised in both wall construction and ceiling construction of a thermally transparent electronic equipment enclosure, Panels, 51, 52, 53 and, 54, are shown mounted horizontally as part of the overall vertical wall construction of insulated walls, 55, and, 56. A heat emitting load (which may be electronic equipment), 57, is contained within the enclosure, 50, having a ceiling panel, 58. The wall panels assist the ceiling panel to transmit heat from the enclosure, 20, during periods of cool ambient external temperature. During times of hot external temperature the panels act as insulator panels which reduce the hours of operation of an alternative cooling device.

The ceiling area of the enclosure, has a sun shade, 59, to minimise solar heat gain to the enclosure.

Fig 10 shows a perspective view of a building enclosure, 98, in which the panel is used as a means to transmit the sun's solar heat into the building through the wall panels, 100, and the ceiling panels, 102. It is to be noted that the wick or capillary material, 104, in the wall and wick, 106, 25 in the ceiling panel are in this embodiment liquid transport medium within the panel positioned on the hot side of the *i panel, ie the side that faces the sun. A sintered wick in this embodiment, acts via capillary action to cover the entire surface area of the panel with the two phase liquid and it is essential that the bottom of the capillary material is immersed in the liquid return sumps, 110, shown in the eoee wall panel and, 112, in the roof panel. In this embodiment heat transfer of between 40-70 Watts/square metre/'C temperature difference is achievable.

The wall panels, 5, are shown with one sheet of light transparent material, 114, which may be glass or perspex which is positioned adjacent but away from the panels. These both minimise heat loss created by the wind blowing over the panels and also acts as further elements of thermal insulation and thus prevent heat flow from inside the building to outside I I MT 9 *9* -9 a- *r/ oooo rz t/ during the night or in periods of very cold weather when there is little or no sun.

Alternatively, adjustable louvres, 120, are shown which can be open in the day to assist solar collection to the panels and closed at night to minimise heat loss from the panels.

Louvres, 120, are essential in the summertime or in hot weather to prevent unnecessary heat gain to the building at times when cooling may be required. In a similar manner the panels, 102, shown mounted on the roof also have a suitable glass or perspex, 114, plus louvres or roller blinds to shade the panels from incident solar radiation during hot weather.

Fig 11 shows a view of a wall type panel. The wick, 104, is preferably sinteed copper or some other type of suitable col(ary metallic mesh. Thebmaterial, 104, must be placed contiguous ]5 with the hot evaporator side or sun side of the wall, and must drop into the liquid sump, 110, to enable it to draw up the liquid. Ideally the entire evaporator surface area will become wetted with the liquid. Also shown is a glass or perspex wind shield, 114,.

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Claims

1. A panel structure for transferring heat preferentially in one direction, said panel structure comprising, side walls and edge walls forming a sealed hollow building panel having first and second walls opposed to each other, a two phase heat-transfer fluid partially filling said panel, valve means to control the internal vapour pressure of said panel, arranged so that under conditions of temperature differential between the external surface of said first and second side walls and a controlled internal vapour pressure, upon sufficient heat energy being imparted through said first opposed wall to convert the two phase heat-transfer fluid into a vapour state, vapour migrates to said second opposed wall and condenses thereon into a liquid state thereby transferring heat energy in one direction from said first to said second opposed wall.

2. A panel structure according to claim 1 wherein said two phase heat-transfer fluid comprises any one of the Class 1 refrigerants, fluorocarbons, water, ammonia, freon 11, s es pentane, freon 113, acetone, methanol, ethanol and liquid 25 metal working fluids or a combination thereof. .:so 0000

3. A panel structure according to claim 1 further comprising a capillary means located internal to said panel S• and adjacent said first opposed wall. F.6

4. A panel structure according to claim 3 wherein said •co capillary means comprises a sintered copper wick material. eoee A panel structure according to claim 3 wherein said capillary means comprises a metallic mesh material. -11-

6. A panel structure according to claim 3 further comprising a reservoir located within said panel, below and adjacent said capillary means into which depends said capillary material and adapted to receive said two phase heat-transfer in its liquid state from said second opposed wall.

7. A panel structure according to claim 1 further comprising a support means located internal of said panel and between said first and second opposed walls to space their internal surfaces away from each other.

8. A panel structure according to claim 7 wherein said support means comprises a grid of beams of non-heat conducting material.

9. A panel structure according to claim 8 wherein said support means comprises a plurality of spherical bodies. 0. A panel structure according to claim 7 wherein said support means comprises a material having low surface tension with respect to said two phase heat-transfer fluid. oeoo i11. A panel structure according to claim 1 wherein the external surface of said first opposed wall of said panel is non-planar.

12. A panel structure according to claim 11 wherein the profile of said first opposed wall comprises a corrugated shape. •ego

13. A panel structure according to claim 1 wherein the profile of said first opposed wall comprises a dimpled shape. -12- S T,? A4Z Z)n E

14. A panel structure according to claim 1 wherein said panel comprises attachment means which are adapted to allow abutment of said walls against edge walls of a similar panel structure to form ceilings and wall portions of a building. Dated this 10th day of July, 1992. ROBERT KENNETH PRUDHOE By his Patent Attorneys R K MADDERN ASSOCIATES *see -13- T 9 -13-