AU637135B2

AU637135B2 - Water heater

Info

Publication number: AU637135B2
Application number: AU62042/90A
Authority: AU
Inventors: Arthur Maurice Meredith
Original assignee: Individual
Current assignee: Individual
Priority date: 1989-09-01
Filing date: 1990-08-30
Publication date: 1993-05-20
Anticipated expiration: 2010-08-30
Also published as: AU6204290A

Description

COMMONWEALTH OF AUSTRALI 3 Patents Act 1952 COMPLETE SPECIFICATION (Original) FOR OFFICE USE Application Number: PJ6118 Lodged: 1/9/89 Complete Specification Lodged: Accepted: Published: Priority: Related Art: Class Int. Class 0 TO BE COMPLETED BY APPLICANT 0 a Name of Applicant: Address of Applicant: Actual Inventor: Address for Service:- Arthur Maurice MEREDITH 45a Manash Avenue, Como, in the State of Western Australia, Commonwealth of Australia Arthur Maurice MEREDITH 0 Wray Associates Primary Industry House 239 Adelaide Terrace Perth Western Australia 6000.

Complete Specification for the invention entitled: "WATER HEATER" The following statement is a full description of this invention, including the best method of performing it known to me:- 1 2 THIS INVENTION relates to a hot water system, particularly a hot water system for the delivery of low temperature, hot water at faucets and shower heads.

Low temperature, hot water is required under regulations in some constituencies, in places such as hospitals and other institutions, as opposed to a normal or high temperature hot water. Typically low temperature, a hot water temperature of 46 0 C is required.

In order to meet the requirements of these regulations mixing valves have been utilised to mix in cold water at the point of use, or cold water has been mixed into a hot water ring main, each technique providing the low temperature hot water. The mixing valve, however, may provide a source of legionella contamination which is difficult to remove, especially if there are no decontamination procedures. A solution to this problem might appear to use a large storage tank, thermostatically controlled to hold water at the low temperature required.

However, it has been found that legionella bacteria can multiply rapidly within such a storage cylinder owing to stratification and stagnation in the lower levels.

It is an object of this invention to provide a low temperature, hot water heater which obviates or at least reduces the effect of at least some of the aforementioned m •problems.

The present invention provides a liquid heater comprising storage means for containing a fluid which can be heated, a *..liquid flow path including heat exchange means disposed within said storage means in heat exchange relationship with said fluid and having an inlet means and an outlet means, wherein a liquid passing along said liquid flow path between said inlet means and said outlet means can receive heat from said fluid, said liquid flow path maintaining 3 said liquid in isolation from said fluid, and wherein said storage means is connected to an external heating means, there being provided a first pumping means for recirculating said fluid through said heating means, said heating means being controlled by a sensor means responsive to the temperature of said fluid proximate said heat exchange means and said inlet means.

The present invention also provides a water heating system comprising a water heater having storage means for containing a fluid, said storage means being connected to an external heating means for heating said fluid, there being provided a first pumping means for recirculating said fluid through said heating means, a water flow path including heat exchange means disposed within said storage means in heat exchange relationship with said fluid, said heat exchange means having an inlet means for connection to a source of water and an outlet means fo: connection to a water delivery line, wherein water passing along said water flow path can receive heat from said fluid, with said water flow path maintaining said water in isolation from said fluid, and wherein said heating means is controlled by a sensor means responsive to the temperature of said fluid proximate said heat exchange means and said inlet means.

Further, the present invention provides a method of providing a supply of heated water wherein a body of fluid is heated to and maintained at a predetermined temperature or temperature range, and a body of water is provided with heat exchange means to thermally contact said body of said fluid, while maintaining said body of fluid in fluid isolation from said body of water, wherein said body of water heated in this manner is supplied to at least one faucet, wherein said body of water is continuously recirculated through said heat exchange means, in fluid isolation from said body of said fluid, and through a ring main for supply to at least one faucet, said ring main e)

N

4 being provided with replenishment means for replacing water drawn from said at least one faucet, and said heat exchange means being connected to an external heating means which is controlled in response to variation of the temperature of said body of water, said temperature being measured at a location proximate both the heat exchange means and an inlet to said heat exchange means.

Preferably said neat exchange means is defined by at least one pipe arranged in tortile configuration. In a preferred form the tortile configuration is helical.

The inlet mean-s and the outlet means of the heat exchange means are preferably adapted to be connected to a ring main for the liquid, the ring main having a second pumping means for recirculating the liquid through the ring main and the heat exchange means. The ring main preferably also has a valve means for drawing off a volume of the liquid, and replenishing means for allowing said volume to be replaced.

The fluid used in the invention is preferably a body of water treated to prevent corrosion of the storage means, **the heating means and the heat exchange means, and to S"i prevent contamination by potential pathogens.

The invention will now be described by reference to the i:0 following description of one specific embodiment thereof as shown in the accompanying drawing: The drawing is a schematic representation of a hot water system incorporating a water heater according to the present invention.

S.The water heating system comprises a water heater indicated generally at 11, and plumbing, part of which is indicated at 12.

5 The water heater has a storage means in the form of a cylindrical tank 13 which is filled with a body of water The body of water 15 is circulated through an external heating means, preferably provided in the form of an externally installed flued type instantaneous gas burner or heater 17, by a first pumping means in the form of a rotary pump 19.

A heat exchange means in the form of a tubular coil assembly 21 is immersed in the body of water 15 held in the tank 13. The lower end of the tubular coil assembly 21 is connected to an inlet pipe 23 and the upper end of the tubular' coil assembly 21 is connected to an outlet pipe The inlet pipe 23 is fed from a replenishment means in the form of feed pipe 27 and a return means in the form of a return pipe 31. Feed pipe 27 includes a one way valve 29, the feed pipe being connected to a cold water supply. The return pipe 31 includes a second pumping means in the form of a second rotary pump 33, and a second one way valve 34.

*e.

S..The outlet pipe 25 and the inlet pipe 23 are connected to a ring main 35 which includes the return pipe 31. A number of faucet feed pipes 39 branch from the ring main 35, these i: in turn are fed to valves 41 which feed faucets 43.

The gas burner 17 and associated rotary pump are controlled in response to temperature variation detected by sensor The sensor 45 is located close to the junction of inlet pipe 23 and coil assembly 21, and senses the drop in water temperature caused when fresh cooler water enters the inlet pipe 23, and senses the drop in water temperature caused by normal thermal losses.

The cylindrical tank is connected to an expansion tank 47 by a pipe 49. The expansion tank 47 has an overflow pipe 51 to remove excess water and is fed via a ballcock valve 53 and a second one way valve 55 from the cold water supply 6 under pressure (not shown), If the level of water in the expansion tank falls due to evaporation, it is replenished to prevent fluid loss in tank 13. The expansion tank, by absorbing variations of water pressure within the cylindrical tank, minimises stresses within the cylindrical tank.

The water contained in the delivery circuit, which includes coil assembly 21, inlet pipe 23, outlet pipe 25 and the plumbing associated with inlet and outlet pipes 23 and is fluidly isolated from the water 15 held in cylindrical tank 13.

All external pipes and tanks of hot water are appropriately thermally lagged (not shown) for maximum efficiency, and minimum thermal loss.

In use, the water 15 is maintained at the desired temperature by gas burner 17 and rotary pump 19 in response to temperature variation detected at sensor 45 and e translated by a thermostatic switch (not shown). When the water reaches the selected temperature, the pump and gas burner shut down. In this embodiment the thermostatic switch is selected or adjusted to a hysteresis of 1.6 0 C, so upon a fall of that temperature at the sensor 45, the gas burner and pump are re-started.

V Any expansion due to heating, air pressure and dissolution of dissolved gasses is safely accommodated by expansion tank 47.

Evaporative losses are also made up for by addition of fresh water in response to low fluid leve' detected by ballcock valve 53.

The body of water 15 in cylindrical tank 13 is used for the purposes of heat transfer to water in the tubular coil 7 assembly of the delivery circuit, and as these bodies of water never mix it is possible to add inhibitors to prevent potentially harmful bacteria from multiplying or to add buffers to prevent corrosion.

Water is circulated though the ring main 35 and coil assembly 21 by second rotary pump 33. As the circulated water passes through coil assembly 21 in thermal contact with the body of water 15, it receives heat from the body of water 15. The pump 33 is a low volume circulatory type pump.

The ring main and del'ivery circuit'are pressurised by the cold water supply connected via feed pipe 27. As hot water is drawn off the ring main at a faucet 41, it is replaced by cold water from feed pipe 27. One way valve 34 acts as an added precaution to prevent cold-water from feed pipe 27 from bypassing the coil assembly 21 to get to faucets 41 directly.

S•The construction of the coil assembly 21 is important to the efficiency of the water heater. It is desirable for :the pipes for this assembly to be of a size such that the S.flow velocity does not exceed 1.5m/s at its fastest flow :rate.

A typical example has a cylindrical tank with a capacity of 500 litres. The delivery circuit utilises 19mm diameter copper pipe which join the coil assembly. The coil assembly is made of five 20 metre long pieces of 12.7mm diameter 19 SWG walled copper pipe connected in parallel.

.4 The gas burner is a 106 MJ unit which in trials used 23.5 kW/Hr to maintain a hot water temperature at 46 0 C with a continuous flow rate drawn from faucets of 11.6 litres per minute. The temperature of input cold water was 16 0

C.

8 The flow rate could be increased to 23 litres per minute for fifteen minutes with a resultant average drop in hot water temperature of 2 0 C from the required temperature of 46 0

C.

For maximum efficiency it has been found that the coil assembly 21 should be located over 75% of the height of the cylindrical tank 13 in such a manner to leave the lower free from cooled water to drop away, and hot water from the gas burner 17 is fed in so that it convects through the coil assembly 21.

There can also be provision in the thermostatic switch control circuit to allow for periodically and temporarily raising the temperature to that suitable for flushing and sterilising the hot water system.

It should be appreciated that the scope of the i.vention is not limited to the scope of the embodiment described herein.

o o*m •o* **i

Claims

1. A liquid heater comprising storage means for containing a fluid which can be heated, a liquid flow path including heat exchange means disposed within said storage means in heat exchange relationship with said fluid and having an inlet means and an outlet means, wherein a liquid passing along said liquid flow path between said inlet means and said outlet means can receive heat from said fluid, said liquid flow path maintaining said liquid in isolation from said fluid, and wherein said storage means is connected to an external heating means, there being provided a first pumping means for recirculating said fluid through said heating means, said heating means being controlled by a sensor means responsive to the temperature of said fluid proximate said heat exchange means and said inlet means.

2. A liquid heater according to claim 1 wherein said heat exchange means is defined by at least one pine arranged in •tortile configuration. e

3. A liquid heater according to 2 wherein said tortile Sconfiguration is helical.

4. A liquid heater according to any one of claims 1 to 3, wherein said inlet means and said outlet means are adapted for connection to a ring main for said liquid, said ring main having a second pumping means for recirculating said liquid through said ring main and said heat exchange means, and having valve means for drawing off a volume of said liquid and replenishing means for allowing said volume to be replaced.

A water heating system comprising a water heater having storage means for containing a fluid, said storage means being connected to an external heating means for A1d$ heating said fluid, there being provided a first pumping means for recirculating said fluid through said heating means, a water flow path including heat exchange means disposed within said storage means in heat exchange relationship with said fluid, said heat exchange means having an inlet means for connection to a source of water and an outlet means for connection to a water delivery line, wherein water passing along said water flow path can receive heat from said fluid, with said water flow path maintaining said water in isolation from said fluid, and wherein said heating means is controlled by a sensor means responsive to the temperature of said fluid proximate said heat exchange means and said inlet means.

6. A water heating system according to claim 5 wherein said heat exchange means is defined by at least one pipe arranged in tortile configuration.

7. A water heating system according to claim 6 wherein said tortile configuration is helical.

8. A water heating system according to any one of claims 5 to 7, wherein said delivery line is connected to said inlet means to form a ring main, a second pumping means being provided for circulating water through said ring main and said fluid flow path.

9. A liquid heater according to any one of claims 1 to 4 I wherein said fluid is a body of water treated to prevent corrosion of said storage means, heating means, and heat exchange means, and prevent contamination by potential :pathogens.

A water heating system according to any one of claims to 8 wherein-said fluid is a body of water treated to prevent corrosion of said storage means, heating means, and 1': 11 heat exchange means, and prevent contamination by potential pathogens.

11 A method of providing a supply of heated water wherein a body of fluid is heated to and maintained at a predetermined temperature or temperature range, and a body of water is provided with heat exchange means to thermally contact said body of said fluid, while maintaining said body of fluid in fluid isolation from said body of water, wherein said body of water heated in this manner is supplied to at least one faucet, wherein said body of water is continuously recirculated through said heat exchange means, in fluid isolation from said body of said fluid, and through a ring main for supply to at least one faucet, said ring main being provided with replenishment means for replacing water drawn from said at least une faucet, and said heat exchange means being connected to an external heating -means which is controlled in response to variation of the temperature of said body of water, said temperature being measured at a location proximate both the heat exchange means and an inlet to said heat exchange means. see: *00 0

12. A method according to claim 11 wherein said heat S"exchange means is a length of tube located in said body of said fluid, wherein said length of tube has an interior which is fluidly isolated from.said body of said fluid. @0 *3

13. A liquid heater according to claim 1 substantially as herein described in relation to the accompanying drawing. 0

14. A water heating system according to claim substantially as herein described in relation to the accompanying drawing. accompanying drawing. U W 12 A method according to claim 11 substantially as herein described in relation to the accompanying drawing. DATED this TWENTY SECOND day of FEBRUARY 1993 ARTHUR MAURICE MEREDITH Applicant. WRAY ASSOCIATES, Perth, Western Australia, Patent Attorneys for the Applicant. 4 4 4 0 ~0 4S 04 S 0S 0s *44e .4 9 0~ S 44 *4 4 .4 4 .4