Dehumidification airflow system and associated process.

Abstract

Dehumidification airflow system and associated method. The invention relates mainly to a dehumidification airflow system (1) for a building wall (2) using air circulation in a buffer space (4) adjacent to the building wall (2), control means being capable of controlling the circulation of a first volume of air to determine a variation in the quantity of water in the buffer space (4) by calculating the difference between the quantity of water extracted and the quantity of water supplied, and the circulation of a flow of a second volume of air through the buffer space (4) if the variation in the quantity of water is greater than a determined threshold, or controlling the stopping of the air circulation means (6) if the variation in the quantity of water is less than or equal to the determined threshold. Figure to be published with the abstract: Fig. 1

Description

Title of the invention: Dehumidification airflow system and associated method. Technical field

[0001] The invention falls within the field of sanitation of existing buildings.

[0002] The invention relates more particularly to an airflow system for dehumidifying the walls of a building, and to a method of dehumidification using such an airflow system. PRIOR ART AND DISADVANTAGES OF PRIOR ART

[0003] In the field of sanitation of existing buildings, the main interventions concern the dehumidification of the walls of said building. Indeed, the walls of the building are subject to humidity coming from several sources, and in particular from capillary rise from damp soils, damp ground in direct contact with buried or semi-buried walls, and from the adsorption of water molecules present in the ambient air (atmospheric humidity).

[0004] There are different methods of dehumidification, and in particular methods of dehumidification by aeraulic systems, such as that described in patent publication FR3003584. Thermally insulating and sealed walls are provided to be arranged at a distance from the wall to be dehumidified, so as to form a dehumidification buffer space by circulation of air in said buffer space according to a determined air flow rate.

[0005] Although functional, this method is not optimal, particularly because it is difficult, if not impossible, to control the humidity of the air entering and circulating in the buffer space. OBJECTIVE OF THE INVENTION

[0006] The invention thus aims to propose an aeraulic system for dehumidifying building walls with optimized efficiency. Statement of the invention

[0007] For this purpose, the aeraulic system for dehumidifying a building wall at least one thermal insulation wall affixed at a distance from an external or internal face of the building wall forming a dehumidification buffer space, a sealed wall affixed to one of the faces of the thermal insulation wall, and means for circulating air in the buffer space from a lower air inlet zone inside the buffer space to an upper air outlet zone outside the buffer space, which aeraulic system comprises: • First means of determining the absolute humidity of the air at level of the air inlet area in the buffer space; • Second means for determining the absolute humidity of the air at the level and the air outlet zone outside the buffer space, and • Control means connected to the air circulation means, to the first and second means for determining the absolute humidity, which control means are configured to: • Operate the air circulation means to generate a flow of a first volume of air through the buffer space for a determined time, • Determine the quantity of water brought into the buffer space by the air flow at the air inlet area, and the quantity of water extracted from the buffer space by the air flow at the air outlet area during said time determined from the respective absolute humidity values continuously determined by the first and second absolute humidity determining means, • Determine a variation in the quantity of water in the buffer space by calculating the difference between the quantity of water extracted and the quantity of water supplied, and • Control the circulation of a flow of a second volume of air through the buffer space if the variation in the quantity of water is greater than a determined threshold, or control the stopping of the air circulation means if the variation in the quantity of water is less than or equal to the determined threshold.

[0008] The system of the invention may also include the following optional characteristics considered in isolation or according to all possible technical combinations: - At the air inlet area inside the buffer space, the first means for determining the absolute humidity of the air comprise first means for determining the temperature and the relative humidity of the air, and at the air outlet area outside the buffer space, the second means for determining the absolute humidity of the air comprise second means for determining the temperature and the relative humidity of the air. - The control means are configured to control the circulation of the first volume of air in the form of a laminar flow in the buffer space. - The control means are configured to control the circulation of the flow of the first volume of air equivalent to the volume of the buffer space. - The air circulation means in the buffer space comprise air blowing means inside the buffer space arranged at the lower air inlet area and air suction means out of the buffer space arranged at the upper air outlet area.

[0009] The invention also relates to a method for dehumidifying a building wall, comprising at least one thermal insulation wall affixed at a distance from an external or internal face of the building wall, forming a dehumidification buffer space, a sealed wall affixed to one of the faces of the thermal insulation wall, and means for circulating air in the buffer space between a lower air inlet zone in the buffer space and an upper air outlet zone outside the buffer space, characterized in that the aeraulic system comprises first means for determining the absolute humidity of the air at the air inlet zone, second means for determining the absolute humidity of the air at the air outlet zone and control means connected to the air circulation means, to the first and second means for determining the absolute humidity, which method comprises the successive steps of: • Actuation of the air circulation means to generate a flow of a first volume of air through the buffer space for a determined time; • Continuous determination of absolute air humidity at the air inlet and air outlet areas during the specified time; • From the absolute humidity continuously determined in the previous step, determination of the quantity of water brought into the buffer space by the air flow at the air inlet zone and the quantity of water extracted from the buffer space by the air flow at the air outlet zone during the determined time; • Determination of a variation in the quantity of water in the buffer space by calculating the difference between the quantity of water extracted and the quantity of water supplied, and, selectively, • If the variation in the quantity of water in the buffer space is greater than a determined threshold, control of the circulation of a flow of a second volume of air through the buffer space between the air inlet zone and the air outlet zone, then stopping of the air circulation means; • If the variation in the quantity of water in the buffer space is less than or equal to the determined threshold, stop the air circulation means.

[0010] The method of the invention may also include the following optional characteristics considered in isolation or according to all possible technical combinations: - The flow of the first volume of air circulating through the buffer space is laminar. - The determined threshold associated with the variation in the quantity of water in the buffer space is equal to zero. - The control means periodically determine the so-called instantaneous variation of the quantity of water in the buffer space during the circulation of the flow of the second volume of air through the buffer space. - The control means control the stopping of the air circulation means before the circulation of the entire flow of the second volume of air if the instantaneous variation of the quantity of water determined in the buffer space is less than or equal to the determined threshold. - The second volume of air is four times greater than the first volume of air. PRESENTATION OF THE FIGURES

[0011] Other characteristics and advantages of the invention will emerge clearly from the description given below, for information purposes only and in no way limiting, with reference to the appended figures, among which:

[0012] [Fig.l] [Fig.l] represents a schematic sectional view of the air handling system of the invention;

[0013] [Fig.2] [Fig.2] represents a schematic side view of the means of circulation and determination of the absolute humidity of the invention. DETAILED DESCRIPTION OF THE INVENTION

[0014] It is first of all specified that in the figures, the same references designate the same elements regardless of the figure in which they appear and regardless of the form of representation of these elements. Similarly, if elements are not specifically referenced in one of the figures, their references can be easily found by referring to another figure.

[0015] It is also specified that the figures essentially represent an embodiment of the subject of the invention but that there may be other embodiments which meet the definition of the invention.

[0016] The present invention relates to an aeraulic system 1 for dehumidifying at least one wall 2 of a building, and advantageously all of the walls 2 of the building.

[0017] For each wall 2 of the building, the ventilation system 1 comprises, according to a first preferred variant of the invention, a thermal insulation wall 3 placed at a distance from an interior face of the wall 2 - said interior face of the wall 2 being that located inside the building - so as to form a dehumidification buffer space 4 between the interior face of the wall 2 and one of the faces of the thermal insulation wall 3.

[0018] According to this first preferred variant, the dehumidification aeraulic system 1 comprises a sealed wall called a vapor barrier wall 5 arranged on the opposite face of the thermal insulation wall 3. The thermal insulation and sealing properties of these walls 3, 5 make it possible to avoid, in the enclosed space inside the building, the presence of humidity in the walls 2.

[0019] According to a second variant, for each building wall 2, the thermal insulation wall 3 is placed at a distance from the wall 2 and opposite an external face of said wall 2. In this second variant, the vapor barrier wall 5 is provided on a face of the thermal insulation wall 3 which is opposite the building wall 2.

[0020] According to a third and final variant, the ventilation system 2 comprises two sealed walls 3 - each attached to a vapor barrier wall 5 - placed on either side of the building wall 2, so as to form two dehumidification buffer spaces 4.

[0021] In the remainder of the description, the air handling system 1 of the invention will be described in connection with the first preferred variant, according to FIGS. 1 and 2.

[0022] The airflow system 1 comprises air circulation means 6 in the buffer space 4 from a lower air inlet zone 7 inside the buffer space 4 to an upper air outlet zone 8 outside the buffer space 4.

[0023] More precisely, and with reference to [Fig.2], the circulation means comprise, for each dehumidification buffer space 4, at least one lower pipe 15 perforated with a plurality of blowing orifices 17 which forms the air inlet zone 7 and at least one upper pipe 16 perforated with a plurality of orifices 18 which forms the air outlet zone 8.

[0024] The circulation means 6 comprise air blowing means 9 connected to the inlet 19 of each perforated lower pipe 15, and which are configured to ensure the injection of air coming from the outside into the buffer space 4, via the orifices 17 of the lower pipe 15. The circulation means 6 further comprise air suction means 10 connected to the outlet 20 of each perforated upper pipe 16, and which are configured to ensure the exit of air from the buffer space 4, via the orifices 18 of the upper pipe 16.

[0025] The airflow system 1 also comprises control means 21 connected to the circulation means 6, and more precisely to the blowing means 9 and to the suction means 10.

[0026] These control means 21 typically comprise programmable control-command means configured to control the power of the blowing 9 and suction 10 means - and therefore the flow rate of blown or sucked air - as well as the operating time of said blowing 9 and suction 10 means. These control means 21 are remotely programmable and comprise wired and / or wireless communication means.

[0027] The airflow system 1 also comprises first determination means of the temperature of the air blown into the lower duct, as well as first means for determining the relative humidity of this blown air 13. In addition, the air handling system 1 also comprises second means for determining the temperature of the air sucked into the upper duct, as well as second means for determining the relative humidity of this sucked air 14.

[0028] These first and second means for determining the temperature and the relative humidity of the air 13, 14 respectively at the air inlet zone 7 and the air outlet zone 8 are connected to the control means 21, which can then determine the absolute humidity of the air at the air inlet zone 7 and at the air outlet zone 8 in the following manner.

[0029] The partial pressure of water vapor at a given temperature - at the air inlet zone 7 Pe and at the air outlet zone 8 Ps - is expressed as follows:

[0030] [Math.l] " _ ^re-Pes " _ Hrs. Pss e ” 100 e s “100

[0031] Hre and Hrs being the relative humidities respectively measured at the air inlet and outlet zones, Pes and Pss being the saturated vapor pressures respectively determined at the air inlet 7 and outlet 8 zones according to the following formula:

[0032] [Math.2] 17.279Te 17.279TS Pes = e6A146+237.475+Te and Pss = e6A146+237.475+Ts

[0033] Te and Ts being the air temperatures in degrees Celsius respectively measured at the air inlet 7 and outlet 8 zones.

[0034] Finally, from the ideal gas equation PV = NRT, and the absolute humidity determined respectively at the air inlet 7 and outlet 8 zones expressed according to the formula Hae = me / Ve and Has = ms / Vs, me, ms, Ve and Vs being respectively the mass of atmospheric water in grams entering the buffer space 4 via the air inlet zone 7, the mass of atmospheric water in grams leaving the buffer space 4 via the air outlet zone 8, the volume of air in cubic meters entering the buffer space 4 at the air inlet zone 7 and the volume of air in cubic meters leaving the buffer space 4 at the air outlet zone 4, then the mass of water (i.e. the quantity of water) added and the mass of water extracted from the buffer space 4 during a given time are expressed as as follows:

[0035] [Math.3] m^.dt = 2.167. Q Pe(V 273.15 + Te(t) 4(0 . dt and m.. dt = 2.167. Q.----------—. dt sv 273.15 + 7X0

[0036] Q being the air flow rate at the air inlet zone 7 and the air outlet zone 8. Preferably, the air flow rate at the air inlet zone 7 is identical to the air flow rate at the air outlet zone 8. In fact, the total mass of water added Me or extracted Ms during a total duration D of air circulation through the buffer space 4 is expressed as follows:

[0037] [Math.4] f P CO f P (t) Me = 2.167. Q. ----O dt and M. = 2.167. Q. ----O ^.dt (1) e J 273.15 + Te(0 5 v J 273.15 + 7X0

[0038] Thus, the control means 21 are configured to control the operation of the blowing means 9 and suction means 10 as a function of the absolute humidity data and the masses of water extracted from the buffer space 4 and added to the buffer space 4 determined.

[0039] Indeed, the invention makes it possible to program a prolonged circulation of air through the buffer zone 4 only if the absolute humidity of the outside air is lower than the absolute humidity in the buffer space 4.

[0040] To do this, the control means 21 of the air handling system 1 implement the following dehumidification process:

[0041] During a first step, the control means 21 actuate the suction 9 and blowing 10 means to control the circulation of a first determined volume of air through the buffer space.

[0042] Advantageously, the air flow rate is such that the Reynolds number associated with this circulation of the first volume of air through the buffer space 4 is less than 2000, which ensures the circulation of a laminar flow in the buffer space 4 and not turbulent. The circulation of a laminar flow limits the mixing between the air initially present in the buffer space 4 and the air supplied from outside via the air inlet zone 7, which in fact limits the volume of air necessary for the almost total replacement of the volume of air in the buffer space 4.

[0043] Indeed, the circulation of a first volume of air equivalent to the volume of the buffer space is sufficient to renew 63% of the air initially present in said buffer space 4. Now, the air flow rate being known, the control means 21 therefore control the actuation of the blowing and suction means for a first determined time ensuring the circulation of the first volume of air.

[0044] The Reynolds number Re is determined as follows:

[0045] [Math.5] _p.v b .L £\.f> V

[0046] lending the density of the air, vb the speed of the air crossing the buffer space, L the characteristic length over which the air flow varies (estimated at 1 meter), and q the dynamic viscosity of the air.

[0047] Thus, the control means 21 adjust the air circulation speed (and therefore the air flow rate) to maintain a Reynolds number below 2000.

[0048] During a second step and concomitantly with the circulation of this first volume of air through the buffer space 4, between the air inlet zone 7 and the air outlet zone 8, the first and second means for determining the relative humidity and the temperature of the air 13, 14 periodically measure the temperature and the relative humidity of the air leaving the blowing means 9 (and therefore entering the buffer space 4 via the air inlet zone 7) as well as the temperature and the relative humidity of the air leaving the suction means 10 (and therefore leaving the buffer space 4 via the air outlet zone 8).

[0049] These measurements are sent to the control means 21, which therefore have n measurements of relative air humidity and n measurements of air temperature at the air inlet zone 7, as well as n measurements of relative air humidity and n measurements of air temperature at the air outlet zone 8. Furthermore, each measurement of temperature or relative humidity taken at time k is associated with a time tk.

[0050] During a third step, the control means determine the mass of water added to the buffer space 4 as well as the mass of water extracted from the buffer space 4 during the circulation period of the first volume of air, i.e. during the first determined time.

[0051] To do this, the control means 21 calculate the instantaneous mass of water added and extracted for each time interval Atk determined between tk.i and tk, k ranging from 1 (start of the circulation of the first volume of air through the buffer space 4) to n (end of the circulation of the first volume of air through the buffer space 4). This calculation is carried out by adapting formula (1) with the method of rectangles.

[0052] Thus, for each time interval Atk, the extracted instantaneous water mass msk and the added instance water mass mek are respectively equal to:

[0053] [Math.6] P ek ^sk m ek = 2.167. m and m sk = 2,167.Q fc .^J 273.15+ T ek k 273.15 + T sk

[0054] Qk being the flow rate of the blowing means and the suction means for the interval of time Atk, Pek and Psk being the partial pressure values of water vapor for the time interval A* respectively at the level of the air inlet 7 and outlet 8 zones, Tek and Tsk being the air temperatures respectively at the level of the air inlet 7 and outlet 8 zones.

[0055] The control means then deduce the variation in water mass Amk for each interval Atk, by subtracting the mass of water added from the mass of water extracted during this interval Atk: Dmk = msk - =.¾-

[0056] The calculations are carried out for all the time intervals, i.e. for k between 1 and n, so that the total mass of water added Me in the buffer space 4 via the air inlet zone 7 and the total mass of water extracted Ms from the buffer space 4 via the air outlet zone 8 is calculated by the control means in the following manner.

[0057] [Math.7] n fc=i And n Ms = fc=l

[0058] Finally, the variation of the mass of water AM inside the buffer space 4, at the end of the circulation of the first volume of air, is calculated by the control means 21 according to DM = Ms - Me.

[0059] For greater precision and as an alternative, another calculation method may be used, for example the trapezoidal method.

[0060] If the variation in the mass of water AM is greater than a determined threshold - typically zero, which means that water has been extracted from the buffer space 4 during the circulation of the first volume of air - then the control means 21 control the circulation of a second volume of air for a second determined time, intended to dehumidify the wall or walls 2 of the building. Typically, this second volume of air is four times greater than the first volume of air, and therefore four times greater than the volume of the buffer space 4.

[0061] On the other hand, if the variation in the mass of water AM is less than or equal to the determined threshold - if the threshold is zero, this means that the mass of water in the buffer space 4 has not varied, or has increased during the circulation of the first volume of air, then the control means control the stopping of the circulation means 6.

[0062] Thus, the second volume of air intended to dehumidify the building wall(s) is only put into circulation if the preliminary test - which consists of the circulation of the first volume of air - concludes that water is extracted from the buffer space 4.

[0063] Daily, the control means carry out between one and ten preliminary tests which, if they indicate an extraction of water from the buffer space 4, are followed by a dehumidification cycle by the circulation of the second volume of air.

[0064] In a particularly advantageous manner, in order to further optimize the aeraulic system 1, the control means 21 periodically measure the instantaneous variation in the mass of water during the circulation of the second volume of air through the buffer space 4. If during a time interval Atk the instantaneous variation in the mass of water in the buffer space 4 becomes negative or zero, then the control means 21 control the stopping of the air circulation means 6 to avoid the addition of water in the buffer space 4 and to limit the operating time of the blowing 9 and suction 10 means.

[0065] The table below illustrates the comparison between dehumidification cycles implemented by a dehumidification system without control of external humidity, and dehumidification cycles with the aeraulic system 1 of the invention, the control means of which are controlled by external humidity. This test period extends over 4 months for the aeraulic system without control, and over 5 months for the aeraulic system 1 of the invention. [Tables 1] Designation Without servo-control With servo-control Variation Duration of a dehumidification cycle 60 min 40 or 60 min Number of cycles 127 131 Programmed duration Dp 7620 min 6600 min Total effective duration De 7620 min 4658 min De / Dp 1 0.71 -29% Extracted mass Ms 2103 2081 Added mass Me 314 33 Ms / Me 6.7 63.1 +842% Ms / De (g / min) 0.28 0.447 +62% Me / De (g / min) 0.041 0.007 -83%

[0066] These results demonstrate, for a comparable quantity of extracted water between the system without control and the aeraulic system 1 of the invention, that:

[0067] The effective operating time of the circulation means 6 is reduced by 29%, which allows energy savings.

[0068] The variation in the ratio between the total mass of water extracted from the buffer space 4 and the total mass of water added into the buffer space 4 is more than 800%. This means that system 1 of the invention, while allowing the extraction of quantities of water comparable with the aeraulic system without control over external humidity, extremely effectively reduces the water supply during dehumidification cycles.

[0069] This is corroborated by the Ms / De and Me / De ratios, which show a 62% increase in the rate of water extraction from buffer space 4 and an 83% decrease in the rate of water supply into buffer space 4.

[0070] The aeraulic system 1 of the invention therefore makes it possible to clean the walls 2 in an optimal manner, by optimizing the extraction of water vapor from the buffer space 4, by limiting the supply of water vapor into this buffer space 4, and by reducing the energy consumption of the air circulation means 6.

Claims

1. Claims Aeraulic system for dehumidification (1) of a building wall (2), comprising at least one thermal insulation wall (3) affixed at a distance from an external or internal face of the building wall (2) forming a dehumidification buffer space (4), a sealed wall (5) affixed to one of the faces of the thermal insulation wall (3), and air circulation means (6) in the buffer space (4) from a lower air inlet zone (7) inside the buffer space (4) to an upper air outlet zone (8) outside the buffer space (4), characterized in that the aeraulic system (1) comprises: - first means for determining the absolute humidity of the air (11) at the air inlet zone in the buffer space (7), - second means for determining the absolute humidity of the air (12) at the level and in the air outlet zone outside the buffer space (8), and - control means (21) connected to the air circulation means (6), to the first and second means for determining the absolute humidity (11, 12), which control means are configured to: - actuating the air circulation means (6) to generate a flow of a first volume of air through the buffer space (4) for a determined time, - determining the quantity of water brought into the buffer space (4) by the air flow at the air inlet zone (7), and the quantity of water extracted from the buffer space (4) by the air flow at the air outlet zone (8) during said time determined from the respective absolute humidity values continuously determined by the first and second absolute humidity determining means (11, 12), - determining a variation in the quantity of water in the buffer space (4) by calculating the difference between the quantity of water extracted and the quantity of water supplied, and - control the circulation of a flow of a second volume of air through the buffer space (4) if the variation in quantity of water is greater than a determined threshold, or order the stopping of the air circulation means (6) if the variation in the quantity of water is less than or equal to the determined threshold.

2. Aeraulic system (1) according to the preceding claim, characterized in that: - at the air inlet zone (7) inside the buffer space (4), the first means for determining the absolute humidity of the air (11) comprise first means for determining the temperature and the relative humidity of the air (13); - at the air outlet zone (8) outside the buffer space (4), the second means for determining the absolute humidity of the air (12) comprise second means for determining the temperature and the relative humidity of the air (14).

3. Airflow system (1) according to claim 1 or 2, characterized in that the control means (21) are configured to control the circulation of the first volume of air in the form of a laminar flow in the buffer space (4).

4. Aeraulic system (1) according to any one of claims 1 to 3, characterized in that the control means (21) are configured to control the circulation of the flow of the first volume of air equivalent to the volume of the buffer space (4).

5. Aeraulic system (1) according to any one of claims 1 to 4, characterized in that the air circulation means (6) in the buffer space (4) comprise means for blowing air inside the buffer space (9) arranged at the lower air inlet zone (7) and means for sucking air out of the buffer space (10) arranged at the upper air outlet zone (8).

6. Method for dehumidifying a building wall (2), comprising at least one thermal insulation wall (3) affixed at a distance from an exterior or interior face of the building wall (2) forming a dehumidification buffer space (4), a sealed wall (5) affixed to one of the faces of the thermal insulation wall (3), and means of air circulation (6) in the buffer space (4) between a lower air inlet zone (7) in the buffer space (4) and an upper air outlet zone (8) outside the buffer space (4), characterized in that the aeraulic system (1) comprises first means for determining the absolute humidity of the air (11) at the air inlet zone (7), second means for determining the absolute humidity of the air (12) at the air outlet zone (8) and control means (21) connected to the air circulation means (6), to the first and second means for determining the absolute humidity (11, 12), which method comprises the successive steps of: - Actuation of the air circulation means (6) to generate a flow of a first volume of air through the buffer space (4) for a determined time; - Continuous determination of the absolute humidity of the air at the air inlet (7) and air outlet (8) zones during the determined time; - From the absolute humidity continuously determined in the previous step, determination of the quantity of water brought into the buffer space (4) by the air flow at the air inlet zone (7) and the quantity of water extracted from the buffer space (4) by the air flow at the air outlet zone (8) during the determined time; - Determination of a variation in the quantity of water in the buffer space (4) by calculating the difference between the quantity of water extracted and the quantity of water supplied, and, selectively, • If the variation in the quantity of water in the buffer space (4) is greater than a determined threshold, control of the circulation of a flow of a second volume of air through the buffer space (4) between the air inlet zone (7) and the air outlet zone (8), then stopping the air circulation means (6); • If the variation in the quantity of water in the buffer space (4) is less than or equal to the determined threshold, stop the air circulation means (6).

7. Method according to the preceding claim, characterized in that the flow of the first volume of air circulating through the buffer space (4) is laminar.

8. Method according to claim 6 or 7, characterized in that the determined threshold associated with the variation in the quantity of water in the buffer space (4) is equal to zero.

9. Method according to any one of claims 6 to 8, characterized in that the control means (21) periodically determine the so-called instantaneous variation of the quantity of water in the buffer space (4) during the circulation of the flow of the second volume of air through the buffer space (4).

10. Method according to the preceding claim, characterized in that the control means (21) control the stopping of the air circulation means (6) before the circulation of the entire flow of the second volume of air if the instantaneous variation of the quantity of water determined in the buffer space (4) is less than or equal to the determined threshold.

11. Method according to any one of claims 6 to 10, characterized in that the second volume of air is four times greater than the first volume of air.

Images