Abstract:
A warewash machine includes a housing at least in part defining a wash area. A water tank supplies water to the wash area and a water heating system is provided for heating water in the water tank. The water heating system includes a heat exchange tube immersed in water within the water tank and has an outer surface in a heat exchange relationship with the water. An infrared gas burner is at least partially disposed within the heat exchange tube for combusting an air/gas mixture and delivering combustion gases through the heat exchange tube. A turbulator is positioned within the heat exchange tube downstream of the infrared gas burner for introducing turbulence in the combustion gases traveling through the heat exchange tube.

Description:
TECHNICAL FIELD  
       [0001]     The present application relates to warewasher water heating systems and more particularly to a warewasher water heating system including an immersion tube with a turbulator disposed therein.  
       BACKGROUND  
       [0002]     Commercial warewashers vary significantly in their design and manner of use, but many include a water heating tank. Water may be recirculated from the tank through wash arms under pressure via a pump. In many cases, it is desirable that the temperature of the water be maintained at an approximate temperature of, e.g., about 150° F. in a high-temperature machine (one using a fresh final rinse at 180-195° F.) or, e.g., at about 140° F. in a low-temperature machine (one utilizing a final rinse mixture of fresh water and sodium hypochlorite for sanitizing, also at about 140° F.). Due to the high volume seen by many commercial warewashers, any increase in efficiency can result in substantial savings in operation costs over time.  
       SUMMARY  
       [0003]     In an aspect, a warewash machine includes a housing at least in part defining a wash area. A water tank supplies water to the wash area and a water heating system is provided for heating water in the water tank. The water heating system includes a heat exchange tube immersed in water within the water tank and has an outer surface in a heat exchange relationship with the water. An infrared gas burner is at least partially disposed within the heat exchange tube for combusting an air/gas mixture and delivering combustion gases through the heat exchange tube. A turbulator is positioned within the heat exchange tube downstream of the infrared gas burner for introducing turbulence in the combustion gases traveling through the heat exchange tube.  
         [0004]     In another aspect, a method of increasing the efficiency of a water heating system for a warewash machine is provided. The method includes providing a first heating system configuration. The first heating system configuration includes a housing at least in part defining a wash area, a water tank for supplying water to the wash area, a water heating system for heating water in the water tank, the water heating system including a heat exchange tube within the water tank, and an infrared gas burner at least partially disposed within the heat exchange tube for combusting an air/gas mixture and delivering combustion gases through the heat exchange tube. The first heating system configuration has an efficiency during a water heating operation. The efficiency is increased by positioning a turbulator within the heat exchange tube downstream of the infrared gas burner for introducing turbulence in the combustion gases traveling through the heat exchange tube.  
         [0005]     The details of one or more embodiments are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will be apparent from the description and drawings, and from the claims. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0006]      FIG. 1  top, partial section view of an embodiment of a water heating system with a heat exchange tube shown in section;  
         [0007]      FIG. 2  is a perspective view of an embodiment of a turbulator;  
         [0008]      FIG. 2A  illustrates an angle between planar portions of the turbulator of  FIG. 2 ;  
         [0009]      FIG. 3  is a side, partial section view of an embodiment of a warewash machine including the water heating system of  FIG. 1 ;  
         [0010]      FIGS. 4 and 5  are top and perspective views of a base of the warewash machine of  FIG. 3  with an outer cover removed;  
         [0011]      FIG. 6  is a perspective view of an embodiment of a base of a warewash machine including a baffle box; and  
         [0012]      FIG. 7  is a perspective view of the base of  FIG. 6  with a sidewall of the baffle box removed. 
     
    
     DETAILED DESCRIPTION  
       [0013]     Referring to  FIG. 1 , a water heating system  10  includes a heat exchange tube  14  and a heater  17  including a burner  22  disposed within the heat exchange tube. The heater  17  includes control connections  15  for connecting the heater to a control unit (not shown) for controlling operation of the heater and associated burner  22  during a heating operation. In the illustrated embodiment, the heat exchange tube  14  is L-shaped including a first heat exchange portion  16 , a gas inlet  24 , a second heat exchange portion  18  and a gas outlet  26 . A restricting portion  20  connects the first and second heat exchange portions  16 ,  18 . The restricting portion  20  has an inner dimension to define a flow area that is less than that of the first and second heating portions  16  and  18 , e.g., to induce or create back pressure for use during operation. It should be understood, however, that back pressure can be introduced anywhere in the water heating system  10  between the burner  22  and the gas outlet  26 . Moreover, gas outlet  26  will typically connect with an exhaust stack and back pressure could also be induced at a location along the exhaust stack or path. As will be described in greater detail below, a turbulator  30  is located within the heat exchange tube  14  downstream of the burner  22 . The turbulator  30  introduces turbulence in the heated gases traveling through the heat exchange tube.  
         [0014]     A suitable heater  17  is an infrared (IR) heater including a gas-fired IR burner  22 . Typically, such IR burners have a hollow central permeable tube about which a sleeve  32  of woven ceramic fabric is provided. When an air/gas mixture is introduced under pressure using blower  34  into the hollow tube, it flows outwardly through interstices of the woven fabric and, upon ignition of the mixture, forms the entire outer surface of the fabric to serve as an IR combustion surface  28 . When the pressure of the air/gas mixture and the back pressure built into the design are properly tuned, the flame will have a burning zone that is maintained at or near the combustion surface  28 . Further discussion of operation of IR heaters in warewash machines can be found in U.S. Pat. No. 5,794,634, the details of which are hereby incorporated by reference as if fully set forth herein.  
         [0015]     Referring still to  FIG. 1 , disposed within the second tube portion  18  is turbulator  30 , which is represented by dashed lines to emphasize that turbulator  30  can be of any form suitable to introduce turbulence to the combustion gases flowing in the heat exchange tube  14 . Turbulence is introduced to the combustion gas flow to force relatively hot combustion gases flowing near centerline L toward inner surface  44  of the heat exchange tube  14  (see arrows  19  of  FIG. 1 ) and to mix the combustion gases within chamber  42 , e.g., to provide a more uniform heating temperature during a heating operation. Turbulator  30  extends from an end  36  of the restricting portion  20  to outlet  26 , which is formed by a flanged member  38  including flange  40 . The flanged member  38  can be used to connect the heat exchange tube  14  to, for example, a flue or exhaust of a warewash machine. In an alternative embodiment, turbulator  30  may not extend to outlet  26  and may include, for example, a free end disposed within chamber  42 .  
         [0016]     In the illustrated embodiment, turbulator  30  has a maximum width W that is less than an inner dimension D of the second portion  18 , e.g., to aid in assembly. In other embodiments, W may be about the same as D. Suitable materials for forming turbulator  30  include materials having a melting point high enough to withstand gas combustion temperatures, such as stainless steel, aluminum, copper, etc. Materials used to form the turbulator  30  may or may not have good thermal conductivity.  
         [0017]     Referring to  FIG. 2 , an example of a turbulator  30  includes a first, relatively planar portion  46  and a second, relatively planar portion  48 . First planar portion  46  and second planar portion  48  each form respective imaginary planes P 1  and P 2  that are disposed at an angle θ (in some embodiments, between about zero and 180 degrees, such as about 45 degrees or greater, such as about 90 degrees) relative to each other ( FIG. 2A ). An angled or twisted portion  50  of varying angular relationship with respect to P 1  and P 2  connects the first and second planar portions  46  and  48 . Connected at end  52  of the turbulator  30  is a stop tab  54 . While in the illustrated embodiment each portion  46 ,  48  and  50  has somewhat smooth front and back faces,  62  and  64 , the front and back faces can be ribbed, grooved, etc.  
         [0018]     In one embodiment, the turbulator  30  is wedged into the second portion  18  through outlet  26 , with the stop tab  54  sized to prevent the turbulator  30  from entering the first portion  16  of the heat exchange tube  14  and contacting burner  22 . Stop tab  54  can also provide support for fixing turbulator  30  within the chamber  42  and maintaining spacing of the relatively planar portions  46 ,  48  from inner surface  46  of the heat exchange tube  14 . Apertures  56  and  58  are located near ends  52  and  60  to aid in manufacture of the turbulator  30  by allowing for insertion of twisting members, such as rods, of a twisting device (not shown) to, for example, cold form a preform plate into the desired shape by twisting. The turbulator  30  can provide increased system efficiency at relatively low cost.  
         [0019]      FIG. 3  is a side view of a warewash machine  70  including a housing  72  atop a base  74 , a moveable door  78  and a washing chamber  76  enclosed by the moveable door  78 , while  FIGS. 4 and 5  show the water heating system  10  connected to a water tank  80  having a top opening that allows for communication with the washing chamber. Referring briefly to  FIG. 3 , this particular warewash machine embodiment is shown for illustrative purposes, it being understood that the heating system  10  can be useful with other warewash machine embodiments, such as conveyor-type warewash machines, or other types of warewash machines, for example, where detergent-laden wash water or rinse water is recirculated by a pump through one or more wash/rinse arms or other structures that spray liquid onto wares to be cleaned.  
         [0020]     In the illustrated embodiment, moveable door  78  encloses washing chamber  76  into which racks of wares are placed between an upper wash arm  82  and a lower wash arm  84 , each of which arms are supplied with spray nozzles. Water is fed to the wash arms  82 ,  84  by a pump  86  which can include a screened water intake  88  and is passed through a conduit  90  to the arms. The water intake  88  is adjacent to and draws water through an opening  92  ( FIG. 5 ) to water tank  80 . Water fed to the wash arms  82 ,  84  is directed onto wares placed in the washing chamber  76  and the water drains back into the water tank  80  from the wares, enabling recirculation of water through the tank  80  as desired.  
         [0021]     Referring now to  FIGS. 4 and 5 , water can be maintained at a predetermined fill level (e.g., as shown by dashed line  91 ) within the water tank  80  during a washing operation. When preliminarily filled, the water tank  80  may be filled from either a separate water supply or through a conventionally-supplied water line. The level of water within the water tank  80  can be monitored, for example, using a float switch or electronic sensor (not shown), which can be operated to open and close a fill valve when the water reaches a desired level. A drain  94  is provided at the bottom of the water tank  80  and may be separate from or associated with a standpipe (not shown).  
         [0022]     The water level may be maintained within the water tank  80  such that the heat exchange tube  14  is completely submerged within the water. Referring particularly to  FIG. 4 , the heat exchange tube  14  extends generally horizontally within the water tank  80  with the first portion  16  connected to a front wall  96  of the water tank  80  and the second portion  18  connected to a rear wall  98  of the water tank. A gas supply conduit  100  ( FIGS. 1 and 5 ) extends from the blower  34  to the burner  22  for delivering the air/gas mixture to the burner.  
         [0023]     In some cases, adding turbulator  30  to the heat exchange tube  14  of a warewasher can improve heating efficiency of the warewasher by about 2 percent (e.g., compared to the same warewasher without the turbulator  30 ). For example, efficiency of a heating system was measured to be about 80% without turbulator  30  and, after adding turbulator  30  by securing the turbulator within the heat exchange tube  14 , the efficiency of the heating system was measured to be about 82%. Efficiency of the heating system was determined by measuring the amount of heat units (BTU) and time necessary to increase the temperature of 110.6 pounds of water by 80° F. in a pilot tank including baffle box  110  as shown in  FIGS. 6 and 7  using an IR heater having a BTU value UL listed at 25,000 and a heat exchange tube with a surface area of 286.9 sq inches. The following equation was used to calculate the efficiency and the results are summarized in Table I that follows.  
                                           TABLE I                                           Efficiency   =         (     Temperature   ⁢           ⁢   Increase     )     ⁢     (     Weight   ⁢           ⁢   of   ⁢           ⁢   Water     )           (     Heat   ⁢           ⁢   Units     )     ⁢     (   Time   )                                      Warewasher   Warewasher With           Without Turbulator   Turbulator                        Efficiency   80   82       (percent)       Weight of Water   110.6   110.6       (pounds)       Temperature   80   80       Increase (° F.)       Heat Units   24851   25284       (BTU)       Time (s)   1625   1540                  
 
         [0024]     It is to be clearly understood that the above description is intended by way of illustration and example only and is not intended to be taken by way of limitation, and that changes and modifications are possible. For example, while an L-shaped heat exchange tube  14  is primarily described, any other suitable shape can be employed, such as a U-shaped heat-exchange tube. Moreover, additional heat transfer to the water might be achieved by including a baffle box along a bottom wall of the water tank to receive the combustion gases from the heat exchange tube and/or including a baffle box along a sidewall of the water tank. As an example,  FIGS. 6 and 7  show base  74  including a baffle box  110  located along a sidewall of the water tank. Referring to  FIG. 7 , within the baffle box  110  baffle plates  112  direct combustion gases exiting outlet  26  along a tortuous path for additional heating of the water through the sidewall of the water tank. The baffle box  110  includes an outlet  120  for connection to an exhaust stack. In some embodiments, the turbulator could also be configured to provide flow restriction, which may induce back pressure in the heat exchange tube for more effective operation. Accordingly, other embodiments are contemplated.