Drum wall comprising a heat storage wall and a transparent cover

Description

Field of invention

[0001] The present invention relates to the field of bioclimatic architecture and more particularly to the passive thermoregulation of buildings using the principle of the "Trombe wall". A Trombe wall is composed of an exterior glazing placed in front of a dark wall to cause a greenhouse effect which heats the air gap located between the two elements. Openings in the lower and upper parts of the wall then ensure, on demand, air circulation by thermosiphon between the air gap and the interior of the premises to be heated. By regulating the system, the calories are stored in the wall and returned in a phase-shifted manner to the building. The air heated in the air gap enters the premises through the upper openings. By heating the room, it cools on contact with the air in the room and, once cooled, returns through the lower openings in the air gap to heat up again. Approximately two-thirds of the energy is returned by direct transmission.The remaining third is restored out of phase thanks to the inertia of the wall.

[0002] In the absence of solar radiation, the convective flow reverses, which can cause accelerated cooling of the room. Manually or automatically closing dampers are installed at the openings. These dampers control the passage of air through the openings to prevent the room from cooling in the absence of sufficient sunlight and / or to ensure cooling of the room during periods of extreme heat. State of the art

[0003] The Trombe wall (or Trombe-Michel) was designed by Edward Morse in 1881 and described in American patent US246626A.

[0004] Many developments have been proposed, such as: walls incorporating phase change material (PCM), zigzag walls, water walls, hybrid walls, trans-solar walls, composite walls, fluidized walls, walls with photovoltaics, walls with a forced air system, etc.

[0005] Also known is US4216765 which describes a transparent solar heat collector using solar radiation to heat and illuminate a building structure, the solar heat collector comprising a transparent converter glass absorbing at least about 90% of the infrared radiation in the solar radiation spectrum incident on the glass for conversion of the infrared radiation to thermal energy, support means carrying the transparent converter glass for exposure to solar radiation and transmission of light into the building structure, and means for passing a transparent heat transfer liquid into contact with the transparent converter glass to transport thermal energy from the glass into the building structure. Disadvantages of the prior art

[0006] The prior art solutions present an aeraulic behavior that can be improved as shown by the theses on the study of convection between the walls of a Trombe wall. The velocity and temperature profile varies in the thickness of the vertical channel formed between the two walls, which leads to disparities between the exchanges between the circulating air and the collector wall. Solution provided by the invention

[0007] In order to overcome this drawback, the present invention relates, in its most general sense, to a trombe wall having a thermal storage wall and a transparent cover defining between them a space for air circulation and heat exchange, said space having in its lower part an opening opening into the interior of the building and in its upper zone an opening opening into the interior of the building, characterized in that the surface of said thermal storage wall facing said transparent cover has at least one means of disturbing the aeraulic boundary layer consisting of one of the three alternatives below.

[0008] The term "air boundary layer" refers to the interface zone between a body and the air flowing during relative movement between the two.

[0009] When a real fluid, in this case air, flows along a wall of a fixed body, in this case the storage wall, the velocities on the wall are zero while at infinity (i.e. far from the wall) they are equal to the flow velocity. On a normal to the wall, the velocity must therefore in all cases vary between 0 and a maximum. The variation law depends on the viscosity of the fluid which induces friction between the neighboring layers: if we consider two successive layers, the slower layer tends to slow down the faster layer which, in return, tends to accelerate it.

[0010] Advantageously, said thermal storage wall facing said transparent cover has a plurality of means for disturbing the air boundary layer distributed laterally and vertically.

[0011] According to the first alternative, said means or means for disturbing the air boundary layer consist of motorized transverse rollers flush with the surface of said thermal storage wall with a thickness of between 10 and 100 millimeters.

[0012] Advantageously, said means or means for disturbing the aeraulic boundary layer consist of motorized transverse rollers flush with the surface of said thermal storage wall with a thickness corresponding to 0.2 to 2 times the thickness of said boundary layer.

[0013] According to a first variant, said rollers are smooth.

[0014] According to a second variant, said rollers have longitudinal ribs. These longitudinal ribs extend in radial planes, or have undulations or at least one twist.

[0015] According to the second alternative, said means or means of disturbing the aeraulic boundary layer consist of protuberances with a thickness of between 10 and 100 millimeters distributed over the surface of said thermal storage wall.

[0016] According to the third alternative, said means or means of disturbing the air boundary layer consist of vibrating surfaces.

[0017] Advantageously, said means or means for disturbing the air boundary layer consist of electrodes forming a dielectric barrier discharge system.

[0018] Advantageously, said electrode(s) consist of two adjacent flat conductive blades arranged on either side of an insulating film. Detailed description of non-limiting examples of implementation

[0019] The invention will be better understood and other advantages thereof will appear more clearly in the light of the following description of examples of the construction of a Trombe wall according to the invention, given solely by way of example, and made with reference to the appended drawings in which: [ Fig. 1 ] there figure 1 represents a sectional view of a first exemplary embodiment of the invention; [ Fig.2 ] there figure 2 represents a sectional view of a second exemplary embodiment of the invention. General principle

[0020] The invention is based on the disturbance of the air flow at the surface of said thermal storage wall facing said transparent cover having at least one means of disturbing the air boundary layer. The disturbance of the thermal and air boundary layer can be obtained by modifying the velocity of the fluid at the wall and / or within the boundary layer itself. From experience, the intensity of this velocity must be greater than the convection velocity defined by the ratio between the thermal diffusivity and a characteristic length of the pipe. An increase in the velocity of the fluid close to the wall or within the boundary layer leads to a modification of the heat transfers between the collector wall and the circulating air. Thus, a rotating roller, a rolling tape or a dielectric barrier discharge system are means which generate a velocity at the wall, and a fortiori, at the boundary layer.

[0021] This is achieved by a "means of disturbance", a generic and functional formulation that will be broken down into different structural examples. This "means of disturbance of the thermal and aeraulic boundary layer" determines the function that the means provided on the surface of the opaque wall must fulfill, in this case creating a disturbance of the boundary layer, thus modifying a laminar flow. The opaque wall of the Trombe Wall is generally flat and has a smooth surface. Presentation of a first embodiment

[0022] There figure 1 represents a first version of a Trombe wall according to the invention. It consists of a wall formed by a thermal storage wall (1), for example a 40 centimeter thick concrete wall or a breeze block wall, or a 45 centimeter wall made of earth. The rear face (inside the building) is covered by insulation (2). It comprises a transparent wall (3), for example a polycarbonate sheet or glazing defining an air gap (11) closed by crosspieces (4, 5) ensuring the fixing of the glass (3) on the wall (1).

[0023] Optionally, the thermal storage wall (1) may contain a phase change material increasing the thermal storage capacity.

[0024] It is crossed by a series of vents (7) aligned in the lower part of the wall (1), and a series of vents (6) aligned in the upper part of the wall (1). These vents (6, 7) open respectively near the ground and near the ceiling of the interior of the building. The air circulates by convection between the lower part and the upper part of the space formed between the wall (1) and the window (3), to heat up in contact with the wall (1) and open into the building through the upper vents (6). The air cools in the building and the cold air is evacuated through the vents (7) of the lower part to return to the space formed between the wall (1) and the window (3).

[0025] Optionally, shutters control the opening or closing of the lower (7) and / or upper (6) vents.

[0026] Alternatively, vents are also provided to communicate with the exterior of the building. Similarly, shutters can control the opening or closing of vents communicating with the exterior of the building.

[0027] In the version illustrated by the figure 1 , the wall (1) incorporates transverse rollers (8, 9, 10) extending across the width of the wall (1). They are integrated into grooves formed in the wall (1) and protrude from the outer surface of the wall (1), facing the glazing (3), by a few tens of millimeters, typically 10 to 100 millimeters. These transverse rollers (8, 9, 10) are driven by electric motors and have a smooth surface or one coated with ribs or corrugated threads.

[0028] According to a particular variant, the transverse rollers (8, 9, 10) form the rotor of an electric motor further comprising a fixed wound stator. The transverse rollers (8, 9, 10) are formed in this case from a ferromagnetic material constituting a yoke against which permanent magnets are glued.

[0029] These transverse rollers (8, 9, 10) have the effect of disturbing the boundary layer of the air flow forming on the surface of the wall (1) by creating turbulence ensuring mixing of the air blade circulating between the glazing (3) and the thermal storage wall (1), so as to increase the thermal exchanges during circulation between the lower zone and the upper zone of the Trombe wall. Implementation variant

[0030] There figure 2represents an alternative embodiment of the invention, where the disturbance of the boundary layer is produced by a dielectric barrier discharge system. For this purpose, the wall (1) has on its surface, regularly distributed, electrodes formed of two adjacent conductive blades (12, 13), separated by a dielectric film (14). One of the electrodes (12) is placed on the dielectric film (14) and is laterally offset relative to the other electrode (13) arranged on the opposite face of the dielectric film (14).

[0031] The conductive blades (12, 13) are powered by discharges with an alternating voltage of 3 to 10 kV with a frequency of a few kHz. When the voltage applied to the gas gap becomes equal to the ignition voltage (defined by the Paschen curve), the formation of a conductive channel is observed. Given the low mean free path at atmospheric pressure, this micro-discharge channel has a radius typically of the order of a hundred µm.

[0032] The dielectric opposite the micro-discharge then behaves like the insulator of a capacitor whose plates are constituted by the conductive blades (12, 13). The passage of the current induces an accumulation of charge on the surface of the solid dielectric opposite the discharge channel which leads to an increase in the voltage. If the increase in this voltage as the discharge develops is faster than the increase in the voltage applied to the place where the micro-discharge was initiated, it causes a drop in the voltage applied to the gas, which leads to the extinction of the discharge.

[0033] Thus, the micro-discharge is blocked well before reaching a sufficient degree of ionization to transition to arc mode. If the voltage applied to the electrodes continues to increase, micro-discharges initiate at new positions because the presence of residual charges on the surface of the dielectric reduces the electric field seen by the gas at the positions where the micro-discharges have already developed. Upon polarity reversal, the charges previously deposited on the dielectric allow a breakdown of the gas under a weaker electric field than during the first alternation.

[0034] The potential difference between two metal blades (12, 13) to establish an electric discharge leads to the arc regime, which is localized and causes a very high temperature rise temporarily producing a plasma disturbing the boundary layer.

[0035] The energy source may consist of photovoltaic cells forming, for example, a strip on the glazing (3) and providing power to an electronic circuit of the dielectric barrier discharge (DBD) system.

Claims

1. Trombe wall having a thermal storage wall (1) and a transparent cover (3) defining between them a space for air circulation and heat exchange, said space having, in its lower part, an opening (7) leading to the interior of the building and, in its upper zone, an opening (8) leading to the interior of the building, characterized in that the surface of said thermal storage wall (1) facing said transparent cover (3) has at least one means for disturbing the thermal and aeraulic boundary layer, which means consists of: - motorized transverse rollers (8, 9, 10) flush with the surface of said thermal storage wall (1), said rollers having a thickness of between 10 and 100 millimeters or - by protuberances having a thickness of between 10 and 100 millimeters distributed over the surface of said thermal storage wall or - by vibrating surfaces.

2. Trombe wall according to claim 1, characterized in that said thermal storage wall (1) facing said transparent cover has a plurality of laterally and vertically distributed means for disturbing the aeraulic boundary layer.

3. Trombe wall according to claim 1, characterized in that said means for disturbing the aeraulic boundary layer consists or consist of motorized transverse rollers (8 to 10) flush with the surface of said thermal storage wall, said rollers having a thickness corresponding to 0.2 to 2 times the thickness of said boundary layer.

4. Trombe wall according to claim 3, characterized in that said rollers (8 to 10) are smooth.

5. Trombe wall according to claim 4, characterized in that said rollers (8 to 10) have longitudinal ribs.

6. Trombe wall according to claim 1, characterized in that said means for disturbing the aeraulic boundary layer consists or consist of electrodes forming a dielectric barrier discharge system.

7. Trombe wall according to the preceding claim, characterized in that said electrode or electrodes consist of two adjacent flat conductive strips (12, 13) arranged on either side of an insulating film (14).