WO2002050475A1

WO2002050475A1 - Method and means for pre-heating water

Info

Publication number: WO2002050475A1
Application number: PCT/GB2001/005745
Authority: WO
Inventors: Leslie Jessop
Original assignee: Leslie Jessop
Priority date: 2000-12-21
Filing date: 2001-12-21
Publication date: 2002-06-27
Also published as: AU2002216258A1; GB0031183D0

Abstract

A method and means for pre-heating mains cold water utilises a central heating system including a length of tubing (10) through which hot water is passing, a sleeve (12) surrounding the length of tubing (10) to define a sealed chamber (16) within the sleeve (12) between the length of tubing (10) and the sleeve (12), mains cold water being fed into the chamber (16) by way of an inlet (22), and withdrawn from the chamber (16) by way of an outlet (24), the withdrawn water having been pre-heated by heat exchange with the length of tubing (10) while in the chamber (16) for subsequent feeding to an electrical water-heating appliance such as a shower.

Description

METHOD AND MEANS FOR PRE-HEATING WATER

TECHNICAL FIELD

This invention relates to a method and means for preheating water, and has particular, though not exclusive, application to the pre-heating of mains cold water prior to being supplied to an electric shower.

BACKGROUND OF THE INVENTION

It is well established practice for domestic, and other, showers to be electrically powered and to provide instantaneous hot water from cold mains water supplied thereto.

In the United Kingdom as an example, there is a temperature difference in the cold mains water of about 15°C between winter and summer, the winter temperature being about 5°C and the summer temperature about 20°C.

Thus, in order to achieve comparable outputs from a shower using an instantaneous electric water heater supplied with mains cold water, it is necessary to increase the temperature of the water by an extra 15°C in winter compared with summer.

However, as the final temperature of the hot water from such a shower with a given electrical power input is controlled by adjusting the flow rate of the supply, it will be appreciated that, for a given output temperature, the flow rate in winter can be so low as to provide unsatisfactory performance from the shower.

There have been various proposals for pre-heating the incoming cold water supply prior to heating the water within the shower. For example GB 2160628A discloses a heat exchanger which uses heat from waster water from the shower to pre-heat incoming water prior to the waste water exiting to a drain.

However, the temperature of the waste water is itself relatively low, such that the temperature rise imparted to the mains water is correspondingly low.

GB 2200439 discloses an arrangement in which the mains cold water is pre-heated by hot water taken from a hot water cylinder. However, such cylinders are often situated a considerable distance away from the instantaneous electric shower, in which case expensive plumbing is reguired to effect connection.

SUMMARY OF THE INVENTION

According to one aspect of the present invention there is provided a method of pre-heating mains cold water utilising a central heating system including a length of tubing through which hot water is passing, the method being characterised by the steps of providing a sleeve to surround the length of tubing to define a heated chamber within the sleeve between the length of the tubing and the sleeve, feeding mains cold water into the chamber through an inlet to the chamber, withdrawing the water from the chamber through an outlet from the chamber, and feeding the withdrawn water to an electrical appliance for further heating therein.

Thus, it will be appreciated that heat from the central heating system is used to pre-heat cold mains water prior to the water entering, for example, an electric shower.

The incoming mains water is of course only pre-heated when the central heating system is operating. A central heating system is however usually set to operate in the winter when the mains water to the shower is at a lower temperature than in the summer, and the performance of the shower is therefore boosted at the appropriate time when the weather is cool whereby the shower has a similar performance in both summer and winter.

In a preferred method, the mains cold water is fed into the chamber at or adjacent one end of the sleeve and is withdrawn from the chamber at or adjacent the other end of the sleeve, the direction of flow of the mains water through the chamber conveniently being opposite to the direction of flow of hot water through the length of tubing.

Prior to activation of the electrical appliance to which the pre-heated mains water is fed, there may be a volume of mains water within the chamber that has been heated to a temperature above a desired value.

In a preferred method, therefore, pre-heated water withdrawn from the chamber and at a temperature above a desired value is mixed with cold mains water prior to being fed to the electrical appliance, and until the temperature of the pre-heated water falls to said predetermined value.

According to a further aspect of the present invention, there is provided means for pre-heating mains cold water utilising a central heating system, the means including a length of tubing within the central heating system through which hot water is passed, and being characterised by a sleeve surrounding the length of tubing to defined a sealed chamber within the sleeve between the length of tubing and the sleeve, an inlet to the chamber for feeding mains cold water into the chamber, and an outlet from the chamber for withdrawing the water from the chamber, whereby mains cold water is preheated in the chamber prior to being fed into an electrical appliance for further heating therein.

Preferably the inlet to the chamber is at or adjacent one end of the sleeve and the outlet from the chamber is at or adjacent the other end of the sleeve.

Conveniently the sleeve comprises a cylindrical member to surround the length of tubing and to define an annular chamber between the cylindrical member and the length of tubing, and a pair of end members closing the ends of the cylindrical member and through each of which passes the length of tubing in sealing relationship therewith.

In a preferred embodiment of the invention, the means includes a by-pass connection between the inlet and outlet of the chamber whereby mains cold water can flow directly between the inlet and the outlet, and a thermostatically controlled flow valve at or adjacent the outlet from the chamber and so arranged that, when the preheated water from the chamber exceeds a predetermined value, the valve opens to mix cold water from the by-pass connection with the preheated water, the valve closing when the temperature of the preheated water from the chamber has fallen to said predetermined value.

Preferably shut-off valves are incorporated in the flow path of mains cold water to and from the sleeve and to either side of the length of tubing whereby the sleeve and length of tubing can be removed, for example to remove scale deposits from within the sleeve and length of tubing.

Conveniently the sleeve, which may be of a synthetic polymeric material such as polyvinyl chloride, is encased in an insulating jacket.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 shows part of a domestic hot water system incorporating the means of the invention, and

Fig. 2 is a section through the sleeve and length of tubing of the means of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawings, Fig. 1 illustrates water flow within a typical domestic central heating system including a hot water cylinder 2, a radiator 4, piping 6 feeding from the cylinder 2 to the radiator 4, and piping 8 returning water from the radiator 4 to the cylinder 2. The piping 6 includes a straight length 10 conveniently located in or adjacent a bathroom containing an electrically powered shower (now shown) .

According to the invention, heat from the hot water passing through the length of piping 10 is used to preheat mains cold water being fed to the electric shower.

More particularly, a sleeve indicated generally at 12 encases the length 10, the sleeve 12 comprising a cylindrical portion 14 coaxially surrounding the length 10 to define an annular chamber 16 between the portion 14 and the length 10, and a pair of T-pieces 18, 20 one to each end of the portion 14 the legs of which respectively comprise an inlet 22 to the chamber 16 and an outlet 24 from the chamber 16, and the cross members of which are bored to seat over and surround the length of piping 10. The sleeve 12 is completed by a pair of opposed end pieces 26, 28 of annular cross section which also seal over and surround the length of piping 10 and which cooperate with the T-pieces 18, 20 to seal the ends of the sleeve 12. The components 14, 16, 18, 20, 26, 28 of the sleeve 12 may be screwed or otherwise connected together.

The supply of mains cold water to be fed to the electric shower flows through piping 30 which is connected to the inlet 22 to the chamber 16, while a further length of piping 32 connects the outlet 24 from the chamber 16 to the shower (not shown) .

Thus it will be appreciated that the arrangement so far described is such that, with the central heating operational and with hot water flowing through the piping 10, cold mains water flowing from the piping 30 through the inlet 22, through the chamber 16 and thence through the outlet 24 will be heated by heat exchange with the length of piping 10 whereby the water flowing to the shower through the piping 32 is warmer than that flowing through the piping 30. The materials, dimensions and flow rates are chosen such that the temperature rise between the inlet 22 and the outlet 24 is typically about 15°C. In order to maximise the temperature rise, the direction of flow of cold mains water through the chamber 16, as indicated by arrows 'C in Fig. 2, is opposite to that of the hot water through the length of piping 10 as indicated by arrows 'H' in Fig. 2.

Thus, the temperature of the mains water arriving at the shower in winter time when the central heating is on is about the same as that in the summer time when the central heating is off, and a hot, full-flow shower can be obtained even at winter temperatures.

If the central heating is on, and the shower is not operational, the mains water contained in the chamber 16 will be heated to a temperature close to that of the hot water in the length of piping 10. Thus, when the shower is first switched on, the mains water initially fed to the shower will be hotter than is required to provide a comfortable shower.

Accordingly, and in order to avoid this condition, the invention provides a by-pass connection 34 between the inlet 22 to the chamber 16 and the outlet 24 from the chamber 16 whereby cold mains water can flow directly from the inlet 22 to the outlet 24 as indicated by arrow 'BP' in Fig. 2. At the junction of the outlet 24, the connection 34 and the piping 32 there is provided a thermostatic control valve 36 which is so arranged that, when the temperature of the water from the chamber 16 at the outlet 24 exceeds a predetermined desired value, the valve 36 opens to allow cold mains water from the by-pass connection 34 to mix with the pre-heated water from the chamber 16 whereby the water flowing through piping 32 to the shower is at the desired value.

Once the temperature of the water from the chamber 16 at the outlet 24 has fallen to the predetermined desired value, the valve 36 closes to cut off the by-pass supply, and equilibrium conditions prevail .

Conveniently a plurality of shut-off valves 38 are provided, one at each end of the length of piping 10, and one in each of the pipings 30, 32 whereby the overall heat exchange assembly can be removed for the purpose of cleaning or replacement.

The described and illustrated heat exchange assembly can be constructed from a minimum number of components very cheaply and economically. The length of tubing 10 is ideally of copper as used in conventional central heating systems, while the sleeve 12 and associated components may be of a synthetic polymeric material such as polyvinyl chloride or other low conductivity material. Thermal efficiency can be increased by wrapping or otherwise enclosing the sleeve 12 in an insulating jacket.

Although described for use in conjunction with an electric shower, the apparatus of the invention could be used to pre-heat water supplied to other electrical appliances such as washing machines, dish washers, combination boilers and the like, which are themselves to heat water internally.

Other modifications and variations from the described and illustrated arrangements will be apparent to those skilled in the art.

Claims

1. A method of pre-heating mains cold water utilising a central heating system including a length of tubing (10) through which hot water is passing, the method being characterised by the steps of providing a sleeve (12) to surround the length of tubing (10) to define a sealed chamber (16) within the sleeve (12) between the length of tubing (10) and the sleeve (12), feeding mains cold water into the chamber (16) through an inlet (22) to the chamber (16) , withdrawing the water from the chamber (16) through an outlet (24) from the chamber (16) , and feeding the withdrawn water to an electrical appliance for further heating therein.

2. A method as claimed in claim 1 in which the mains cold water is fed into the chamber (16) at or adjacent one end of the sleeve (12) and is withdrawn from the chamber (16) at or adjacent the other end of the sleeve (12) .

3. A method as claimed in claim 2 in which the direction of flow of the mains water through the chamber (16) is opposite to the direction of flow of hot water through the length of tubing (10) .

4. A method as claimed in any one of claims 1 to 3 in which pre-heated water withdrawn from the chamber (16) and at a temperature above a desired value is mixed with cold mains water prior to being fed to the electrical appliance and until the temperature of the pre-heated water falls to said predetermined value.

5. Means for pre-heating mains cold water utilising a central heating system, the means including a length of tubing (10) within the central heating system through which hot water is passed, and being characterised by a sleeve (12) surrounding the length of tubing (10) to defined a sealed chamber (16) within the sleeve (12) between the length of tubing (10) and the sleeve (12) , an inlet (22) to the chamber (16) for feeding mains cold water into the chamber (16) and an outlet (24) from the chamber (16) for withdrawing the water from the chamber (16), whereby mains cold water is preheated in the chamber (16) prior to being fed into an electrical appliance for further heating therein.

6. Means as claimed in claim 5 in which the inlet (22) to the chamber (16) is at or adjacent one end of the sleeve (12), and the outlet (24) from the chamber (6) is at or adjacent the other end of the sleeve (12) .

7. Means as claimed in claim 6 in which the sleeve (12) comprises a cylindrical member (14) to surround the length of tubing (10) and to define an annular chamber (16) between the cylindrical member (14) and the length of tubing (10), and a pair of end members (26, 28) closing the ends of the cylindrical member (14) and through each of which passes the length of tubing (10) in sealing relationship therewith.

8. Means as claimed in any one of claims 5 to 7, and including a by-pass connection (34) between the inlet (22) and the outlet (24) of the chamber (16) whereby mains cold water can flow directly between the inlet (22) and the outlet (24), and a thermostatically controlled flow valve (36) at or adjacent the outlet (24) from the chamber (16) and so arranged that, when the preheated water from the chamber (16) exceeds a predetermined value, the valve (36) opens to mix cold water from the by-pass connection (34) with the preheated water, the valve (36) closing when the temperature of the preheated water from the chamber (16) has fallen to said predetermined value.

9. Means as claimed in any one of claims 5 to 7 wherein shut-off valves (38) are incorporated in the flow path of mains cold water to and from the sleeve (12) and to either side of the length of tubing (10) whereby the sleeve (12) and length of tubing (10) can be removed.

10. Means as claimed in any one of claims 5 to 9 in which the sleeve (12) is encased in an insulating jacket.