WO1996001396A1

WO1996001396A1 - Fluid tempering system

Info

Publication number: WO1996001396A1
Application number: PCT/CA1995/000398
Authority: WO
Inventors: Nazir Dosani; Nizar Ladha
Original assignee: Nazir Dosani; Nizar Ladha
Priority date: 1994-07-04
Filing date: 1995-07-04
Publication date: 1996-01-18
Also published as: CA2127338A1; AU2783395A

Abstract

A fluid tempering system for supplying tempered fluid to hot fluid distribution system (38), for example water at a constant temperature by controlling the amount of cold water from the cold water supply (32) mixing with hot water from the water heater (15), to control the temperature of water in the hot water distribution system (38). The higher temperature water mixed with cold water, reduces scalding hazard and also increase the volume of hot water, at a tempered temperature, within the hot water distribution system (38). The system also eliminates the slug in the tempering sytem.

Description

Field of invention

The present invention is directed to modified storage . heater system that delivers tempered water or other fluid to the user/consumer.

Background of the Invention

The present invention relates to fluid temperature control apparatus. In particular it is concerned with apparatus for providing fluid, for example water, to a user at a required temperature where this achieved by mixing in varying proportions two supplies of liquid at different temperature, designated "cold" and "hot" respectively.

The apparatus is of general application but is best explained in relation to control of a domestic hot water tank.

In a conventional water heating systems, cold water, delivered to a combined water heater/storage tank, is heated to a desired temperature in readiness for demand draw by the user.

In a direct demand system, such as is commonly used for domestic hot water supply, the apprehension of scalding the user, generally results in fixing the maximum temperature to which water may be heated in the water heater tank, to a relatively low setting at or below 60 degree C. (140 degree F.)

However, such tepid water temperature in a stored body of water, can encourage bacterial growth. It would therefore be preferable, for sanitary purposes, if the water in the tank was heated to a ' sani.ti.zi.ng temperature to destroy bacteria or other potential growth organisms.

Trihey, John M. of Australia , (PCT patent number SUBSTITUTE SHEET PCT/AU90/00159) teaches a method of tempering the hot water by creating a flow path between the cold water inlet and the hot water outlet. The flow path is created using a tube of relatively narrow bore and a manual valve is set within the tube to preset the temperature of the water in the distribution system. The ratio of cold water and hot water mix is preset by the size of the tube and the setting of the manual valve. This predetermined ratio does not take into account the varying temperature of cold water supply, the changes in pressure within the hot water tank as the temperature increases or decreases and also as the water is drawn from the hot water tank the temperature within the tank decreases and with preset ratio the user does not get the benefit of the tepid water left in the tank.

Perlman et al. of Canada (US patent number 5,115,491) teaches us a tempering system using a heat exchanger and a valve. To get maximum benefit from this system the water within the storage tank is heated to scalding temperature and also the heat exchanger makes the system too expensive. Further more the heat exchanger is prone to scaling problems.

The present invention overcomes these disadvantages by monitoring the temperature of water in the hot water distribution system and adjusting, in real time, the ratio of cold water mixing with hot water from the tank.

In a preferred embodiment of the invention the ratio of the cold water and hot water mixing is further adjusted by the temperature of water at the hot water outlet and also by the temperature of cold water supply. This method takes care of the seasonal changes in the temperature of cold water supply and also the changes in temperature of hot water from the tank due to heating elements turning on or due to water being drawn from the hot water tank by the user. SUBSTITUTE SHEET In a preferred embodiment of the invention the stepper motor valve which controls the ratio of the cold water mixing with hot water is installed near the cold water inlet. This position reduces the temperature around the valve which can damage the electronic components and also the scaling problem is eliminated as scaling typically occurs on the hot water outlet side.

The present invention further provides a means of preventing slug within the fluid tempering system. Slug is the hot fluid left in the tempering system after the consumer has turned off the flow of fluid or the tempering system is not used for a period of time. The slug is created by the hot fluid in the tank being at a higher temperature and therefor at a higher pressure pushing itself into the hot fluid distribution system. The temperature of the slug can be at a high enough temperature to create scalding problems.

Summary of the Invention

According to the invention, there is provided a system for distributing tempered fluid to a user. The system consists of a storage tank having heating means, outlet means for conveying heated fluid from the storage tank to a mixing chamber for distribution system on demand, cold fluid inlet means for replenishing the storage tank on demand, and a flow path between the cold fluid inlet and the mixing chamber. The ratio of cold fluid flowing between the flow path and the cold fluid inlet being controlled by a stepper motor, which is adjusted by the temperature setting of the distribution system by the consumer.

Preferably, a temperature sensor in the hot fluid distribution system will further close the cold fluid flow to the mixing chamber where hot fluid exiting the tank and into the mixing chamber for distribution is

RECTIFIED SHEET (RULE 91)

ISA/EP below the temperature set by the consumer.

Preferably, a temperature sensor in the hot fluid distribution system will allow maximum flow of cold fluid to the mixing chamber where hot fluid exiting the tank and into the mixing chamber for distribution is above scalding temperature as set by the consumer.

Preferably, a temperature sensor is located in the distribution system to actuate a safety valve to avoid the exiting of fluid above a desired maximum temperature into the distribution system.

The present invention further provides means to reduce the slug in the tempering system.

Brief Description of the Drawings In drawings which illustrate by way of example only a preferred embodiment of the present invention,

Figure 1A is a block diagram of one embodiment of the present invention;

Figure IB is a block diagram showing one of the alternate embodiment;

Figure 2A and Figure 2B are cross section of a 3-way valve; and

Figure 3 is schematic diagram illustrating the circuitry used in standard North American hot water tanks.

Detailed Description of the Invention

For illustration purposes, specific embodiments of the

RECTIFIEDSHEET(RULE91) ISA/EP invention will be described in association with a standard electrically heated domestic hot water delivery system having two immersed elements. Other modification of the invention for use with other types of hot water delivery system, such as one element tanks and commercial and industrial system for delivery of hot water or other types of heated fluid will be obvious to one skilled in the art.

As shown in Figure 1A and IB, a water storage tank 10 is provided with heating elements 12 and 14 located towards the bottom and top of the tank, respectively, and which are electrically operated in order to heat a body of water within tank 10. In standard North American water heaters, the circuit is designed to permit the heating elements to opperatein the alternative only, that is when one element is on, the other is off. As illustrated in Figure 3, this done by connecting the elements 12 and 14 to a common power source 40 with a double-throw or flip- flop relay 42.

In conventional constructions for domestic use, the tank 10 is encased in an insulating material 15, such as glass fibre, in order to prevent heat dissipation of the heated water within tank 10. For the purpose of the present invention, especially where for power demand control options a circuit interrupter, as illustrated in patent number PCT/CA93/00288, patented by the inventors, is connected to tank 10. A higher level of thermal insulation may be considered to reduce heat loss during peak energy demand periods.

As illustrated in Figure 1A the cold water supply is connected to stepper motor valve 16 which sets the ratio of water entering tank 10 through cold water inlet 18 and the flow path 20 which is in full communication with mixing chamber 22.

SUBSTITUTESHEET Mixing chamber 22 is in full communication with flow path 20, the hot water outlet 24 from tank 10 and hot water distribution system 26. As water is drawn from the hot water distribution system 26, hot water is drawn from hot water outlet 24 and cold water from the flow path 20. Thus, the flow of cold water from the flow path 20 and hot water from outlet 24 forces the hot water and cold water to mix within the mixing chamber 22 to form water at a lower temperature for distribution within the hot water distribution system.

The temperature of hot water required in the hot water distribution system controls the ratio of cold water supply 32 flowing in the flow path 20 and the cold water inlet 18. As the temperature of hot water at outlet 24 drops the ratio of cold water in the flow path 20 is reduced to compensate for drop in temperature at the hot water outlet, thus the temperature of water in the hot water distribution system is maintained at a constant temperature.

To maintain constant temperature in the hot water distribution system the ratio of cold water in the flow path 20 and the cold water inlet 18 is further adjusted by the temperature of cold water supply as sensed by sensor SI. This adjustment compensates for seasonal variation in the cold water supply and also for different geographical locations.

Further more as the temperature of hot water at outlet 24 drops below the preset temperature of the hot water distribution system, valve 16 stops the flow of cold water into flow path 20 and directs the cold water into the tank via cold water inlet 18. This gives the consumer extra hot water although at a lower temperature.

An exterior signal, such as a light (not shown) , could also be associated with temperature sensor S4 to SUBSTITUTESHEET indicate, by visual inspection, when the water in the storage tank or system is below scalding temperature.

As an additional safety feature to prevent scalding water from flowing into the hot water distribution system, an independent safety shut-off valve 25 is located in the hot water distribution system 26 after the mixing chamber 22.

The shut-off valve 25 can be a commercially sold valve from Memory Plumbing Products in Connecticut, U.S.A. sold under the trademark Shower Guard or a thermostat combined with a solenoid in a known manner for a safety shut-off valve.

When utilising a high temperature water storage system with a properly insulated storage tank, according to the invention, the energy required for re-heating the water in the storage tank can be greatly reduced. According to a further aspect of the present invention, the power supply demand for the heating means of the storage tank can be reduced significantly or completely during lengthy periods of time, such as daily peak energy consumption periods.

Figure IB illustrates an alternate embodiment wherein the stepper motor 16 is split into 2 separate valves 34 and 36. Valves 34 and 36 are 2-way valves which either let the water flow through at a given ratio or stop the flow completely. The 2 separate valves gives the system better control over the varying pressure in cold water supply 32 as cold water appliances, such as garden hose and the like are used and also the varying pressure within tank 10 as the temperature of water changes over time. Pressure within tank 10 increases with increase in water temperature and decreases as the water temperature drops.

As illustrated in Figure 2A and 2B, cold water supply is

SUBSTITUTE SHEET connected to Port 58. Port 54 is in full communication with flow path 20 and Port 56 is in full communication with cold water inlet 18. Piston 52 is adjustable to let the cold water flow from Port 58 to Port 54 and/or Port 56. Thus, the ratio of cold water from the cold water supply 32 is adjustable either to flow into flow path 20 and/or cold water inlet 18.

Cold water supply 32 flowing from Port 58 and into Port 54 will reduce the temperature of hot water distribution 26 while cold water supply 32 flowing into Port 56 will increase the temperature of hot water distribution system 26. Thus, the position of piston 52, which is controlled by a stepper motor, sets the temperature of water in the hot water distribution system 26.

Slug is created within the mixing chamber 22 when the user closes tap 38 within the hot water distribution system 26, so when the tap 38 is opened, next time, slug will flow through and cause scalding problems to the user.

Closing of tap 38 causes the temperature in the mixing chamber 22 to increase due to hot water under pressure within tank 10 being pushed out into mixing chamber 22 which is at lower temperature and therefor at a lower pressure. The hot water, under pressure, also floods flow path 20, which is at cold water temperature typically 10 degree C, and thus increasing the amount of slug to be dissipated.

To prevent this hazard a back flow valve (or some times cold the "one-way" valve) 28, sold commercially by Honeywell as part number BF290ANU, is inserted within the flow path 20 to prevent the flooding of the flow path 20 by the hot water exiting the hot water outlet 24. Thus the size of the slug is reduced by preventing the hot from expanding into flow path 20.

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ISA/EP The temperature of the slug is further reduced by closing valve 30 when ever the temperature of the mixing chamber gets over a fixed setting. Thus hot water is prevented from flowing into the mixing chamber 22 and thereby raising the temperature of water to be distributed.

Further more the rising temperature within the mixing chamber 22 also changes the setting of valve 16 to supply maximum flow of cold water to mixing chamber 22 and thereby having the ability to reduce the temperature of the slug within mixing chamber 22 as soon as tap 38 is opened by the user.

The oppeningof the tap 38, by the user, cause the cold water to flow into the hot water distribution system 26. When the temperature sensed by sensor S3 in hot water distribution system 26 is equal to sensor S2 in the flow path 20 and sensor SI in the cold water supply 32, all the valves are returned to operating positions to start supplying water at the preset hot water distribution temperature.

Valve 30 at the hot water outlet, when closed, also acts as a heat trap to prevent loss of heat from within tank 10.

The temperature of hot water distribution system 26 and other parameters such as maximum temperature of cold water supply 32, the maximum temperature of water within tank 10 and the like can be programmed into the system either remotely or by a keypad (not shown) , either by the user or the electrical utility company.

A preferred embodiment of the invention having thus been described by way of example only, it will be apparent to those skilled in the art that modifications and adaptations may be made without departing from the scope of invention, as set out in the appended claims.

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ISA/EP

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH A EXCLUSIVE PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A fluid tempering system, comprising: a storage tank having heating means; outlet means for conveying heated fluid form the storage tank; cold fluid inlet means for replenishing the storage tank on demand; control means for establishing a flow path between the said cold fluid inlet and said hot fluid outlet; and the arrangement being such that cold fluid flowing to the said cold fluid inlet is divided between the said flow path and said cold fluid inlet in a variable ratio whereby fluid flowing in the hot fluid distribution system, on demand, is colder than the fluid passing through the hot fluid outlet.

2. The fluid tempering system of claim 1 wherein the ratio between the said flow path and said cold fluid inlet is controlled by a 3-way valve.

3. The fluid tempering system of claim 1 wherein the ratio between the said flow path and said cold fluid inlet is controlled by 2 separate 2-way valves.

4. The fluid tempering system of claim 1 wherein the ratio between the said flow path and said cold fluid inlet is adjusted by the temperature of the fluid flowing in the hot fluid distribution system.

5. The fluid tempering system of claim 4 wherein the temperature of the fluid within the hot fluid distribution system is programmable.

6. The fluid tempering system of claim 1 wherein the ratio between the said flow path and said cold fluid inlet is further adjusted by the temperature of the fluid

SUBSTITUTESHEET flowing at the said hot fluid outlet.

7. The fluid tempering system of claim 1 wherein the ratio between the said flow path and said cold fluid inlet is further adjusted by the temperature of the said cold fluid supply.

8. The fluid tempering system of claim 1 wherein the temperature of the fluid within the hot fluid tank is programable.

9. The fluid tempering system of claim 1 wherein the memory means records the temperature readings from the temperature sensors, and an average of such data over a preset period of time is used to change variable stored limits in the memory means.

10. The fluid tempering system of claim 1 wherein the system is programmable.

11. The fluid tempering system of claim 10 in which the system is remotely programmable.

12. The fluid tempering system of claim 10 in which the system is programmable using a removable keypad.

13. A slug preventing system, comprising: a storage tank having heating means; outlet means for conveying heated fluid form the storage tank; cold fluid inlet means for replenishing the storage tank on demand; control means for establishing a flow path between the said cold fluid inlet and said hot fluid outlet; a valve within the flow path wherein the cold fluid can flow towards the mixing chamber; and a valve between the hot fluid outlet and the mixing chamber ;

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ISA/EP wherein the valve in the flow path prevents the hot fluid from flooding the flow path and the valve at the hot fluid outlet closes when the fluid in the mixing chamber gets above the preset temperature of the hot fluid distribution system.

SUBSTITUTESHEET