Solar collector insulation and obtained product

Abstract

A solar collector, in particular a solar thermal collector, is formed of at least one circuit transporting a heat transfer fluid, and includes at least one insulator, in particular in the form of at least one layer, formed of flakes and/or nodules of mineral wool(s) or mineral fibers. A process is provided for insulating or manufacturing a solar collector into which flakes and/or nodules of mineral wool(s) and/or mineral fibers are blown, as insulator, in particular without adding binder or water.

Claims

1. A solar thermal collector comprising: a frame having at least one wall forming a back of the collector; at least one circuit configured to transport a heat transfer fluid; and at least one insulator in the form of at least one layer, formed of flakes and/or nodules of one or more mineral wools or mineral fibers, wherein the at least one insulator formed of flakes and/or nodules of one or more mineral wools or mineral fibers is between the circuit transporting the heat transfer fluid and said back wall, and is in contact with the circuit transporting the heat transfer fluid.

2. The solar collector according to claim 1, wherein the collector is a glazed flat-plate collector and comprises at least one glazing unit.

3. The solar collector according to claim 1, wherein the flakes and/or nodules have a size of less than 50 mm, for at least 50% by weight of the flakes, between 5 and 25 mm.

4. The solar collector according to claim 3, wherein the flakes and/or nodules have a size of less than 30 mm.

5. The solar collector according to claim 1, wherein the flakes and/or nodules are made of one or more glass wools or glass fibers, with a micronaire of less than 25 l/min, and/or are made of one or more rock wools or rock fibers, with a fasonaire of greater than 150 mmcw.

6. The solar collector according to claim 5, wherein the flakes and/or nodules have a micronaire between 3 and 18 l/min, and a fasonaire between 200 and 350 mmcw.

7. The solar collector according to claim 1, wherein the insulator further comprises aerogels.

8. The solar collector according to claim 1, wherein the insulator comprises a content of organic compounds of less than 4% by weight, and is free of one or more organic compounds, and the insulator comprises a content of anti-dusting agents of less than 1% by weight, and is free of one or more anti-dusting agents.

9. The solar collector according to claim 8, wherein a content of organic compounds is less than 1.5% by weight.

10. The solar collector according to claim 1, wherein the insulator comprises a binder content of less than 4% by weight, and a water content of less than 2% by weight, the insulator being free of one or more binders.

11. The solar collector according to claim 1, wherein the density of the insulator is between 10 and 100 kg/m.sup.3.

12. The solar collector according to claim 11, wherein the density of the insulator is between 25 and 80 kg/m.sup.3.

13. A process for insulating or manufacturing a solar collector for obtaining the collector according to claim 1, wherein the flakes and/or nodules of one or more mineral wools and/or mineral fibers are blown, as insulator, into the collector.

14. A process according to claim 13, wherein the blowing is carried out without adding binder or water.

15. A process according to claim 13, wherein a flow of blown material comprises, besides the flakes and/or nodules of one or more mineral wools and/or mineral fibers: less than 2% by weight of moisture, one or more additional insulating materials, one or more additives, at less than 1% by weight, for example one or more additives of mineral oil, antistatic and silicone.

16. The process according to claim 15, wherein the flow of blown material further comprises: less than 4% of binder already polymerized or crosslinked or cured or hardened or that has already reacted; and one or more other components incapable of binding the flakes/nodules together and free of water.

17. A process according to claim 13, wherein the flakes and/or nodules have less than 4% by weight of binder, and in that a content of anti-dusting agents in the blown material is less than 1% by weight, the blown material being free of one or more anti-dusting agents.

18. A process according to claim 13, wherein a blowing gas stream is oriented substantially parallel to a mid-plane of a space to be insulated, with an angle of incidence of the blowing stream with said plane of between +5 and 5, a blowing flow rate additionally being of the order of 50 to 200 g/s, and/or a blowing gas pressure being between 70 and 500 mbar.

19. A blowing device for the implementation of the process according to claim 13, and suitable for insulation of solar collectors, comprising at least one diffuser having an outlet area capable of fitting into at least one portion of an opening that opens onto a space to be insulated, so that a flow leaving the at least one diffuser is essentially parallel to a mid-plane of the space to be insulated.

Description

(1) The manufacture of the collectors according to the present invention is simultaneously illustrated, in a nonlimiting manner, in the appended drawings, in which:

(2) FIG. 1a represents a schematic partial view of a solar collector and of a portion of a blowing device according to the invention which are positioned in preparation for carrying out the blowing of the flakes/nodules of mineral wool(s)/fibers in order to obtain a solar collector according to the invention;

(3) FIG. 1b represents a view of the inside of the assembly from FIG. 1a during the blowing;

(4) FIG. 1c represents, seen from the side with respect to the previous figures, the inside of the assembly from FIG. 1a during the blowing;

(5) FIGS. 2a and 2b represents figures similar to FIGS. 1a and 1b but with a blowing device that has a diffuser with a cross section different to the one illustrated in FIGS. 1a and 1b.

Example 1 According to the Invention

(6) In this example, the collector (1) is formed of a chamber comprising a metal frame (2) formed of extruded and bent aluminum profiles, added to which frame is a back (3) in the form of a metal sheet, for example made of aluminum or aluminum-zinc, the assembly being held by clinching in order to form said chamber, an absorber (4) (cf. FIG. 1c) formed of a copper sheet provided with a selective corrosion-resistant coating is additionally fastened inside the chamber, with the aid of rubber sleeves (for example of EPDM or silicone type, these sleeves not being represented in the figures) mounted in the aluminum frame, this absorber additionally being attached, in particular by laser welding, to a hydraulic circuit (5) (of coil or ladder or grid type) made of copper intended to transport water, the hydraulic circuit facing the back of the chamber and the absorber facing a glass plate (6) that seals the collector on its opposite face (face opposite the one formed by the back), the glass plate (not represented, like the absorber, in FIG. 1b or 2b, for a better understanding, said glass plate covering the absorber that itself covers the hydraulic circuit as illustrated in FIG. 1c) being in particular a 3 mm thick plate of tempered solar glass with a low iron content and being for example fastened to the chamber with the aid of adhesives, the leaktightness between the glazing unit and the chamber being provided for example by a seal (for example made of EPDM, not represented). Starting from the back of the collector (3), there is therefore successively (before addition of the insulator) the hydraulic circuit (5), the absorber (4) and the glass pane (6), the space left between the back and the circuit having a thickness of around 50 mm.

(7) The insulation is achieved as follows according to the invention:

(8) The collector is fastened to a support, for example a vertical support (as illustrated in the figures, the support not being represented), and introduced between the rear plate and the hydraulic circuit/absorber assembly, on one of the small sides (2) of the frame (then directed upwards in the case of the vertically fastened collector), through an opening (7) made that gives access to the space or portion of the collector to be insulated between the rear plate and the coil, is a flat diffuser (8) with a rectangular cross section (for example an outlet area having a width (L) of 50 cm (FIG. 1b) and a depth (e) of 50 m (FIG. 1c), the scale not necessarily being respected in the drawings, in particular FIG. 1c being enlarged for better understanding) or a diffuser with a round cross section (8) or oval cross section (for example having an outlet area with a diameter (D) of 20 mm (FIG. 2b)) of a blowing device, connected, for example by means of a connection sleeve (9) to a blowing machine (not represented) of Fibermaster MK500 reference sold by the company Stewart Energy. The diffuser that can be fitted in is preferentially oriented parallel to the glass plate and to the back of the collector, a single diffuser being sufficient to carry out the desired insulation. In an alternative embodiment, the blowing, in particular in the case of the use of a diffuser with a round cross section, may also be carried out through an opening made in the back (3) or rear of the collector.

(9) The blowing machine comprises a supply of mineral wool flakes, decaking members intended to separate the flakes that are usually sold in sacks or compacted bales, one or more flake-conveying members (or ducts), and a blower which directs a stream of pressurized air into the duct or ducts.

(10) The dry blowing of the flakes/nodules of mineral wool(s)/fibers (10) between the back of the collector and the hydraulic circuit/absorber assembly is carried out until the cavity between said back and said assembly is filled (the flakes also filling in the empty spaces between the undulations of the coil and the absorber), an automatic pressure cutoff occurring for example when the column of flakes (11) reaches the end piece (12) of the diffuser in order to stop the blowing, holes (13) (for example having a diameter of around 10 mm) having additionally been drilled through the uprights of the frame in order to enable the evacuation of the air. All of the holes made through the chamber of the collector (for the blowing and the evacuation of the air) may then be plugged by plugs or pellets made of rubber or silicone or polyamide, etc.

(11) The blowing flow rate used is of the order of 120 g/s, the pressure at the diffuser being close to 200 mbar during the blowing. The distribution of the flakes is carried out homogeneously, the density and the thickness of the layer that are obtained respectively being of the order of 35 kg/m.sup.3 and 50 mm, the flakes used being blowable glass wool flakes sold by the company Saint-Gobain Isover under the brand Comblissimo having a micronaire of 6 l/min, the thermal conductivity value (measured in particular according to the EN12667 standard) obtained being of the order of 35 mW.Math.m.sup.1K.sup.1 for the aforementioned density of 35 kg/m.sup.3, the content of binder and of organic components in these flakes (originating from their manufacture, the blowing being carried out by the dry process) being less than 2%. The thermal resistance R obtained, corresponding to the ratio of the thickness of the insulator to the thermal conductivity , is 1.4 m.sup.2.Math.K/W.

(12) The energy loss from the collector is additionally evaluated by determining the value of the first order loss coefficient a1 in the following manner: the power delivered by the solar collector is given by the following relationship: P=q**Cp*(TsTe), in which q is the flow rate of water passing through the hydraulic circuit (here of the order of 43 l/h.Math.m.sup.2), is the density of the water (set at 1000 kg/m.sup.3), Cp is the specific heat capacity of the water (here equal to 4186 J.Math.kg.sup.1.Math.K.sup.1), Te is the temperature of the water at the inlet of the collector and Ts is the temperature of the water at the outlet of the collector. The efficiency of the collector =(power delivered by the collector)/(solar flux received by the absorber), is measured for various T values, where T is the difference between the average temperature of the heat transfer fluid in the collector and the external ambient temperature, the measurements being made after 5 h of exposure under incident radiation Eo. Moreover, in accordance with the EN12975 standard, the experimental curve of the efficiency may be modelled by an equation of the type: =Fa1(T/Eo)a2(T.sup.2/Eo), in which F is the collector efficiency factor, is the transmission factor of the glazing unit, is the absorption factor of the absorber and Eo is the incident solar radiation (after 5 h of exposure). For simplification, the coefficient F** (optical efficiency of the collector) is taken as equal to 0.8. Moreover Eo=800 W.Math.m.sup.2 with a direct incidence of the luminous flux (the solar flux is measured by a sensor having the same inclination as the collector). The experimental efficiency curve is in the form of a curve which is a function of T, of ordinate at the origin F** (case where T=0). The equation of the curve =f(T) according to the preceding equation is determined by linear regression, by varying the factors a1 (determining the slope of the curve) and a2 (determining the inflection of the slope of the curve), until the modelled curve and the experimental curve are superimposed. The superimposing of the two sets the coefficients a1 and a2, which are respectively the 1.sup.st and 2.sup.nd order loss coefficients.

(13) The first order loss coefficient a1 obtained is 3.12 W/m.sup.2.Math.K.

(14) Moreover, the product obtained is classified A1 in terms of fire resistance (according to the DIN 4102 standard).

Example 2 According to the Invention

(15) The procedure of the preceding example is followed, replacing the blowable glass wool flakes with rock wool flakes sold by the company Saint-Gobain Eurocoustic under the reference Coatwool HP and having a fasonaire of 250 mmcw The results obtained are the following: blown density of 45 kg/m.sup.3; layer thickness of 50 mm (thickness of the cavity as in the previous example); thermal conductivity of the order of 45 mW.Math.m.sup.1K.sup.1; thermal resistance R of 1 m.sup.2.Math.K/W; first order loss coefficient a1 of 3.34 W/m.sup.2.Math.K; and classification A1 in terms of fire resistance.

Reference Example

(16) Instead of blowing the insulating layer as in each of the preceding examples, a melamine foam sold by the company BASF under the reference Basotec is inserted between the back and the coil, this foam being, conventionally used for insulating solar collectors, this foam, with a thickness of 20 mm and a density of 12 kg/m.sup.3, having an undulating profile in order to occupy a larger space between the back and the hydraulic circuit/absorber assembly, the thermal conductivity obtained being of the order of 33 mW.Math.m.sup.1K.sup.1, an additional mineral wool being desirable in order to ensure the insulation of the back of the collector, the melamine foam not filling all the space between the back of the collector and the hydraulic circuit/absorber assembly. The thermal resistance R obtained is this time 0.6 m.sup.2.Math.K/W, the first order loss coefficient a1 being 3.92 W/m.sup.2.Math.K, the insulation performance obtained consequently being worse than in the examples according to the invention.

(17) The classification in terms of fire resistance is moreover much worse (class C).

(18) In the case of the collectors obtained according to the invention, a better leaktightness and an improvement in the thermal performance are thus observed, the insulation also being achieved in a practical manner without dust. Where appropriate, the thermal performance may be further improved by adding aerogels to the flakes, for example granules of aerogels of reference P300 sold by the company Cabot, in a proportion for example of 30% to 60% by weight of the blown material.

(19) The present invention makes it possible to produce a new range of solar collectors that have improved insulation and performance, these collectors possibly being used as solar water heaters (domestic hot water, heating of buildings, either individual or community, etc.), or other applications (heating of swimming pools, of floors air conditioning, etc.).