Abstract:
A water heating device which includes a thermally insulated water storage tank having a side wall and being configured to receive drinking water, a water inlet as an inlet for drinking water, a water outlet as an outlet for hot water, and a heating unit arranged inside the water storage tank adapted to heat water inside the water storage tank. The heating unit is inclined with respect to the side wall of the water storage tank, in particular at an angle other than 90° with respect to the side wall of the water tank.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to a water heating device. 
         [0002]    Water heating devices consists of a storage water tank and a heat source which heats the tank. In many cases the heat up of the water is executed with an electric element for example a sheathed electric heating element. The surface of the heating element can be immersed in potable water of the storage tank. The heating element typically comprises a flange and is screwed into the storage water tank. In order to ensure that the storage water tank is sealed, a sealing gasket is provided between the flange of the heating element and the tank. 
         [0003]    In order to be able to control the water temperature in the storage water tank, the storage water tank typically comprises a temperature regulation unit which controls a heating element to heat the water inside the storage water tank according to a set point set by the consumer. To avoid overheating of the water inside the water tank, a temperature and pressure relief valve and a temperature cut off device is needed. 
         [0004]    In order to reduce corrosion of the storage water tank, a sacrificial anode is provided. 
         [0005]    The above described water tank increases the maintenance expense because in case of a defect heating element the complete water content of the tank needs to be drained. Furthermore, in case of a replacement of a defect element, there is a risk of leaking water out of a not proper sealed flange. If no water is present in the water tank and the fired heating element is not cooled by water and is thus in a dry fire operation, there is a high risk that the heat element can be damaged due to overheating of the heat element. 
         [0006]    Sacrificial anodes may corrode fast if the water inside the water tank has a high conductivity and the water has a high salt content. The corrosion process of the sacrificial anode may increase the maintenance expense because the anode needs to be replaced more frequent. Furthermore, a unwanted high production rate of hydrogen occurs because of the electrolysis process during the operation of the sacrificial anode may also be present. During the tapping process the released hydrogen gas produces unwanted noise and there is as well an increased fire risk. 
       SUMMARY OF THE INVENTION 
       [0007]    It is an object of the invention to provide an improved water heating device. 
         [0008]    This object is solved by a water heating device which comprises a thermally insulated water storage tank having a side wall which is configured to receive drinking water. The water heating device furthermore comprises a water inlet for the incoming drinking water, a water outlet for the outgoing hot water and a heating unit inside the water tank adapted to heat water inside the water tank. The heating unit is inclined with respect to the side wall of the water tank. The angle between the heating unit and the side wall of the water tank is an angle other than 90°. 
         [0009]    According to an aspect of the invention, the water tank comprises a pocket which is adapted or configured to receive at least part of the heating unit. 
         [0010]    According to a further aspect of the invention, the pocket is inclined with respect to the side wall of the water storage tank. 
         [0011]    To a further aspect of the invention, the pocket is designed like a tube which is welded or glued to the side wall of the water storage tank. The tube end which is in contact with potable water is closed using a welded cap. The tube end which is opposite to the closed end has an open end. 
         [0012]    To a further aspect of the invention, the length of the heating element is less than the length of the tube. Hence, a portion in the open end tube between an end of the heating unit and the side wall is not directly heated. Alternatively the heating unit comprises a heating element (e.g. in form of a heating wire) which does not extend along the entire length of the heating unit thus a section of the heating unit is not directly heated by the heating element. This reduces the temperature in the wiring housing. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]      FIG. 1  shows a schematic representation of a water heating device according to a first embodiment; 
           [0014]      FIG. 2  shows a schematic representation of a water heating device according to a second embodiment; 
           [0015]      FIGS. 3A-3C  show different representations of a heating element according to the invention; 
           [0016]      FIG. 4A  shows a schematic representation of a water heating device according to a third embodiment; 
           [0017]      FIG. 4B  shows a schematic representation of a water heating device according to the prior art; 
           [0018]      FIG. 5  shows a schematic representation of a part of  FIG. 4A ; 
           [0019]      FIG. 6  shows a schematic representation of part of a water heating device according to a fourth embodiment; and 
           [0020]      FIG. 7  shows a schematic representation of a heating element according to a fifth embodiment. 
       
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
       [0021]    It is to be understood that the figures and descriptions of the present invention have been simplified to illustrate elements that are relevant for a clear understanding of the present invention, while eliminating, for purposes of clarity, many other elements which are conventional in this art. Those of ordinary skill in the art will recognize that other elements are desirable for implementing the present invention. However, because such elements are well known in the art, and because they do not facilitate a better understanding of the present invention, a discussion of such elements is not provided herein. 
         [0022]    The present invention will now be described in detail on the basis of exemplary embodiments. 
         [0023]      FIG. 1  shows a schematic representation of a water heating device according to a first embodiment. The water heating device  100  comprises a thermally insulated metal water storage tank  100   a  for receiving potable water which needs to be heated. The storage tank  100   a  comprises a hot water outlet  101 , a cold water (potable water) inlet  102  and an inlet  103  for a pressure and temperature relief valve (“P &amp; T valve”). A metal tube  104  is welded into the metal water storage tank  100   a . The end of the metal tube  104  which is in contact with potable water is closed with a welded cap. The opposite end of the tube  104  is open to the atmosphere. According to the invention, the metal tube  104  is welded to the side wall  100   b  of the tank and comprises an inclination. A heating element  105  is inserted into the tube  104  such that the tube transfers heat to the water. By the inclination of the tube  104  and thus the inclination of the heating element  105 , the water inside the water tank is efficiently heated. Because of the pocket design of the welded tube  104  it is possible to service a damaged heat element  105  without draining the water content of the water storage tank  100   a . The inner diameter of the tube  104  is larger than the outer diameter of the heat element  105  in order to incorporate the heat element  105 . Thus, the maintenance of the water heating device is significantly improved without risk of leaking water after a service. 
         [0024]    The water storage tank  100   a  may comprise a second tube  106  which is welded into the water tank  100   a . This second tube  106  is a metallic sleeve tube  106  with an open end outside the water tank to insert a temperature sensor  107 . The temperature sensor  107  may be connected to a safety cut out  108  or a thermostat. Optionally, the second tube  106  is inclined towards the side wall of the water tank. Optionally, the angle of the inclination of the first tube does not correspond to the angle of inclination of the second tube. 
         [0025]    According to an aspect of the invention, the outer surfaces of the first and second tubes  104 ,  106  can be enamelled. In particular, only those portions of the outer surfaces of the first and second tube  104 ,  106  which are in contact with water are enamelled. 
         [0026]    Optionally, the water tank  100   a  also comprises a sensor and a further temperature sensor unit  109 , which exists of a plurality of temperature sensors vertically arranged like a chain. 
         [0027]    Furthermore, optionally an anode rod  110  is provided to avoid corrosion of the metallic tank. In addition, the anode rod  110  is used for a dry fire prevention sensor. The electronic impressed anode rod  110  is connected to an electronic device  111  which may be arranged at the outside of the water tank  100   a.    
         [0028]    Optionally, the water tank  100   a  may comprise further an inlet port and a outlet port  112 ,  113  for an add-on heating unit or heat generator to be retrofitted later. This add-on heat generator can be a heat pump. The heat pump can be connected to the electronic unit  111 . In particular, an electrical connection can be provided to the electronic device  111 . 
         [0029]      FIG. 2  shows a schematic representation of a water heating device according to a second embodiment. The water tank  100   a  comprises a hot water outlet  101 , a cold water inlet  102 , an inlet  200  for a P &amp; T valve. Furthermore, a first tube  104  is welded or glued to the side wall of the water tank  100   a . The closed end of the tube  104  which is in contact with potable water can be covered by a welded cap. The opposite end is open to the atmosphere. The first tube  104  is a heat exchanger if a heating element  105  is assembled inside it. The outside diameter of the heating element  105  is smaller than the inside diameter of the first tube  104 . As shown in the first embodiment, the first tube  104  is arranged with an inclination towards the side wall of the water tank. Thus, the water in the cold sump section can be heated advantageously. This increases the mix water amount of the usable tank volume. 
         [0030]    As shown in the first embodiment, a second tube can be provided in which a temperature sensor  107  is inserted. Furthermore, a wiring enclosure  120  is connected to the electric heat element  104  via an electrical grid with the wires  122  and  123 . The wire  121  is the ground line for safety reasons. This line  121  needs to be grounded via any metallic part of the tank. In  FIG. 2 , convection C is depicted, to illustrate cold water flowing down towards the heating element  105 , where the water is heated and due to the heat convection, the heated water then moving upwards. Because of the inclination of the heating element  105  also water of the cold sump of the water tank  100   a  is heated. 
         [0031]      FIGS. 3A-3C  show different views of the heating element according to the invention. In  FIG. 3A , the heating element  105  is a ceramic heat element and may comprise of a number of ceramic elements  114  which are stacked together using a central thread bar.  FIG. 3B  shows a single ceramic element and  FIG. 3C  shows a schematic cross section of the heating element  105 . The heating element comprises a plurality of ceramic fins  115  which transfers heat from the spiral heating wire to the inner wall of the surface of the tube  104 . The ceramic nature of the fin  115  creates spacing for the high voltages of the hot wire in front of the conductive tube  103 . Between the fins, a number of gaps  116  provides enough spacing for the spiral heat wire. In the middle of the heating element  105 , a central bore hole  117  is provided. This central bore hole  117  acts like a gap for the central thread bar. Each of the ceramic elements is divided from the following by a heal  118  providing a distance between adjacent ceramic elements. 
         [0032]      FIG. 4A  shows a schematic representation of a water heating device according to a third embodiment. The water heating device  100  comprises a thermally insulated metal water storage tank  100   a  for receiving potable water which needs to be heated. The water storage tank  100   a  comprises a shell section or side wall  100   b , a top section  100   d  as well as a bottom section  100   c . The top and bottom section  100   d ,  100   c  is welded to the side wall  100   b . At the lower part of the side wall  100   b  a metal tube  104  is welded to the side wall  100   b . The end  104   a  of the metal tube  104  is in contact with potable water and closed with a welded cap. Preferably, the metal tube  104  is inclined at an angle from 5° to 30° with respect to a horizontal plane. Inside the metal tube  104  a heating element  105  is inserted.  FIG. 4A  shows the closed end  104   a  of the metal tube  104 . It is arranged in the area of the bottom section  100   c . This arrangement of the metal tube  104  and thus the arrangement heating element  105  is advantageous, because the water which of the bottom section  100   c  is also heated. 
         [0033]    In  FIG. 4A  two convection zone C 1 , C 2  are depicted, they are active during times, when the heating element  105  is activated. As declared in  FIG. 4A , especially the second convection current C 2  heats the lower part of the bottom section  100   c . Thus, also the water inside the bottom section  100   c  is heated as well. 
         [0034]    In contrast, in  FIG. 4B , where the heating element is arranged horizontally it is visible that the convection currents C 3 , C 4  do not reach into the bottom section  100   c  of the water tank. The bottom section remains cold which reduces the amount of usable water of the tank content. 
         [0035]      FIG. 5  shows a schematic representation of a part of  FIG. 4A . In the lower part of the shell section or the side wall  100   b , the open end of the metal tube  104  is depicted. The open end of the metal tube  104  can be welded to the shell section  100   c  for example by means of a welded joint  100   e . Furthermore, the bottom region  100   c  and the shell section or the side wall  100   b  can also be welded together by means of a welded round joint  100   f . According to the invention, the distance between the welded joint  100   e  for the metal tube  104  and the welded joint  100   f  for the side wall  100   b  and the bottom section  100  are arranged not closer than 25 mm from each other. In other words, the minimum distance between the two welded joints is more than 25 mm. The reason for this minimal distance is to avoid any thermal deformation during the welding process and durability according to required pressure lifetime cycle. 
         [0036]      FIG. 6  shows a schematic representation of a part of a water heating device according to a fourth embodiment. In  FIG. 6 , the storage tank  100   a  as well as the bottom section  100   c  is depicted. Furthermore, the inclined metal tube  104  as well the inclined heating element  105  is depicted. Preferably, the heating element  105  comprises a section  105   e  which is not heated. This section  105   e  is preferably arranged at the proximal end of the heating element  105 . 
         [0037]      FIG. 7  shows a schematic representation of a heating element according to a fifth embodiment. In  FIG. 7 , a schematic cross section of the heating element is depicted. The heating element  105  thus comprises two bolts  105   b  connected to each heating wire  105   d . The length of the two bolts  105   b  will determine the non heated section  105   e  of the heating element. The heating element may also comprise high conductive ceramic fins  105   c  in order to avoid a short between the single element wire The arrangement of the ceramic fins create a duct for a single heat element and transfers the heat to the surrounding tube wall  105   f.    
         [0038]    According to the invention, the not-heated section  105   e  is provided so that the temperature inside the wiring enclosure  108  does not exceed a threshold value. Accordingly, the section  105   e  acts like a cooling section. 
         [0039]    While this invention has been described in conjunction with the specific embodiments outlined above, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art. Accordingly, the preferred embodiments of the invention as set forth above are intended to be illustrative, not limiting. Various changes may be made without departing from the spirit and scope of the inventions as defined in the following claims. 
         [0040]    In addition, it is noted that citation or identification of any document in this application is not an admission that such document is available as prior art to the present invention. 
         [0041]    It is also noted that in this disclosure and particularly in the claims and/or paragraphs, terms such as “comprises”, “comprised”, “comprising” and the like can have the meaning attributed to it in U.S. Patent law; e.g., they can mean “includes”, “included”, “including”, and the like; and that terms such as “consisting essentially of” and “consists essentially of” have the meaning ascribed to them in U.S. Patent law, e.g., they allow for elements not explicitly recited, but exclude elements that are found in the prior art or that affect a basic or novel characteristic of the invention. 
         [0042]    It is further noted that the invention does not intend to encompass within the scope of the invention any previously disclosed product, process of making the product or method of using the product, which meets the written description and enablement requirements of the USPTO (35 U.S.C. 112), such that applicant(s) reserve the right to disclaim, and hereby disclose a disclaimer of, any previously described product, method of making the product, or process of using the product.