AU2013202028B2 - Water Storage Heaters - Google Patents

Abstract

Abstract: A water storage heater comprising a water storage tank located over a combustion chamber in communication with an 5 air inlet, the tank being enclosed within an outer wall, the combustion chamber being in communication with a heat transferring flue duct to transfer combustion products to the exterior, the flue duct extending through the tank to a heat exchanger chamber defined between the exterior of 10 the tank and the outer wall, the heat exchanger chamber having an outlet aperture coupled to a discrete substantially rectangular exhaust enclosure, the exhaust enclosure being positioned on the exterior of the outer wall. 4128619_2 (GHMatters) P89901.AU.1 26/03/13 Figure 1 I -. c cKA' rFi ,, _, t

Description

- 1 WATER STORAGE HEATERS This invention relates to water storage heaters and more particularly to gas powered storage heaters that 5 incorporate an internal flue. Water storage heaters that operate on gas usually have a combustion chamber at the base of a water tank. A heat transferring flue duct is directed through the tank 10 to direct the combustion products to an exhaust. The tank is usually insulated and placed within an external housing. For energy conservation reasons is important that 15 water heaters of this kind operate in a highly efficient manner. This is assessed on the efficiency of the water heater in terms of the amount of fuel that is required to heat the water and the capacity of the water to maintain its temperature, in other words, the insulation of the 20 heater. Heaters of this kind are often located outside and thus the effects of external wind can cause problems such as affecting the airflow to the combustion chamber, quality of combustion, drawing heat from the water tank or extinguishing the pilot flame. 25 The combustion products contain useful heat so there is thus a need to route and direct the hot combustion products so that as much heat as possible can be passed to the water contained in the tank. However, slowing down 30 the velocity of the combustion products can cause problems with combustion quality and there is thus a balance between providing a convoluted combustion products passage that allows the heat to be transferred to the water tank and ensuring good flow of combustion products for 35 efficient combustion. The external wind currents are also a factor that play on this dilemma. 6486065_1 (GHMatters) P89901.AU. 1 TERUNI 11/05/15 - 2 It is these issues that have brought about the present invention. In one aspect of the present invention there is 5 provided a water storage heater comprising a housing containing a water storage tank located over a combustion chamber in communication with an air inlet, the tank being surrounded by an outer wall inside the housing, combustion chamber being in communication with a heat transferring 10 flue duct to transfer combustion products to the exterior, the flue duct extending through the tank to a heat exchanger chamber defined by a space between the tank and the outer wall, the heat exchanger chamber having an outlet aperture coupled to a discrete exhaust enclosure, 15 the exhaust enclosure being positioned on the exterior of the outer wall. In an embodiment described herein there is provided a baffle for suspension in the flue duct of a gas water 20 heater, the baffle comprising an elongate spine having lateral extending spaced fins and a series of spaced restrictors secured to the spine whereby combustion products flow in the flue is impeded, and slowed by the fins and restrictors and directed against the walls of the 25 flue duct. Embodiments of the present invention will now be described by way of example only with reference to the accompanying drawings in which: 30 Figure 1 is a cross sectional conceptual view of a storage water heater, Figure 2 is a perspective transparent image of the water heater, Figure 3 is a perspective view of the water heater 35 with insulation and outer casing removed, Figures 4a and 4b are side and front elevation views of the water heater with the insulation and outer casing 6486065_1 (GHMatters) P89901.AU. 1 TERUNI 11/05/15 -3 removed, Figure 4c is a plan view of the water heater, Figure 5 is a perspective view of the base of the water heater showing fins in an exhaust chamber, 5 Figure 6 is a perspective view of the base of the water heater showing different fins within the exhaust chamber, and Figure 7 is a perspective view of a section of the baffle for use in a flue of the water heater 10 The accompanying drawings illustrate a gas powered storage water heater 10. The heater 10 has an external sheet metal housing 11 that is an elongate rectangle standing with its longer axis vertical. The housing 11 15 defines a base 12, top 13 and sides 14, 15, 16 and 17. The housing 11 contains a cylindrical water tank 20 supported by a leg structure 21 that defines, with the underside of the water tank, a combustion chamber 22. The combustion chamber 22 contains a gas burner 24 and a pilot 20 flame mechanism conventional to heaters of this kind. The gas controller 28 is mounted on the front of the tank 20. The front wall 14 of the housing 11 has a rectangular enclosure 18 located towards the base of the heater 10. 25 The enclosure 18 has a removable panel (not shown) providing access to the combustion chamber 22 and gas controller 28 of the heater. The sides 61, 62 of the enclosure 18 include air vents 19 that facilitate entry of air for combustion and exit of combustion products. A 30 horizontal plate 63 separates the enclosure into a lower air inlet chamber 64 and an upper exhaust outlet 65. The position and orientation of the vents 19 ensure a pressure balance between the combustion air inlet and combustion products outlet notwithstanding the potential of strong 35 external winds. The cylindrical water tank 20 is located within a 6486065_1 (GHMatters) P89901.AU. 1 TERUNI 11/05/15 - 4 cylindrical metal outer casing 25. The outer casing surrounds the tank so that there is a narrow space 30 around the sides and top of the tank. This space forms a heat exchanger chamber 30. The combustion chamber 22 has 5 a flue in the form of a duct 31 extending centrally through the water tank 20 to merge with the heat exchanger chamber 30. The heat exchanger chamber 30 has an arcuate aperture 33 located at the base of the heater 10. 10 As shown in Figures 3 and 4 a substantially rectangular exhaust chamber 40 is attached to the exterior of the base of the cylindrical casing 25 over the outlet aperture 33 (Figure 1)of the heat exchanger chamber 30. The exhaust chamber 40 is defined by a rectangular front 15 panel 71 with diverging sides 72, 73 that abut the exterior of the casing 25. Arcuate end plates 74 seal off the top and bottom of the chamber 40. The chamber 40 extends around the cylindrical casing 25 for about 1200. The exhaust chamber 40 sits towards the base of the water 20 heater 10 above the combustion chamber 22 between the casing 25 and the enclosure 18. The combustion products enter the exhaust chamber 40 at its base to escape via a rectangular aperture 42 located closer to the top of the exhaust chamber 40. As shown in Figure 2 the air entry to 25 the combustion chamber 22 is via the vents 19 in the front panel through the inlet chamber 64 and through an aperture 38 at the base of the heater 10. The combustion products escape from the exhaust chamber 40 via the outlet aperture 42, and through the side vents 23 in the front panel. The 30 side vents 19 in the inlet chamber 64 are placed in front of appropriate baffles 66, 67 to reduce the influence of high and low winds on combustion quality. The exhaust chamber 40 includes a series of baffles 35 in a form of vertical fins 45 or tubular baffles 46, see Figures 5 and 6. The fins 45 or baffles 46 aids laminar flow of the combustion products to the enclosure 18 and 6486065_1 (GHMatters) P89901.AU. 1 TERUNI 11/05/15 - 5 reduces the effect of combustion turbulence caused by high and low winds around the exhaust chamber aperture 42. The exhaust chamber is in direct contact with the exterior of the cylindrical casing 25 to act as a secondary heat 5 exchanger that ensures that virtually all of the heat in the combustion products is extracted and transferred to the water tank via conduction through the walls. As shown in Figure 1 a baffle 50 is inserted into the 10 central duct 31 of the flue to increase the residence time of the combustion products by reducing their velocity and directing the combustion products against the walls of flue duct. If the residence time of the combustion products can be increased and directed there is much more 15 opportunity for the heat in the combustion products to be transferred by conduction into the surrounding water tank 20. The baffle 50 that is shown in detail with reference 20 to Figure 7 is formed out of metal, preferably galvanized metal to form an elongated spine 55 that has been formed to provide a series of downwardly inclined fins 51 to ensure that the gases conduct a convoluted and somewhat helical passage up the flue duct 31 thus maximising the 25 contact time of the combustion products with the walls of the flue duct. A series of annular flow restrictors 56-58 are positioned spaced apart along the spine 55 to impede and direct the passage of the combustion products thereby increasing the turbulent flow along the flue duct 31 and 30 further ensuring maximum contact time of the combustion products with the walls of the flue duct. The annular flow restrictors 56-58 and fins 51 are designed so that there is an air gap between their outer edges and the adjacent wall of the water tank. The baffle 50 is 35 suspended from the top of the tank 20 via suitable attachment means (not shown). 6486065_1 (GHMatters) P89901.AU. 1 TERUNI 11/05/15 - 6 The baffle 50 is designed to define a complex labyrinth for the passage of the exhaust gases, which has the effect of impeding the flow of the combustion products so that the combustion products have a complex and 5 somewhat turbulent passage up the length of the central flue duct 31 whilst being directed to the wall of the flue duct for maximum contact. The baffle 50 is also designed so that it does not directly contact the wall of the water tank to reduce the likelihood of the baffle itself causing 10 loss of heat of the water in the tank through conduction whist the main burner is not operating. The combination of the inclined fins 51 and the annular flow restrictors 56-58 substantially reduces the flow of the combustion products whilst at the same time ensures that there is 15 sufficient air drawn into the base of the heater to provide good quality combustion. Because the coldest water is at the base of the tank 20 the baffle 50 reduces the velocity of combustion products at the start of the duct 31 and maximises the contact time of the hot 20 combustion products and the wall of the flue duct adjacent the gas controller . The baffle 50 is designed to ensure the highest rate of heat absorption at the base of the tank with the rate of heat absorption tailing off towards the top of the flue duct 31. 25 The number and spacing of the annular flow restrictors can be varied to alter the rate of heat transfer. It is also understood that the centre of the annular restrictors could consist of a single or multiple 30 geometric shape(s) or formed as an open mesh with fixed or variable apertures. The flue duct acts as a heat exchanger and draws heat from the combustion products to be transferred into the 35 water tank 20 through the internal duct 31 and via the heat exchanger chamber 30 on the exterior of the tank. It is understood that the exterior of the tank 20 is wrapped 6486065_1 (GHMatters) P89901.AU. 1 TERUNI 11/05/15 - 7 in suitable insulation 48 that sits between the tank and the outer housing 11. At the lower end of the heater 10 where there is less room for insulation a lower level of insulation is envisaged. 5 Although in the preferred embodiment the exhaust chamber 40 is positioned towards the base of the water heater 10 it is understood that it could be located further up the water heater or possibly on a side opposite 10 the combustion chamber inlet aperture 29. The dimensions of the duct 31, flue chamber 30 and exhaust chamber 40 are designed to slow the velocity of combustion products to allow transfer of heat to the water tank 20 whilst still allowing sufficient flow so that air can be drawn into the 15 base of the water heater 10 for good quality combustion. The baffles 45, 46 and structure of the exhaust chamber 40 are arranged so that the combustion chamber 40 and interior of the heater are not detrimentally affected by high or low winds on the exterior of the water heater. 20 The cross section of the exit aperture 33 of the heat exchanger chamber 30 is selected to ensure the desired flow of combustion products into the exhaust chamber 40. 25 The size and position of the exhaust chamber 40 relative to the heat exchanger chamber 30 have been carefully selected to ensure that there is a volumetric ratio between the two chambers. The exhaust chamber 40 has a reduced cross section to reduce heat loss. The 30 dimension of the exhaust chamber 40 can be simply varied to establish the desired volumetric ratio without excess loss of heat. The cross sectional area and size of the arcuate aperature 33 has also been carefully calculated and determined as a function of the offset distance of the 35 annular flow directing case from the exterior of the water tank wall and the outer circumference of the water tank 20. 6486065_1 (GHMatters) P89901.AU. 1 TERUNI 11/05/15 - 8 These variation may be necessary for different gas types and operating conditions or the varying certification or performance requirements of different 5 countries. The convoluted flow of the flue path acts as a heat trap, ensuring that when the main burner is off the radiant heat from the flue duct 31, cylindrical water tank 10 20 and the convection heat from the pilot flame is stalled thus keeping the heat within the heater and further reducing heat escaping from the side vents 23. The water heater is designed so that its overall 15 efficiency mainly in terms of fuel consumption and maintenance of water temperature achieves the lowest possible energy consumption. In the claims which follow and in the preceding 20 description of the invention, except where the context requires otherwise due to express language or necessary implication, the word "comprise" or variations such as "comprises" or "comprising" is used in an inclusive sense, i.e. to specify the presence of the stated features but 25 not to preclude the presence or addition of further features in various embodiments of the invention. 6486065_1 (GHMatters) P89901.AU. 1 TERUNI 11/05/15

Claims (15)

1. A water storage heater comprising a housing containing a water storage tank located over a combustion chamber in 5 communication with an air inlet, the tank being surrounded by an outer wall inside the housing, the combustion chamber being in communication with a heat transferring flue duct to transfer combustion products to the exterior, the flue duct extending through the tank to a heat 10 exchanger chamber defined by a space between the tank and the outer wall, the heat exchanger chamber having an outlet aperture coupled to a discrete exhaust enclosure, the exhaust enclosure being positioned on the exterior of the outer wall. 15

2. The water storage heater according to claim 1 wherein the exhaust enclosure is defined by a rectangular outer wall secured to the outer wall of a cylindrical tank by diverging side walls. 20

3. The water storage heater according to either claim 1 or 2 wherein an exhaust outer chamber and an air inlet chamber are formed by a covering enclosure located on the exterior of the heater in communication with the exhaust 25 enclosure, the enclosure having side walls defining similarly orientated air vents that define an exhaust outlet and an air inlet.

4. The water storage heater according to any one of the 30 preceding claims wherein a series of spaced baffles are positioned on the interior of the exhaust enclosure.

5. The water storage heater according to claim 4 wherein the baffles extend either vertically or horizontally. 35

6. The water storage heater according to either claim 4 or claim 5 wherein the baffles are tubular. 6486065_1 (GHMatters) P89901.AU. 1 TERUNI 11/05/15 - 10

7. The water storage heater according to any one of the preceding claims including insulation provided inbetween the outer wall and the housing, the exhaust outer chamber 5 and air inlet chamber being positioned externally of the housing.

8. The water storage heater according to any one of the preceding claims wherein a baffle assembly is suspended to 10 extend along the flue duct.

9. The water storage heater according to claim 8 wherein the baffle assembly comprises an elongate spine having laterally extending spaced fins and a series of spaced 15 restrictors secured to the spine whereby combustion products flow in the flue is impeded, slowed by the fins and restrictors and directed against the walls of the flue duct. 20

10. The water storage heater according to claim 9 wherein the lateral projection of the fins and restrictors is less than the width of the duct.

11. The water storage heater according to either claim 9 25 or claim 10 wherein an elongate blank is formed to define fins that are shaped out of the body of the blank.

12. The water storage heater according to any one of claims 9 to 11 wherein the spacing of the restrictors is 30 adjustable.

13. The water storage heater according to any one of claims 1 to 12 wherein there is a volumetric ratio between the exhaust chamber and the heater exchanger chamber can 35 be between 1:50 to 1:65.

14. The water storage heater according to any one of the 6486065_1 (GHMatters) P89901.AU. 1 TERUNI 11/05/15 - 11 preceding claims wherein the cross sectional area and size of the outlet aperture is calculated as a function of the offset distance of the outer wall from the exterior of the water tank and the outer circumference of the water 5 tank.

15. A water storage heater substantially as described herein with reference to and as illustrated in the accompanying drawings. 10 6486065_1 (GHMatters) P89901.AU. 1 TERUNI 11/05/15