NZ586368A

NZ586368A - A hot water tank where the hot water is diluted with cooler water drawn from a dilution duct by a venturi effect

Info

Publication number: NZ586368A
Application number: NZ586368A
Authority: NZ
Inventors: Patrick Pussell
Original assignee: Dux Mfg Ltd
Priority date: 2008-12-11
Filing date: 2009-11-03
Publication date: 2012-06-29
Also published as: AU2009324262A1; WO2010065985A1; AU2009324262B2

Abstract

A hot water system includes a tank 10 having a top 12b and a bottom 12c, a heating element 20 at or near the bottom 12c of the tank 10, a cold water inlet duct 22 at or near the bottom 12c of the tank 10, a heated water outlet duct at or near the top 12b of the tank 10, the heated water outlet duct 28 having an inlet end 30 and an outlet end 32, and a dilution duct 34 having an inlet end 36 at or near the bottom 12c of the tank 10 and an outlet end 38 within the heater water outlet duct 28 and between the inlet end 30 and the outlet end 32 of the heated water outlet duct 28. Heated water flowing from the inlet end 30 to the outlet end 32 of the heated water outlet duct 28 draws water, via a venturi effect, from the dilution duct inlet end 36 to the dilution duct outlet end 38, where it mixes with the heated water flowing through the heater water outlet duct 28.

Description

1 A HOT WATER SYSTEM AND A METHOD OF OPERATING SAME Field of the Invention The present invention relates to a hot water system and a method of operating same.

The invention has been primarily developed for use as a 50 litre nominal delivery capacity hot water system with an internal electric heating element and will be described hereinafter with reference to this application. However, it will be appreciated by persons skilled in the art that the invention is not limited to this particular application and is also suitable for other nominal delivery capacities and hot water systems using gas burners.

Background of the Invention The Australian Standards testing for a 50 litre nominal delivery capacity hot water system (according to ASNZ 4692.1 2005 Appendix D) begin with heating the water within the system's tank to a fixed temperature (e.g. 75° C). The heated water outlet of the system is then opened to an extent that hot water flows at a (controlled) rate of 10 litres per minute. The outlet temperature of the water leaving the heated water outlet is measured during this process and the flow is stopped when the water temperature has fallen by 12° K. The volume discharged during the time taken for the 12° K temperature drop becomes the nominal delivery capacity of the tank, such that the tank can then be classed (e.g. for regulatory and advertising purposes) as a tank having that capacity.

The physical external dimensions of hot water systems of this type are constrained to a historical size that fits within the cabinetry of apartments dating back to the 1960's, principally in Sydney, Australia. Changes to heat loss regulations in the 1990's forced an increase in the thickness of the insulation surrounding the system's tanks. This caused a reduction of the internal volume of the tank, given the constraints on the system's external dimensions. As a result, many existing designs of 50 litre nominal delivery capacity hot water systems can not comply with both the heat loss regulations and the external dimension constraints.

For example, one known system uses an internal pipe from the cold water inlet plumbed directly to the heated water outlet. In this system, a proportion of the incoming cold water mixes directly with the outgoing hot water. However, the cooling effect is too great and the system is only rated as a 45 litre nominal delivery capacity when tested in accordance with the above Standard. Another known system uses a physically relatively 2 large tank surrounded by relatively thin, but very dense insulation. However, a 50 litre nominal delivery capacity was not obtainable when tested in accordance with the above Standard.

Object of the Invention It is an object of the present invention to provide a hot water system able to meet the nominal delivery capacity, heat loss regulations and the external dimension constraints, when tested in tested in accordance with the above Standard.

Summary of the Invention Accordingly, in a first aspect, the present invention provides a hot water system including: a tank having a top and a bottom; a heating element at or near the bottom of the tank; a cold water inlet duct at or near the bottom of the tank; a heated water outlet duct at or near the top of the tank, the heated water outlet duct having an inlet end and an outlet end; and a dilution duct having an inlet end at or near the bottom of the tank and an outlet end within the heater water outlet duct and between the inlet end and the outlet end of the heated water outlet duct, wherein heated water from flowing from the inlet end to the outlet end of the heated water outlet duct draws water, via a venturi effect, from the dilution duct inlet end to the dilution duct outlet end, whereafter it mixes with the heated water flowing through the heater water outlet duct.

The heated water outlet duct inlet end preferably includes a diffuser, most preferably formed from a mesh or screen. The diffuser is preferably substantially adjacent the top of the tank.

The cold water inlet duct outlet end preferably includes a diffuser, most preferably formed from a mesh or screen. The diffuser is preferably substantially adjacent the bottom of the tank.

The dilution duct preferably has an inner diameter of about 25 to 30 % of the inner diameter of the heated water outlet duct. 3 The dilution duct preferably has an inner diameter of about 5 to 8 mm. The inner diameter of the heated water outlet duct is preferably about 15 to 20 mm. The inner diameter of the cold water inlet duct is preferably about 15 to 20 mm.

The tank is preferably substantially surrounded with insulation. The insulation is preferably surrounded by a casing.

In one form, the heating element is an electric element inside the tank. In another form, the heating element is a gas burner beneath the tank.

The tank preferable has an internal volume of about 53 litres.

In a second aspect, the present invention provides a method of operating a hot water system, the method comprising: admitting cold water at or near to a bottom of a hot water system tank; heating the water at or near the bottom of the tank; drawing off heated water from at or near the top of the tank; and drawing, via a venturi action, water from at or near the bottom of the tank and mixing it with the heated water being drawn from the tank.

The method preferably includes drawing the heated water from the tank through a heated water outlet duct and mixing the water drawn from at or near the bottom of the tank with the heated water within the heated water outlet duct.

Brief Description of the Drawings A preferred embodiment of the invention will now be described, by way of an example only, with reference to the accompanying drawing in which: Fig. 1 is a cut-away perspective view of an embodiment of a hot water heater system.

Detailed Description of the Preferred Embodiments Fig. 1 shows an embodiment of a hot water heater system 10. The exterior of the system 10 is defined by a cylindrical external casing 12, having the following dimensions: diameter 405 mm; and height 700 mm. These dimensions meet the previously mentioned physical dimension constraints. A water tank 14 having a volume of 53 litres is positioned inside the casing 12. The casing 12 has a cylindrical side wall 12a, a domed top 12b and a domed bottom 12c. The space between the exterior of the tank 14 and the interior of the casing 12 is filled with styrene insulation 16. The top 12b and bottom 12c of the casing 12 have a series of fins 18 about their periphery which serve to key into and 4 locate/engage the insulation 16. An electric heating element 20 is positioned inside the tank 14 near the bottom of the tank 14.

A cold water inlet duct 22, having an internal diameter of 18 mm, is provided inside the tank 14, near the bottom of the tank 14. The duct 22 has an inlet end 24, for connection to a source of mains water, and an outlet end, adjacent the bottom of the tank 14, in the form of a mesh/screen diffuser 26. The diffuser 26 serves to disperse the cold water being admitted to the tank 14 in a manner that assists in temperature stratification within the tank 14.

A heated water outlet duct 28, having an inner diameter of 18 mm, is also provided within the tank 14. The duct 28 has an inlet end, adjacent the top of the tank 14, in the form of a mesh/screen diffuser 30, and an outlet end 32 for connection to, for example, a bath, sink or shower outlet.

A dilution duct 34, having an inner diameter of 5 mm, is also provided within the tank 14. The dilution duct 34 has an inlet end 36, adjacent the bottom of the tank 14, and an outlet end 38, which is near the top of the tank 14 and within the heated water outlet duct 28. An anode 40 is also provided within the tank 14.

During the previously mentioned testing process, heated water is drawn from the tank 14 through the (inlet) diffuser 30 of the heated water outlet duct 28 and exits the system 10 via the heated water duct outlet end 32. The flow of water through the duct 28 passes the outlet end 38 of the dilution duct 34 and creates a venturi action. This venturi action draws cooler water from the bottom of the tank 14 into the dilution duct inlet end 36, through the dilution duct 34, and out through the dilution duct outlet end 38, whereafter it mixes with the heated water flowing through the heated water outlet duct 28.

The effect of this mixing is the temperature of the water leaving the duct outlet 32 is slightly lowered or tempered (by about 5 to 6° C) due to the dilution of the cooler water from the bottom of the tank 14. This dilution or tempering results in a more consistent water temperature at the duct outlet 32 over the total testing draw period and thus increases the delivery capacity. The internal volume of 75° C water is increased due to a larger delivered volume of less than 75° C water through the fixed dilution ratio. As a result, a larger volume of water is delivered during the 12° K temperature drop as compared to a similar hot water system not using the dilution duct 34. Accordingly, the dilution duct 34 results in a tank 14 of a (reduced) physical volume able to meet the external dimension constraints to deliver enough water in accordance with the aforementioned described testing regime to be classified as having a nominal 50 litre delivery capacity. The advantage of this arrangement over existing systems is it allows a physically relatively small tank size to deliver a greater nominal capacity than existing systems.

Although the invention has been described with reference to a specific example, 5 it will be appreciated by persons skilled in the art that the invention may be embodied in many other forms. For example, the invention is also applicable to hot water systems with gas burners. 6

Claims

1. A hot water system including: a tank having a top and a bottom; a heating element at or near the bottom of the tank; a cold water inlet duct at or near the bottom of the tank; a heated water outlet duct at or near the top of the tank, the heated water outlet duct having an inlet end and an outlet end; and a dilution duct having an inlet end at or near the bottom of the tank and an outlet end within the heater water outlet duct and between the inlet end and the outlet end of the heated water outlet duct, wherein heated water from flowing from the inlet end to the outlet end of the heated water outlet duct draws water, via a venturi effect, from the dilution duct inlet end to the dilution duct outlet end, whereafter it mixes with the heated water flowing through the heater water outlet duct.

2. The hot water system as claimed in claim 1, wherein the heated water outlet duct inlet end includes a diffuser

3. The hot water system as claimed in claim 2, wherein the heated water outlet duct inlet end diffuser is formed from a mesh or screen.

4. The hot water system as claimed in claim 2 or 3, wherein the heated water outlet duct inlet end diffuser is substantially adjacent the top of the tank.

5. The hot water system as claimed in any one of the preceding claims, wherein the cold water inlet duct outlet end includes a diffuser

6. The hot water system as claimed in claim 5, wherein the cold water inlet duct outlet end diffuser is formed from a mesh or screen.

7. The hot water system as claimed in claim 5 or 6, wherein the cold water inlet duct outlet end diffuser is substantially adjacent the bottom of the tank. RECEIVED at IPONZ on 7 June 2012 7

8. The hot water system as claimed in any one of the preceding claims, wherein the dilution duct has an inner diameter of about 25 to 30 % of the inner diameter of the heated water outlet duct.

9. The hot water system as claimed in any one of the preceding claims, wherein the dilution duct has an inner diameter of about 5 to 8 mm.

10. The hot water system as claimed in any one of the preceding claims, wherein the inner diameter of the heated water outlet duct is about 15 to 20 mm.

11. The hot water system as claimed in any one of the preceding claims, wherein the inner diameter of the cold water inlet duct is about 15 to 20 mm.

12. The hot water system as claimed in any one of the preceding claims, wherein the tank is substantially surrounded with insulation.

13. The hot water system as claimed in claim 12, wherein the insulation is surrounded by a casing.

14. The hot water system as claimed in any one of the preceding claims, wherein the heating element is an electric element inside the tank.

15. The hot water system as claimed in any one of claims 1 to 13, wherein the heating element is a gas burner beneath the tank.

16. The hot water system as claimed in any one of the preceding claims, wherein the tank has an internal volume of about 53 litres. 6340270_1 RECEIVED at IPONZ on 7 June 2012 8

17. A hot water system substantially as hereinbefore described with reference to the accompanying drawings. Dux Manufacturing Limited By the Attorneys for the Applicant SPRUSON & FERGUSON Per: 6340270_1