Abstract:
A shower or car-wash is provided with a heat-exchanger element of thin sheet metal mounted under or in the floor to pre-heat incoming cold water using heat recovered from the spent sprayed water. The heat exchanger element has a rectangle wave shaped cross section thereby providing greater heat transfer area and being able to withstand heavy vertical loads. The vertical portions of the rectangle wave may advantageously be provided with vertical reinforcing ribs in the form of depressions stamped in the metal.

Description:
[0001]     The present invention relates to a spray or shower arrangement as recited in the preamble to the attached claim  1  and to a shower insert as recited in the preamble to the attached claim  13 .  
       BACKGROUND OF THE INVENTION  
       [0002]     The present invention relates to the recovery of heat from spent water in showers and other spray arrangements. Significant savings can be made in water heating costs if the heat content from the sprayed water, before it disappears into the drainage system, can be partially transferred to incoming cold water thereby pre-heating it before it is mixed with the incoming hot water, thereby reducing the amount of hot water required to achieve the desired warm water temperature from the shower or spray head.  
       BACKGROUND ART  
       [0003]     It is known in the art to use a heat exchanger element to pre-heat incoming cold water by extracting heat from the spent water in a shower, for example through DE 44 06 971 A1, EP 0 275 237A2, DE 33 19 638 A1, DE 37 17 720 A1 and DE 196 08 404 A1, each of which describes a shower system, wherein a heat exchanger is mounted beneath the shower basin. In each of these systems, the spent shower water flows on one side of a heat exchanger before flowing out into the drainage system. Incoming cold water flows in a convoluted flow path on the other side of the heat exchanger element and is thereby preheated before being mixed in the mixer with the hot water. The channels in each of these background documents are in general of rounded cross section. DE 37 17 720 A1 describes however channels for the incoming cold water which are diamond-shaped in cross section, i.e. squares tipped up 45°. The spent shower water runs down through the shower floor over these diamond cross section tubes. This heat exchanger arrangement is difficult to construct since it requires individual diamond cross section tubes connected together by end conduits. EP 0 275 237 describes lens shaped conduits under the shower floor. These conduits provide more heat transferring surface area than a tube of circular cross section but are also difficult to arrange and connect as individual conduits.  
         [0004]     Against the background of this art, the problem addressed by the present invention is to provide a heat exchanging arrangement and/or insert, which is easily and inexpensively manufactured, has a heat exchanger sheet which is thin and provides a greater heat exchanging surface than conventional designs at the same time as it is capable of withstanding downwardly directed loads.  
         [0005]     These and other advantages are achieved according to the invention by an arrangement of the type described in the preamble to claim  1 , which has the features recited in the characterizing clause of claim  1  and by an insert of the type described in the preamble to claim  12 , which has the features recited in the characterizing clause to claim  12 .  
         [0006]     The rectangle wave form of the metal heat transmitting sheet is compact and at the same time provides extensive surface area for heat transfer. Despite being thin, and thus rapidly and easily transferring heat, it is able to withstand the downward forces which may be applied when it is used in a shower basin or carwash for example. This is particularly true when the metal sheet I provided with vertical reinforcing ribs as recited in claim  2 . 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0007]     The present invention will now be described in more detail with reference made to the accompanying drawings, of which:  
         [0008]     FIGS.  1  ( a ), ( b ) and ( c ) show a plan view and two perspective views respectively of a shower floor basin,  
         [0009]     FIGS.  2  ( a - g ) show different views of a heat exchanger unit mounted under the shower floor basin,  
         [0010]      FIG. 3  shows various views of a drain with trap for use in the arrangement,  
         [0011]      FIG. 4  shows a schematic perspective view of a part of a metal heat exchanger element provided with vertical ribs. 
     
    
     DETAILED DESCRIPTION  
       [0012]      FIG. 1   a  shows a view from above of a shower floor basin  1  with a drain trap  2  and an inlet  4  and an outlet  3  for incoming cold water. The basin  1  has a gutter  5  in which sprayed water is collected and runs to the drain  2 .  
         [0013]      FIG. 2  shows a number of different views of a heat exchanger unit having a bottom  10  and a top  7 .  FIG. 2   a  is a view from above and  FIG. 2   b  is an end view showing the drain water outlet  9  and the heat exchanger inlet channel  4   a  and heat exchanger outlet channel  3   a  for incoming cold water which is to be pre-heated in the heat exchanger unit. There is a drain heat exchanger inlet  8  receiving spent shower water from  FIG. 2  ( e ) shows a perspective view of the heat exchanger unit with the cover  7  on and  FIG. 2  ( e ) shows the same unit with the cover  7  off, revealing the heat exchanger element in the form of a metal sheet  15 , which is formed with a rectangle wave cross section as can be seen in  FIG. 2 ( c ) which is a cross section on a much larger scale of a portion of the heat exchanger unit.  
         [0014]     The rectangle-wave metal sheet  15  as seen in  FIG. 2 ( c ) has a very thin thickness and is therefore able to transmit heat energy rapidly and efficiently. The wave has relatively long vertical portions  13  and relatively short horizontal portions  14  of dimension a. Before arriving at the shower mixer cold incoming water is led through the inlet  4  into the inlet channel  4   a  to the far end proximate the drain heat exchanger inlet  8  and flows through the channels on the underside of the sheet metal element  15 , absorbing the heat of the spent shower water on the other side of the element, before exiting through channel  3   a  and outlet  3 , from where it flows pre-heated to a conventional shower mixer where some additional hot water is mixed in to bring the water exiting the shower head to the desired comfortable temperature.  
         [0015]      FIG. 2 ( f ) shows a push-button cut-off valve  16 , which is manually actuated at periodic intervals when the heat exchanger drain path is to be disinfected, by filing it with disinfectant through the drain  2 , and allowing the disinfectant to stand for a period in the heat exchanger, before the push-button is actuated again to open the drain path and allow the disinfectant solution to be flushed out. The push-button cut-off valve  16  is shown enlarged in  FIG. 2 ( g ).  
         [0016]     By virtue of the fact that the heat exchanger element is made of such thin sheet metal, after the shower is turned off and the spent water runs out of the heat exchanger and into the sewage system, the sheet metal will cool very rapidly since there will be cold water on one side of the metal sheet and air on the other side. This reduction in temperature will inhibit the growth of bacteria. Optionally, after the shower is shut off, a valve opening into the basin near the drain may open and allow cold water to run for a few seconds thereby effectively cooling off the system. This valve may also be set to open periodically to flush the system with new cold water if the shower is not used for longer periods of time.  
         [0017]     To kill bacteria it is also possible to apply a voltage, which will not be noticed by or affect the shower occupant, between the cold water inlet and outlet.  
         [0018]      FIG. 3 ( a ) is a perspective view in more detail of the trap drain  2  shown in  FIGS. 1 and 2 . The trap outlet  18  is at a higher level than the base of the drain to for a water trap so that sewage smells cannot wander back up and out into the bathroom. The trap drain  2  has a first filter  19  which can be removed for cleaning or replacement by means of the tab  21 . A second filter  20  is disposed below the first filter  19 . If the second filter  20  is removed, the spring  22  will move the plug  21  upwards to close off the drain. This will protect the heat exchanger from being used without a filter protecting the heat exchanger from becoming clogged with soap and shampoo residue, hair and skin remnants and other contaminants which might otherwise cause a sanitary problem.  
         [0019]      FIG. 4  shows a schematic perspective representation of a further advantageous embodiment of the rectangle wave shaped heat exchanger element. Only one wave length is shown. The vertical portions  13  are each embossed with ribs  6   a ,  6   b  while the metal sheet is still flat before the metal sheet is bent into it final shape. The vertical ribs are in the form of depressions which are all directed to the right in figure. The rows of ribs are all arranged in direct alignment with each other so as to create a meandering zig-zag path for water on either side of the sheet. This increases the heat transfer surface significantly and at the same time strengthens the heat exchanger element for vertical downward loading. The heat exchanger element can still be made of thin sheet metal.  
         [0020]     The person skilled in the art will of course recognize that the invention defined in the attached claims can also be realized in a number of different applications where the recover of heat from spent water is desired, such as many types of hot shower arrangements including car-washes.  
         [0021]     The present invention can also be implemented in the form of a prefabricated insert which can be installed in existing showers or car-washes for example, connecting to the existing cold water and drain lines.