EP4616124A1 - Domestic hot water storage tank with immersed heating element - Google Patents

Abstract

The invention relates to a domestic hot water storage tank (1) comprising an inlet connection (2) for adding water to the tank (1), an outlet connection (3) for discharging hot water contained in the tank (1) and a heating element intended to be immersed in the water in the tank (1) in order to heat the water present in the bottom portion of the tank (1) when in the installed position. According to the invention, the heating element comprises at least one electrically insulated resistive flexible wire, the ends (10a, 10b) of which come out of the tank (1) to connect to an external electrical power supply and at least one length portion located between the ends (10a, 10b) of which is intended to rest, under the effect of gravity, at the bottom of the tank (1) when in the installed position, whereby forming a random heap (12).

Description

Description

Title of the invention: Domestic hot water storage tank with submerged heating element

Technical area

[0001] The present invention relates to the general field of domestic hot water storage tanks, and more specifically a domestic hot water storage tank comprising an inlet tap for bringing water into the tank, a outlet tap to bring out hot water contained in the tank and a heating element intended to be immersed in the water of the tank in order to heat the water present in the lower part of the tank in the installed position.

Technology background

[0002] Such tanks are used for example in electric water heaters.

[0003] Figure 1 schematically illustrates a known tank 1 for an electric water heater, particularly suitable for a so-called “sink” installation. The tank 1, generally made of steel with an enameled internal wall, has an inlet tap 2 to bring cold water under pressure into the tank 1, and an outlet tap 3 to let out the heated water contained therein. in the tank 1. In such a configuration, the cold water enters the interior of the tank 1 through an inlet rod 4 carried by the inlet tap 2 and extending in the axis of this inlet tap 2. The water contained in the tank 1 is heated by an electric heating element 5. The heating temperature is regulated via one or more thermostats housed in a thermowell 6 extending through an opening made in the tank 1, to heat the water according to a set temperature (for example between 60 and 65° C to make it possible to obtain an actual outlet temperature of approximately 40° C if the outlet water is mixed via a mixer with cold water). At the request of a user at a drawing point (washbasin or sink faucet, shower, bathtub, etc.), the heated water can leave tank 1 through an outlet pipe. 7 carried by the outlet tap 3 and extending axially to the outlet tap 3. [0004] An electric water heater operates most of the time with storage, that is to say it does not heat the water continuously, but accumulates a quantity of hot water for daily needs and operates according to the principle of stratification. More precisely, cold water under pressure enters the interior of the tank as it empties to meet domestic hot water needs. The cold water entering is heated by the heating element or any alternative energy supply and gradually rises to the top of the tank. Indeed, like air, hot water has a lower density than cold water. It is therefore lighter and naturally gains height. On the other hand, cold water, naturally denser, remains at the bottom of the tank. It is this physical principle which is the origin of the name stratification.

[0005] In the case of the "over sink" configuration of Figure 1, the entry rod 4 extends only in the lower internal part of the tank 1, and has a stamped upper part to avoid any vertical entry d cold water, and an intermediate portion provided with side orifices guaranteeing substantially horizontal penetration of cold water into the tank. Such an intermediate portion is commonly called a “jet breaker” because it will “break” the pressure of the water injected into the bottom of the tank and thus preserve the natural distribution of the layers of water according to their temperature. Conversely, the outlet pipe 4 is much longer in order to take the heated water from the upper internal part of the tank 1.

[0006] For a so-called “under-sink” configuration, illustrated schematically in Figure 2, we find the same components as those detailed above. However, taking into account the position of the inlet 2 and outlet 3 connections in the upper part of the tank 1, and to respect the phenomenon of stratification of the water, the inlet rod 4 is here much longer by so that its intermediate part carrying the side orifices and its stamped end are placed in the lower part of the tank 1. The outlet rod, on the other hand, is very short so as to take the hot water located in the upper part of the tank 1.

[0007] In the two configurations above, it is known to further equip the tank 1 with an anode 8 for protecting the tank 1 against corrosion which extends longitudinally inside the tank 1. The protective anode forms cathodic protection which can be sacrificial, for example made of alloy magnesium or aluminum alloy. Alternatively, the protective anode may be permanent. In the latter case, an imposed electric current passes through the protective anode. Alternatively, the protective anode can be of the type combined with an impressed current anode around which a sacrificial anode is arranged.

[0008] In the embodiments illustrated in Figures 1 and 2, the electric heating element 5, the thermowell 6 containing the thermostat(s) and the protective anode 8 extend into the tank 1 through a corresponding opening passing through the external wall of the tank 1, and are carried by the same flange 9, itself removably fixed to the tank 1, on the periphery of the opening. More precisely, the protective anode 8 extends close to and parallel to the thermowell 6 and to a portion of the heating element 5, and substantially horizontally when the tank is installed.

[0009] In the two configurations above, the heating element is constituted by a shielded electrical resistance 5 immersed in the water of tank 1.

[00010] The use of a shielded electrical resistance presents a certain number of disadvantages:

[00011] First of all, this type of resistance has a high surface power density (expressed in Watts per square meter), which results in a high temperature of the resistance wall which is in contact with the water. The shielded electrical resistance is sensitive in particular to the quality of the water and its lifespan is short. Furthermore, as we seek to mainly heat the water contained at the bottom of the tank, it is necessary, as visible in Figures 1 and 2, to give the shielded electrical resistance 5 a relatively complex bent L shape, the number of which of elbows depends on the desired heating power. This bent L shape makes it complex to install the heating element carried by the flange 9 inside the tank, especially in the case of a compact tank. Indeed, the tank 1 is generally produced by assembling two bases 1a, 1b and possibly an intermediate shell 1c whose dimension varies depending on the tank capacity that one wishes to obtain. Consequently, the more compact the tank is (for example for a capacity of 5 liters), the more difficult it is to install the shielded resistance inside the tank. When the flange 9 also carries the protection anode against the corrosion, as illustrated in Figures 1 and 2, the installation of the elbow shielded resistance is impossible if this anode is too long.

[00012] To increase the lifespan of the heating element, it has already been proposed to replace the shielded electrical heating resistance with a soapstone resistance placed inside a waterproof enamelled steel sheath, the whole being immersed in water, and for example carried by the flange 9. This type of heating element is, however, very expensive and bulky, which does not allow its use in the case of a compact tank.

[00013] Other solutions consist of heating the water from outside the tank. In particular, solutions are known consisting of covering the tank with a heating blanket comprising, inside a flexible envelope, a mesh of resistive electrical wires. Given the very low surface power density of electrical wires, these solutions do not make it possible to provide significant heating powers and therefore heating speeds, required in certain markets. They are also very expensive. Other solutions consist of using the principle of induction heating via heating coils which directly heat the tank. The latter must be made of ferritic steel. In addition to the high cost, electric fields can have an uncontrolled impact on the lifespan of the enameled tank. Moreover, all solutions aimed at heating the water from outside the tank are less effective than solutions with a submerged heating element.

Summary of the invention

The present invention aims to overcome the disadvantages of known solutions.

[00015] This aim is achieved in accordance with the present invention, the subject of which is a storage domestic hot water tank comprising an inlet tap to bring water into the tank, an outlet tap to let out hot water contained in the tank and a heating element intended to be immersed in the water of the tank in order to heat the water present in the lower part of the tank in the installed position, characterized in that said heating element comprises at least one electrically insulated resistive flexible wire, the ends of which emerge from the tank for connection to an external electrical power supply, and of which at least a portion of length located between the ends is intended to rest by gravitation at the bottom of the tank in said installed position, forming a random cluster.

[00016] According to one embodiment, said heating element consists of at least one electrically insulated resistive flexible wire. By “constituted” is meant the fact that said heating element only comprises said at least one electrically insulated resistive flexible wire. In other words, said at least one electrically insulated resistive flexible wire is not arranged within a sheath or a tube. An external wall of said at least one electrically insulated resistive flexible wire is thus intended to be in contact with the water present in the tank.

[00017] In one possible embodiment, the heating element comprises a plurality of flexible resistive wires, the ends of which emerge from the tank for connection to an external electrical power supply, each wire being electrically insulated and having at least one portion of length between its ends intended to rest by gravitation at the bottom of the tank in said installed position, forming with the other wires said random cluster.

[00018] Said at least one wire preferably comprises a metallic core, and an electrical insulation sheath, surrounding said core.

[00019] In one possible embodiment, the tank further comprises an anode for protecting the tank against corrosion, said anode extending longitudinally inside the tank.

[00020] In one possible embodiment, the tank further comprises an element removably fixed to the tank to sealingly seal an opening passing through the wall of the tank, the ends of said at least one wire or of said plurality of wires coming out of the tank at the opening and said element.

[00021] The protective anode is preferably carried by said element.

[00022] In one possible embodiment and the inlet connection are located in the lower part of the tank in the installed position. Alternatively, the inlet connection and the outlet connection are located in the upper part of the tank in the installed position.

[00023] In one possible embodiment, the element is located in the lower part of the tank in the installed position. The element can then be used as a drain plug.

[00024] In another possible embodiment, the element is located in the upper part of the tank in the installed position. [00025] In one possible embodiment, the element is a flange located on a side wall of the tank in the installed position.

Brief description of the figures

[00026] The description which follows with reference to the appended drawings, given as non-limiting examples, will make it clear what the invention consists of and how it can be carried out. In the attached figures:

[00027] [fig. 1] Figure 1, already written above, schematically illustrates part of a known tank for electric water heater, particularly adapted to a so-called “over sink” configuration;

[00028] [fig. 2] Figure 2, already written above, schematically illustrates part of another known tank for water heater, particularly adapted to a so-called “under sink” configuration;

[00029] [fig. 3] Figure 3 illustrates a modification made to the water heater tank of Figure 1, in accordance with a first embodiment of the present invention;

[00030] [fig. 4] Figure 4 illustrates a modification made to the water heater tank of Figure 2, in accordance with another embodiment of the present invention;

[00031] [fig. 5] Figure 5 gives comparative tests illustrating the gains of the invention.

Description of embodiment(s)

[00032] In the figures, identical or equivalent elements will bear the same reference signs. The various diagrams are not to scale. In certain figures, certain elements, including the tank, have been deliberately represented in mixed lines in order to facilitate the understanding of the figures and to show internal parts of the tank.

[00033] Figure 3 illustrates a first embodiment of a tank according to the invention for an electric water heater, particularly suitable for a so-called “over-sink” configuration.

[00034] We thus find the elements already described with reference to Figure 1, namely:

- a tank 1, preferably made of steel, and preferably enameled on its wall internal ;

- an inlet connection 2 and an outlet connection 3, preferably welded to the external wall of the tank 1 in the lower part of this tank, at the level of corresponding openings made in this external wall; And

- an entry rod 4 carried by the entry point 2 so as to extend axially to the entry point and inside the tank 1, and an exit rod 7 carried by the exit point 3 so as to extend axially to the inlet connection and inside the tank 1.

[00035] The inlet and outlet connections are for example also made of steel.

[00036] In this non-limiting example, the entry point 2 and the exit point 3 are located in the lower part of the tank when the latter is in the installed position, and oriented so that the entry rod 4 and the outlet rod 7 extends substantially parallel to the interior of the tank 1.

[00037] The tank 1 further comprises a heating element intended to be immersed in the water of the tank 1 in order to heat the water present in the lower part of the tank 1 in the installed position. In accordance with the invention, this heating element consists, in the example shown, of two flexible resistive wires, each electrically insulated, and whose ends 10a, 10b on the one hand, and 11a, 11b on the other hand , come out of tank 1 for connection to an external power supply (not shown). The tank 1 is also shown in the installed position, a position in which it can be seen that the length portion located between the ends 10a, 10b or 11a, 11b rests by gravitation at the bottom of the tank 1, forming a random cluster 12.

[00038] Each flexible resistive wire mainly and preferably comprises a core made of a metal wire resistant to the passage of current, and an electrical insulation sheath, for example made of silicone, surrounding the core.

[00039] As the wires are immersed in the water of the tank and this water is likely to be drunk by a user, the material of the sheath is preferably chosen to meet the requirements of existing health and potability standards relating to electrically insulating materials authorized for food contact.

[00040] In a variant embodiment not shown, the heating element can consist of a single flexible resistive wire, a portion of its length is intended to rest by gravitation at the bottom of the tank when the latter is in installed position. An advantage of providing a plurality of wires lies in the fact that it is possible to regulate different power levels, or even use several phases of the external power supply.

[00041] By using a substantial length of wire which forms the random cluster 12, the tests have shown that it is possible to obtain a power volume density (capacity of the cluster to transmit energy, at a given volume) sufficient to heat the water in the lower part of the tank.

[00042] Figure 5 gives comparative tests obtained with a wire (in accordance with the invention), with a conventional copper shielded resistance of power equal to 350 Watts, with a conventional copper shielded resistance of power equal to 2500 Watts, with a known soapstone resistance of power equal to 2400 Watts.

[00043] In the example of Figure 5, the wire used has a diameter of 3 millimeters and a linear power of 57 W/m, which makes it possible to obtain a power density of 8064 W/L. Of course, other power density can be obtained with other wires. The choice of wire is made according to normative constraints, design constraints and/or cost. As a non-limiting example, we will preferably choose a wire whose external diameter (sheath included) is between 2 and 7 millimeters. The necessary length of the wire forming the cluster will depend directly on the desired power (for example typically between 200 and 3500 Watts in the non-limiting case of domestic water heaters). The power density is calculated by dividing the power of the wire (in W) by the volume occupied. The occupied volume can be modeled in 3D, or calculated experimentally. For a wire of length L and diameter D, the occupied volume V is given by the following equation:

[00044] It should be noted that the wire is preferably chosen so that the volume occupied is as small as possible.

[00045] In the example shown in Figure 3, the tank 1 comprises a plug 13 removably fixed to the tank 1 to sealingly seal an opening passing through the wall of the tank 1. Given its position in the lower part, the plug 13 can advantageously serve as a drain plug. As seen in this figure, the ends 10a, 10b on the one hand, and 11a, 11b on the other hand, for the two flexible wires, exit the tank 1 at the level of the opening and the drain plug 13. In a variant not shown, it can also be provided that the plug 13 carries a thimble comprising a or thermostats allowing temperature measurement for temperature regulation purposes by a regulation circuit external to the tank.

[00046] The tank 1 further preferably comprises an anode for protecting the tank 1 against corrosion (not shown), for example a sacrificial anode made of magnesium alloy or aluminum alloy, arranged so as to extend longitudinally inside the tank 1. In a possible embodiment, the corrosion protection anode can be carried by the plug 13. Alternatively, it is possible to envisage that the protection anode is carried in the extension axial of the entry rod 4.

[00047] In the example shown in Figure 3, the inlet tap 2, the outlet tap 3 and the plug 13 through which the ends of the flexible wire(s) emerge, are located in the lower part of the tank 1 in installed position. Other arrangements are of course possible without departing from the scope of the present invention. In another embodiment not shown, the ends of the flexible wire(s) can emerge at an element other than the plug 13, for example a flange, removably fixed to the tank 1, on the periphery of a opening passing through the wall of the tank 1. The flange can be similar to the flange 9 of Figure 1, fixed laterally on the tank and carrying the ends of the flexible wire(s) (instead of the shielded resistor 5 of Figure 1), or even a thermowell containing one or thermostats and/or a protective anode.

[00048] Figure 4 illustrates another embodiment of a tank according to the invention for a water heater, particularly suitable for a so-called “under sink” configuration.

[00049] Unlike the “on sink” configuration seen previously, the inlet connection 2 and the outlet connection 3 of the tank are here located in the upper part of the tank 1 when the tank is in the installed position. The entry rod 4 always has a part 41 forming a jet breaker with side openings. However, in order to respect the stratification phenomenon, the inlet rod 4 is much longer so that this part 41 forming a jet breaker is found in the lower part of the interior of the tank 1. [00050] Just as in the embodiment described above with reference to Figure 3, the heating element consists, in the example shown in Figure 4, of two flexible resistive wires, each electrically insulated, and of which the ends 10a, 10b on the one hand, and 11a, 11b on the other hand, emerge from the tank 1 for connection to an external electrical power supply (not shown). The tank 1 is also shown in the installed position, a position in which it can be seen that the length portion located between the ends 10a, 10b or 11a, 11b rests by gravitation at the bottom of the tank 1, forming a random cluster 12 .

[00051] In a variant embodiment not shown, the heating element can consist of a single flexible resistive wire, a portion of its length is intended to rest by gravitation at the bottom of the tank when the latter is in the installed position.

[00052] Here again, the tank 1 comprises a plug 13 removably fixed to the tank 1 to sealingly seal an opening passing through the wall of the tank 1. As can be seen in this figure, the ends 10a, 10b d on the one hand, and 11a, 11b on the other hand, for the two flexible wires exit from the tank 1 at the level of the opening and the plug 13. In a variant not shown, it can also be provided that the plug 13 carries a thermowell comprising one or more thermostats allowing temperature measurement for the purposes of temperature regulation by a regulation circuit external to the tank.

[00053] The tank 1 further preferably comprises an anode for protecting the tank 1 against corrosion (not shown), for example a sacrificial anode made of magnesium alloy or aluminum alloy, arranged so as to extend longitudinally inside the tank 1. In a possible embodiment, the corrosion protection anode can be carried by the plug 13. Alternatively, it is possible to envisage that the protection anode is carried in the extension axial of the output rod.

[00054] In the example shown in Figure 4, the inlet tap 2, the outlet tap 3 and the drain plug 13 through which the ends of the flexible wire(s) emerge, are located in the upper part of the tank 1 in installed position. Other arrangements are of course possible without departing from the scope of the present invention. For example, in another embodiment not shown, the ends of the flexible wire(s) can come out at an element other than the plug 13, for example a flange, fixed so removable to the tank 1, on the periphery of an opening passing through the wall of the tank 1. The flange can be similar to the flange 9 of Figure 2, fixed laterally on the tank and carrying the ends of the flexible wire(s) ( instead of the shielded resistor 5 in Figure 1), or even a thermowell containing one or more thermostats and/or a protective anode.

Whatever the embodiment carried out, the present invention has numerous advantages:

[00056] Thus, the wire(s) constituting the heating element are submerged, which constitutes, as we saw in the introduction, a more effective solution than heating from the outside of the tank.

[00057] In addition, the wire(s) constituting the heating element having a low surface power density, they are less sensitive to the quality of the water. This increases the lifespan of the heating element compared to those of known submerged heating element solutions.

[00058] Furthermore, the power volume density offered by the random pile of wires is much greater than the power volume density of a sheath containing a soapstone resistor. This results in a gain in space requirements.

[00059] Furthermore, in the embodiments illustrated in Figures 3 and 4, it is no longer necessary to provide a large flange. In fact, only a small element, for example the drain plug, can be used here to allow the ends of the wire (or wires) constituting the heating element to come out of the tank to be connected to an external power supply. In the embodiments for which the plug 13 also carries the temperature probes and/or an anode for protection against corrosion, or those for which the protective anode is carried by the inlet or outlet rod, we 'frees from the need to use the flange 9 and to have a corresponding opening on the bottom of the tank 1b as illustrated in Figures 1 and 2. The two bottoms of the tank 1 and 1 b can thus be identical, which reduces still manufacturing costs.

[00060] Finally, all assembly operations are considerably simplified.

[00061] Although the preceding detailed description has only been made in the context of tanks for electric water heaters, the present invention applies to any storage tank comprising a heating element intended to be immersed in the water of the tank.

Claims

Claims [Claim 1] Tank (1) for storage hot water comprising an inlet tap (2) for bringing water into the tank (1), an outlet tap (3) for letting water out hot water contained in the tank (1) and a heating element intended to be immersed in the water of the tank (1) in order to heat the water present in the lower part of the tank (1) in the installed position, characterized in that said heating element comprises at least one electrically insulated resistive flexible wire, the ends of which (10a, 10b) come out of the tank (1) for connection to an external electrical power supply, and of which at least a portion of length is located between the ends (10a, 10b) is intended to rest by gravitation at the bottom of the tank (1) in said installed position, forming a random cluster (12). [Claim 2] Tank (1) according to claim 1, in which the heating element comprises a plurality of flexible resistive wires, the ends of which (10a, 10b, 11a, 11 b) emerge from the tank (1) for connection to an external electrical power supply, each wire being electrically insulated and having at least a portion of length between its ends (10a, 10b; 11a, 11 b) intended to rest by gravitation at the bottom of the tank (1) in said installed position, in forming with the other wires said random cluster (12). [Claim 3] Tank (1) according to any one of the preceding claims, in which said at least one wire comprises a metallic core, and an electrical insulation sheath, surrounding said core. [Claim 4] Tank (1) according to any one of the preceding claims, further comprising an anode for protecting the tank (1) against corrosion, said anode extending longitudinally inside the tank (1) . [Claim 5] Tank (1) according to any one of the preceding claims, further comprising an element (13) removably fixed to the tank (1) to sealingly seal an opening passing through the wall of the tank (1). ), the ends (10a, 10b; 11a, 11 b) of said at least one wire or of said plurality of wires emerging from the tank (1) at the level of the opening and of said element (13). [Claim 6] Tank (1) according to the combination of claims 4 and 5 in which the protective anode is carried by said element (13). [Claim 7] Tank (1) according to any one of claims 5 or 6, in which the inlet tap (2) and the outlet tap (3) are located in the lower part of the tank (1) in position installed. [Claim 8] Tank (1) according to any one of claims 5 or 6, in which the inlet tap (2) and the outlet tap (3) are located in the upper part of the tank (1) in position installed. [Claim 9] Tank (1) according to any one of claims 5 to 8, wherein said element is a flange located on a side wall of the tank (1) in the installed position. [Claim 10] Tank (1) according to claim 7, in which said element (13) is located in the lower part of the tank (1) in the installed position, and forms a drain plug. [Claim 11] Tank (1) according to claim 8, in which said element (13) is located in the upper part of the tank (1) in the installed position.