GB2181525A - Water heating apparatus - Google Patents

Abstract

An expansion chamber 36 is provided in communication with secondary water in a coil 34 which is located in a tank 10 of hot primary water to be heated thereby. The expansion chamber may be elongate as shown or spherical and located inside or outside the tank either between two horizontal or vertical coil sections 38, 40 of the coil 34 or connected to the inlet to the coil 34. The outlet 42 admitting water to the elongate chamber 36 is above the level of the end 44 of pipe 46 leading water out of the chamber. The feedwater 18 and overflow 24 connections between cold water feeder tank 14 and hot water tank 10 each include U-bends, ie 22 and 28 respectively. <IMAGE>

Description

SPECIFICATION Water heating apparatus This invention relates to water heating apparatus, and in particular is concerned with improvements in the water heating apparatus disclosed in ourco pending British Patent Application No. 2153504 in which there is disclosed water heating apparatus of the type (referred to as heating apparatus of the type set forth) having a tank which acts as a thermal store fora body of primary water which is or can beselectively circulated around a flow heating circuit, such as a small bore central heating system in a domestic dwelling.The heat is added to the body ofthe primary water in the tank by any appropriate heating means, which may be either inside the tank but preferablywill be external ofthetankandwill bea boiler or solar heating means through which the primary water from the tank is circulated and by which the primary water is heated.

Reference is made in the above to "primary" water because the present invention concerns heating apparatus ofthetype setforth having a secondary water circuit, and that secondary water circuit inclu des a heat exchange coil means which is insidethe thermal store tank. The secondary water passes through the coil means and receives heat from the heated primarywaterin thetankwhich surrounds the coil, and the heated secondarywaterwhich issues from the coils isforconsumption i.e. atdomestic watertaps, washing machines, or for general purposes.

As explained in said co-pending application, the invention disclosed therein is concerned with taking account of thermal expansion of the water in the secondary circuit, and in accordance with the invention the subject of the said co-pending application, there is provided in a heating apparatus ofthetypeset forth a thermal expansion chamber comprising a closed housing in hydraulic connection with the sec ondary water circuit.

By the said invention, thermal expansion can be readily accommodated in view of the fact that only a relatively small volume of secondary water is subjected to the heating in the thermal storage tank, and therefore only a small amount ofthermal expansion need be accommodated.

The present invention is concerned with various inventive designs of the secondary coil means and expansion chamber as disclosed in the accompanying drawings of which the five Figures 1 to 5 respectively show five embodiments of secondary coil means and expansion chamber arrangements.

In each ofthe Figures, the tankforthe body of primary water is shown but omitted are the primary water connections and the heating means; reference is made to said co-pending application for details of the omitted items.

Referring to the drawings, in each Figure is shown a hotwatertank 10 which may be ofcopperorthe like, and the tank is surrounded by insulation 12. A feedertank 14 is mounted on top ofthetank 10, and the supply of cold waterto the feeder tank 14 is controlled by means ofafloatvalve 16. Coldwaterflows from the tank 14through feed pipe 18 extending through the insulation 12 as shown, and terminating in an outlet 20 at the base of the tank 10. The feed pipe 18 is provided with a U-bend 22 at the lower end thereof.

From the upper end of tank 10an overflow pipe 24 extends backintothetank 14through an outlet 26 which is in the upper half oftank 14. Pipe 24 has an elevated U-bend portion 28.

The water in tank 10 is heated by means of a boiler orthe like (not shown) butofwhich details are given in said co-pending application 2153504, and in addition the hotwaterfrom the tank 10 is drawn through a closed circuit, for example a domestic heating circuit containing radiators, and is returned to thetank 10.

Again, connections illustrating this circuit are dis closed in the said co-pending application.

In each of the Figures of the accompanying drawings, there is disclosed a secondarywatercir- cuit comprising an inlet pipe 30 through which mains cold water is supplied, and an outlet pipe 32 from which heated water is supplied to consumer points such as domestictaps ora domesticwashing machine.

The cold water supplied through pipe 30 receives its heat by passing through heating coil means 34 in side thetank 10 and immersed in the hotwater therein.

The structure as above described is disclosed in said co-pending application to which reference is made.

Also disclosed generally in said co-pending application is an expansion chamber (reference 47 in said copending application) designed to accommodate thermal expansion of the secondary water in the heat exchange coil means 34. The present invention is concerned with specific designs for the said expansion chamber and coil means arrangement to provide effective design and construction.

In the arrangement of Figure 1, the expansion chamber comprises an elongated closed tubular body 36, and the heating coil means 34 is in the form oftwo coil sections 38 and 40 comprising helical coils arranged with their axes horizontal. The outlet end of coil section 38 indicated by numeral 40 leads into the lower end ofthe closed tube 36, and the outlet 42 thereof is located above an inlet 44 of the pipe 46 leading to the inlet end of coil 40. Pipe 46 extends into and along the tubular body 36 with a lower end 44 nearthe lower end ofthe body 46. This arrangement provides a structurally desirable layoutforac- commodation insidethe body 10, and provides for effective heat exchange. It is to be noted that the pipe 30 extendsthroughthe insulation l2beforeemer- ging atthe lower end ofthe body 10to meetthecoil section 38.

In normal operation ofthe arrangement described in Figure 1,the secondary water level in the tube 36 will be above the outlet 42 buta quantity ofairwill be trapped in the top end ofthetube 36. In the event of thermal expansion ofthe secondary water in coil sec tions 38 and 40 taking place, the level of water in tube 36 will rise compressing the trapped air until equilibrium is reached. The volume ofthe tube 36 will be designed to accommodate the maximum anticipated thermal expansion ofthe secondary water.

In the arrangement of Figure 2, again a closed tubular body 36 is employed, and this body is located insidethetank10similartothearrangementof Figure 1. Howeverthe pipe 30 leads into the lower end of the body 36 and its outlet 50 is at the lower end ofthe body 36. The heat exchange coil means 34 which may be in a single coil or in spaced coil sections as described in said co-pending application has its coils arranged so that the axis of the heat exchanger is vertical, and has its lower end coupled to an inlet 52 which is adjacent the outlet 50 inside the closed expansion tube 36.

In the arrangement shown in Figure 3, the expan- sion chamber is spherical and is indicated by numeral 54, and the expansion chamber 54 is located inside the tank 10 and is coupled between two sections 56 and 58 ofthe heat exchange coil means 34. The sections 56 and 58 are arranged with their axes vertical in thetank 10, and infactthespherical expansion chamber 54 may be arranged centrally ofthetank with the heat exchange coils 56 and 58 coiled therearound.

In the arrangement shown in Figure 4, the coil sections 60 and 62 arranged insidethe tank 10 are arranged with their axes horizontal and are coupled by a pipe section 64. The expansion chamber 36 is located outside the tank 10 as shown, but otherwise the expansion chamber and connections thereto are sim ilartothearrangementshown in Figure 2.

In the arrangement shown in Figure 5, the heat exchange coil sections 66 and 68 are arranged similar to the arrangement of Figure 4, and the expansion chamber 70 is spherical but is arranged outside the tank as shown. The outlet from the expansion chamber 70, pipe 72, passes through the insulation 12 as shown to connectatthe lower end ofthetank with the heat exchange coil section 66.

Each ofthe expansion chamber and heat exchange coil means arrangements described in Figures 1 to 5 provides particular advantages of operation of the general concept disclosed in the said co-pending application.

The arrangements described also possess additional advantages in the design ofthefeed andover- flowpipes 18 and 24 asfollows.

The provision of the U-bend 22 in the feed pipe 28 prevents what is known as one pipe circulation i.e.

hot water rising up the pipe and cold waterfalling through the same pipe, which could result in the transferrance of heat from the tank 10 to the feed tank 14. This is important in this application because of the high operational temperatures ofthe tank 10. The tank 14 is an open top tank, and if the water in this tank becomes hot, evaporation will take place resulting in a loss of water. A loss of water means frequent replenishment of the water in tank 10, which leads to increasing ofthe free oxygen in the water, which in turn can lead to rusting in the primary water circuit.

Anotherfeaturetherefore which has been embodied in the apparatus described isthatthe insulation 12 is encased in a steel casing, and the watertank 14 is mounted on the casing and isthermallyinsula- tedfrom thetank 10. The numberof copper pipe con- nections required has been kept to a minimum, thereby to minimise heat loss by conduction.

Alsowithaviewtominimising heatingofthetank 14, it should be observed that the overflow pipe 24 passes horizontally through the insulation 12 atthe top of tank 10, and is provided with the elevated Ubend 28, to increase the head of the overflow pipe, making it more difficult forwaterto flow from the tank 10 through the overflow pipe back into the headertank. It is found that with the switching on and off ofthe pump in the primary circuit, water surges in the tankcantake place, and such surges were leading to the charging ofthe hot waterth rough pipe 24 into the tank 14.

These combined modifications have been con ceived dueto thefactthatthe particularform of apparatus to which the invention relates, being novel in concept, operates at much highertemperatures than conventional hot water tanks, and therefore in the context of th is field these combined modifications represent a considerable step forward in the art.

Claims (11)

1. Water heating apparatus of the type set forth comprising an expansion chamber in contact with the secondary water circu it, said expansion chamber comprising an elongated enclosure located inside the tank between respective coil sections being an inlet coil section and an outlet coil section ofthe heat exchanger, the outlet end ofthe inlet coil section being a type which extends upwardly into the expansion chamberto a level which is above the level from which an outlet pipe extends from the expansion chamberto the inlet of the outlet heat exchanger section.

2. Water heating apparatus of the type setforth comprising an expansion chamber in communication with the secondary water circuit, said expansion chamber being connected to the inlet end of the heat exchanger coil.

3. Water heating apparatus according to Claim 2, wherein the expansion chamber comprises an elongated enclosure insidethetank.

4. Water heating apparatus according to Claim 2, wherein the expansion chamber is an elongated enclosure located outside the tank.

5. Water heating apparatus according to Claim 2, wherein the expansion chamber is a sphere located outside the tank.

6. Water heating apparatus of the type setforth and including an expansion chamber in communication with the secondary water circuit, said expansion chamber comprising a sphere.

7. Water heating apparatus according to Claim 6, wherein said sphere is connected intermediate inlet and outlet coil sections ofthe heat exchanger.

8. Water heating apparatus according to Claim 7, wherein the coils of the inlet and outlet heat exchanger sections are coiled round the sphere.

9. Water heating apparatus ofthetypesetforth including a feeder tank located above said tank, and including an overflow connecting the feedertankto the top of said tank, said overflow comprising a pipe which extends from the feeder tank and then up wardlyto define an inverted U before leading intothe top ofthe said tank.

10. Water heating apparatus according to Claim 9, including a feed pipe from the feeder tank into the bottom ofthe said tank, said feed pipe having a Ubend which lies below the inlet to the said tank.

11. Water heating apparatus of the type set forth and substantially as herein before described with referenceto Figure 1, Figure 2, Figure 3, Figure4or Figure 5 ofthe accompanying drawings.