GB2136099A - Apparatus for heating water - Google Patents

Abstract

A water heating system comprises a tank 10 for containing primary water which is heated from a remote source 22. Inside the tank is a heat exchanger 28 through which mains water to be heated is passed, to provide hot, secondary water usable at the taps. The advantage of the arrangement is that the mains water can be at high pressure, and only a small volume is heated at any one time. The temperature of the water which is supplied to the taps is controlled by bleeding off cold water from the mains supply through connection 40 and mixing it with the hot water issuing from the heat exchanger in valve 36 which may be manual or automatic. <IMAGE>

Description

SPECIFICATION Apparatus for heating water This invention relates to an apparatus for and a method of heating water in domestic applications, and in particular is concerned with an apparatus for small, one person or starter homes which, because of size and/or effective thermal insulation, require only a small rating heater for heating not only the water for a primary hot water circuit, in particular a central heating circuit, but also the water for heating a secondary hot water circuit, in particular the hot water which dispensed from the domestic taps and which is used for washing and general purposes.

Known domestic apparatus for heating water is, compared to apparatus according to the present invention, rather expensive and complicated, and in terms of BTU output is usually much higher than that required for small, one person or starter homes, which apart from being small invariably are extremely well insulated, each of which features leads to a reduction in the demand of the heating system. The present invention provides a heating apparatus for use in the aforesaid homes which is simple in nature and relatively inexpensive.

According to the invention there is provided an apparatus for heating water comprising a storage tank for holding primary water for circulation through a flow heating system, means connecting or enabling the connection of a heating means to the tank for the heating of the water therein, a heat exchanger unit in the tank, said heat exchanger having an inlet for cold mains water and an outlet for heated, secondary water for general consumption and selectively operable mixing valve means coupling the said inlet and outlet for bleeding cold water from the inlet directly to the outlet for the selective control of the temperature of the heated secondary water.

The said mixing valve means may be thermostatically controlled so that more or less cold water is bled off to mix with the heated water automatically depending upon the temperature of the hot water.

The said heat exchanger may be in two sections connected in series, the respective sections being spaced vertically in the tank.

The closed heating system which is served by the tank may have an inlet to the tank towards the bottom thereof for return of the primary water from the heating system, the outlet to the heating system being located at the top of the tank.

The heating means may be a small, low rated heater, such as a 3 KW gas boiler connected to the tank to circulate the water in the tank through the boiler to heat same. Any type of heating means, remote from close to, or even in the tank may be used as convenient. Solar heating means may be used.

The primary water is preferably fed to the tank from a reservoir or feed tank, which feed tank also forms an expansion tank in that it receives overspill primary water from the main tank via an overspill pipe at the top of the main tank.

Instead of the feed and expansion tank being separate from the main tank, in an alternative embodiment, the main tank is designed to embody the feed and expansion tank.

The main tank preferably comprises a galvanised steel or copper outer case, lined with fibre glass insulation to the inside of which is an inner case which may also be of copper and in which the secondary water is contained.

Preferably the heating means is a boiler through which primary water from a tank is circulated to be heated, and will return from the flow circulation circuit is arranged in conjunction with the outflow to the boiler to provide increased gravitation of circulation flow of the body of water in the tank.

Specifically, the end of the circulation path inflow is in register with the boiler outflow, inside the tank, and at the bottom thereof, so that the returning flow of primary water. from the circulation path is directly into the boiler outflow and the said outflow is formed as a funnel into which the end of the return circulation path in the form of a pipe fits, so as to leave an annular induction area into which the water or the body of the water at the lower end of the storage tank is drawn, thereby increasing the circulation rate of the storage tank.

The invention also provides a method of providing domestic hot water and space heating, wherein a tank which forms a thermal store contains primary water, and that primary water is circulated around a space heating system, the water being heated by means of suitable heating means, and a heat exchange coil provided in the tank enables secondary water from the mains to pass through the heat exchange coils and after heating of same to consumption point such as domestic taps, and wherein the temperature of the secondary water flowing to the domestic taps is controlled by bleeding of cold mains water before it enters the heat exchange coils, and feeding same to mix with the secondary hot water issuing from the said coils.

Embodiments of the present invention will now be described, by way of example, with reference to the accompanying drawings, wherein: Fig. 1 is a sectional elevation of apparatus according to a first embodiment of the invention.

Fig. 2 is an elevation similar to Fig. 1, but showing another embodiment of the invention; and Figs. 3 and 4 show in diagrammatic form a modification which provides an improved performance.

Referring to the drawings, in Fig. 1 an apparatus for heating water is shown, and comprises an elongated, upright tank having a galvanised steel outer case 10, which is lined internally with fibre glass insulation 12, and there is an inner casing 14 of copper serving to contain a body of water 1 6 (primary water) which is the water used for the central heating system of the dwelling, the heating system being for example a small bore central heating system, with appropriate radiators and circulating pump. The outlet to the flow heating system is indicated by numeral 1 8, and is towards the top of the tank, whilst the return in the flow heating system is at the bottom of the tank and- is indicated by numeral 20.

The body of water 16 is heated off peak to approximately 800C at the top of the tank by a small rated heating unit 22, which may be for example a 3 KW gas boiler, located to the outside of the tank and having circulating pipe connections 24 and 26 for circulating the body of water 16 through the boiler 22. When the hot water from the tank is circulated to the central heating system, the radiators heat up quickly because of the maintenance of the high temperature of the water in the tank.

Inside the inner case 14 is a heat exchanger 28 which is in two coils, 28A in the lower portion of the tank, and 28B in the upper portion of the tank, the two coils being connected in series by pipe 30, which is partially embedded in the insulation 12 of the tank wall.

Cold water is supplied to the heat exchanger from a mains pipe 32, and the heated water (secondary water) from the upper coil 28 is delivered by a fali pipe 34 having an outlet 38 for hot water, and a bleed connection 40 by which incoming cold water may bleed from the pipe 32 directly into the mixing valve 36 to mix with the hot water coming from pipe 34 to provide, in pipe 38, hot water for general domestic use, of a temperature controlled by the setting of the thermostatic valve 36. The valve 36 may be operated manually, but can be arranged to operates automatically to ensure that the water flowing from pipe 38 is as near constant temperature as possible. This temperature would be selected so as to avoid scalding of the users of the hot water.

From the top of the tank is a vent pipe 42 which leads to a feed and expansion tank (not shown), and water from the feed and expansion tank is supplied to the lower end of the tank through an inlet 44.

The unit described is an integrated thermal storage unit in that it provides for heating of the primary water for the heating system (the body of water 16) and the heat in that body of water by heat exchange via the heat exchanger 28 serves to heat the secondry, domestic hot water which issues from outlet 38.

The unit may be designed to operate in that the boiler 22 serves to supply a constant but small heat input to the body of water 16, spread over a long period, rather than large heat input over short heating periods.

The arrangement illustrated in Fig. 2 is generally similar to that illustrated in Fig. 1, except that the feed and expansion tank 50 is embodied in the main tank, and the water inlet pipe 32 has a branch pipe 32A leading through a system ball valve 52 to the tank 50. An expansion tube 54 leads from the top of the main tank to allow for overspill of water back into the feed and expansion tank 50, and the said tank 50 finally has an overflow 54. The branch pipe 32A is embedded in the insulation 1 2 as shown in Fig. 2. This tank operates on exactly the same principle as the tank shown in Fig. 1, and no further description of the operatiqn is therefore given.

If desired, there may be a mixing valve, which is controllably thermostatically and automatically, between the outlet to the flow heating and the return from the flow heating, in order that returning water can be diverted to the outlet without passing through the tank.

The volume of the storage tank may be of the order of 25 to 60 gallons depending upon the application and location for the unit. It is envisaged for example that some units may be for location under work tops, in which case they will be rather squat, whilst others may be designed for location in cupboards, and require to be taller and narrower.

Referring now to Figs. 3 and 4, the basic arrangement previously described is shown, and thermal storage tank is indicated by a reference 100 and contains a body of water 110 to serve as a heat supply source,and coupled to the tank 100 is a boiler 12, which may be electrically operated or gas fired, or the like, the coupling being by means of an outflow pipe 160 connected to the lower end of the tank 100, and a return flow pipe 180 connected to the upper end of the tank 100.

Such an arrangement thus far described would operate on the simple gravity circulation of the hot water on the tank 100 in that as heat is applied to the circulating water via the boiler 120, the hot water rises and is inserted into the top end of the tank 100, and the water from the lower end of the tank is induced by gravitational conduction through the outflow 160 into the boiler 120.

To improve the performance of the boiler and storage tank arrangement described, it is preferable to increase the circulation rate if possible, but the normal method of doing this, i.e.

by using a pump, has shown itself to be too expensive as regards the specific systems in which we are interested.

The improvement of Figs. 3 and 4 provides a means whereby the gravitational induction effect can be increased when the hot water in the storage tank is used in a circulation user circuit, being for example a circuit of space heating radiators for a domestic dwelling, such a circuit being indicated in Fig. 3 by the outflow pipe 200 (with pump 210) and the return pipe 220, the pipe 200 being to the top of the tank 100 and the return pipe being to the bottom of the tank 100.

The increase gravitational effect is arranged by positioning the outlet 230 from the pipe 220 in register with the inlet end 250 of the pipe 160, which is formed as an enlarged funnel shaped mouth. As the water which is circulated through the circulation circuit 210, 222, is propelled by means of a circulating pump, when it is returned through the outlet pipe 220, it has a significant velocity and discharges straight into the funnel mouth 250, and this has the effect of inducing into the inflow pipe 160 water from the surrounding body of water as indicated by arrows 270 in Fig. 4, whereby forced induction circulation is established. Therefore, a higher circulating flow rate is achieved through the boiler 120, improving the performance of the system.It is the kinetic energy and pressure energy of the returning fluid from the circulating system which is utilised to achieve better circulation through the boiler. In previous systems, the said energy is simply dissipated by the random returning of the circulating flow to the tank 1 00.

Additionally, the pipe 180 may be arranged so that its end engages in a bell housing at the end of conduit 200 inside the tank 100, to provide a similar effect as that described and as exists between the pipe 220 and pipe 160.

A considerable advantage of the system is that when the circulating circuit is operational, force circulation through the boiler takes place, but when the circulating circuit is not operational, for example in summer months, the normal gravitational circulation of the water through the boiler still takes place.

The advantages of the apparatus according to the invention are that; (i) installation costs are reduced as the unit requires fewer components, less time to install and no special parts; (ii) running costs are reduced as the heat generator works more efficiently and the system losses are reduced; (iii) space is saved as the apparatus has fewer components and can be installed either on the ground or the first floor; (iv) the unit does not penetrate the loft space which reduces condensation risk; (v) it is easy to use as it has no complex controls; (vi) has the option for connection to direct mains which means that the secondary water can be at a high enough pressure to provided for example a powerful jet in a shower. This can be achieved without the need for non-return valves, temperature and pressure safety relief valves or expansion vessels in especially in view of the small amount of secondary water in the heating coils at any instant.

(vii) is flexible in use and may be used with room thermostats, simple time clocks, thermostatic radiator valves, TRV's and mixing valves, compensator, compensator plus TRV's and all other control systems; and (viii) the apparatus can have either a balanced or conventional flue.

Modifications may of course be made to the apparatus without departing from the invention.

Claims (8)

1. Apparatus for heating water comprising a storage tank for holding primary water for circulation through a flow heating system, means connecting or enabling the connection of a heating means to the tank for the heating of the water herein, heat exchanger unit in the tank, said heat exchanger having an inlet for cold mains water and an outlet for heated, secondary water for general consumption, and selectively operable mixing valve means coupling the said inlet and outlet for bleeding cold water from the inlet directly to the outlet for the selective control of the temperature of the heated secondary water.

2. Apparatus according to Claim 1, wherein the mixing valve means may be thermostatically or manually controlled so that more or less cold water is bled off to mix with the heated water automatically depending upon the temperature of the hot water.

3. Apparatus according to Claim 1 or Claim 2, wherein the heat exchanger is in two sections connected in series, the respective sections being spaced vertically in the tank.

4. Apparatus according to Claim 1, 2 or 3, wherein the heating means may be a small, low rated heater, such as a 3 KW gas boiler connected to the tank to circulate the water in the tank through the boiler to heat same.

5. Apparatus according to Claim 4, wherein the return flow from the flow heating system leads directly into the inlet of the connection to the boiler so that there will be an induced circulating effect in the tank.

6. An apparatus for heating water substantially as hereinbefore described with reference to the accompanying drawing.

7. A method of heating water wherein the heating means is a boiler through which primary water from a tank is circulated to be heated, and will return from the flow circulation circuit is arranged in conjunction with the outflow to the boiler to provide increased gravitation of circulation flow of the body of water in the tank.

8. A method of heating water substantially as hereinbefore described with reference to the accompanying drawings.