Method and apparatus for dampening noise occurring in liquid heaters operating according to the vacuum vaporization principle
FOREIGN PATENTS OR APPLICATIONS Apr. 15, 1975 122 4 R Kloner......  
 1,619,660 3/1967 Fieldmm... 1,966,442 7/1934 Field......... 2,261,235 11/1941 Doelling.... 2,378,934 6/1945 2,569,078 9/1951 Silver et al 822,244 11/1951 Germany Primary ExaminerAlbert W. Davis, Jr. Attorney, Agent, or FirmWerner W. Kleeman [57] ABSTRACT A method for dampening noise occurring in liquid heaters operating according to the vacuum vaporization principle owing to pronounced vapor formation at the heating surfaces which contemplate opposing the formation of vapor bubbles at the heating liquid through the action of obstruction or damming up means. The equipment for the performance of the aforesaid method employs obstruction or damming-up means arranged at the vacuum vessel or container which-oppose the formation of vapor bubbles at the heating liquid.  
 18 Claiins, 3 Drawing Figures DAMPENING NOISE OCCURRING IN LIQUID HEATERS OPERATING ACCORDING TO THE VACUUM VAPORIZATION PRINCIPLE Inventors: Willi Brandl, Zurich; Zdenek Koula,  
 Regensdorf; Peter Nirk, Zug, all of Switzerland Assignee: Stotz &amp; C0., Zurich, Switzerland Oct. 19, 1972 Appl. No.: 299,036  
 US. 165/1; 165/105; 122/367 PF; 122/501; 122/33 Field of Search 165/105, 1; 62/527; 122/367 PF, 501, 4 R, 33; 40/l06.2l  
 References Cited UNITED STATES PATENTS 6/1886 122/501 4/1890 122/501 8/1900 Ramsden 122/501 United States Patent Brandl et a1.  
 [ METHOD AND APPARATUS FOR [22] Filed:  
  a n 6 0 :0 0 u. H m an n. 4&#39; 0. 4 40:10.5  
  0 o -$20 20.0. a: 1 .rl ID OPI. 0 O  
 llllltllllll tllullilllisl III-l I I&#39;ll! IIIIIlII-II 1 METHOD AND APPARATUS FOR DAMPENING NOISE OCCURRING IN LIQUID HEATERS OPERATING ACCORDING TO THE VACUUM VAPORIZATION PRINCIPLE BACKGROUND OF THE INVENTION The present invention relates to a new and improved method of, and apparatus for, dampening the formation of noise occurring in liquid heaters which operate according to the vacuum vaporization principle owing to pronounced vapor formation at the heating surfaces.  
  Liquid heaters which operate according to the vacuum vaporization principle are known in the art, for instance from German Pat. No. 1,270,258. Such prior art construction embodies an evacuated vessel or container, the so-called vacuum vessel, partially filled with a vaporizable heating liquid, which can be heated by a heat source. One or a number of heat exchangers for heating one or a number of liquids are arranged at the vessel, these heat exchangers, in turn, being heated by the vapor of the vaporizable heating liquid.  
  These prior art constructions are used particularly as hot water heaters wherein, as a general rule, there are provided two heat exchangers, one of which serves for heating the water of a circulation heating installation, the other of which is designed as a boiler and serves for heating-up the water which is to be consumed. The heating liquid can be, for instance, also water.  
  Such type liquid heaters exhibit the unpleasant characteristics that during operation, especially however always after switching-in the heat source, there occurs a pronounced build-up of noise. This is predicated upon the intensive vapor formation at the heating surfaces of the vacuum vessel or container which is evacuated to about 18 Torr (mm. Hg pressure). Formation of vapor is particularly pronounced during the heating up period of such liquid heaters, because the heating liquid, typically water. owing to the negative pressure already begins to boil slightly above room temperature. Since in the vacuum vessel no atmospheric pressure opposes the formation of vapor bubbles there occurs, during the heating operation, in an almost explosion-like fashion very large vapor bubbles at the heating surfaces. The pronounced noise exists primarily because of the bouncing-off or recoil of the liquid at the heating surfaces after formation of the vapor bubbles. With progressive heating, that is to say, when the liquid in the vacuum vessel transforms progressively into vapor and therefore also the pressure increases, this development of noise considerably diminishes. It would be possible to dampen the formation of noise, especially during the heating-up period, by less strongly evacuating the vacuum vessel or container. However, this procedure would be disadvantageous from the standpoint that the heat transfer characteristics would become poorer if the vessel were evacuated to a lesser degree.  
 SUMMARY OF THE INVENTION Hence, it will be recognized that this particular field of technology is still in need of improved techniques and equipment for dampening the formation of noise in liquid heaters operating according to vacuum vaporization principles. It is a primary object of this invention to provide an improved method of, and apparatus for, dampening such noise formation.  
  Another and more specific object of the present in vention aims at dampening the formation of noise at liquid heaters of the aforementioned type without adversely affecting the efficiency of the equipment.  
  Yet a further significant object of the present invention relates to an improved method of, and apparatus for, beneficially. suppressing the formation of noise at heating equipment operating according to vacuum vaporization techniques, through the use of relatively simple and inexpensive means.  
 Now in order to implement these and still further obl0 jects of the invention, which will become more readily apparent as the description proceeds, the inventive method is manifested by the features that the formation of vapor bubbles at the vacuum vessel or container is opposed by obstruction or dam-up means.  
  As far as the apparatus aspects of this development are concerned and as same are used in the performance of the aforesaid method, the inventive apparatus is manifested by the features that such obstruction or dam-up means which oppose the formation of vapor bubbles are arranged in the vacuum vessel or container.  
  It has been found to be advantageous to employ as the obstruction or dam-up means, for instance granular material. This can be of coarse grain size. Better results can be realized, however, if there is employed as the obstruction or dam-up means a granular material having a grain size of less than 5 mm., advantageously in the range of 1.5 to 5 mm and preferably in the range of 1.5 to 2 mm.  
  Granular materials suitable for the purposes of the invention are for instance the following: sand. glass grains, metal spheres or balls and chips, ceramic balls or spheres, furthermore, balls or spheres formed of plastic, which are specifically heavier than the liquid and resistant thereto throughout the prevailing operating temperatures, for instance those formed of polytetrafluoroethylene. Particularly suitable is quartz sand of the aforementioned grain size. I  
  By virtue of the inventive obstruction or dam-up means proposed by this development, there is realized a surprising sound dampening effect which extensively exceeds all expectations as same can be readily demonstrated by the following tabulated sound measurements which have been carried out for different grain sizes under otherwise similar conditions.  
 Noise level As a general rule, the sound dampening effect increases with decreasing grain size. However, there is a lower limit of the grain size which is governed by the requirement that with too small grain size the condensed heating liquid flows poorly to the heating surfaces.  
  Advantageously, a packing in the vacuum vessel formed of sand of the aforementioned grain sizes is covered at the top with sand of a coarser granulation or grain size or a sieve. In this way relative movement of the grains with respect to one another is dampened, and thus, wear of both the equipment walls as well as the grains is reduced.  
  The fill height of the granular obstruction or damming-up or dam-up means advantageously extends up to at least approximately the height of the liquid level at the vacuum vessel, preferably above the liquid level.  
  According to another preferred embodiment of the invention, there is employed as the obstruction or damming-up means, a compact, yet porous body which fills the vacuum vessel at least approximately to the height of the liquid level, preferably beyond the liquid level.  
  Suitable as the compact porous body there can be in particular advantageously employed: ceramic sintered bodies; metallic sintered bodies; molded bodies formed of porous natural stone, such as tuff; sintered bodies formed of plastic which throughout the prevailing operating temperatures are resistant to the liquid, for instance polytetrafluoroethylene; plastic foams resistant to the liquid over the prevailing operating temperatures; molded bodies formed of glass fibers adhesively bonded together by a suitable binder or binding agent resistant&#39;to the liquid at the prevailing operating temperatures.  
  During fabrication of the equipment of this development the compact. porous body can be either introduced into the vacuum compartment as a prefabricated molded body or, however, it can be formed in situ in the ,vac uum compartment by sintering bonding or foaming the appropriate raw materials. The lastmentioned fabrication technique has the advantage that there is automatically formed a body of the desired dimensions, so that no further processing or other work is necessary.  
  In comparison to other small component-obstruction or damming-up means, such type compact bodies possess the beneficial result that they remain in place in the vacuum vessel even during transport. Consequently, the equipment of this development can be finish-produced at the factory and subsequently transported to the&#39;desired site without undertaking any spe cjal measures.  
 BRIEF DESCRIPTION OF THE DRAWING The invention will be better understood and objects other than those set forth above, will become apparent when consideration is given to the following detailed description thereof. Such description makes reference to the annexed drawing wherein:  
  FIG. 1 is a schematic longitudinal sectional view through a combination heating boiler for heating water and water of consumption equipped with a first embodiment of apparatus for sound dampening at the vacuum vessel or container;  
 I FIG. 2 is a fragmentary view, on an enlarged scale, illustrating the lower portion of such heating boiler with a second embodiment of apparatus for sound dampening provided at the vacuum vessel; and  
  FIG. 3 is&#39;a fragmentary view showing a detail of a modified form of obstruction means.  
 DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Describing now the drawing, the heating boiler depicted in FIG. 1 will be understood to embody an outer completely enclosed vacuum vessel or container I having a bell-shaped inwardly domed floor 2. Within this vacuum vessel 1 there is arranged in the form of a first heat exchanger a boiler 5 for the water 6 which is to be consumed. Two conduits or pipes 7 and 8 which extend through a sealed throughpassage guide 20 serve for the infeed of fresh water and the withdrawal of the heated water respectively. Within the vacuum vessel 1 there is furthermore arranged a second heat exchanger in form of a tubular or pipe coil 9 for heating water. The vacuum vessel or container 1 is conventionally evacuated to about 18 Torr (mm Hg pressure) and filled at its lower portion with water 4. Within the bell-shaped bottom or floor 2 there is arranged a suitable heating source 10 having a ring-shaped arranged flame 11. The hot gases can escape through a channel or duct 12 which can be connected to a flue or the like. A perforated sheet metal member or plate 13, serving as obstruction or dammingup means, is arranged at or directly beneath the surface of the water.  
  Now, if the heating source 10 is placed into operation, then the flames 11 almost instantaneously bring about the formation of vapor at the heating surfaces of the vessel floor or bottom 2, since the boiling point is very low owing to the vacuum prevailing within the evacuated vessel or container 1. During the formation of large vapor bubbles, water must be displaced. The perforated sheet metal member or plate 13 now prevents the rapid displacement of the water, since such must flow through the perforations or holes 13a of the perforated plate member 13. As a result, there prevails for a short period of time a pressure increase at the water 4 which opposes the formation of larger vapor bubbles and thus also dampens the development of noise. The size and number of perforations 13a at the sheet metal member or plate 13 must be, of course, ac-  
 commodated to the heating load in such a manner that.  
 there always prevails a sufficient pressure in order to realize the desired sound suppression.  
  In FIG. 2 there is schematically illustrated, on an enlarged scale, only the lower portion of a boiler. Instead of using in this case a perforated sheet metal member or plate, as was taught for the embodiment of FIG. 1, in the embodiment of FIG. 2 particulate material e.g., granular material 14, serving as the obstruction means, is filled into the lower portion of the vessel 1 containing the water 4. As the granular material, there can be used the materials discussed above. Further, this granular material may consist of, for instance, sand of a finer size covered by a layer of sand of coarser granulation. In a manner analogous to the function of the perforated sheet metal member or plate 13, here also the granular material 14 prevents the rapid displacement of the water during the formation of vapor bubbles, so that localized overpressure regions prevail at the water which oppose the formation of large vapor bubbles and therefore suppress the development of noise.  
  It would be, of course, possible, while still practicing the underlying concepts of this development, to make certain modifications and changes. Hence, it would be conceivable to arrange, for instance, a number of perforated sheet metal members 13 or those of a different shape in the water 4. Furthermore, both features can be combined in that, for instance, there can be provided granular material 14 and above such granular material a perforated sheet metal member or sieve 13, as shown in phantom lines in FIG. 2, or granular material can be arranged in sandwich-like manner in the water bath between two perforated sheet metal members or sieves. Furthermore, perforated sheet metal members or plates can be employed in combination with pervious wire mesh or with porous coverings or layers. As shown in FIG. 3, it would be also possible to use a non-planar Le, a conical-shaped or domed sheet metal member or plate 30 arranged at the water bath and which, only at the region of its highest point or apex, is provided with openings 31 for the throughpassage of the water and vapor. Further, as indicated in phantom lines at the left of FIG. 1 and with reference character 40, there can be employed as the obstruction means a compact but porous body which fills the vacuum vessel at least to the surface, or even beyond, the level of the heating liquid.  
  While there is shown and described present preferred embodiments of the invention, it is to be distinctly understood that the invention is not limited thereto, but may be otherwise variously embodied and practiced within the scope of the following claims. Accordingly,  
 What is claimed is:  
  1. A method for dampening the development of sound occurring at a liquid heater having a vacuum vessel adapted to contain a heating liquid and operating according to the vacuum vaporization principle owing to pronounced development of vapor at the heating surfaces thereof, comprising the steps of providing noise suppression means comprising particulate material having a grain size less than 5 mm, said material disposed within said vacuum vessel and at least partially filling the space therein occupied by said heating liquid, and opposing the formation of vapor bubbles at the heating liquid by means of said noise suppression means.  
  2. The method as defined in claim 1, including the step of selecting a particulate material having a grain size in the range of 1.5 to 5 mm.  
  3. The method as defined in claim 2, wherein the selected particulate material has a grain size in the range of 1.5 to 2mm.  
  4. The method as defined in claim 1, including the step of selecting sand as the particulate material.  
  5. The method as defined in claim 4, wherein the selected sand is quartz sand.  
  6. The method as defined in claim 4, including the step of covering the sand at its top with a layer of sand of coarser granulation.  
  7. The method as defined in claim 4, including the step of covering the sand with a sieve.  
  8. The method as defined in claim 1, including the step of filling said vacuum vessel of the liquid heater with the particulate material at least up to approximately the surface of the heating liquid thereof.  
  9. The method as defined in claim 1, including the step of filling the vacuum vessel of the liquid heater with the particulate material to a level exceeding the surface of the heating liquid thereof.  
  10. The combination with a liquid heater working according to the vacuum vaporization principle and including a vacuum vessel containing a heating liquid, of means for suppressing the formation of noise at the liquid heater, said noise suppression means comprising particulate material having a grain size less than 5 mm, said material disposed within said vacuum vessel and at least partially filling the space therein occupied by said heating liquid.  
  11. The combination as defined in claim 10, wherein the particulate material has a grain size in the range of 1.5 to 5 mm.  
  12. The combination as defined in claim 10, wherein the granular material possesses a grain size in the range of 1.5 to 2 mm.  
  13. The combination as defined in claim 10, wherein the particulate material is sand.  
  14. The combination as defined in claim 13, wherein the sand is quartz sand.  
  15. The combination as defined in claim 13, wherein the sand is covered at its top with a layer of sand of coarser granulation.  
 16. The combination as defined in claim 13,-wherein to a point exceeding the surface of the heating liquid.  
  UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION PATENT NO. 3,877,511  
 DATED April 15, 1975 |NVENTOR(5) WILLI BRANDL, ZDENEK KOULA and PETER NIRK It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:  
 In the Heading, left-hand column, after item [21] insert as a new line the following:  
 -[30] Foreign Application Priority Data September 20, 1972 Switzerland 13752/72 and September 20, 1972 Switzerland l3753/72- Signed and Scaled this sixteenth D a y 0; March I 9 76 [SEAL] A ties t:  
 RUTH C. M A SON C. MARSHALL DANN Arresting Ojflcer Commissioner uj&#39;Patenrs and Trademarks