FR2514477A1 - Solar heat collector with hot water storage - has primary circuit steam pressure-pump in heat storage pressure vessel - Google Patents

Abstract

The solar collector comprises an inclined flat-plate absorber (1) mounted on an insulated storage vessel (8) with a secondary water inlet (18) and an outlet (17). A steam pressure pump is located above the panel and has a lower vessel (3) and an upper vessel (4). The upper volumes of both vessels are interconnected by a pipe (6) containing a valve (5) operated by a float (7) in the upper vessel. The lower volumes of the vessels are interconnected by pipes (9-11) to form a closed circuit containing a heat exchanger (2) within the vessel (8).

Description

 The present invention relates to an apparatus for the preparation of domestic hot water from the heat supplied by a flat solar collector, the collector, the pump and the storage tank being combined in compact form.

The simplest systems for the preparation of domestic hot water comprise a flat collector and a storage tank situated just above the flat collector, the heat exchange between the collector and the said tank being made by thermosyphon. These systems have several disadvantages
- the whole device is not aesthetic and is difficult to integrate into the architectural environment
the stability of the device is poor because the heaviest element (the tank 3 is located at the top,
- the wind resistance is not always good,
- The efficiency of the sensor is reduced because the speed of circulation of the liquid in the absorber is lower than in an installation having a forced circulation of the heat-transfer liquid.

 There are also known devices for the preparation of domestic hot water comprising a flat sensor and a storage tank located at the same level as the flat sensor and placed in the space available at the rear of the sensor, in these devices the transfer of heat between the sensor and the tank is generally provided by an electric pump controlled by an electronic regulation ensuring the starting of the pump when the heating of the water of the tank is possible.

These systems have the disadvantage of being dependent on the power supply network and have a significantly higher cost price than thermosiphone devices.
There are also known installations consisting of a solar collector and a hot water storage tank comprising a heat exchanger, the exchanger and the absorber of the collector constituting a primary circuit containing a fluid in liquid-vapor equilibrium, 1 heat exchange between the insolator and the tank exchanger by vaporization and condensation (heat pipe); these installations do not perform satisfactorily when the solar collector and the tank are located at the same level because the reverse exchange is possible: the collector cools the tank overnight.

The device object of the present invention has the advantages of a compact system comprising a forced circulation produced by a pump: aesthetics, stability, high efficiency, while being autonomous, reliable and of a low cost price.
This device comprises in association izn ccpteur salary plan, a hot liquid storage tank Sitl≈ at the same level as the said sensor in the space available at the rear of the sensor and comprising a heat exchanger. an autonomous pump for circulating a coolant e vapor vapor balance in the primary circuit of the installation consisting of the sensor, the exchanger of the storage tank and the said pump. This pump uses the difference between the vapor pressure of the part of the fluid in contact with the absorber of the solar collector, and the vapor pressure of the fluid in contact with the exchanger of the storage tank, to cause circulation. installation fluBes.

 In a preferred embodiment, the reservoir has a flat face placed against the rear face of the insolator so as to reduce the volume and to benefit from the thermal insulation of the sensor to isolate part of the surface of the reservoir, this position also gives better stability to the whole and increased wind resistance.

The pump consists of the following elements
- a first chamber which communicates with the upper part of the absorber of the solar collector,
a second chamber which is situated at a higher level than that of the first chamber, which chambers contain a mixture of the liquid and vapor phases of said fluid,
- a pipe which connects the upper part of the first chamber to the second chamber, and which is equipped with an automatic valve.

 - A circuit which connects the lower part of the first chamber to the second chamber through the exchanger of the hot liquid storage tank.

 the operation is as follows: when the level of the liquid-vapor interface reaches an upper threshold in the first chamber (or a lower threshold in the second chamber), the automatic valve closes and the vapor pressure increases in the first chamber and expels the liquid to the second chamber through the exchanger of the storage tank, the temperature of the liquid drops during this transfer, and when the level of the interface in the first chamber reaches a lower threshold (or when the level reaches an upper threshold in the second chamber), the automatic valve opens causing an equalization of the vapor pressures of the two chambers and the liquid flows from the second chamber to the first under the action of gravity, and when the level of the interface in the first chamber again reaches the upper threshold, a new cycle begins again and the heat transfer fluid circulates transporting calories from the insulator to the r storage tank.

 The positions of the absorber of the solar collector and of the exchanger of the storage tank are not symmetrical in the primary circuit of the installation, therefore heat exchange takes place in a privileged manner. towards 1 exchanger of the storage tank and the reverse exchange is very reduced.

This property will be highlighted in the following description referring to the appended drawings which represent, without any limiting character, examples of embodiment of devices and circuits constructed according to the present invention.

 - Figure I shows schematically a first embodiment of a solar water heater according to the invention.

 - Figure 2 schematically shows a second embodiment of a solar water heater according to the invention in which the liquid has a unidirectional movement.

 - Figure 3 shows in more detail a circulation pump corresponding to the device presented in Figure 2.

 the solar water heater represented by FIG. I comprises a flat solar collector provided with an absorber I and with insulation 16 on the rear face, it also comprises a hot liquid storage tank 8 provided with thermal insulation I5, a cold water inlet I8 and a heated water outlet 17, it finally comprises a pump consisting of a first chamber 3, a second chamber 4 located above the first chamber and an automatic valve 5 controlled by a float 7 immersed in the liquid of the upper chamber 4.

 the upper parts of the chambers 3 and 4 communicate with each other through a pipe 6 provided with the automatic valve 5. A circuit consisting of the portions 9, IO and It connects the lower parts of the two chambers 3 and 4 through the absorber I and the exchanger 2. the chambers 3 and 4 interconnected by the pipes 6, 9, IO, II form a closed circuit which contains a constant quantity of fluid which is in the liquid and gaseous state.

 The device also includes a support 19 ensuring stability on a horizontal plane. the assembly consisting of the solar collector, the storage tank and the pump is contained in the space between two planes forming a dihedral angle less than 300 so that it is possible to place it directly on a roof having a slight slope . For steep roofs, incorporation into the roof is possible, only the pump then protrudes from the roof.

the operation of the pump of the device shown in figure I is as follows
At the start of the cycle the valve 5 is closed and the chamber 3 contains a lot of liquid and little steam. the liquid contained in the chamber 3 communicates with the absorber, hot source. It heats up and the vapor pressure increases in the chamber 3, the liquid is expelled by the pressure through the conduit 9, the absorber I and the exchanger 2. It cools down by passing through the exchanger and fills gradually the chamber 4. As the liquid contained in the chamber 4 is at a lower temperature, the vapor pressure is lower there than in the chamber 3 and the liquid circulates under the effect of the difference between the vapor pressures. heat supplied by the hot source is partially transferred to one exchanger of the storage tank and partly transformed into potential energy of the liquid which is discharged to a higher level.

 when the liquid level reaches an upper threshold in the chamber 4, the float 7 controls the opening of the automatic valve 5, which puts in direct communication the upper parts of the two tanks through the pipe 6. These two tanks then form two communicating vessels and the liquid contained in the reservoir 4 flows, by gravity to the reservoir 3 through the pipe II, IO, 9 until the level of the liquid interface. vaDeur reaches a lower threshold in the chamber 4 which is detected by the float which controls the closing of the valve 5, and a new cycle begins again.

 It should be noted that 1 liquid contained in the chamber 4 heats up at the opening of the valve 5 by bringing it into contact with the steam coming from the chamber 3, it is therefore a heated fluid which returns to the cold source by pipeline II.

 when the absorber of the insolator becomes colder than the hot liquid stored in the tank 8, the vapor pressure in the chamber 3 is lower than the vapor pressure in the chamber 4 which communicates with the exchanger 29 of this makes the chamber 3 fill with liquid, the chamber 4 then contains little liquid and the valve 5 controlled by the float 7 is closed, this position is stable; 1 n3y therefore there is no vapor exchange between the chambers 3 and 4; the heat exchange between the absorber I and the exchanger 2 via the conduit IO is very weak taking into account the low position of the conduit TO.

Thus the reservoir 8, the chambers 3 and 4 and the conduits II and being suitably insulated, the reservoir 8 retains the stored heat when the temperature of the absorber I becomes lower than the temperature of the liquid stored in the reservoir 8.

 The tank 8 has been shown in Figure I as a receiver with a single exchanger, and in which the heat is stored thanks to the specific heat of the water, but it is possible to store the heat by changing its state a solid body, the latent heat being restored during solidification, in this case the tank would contain a second exchanger leading to the fittings I7 and 18 of the sanitary hot water installation. the reservoir 8 may also include an electrical resistance associated with a thermostat for freezing the instance. the fluid of the primary circuit advantageously consists of water mixed with a more volatile fluid, for example ethe and alcohol, which makes it possible to increase the vapor pressure and lower the freezing temperature.

It is clear that a substantially equivalent operation could be obtained by controlling the automatic valve 5 by a float immersed in the liquid of the chamber 3, in this case the automatic valve 5 should close by the rise of the float beyond a certain threshold, and the descent of the flatterer would open the automatic valve 5. The advantage of the arrangement of the figure
It is to allow the liquid to be completely emptied from the chamber 3, when the automatic valve 5 closes, which is possible if the volume of the chamber 4 is greater than that of the chamber 3.

 It is also possible to change the levels of the mouths of the conduits II and 6 in the reservoir 4 without departing from the scope of the invention.

 FIG. 2 represents another embodiment of the invention which differs by the circuit of the circulating pump, the other elements being similar. In the embodiment according to FIG. 2, the flow of the liquid between the absorber and the exchanger of the storage tank is anidirecfiio * unel. and the absorber is constantly traversed from bottom to top, which ensures a more satisfactory heat exchange between the insulator and the hot water reserve.

 the parts homologous to those of FIG. I are represented by the same reference mark followed by the index a.

 The difference in altitude between the levels of liquids in chambers 4a and 3a is sufficient for the corresponding static pressure to allow the liquid to overcome the resistance of the non-return valve I3, placed on the conduit I2 connecting the bottom of the upper chamber at the hot spring. The direction of the valve I3 is such that the liquid from the upper reservoir can flow only in the direction of the hot source. The bottom of the lower chamber is connected to the exchanger 2a by means of a valve I4 which allows the liquid to flow only in the direction of the cantor 3a towards the exchanger 2a. The conduit IIa connects the lower part of the cold source to the upper part of the reservoir 4a.

 One of the chambers, preferably the chamber 3a, comprises a float controlling the automatic valve 5a, which closes when the float reaches a high threshold and opens when it reaches a low threshold.

 The second chamber 4a has a volume greater than the first so as to be able to absorb the additional volume due to the expansion of the liquid with the temperature without the operation of the installation being disturbed.

The operation of the apparatus according to FIG. 2 is as follows
At the start of the cycle, the chamber 3a is filled with liquid up to the high level of the float. By the fact of the communication with the hot source, the liquid heats up and the pressure increases in this chamber 3a, which causes the hot liquid to explode through the valve I4 towards the exchanger of the storage tank. Thus it is liquid having the temperature of the hottest parts of the absorber Ia which reaches the exchanger 2a, therefore the inertia on start-up is lower than that of the device of FIG. .

 The liquid, after having been cooled by passing through the exchanger, progresses through the conduit IIa and opens into the upper part of the chamber 4a where it condenses the vapor. This condensation is favored by the presence of a spray device 20, which causes a suction effect favorable to the flow of the liquid. The valve 5a opens automatically when the float level reaches the lower threshold.

 The equalization of the vapor pressures in the two chambers, following the opening of the valve 5a, causes the liquid to flow from the upper chamber to the absorber and the lower chamber through the conduit I2 and the non-return valve. return I3; when the float in the tank 3a reaches the upper threshold a new cycle begins again.

 Unlike the device in FIG. I, on a device conforming to FIG. 2, the volume of the chambers 3 and 4 can be much less than that of the pipes and that of the absorber and of the exchanger by the fact that the circulation is unidirectional and by the fact that the liquid travels the absorber from bottom to top, the liquid expelled through the valve 14 is thus at high temperature.

 FIG. 3 schematically represents an embodiment of a pump fitted to a device such as that of FIG. 2 comprising two chambers, a valve automatically controlled by a float, two valves and members intended to purge the circuit or to improve the condensation vapors in the upper chamber when the controlled valve is closed.

 In this FIG. 3, the elements homologous to those of FIG. 2 are designated by the same reference mark followed by the index b.

 The device has four threaded ends, the ends 41 and 43 are intended to be connected to the insulator, the connections 42 and 44 are to be connected to the cold source exchanger. The nozzle 41 has been placed in the middle of the reservoir 3b to reduce the total height of the device which projects above the insulator to which it is intended to be connected.

 The relative dimensions of the various elements of FIG. 3 have not been respected, in particular the automatic valve Sb has been enlarged to allow its constituents to be represented.

This valve comprises a valve 27, articulated around an axis of rotation 28, a spring 29 is fixed to the valve and to an anchoring point 30, so that this spring is slightly compressed. The positions of the spring anchor points are such that the valve has two stable states in its rotation around the axis 28.

In one of these states, the valve closes the seat 31 located at the top; in the other stable state, the valve is open.

 the valve 27 is linked to a rod 32 by a hinge pin 33, parallel to the axis 28, so that the upward and downward movements of the rod respectively cause the valve to open and close. The rod 32 carries those stops 35 and 36.

 The reservoir 3b contains an annular float 34 which can slide freely around the rod 32 between the two stops 35 and 36.

 The operation is as follows; . when the level of the liquid rises in the reservoir 3b, the float 34 comes to bear against the stop 35, the Archimede push on the float causes the valve 27 to rise which is applied to the seat 31. After closing of the valve, the thrust exerted by the spring 30 keeps the valve closed, the rise in pressure in the reservoir 3b is favorable to this closure.

 In the device shown in Figure 3, when the liquid level drops in the cylindrical tank 3b, the float 34 slides on the rod 32 and finally comes to rest on the stop 36, and when the liquid level continues to drop, the weight apparent of the float believes and it ends up driving down the rod 32 and the valve 27.

 A spray device 40 is located at the upper end of the conduit IIb into which the liquid from the cold source arrives. This spraying device is intended to promote contact between the cold liquid entering the tank 4b and the vapor contained in the same tank. This result is obtained by a very light valve 45 terminating the conduit IIb, this valve need not be perfectly sealed. It opens to the passage of the liquid and increases the speed of ejection of the liquid, this is especially noticeable for low liquid flow rates, the liquid thus being able to reach the entire volume of the reservoir 4b whatever the flow rate. The mobile spraying member 45 could be produced in other equivalent forms.

 the conduit 6b connecting the automatic valve 5b to the upper part of the reservoir 4b, comprises a manual valve 46 and a thermal insulator 47. This conduit enters through the lower part of the reservoir 4b in order to make the entire apparatus more compact.

 The thermal insulator 47 reduces the heat exchanges between the liquid contained in the reservoir 4b and the conduit 6b the other elements: reservoirs, conduits, are also covered externally with a thermal insulator which has not been shown so as not to overload the figure.

 The manual valve 46 and the manual vent valve 37 allow an easy purging of the air contained in the installation, during the first start-up, without the need to use a vacuum pump: the installation is at previously filled with liquid through the filling orifice 39 until liquid appears in the reservoir 4b, the cap 39 and the manual valve 46 are then closed and the trap 37 is opened, the pressure increase in the source hot and in the reservoir 3b provorlur the expulsion of the liquid from this reservoir and a part of the liquid from the pipe leading to the cold source, this expelled liquid fills the reservoir 4b and the trap 37 is closed when this reservoir is full of liquid. The valve 46 can then be definitively opened, the installation then being purged of the air that it contained.

 As a variant, the purging operation could be carried out by manual control of the valve 27.

 The tank 4b also carries a safety valve 38.

 In the event that the installation has a micro-leak, air can enter the circuits when the installation is in depression by the drop in temperature of the hot source.

When the hot source rises in temperature, the pressure increases throughout the circuit and the air contained in the circuit can escape through the valve38, when the pressure is sufficient; the departure of this air then allows the installation to operate normally.

 The entire apparatus is contained in a protective enclosure 48. the valves I3b and I4b are preferably of the swing type.

Claims (9)

 WTV7FjiNlTCATOS  - an autonomous pump for circulating a heat-transfer fluid in liquid-vapor equilibrium in the primary circuit of the installation consisting of the absorber of the solar caftor, the exchanger of the storage tank and the said pump which uses the difference between the vapor pressure of the part of the fluid in contact with the said absorber, and the vapor pressure of the fluid in contact with the said exchanger, to cause the circulation of the liquid of the installation.  - an insulated hot liquid storage tank located at the same level as the said sensor in the space available at the rear of the sensor, and comprising a heat exchanger, a cold water inlet and an outlet warm water,  - a flat solar collector  I. Device for the production of sanitary hot water characterized in that it comprises in association; ion  2. Device according to claim I characterized in that the hot liquid storage tank has a plant face which is placed against the rear face (not exposed to the sun) of the solar collector, so that the volume of the device is thus reduced, and the insulator's thermal insulation partially isolates the hot liquid storage tank.  3. Device according to claim I characterized in that the pump for circulating the heat transfer fluid comprises the following elements  - a first chamber (3) which communicates with the upper part of the absorber of the solar collector (I),  - a second chamber (4) which is situated at a higher level than the first chamber, which chambers contain a mixture of the liquid and vapor phases of said fluid,  - a pipe (6) which connects the upper part of the first chamber to the second chamber, and which is equipped with an automatic valve (5),  a circuit which connects the lower part of the first chamber to the second chamber through the exchanger of the hot liquid storage tank.  4. Device according to claim 3 characterized in that the said automatic valve (5) is controlled by a float (7).  5. Device according to claim 3 characterized in that the lower part of the first chamber (3a) is connected to the second chamber (4a) by a circuit comprising a first non-return valve (I4) and the tank exchanger d hot water (2a) and a conduit (IIa), that the bottom of the second chamber (4a), is connected to the lower part of the absorber (la) by a pipe (12) equipped with a second valve no return (I3), and the upper part of the absorber (Ia) is connected to the bottom of the first chamber (3a), so that when the said valve (5a) is closed, the pressure increases in the chamber lower, and the liquid flows to the upper chamber (4a) through the exchanger (2a) and when the said valve is open, the liquid from the upper chamber (4a) flows by gravity to the lower chamber (3a) through the absorber (Ia).  6. Device according to claim 4 characterized in that the said automatic valve comprises a valve 27 which cooperates with a seat (31), which valve is articulated around an axis (28), and a spring (29) which is fixed to said valve (27) and to an anchor point (30) whose position is such that said valve has two stable states, one applied against the seat (31) and the other open.  7. Device according to claim 3 characterized in that the pipe (6b) which connects the upper part of the first chamber to the second chamber comprises a manual shutter device such as a manual valve (46) and in that it includes an air vent (37) placed at the top of the second chamber (4b), so that the air in the installation can be purged by closing the said manual valve (46).  8. Device according to any one of claims 3 to 7 characterized in that the pipe (IIb) which connects the exchanger to the upper chamber (4b) opens into the upper part thereof containing the vapor phase and leads to its upper end a spraying device (40), for example a flap valve (45).  9. Device according to any one of claims 2 to 7 characterized in that the upper chamber (4b) comprises a safety valve (38).