Patent Publication Number: US-2003226523-A1

Title: Supercharged hot water heater

Description:
PRIORITY CLAIM  
     [0001] This application claims the benefit of U.S. Provisional Patent Application Serial No. 60/60/387,010 filed on Jun. 6, 2002, which is hereby incorporated by reference in its entirety. 
    
    
     
       FIELD OF THE INVENTION  
       [0002] The present invention relates generally to hot water heaters and more particularly to near boiling hot water heaters.  
       BACKGROUND OF THE INVENTION  
       [0003] Hot water dispensers that mount to sinks are common. Such dispensers consist of two main parts, a water tank with a heater and a faucet. In the water tank water is heated by the heater and stored until needed. The tank and associated plumbing are usually installed below the sink where they are out of the view of the user. The faucet is usually mounted above the sink such that a user can dispense the amount of hot water desired while any excess hot water falls harmlessly into the sink. Such dispensers are typically used by opening a valve on the faucet to dispense the hot water stored in the tank to the user who can then enjoy, for example, a hot cup of soup, hot chocolate, or tea. Several different methods may be used to open the valve such as twisting a handle, depressing a lever, or pushing a button on the faucet.  
       [0004] A typical prior art hot water dispenser, such as the In-Sink-Erator, Instant Hot™, hot water dispenser, model number H-990-W-5, is shown in FIG. 1. Such prior art hot water dispensers  10  are typically mounted such that the water tank  12 , with the heater  18 , is attached to a wall beneath the sink by well known means. The faucet  34 , with the activating valve  32 , is typically attached to the upper surface of the sink through a hole in the sink cabinet&#39;s upper surface and is oriented such that any water emanating from the faucet will fall into the sink and drain away. Tubing  20 ,  26 ,  28 , and  30 , typically copper, stainless steel, or plastic, connects the faucet  34  with the tank  12 . Tubing  28  allows hot water  16  in the tank  12  to flow to faucet  34 . Tube  30  is connected to a water supply by any suitable means known in the plumbing arts. Prior art hot water dispensers typically heat the dispensed water  16  to a temperature below boiling, typically between 180° F. and 190° F.  
       [0005] Tank  12  is made of any suitable material such as stainless steel, copper, or high temperature plastic that can hold the heated water  16  in the tank. The water  16  in the tank  12  is heated by heating element  18 . Heating element  18 , in the prior art, is typically a 750-watt electric heating element that is regulated by a temperature adjustable thermostat  14  (electrical connection not shown).  
       [0006] A fixed baffle  22  divides the tank  12  into a hot water storage area  40  and an expansion area  24 . Tube  26  acts as a vent for expansion area  24  so that neither low pressure nor high pressure will be created to restrict the flow of water into and out of expansion area  24 . The baffle  22  is a rigid or semi-rigid material, such as stainless steel, copper or heat resistant plastic to which venturi  38  may be attached. The expansion area allows for any water remaining in tube  28  after water flow into the tank is shut off through tube  20  to drain into the expansion area through hole  42 . Additionally, because the cool water that has replaced the water used expands by about 8 percent as it is heated, an expansion area must be provided or water will be forced out of tube  28  where it would drip from faucet  34 . Consequently the heated and expanded water flows into venturi  38  through hole  42  and into expansion area  24 . The venturi  38  is affixed about the lower end of tube  28 . As water is forced out of tube  28  venturi  38  creates low pressure at opening  42  as water in tube  28  flows past it. The low pressure draws water from expansion area  24  through the opening thus draining any accumulated water in expansion area  24 .  
       [0007] In order to dispense hot water  16 , the user activates a spring-loaded, twist-actuated valve  32 , although any type of on-off water valve may be used, to allow cold water in tube  30  to flow into tube  20 . Tube  20  is connected to the bottom of tank  16  at inlet  36 . As relatively cold water enters the tank  12  through inlet  36 , hot water is forced out of tank  12  and into dispensing tube  28  and ultimately through faucet  34 . Faucet  34 , In-Sink-Erator™ model number 41760, amongst other things, constitutes a mounting device for valve  32  and a conduit for various tubes carrying water to and from the tank  12 . After an amount of hot water is dispensed in this fashion, the cold water received at inlet  36  is heated in preparation for the next activation of valve  32 .  
       [0008] In some applications it is desirable to dispense water hotter than 190° F. For example some users can taste the difference between tea that is brewed using water at 190° F. versus water that is near boiling (e.g., 205° F.-212° F.), and these users prefer the latter temperature. Water at near boiling temperatures may be desirable for other reasons as well.  
       [0009] Because of the desire for water at near boiling temperatures, other types of prior art hot water dispensers have been designed that heat the dispensed water to near boiling, and some even flash the water to steam before dispensing the water or steam. These prior art hot water dispensers provide hot water at or above 205° F. or may even provide steam for such uses as cappuccino. These types of prior art hot water dispensers provide near boiling hot water by utilizing highly accurate (and consequently expensive) thermostats to continuously cycle the heating element on and off in order to maintain the requisite near boiling water temperature.  
       [0010] These types of near boiling dispenser must contend with the possibility that the heated water may boil and turn into steam, thereby greatly expanding in volume and providing the potential for damaging components and injuring users. While steam generation is desired in some circumstances, the hot water dispenser must be designed to prevent the damaging effects of steam generation. In order to prevent damage from steam generation, typical prior art hot water dispensers typically utilize a pressure relief valve on the tank to prevent overpressure in the tank.  
       [0011] The reader is referred to the following references for further background regarding the design and operation of prior art hot water heaters, which are incorporated herein by reference in their entirety: U.S. Pat. No. 6,266,485, U.S. Pat. No. 6,256,465, U.S. Pat. No. 6,094,524, U.S. Pat. No. 6,069,998, U.S. Pat. No. 4,513,887, and pending application Ser. No. 09/564,199 filed May 4, 2000.  
       [0012] It has generally been regarded as difficult to design a relatively cheap, reliable, and safe system that can dispense near boiling water. Prior art hot water dispensers that dispense near boiling hot water are expensive to manufacture and operate. In this regard, it should be noted that the heat loss rate of water increases as its temperature increases. In other words, 205° F. water cools quicker than water between say 180° F. to 190° F. Thus the higher temperature water must be reheated more often than cooler water to keep it at the desired temperature, which raises energy costs. To compensate for the increased heat loss rate of higher temperature water, additional insulation can be used around the tank. Of course more insulation leads to higher manufacturing costs. Additionally, because the water is being held at a temperature closer to its boiling point, a more accurate thermometer must be used to avoid overheating the water. Overheating the water could lead to unwanted steam generation and higher tank pressure than the tank is designed to withstand. A more accurate thermometer is expensive, which again leads to higher costs. Additionally, pressure relief or safety valves to protect against the possibility of damage due to steam generation further raise manufacturing costs.  
       SUMMARY OF THE INVENTION  
       [0013] Embodiments of the present invention provide a hot water dispenser capable of heating water to near boiling temperatures (e.g., 205° F. to 212° F.). When water at near boiling temperatures is required, a secondary heating element is activated. The secondary heating element is thermally coupled to the dispensing tube so that the water in the tube may be further heated as it passes through the dispensing tube from the tank to the dispensing outlet. Heating the water to near boiling just prior to its being dispensed reduces energy costs because the near boiling temperature water is not stored and allowed to cool. Additionally, the need for expensive insulation or expensive thermostats is reduced. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0014] Other objects and advantages of the invention will become apparent upon reading the following detailed description and upon reference to the drawings, in which  
     [0015]FIG. 1 is a cross-sectional view of a conventional hot water dispenser.  
     [0016]FIG. 2 is a cross-sectional view of a hot water dispenser with a secondary heating element.  
     [0017]FIG. 3 is a cross-sectional view of the secondary heating element.  
     [0018]FIG. 4 is a graph of the temperature increase of the dispensed water as compared to the temperature of the water in the tank when a secondary heating element adjusted to provide 750 watts of heat output is used.  
     [0019]FIG. 5 is a graph of the temperature increase of the dispensed water as compared to the temperature of the water in the tank when a secondary heating element adjusted to provide 1000 watts of heat output is used.  
     [0020]FIG. 6 is a graph of the temperature increase of the dispensed water as compared to the temperature of the water in the tank when a secondary heating element adjusted to provide 1300 watts of heat output is used. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
     [0021] In the disclosure that follows, in the interest of clarity, not all features and details of actual implementations of a hot water heater are necessarily described. It will of course be appreciated that in the development of any such actual implementation, as in any such project, numerous engineering and design decisions must be made to achieve the developer&#39;s specific goals and subgoals (e.g., compliance with mechanical and business-related constraints), which will vary from one implementation to another. Moreover, attention must necessarily be paid to proper engineering and design practices for the environment in question. However, while such a development effort for a hot water heater might be complex and time-consuming, it would nevertheless be a routine undertaking for those of skill in the art having the benefit of this disclosure.  
     [0022]FIG. 2 is a cross-sectional view of the type of hot water dispenser shown in FIG. 1, but which incorporates a secondary heating element  50  in accordance with one embodiment of the disclosed invention.  
     [0023] Secondary heating element  50  is envisioned as providing a high heat output in a small volume and is preferably rated for 1000 watts at 115 volts. However, any type of heating element, whether gas or electric, will work as long as enough heat is generated to provide the desired water temperature at the desired water flow rate.  
     [0024] Secondary heating element  50  is depicted wrapping about tube  28 . Tube  28  is preferably stainless steel but may be copper, or any other suitable material that can affect heat transfer between secondary heating element  50  and tube  28 . During testing, secondary heating element  50  was thermally coupled, by soldering, alongside and in parallel orientation, to tube  28 . (Further details concerning a suitable secondary heating element are disclosed below). However, it is believed to be preferable to wind tube  28  about the exterior of heating element  50  (as shown) resulting in a mechanical compression fit between tube  28  and secondary heating element  50  and which facilitates increased heat transfer. However, any method of thermally coupling tube  28  and secondary heating element  50  about the exterior or interior of tube  28 , such that the heat generated by secondary heating element  50  may be transferred to the water inside of tube  28 , may be used. Secondary heating element  50  is preferably located as near as is reasonable to the dispensing outlet of faucet  34  to minimize cooling and to prevent steam from forcing near boiling water out of the faucet at high speed.  
     [0025] As in the prior art, water in tank  12  is preferably held at approximately 180° F.-190° F. As water is removed from tank  12  through tube  28 , secondary heating element  50  raises the temperature of the water in tube  28 , via heat transfer through tube  28 , to near boiling temperature (e.g., 205° F.-212° F.) precluding the need to maintain water in tank  12  at near boiling temperatures. In addition to this safety and energy efficiency advantage, the present embodiment allows water to be dispensed at either hot (180° F.-190° F.) or near boiling (205° F.-212° F.) temperatures at the user&#39;s discretion. The tank  12  is preferably not pressurized but vented as described herein, although it could be pressurized with well-known modifications, as one skilled in the art will recognize.  
     [0026] The heat transfer rate should be matched to the desired flow characteristics of the hot water dispenser heater so that the appropriate dispensing temperature can be achieved. Preferably, a suitable heating element will provide an approximately 20° F. boost in water temperature at a water flow rate of approximately 0.5 gallons per minute, which would boost the water temperature from, say 180° F.-190° F. in the tank to 205° F.-210° F. Assuming perfect heat transfer between the secondary heating element and tube  28 , it would be necessary to provide 68.67 watts of energy to the water to raise the temperature of 1 fluid ounce of water 1° F. each second.  
     [0027] Secondary heating element  50  is attached to a switch  54 , such as a THERMO DISC™ model 36T, by wires  52 . Wires  52  are in turn attached to a 115V A/C power source. Switch  54  is preferably a temperature-sensing switch. The thermal sensing portion of switch  54  is thermally coupled to tube  28  as shown and is held in place by mechanical means, such as welding, soldering, bolts, or a compression fit inside of the faucet  34 , allowing switch  54  to sense the temperature of tube  28 .  
     [0028] Switch  54  preferably goes to an off condition when tube  28  reaches a predetermined temperature, preferably 250° F., although any temperature in excess of the boiling point of water could be used. A cutoff temperature of 250° F. allows for tube  28  to be overheated but not excessively so. Slightly overheating tube  28  is allowable immediately prior to initiating water flow through tube  28  and again just after water flow through tube  28  ceases. Slightly overheating tube  28  is allowed to give some leeway for preheating tube  28 , user error, etc., but the temperature must also be low enough that components are not damaged or users injured. Once switch  54  goes to an off condition, the user may reset the switch to activate secondary heating element  50  once temperatures have been allowed to cool below the trip temperature of switch  54 . However, alternatively any switch that will activate secondary heating element  50  could be used, and such a switch need not be a temperature sensing switch.  
     [0029] By heating the water as it is dispensed, the need for an expensive, accurate thermostat is eliminated. An expensive thermostat is not needed because water is no longer held in the tank at near boiling temperatures, which requires careful monitoring to prevent steam generation. As noted earlier, steam generation would damage components and possibly injure a user. When water is held at temperatures that are not so close to boiling, such as in the current embodiment of this invention, safety is improved. Therefore, a slightly less accurate and consequently less expensive conventional thermostat  14  may be used to monitor the water temperature in the tank.  
     [0030]FIG. 3 is a cross-sectional view of the hot water dispenser secondary heating element and faucet  34  assembly. When more “normal” hot water (180° F.-190° F.) is desired by the user, the user simply activates valve  32  as in the prior art. However, when near boiling water is desired, switch  54  is activated. Switch  54  activates secondary heating element  50  as previously described. After switch  54  is activated a few seconds may be required to allow secondary heating element  50  to heat itself and tube  28  before any appreciable amount of heat can be transferred to the water  16  in tube  28 . In a preferred embodiment, valve  32  is then manually activated, by the user, causing water  16  to flow into tank  12  (not pictured) and forcing preheated water  16  through tube  28  where the water&#39;s temperature is boosted as previously described. If valve  32  is activated prior to or simultaneously with switch  54  then “normal” hot water will be dispensed during those few seconds required by secondary heating element  50  to heat up. Once valve  32  is manually deactivated, the flow of water through tube  28  ceases causing the temperature of tube  28  to rise. Switch  54  senses the rise in temperature of tube  28 , causing secondary heating element  50  to be deactivated as discussed earlier.  
     [0031] In a modified embodiment, switch  54  can be connected to a timing circuit (not shown) which can electrically activate valve  32  without further intervention by the user. In such an embodiment, activation of switch  54  sends a signal to the timer circuit, which, after the execution of a delay (e.g. 2 seconds) sufficient for preheating the water inside of tube  28 , sends a signal to open valve  32 . This embodiment conveniently allows the user to press or activate a single switch when near boiling point water is desired, and indeed might obviate the need for a user-activated valve  32 . Such timer circuits, and methods of powering and connecting the same are well known and thus are not illustrated in further detail herein.  
     [0032] To demonstrate the correct size or power output for the secondary heating element  50 , a single secondary heating element  50 , Chromalox™ SGB-1153L, rated at 1300 watts was tested. The results of such testing are shown in FIGS.  4 - 6 . In FIG. 4, the test was performed with the secondary heating element adjusted for a 750 watt output by varying the applied voltage appropriately. In FIG. 5, the test was performed with the secondary heating element adjusted for a 1000 watt output. In FIG. 6, the test was performed with the secondary heating element adjusted for a 1300 watt output, i.e., with full voltage provided to the secondary heating element  50 . In each test, the water flow rate from the hot water dispenser was approximately 0.5 gallons per minute.  
     [0033] Referring to FIG. 4, at the beginning of the test, water  16  in the tank  12  (designated as  100 ) was about 195° F. Initially, the tank water temperature remains steady at about 196° F. for the first half of the test then begins to fall to about 191° F. As the test begins the water output temperature (designated as  102 ) is 210° F. The output water temperature is initially somewhat high due to preheating of tube  28  by secondary heating element  50  before water begins to flow through tube  28 . Once water  16  begins to flow through tube  28 , tube  28  is cooled by the flowing water at a rate faster than secondary heating element  50  can replace the lost heat. As a result the water output temperature  102  begins to decrease and continues to decrease until water flow through tube  28  is terminated at the end of the test. This test indicates that for this embodiment, a 750 watt secondary heater is not strong enough to provide near boiling point water for a time sufficient for most user applications, such as steeping a mug of tea, although it might be acceptable for other applications.  
     [0034]FIG. 5 shows the test results when the secondary heating element is set at 1000 watts. At the beginning of the test, water  16  in tank  12  (designated as  110 ) is about 187° F. As the test begins the water output temperature (designated as  112 ) quickly increases to over 205° F. and remains there. Even as the temperature of the water in the tank  110  decreases, the secondary heating element  50  is able to maintain water output temperature above 205° F., but is not able to increase past about 210° F. FIG. 5 thus indicates proper balance between rapidly providing near boiling point water while not generating steam at the indicated water flow rate. (Steam could be generated if the water flow rate was reduced).  
     [0035]FIG. 6 shows the test results when the secondary heating element is set at 1300 watts. At the beginning of the test, water  16  in the tank  12  (designated as  120 ) is about 192° F. As the test begins, the water output temperature (designated as  122 ) rises quickly to over 205° F. However, even when the preheated water temperature in the tank  120  decreases there is no corresponding decrease in the water output temperature  122 . In fact the water output temperature rises even though the water temperature in the tank decreases, meaning that the secondary heater has enough heating capacity to add additional energy to the water in order to reach near boiling temperatures even when the water input temperature is declining. This may suggest that 1300 watts in this embodiment is too powerful for some applications, and that steam generation may result (although this may be desirable for other applications requiring steam, such as making cappuccino).  
     [0036] The tests depicted in FIGS.  4 - 6  illustrate that some amount of experimentation might be necessary on a given application to achieve the proper power level for the secondary heating element  50 . As one skilled in the art will realize, the power level is a function of several characteristics, each of which must be considered, including the water flow rate, efficiency of heat transfer to the water, etc.  
     [0037] While the embodiment of the present invention is described as being mounted about a sink there are many possible variations of using the present invention. It could be used in vending machines that dispense hot soup, tea, or coffee. It could also be used in coffee makers. The present invention could be used anywhere that hot or near boiling water is required. While the present invention has been described with particular embodiments, one should not understand these embodiments to limit the scope of the various aspects of the invention, which instead is defined by the below claim language and its equivalents.