FR2574912A2 - Solar water heater for heating and storing by the direct passage of water and its method of manufacture - Google Patents

Abstract

The invention relates to a solar water heater for heating and storing by direct passage of the water. The water heater comprises a tank 13 mounted inside an enclosure 12 made of glass in which a high vacuum has been produced. Pipes forming elastic water ducts 30, 31 provide sealed water inlet and outlet passing through the outside glass enclosure. Housings 26 in combination with spacers immobilise the tank 13 in the enclosure 12. The invention applies in particular to the production of domestic hot water using solar energy.

Description

 The present certificate of addition relates to improvements to the solar water heater described in main patent No. 84 00 188 of January 6, 1984.

 It is a solar water heater for heating and storage by direct passage of water without a heat exchanger forming a compact, efficient and economical unit.

 The aim sought after according to the invention is to produce a solar water heater with good efficiency, at low cost, compact, requiring no additional servitude, insensitive to frost, which can be installed with very good performance, indifferently in cold, temperate or tropical.

 The solar water heater, object of the invention, is of the type comprising a storage tank placed inside a transparent enclosure. According to the invention, the storage tank is mounted inside a transparent enclosure which is entirely sealed, resistant to admospheric pressure, an intermediate space of reduced thickness being provided between said tank and the enclosure. in which space a high air vacuum has been created, at least two hydraulic water inlet and outlet connections being provided which connect the storage tank to the outside of the water heater by sealingly passing through it 'enclosure, and at least two series of spacers arranged between the balloon and the enclosure, and located towards the two ends of the balloon maintaining the thickness of said vacuum space.

 Such a general design of the water heater gives the device very large operating advantages over water heaters of the known prior art.

These advantages come essentially from the excellent thermal insulation of the interior balloon housed in a glass enclosure slightly distant from the exterior wall of the balloon and in which enclosure there is a high vacuum. However, such a construction design poses many delicate technical problems which can be resolved under the best conditions in this certificate of addition.

 In particular, in accordance with the present invention, recessed or projecting housings are formed on the internal wall of the external envelope to receive at least some of said spacers. In this way, a setting in rotation in one direction and in translation in both directions of the balloon is ensured inside the glass enclosure, which makes it possible to work together on a lathe when welding the caps closing the ends of the enclosure and also ensures a blockage in translation of the balloon in the enclosure facilitating transport operations.

 According to another characteristic of the invention, at least one bottom of the inner balloon is of concave shape, which facilitates the operations of closing the enclosure around the balloon, and on the other hand, makes it possible to gain in volume of size.

 According to another characteristic of the invention, the water inlets and outlets of the tank are made by elastic connections, which limits the stresses of expansion that can be exerted on the glass enclosure.

 The invention also relates to a method of manufacturing the water heater comprising various successive stages of implementation.

The invention, its advantages and its means of implementation will appear more clearly with the aid of the description which follows, given with reference to the appended drawings in which:
FIG. 1 shows in elevation section and schematically a water heater produced according to the invention,
FIG. 2 is a cross-sectional view taken along line II-II of FIG. 1,
FIG. 3 shows in longitudinal section, lying parallel to its axis and in more detail an alternative embodiment of the water heater,
FIG. 4 is an end view taken along arrow IV of FIG. 3,
FIG. 5 is a sectional view taken along the plane VV of FIG. 3,
FIG. 6 schematically shows three spacers fixed around a balloon according to a preferred embodiment and before introduction of the balloon into the external glass enclosure of the water heater,
FIG. 7 shows a detail of the attachment of a spacer around the balloon,
FIG. 8 shows on a larger scale the detail of one end of a spacer,
FIG. 9 is a top view taken along arrow IX of FIG. 7,
FIG. 10 schematically shows in cross section how the balloon is positioned by means of the spacers inside the enclosure when the balloon is not filled with water,
- Figure It is a view similar to that of Figure 10, but when the balloon is filled with water,
FIG. 12 schematically shows in longitudinal section how the hot water outlet and the cold water inlet are arranged in the tank,
FIG. 13 shows schematically on a small scale how a housing for a spacer can be produced in the wall of the enclosure,
FIGS. 14 and 15 are sectional views taken respectively along the planes XIV-XIV and XV-XV of FIG. 13,
FIG. 16 schematically shows a method allowing the balloon to be placed inside its glass enclosure,
FIG. 17 shows in section the implantation detail of the getter at one end of the balloon,
- Figure 18 shows in more detail and on a larger scale how can be achieved and set up The getter.

 We will first refer to Figures 1 and 2 showing the general construction of a heater designed according to the invention.

 The water heater designated 1 as a whole essentially comprises a general external enclosure 2, transparent, leaktight, resistant to atmospheric pressure, that is to say about 1 bar, and for example made of borosilicate glass. Inside there is a metal balloon 3 serving as a storage tank for rep-ered water 5 (Figure 2) and therefore resistant to corrosion of this and pressure from the water network. Between the outer enclosure 2 and the storage tank 3 there is an intermediate space 4 surrounding the entire tank 3. This space is preferably of substantially constant and reduced thickness, for example of the order of 1 to a few centimeters. A high vacuum, for example of the order of 10 5 bars, was achieved there at the time of manufacture of the balloon.

 In order to keep the thickness of the air space 4 constant, spacers 6, for example metallic, and suitably fixed to the balloon 3 are placed towards the two ends of the balloon.

 The entire water heater 1 can rest on the ground, on a roof or on any support while being placed, for example, parallel to its longitudinal axis by means of two pieces -7 conforming to the external volume of the enclosure 2 on its lower part, it can be strapped on its upper part for better hold. The parts 7 are advantageously placed substantially in the same vertical plane as the spacers 6 so as to take over the storage costs of the ball 3 without any particular effort for the enclosure, the ball 3 forming the supporting beam of the construction.

 The storage tank 3 is coated with a surface 8 absorbing and / or selective for solar radiation over its entire outer surface. This coating can be carried out by painting, immersion in an electrolytic bath or the bonding of an adhesive thin sheet coating.

 Two hydraulic connections are provided, namely a cold water inlet at 9 and a hot water outlet at 10 which open into the storage tank 3 respectively at the two most extreme points diagonally, so as to avoid mixing of hot and cold water and to be drawn off The hottest water in the upper part of the tank 3.

 The water heater 1 can be indifferently placed horizontally in the north-south or east-west axis, or even obliquely on a roof for example, taking care in the latter case that the hot water outlet leads well into the part higher of the balloon.

 By way of example, a water heater in accordance with the invention can be produced from an enclosure 2 made of borosilicate glass, of circular section of 200 mm outside diameter, 5 mm thick and 3.10 m overall length. The storage tank 3 is made of stainless steel or coated black steel, also of circular section of 170 mm outside diameter, 2.5 mm thick and 3 m long. The intermediate spacing 4 is substantially constant, including at the ends and 10 mm thick. The covering 8 can be of the selective self-adhesive film type. In such an embodiment, the water heater would have a storage volume of 66 liters for a surface absorbing solar radiation of 0.50 m2 projected and a useful absorbent surface of 1 , 2 m2 calculated on the basis of three-quarters of the total surface of the covering 8 which is 1.6 m2.

 Also still according to the invention, storage capacities and therefore higher daily hot water production can be obtained by combining several units 1 in accordance with the preceding description.

For example, water heaters of 132 liters or 198 liters of capacity can be produced by combining two or three units 1 on a common base and all the hydraulic connections having been made during manufacture.

 As a selective coating, a coating is used which has a high absorption coefficient and a low emission coefficient E, for example o (between 0.95 and 0.98 and E between 0.12 and 0.25.

 The water stored in the central tank is strongly heated directly in contact with the hot wall of the tank when it receives solar radiation.

The performance coefficients are excellent since the transparent and watertight external enclosure ensures the greenhouse effect, the intermediate space 8 air void canceling any heat exchange by convection or conduction, and the selective coating of the storage tank increase absorption and reducing radiation losses.

 Referring to Figures 3 to 5 we will now describe a mode of. preferred construction.

 In these d-essins, we have identified by numbers increased by 10 units the similar elements of the embodiment of Figures 1 and 2, and we will not re-describe in detail all these elements accordingly.

Compared to the schematic embodiment of FIGS. 1 and 2, the following particular characteristics of the mode of observation will essentially be observed.
realization of figures 3 to 5.

 The spacers 16 are spring blades which have been fixed around the balloon 3 by means of a flexible band 21 suitably tightened at 22 according to conventional techniques for closing packages and cases.

The way of fixing the spacers will appear, moreover
Clearly, when describing Figures -6 to 9. In this way, welding and corrosion problems are avoided on the balloon 3 of the spacers 16.

Two sets of three spacers 16 are provided towards the opposite ends of the water heater. In the
illustrated realization where the balloon is approximately 3 m
Long, the spacers were set at about 250 mm from
each background.

On the other hand, we observe, by examining the
Figures 3 and 5, that one of the spacers identified 16a is
positioned in the glass enclosure -2 inside a
generally U-shaped housing with three branches
23, 24, 25 were formed by local deformation towards
the inside of the wall of the enclosure 2- on a small
thickness e, for example of the order of 3 to 4 mm. In this way the spacer is trapped inside the Housing 26 formed by this U with three branches 23, 24, 25 immobilizing the ball in translation parallel to its axis inside the enclosure 12. This allows also to obtain a blocking of the rotation of the baron 13 prohibiting the latter from rotating in the direction of the arrow 27 relative to the enclosure 12, for reasons which will appear later.

 The bottoms 28, 29 of the balloon 13 have their concavity facing outwards, which has advantages in terms of overall dimensions of the heater and also in terms of manufacturing, as will be seen below.

 In one of the hollow bottoms 28, are housed connection pipes 30, 31 respectively with the cold water inlet 20 and the hot water outlet 19, and the pipes 30, 31 are formed in "tail of pig "producing a flexible outlet junction with the sealed cross-pieces 32, 33 of the enclosure 12. It is indeed necessary to provide for a possibility of expansion of the reservoir 13 with its connection conduits relative to the enclosure 12 while not subjecting the latter only to reduced constraints.

 In 34, 35 there are shown flexible junction tubes for connecting the water heater to the pipes for supplying cold water and for using hot water from the room to be equipped, these flexible pipes having the object of avoiding when the tank is connected to the installation, the glass part of the tank welded to the water inlet and outlet breaks.

At the opposite end of the enclosure 12 we see a getter identified as a whole 36 housed at
The interior of a protuberance 37 of the corresponding bottom 12a of the enclosure 12 and whose implementation and interest will be described in more detail below.

 We will now refer to FIGS. 6 to 9 to show in more detail the construction of the spacers16.

 Preferably, there will be around each end of the banlon three spacers 16 formed by a generally U-shaped leaf spring, having a bottom 38 joined by two branches 40 to two feet 39 wound. The fixing of each spacer is done by a flexible band 21 which passes through two notches 41 formed in the bottom 38, and The flexible band 21 is tightened by means of a clamping device 22 of any known suitable type. In this way the three spacer feet 16 can be suitably distributed at 1200 from each other around the balloon 13 and be securely fastened thereto without it being necessary to call upon any operation such as welding which could alter the wall of the balloon.

 The detail in FIG. 8 shows that, preferably, the leaf spring is wound on itself over at least one complete turn. This allows the rolled-up feet 39 to have sufficient resistance to prevent them from being crushed under the weight of the balloon filled with water.

 Thus, with reference to Figures 10 and 11, we see the positions taken respectively by the ball 13, mounted in the enclosure 12 and separated from it by the spacers 16, when the ball is empty of water (Figure 10) or when the balloon is full of water (Figure 11). In this case the balloon is somewhat off-center (d) coming to bear on, and deform, but nevertheless without crushing them, the two feet 39 of the two spacers 16 mounted in the lower part of the balloon.

 Referring to FIG. 12, we have shown schematically how the hot water outlet 19 and the cold water inlet 20 can be arranged inside the tank 12.

 Given the large length of the balloon relative to its diameter, the cold water pipe 20 is advantageously given a winding path, for example in a helix along the internal wall of the balloon, against which wall it remains wedged. The connections which must pass through the glass enclosure in leaktight fashion (not shown) can be formed, as illustrated by flexible conduits 44, 45 to allow differential expansion between the balloon 13 and the enclosure 12.

 Referring to Figures 13 to 15, there is illustrated the housing 26 formed in the wall of the glass enclosure 12 for receiving and wedging a tab of a spacer 16. The introduction of the tab into the spacer is done by bringing the tab in the position marked in a near the entrance to the housing 26, then pushing it up to the height of the entrance to the housing in b, and then rotating the balloon 13 (whose tab is integral) inside the enclosure 12 until the tab comes into c to lock at the bottom of the housing 26.

 The principle of placing the balloon 13 in the enclosure 12 will now be described in more detail, with reference to FIG. 16.

 It will first be assumed that the enclosure 12 is already partly made with a bottom 12b already welded.

(We will describe below all the successive operations to be implemented for the complete manufacture of a water heater).

 The balloon 13, equipped with its hot and cold water outlets, such as for example 44, 45, is threaded inside the enclosure 12, being gripped by its bottom 29 by means of a suction cup 46, connected by a conduit 47 to a vacuum pump, as indicated by the arrow 48.

 The legs 16 of the spacers are temporarily folded against the wall of the balloon 13 by a flexible link (not shown) until the legs are engaged in the opening of the enclosure 12. The external flexible link is then removed and the 'assembly is advanced, as indicated by arrow 49, until the second set of legs 16 are also engaged in the opening. We then continue to push the entire balloon 13 until the legs 16 come up to the height of the housing 26. At this time, we rotate the balloon 13 in the direction of the arrow 50 to make the leg d 'corresponding spacer in the housing 26, as had been explained in relation to Figures 13 to 15.

 We will now refer to Figures 17 and 18 explaining the use of the getter.

 As is well known in the high vacuum technique, the vacuum can be perfected inside an enclosure by vaporizing certain elements therein when an already relatively high vacuum has been established.

For example, it is thus possible to vaporize barium in an enclosure in which a reactive vacuum of the order of 10 4 bar has been made, so as to bring this vacuum to a higher value, for example, of the order from 10 6 bar. In addition, the "flashing" of barium on the pa
neighboring kings in the enclosure glass creates a color
reflective silver forming a vacuum witness. Indeed, -in the event of a leak and introduction of air into the enclosure,
the oxygen-hungry barium oxidizes and turns whitish.

The barium can be vaporized by means of an electrical winding 51 which will heat the vaporizable substance of the getter 36
when an induction choke 52 (FIG. 17) will be applied to the outside around the winding 51. The practical assembly can be done as illustrated in FIG. 18 by providing the winding 51 for supplying a heating resistor making it possible to heat resistors 53 on which the barium has been previously deposited,
the winding 51 being formed on a small cylinder in
glass 54, itself welded to the bottom of the housing 37 also
glass, itself welded to the cap 12a.

We will now describe in relation to the various
figures the various successive operations which must
be made to make the water heater.

Glass cylinders are produced separately
constituting the main part of enclosure 12, for
before having for example an outside diameter of 200 mm and a wall thickness of 5 mm, so that
resist crushing atmospheric pressure
when the enclosure is evacuated.

The end caps such as 12a, 12b are also produced separately, which must cover and close the enclosure 12. The cap 12b must include
(Figure 16) two glass tubes 55, 56 into which the water inlet and outlet pipes 44, 45 of the balloon will engage. This cap may also include a third glass tube 57 through which the vacuum will be created in the enclosure.

Balloon 13 is produced separately, the outside diameter of which is slightly smaller than the inside diameter of the enclosure. For example, the outside diameter of the balloon can be of the order of 170 mm. It is made, preferably of steel - and it must be able to resist the pressure of calibration of the water
(generally 9 bars) increased by a bar corresponding to the vacuum created in enclosure 12.

 The tank 13 is equipped with its bottoms and its water inlet and outlet conduits with its flexible connections. Two pipes 44, 45 project at one end to exit through the tubes 55, 56 of the cap 12b.

The enclosure 12 also comprises, which can be hollowed out or in relief on its internal wall,
the housing 26 for wedging at least one spacer 16 or one of its feet 39.

 The cap 12b is welded to the tube 12.

 The balloon 13 is fitted with its series of spacers 16 which are kept tight by a temporary flexible strip.

The balloon 13 is introduced by axial translation into the enclosure 12, releasing the flexible strip when
the spacers have entered the cylinder, which allows the bat ton 13 to be properly engaged with its spacers 16 in the enclosure 12 without scratching it (which could weaken the glass).

When the balloon 13 is properly engaged in the enclosure 12, it is slightly rotated on
itself, as illustrated in FIG. 16, the balloon 13 in the enclosure 12 so as to block the corresponding spacer in the housing 26. At the same time, we took the precaution of bringing out the flexible pipes '44, 45 by the tubes 55, 56 of the cap 12b
The balloon 13 is thus suitably positioned and wedged in the enclosure 12, it is possible to remove the flap 46 having served for its introduction, and the other cap 12a can be put in place than the one for
ra weld to the adjoining wall 12 of the enclosure by rotating the entire water heater on a lathe to achieve a good weld and uniform heating of the cap on the enclosure 12. The concave bottoms of the ball allow '' avoid overheating phenomena which could be harmful in particular to the particular absorbent coating of the balloon. On the other hand, the getter 36 being protected in its housing 37 is also not subject to untimely overheating during the operation of closing the enclosure by welding the cap 12a.

 When these operations are completed, the enclosure is started to evacuate by the tube 57 connected to a suitable source of vacuum. Simultaneously, the tubes 55 and 56 are welded around the cold water and hot water outlet pipes 44, 45. This welding is carried out by simple heating of the tubes 55, 56 which, due to the vacuum produced in the enclosure, are crushed against the tubes 44, 45. A vacuum is maintained, for example of the order of 10 4 bar while heating the whole for example around 300 "C in an oven for 3 to 4 hours, so as to avoid degassing over time.

 After which, seal the vacuum tube 57 and proceed with flashing - vaporization of the getter for perfect vacuum up to 10 6 bar. Maintaining the silver color of the barium vaporized on the adjacent walls of the enclosure is a guarantee of maintaining the vacuum.

 Many alternative embodiments can be made to the modes of construction, mounting and manufacturing described. In particular, a number of operations can be reversed and the various solutions recommended and described can be combined.

 For example, when welding the glass caps at the two ends of the enclosures, heating ramps can be used to avoid having to rotate the entire enclosure and the storage tank on itself.

 In general, the use of synthetic and plastic materials will be prohibited inside the vacuum chamber, because these materials degas over time and would drop the performance of the device. The materials used will therefore be essentially metallic such as steel, copper, etc.

 Likewise, the external absorbent coating of the balloon must be able to withstand the heating of the assembly process of the assembly and the steaming at the end of the degassing operation.

 On the level of the outer feet 17, on the other hand, flexible plastics such as PVC can be used which will reduce the stresses with the glass and will also ensure a reduction at this location of the thermal bridge created by the presence of the spacers, the conductivity of which is very limited.

 Given its design, the ball can be placed in any orientation. If use in a vertical position is planned, it is then advantageous to add, on the side at least of the balloon which will be placed at the bottom, a mattress of absorbing glass wool which will allow the balloon to be supported inside the enclosure. by resuming the load mainly on the lower cap which will obviously be properly received in a suitable cradle.

Claims (12)

 1. - Improvements to a solar water heater according to any one of the claims of the main patent and in particular claim 1, that is to say comprising a storage tank (3) placed inside an enclosure transparent (2) for solar radiation, said enclosure (2) being entirely sealed, resistant to atmospheric pressure, an intermediate space (4) of reduced thickness being provided between said balloon and the enclosure in which a vacuum a-ir pushed was made, at least two hydraulic connections, 10) inlet and outlet of water being provided which connect the storage tank to the outside of the water heater by crossing tightly l 'enclosure (2), at least two series of spacers (6) being arranged between the balloon (3) and the enclosure (2) and located towards the two ends of the balloon maintaining the thickness' of said vacuum space, characterized in that recessed or projecting housings 26 are formed on the internal wall of the outer casing to receive at least some of said spacers (16a).  2. - Improvements according to claim 1, characterized in that at least one bottom (28) of the inner balloon (13) is of concave shape.  3. - Improvements according to claim 1 or claim 2, characterized in that the water inlet and outlet (19, 20) are made by elastic connections (30, -31, 44, 45).  4. - Improvements according to claim 3, characterized in that the water inlet and / or outlet are made by non-rectilinear connections.  5. - Improvements according to claim 3 or claim 4, characterized in that the inlet and the outlet are made towards your opposite ends of the ball 63) the pipe (20) which crosses the ball over almost its entire serpentine length, for example by helicopter, inside the balloon.  6. - Improvements according to one of the preceding claims, characterized in that the spacers (16) have the form of springs and are held on the outer wall of the balloon by means of flexible ties (21) suitably stretched.  7. - Improvements according to claim 6, characterized in that said springs (16) have the form of blades wound on themselves at their ends (39).  8. - Improvements according to one of the preceding claims, characterized in that the enclosure (12) has at one of its ends, in its axis a  circular cylindrical housing (37) of reduced diameter communicating with the vacuum space (14) between the enclosure and the balloon and the wall of which is formed from a material similar to that which constitutes said enclosure, said housing being susceptible to contain a getter (36).  9. - Improvements according to claim 8, characterized in that said getter comprises a barium tablet and an electric coil (51) of vaporization  C "flashing") capable of being supplied by means of an external induction flow.  10. - Improvements according to claim 8 or claim 9, characterized in that said getter is mounted on a screw (54) made of glass fixed inside said housing (37).  11. - A method of manufacturing a water heater according to any one of the preceding claims, characterized by The following steps  Glass cylinders and end caps (12a, 12b) are produced separately to form said enclosure (12),  On the internal wall of the glass cylinder, hollow or protruding housings (26) are formed for receiving the ends of said spacers i? 3),  A balloon with an outside diameter smaller than the inside diameter of the enclosure is produced.  on the order of a few centimeters, preferably 1 to 3 cm below,  This balloon (13) is fitted with its flexible water inlet and outlet pipes (30, 31, 44, 45) with two ends projecting out of the balloon towards a longitudinal end of the balloon,  An end cap (12a) is provided with two glass tubes (55, 56) of diameter slightly greater than said two ends of pipes (44, 45) and which are positioned so as to be able to receive them,  Said cap (12a) is welded to one end of said glass cylinder,  The balloon (13) is fitted with its series of spacers (16) which are kept tight by a temporary flexible band,  The ball is introduced by axial translation into the enclosure, releasing the flexible strip that the spacers have entered the cylinder,  The ball is rotated in the enclosure to bring at least some of the spacers (16a) into abutment in their housing (26) formed on the internal wall of the cylinder,  We weld the second cap on said cylinder,  A vacuum is created in the space (14) between the balloon and the enclosure by means of a glass tube (57) passing through one of the caps,  The two aforementioned glass tubes (55, 56) are closed in leaktight fashion on said pipe ends (44, 45) which they surround by heating them locally, and  The vacuum tube (57) of said space (14) is sealed.  12. - Method according to claim 11, characterized in that perfect vacuum by vaporization ("flashing") of a getter in the enclosure.