Abstract:
Disclosed herein are storage type water heaters having means for improved mixing of cold water supply with water stored in the water tank of a water heater, means for limiting surges of water into and out of a water tank, and means for disrupting formation and propagation of convection currents and water streamers in a water tank.

Description:
This application claims the benefit of Provisional application Ser. No. 60/251,190 filed Dec. 4, 2000. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to storage type water heaters. Particularly, the present invention relates to improved apparatus and methods for distributing water in the water storage tank of a water heater for improving thermal efficiency. More particularly, the present invention relates to improved methods and apparatus for mixing incoming cold water with heated water in the water storage tank for eliminating stratification of water according to temperature and for preventing intrusion of cold water streamers into the heated water in the upper portion of the water storage tank. 
     2. Description of Pertinent Art 
     Storage type water heaters, as contemplated herein, typically comprise a vertical, cylindrical water rank having a cold water supply tube, (commonly referred to as a “dip tube”), extending internally from the top of the water tank to a point near the bottom of the water rank, and having a hot water outlet near the top of the water tank, Such water heaters may employ gas heat or electrical heat for heating water. Typically, such water heaters are employed to heat cold water from a temperature of often 58° F. or lower to temperatures in the range of about 120° to 140° F. The heated water is stored in the water tank for use as the demand arises. 
     Such water heaters as are heated by gas generally comprise a vertical, cylindrical water tank having a centrally located gas flue passing vertically through the water tank. A radial flame gas burner, located directly below the bottom of the water tank heats water in the water tank. Additional heat is transferred to water in the water tank from hot combustion gasses produced by the burner passing upward through the gas flue. Flue baffles and similar apparatus are commonly employed in the gas flue for improving heat transfer from the combustion gasses to the water in the tank. Combustion gases are exhausted from the gas flue near the top of the water heater. 
     Such water heaters as are heated by electricity generally comprise a vertical cylindrical water tank having one or more electrical resistance heating elements mounted at intermediate elevations in the water tank. Heat is exchanged between the heating elements and water in the water tank. 
     Cold water is supplied to a storage type water heater through a dip tube. As hot water is withdrawn from an outlet near the top of the tank, cold water flows down the dip tube and is deposited near the bottom of the tank. Water in the tank is heated, by either electric elements or gas burners, creating a water temperature gradient with the hottest water near the top of the tank and the coolest water at the bottom. The velocity and uneven distribution of water discharging from the dip tube often result in streamers of cold water flowing upwardly in the tank, disturbing the water temperature gradient and sometimes allowing cold water to discharge from the hot water outlet. 
     Methods and apparatus for improving distribution of cold water and preventing convection currents of cold water in the tank of a water heater are known in the art. In U.S. Pat. Nos. 4,949,680; 5,054,437; 5,137,053; and 6,199,515 B1, means including baffles and diffusers are provided for distributing cold water from the dip tube evenly across the bottom diameter of the tank and thereby preventing streamers of unheated water from rising within the tank. 
     In U.S. Pat. No. 4,949,680 the vertical dip tube, through which cold water enters the tank, is positioned at or near the central axis of the tank for exchanging heat between heated water in the tank and cold water entering through the dip tube, thus foiling thermal convection currents from rising in the tank and minimizing the mixing of hot and cold water near the hot water discharge outlet. 
     U.S. Pat. Nos. 4,632,065 and 5,809,941 disclose internal baffles within the water hearer tank for foiling internal thermal convection currents within the tank and minimizing mixing of hot and cold water near the hot water discharge outlet from the tank. 
     U.S. Pat. No. 4,197,446 discloses a water heater comprising a storage rank, a cold water inlet means comprising an external water heater connected to the water tank, a jet pump in the cold water inlet and a hot water discharge faucet. In operation, when hot water is discharged through the hot water faucet, cold water enters the tank trough the jet pump, causing water to be drawn from the tank into die external heater where the water is heated to discharge temperature. A portion of the hot water from the external heater is drawn i-nto the jet pump where the hot water mixes with the entering cold water. This water mixture is discharged into the rank where it is maintained at an intermediate temperature without further heating in the tank. 
     British Provisional Specification GB 648,213 discloses a water heater comprising a tank, a first tube vertically arrayed in the tank and having an open top, an external heater in communication with the external lower portion the first tube, and a second tube having a first open end in communication with the lower portion of the tank and a second open end in communication with the interior of the first tube lower portion. In operation, the external heater heats water in the lower portion of the first tube. As heated water rises in the first tube, cooler water from the lower portion of the water tank is drawn in to the lower portion of the first tube through the open second tube. Heated water from the first tube is discharged near the top of the tank. 
     SUMMARY OF THE INVENTION 
     Now, according to the present invention, I have discovered apparatus and methods for improving thermal efficiency and uniformity of hot water discharge temperature in a storage type hot water heater. 
     A storage type water heater comprising: a water tank having a cold water inlet and a hot water outlet, and a dip tube having a dip tube inlet connected to the cold water inlet, and having a dip tube outlet discharging into the lower portion of the water tank, the improvement of the present invention comprises: 
     a). a first flow regulator in the cold water inlet for regulating the flow of cold water into the water tank; 
     b). one or more mixing means in the dip tube for mixing incoming cold water with warm water from the water tank; 
     c). distributor means for distributing water discharged from the dip tube outlet evenly into the lower portion of the water tank; and 
     d). a second flow regulator in the hot water outlet for regulating flow of hot water from the water heater. 
     The apparatus of the present invention further includes baffle means in the mid portion of the water tank for preventing the upward flow of cooler water to the hot water outlet. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 of the drawings is a schematic cross section of the water tank of an electrically heated water heater typical of prior art storage type water heaters. 
     FIG. 2 of the drawings is a schematic cross section of the water tank of an electrically heated storage type water heater, incorporating improvements of the present invention. 
     FIG. 3 of the drawings is a schematic cross section of the water tank of a gas flame heated storage type water heater, incorporating improvements of the present invention. 
     FIG. 4 of the drawings is a schematic cross section of a dip tube assembly incorporating the improvements of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The detailed description of the invention which follows is made with reference to the drawings and in terms of preferred embodiments of the invention. The detailed description is not intended to limit the scope of the present invention, and the only limitations intended are those embodied in the claims appended hereto. 
     In FIG. 1, a conventional water heater is shown and its operation is described below for presenting problems which the improvements of the present invention overcome. 
     In FIG. 1, a conventional electrically heated tank type water heater  30  is shown in schematic cross section. Water heater  30  comprises a water tank  10  having an electrical resistance heating element  11 , a cold water inlet  14  and a hot water outlet  17 . A cold water dip tube  12 , having an open upper end  13  connected to cold water inlet  14 , is disposed substantially vertically in water tank  10  and terminates at open end  15  near the bottom  16  of tank  10 . In operation, hot water is withdrawn from water tank  10  via hot water outlet  17 . Cold water, propelled by water main pressure, flows into water tank  10  through dip tube  12 , replacing the hot water withdrawn. Cold water, from dip tube open end  15 , enters the lower portion of water tank  10  near water tank bottom  16 . The velocity and uneven distribution of cold water flowing from dip tube open end  15  creates streamers of cooler water which are forced upward, creating volumes of water having different temperatures. The volumes of water having different temperatures form water strata, indicated at  18 ,  19 ,  20 ,  21  and  22 , in water tank  10 . Each water stratum, of  18 ,  19 ,  20 ,  21  and  22 , has a different temperature and density from other strata of the group. The temperatures of the strata increase in a vertical direction with stratum  18  having the lowest temperature and stratum  22  having the highest temperature. Water in stratum  22 , heated by heating element  11 , is substantially at the temperature of hot water which is withdrawn through hot water outlet  17 . 
     As the rate of hot water withdrawal from hot water outlet  17  is increased, the rate of cold water flowing from dip tube outlet  15  increases for maintaining the volume of water in water tank  10 . At high rates of flow, cold water from dip tube outlet  15  tends to force water from strata  18  and  19  upward into water stratum  22  and, in severe cases, into hot water outlet  17 . Thus reducing the temperature of hot water available for withdrawal from water tank  10 . 
     According to the present invention, apparatus and methods for improved distribution of cold water into a storage type water heater are disclosed. Use of the apparatus and methods of the present invention improves mixing of cold supply water with water in the water tank of the water heater, thereby minimizing temperature stratification of water in the water tank and reducing intrusion of cooler water from the water tank into the hot water outlet; thereby improving thermal efficiency of the water heating process and improving uniformity of the temperature of hot water produced. 
     In FIG. 2, a water heater  100 , embodying improvements of the present invention is shown. Water tank  110 , having an electrical resistance heating element  111 , is shown in schematic cross section. Cold water dip tube  112 , having an open upper end  113  connected to cold water inlet connection  114  near the top of water tank  110 , extends downward into water tank  110 , ending at dip tube open end  115  above water tank bottom  116 . Hot water outlet  117  is located near the top of water tank  110 . 
     In FIG. 2, according to the present invention, eductor mixers  123 ,  124  and  125  are connected into the lower portion of dip tube  112 , for blending water from water tank  110  with cold water in dip tube  112 . Eductor mixers are well known and widely used for pumping and mixing liquids. Eductor mixers utilize the kinetic energy of a first flowing liquid to cause a second liquid to flow into and mix with the first liquid. In operation, a high velocity stream of one liquid exiting a restricted flow area creates an region of low pressure into which a second liquid can flow, thus mixing the two liquids. 
     In FIG. 2, cold water flowing in dip tube  112  passes through eductor mixer  123  thus drawing in and mixing warm water from water tank  110  with cold water in dip tube  112 , thereby forming a first water mixture having a temperature higher than the cold water temperature. This first wager mixture continues flowing downward from eductor mixer  123 , through dip tube  112  and through eductor mixer  124 , thus drawing in and mixing additional warmer water from water tank  110  to form a second water mixture, warmer than the first water mixture. The second water mixture Continues flowing downward from eductor mixer  124 , through dip tube  112  and through eductor mixer  125  where the second water mixture draws in and mixes with further warm water from water tank  110 , thus forming a third water mixture which is warmer than the second water mixture. This third water mixture continues flowing down dip tube  112 , through dip tube outlet  115  and discharges into the lower portion of water tank  110 . By placing eductor mixers  123 ,  124  and  125  in the lower portion of water tank  110  below heating element  111 , water strata  119 ,  120  and  218 , each having a different temperature, are disrupted or prevented from forming, such that water in the lower portion of water tank  110  has a relatively uniform temperature as it passes upward for heating by the electrical heating element  111 . Thereby allowing hot water to be heated to a relatively uniform temperature and improving thermal efficiency of the water heating process. 
     In FIG. 2, the three eductor mixers  123 ,  124  and  125  are shown in the lower portion of water tank  110 . Preferably the eductor mixers are positioned in the lower third of water tank  110  where water strata, such as strata  118 ,  119  and  120  are likely to form when such eductor mixers are not employed. While three eductor mixers,  123 ,  124  and  125 , are shown, it is contemplated that the number of eductor mixers may be selected to achieve the desired mixture of incoming cold water with warm water from water tank  110 . The number of eductor mixers may be one or more. 
     In FIG. 2, a distributor  126  is located below dip tube outlet  115  for redirecting the flow of water from dip tube outlet  115  from a downward direction to a substantially horizontal direction and for distributing the redirected water into water contained in the lower portion of water tank  110 . Distributor  126 , by so distributing the water flowing from dip tube outlet  115 , improves mixing of water flowing from dip tube outlet  115  with water in the lower portion of tank  110 ; reduces formation of water strata having different temperatures; and reduces the up flow of cooler water into hotter water located in the upper portion of water tank  110 . Distributor  126  comprises means for changing the direction of water flow from a downward direction at dip tube outlet  115  to a substantially horizontal direction. In FIG. 2, distributor  126  is shown connected to dip tube outlet  115 . However, distributor  126  may be mounted in other ways, such as connected to a wall or bottom  116  of water tank  110 . 
     In FIG. 2, dip tube  112  is connected to cold water inlet  114  and extends downward into water tank  110 . Eductor mixers  123 ,  124 , and  125  and distributor  126  are shown connected to dip tube  112 . Preferably, dip tube  112 , eductor mixers  123 ,  124  and  125  and distributor  126  are of a dimension such that they will pass through cold water inlet  114 . In this preferred configuration, dip tube  112 , eductor mixers  123 ,  124  and  125  and distributor  126  may be freely passed through cold water inlet  114  for insertion into and withdrawal from water tank  110  as necessary or as desired. 
     In FIG. 2, baffle  127  extends horizontally across water tank  110  at an elevation above eductor mixer  123  for preventing the up flow of streams of cooler water into the upper portion of water tank  110  near hot water out let  117  without substantially hindering the general upward flow of water from the lower portion into the upper portion of water tank  110 . Preferably, baffle  127  is located at about the mid point of water tank  110 . Openings  130  in baffle  127  are arranged such that streams of rising cooler water will be disrupted while the upward movement of water from the lower portion into the upper portion of water tank  110  is not substantially hindered. Baffles are well known and widely used. Baffle  127  may have a variety of configuration for accomplishing its purpose in the present invention. For example, baffle  127  may comprise a horizontal plate having holes or openings  130 , wherein the horizontal plate disrupts the upward flow of relatively fast moving streams of cooler water and the openings  130  allow the generally upward flow of water from the lower to the upper portion of water tank  110 . 
     In FIG. 2, first flow regulator  128  is connected to cold water inlet  114  and to dip tube open upper end  113 . Flow regulator  128  regulates the rate of flow of cold water into water tank  110 . Flow regulator  128  limits the rate of flow of cold water and limits a surge of cold water into water tank  110  when a sudden pressure change in the water system associated with the water heater  100  occurs. Such pressure changes in the water system often occur when a valve in the water system is suddenly opened or closed. By limiting a sudden surge of cold water into water tank  110 , an upsurge of cooler water from the lower portion into the upper portion of water tank  110  is prevented. 
     In FIG. 2, a second flow regulator  129  is connected to hot water outlet  117  for regulating the rate of flow of hot water out of water tank  110  for limiting a surge of hot water when a sudden pressure change in the water system associated with water heater  100  occurs. By limiting a surge of hot water from water tank  110 , the opportunity for injury or discomfort to a user of the hot water is decreased. 
     A wide variety of apparatus are available for use as flow regulators  128  and  129 . For example, orifice plates, check valves, and spring activated flow regulator valves are well known and widely used for such purposes. The choice of apparatus will depend upon such factors as anticipated pressure changes and water flow rates which the flow regulators may be expected to experience. One preferred apparatus is a spring activated flow regulator valve which is normally closed and opens in response to an increase in pressure differential across the valve. The spring limits the rate and degree of opening of the regulator valve in response to a pressure differential across the regulator valve, thus limiting any surge of water through the regulator valve. Such flow regulator valves are widely commercially available in a wide variety of styles, sizes, flow capacities and pressure differentials. 
     The description of the invention given above and with reference to FIG. 2 of the drawings is given in terms of an electrically heated water heater. A gas heated water heater has different thermodynamic characteristics from an electrically heated water heater. These differences in thermodynamic characteristics result in different heat distributions within the water contained in a water tank. Consequently, a different arrangement of the dip tube-eductor mixer combination is desirable for gas heated water heaters , as compared to electrically heated water heaters. Other elements of the present invention, including distributor  126 , baffle  127  and flow regulators  128  and  129  have the same functions in both electrically heated and gas heated water heaters. Therefore, in the description of the present invention which follows, as it applies to gas heated water heaters, only the dip tube-eductor mixer combination is described with the understanding that distributor  126 , baffle  127  and flow regulators  128  and  129  may be used in the same way in both electrically heated and in gas heated water heaters. 
     FIG. 3 is a schematic cross section of a water tank  210  of a gas heated water heater  200 . In FIG. 3, gas flue  250  extends upward through the center of water tank  210  for exhausting combustion gas from a gas burner, not shown, which heats water in water tank  210 . Hot combustion gasses in gas flue  250  often heat water near the top of water tank  210  to temperatures in excess of the maximum desired hot water temperature. Such overheating of water results in a waste of thermal energy. 
     In FIG. 3, dip tube  212 , having an open upper end  213  connected to cold water inlet connection  214  near the top of water tank  210 . extends downward into water tank  210 , ending at dip tube open end  215 , above water tank bottom  216 . Hot water outlet connection  217  is located near the top of water tank  210 . Cold water flows from dip tube  212  and enters water tank  210  through dip tube open end  215 . Eductor mixer  251  is connected in dip tube  212  at an elevation near the top of water tank  210  and eductor mixers  223  and  224  are connected in dip tube  212  at elevations in the lower portion of water tank  210  for blending water from tank  210  wit cold water flowing through dip tube  212 . 
     In FIG. 3, eductor mixer  251  is positioned in the upper portion of dip tube  212  for drawing in and mixing hot water from near the top of water tank  210  with cold water in dip tube  212  thereby forming a first water mixture having a temperature intermediate between the cold water temperature and the hot water temperature, thereby substantially redistributing wasted thermal energy from overheated water into water in the lower portion of water tank  210   
     In FIG. 3, the first water mixture flows downward from eductor mixer  251  through dip tube  212  and through eductor mixer  223 , thus drawing in and mixing warm water from the lower portion of water tank  210  for forming a second water mixture having a temperature higher than the temperature of the first water mixture. This second water mixture flows downward from eductor mixer  223 , through dip tube  212  and through eductor mixer  224  where the second water mixture draws in and mixes with additional water from water tank  210 , forming a third water mixture which is generally warmer than the second water mixture. The third water mixture flows downward from eductor mixer  224  through dip tube  212  to dip tube lower end  215  from which the third water mixture is discharged into water tank  210 . Eductor mixers  223  and  224 , by drawing in water from the lower portion of water tank  210 , disrupt and prevent formation of water strata of different temperatures in the lower portion of water tank  210 . 
     In FIG. 4, a dip tube assembly  400  is shown in section view. dip Tube assembly  400  comprises tubular dip tube members  412   a ,  412   b  and  412   c , eductor mixers  423   a  and  423   b , distributor  426  and flow regulator  428 . Dip tube assembly  400  is designed for insertion into a water tank through a cold water inlet. 
     In FIG. 4, flow regulator housing  401  is connected to the open upper end  402  of firs: dip tube member  412   a  and threads  403  provide for releasable connection of. flow regulator housing  401  to a cold water inlet of a water tank. Dip tube members  412   a ,  412   b  and  412   c , eductor mixers  423   a  and  423   b  and distributor  426  will pass freely through the cold water inlet and into the water tank. 
     In FIG. 4, Flow regulator  428  is double acting for limiting the flow of water surges in either direction through flow regulator  428 . Flow regulator  428  comprises regulator valve body  451  contained within the interior of flow regulator housing  428 . Openings  452  and  456  provide communication through regulator valve body  451 . Regulator valve plunger  450  is moveably mounted within regulator valve body  451 . Spring  453  communicates between the upper surface of regulator valve plunger  450  and regulator valve body  451 , and spring  454  communicates between the lower surface of regulator valve plunger  450  and regulator valve body  451  for maintaining regulator valve plunger in contact with regulator valve seat  455  under conditions of no differential pressure across flow regulator  428 . Upon application of a differential pressure across flow regulator  428 , springs  453  and  454  resist displacement of regulator valve plunger away from regulator valve seat  455 , thus limiting any surge at water passing in either direction through flow regulator  428 . 
     In FIG. 4, upper end  404  of first eductor mixer  423   a  is connected to lower open end  405  of first dip tube member  412   a . Lower end  406  of first eductor mixer  423   a  is connected to open upper end  407  of second dip tube member  412   b . Upper end  408  of second eductor mixer  423   b  is connected to lower open end  409  of second dip tube member  412   b  and lower end  410  of second eductor mixer  423   b  is connected to open upper end  411  of third dip tube member  412   c.    
     In FIG. 4, central opening  430   a  through first eductor mixer  423   a  smoothly reduces in diameter from central opening inlet  431   a  to central opening mid point  432   a  and smoothly decreases in diameter from central opening mid point  432   a  to central opening outlet  433   a . Openings  433   a  provide communication between the exterior of dip tube assembly  400  and central opening midpoint  432   a . Likewise, the diameter of central opening  430   b  smoothly decreases from central opening inlet  431   b  to central opening mid point  432   b  and smoothly increases in diameter from central opening mid point to central opening outlet  433   b , and openings  433   b  provide communication between the exterior of dip tube assembly  400  and central opening mid point  432   b  of second eductor mixer  423   b.    
     As water flows through the central opening of an eductor mixer as described above, the velocity of the flowing water increases as the diameter of the eductor mixer central opening decreases and the velocity of flowing water then decreases as the diameter of the central opening increases. In the dip tube assembly described, as the velocity of flowing water increases, the pressure of the flowing water decreases, thus producing a pressure differential between the exterior of the dip tube assembly and the interior of the eductor mixer central opening. Water, under influence of the pressure differential, flows through the openings between the exterior of the dip tube assembly into the eductor mixer central opening mid point. 
     In FIG. 4, distributor  426  comprises a distributor housing  440  connected to third dip tube member lower end  413  and a distributor plate  441 . Openings  442  through distributor housing  440  provide communication between the interior of third dip tube member  412   c  and the exterior of dip tube assembly  400 . Distributor plate  441  is connected to and spaced below distributor housing  441  for radially deflecting water flowing from distributor housing openings  442 . 
     Dip tube assembly  400 , described above, may be releasably connected into a water tank such that water flowing through the dip tube assembly  400  is mixed with water present in the water tank and water flowing from the dip tube assembly  400  is radially distributed into the water tank. 
     While the present invention has been described with reference to preferred embodiments, the same are to be considered illustrative only and not limiting in character. Many modifications to the methods and apparatus of the present invention will occur to those skilled in the art without departing from the spirit and scope of the invention, which is defined only by the claims appended hereto.