EP1230520B1

EP1230520B1 - Draw-off conduit for hot-water

Info

Publication number: EP1230520B1
Application number: EP00980112A
Authority: EP
Inventors: Evert Sjoerdsma
Original assignee: Energieonderzoek Centrum Nederland ECN
Current assignee: Energieonderzoek Centrum Nederland ECN
Priority date: 1999-11-18
Filing date: 2000-11-08
Publication date: 2004-08-11
Anticipated expiration: 2020-11-08
Also published as: NL1013603C2; DE60012963D1; WO2001036878A1; DE60012963T2; AU1741201A; ATE273486T1; EP1230520A1

Abstract

Draw-off conduit for transporting water from a hot-water heater to a draw-off point, which is connected in the vicinity of the draw-off point to a thermally insulated storage vessel and comprises control means for storing water from this draw-off conduit in that storage vessel and filling this draw-off conduit with cold water immediately following drawing of water from the draw-off point, and extracting water from that storage vessel at the start of a repeated drawing of water from that draw-off point.

Description

The invention relates to a hot-water supply arrangement, comprising a hot-water heater, a draw-off conduit for transporting water from said hot-water heater to a draw-off point, and a thermally insulated storage vessel for storing hot-water transported from said hot-water heater, the storage vessel being connected to said draw-off conduit in the vicinity of the draw-off point.

US-A-5072717 discloses an arrangement, in which a storage vessel installed just ahead of a draw-off point stores a small amount of water and maintains it to the temperature of a hot-water heater. When the draw-off is opened, the water from the storage vessel is first drawn while the cooled down water which was stationary in the conduit coming from the hot-water heater refills the storage vessel. When the conduit is cleared of cold water the storage vessel is bypassed, and its stored cold water is slowly admixed in the flow of hot water to the draw-off point.

Patent Abstracts of Japan, vol. 007, no. 240 (M-251) discloses an arrangement, in which the storage vessel is included in a bypass course of a water supplying line in maximum possible vicintity to a draw-off point, for storing hot water and merging water stored therein with water from the supply line.

Although according to these prior art arrangements hot water is immediately available on drawing of water from the draw-off point, these arrangements have a disadvantage in that it is the cause of loss of energy and water, which loss results from cooling of hot water which, after water has been drawn off a first time at a draw-off point, remains in the draw-off conduit, which means a loss of energy and eventually a loss of water. On an annual basis such so-called draw-off losses can assume substantial proportions, depending on the length of a draw-off conduit and the frequency of tapping. The potential costs of draw-off losses in homes are moreover further distorted by the measure of attempting to keep draw-off conduits short by placing a second hot-water heater (for instance a kitchen geyser or electric boiler) in the immediate vicinity of a draw-off point. The placing of a second hot-water heater does of course contribute to the comfort of the user, who has to wait only a short time until hot water is available, but results in operating and investment costs which are relatively high compared with the costs of a first heating apparatus, for instance a combined apparatus placed in an attic for hot water supply and home heating.

It is an object of the invention to provide a hot-water supply arrangement wherein loss of water and energy resulting from cooling of hot water in the conduit does not occur, or at least hardly so.

This objective is achieved, and other advantages obtained, with a hot-water supply arrangement of the type specified in the preamble, in which according to the invention the storage vessel is arranged for containing a compressible air volume and control means are provided allowing the storage vessel to draw-in hot water still present in the draw-off conduit after drawing of water from the draw-off point and allowing hot water to flow from that storage vessel to the draw-off point (5) at the start of a repeated drawing of water, and for keeping a compressible gas volume in the vessel.

When the draw-off point is opened in a hot-water supply arrangement according to the invention, hot water under pressure of the compressible gas volume is extracted from the storage vessel, which water then mixes with cold water from the draw-off conduit and thus mixed hot water flows out of the draw-off point. With a correct dimensioning of the storage vessel the quantity of hot water therein is sufficient to be mixed with the total quantity of cold or cooled water in the draw-off conduit, and heated water from the hot-water heater also reaches the draw-off point before the storage vessel is completely empty. When the draw-off point is closed the storage vessel is filled with hot water from the draw-off conduit, and the draw-off conduit is filled with cold water from a cold water conduit, such that in principle no hot water from the hot-water heater remains in the draw-off conduit.

In an embodiment of a hot-water supply arrangement according to the invention the storage vessel is provided on its underside with an outlet opening closable by means of a drilled-through non-return valve, in which drilled-through non-return valve an inlet opening is provided.

In this embodiment the inlet opening preferably has a smaller diameter than the outlet opening.

The storage vessel is more preferably provided with a pressure-independent flow limiter employed as outflow limiter.

In yet another embodiment the draw-off conduit is according to the invention connected to the storage vessel via a thermally insulating conduit piece.

In an advantageous embodiment the storage vessel is a stainless steel vacuum bottle.

It has been found that the draw-off losses in a hot-water supply arrangement according to the invention are particularly minimized if the volume of the storage vessel is about twice the volume of the draw-off conduit.

In order to ensure that hot water is immediately available at the draw-off point of a hot-water supply arrangement according to the invention, irrespective of the time of the previous draw-off, the storage vessel is preferably provided with a heating element.

In an embodiment of a hot-water supply arrangement according to the invention wherein the hot-water heater is a geyser, the control means are chosen such that the storage of water from the draw-off conduit in the storage vessel takes place at a flow rate which is so low that the burner of the geyser connected to that draw-off conduit is not activated, and the geyser thus supplies cold water to the draw-off conduit.

In an embodiment of a hot-water supply arrangement according to the invention wherein the hot-water heater comprises a supply tank, for instance in an electric boiler or a gas boiler, below a determined water pressure in the draw-off conduit this draw-off conduit is connected to the supply tank by means of a switching device placed in the vicinity of the supply tank, and above this determined water pressure the draw-off conduit is connected to a cold water conduit.

In a preferred embodiment the switching device comprises a cylinder with an axial inlet opening to the cold water conduit, a lateral inlet opening to a conduit to the supply tank, a lateral outlet opening to the draw-off conduit and a slide displaceable in this cylinder, wherein the lateral outlet opening is placed closer to the axial inlet opening than the lateral inlet opening and, subject to the pressure in the draw-off conduit, the slide takes up a rest position between the lateral outlet opening and the lateral inlet opening, wherein the draw-off conduit is connected to the cold water conduit, or takes up an operating position between the lateral outlet opening and the axial inlet opening, wherein the draw-off conduit is connected to the supply tank.

The invention will be elucidated hereinbelow on the basis of embodiments and with reference to the drawings.

In the drawings

Fig. 1 shows a schematic view of a first embodiment of a draw-off conduit according to the invention,

Fig. 2 shows a view in longitudinal section of a storage vessel for the draw-off conduit shown in fig. 1,

Fig. 3 is a schematic view of a second embodiment of a draw-off conduit according to the invention,

Fig. 4 shows a view in longitudinal section of a switching device for the draw-off conduit shown in fig. 3.

Corresponding components are designated in the drawings with the same reference numerals.

Fig. 1 shows a geyser 1 (for instance in the attic of a house above a bathroom), which is connected via a short draw-off conduit 2 to a first draw-off tap 3 (for instance in that bathroom), and which via a long draw-off conduit 4 is connected to a second tap 5 (for instance in the kitchen of the house). A reversed vacuum bottle 6 connected to draw-off conduit 4 by means of a conduit piece 41 is placed in the vicinity of the second draw-off tap 5, with outer bottle 7, vacuum chamber 8 and inner bottle 9, the opening 10 of which is closed by a drilled-through non-return valve 11. Vacuum bottle 6 provides a saving of draw-off losses in draw-off conduit 4 in the following manner. During normal operation of the system the vacuum bottle 6 is filled for about 70% with hot water (level II). Situated above the water level is a compressed volume of air which is maintained by the continuous degassing of freshly supplied water. When draw-off tap 5 is opened the pressure in draw-off conduit 4 falls to about 10% of its original value, as a result of which hot water is pressed by the compressed air out of vacuum bottle 6 into draw-off conduit 4, where it mixes with the cold water present in this conduit 4. Mixed hot water thus flows from draw-off tap 5 immediately after opening. The volume of vacuum bottle 6 is chosen such that the quantity of hot water stored therein is just sufficient for mixing with the quantity of cold water in draw-off conduit 4. Before vacuum bottle 6 is completely empty, the pressure of the air bubble is equal to the pressure in draw-off conduit 4, and the outflow of hot water from vacuum bottle 6 ceases, about 10% of this bottle remaining filled with hot water (level I). In this situation hot water from geyser 1 heated by a burner 12 has become available at draw-off tap 5. When draw-off tap 5 is closed the pressure in draw-off conduit 4 rises and non-return valve 11 of vacuum bottle 6 is closed. Hot water flows from draw-off conduit 4 into vacuum bottle 6 through the bore in non-return valve 11 at a low flow rate such that burner 12 of geyser 1 is switched off, and draw-off conduit 4 slowly fills with cold water from a cold water conduit 23 supplied via geyser 1. The water flowing into vacuum bottle 6 rises again to an equilibrium level II, wherein the air bubble is compressed to a pressure equal to the pressure in draw-off conduit 4. Upon subsequent opening of draw-off tap 5, the above described cycle is repeated. A draw-off conduit 4 provided with a vacuum bottle 6 provides the advantage that hot water flows therefrom immediately the tap 5 is opened, which results in a saving of both water and energy relative to draw-off conduits without vacuum bottle.

Figure 2 shows in more detail the stainless steel vacuum bottle 6 of fig. 1 with the downward directed opening. Vacuum bottle 6 can withstand a pressure of 8 bar, the highest occurring pressure in draw-off conduit 4. The opening is closed by means of a plug 14 which is sealed with an O-ring 13 and in which is formed an outlet opening 15 which is closed by a non-return valve 11, in which an inlet opening 16 is drilled, wherein the diameter of inlet opening 16 is smaller than that of outlet opening 15. Arranged in inlet opening 16 is a cleaning pin 17 which is freely movable over determined distances. In order to prevent heat leakage, vacuum bottle 6 is connected using a coupling nut 20 to the conduit piece 41 to draw-off conduit 4 via a conduit piece 19 of a thermally insulating plastic material sealed with O-ring 18. In coupling nut 20 is arranged a pressure-independent flow limiter 21 which provides a constant outflow speed, irrespective of the pressure in vacuum bottle 6. The figure further shows a low-voltage heating element 22 arranged in plug 14, using which element a quantity of water in vacuum bottle 6 can be kept at the correct temperature, also in the case of prolonged storage of this quantity. In order to hold a quantity of water of 1.5 litres in a vacuum bottle 6 at a temperature of about 80°C with such an element 22, which is for instance powered by a 6-Volt plug-in transformer with separated windings, a continually supplied power of about 3 Watt will suffice, which, including the own use of the plug-in transformer, results in an annual consumption of about 40 kWh. This consumption is negligible compared to the annual energy saving which can be realized with the vacuum bottle.

Fig. 3 shows a boiler 23 with heating element 24 (for instance in the attic of a house above a bathroom), which is connected via a short draw-off conduit 2 to a first draw-off tap 3 (for instance in that bathroom), and which is connected via a long draw-off tap 26 to a second draw-off tap 5 (for instance in the kitchen of the house). Similarly to the situation shown in fig. 1, a reversed vacuum bottle 6 connected onto draw-off conduit 4 is placed in the vicinity of second draw-off tap 5. Other than draw-off conduit 4 of a geyser 1 (fig. 1), the draw-off conduit 26 for a boiler 24 heated electrically or with gas is connected to a switching valve 27 which connects draw-off conduit 26, subject to the pressure therein, to a conduit 28 to boiler 24 or cold water conduit 23. The operation of vacuum bottle 6 is set forth above in the elucidation of fig. 1, and will only be repeated insofar as necessary for a good understanding. When draw-off tap 5 is opened the pressure in draw-off conduit 4 falls, as a result of which hot water is pressed by the compressed air out of vacuum bottle 6 into draw-off conduit 26, where it mixes with the cold water present in this conduit 26, and as a result of which the draw-off conduit 26 is connected to boiler 24 by switching valve 27. When draw-off tap 5 is closed the pressure in draw-off conduit 26 rises and the non-return valve 11 of vacuum bottle 6 is closed. Hot water flows out of draw-off conduit 4 into vacuum bottle 6 through the perforation in non-return valve 11 at a flow rate such that pressure in draw-off conduit 26 remains higher than when the draw-off tap 5 is open, as a result of which a switching occurs in switching valve 27, and draw-off conduit 26 is connected onto cold water conduit 23, so that draw-off conduit 26 slowly fills with cold water from this cold water conduit 23. The hot water flowing into vacuum bottle 6 rises again to an equilibrium level II, wherein the air bubble is compressed to a pressure which is equal to the pressure in draw-off conduit 26. Upon subsequent opening of draw-off tap 5 the above described cycle is repeated.

Fig. 4 shows the switching valve of fig. 3 in more detail in a rest position, wherein the draw-off tap 5 is closed and the water in

conduits

28, 26 and 23 has come to a standstill. Switching valve 27 comprises a cylindrical housing 29 with an axial inlet opening 30 to cold water conduit 23, a lateral inlet opening 31 to boiler conduit 28, a lateral outlet opening 32 to draw-off conduit 26 and a slide 34 displaceable in this cylinder 27, wherein the lateral outlet opening 32 is placed closer to the axial inlet opening 30 than the lateral inlet opening 31 and, depending on the pressure in draw-off conduit 26, the slide 34 takes up a rest position between the lateral outlet opening 32 and the lateral inlet opening 31, wherein draw-off conduit 26 is connected to cold water conduit 23, or takes up an operating position between the lateral outlet opening 26 and the axial inlet opening 30, wherein draw-off conduit 26 is connected to boiler conduit 28, and thus to boiler 24. The switching takes place by means of a piston 35 which is connected to slide 34 and enclosed under pre-pressure of a spiral spring 33. If a pressure difference occurs over piston 35, it moves to the right counter to the pressure of spring 33, as a result of which the slide 34 closes the cold water conduit 23 and leaves clear the connection between boiler conduit 28 and tap water conduit 26. The pressure difference occurs as a result of a small constriction 36 in outlet opening 32. The full pressure of cold water conduit 23 is always on the left-hand side of piston 35, this pressure being admitted via a first internal channel 37, and the (variable) pressure of tap water conduit 26, which is admitted via a second internal channel 38, is always on the right-hand side of piston 35. When there is a small flow through switching valve 27 the occurring pressure differences are too low to cause piston 35 to move to the right counter to the pressure of spring 33. A small pressure difference occurs if draw-off tap 5 is closed again after hot water is drawn off, and vacuum bottle 6 slowly fills up. In this situation cold water flows out of cold water conduit 23 into draw-off conduit 26 via switching valve 27.

It is noted that the embodiments described here serve to elucidate the invention, not to limit it.

Falling for instance within the scope of the claims appended herein are embodiments wherein the discussed switching valve is not realized by means of a cylinder with piston-slide combination, but by a membrane with a shuttle valve, for instance in an existing casting of a reducer valve.

Claims

Hot-water supply arrangement, comprising a draw-off conduit (4, 26) for transporting water from a hot-water heater (1, 24) to a draw-off point (5), and a thermally insulated storage vessel (6) for storing hot-water transported from said hot-water heater (1, 24), the storage vessel (6) being connected to said draw-off conduit (4, 26) in the vicinity of the draw-off point (5), characterized in that the storage vessel (6) is arranged for containing a compressible air volume and control means (11, 27) are provided allowing the storage vessel (6) to draw-in hot water still present in the draw-off conduit (4, 26) after drawing of water from the draw-off point (5) and allowing hot water to flow from that storage vessel (6) to the draw-off point (5) at the start of a repeated drawing of water, and for keeping a compressible gas volume in the vessel.
Hot-water supply arrangement as claimed in claim 1, characterized in that the control means (11) comprise a drilled-through non-return valve (11) having an inlet opening (16), which drilled-through non-return valve (11) is provided at an outlet opening (15) of the storage vessel (6) on its underside.
Hot-water supply arrangement as claimed in claim 2, characterized in that the inlet opening (16) has a smaller diameter than the outlet opening (15).
Hot-water supply arrangement as claimed in any of the foregoing claims, characterized in that the storage vessel (6) is connnected to draw-off conduit (4, 26) via a thermally insulating conduit piece (19).
Hot-water supply arrangement as claimed in any of the foregoing claims, characterized in that the storage vessel (6) is provided with a pressure-independent flow limiter (21) employed as outflow limiter.
Hot-water supply arrangement as claimed in any of the foregoing claims, characterized in that the storage vessel is a stainless steel vacuum bottle (6).
Hot-water supply arrangement as claimed in any of the foregoing claims, characterized in that the volume of the storage vessel (6) amounts to about twice the volume of the draw-off conduit (4, 26).
Hot-water supply arrangement as claimed in any of the foregoing claims, characterized in that the storage vessel (6) is provided with a heating element (22).
Hot-water supply arrangement as claimed in any of the foregoing claims, wherein the hot-water heater comprises a supply tank (24), characterized in that the control means comprise a switching device (27) placed in draw-off conduit (26) in the vicinity of the supply tank (24) for connecting the draw-off conduit (26) to the supply tank (24) below a determined water pressure in the draw-off conduit (26), and connecting said draw-off conduit (26) to a cold water conduit (23) above this determined water pressure is connected.
Hot-water supply arrangement as claimed in claim 9, characterized in that the switching device (27) comprises a cylinder (29) with an axial inlet opening (30) to the cold water conduit (23), a lateral inlet opening (31) to a conduit (28) to the supply tank (24), a lateral outlet opening (32) to the draw-off conduit (26) and a slide (34) displaceable in this cylinder (29), wherein the lateral outlet opening (32) is placed closer to the axial inlet opening (30) than the lateral inlet opening (31) and, subject to the pressure in the draw-off conduit (26), the slide (34) takes up a rest position between the lateral outlet opening (32) and the lateral inlet opening (31), wherein the draw-off conduit (26) is connected to the cold water conduit (23), or takes up an operating position between the lateral outlet opening (32) and the axial inlet opening (30), wherein the draw-off conduit (26) is connected to the supply tank (24).