AU635027B2 - Improvements to hot water tanks and installations equipped with such tanks - Google Patents

Abstract

The invention concerns an installation for the distribution of hot water comprising a tank (1) fitted with a cold-water inlet pipe (2) emerging into the lower section, with a hot-water outlet pipe (3) opening into the top section and with a third pipe (9) opening at an intermediate level and intended for the heating and reheating of the tank, the said third pipe (9) being connected in series with the secondary (102) of a heat exchanger (10), the primary (101) of which is a heat source, and with a circulating pump (11) causing the water to circulate in the direction of the tank, the upstream end of this third pipe (9) being connected at (P) to the cold-water inlet pipe (2). <IMAGE>

Description

COMMONWEALTH OF AUSTRALIA 3 PATENTS ACT 1952-69 COMPLETE SPECIFICATION

(ORIGINAL)

Class Int. Class Application Number: Lodged: Complete Specification Lodged: *s*0

S.

S Priority 0 Related Art Accepted; Published: *..Name of Applicant: too* Address of Applicant: Actual Inventor fo e e 0 Address for Service CHAFFOTEAUX ET MAURY 2, rue Chaintron, 92120 Montrouge, France GILBERT NAUDET WATERMARK PATENT TRADEMARK ATTORNEYS.

LOCKED BAG NO, 5, HAWTHORN, VICTORIA 3122, AUSTRALIA Complete Specification for the invention entitled: IMPROVEMENTS TO HOT WATER TANKS AND INSTALLATIONS EQUIPPED WITH SUCH TANKS The following statement Is a full description of this invention, including the best method of performing it known to us us 1 Improvements to hot water tanks and installations equipped with such tanks The invention relates to hot water tanks, namely closed tanks adapted to contain, for the purpose of storing the corresponding heat, a pressurized mass of hot water intended more particularly for sanitary use, the volume of this mass generally being about 100 litres or so and its temperature being generally between 50 and 80 0

C.

It also relates to the installations equipped with coo. such tanks.

In known embodiments, the tanks of the kind in question are served by two tubes one of which, assigned to the intake and fed from a pressurized cold water network, opens into the low part whereas the other, assigned to drawing off and connected to at least one hot water distribution tap, opens into the top part.

Whenever the tap is opened, hot water is distributed drawn from the top part of the tank, the volume of water 20 drawn off being automatically compensated for by the intake of an equivalent volume of pressurized cold water in the low part of the tank.

The heat required for heating the water contained in the tank, at least for the greatest part thereof, is S. 25 generally brought by a closed independent water circuit comprising in series a coil immersed in the tank, a e circulating pump and a heat exchanger associated with a heat source such as the burner of a boiler.

The coil in question is relatively costly and the efficiency of the heat exchange which it makes possible is low.

To overcome these drawbacks, solar heating installations have been proposed equipped with a tank the above defined type, in which the coil immersed in the tank is omitted, the two ends of the heating piping which were previously connected to the two ends of this coil 2 openihg then directly into the tank.

This approach leads to a more favourable heat balance than the preceding ones.

But it again has the drawback of requiring the use of four separate connections passing sealingly through the wall of the tank for respectively the four tubes serving the tank for the cold water and the hot water.

The invention reduces this drawback by limiting the number of such connections to three.

10 For this, the tanks of the kind in question o o o according to the invention are further equipped with a tube, so-called cold water intake, opening into the low O part, a tube for drawing off hot water opening into the top part and a third heating and re-heating tube opening 15 into the tank lower than the drawing off tube, and they tee S are essentially characterized in that the total number of tubes serving the tank with water is equal to three.

As for the installations of the above kind, $see ec*. according to the invention, they are essentially 20 characterized in that the third tube is mounted in series to o with the secondary of a heat exchanger whose primary is a .".heat source and with a circulating pump causing the water to flow in the direction of the tank, the upstream end of this third tube being connected to the so-called cold o: 25 water intake tube.

In preferred embod i.laits, recourse is further had to one and/or other of the following arrangements a non return member is mounted on the section, of the so-called cold water intake tube, between the mouth of this tube in the tank and the point of connection to said tube at the upstream end of said third tube, in a direction such that this section can only have passing therethrough water leaving the tank; the heat exchanger whose secondary is mounted in series with the third tube is a high heat exchange capacity exchanger whose primary is itself connected to 3 the heat exchanger of a boiler and forming with the latter a closed circuit comprising a second circulating pump; thermostatic means are provided, responsive to the temperature of the water at a predetermined level of the tank, for controlling the energization of the two circulating pumps; the end of the third tube which opens into the tank is located at a vertical distance between 0 and 200 10 mm above the mean level of the mouth of the so-called cold water intake tube for a cylindrical tank whose diameter is between 400 and 500 mm; ooo• the end of the third tube which opens into the e e tank is stopped at the end and formed with lateral slits 15 whose width is greater than the mutual spacing.

000 0 Apart from these main arrangements, the invention comprises certain other arrangements which are preferably used at the same time and which will be more explicitly eeee discussed hereafter.

ergo 20 In what follows, preferred embodiments of the invention will be described with reference to the e* e accompanying drawings in a way which is of course in no wise limitative.

Figure 1 of these drawings shows very schematically a 25 a sanitary hot water supply installation comprising a tank and constructed in accordance with the invention, this installation being shown during a period of re-heating the tank without drawing off of water.

Figure 2 shows, similarly to figure i, a portion of the same installation, during drawing off of hot water without re-heating of the tank.

Figure 3 shows a detail of said tank.

In a way known per se, tank 1 is adapted so as to contain a mass of pressurized hot water while keeping the heat of this mass by means of an appropriate heat insulation, the volume of said mass being for example 4 about 100 litres.

The tank 1 is equipped with a first tube 2, called "cold water intake tube" (but not always serving for such intake, as will be explained further on) opening into its low part and a second tube 3 for drawing off water and opening into its top part.

The upstream end of tube 3 is connected to a drawing E off tap 6.

An aquastat 7 is also provided associated with a 10 user circuit 8 for controlling the heating of the water oS.. contained in the tank as soon as the temperature of this water at a predetermined level passes below a I* o predetermined threshold.

Furthermore, a third tube 9 is provided opening ito 15 the tank at an intermediate level thereof, but generally fairly close to the bottom of the tank; thus, this level is generally located at a vertical distance H between 0 and 200 mm above the mean level of the mouth of the socalled cold water intake tube 2, for a cylindrical tank 20 whose diameter is between 400 and 500 mm.

The continuous flow path defined partially by said tube 9 for the re-heating water of the tank passes successively through a heat exchanger 10, while forming by itself the secondary 102 of this exchanger, and a 25 circulating pump 11 connected so as to feed water towards the tank.

The upstream end of tube 9 is connected to tube 2 at a point P thereof which is located downstream of the safety unit 4, generally under the tank 1.

The heat exchanger 10 could be directly the heating element of a boiler, the primary of this exchanger then being formed by the different passages offered to the hot gases coming !from the combustion of an appropriate fuel.

In the preferred embodiment illustrated, this exchanger 10 is an exchanger with good heat efficiency whose primary l01 is mounted in series with the exchanger 5 12 of a boiler 13 such as the one which has just been defined and forms a closed circuit therewith and with a second circulating pump As for circuit 1, it forms advantageously the "short" loop of a mixed heating installation, namely adapted for providing both central heating by hot water flow through radiators and drawing off of sanitary water, the "long" loop 16 of thic installation, equipped with radiators 17, being mounted in parallel across loop 14 and 10 the switching from one of these two loops to the other being automatically controlled by a three-way valve 18.

.Operation of the installation described above is the S S. following.

On start-up, the temperature of the water contained 15 in the tank is cold, namely less than the reference temperature to which the user circuit 8 is set.

This circuit is therefore energized, which results in driving simultaneously the two pumps 11 and 15 while e.e. placing valve 18 in its position corresponding to "drawing 20 off", i.e. placing the "short loop" 14 in communication r with the exchanger 12 of the boiler.

Driving of pump 15 results in igniting the burner 19 of boiler 13, which heats the water in loop 14 as well as exchanger 25 Driving pump 11 results in causing the water to flow through the closed circuit comprising in series the tube 9 (and so said pump 11 and the secondary 102 of exchanger tie low portion of tank 1 and the downstream section of tubE namely the one between point P and the end of said tube opening into the tank, the word "downstream" being considered with respect to the direction of intake of the cold water into the tank following drawing off, as shown in figure 2, such as described hereafter.

The water in question is drawn off from the low coldest zone of tank i, then it is heated in exchanger and re-introduced thus re-heated into the tank from the 6 downstream end of tube 9.

Such operation under re-heating conditions of the tank continues until the temperature detected by the aquastat 7 reaches a given threshold and, from this time, the circuit 8 stops pump 11 as well as pump 15 if the latter is not otherwise in use.

Then, for drawing off hot water, it is sufficient to open tap 6.

As can be seen in figure 2, such water drawn off through tube 3 is immediately compensated for by the introduction of an identical volume of cold water at the base of the tank through tube 2.

The two ways of functioning which have just been described occur the most often at separate times, seeing 15 that, on the one hand, the respective durations of the drawing off and re-heating are in practice relatively short and do not overlap and, on the other hand, the volume of hot water permanently available in the top of the tank is generally sufficient to supply the different needs of the users of the installation with hot water.

But the two ways of functioning indicated corresponding respectively to drawing off hot water and re-heating the water in the tank, may be perfectly combined, the cold water supply for compensating the hot 25 water drawn off then being distributed between the two tubes 2 and 9 which are mounted in parallel from point P, with a relative proportion of the flows circulating in these two tubes which depends on the pressure of the cold water admitted, on the flow of hot water drawn off and on the power of the pump.

In a variant which may accelerate heating or reheating of the tank on the assumption of the abovementioned dual operation, the whole of the volume of cold water admitted into tank 1 from network 5 is forced through the exchanger 10 by rising in the "downstream t section of the above-defined tube 2, i.e. between point P 7 and the mouth of this tube in tank 1, a non-return member oriented so as to make the flow of water possible in said section only in the direction leaving the tank this member has been shown at 21 with a dash-dot line in figure 1.

This member may be placed on the mouth of tube 2.

Of course, in these cases, tube 2 does not serve for "the intake of cold water" into the tuhe and this is why this tube has been designated above by the expression "so- 10 called cold water intake tube".

To avoid as much as possible disturbing, by the intake of re-heated water into the tank, the thermal 000* ,stratification naturally created in the volume of water in this tank, the downstream end of tube 9 is advantageously o 15 adapted so that the water leaving through this end is distributed in horizontal directions as is shown by arrows G in figure 1.

For this, for example, said end is stopped axially and horizontal slits 29 are formed radially in its 20 sidewall, as can be seen in figure 3. These slits so advantageously have a width 1 greater than their mutual spacing e, so as to reduce the outgoing speed of the reheating water; the respective values of these two dimensions are for example 2 and 1.5 mm for a diameter of 25 tube 9 of about 15 to 18 mm.

A construction with horizontal slits may also be s s advantageously adopted at the end of tube 2 which opens into the tank this is what is shown by arrows F in figures 1 and 2. In such a case, the relation between the lengths and spacings of the slits is generally reversed with respect to that explained above.

Following which, and whatever the embodiment adopted, a hot water distribution installation with tank is finally obtained whose construction and operation follow sufficiently from what has gone before.

This installation has numerous advantages with 8 respect to those known heretofore and in particular the following the number of tubes serving the tank with water is reduced from four to three, which similarly reduces the number of sealed through passages in the wall (generally lower wall) of said tank for said tubes, the tank is without the usual coil, the overall thermal efficiency of the installation is excellent because a construction can be chosen for the heat exchanger with a very high heat efficiency, this e efficiency being appreciably greater than that of the heat 0@ exchange provided between the water of a tank and the S water which flows in a coil immersed in this tan thus, if we consider a hot water distribution installation S, 15 comprising a tank and a boiler, whose thermal power is about 22 kW, it is possible to recover a thermal power of about 15 kW with the above reuommended solution corresponding to a re-heating water flow rate between 500 and 800 1/h when pump 11 is energized whereas it is 20 difficult to recover more than 7 kW with prior known constructions.

As is evident, and as it follows moreover already from what has gone before, the invention is in no wise limited to those of its modes of application and S, 25 embodiments which have been more especially considered; it embraces, on the contrary, all variants thereof.

CC

Claims (4)

1. A hot water tank equipped with an intake tube opening into and out of a lower part of said tank, an outlet tube for drawing off hot water from a top part of said tank and a third heating tube opening into said tank lower than said outlet tube, said intake tube feeding into a heat exchanger whilst said heating tube carries heated water away from said heat exchanger and into said tank, said tank being characterised in that a cold water inlet is connected to said intake tube remote of said tank, and in that said heating tube is mounted in series with the secondary tube of a heat exchanger whose primary tubing is a heat source and with a circulating pump causing water to flow in the direction of said tank, the upstream end of this heating tube being connected to said intake tube, said tank being further characterised in that a non-return valve is mounted on said intake tube to prevent water flowing from said intake tube into said tank.

2. A hot water tank as claimed in claim 1 characterised in that for a cylindrical tank whose diameter is between 400 and 500 mm the end of said heating tube which opens into said tank is located at a vertical distance between i 0 and 200 mm above the mean level of the mouth of said intake tube.

3. A hot water tank as claimed in any one of claims 1 or 2 wherein the end of said heating tube has a termination formed with lateral slits or openings whose width is greater than the mutual spacing between said slits or openings. t,

4. A hot water distribution installation equipped with a tank according to any one of claims 1 to 3 characterised in that said heat exchanger whose secondary tube is mounted in series with said heating tube is an exchanger with high heat exchange capacity whose primary tube is itself connected to the heat exchanger of a boiler forming therewith a closed circuit, said circuit also including a circulating pump. A hot water distribution installation as claimed in claim 4 cnaracterised in that a thermcstat means is provided, for controlling the energisation of circulating pumps in response to the temperature of water in said tank said thermostat being located at a pre-determined level in said tank. Daiod this 13th day of January, 1993. CHAFFOTEAUX ET MAURY WATERMARK PATENT TRADEMARK ATTORNEYS THE ATRIUM 290 BURWOOD ROAD HAWTHORN VICTORIA 3122 AUSTRALIA AU5597090,WPC DOC016 o e S, S: 5e 9