FR2519384A1 - Thermal pump for heating circuit - has three interconnected pressure vessels and three-way valve between solar panel and water tank - Google Patents

Abstract

The heating circuit has a heating source solar panel and a cold source domestic water cylinder. A header vessel is connected into the hot source with a higher vessel connected to the cold source. An intermediate vessel has a three-way valve which connects with the steam space of the other vessels. When the water in the header vessel is heated, the increase in pressure causes water to flow from the cold source to the upper reservoir. The three way valve connects the steam spaces of the upper and intermediate vessels, therefore water flows by gravity into the intermediate vessel.

Description

 The subject of the present invention is a method and devices allowing the circulation of a heat-transfer liquid autonomously in a closed circuit connecting a hot source to a cold source, in order to ensure a heat exchange between these sources. I1 is known methods for circulating a heat transfer liquid independently between a hot source and a cold source, such a method has been described in the European patent published sus nO 38769.A2.In these pumps the circulation of the heat transfer liquid occurs in two stages: in the first stage the liquid circulates from a lower tank communicating with the hot snurce towards an upper tank by crossing the cold source, during the second time the liquid flows by gravity from the tank higher than the lower tank by crossing the hot spring thanks to a balancing between the vapor pressures of the two tanks.

 In these previous pumps, the circulation of the heat transfer liquid between the hot source and the cold source is not regular but pulsed and generally discontinuous; on the other hand the balancing between the vapor pressures of the two tanks in the second time causes a cooling of the hot source and a heating of the upper tank without the cold source being heated; this parasitic heating of the upper tank is unfavorable for the circulation of the heat transfer liquid in the first stage of operation, and impairs good heat exchange between the sources.

 The process and the devices which are the subject of the present invention do not have these drawbacks: the flow of liquid from the hot source to the cold source is continuous and there is no balancing between the vapor pressures of the upper and lower tanks; so that the flow of the liquid circulating between the hot source and the cold source is greater, for a given fluid and given source temperatures so the remote heat exchange between the hot and cold sources is better ensured than in previous systems.

 Another objective of the present invention is to propose devices making it possible to avoid the entry of air into the circuits of the heat-transfer fluid when the temperature of the fluid becomes lower than the boiling temperature under atmospheric pressure.

 These objectives are achieved by means of a method for circulating a heat transfer fluid in a closed circuit comprising a hot source, a cold source, a first closed tank in communication with the hot source, the part of the first tank containing the liquid phase communicated by a pipe crossing the cold source, with a second tank located at a level greater than or equal to that of the first tank. The entire installation is closed and contains a fluid in vapor-liquid equilibrium. I1 prevails in the second tank receiving the liquid from the cold source a pressure lower than that of the vapor phase of the first tank communicating with the hot source, so that the liquid contained in the first tank, is circulated in the pipe crossing the cold source, and the level rises in the second tank while it drops in the first, the liquid accumulating in this displacement of mechanical energy. The return of the liquid from the second tank to the first is obtained by a device constituted a chamber having an intermediate level between that of the two reservoirs, and pipes connecting the said chamber to each of the two reservoirs, the said pipelines comprising automatic shutter systems which will be described later.

 said intermediate chamber is alternately placed in communication with the second tank, then with the first.

the level of the liquid being higher in the second tank, when it is placed in communication with the second re-tank; said intermediate chamber fills with liquid by gravity, it empties of the liquid it contains and fills with vapor when it is placed in communication with the first reservoir. Thanks to an indirect communication by the intermediate chamber, the pressures of the two tanks do not balance when the liquid returns from the second tank to the first, so that the flow of liquid from the first to the second tank, through the cold source is continuous, under the action of the difference between vapor pressures; when the flow of liquid passing through the cold source increases, the difference between the liquiaes levels in the two tanks also increases, and the flow of the circuit passing through the intermediate chamber also increases ........... .................

 the devices according to the invention, being autonomous, can operate in isolated sites, without any contribution of mechanical or electrical energy. They find application in particular in installations using solar radiation as a hot source, for example in solar water heaters or in installations for producing cold from solar energy using absorption or adsorption phenomena, in thermal engine cooling systems in which the hot source is the cylinder block and the cold source the radiator, in domestic heating systems with heat transfer liquid, and more generally in all remote heat transfer systems with heat transfer liquid.

 Other advantages of the invention will be highlighted in the description which follows. Figure I shows a first device for implementing the method in which the intermediate chamber is a closed tank, Figure 2 shows an exemplary embodiment of this device.

 FIG. 3 represents an installation in which several hot springs and several supply devices operating in parallel.

 the device represented by FIG. I comprises a hot source I and a cold source 2. I1 also comprises a first closed tank 3 communicating with the hot source, a second closed tank 4 situated at an altitude greater than or equal to that of the first tank, and a chamber 5 situated at an intermediate level between the levels of the reservoirs 3 and 4.

These three chambers 3, 4 and 5 contain a liquid in phase equilibrium with its vapor.

The upper part of the intermediate chamber 5 comprises a three-way valve 6 which is connected by a conduit 7 to the upper part of the reservoir 3 and by another conduit 8 to the reservoir 4. The three-way valve 6 connects the part upper of the intermediate chamber 5 either with the upper part of the tank 3 in one position, or with the tank 4 in another position.

 The lower part of the chamber 5 containing the liquid communicates with the lower part of the reservoir 4 via the conduit 9 carrying a non-return valve I0, the lower part of the chamber 5 also communicates with the lower part of the hot spring through the conduit t! comprising the valve I2. the direction of the valve 10 is such that the liquid can flow from the reservoir 4 to the chamber 5, the valve I2 allows the circulation of the liquid from the chamber 5 to the hot source I.

 the three-way valve 6 is automatically controlled by two level sensors I3 and I4, high and low levels of the vapor liquid interface in the chamber 5.

 A conduit 15 connects the lower part of the reservoir 3 to the upper part of the cold source 2 through a valve I7 which passes in the direction of the cold source reservoir 3.

The lower part of the cold source is connected by a conduit I6 to the upper part of the reservoir 4, this conduit I6 is terminated by a sprinkling device I8 which makes it possible to ensure satisfactory thermal contact between the vapor contained in the upper part from reservoir 4 and the liquid from the cold source. the operation of the pump according to FIG. I is as follows: the vapor pressure in the reservoir 3 communicating with the hot source is higher than in the reservoir 4 which receives liquid coming from the cold source via the conduit I6, the liquid therefore circulates under the effect of this difference between the vapor pressures of the reservoirs 3 and 4, by the conduits I5 and I6 through the valve I7. During this displacement, the liquid transfers heat from the hot source at the cold source, and the liquid acquires potential and kinetic energy. In the case where the hot source is a solar collector and the cold source is a tank for the preparation of domestic hot water, the valve I7 makes it possible to avoid cooling of the tank by the effect of thermosiphon or heat pipe, at night when the collector solar is cooler than the hot water stored, in other applications this I7 valve is not essential.

 the transfer of the liquid from the reservoir 4 to the reservoir 3 takes place thanks to the potential and kinetic energy accumulated during the first part of the journey which has just been described.

 When the three-way valve 6 is in its first position, the vapor phase contained in the chamber 5 communicates with the reservoir 4, and liquid flows from the reservoir 4 into the chamber 5 through the conduit 9 through the valve I0, and the level of the liquid rises in the chamber 5. When the liquid vapor interface in the chamber 5 reaches an upper threshold, the three-way valve 6 switches to the second position and connects the upper part of the chamber 5 with the upper part of the reservoir 3 via the conduit 7, the communication with the conduit 8 being cut off. the vapor pressures of the tanks 3 and 5 are equalized, the pressure increases in the chamber 5 which induces the closing of the valve I0, the two tanks 3 and 5 then form communicating vessels via the conduit 6t, of the valve 12, and from the hot source, the liquid flows from the chamber 5 to the reservoir 3 via the conduit i of the valve 12 and the hot source. the level of the liquid drops in the chamber 5, until the vapor liquid interface reaches a lower threshold which causes the three-way valve 6 to tilt in the first position, the chamber 5 is then put into communication with the reservoir 4 through the conduit 8, the pressure decreases in the chamber 5 which causes the closure of the valve I2 and the opening of the valve I0, and a new cycle begins. During these cycles the liquid flows from reservoir 4 to reservoir 3, without there being any equalization between the vapor pressures of the reservoirs 3 and 4, thus the difference between the vapor pressures of the two reservoirs 3 and 4 is maintained, the flow of liquid through the conduits I5 and I6 through the cold source is thus permanent.

 In Figure I, tanks 3 and 4 have an elongated shape in the height direction, so when the flow increases in the circuit passing through the cold source, the difference between the levels of liquids in tanks 3 and 4 increases , which also increases the flow of the return circuit passing through the intermediate chamber 5. If the reservoir 4 were to fill completely with liquid, the kinetic energy acquired would cause the valve 10 and the valve 12 to open, which would allow a return of the liquid to the reservoir faster.

 FIG. 2 schematically represents a nonlimiting example of embodiment of a pump corresponding to the device which has just been described in relation to FIG. I. It also includes devices auxiliary to the pump.

 In this FIG. 2, the elements homologous to those of FIG. I are designated by the same reference mark followed by the index a. the relative dimensions of the various elements were not respected in order to represent certain details.

 The hot source is represented by a solar collector la, the cold source is a domestic hot water preparation tank 2a comprising a heat exchanger I9; the rest of the tallatior. is not specific to this application and can be used in most remote heat transfer systems.

 the spraying device comprises a valve 28, this valve opens to the passage of the liquid and increases the speed of ejection of the liquid, the liquid thus being able to reach the entire volume of the reservoir 4a, even for low liquid flow rates. This movable valve can be produced in other forms equivalent to that presented in FIG. 2.

 The automatic valve consists of two valves 20 and 21 integral with a rod 24, the rise of the rod 24 applies the valve 21 to its seat 23, while the descent of the rod 24 opens the valve 21 and closes the valve 20 by applying it to its seat 22.

 The control rod 24 has two stops 25 and 26, the valve 6a is controlled by an annular float 27 sliding freely around the rod 24 between the two stops 25 and 26.

 The operation is as follows: the hot source heats the liquid contained in the tank 3a, the vapor pressure increases in this tank, one of the valve I2a or IOa is therefore closed, the liquid flows through the valve I7a, from the exchanger I9 and from the conduit I6a in the tank 4a by the spraying device I8a, the level of the liquid rises in the tank 4a, which allows a return of the liquid to the tank 3a by the intermediate chamber 5a.

 the operation of the three-way valve is initially as follows, the rod 24 is in the lower position, the valve 21 is open and the valve 20 is closed, the chamber 5a communicates with the reservoir 4a, the upper communication with the reservoir 3a being closed by the valve 20. The pressure in the tank 3a being higher than in the tanks 4a and 5a, the valves 12a and 20 are kept closed, the state of the valve 6a in the lower position is therefore stable. the level of the liquid in the reservoir 4a being higher than in the chamber 5a, the liquid flows by gravity into the intermediate chamber 5a, the vapor contained in the chamber 5a flows through the conduit 8a towards the reservoir 4a, from the liquid enters the chamber 5a through the valve IOa. The vapor leaving the tank 5a and the liquid entering this same tank exchange heat in the enclosure delimited by the grid 33 in the tank 4a. The level of the liquid rises in the chamber 5a and the float 27 comes press against the upper stop 26; the liquid level continues to rise until Archimedes' push on the float causes the rod 24 carrying the valves 20 and 21 to rise. The valve 20 opens, and almost simultaneously the valve 21 closed. After closing the valve 21, the increase in the vapor pressure in the reservoir 5a keeps the valve 21 pressed against its seat, the state of the valve in the upper position is therefore stable, even when the float does not press not against the stopper 26. The communication by the valve 6a of the chamber 5a with the reservoir 3a causes the liquid to flow through the valve I2a to the reservoir 3a through the hot source; while the level of the liquid drops in the intermediate chamber 5a, the float 27 slides on the rod 24 and finally comes to bear on the stop 25, and when the level of the liquid continues to drop, the apparent weight of the float increases and eventually driving down the rod 24, which causes the valve 2I to open and the valve 20 to close, we find ourselves in the initial conditions and a new cycle begins again.

 It goes without saying that the various elements which go into the composition of the pump which has just been presented can be produced in different forms without departing from the scope of the invention, it is in particular possible to use the known techniques of three-way valves. distribution channels and systems, for example pilot valve valves may be used; the stable states of valve 6a can be obtained by springs.

 In order to reduce the size, it is advantageous to superimpose the tanks 4a, 5a and 3a. One of the tanks 3a or 4a can have a very small volume, the tank 3a can be included in the hot spring.

 The nature of the fluids contained in the installation depends on the temperatures at which the desired heat exchanges take place. Water can advantageously constitute the heat transfer fluid, a more volatile fluid can be mixed therein to increase the vapor pressure.

 It is possible, without departing from the scope of the invention, to place several intermediate chambers, in series or in parallel between the upper tank and the hot source, for example it is advantageous to ensure the continuity of the flow in the hot source to place two chambers intermediaries in parallel so that they operate in phase opposition.

 FIG. 3 schematically represents an installation comprising two different hot sources operating as a base, two cold sources and systems for circulating the heat-transfer liquid such as those which have been described in connection with FIGS. I or 2.

 the two hot springs can supply calories at different times and at different rates.

These sources can be, for example, two groups of insolators of different surfaces or orientations, or a group of insulators associated with a fuel boiler.

 There is also described a device making it possible to avoid the entry of air when the temperature of the vapor phase of the fluid of the installation becomes lower than the boiling temperature under atmospheric pressure.

 In this FIG. 3, the homologous elements associated with each of the two hot sources are represented by the same reference mark followed by the index d or g depending on whether it is the first or the second hot source. the common elements are represented by a reference followed by the letter b, when they have already been presented in the previous figures.

 Two cold sources 2b and 2c have been shown in parallel, their number may naturally be higher, this is the case in a central heating installation in which the radiators act as a cold source.

 Each of the hot springs Ig or Id is associated with a 3g or 3d tank located at a higher level than the hot source, each of the 3g or 3d tanks is connected by a valve 30g or 30d to a conduit 31 leading to the cold sources. The cold sources outlet is connected by a conduit I6b to the single upper tank 4b.

 Each of the hot springs Ig or Id is associated with an intermediate chamber 5g pu 5d provided with an automatic valve 6g or 6d and ducts 8g, 9g, 7g IIg or 8d, 9d, 7d, IId equipped with non-return valves IOg, I2g or IOd, I2d.

 If one of the hot springs, for example Ig is at low temperature, the pressure in this source being lower than in the rest of the installation, the valve 30g remains closed, the tank 3g fills with liquid which descends through gravity through the intermediate chamber 5g, when the reservoir 3g is full of liquid the source Ig is isolated from the upper reservoir 4b by the valve 6g and by the valves IQ; or {lg. Thus the source Ig and the reservoir 3g are completely isolated from the rest of the circuit as long as the pressure in the reservoir 3g does not reach the pressure of the conduit 3t.

 In this installation as in the previous ones, the circuit comprises one or more fluids in vapor liquid equilibrium, the vapor phase having to be perfectly condensable; in the event of a micro leak, air can enter the installation when the temperature of the fluid is lower than the boiling temperature under atmospheric pressure, to circulate the liquid must compress this air, which disrupts the operation .

 The device made up of the membrane vessel 34 makes it possible to maintain a sufficient pressure to oppose any entry of air into the installation.

 This device comprises a membrane vase inflated to a pressure higher than atmospheric pressure, the bladder 33 is connected to the upper reservoir 4b by a conduit 32 opening at an intermediate level between the bottom and the top of the reservoir 4b.

 the operation is as follows: when the hot springs are at low temperature, the 3d and 3g tanks are full of liquid and the vapor pressure of the installation fluid is lower than the gas pressure of the membrane vessel, the bladder empties of liquid and the upper reservoir 4b is full of liquid; outside air cannot enter the installation where the pressure is maintained above atmospheric pressure. when the temperature of a hot source becomes higher than the boiling temperature of the fluid under the filling pressure of the membrane vase, steam is formed in one of the reservoirs 3g or 3d, the bladder 33 swells with liquid , and when the temperature of the fluid contained in the reservoir 4b becomes higher than the boiling temperature of the fluid under the filling pressure of the membrane vase, steam is formed at the top of the reservoir 4b, and the bladder of the vase membrane continues to fill with liquid until the liquid vapor interface in the reservoir 4b reaches the level of the mouth of the conduit 32. the level of the liquid in the reservoir 4b is thus maintained at a lower threshold such that the operation of the return circuit of the liquid from the upper reservoir to the hot sources through the intermediate chambers is not disturbed.

Claims (9)

 b.) when the level of the vapor liquid interface in the intermediate chamber reaches an upper threshold, the communication between the said chamber and the upper reservoir is interrupted and the said chamber is placed in communication with the assembly constituted by the cnaude source and the lower tank, so that the liquid contained in the intermediate chamber flows by gravity towards the hot source and the lower tank, then when the level of the liquid vapor interface reaches a lower threshold the communication between the intermediate chamber and the hot source and the intermediate chamber is put back into communication with the upper reservoir as in a, and during these cycles, liquid is transferred from the upper reservoir to the lower reservoir, steam is transferred in the opposite direction, without equalizing the vapor pressures of the upper tank and the lower tank, so that the flow of liquid from the lower tank eur to the upper tank through the cold source is not interrupted, the heat transfer liquid thus circulates continuously transporting calories from the hot source to the cold source.  a.) communicating with the upper reservoir a chamber having an intermediate level between the upper reservoir and the lower reservoir, so that the liquid contained in the upper reservoir can flow into the intermediate chamber which is filled with liquid,  the return of the liquid from the upper reservoir to the assembly consisting of the hot source and the lower reservoir is obtained by the following operations a and b  - the liquid circulates from the first tank to the second by crossing the cold source under the effect of the difference in vapor pressures between the fluid of the first tank communicating with the hot source and the fluid of the second tank which receives liquid from the exchanger of the cold source, this flow tends to cause the level of the liquid-vapor interface to rise in the upper tank and an equivalent descent of the level of the liquid-vapor interface in the lower tank,  - conduits provided with automatic shut-off devices making it possible to connect the said (or said) chamber (s) intermediate (s) alternately, either with the upper reservoir, or with the assembly constituted by the lower reservoir and the hot spring, characterized in that  - at least one chamber (5) located at an intermediate level between the upper tank (4) and the lower tank (3),  - A conduit (15) connecting the exchanger of the cold source to the assembly constituted by the first tank and the hot source in the part of said assembly containing the liquid phase, the other end of the exchanger of the source cold being connected by another conduit (I6) to the upper reservoir (4),  - a second closed tank (4) which is situated at a level at least equal to that of the first tank, which tanks contain a mixture of the liquid and vapor phases of a fluid,  - a cold source (2)  a hot source (I) communicating with a first closed tank (3) situated at a level greater than or equal to that of the hot source, the said tank being able to be included in the heat exchanger of the hot source,  I.- Method for circulating a heat transfer liquid in a closed circuit which comprises  2.- Device for circulating a heat transfer fluid in a closed circuit, comprising at least one hot source (I) and at least one cold source (2), characterized in that the said device comprises  a first closed tank (3) communicating with the hot source and located at a level greater than or equal to that of the hot source, the said tank can be confused with the upper part of the heat source exchanger,  - a second closed tank (4) which is situated at a level at least equal to that of the first tank, which tanks contain a mixture of the liquid and vapor phases of a fluid  - a conduit (I5) connecting the heat exchanger of the cold source to the assembly constituted by the first tank and the hot source in the part of said assembly containing the liquid phase, the other end of the exchanger of the cold source being connected by another conduit (I6) to the upper tank (4),  - at least one chambsk5) located at an intermediate level between the upper tank (4) and the lower tank (3),  - conduits fitted with closure devices making it possible to communicate alternately and automatically that said (or said) chamber (s) -intermediate (s) (5) either with the upper tank, or with the 'assembly constituted by the lower tank and the heat exchanger of the hot source.  3.- Device according to claim 2 wherein the chamber (5) located at an intermediate level between the upper tank and the lower tank comprises two level sensors (I3, I4) controlling an automatic valve (6), which valve allows put the upper part of said chamber in communication either with the upper reservoir (4) when the liquid vapor interface reaches the level of the lower sensor (I4) or with the upper part of the lower reservoir when the liquid vapor interface reaches level of the upper sensor I3, and in which the said chamber comprises at the lower part two conduits (9, II) provided with non-return valves (IO, I2) communicating with the bottom of the lower tank on the one hand and with the hot source on the other hand, the direction of said valves being such that the liquid can flow from the upper reservoir to the hot source.  4.- Device according to claim 2 characterized in that the automatic valve (6) is a float valve consisting of two valves (20) and (21) integral with a rod (24) having two stops (25, 26) , the rise of the rod (24) applying the valve (21) on its seat (23), and opening the valve (20) the descent of the rod (24) opening the valve (21) communicating with the upper tank and closing the valve (20) communicating with the lower reservoir, the said float having an annular shape allowing it to slide on the rod (24) between the stops (25, 26).  5.- Device according to any one of claims 2 to 4, characterized in that the pipe (I6) which connects the cold source to the upper tank (4) opens into the upper part of this tank (4) containing the phase gas and carries at its end a spray device (18), for example a flapper valve (28).  6.- Device according to any one of claims 2 to 5 characterized in that the conduit (I5) connecting the assembly consisting of the lower reservoir and the hot source to one exchanger of the cold source comprises a valve no return (I7) allows the liquid to flow in the direction hot source cold source.  7.- Device according to any one of claims 2 to 6, characterized in that the fluid circuit comprises an expansion tank (34) of the membrane type, inflated to a pressure higher than atmospheric pressure.  8.- Device according to claim 7 characterized in that the bladder of the expansion vessel (34) is connected to the upper reservoir (4) by a conduit (32) opening at an intermediate level between the bottom and the top of the upper tank (4).  9.- Device according to one of claims 2 to 8 characterized in that it comprises two hot springs (Ig, Id), two intermediate chambers (5d, 5g), two lower tanks (3g, 3d) which are connected in parallel through Og valves, 30d) on the same tube (31) connected to one exchanger of the cold source.  IO.- Application of a device according to one of claims 2 to 9 to the circulation of a heat transfer liquid in an installation comprising a solar collector as a hot source and a heat exchanger as a cold source.