GB2530259A - Induction to heat thermal storage boilers, hot water cylinders and flow boilers - Google Patents

Abstract

A thermal storage boiler/combi boiler 1 or a domestic hot water cylinder la or flow boiler 2 is supplied with heat by an induction coil 3 that, by creating eddy currents in the metal wall of the store/cylinder/flow boiler, heats their fluid contents. As the induction coil/s are mounted on the outside of the store/cylinder/flow boiler it/they can be easily replaced or serviced without the need for time consuming cooling and draining down with attendant waste of heated water. As the induction coil's temperature typically only reaches ten to twenty degrees higher than the heated fluid the induction coil remains far cooler than would a resistance immersion heater which will 'burn out' over time.

Description

THIS INVENTION RELATES TO USE OF INDUCTION TO HEAT THERMAL

STORAGE BOILERS, HOT WATER CYLINDERS AND FLOW BOILERS It is known from Patent No GB 2266762 and Patent Application No GB 2423569 that thermal storage with heating means can be used together with a mains water heating heat exchanger as a mains water flow heating means can be used to improve the domestic hot water flow rate of a "combi" boiler. It is further known from Patent No GB 2266762 and Patent Application No GB 2423569 that thermal storage can be used to store intermittent energy input from, for example, off peak electricity supply, solar thermal, wind or photovoltaic generated electricity.

Thermal storage can be used as a buffer for air source heat pumps, CHP and similar devices to prevent short cycling wear and inefficiency. They also enable smaller heating units to be used so that the base loads can be met by the heat generator with the thermal store being additionally deployed to meet peak loads. This type of thermal storage boiler by its ability to accept intermittent heat input and store it until output is required (often at night when "green" inputs c.g. solar may havc ccascd) cnablcs and cncouragcs uptakc of"grccn" inputs from solar and other "responsible" sources, Thermal storage also helps electricity companies to "load level" and "load match" making more efficient use of generating and distribution plant.

In current forms that use intermittent off peak electricity the thermal store is heated with electricity using one or more resistance heated immersion heaters.

A disadvantage of immersion heaters is that a plurality is generally needed leading to a plurality of large tappings being required in the thermal store with an attendant increase in production cost and risk of leaks both from the joints at the tappings and from the immersion heaters themselves. They need replacing as their life is not long due to resistance element burn out'. To replace an immersion heater would be a fairly simple fast process but for the need to drain the large thermal store or a domestic hot water cylinder, This process of draining down and refilling the thermal store can take several hours, This can involve still longer delays if the store has to be cooled to a safe temperature before draining down can be carried out. This means that the simple replacement of a failed immersion heater component can take a long time and thus be extremely costly in labour.

Patent Application No GB 2423569 teaches that using a three port valve and pump on the return of the heating and domestic hot water heat exchanger circuit of a thermal storage combination boiler extends the life of the pump and motorised three port valve by subjecting them to the cooler return water. Because the three port valve and pump are both naturally and, without complex electronics, actuated for the provision of domestic hot water throughout the year, the build up of plated out detritus on the rubbing surfaces of the components that causes premature failure by seizure is prevented. Also the pump and three port valve location on the heating and domestic hot water return enables the flow to the heating to be taken from lower down the thermal store than the flow to the domestic hot water heat exchanger effectively leaving a reserve of thermal energy for domestic hot water production.

Flow boilcrs arc non storage electric boilers that have the advantage of being extremely cheap in manufacture compared to direct combustion boilers. However, as they have no thermal storage their heat output ceases the moment they are turned off. This makes them suitable solely for connection to the expensive peak rate twenty four hour electricity supply as connection to an intermptible off peak supply would leave the householder without heat shortly after the off peak supply is shut off. Flow boilers alone do not offer the load levelling and load predicting advantages to the generating companies that electric thermal storage boilers do and so are not suitable to be connected solely to an off peak supply and thus cannot fully benefit from its cheaper running cost.

The disadvantages of the above use of immersion heaters in thermal storage boilers/thermal storage combi boilers also occur in their use in heating domestic hot water in cylinders and in flow boilers.

A further disadvantage of utilising immersion heaters to heat thermal stores, flow boilers and domestic hot water cylinders or flow boilers is that immersion heaters use electrical resistance wires in their stmcture that reach high temperatures that shorten the life of the immersion heaters by burning out'.

Although some induction heated flow boilers are known, their induction coils are within the boiler or under the boiler and thus inaccessible or nearly inaccessible after manufacture and require the same cooling and draining mentioned above to gain access to the coil/s.

It is the object of the present invention to overcome the disadvantages of the prior art of immersion heaters being fitted directly into a thermal storage boiler/combi boiler or a domestic hot water cylinder or flow boilers and the disadvantages of induction coils fitted within a boiler.

According to one preferred form of the present invention there is provided a thermal storage boiler/combi boiler being provided as a heat store for the supply of primary hot water to a hcating or hcating and domcstic hot watcr systcm is providcd with at least one inductive heating means (known as an inductive coil) mounted on the outside of the water retaining wall in a proximity sufficiently close to the wall of the thermal store/domestic hot water cylinder to enable eddy currents created by the inductive heating means to heat the thermal store's metal wall which passes the heat so created to heat the store's enclosed water. The thermal storage boiler/combi boiler may optionally be fitted with provision to accept additional heat inputs from, for example, solar thermal panels.

In a further preferred form a domestic hot water storage cylinder is provided with at least one inductive heating means mounted on the outside of its fluid retaining wall in a proximity sufficiently close to the outside wall of the domestic hot water storage cylinder to enable eddy currents created within the metal wall of the domestic hot water cylinder to cause heating of the wall that is passed by conduction to its enclosed domestic water.

In a further preferred form a flow boiler is provided with at least one inductive heating means mounted in proximity sufficiently close to the outside wall of the said flow boiler to enable eddy currents created within the metal wail of the flow boiler to cause heating of its wall that is passed on by conduction to the enclosed heating circulating fluid.

Advantageously the said fluid retaining wall is fabricated from a ferromagnetic material that can produce strong eddy currents with attendant good heating of the wall's fabiic and to conduct such heat to the contained fluid.

Alternatively if the said fluid retaining wall is fonned from a non ferromagnetic material, such as copper, a ferromagnetic plate or other ferromagnetic surface may be thennal conductively interspersed between the inductive coil and the fluid retaining wall.

flow boilers utilising eternally mounted inductive heating means can be used as stand-alone boilers or usefully be linked to thermal storage boilers/combi boilers and offer the ability to service or replace their inductive heating coil/s without the time consuming need to drain down and waste expensively heated watcr. Boilers/combi boilers that use inductive heating means instead of resistance immersion heaters, have much longer lives because resistance immersion heaters having high operating temperatures have a much shorter life that cooler running induction coils.

Although the thermal store version of the present invention is described for clarity as having the controls, pump and three port motorised valve configured as in Patent Application No GB 2423569 to take advantage of the features of that Patent it should be understood that other control and flow boiler configurations can be substituted where circumstances dictate.

Although the present invention is described for clarity as an electric thermal storage combi boiler/boiler or a domestic hot water cylinder, or flow boiler, any other metal chamber containing fluid to be heated may take advantage of the utilisation at least one externally mounted inductive heating means to heat its contents.

Although the present invention is described as having an inductive heating means the term inductive heating means should be taken to mean any mostly inductive electrical heat producing means that can be fitted externally to a thermal storage combi boiler/boiler or a hot water storage cylinder or a flow boiler or other fluid containing chamber and by inducing eddy currents within their metal wall's structure cause the wall to heat and by conduction with their contents cause the contents to heat.

Expansion system, safety system, temperature control system, induction coil control system, heating circuit and filling means have been omitted for clarity.

The invention will now be described by example with reference to the following drawings wherein Drawing 1 is a diagrammatic illustration of the thermal storage combi boiler form of the present with at least one induction heating means mounted on the fluid retaining wall of the thermal store.

Drawing 2 is a diagrammatic representation of a further form of thermal storage combi boiler having its heat produced by a separate flow boiler said flow boiler being heated by at least one induction heating means mounted on the fluid retaining wall of the flow boiler.

Drawing 3 is a diagrammatic illustration of the domestic hot water cylinder form of the present invention being heated by at least one induction heating means mounted on the fluid retaining wall of the flow boiler.

Drawing 4 is a diagrammatic illustration of the flow boiler form of the present invention said flow boiler being heated by at least one induction heating means mounted on the fluid retaining wall of the flow boiler.

Referring firstly to Drawing 1 there is shown a thermal storage combi boiler system heated by induction coil heater/s 3 mounted on the fluid retaining wall of the store 1.

Referring now to Drawing 2 there is shown a thermal storage combi boiler system where the store is heated by a flow boiler 2 having induction coil heater/s 3 mounted on the fluid retaining walls of the flow boiler 2.

Referring now to Drawing 3 there is shown a domestic hot water cylinder la heated by induction coil heater/s 3 mounted on the fluid retaining wall of the cylinder la, Referring now to Drawing 4 there is shown a flow boiler heated by induction coil heater/s 3 mounted on the fluid retaining wall of the flow boiler.

As described earlier the induction coil heater/s 3 on control (not shown) demand causes eddy cuncnts induccd in thc fabric of thc fluid rctaining walls to hcat, hcating in turn by thcrmal conduction the fluid within.

The numbered items will be listed as a guide to the components of each drawing their functions being known.

I. Thermal store fluid container.

la. Domestic hot water cylinder.

2. Flow boiler fluid containing wall.

3. Inductive heating means.

4. Flow switch.

5. Domestic hot water heat exchanger.

6. Circulating pump.

7. 3 port control valve.

8. Heating circuit flow.

9. Heating circuit return.

10. Thermostatic mixing valve 11. Tempered water to taps 12. Cold water inlet 13. Flow out from flow boiler 14, Vent 15. Cylinder hot water to taps 16. Automatic by-pass valve 17. Return into flow boiler The thermal store 1, domestic hot water cylinder 2 and flow boiler 3 may be conveniently formed from ferrous metal, glass lined ferrous metal, suitable stainless steel or other metals or substances that can have eddy currents induced in it that creates sufficient heat, Suitable commercially available ferromagnetic stainless steel cylinders, thermal stores or fabricated flow boiler chambers may be used. None ferromagnetic cylinders may be utilised by using a fcrromagnctic platc or coating dcscribcd abovc. Thc inductivc coils may convcnicnfly bc as commercially available or custom fabricated to suit the specific needs of load, AC frequency, mounting wall curvature etc.