GB2028986A

GB2028986A - Water heaters

Info

Publication number: GB2028986A
Application number: GB7929131A
Authority: GB
Original assignee: IMI RYCROFT Ltd
Current assignee: IMI RYCROFT Ltd
Priority date: 1978-08-22
Filing date: 1979-08-21
Publication date: 1980-03-12
Also published as: GB2028986B

Abstract

A hot water generator, suitable for example for supplying heated water to a hotel, comprises a heating compartment 12, a storage compartment 10 and a mixing compartment 11. Water is heated by heat transfer from steam as the water passes through a coil 15 in the heating compartment 12, and is then stored in the storage compartment 10. The steam input valve 16 is controlled in response to a thermostat 25, the element of which is subjected to a stream of water. This stream consists of mixed samples of cold feed water passing through a valve 28 and water taken directly after passing through the heating coil, via the pipe 27. The mixing compartment 11 may be below the heating compartment 12. <IMAGE>

Description

SPECIFICATION Hot water generator This invention relates to a hot water generator and more particularly to a hot water generator wherein a hot fluid, for example, steam or medium to high pressure hot water supplies the thermal input.

One of the problems of existing hot water generators is that their response to sudden demands for heated water can be unsatisfactory.

For example, at a peak hour in a residential institution such as a hotel, there may be a sudden and sustained demand for hot water. If the generator cannot respond rapidly enough, the storage capacity is quickly exhausted whilst the heat input to generator has barely had time to replenish the heated water which has been removed. The user will then experience a fall in the temperature of the water supplied to him.

It is one of the objects of the invention to provide a hot water generator which is capable of responding rapidly to a sudden demand for heated water.

According to the invention we provide a hot water generator in which the heat input is controlled by a thermostat, said thermostat being operable in response to changes in the temperature of a mixture of samples respectively supplied from the water to be heated and from the heated water.

According a preferred aspect of the invention, a hot water generator comprises a heating compartment having heating fluid entry and exit means and through which passes a conduit for water to be heated, a heated water storage compartment, from which the heated water can pass into a secondary circuit, and a mixing compartment having an inlet for cold feed water to be heated and an inlet for water returned from the secondary circuit, there being connections respectively for conveying mixed water from the mixing compartment into the heating conduit, and for conveying heated water from said conduit into the storage compartment,-and thermostat operable control means for controlling the thermal input to the heating compartment in response to the change in temperature of a mixture of water samples respectively supplied from the cold feed and from the heated water prior to its entry to the storage compartment.

The heating fluid may suitably be steam, and a distributor manifold for the steam may be provided within the heating compartment.

The storage compartment is preferably mounted above the other two compartments. The mixing compartment is preferably intermediate the storage compartment and the heating compdrtment The heating compartment may be made of steel with the mixing and storage compartments mounted above it being both made in copper.

The thermostat may have an element which is positioned in the storage compartment, the element having a shroud around it, through which passes the mixture of water samples thereby affecting the response of the theremostat. The element may have a portion which is unshrouded and extends into the heated water which in use is contained in the storage compartment.

A pump may be employed to continuously supply a water sample to the thermostat element from the heated water prior to its entry to the storage compartment. The pump may also draw water from the cold feed through an orifice or needle valve. The orifice or needle valve is preferably adapted to provide an increased cold feed sample in response to an increase in the cold feed flow rate into the mixing compartment, which increase results from an increase in the rate of water consumption in the secondary circuit.

Two embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 illustrates diagramatically a first hot water generator according to the invention, and Figure 2 illustrates diagramatically a second hot water generator according to the invention.

Figure 1 shows a hot water generator comprising a vertical cylindrical body having three compartments. The uppermost compartment 10 provides storage for heated water prior to its circulation in the secondary circuit; the intermediate compartment 11 is a mixing compartment for mixing cold feed water prior to heating with water returning from the secondary circuit; and the lowermost compartment 12 has means for heating the water prior to storage. The generator is supported on iegs 13.

Water to be heated passes from the mixing compartment 11, through a pipe 14 and into a heating coil or coils 1 5 extending within the lowermost or heating compartment 12. Heating is carried out by heat transfer through the wall of the heating coil 1 5 from steam entering the heating compartment via control valve 16, pipe 17 and steam distributor manifold 1 8. The condensate collecting in the base of the heating compartment is removed via a condensate outlet pipe 19.

Water heated in coil 1 5 leaves the heating compartment 12 2 towards its upper end, and rises through a pipe 20 to a point near the top of the generator when it enters the storage compartment 10. The secondary circuit, from which the user draws heated water, leaves the storage compartment 10 at its uppermost point via pipe 21, returning at the end of the circuit into the base of the mixing compartment 11. Potential use points in the secondary circuit are represented by valves 22.Water from the mixing compartment 11 is prevented from being drawn into the return of the secondary circuit by a non-return valve 23 in line 21 adjacent the mixing compartment 1 A circulation pump 24 is usually included in the secondary circuit to maintain the temperature in the secondary circuit pipework high enough for immediate consumption by the user.

A shrouded thermostatic element 25 projects through the side of the storage compartment 10.

A pump 26 continuously draws a sample of heated water through line 27 which is connected to pipe 20 before it enters the storage compartment 10. This sample is therefore drawn from water immediately after it leaves the heating coil 1 5. In addition, the pump 26 draws a sample of cold feed water via a needle valve or orifice 28 from the cold feed inlet pipe 29 before it enters the mixing compartment 11. Only a relatively small sample from the cold feed passes through the needle valve 28 relative to the sample from the heated water, but the pipework and valves are arranged so that the pump 26 draws a larger sample of cold feed when the cold feed flow rate through inlet pipe 29 increases due to an increase in demand from the secondary circuit.

Both samples drawn by pump 26 are passed as a single continuous stream over the shrouded element 25 and into the storage compartment 1 0.

The tip of element 25 projects out of the shroud into the water in the storage compartment 1 0, so that whilst the thermostat normally responds to the temperature of the stream passing through the shroud, if pump 26 fails it will respond to the temperature of water in the storage compartment 1 0. The thermostat operates in response to changes in the temperature of the mixed samples passed over element 25 to open and close the steam control valve 1 6.

As soon as heated water is drawn from the secondary circuit by the opening of valves 22, cold feed water is drawn into the mixing compartment 11. The cold feed sample drawn by pump 26 is increased, and the element 25 responds to the resulting temperature drop in the water passed through the shroud by opening the steam valve 1 6. The response of the generator to the drawing off of heated water is thereby extremely rapid, since it does not wait for the temperature of water in the storage compartment or another part of the circuit to drop before commencing heating the water in coil 1 5.

Another feature of the generator is that the sample of heated water which is fed to thermostat 25 by pump 26, is taken directly after the heated water leaves the coil 15. If heated water suddenly ceases to be drawn from the secondary circuit, the flow of water through coil 1 5 will drop sharply, thereby rapidly increasing the temperature of the water leaving the heating compartment 12. By means of sampling at this point the thermostat 25 can respond rapidly to the termination of demand in the secondary circuit, and partially close or stop the supply of steam through control valve 1 6.

A similar generator, with its features indicated by the same numerals as in Figure 1, is shown in Figure 2. The positions of the mixing compartment 11 and heating compartment 1 2 have, however, been reversed.

The heating compartment 12 of both embodiments is suitably made of steel, whilst the two other compartments, the interconnecting pipes and the coil 1 5 are made of copper. The embodiment of Figure 1 has constructional advantages over that shown in Figure 2, in that the two upper compartments can be made as an integral copper unit having a copper base. This copper case can then be mounted above the steel heating compartment. The steam is thereby retained in a steel shell, ensuring the safety and durability of the generator, whilst the copper compartments need only to be of sufficient wall thickness to contain the water pressure.

Claims

1. A hot water generator in which the heating input is controlled by a thermostat, such thermostat being operable in response to changes in the temperature of a mixture of samples respectively supplied from the water to be heated and from the heated water.

2. A hot water generator as claimed in Claim 1 comprising a heating compartment having heating fluid entry and exit means and through which passes a conduitforwater to be heated, a hot water storage compartment from which the heated water can pass into a secondary circuit, and a mixing compartment having an inlet for cold feed water to be heated and an inlet for water returned from the secondary circuit, there being connections respectively for conveying mixed water from the mixing compartment into the heating conduit, and for conveying heated water from said conduit into the storage compartment, and thermostatically operable control means for controlliny the thermal input to the heating compartment in response to the change in temperature of a mixture of water samples respectively supplied from the cold feed and from the heated water prior to its entry to the storage compartment.

3. A hot water generator as claimed in Claim 2 in which the heating fluid is steam and a distributor manifold for the steam is provided within the heating compartment.

4. A hot water generator as claimed in Claim 2 or Claim 3 in which the storage compartment is mounted above the mixing compartment and the heating compartment.

5. A hot water generator as claimed in Claim 4 in which the mixing compartment is positioned intermediate the storage compartment and the heating compartment.

6. A hot water generator as claimed in any of Claims 2 to 5 in which a thermostatic element is positioned in the storage compartment, the element having a shroud around it, through which the mixture of water samples can pass and thereby affect the response of the thermostat.

7. A hot water generator as claimed in Claim 6 in which the element has an unshrouded portion which extends into the heated water, which in use is contained in the storage compartment

8. A hot water generator as claimed in any of Claims 2 to 7 in which a pump is employed to continuously supply a water sample to the thermostatic element from the heated water prior to its entry into the storage compartment

9. A hot water generator as claimed in Claim 8 in which the pump is adapted to draw water from the cold feed through an orifice or needle valve.

10. A hot water generator as claimed in Claim 9 in which the orifice or needle valve is adapted to provide an increased cold feed sample response to an increase in the cold feed flow rate into the mixing compartment.

11. A hot water generator as hereinbefore described with reference to and as shown in either of the accompanying figures.