GB2130694A

GB2130694A - Improved domestic hot water circulation system

Info

Publication number: GB2130694A
Application number: GB08330518A
Authority: GB
Inventors: Henry John Firman
Original assignee: Individual
Current assignee: Individual
Priority date: 1982-11-17
Filing date: 1983-11-16
Publication date: 1984-06-06
Also published as: GB8330518D0

Abstract

An improved domestic hot water circulation system comprises a conventional circulation system having a series of room heating radiators connected to a gas fired boiler 20. Connected to the circulation system is a heat exchanger 16 to collect otherwise wasted heat from the boiler 20 and deliver it directly to the circulation system. Heat exchanger 16 is mounted remotely from the boiler to receive hot spent gas from it and is connected by pipes 30, 32 to the cold feed of the boiler. A thermostatically controlled hot feed through line 100 to the heat exchanger provides for rapid warm-up to reduce condensation on the heat exchanger. <IMAGE>

Description

SPECIFICATION Improved domestic hot water circulation system This invention relates to heating apparatus particularly, but not exclusively, applicable to domestic heating systems for dwelling houses, with application likewise to analogous heating systems such as those for greenhouses and the like.

In currently available domestic heating systems of the kind comprising a boiler or furnace with a heat circulation system such as radiators connected to the boiler by pipe-work through which heated liquid flows, or a ducted air heat circulation system, the problem arises that a large proportion of the heat generated by the boiler is discharged through the boiler flue without effecting any significant heating effect. It is believed that at least 30% of the heat generated by the boiler is lost in this way.

Many attempts have been made to effect heat conservation in domestic dwelling houses in recent years as a result of the increasing cost of fuels, but to the Applicant's knowledge no effective means has been devised for use in domestic heating systems which alleviates the problem of heat loss in the boiler exhaust gases, and an aim of the present invention is to provide heating apparatus offering improvements in relation to this problem, with possibly slightly wider application, but it is appreciated that many sophisticated heating systems have been devised over the years for use in industrial boilers and furnaces and the like but in view of the long felt want for improvements of the kind identified above in relation to domestic heating systems it is submitted that such industrial boilers and the like have no relevance to the present invention.

According to the invention there is provided heating apparatus comprising a primary heating system having an outlet for heated gas, a heat exchanger positioned in the path of said heated gas, and heat transfer means to transfer heat from the heat exchanger to the primary heating system.

Preferably, the primary heating system comprises a boiler or furnace. The boiler may be for use in a domestic dwelling house. The outlet of the primary heating system may be a flue or exhaust duct of the boiler or furnace.

Preferably, the heat exchanger is mounted in a housing having an inlet connected to or positioned to receive heated gas from the boiler exhaust duct.

An outlet of the housing may be directly connected to atmosphere -- this arrangement being particularly applicable to heating systems of the "balanced fiue" kind in which the flue passes through an opening in a wall of the dwelling house and an air inlet for the boiler surrounds or is adjacent to the flue. The heat exchanger may be mounted on an external wall of the house adjacent the outlet of the boiler flue.

Alternatively, the housing outlet may be connected to a continuation of the boiler flue or chimney.

The primary heating system may comprise a hot liquid circulation system and the heat exchanger may comprise liquid-filled tubes with end manifolds connected to said circulation system. The heat exchanger is preferably connected to the primary heating system on the upstream side of the boiler with respect to the direction of liquid flow around the circulation system. The inlet and outlet to the heat exchanger are preferably connected to the primary heating system with the heat exchanger inlet connection upstream of the heat exchanger outlet connection.

The inlet and outlet connections to the heat exchanger are preferably through a manifold at one end of the heat exchanger, an internal baffle being provided in said manifold between the inlet and outlet connections.

The housing of the heat exchanger is preferably insulated to reduce heat loss through the walls of the housing. Baffle means may be provided in the housing to spread the heated gas over the surfaces of the heat exchanger.

The invention also provides a method of heating comprising providing heating apparatus including a primary heating system having an outlet for heated gas, positioning a heat exchanger in the path of said heated gas, causing said heated gas to transfer heat to the heat exchanger, and providing heat transfer means to transfer the exchanged heat from the heat exchanger to the primary heating system.

An embodiment of the invention will now be described by way of example with reference to the accompanying drawings in which: Fig. 1 shows a circuit diagram for a primary heating system having a boiler with a heat exchanger positioned in the boiler flue; Fig. 2 shows a sectioned elevation view indicating, diagrammatically, the connection of the heat exchanger to the boiler exhaust flue through the wall of a domestic dwelling house having a balanced flue boiler exhaust system; Fig. 3 shows, on a larger scale, a vertical section through the heat exchanger assembly of Fig. 2, the direction of viewing being indicated by arrows Ill-Ill in Fig. 2; Fig. 4 shows an end elevation view of the heat exchanger assembly of Fig. 3, the direction of viewing being indicated by arrow IV in Fig. 3;; Fig. 5 shows, in a view corresponding to that of Fig. 3, a similar vertical section through a modified heat exchanger assembly in which the housing of the heat exchanger is directly connected to a boiler flue or chimney as opposed to atmosphere; Fig. 6 shows an end elevation view of the heat exchanger assembly of Fig. 5, the direction of viewing being indicated by arrow VI in Fig. 5: Fig. 7 shows a section on the line VIl-VIl in Fig. 5 through an inlet manifold of the heat exchanger, showing the water tube positions; the corresponding section through the manifold at the other end of the heat exchanger corresponds; Figs. 8 and 10 show, on an enlarged scale, a vertical section through the two end manifolds of the heat exchanger, that of Fig. 10 being the inlet manifold; and Fig. 9 shows an end elevation view on arrow IX in Fig. 5 of the end plate of the inlet manifold.

As shown in Fig. 1, heating apparatus 10 comprises a primary heating system 1 2 having an outlet 14 for heated gas, and a heat exchanger 1 6 being positioned in the path of the heated gas, with heat transfer means 18 being provided to transfer heat from the heat exchanger to the primary heating system.

Heating apparatus 10 is based upon a conventional domestic central heating system comprising a gas fired boiler 20 connected to a series of room heating radiators (not shown) and a coiled heating element in a hot water tank (also not shown). Pipework 22 connects boiler 20 to the radiators and the hot water tank.

The direction of flow of water through pipework 22 is indicated in Fig. 1 by arrows. The cold feed, or return, to the boiler is through a cold feed pipe 24 connected to the boiler water jacket near the bottom of the jacket. The hot feed pipe 26 delivers hot water from the boiler to the radiator system and heating element in the hot water tank.

Within boiler 20 a conventional gas burner system 21 delivers heat to the water jacket and waste gases from the burner system are delivered to atmosphere through a flue 28. Heat exchanger 16 is positioned at the end of flue 28 so as to receive the hot flue gases, which are then discharged to atmosphere.

Heat transfer means 1 8 comprises an inlet tube 30 and an outlet tube 32 connected to a multipletube water-filled assembly forming heat exchanger 1 6. Thus the heat exchanger is connected to primary heating system 1 2 on the upstream side of boiler 20 and the inlet tube 30 for the heat exchanger is connected to cold feed pipe 24 at an upstream position of the heat exchanger outlet tube 32.

The result of this arrangement is that heat extracted from the flue gases by heat exchanger 1 6 is transferred to the water within the heat exchanger water tubes and effects a pumping action causing cold water to be drawn into the heat exchanger and hot water to be delivered to the boiler cold feed pipe, whereby the cold feed to the boiler is raised in temperature.

Fig. 2 shows the general arrangement of the heat exchanger 1 6 in relation to the boiler flue 28 and the wall 34 of a domestic dwelling house.

Note that in Fig. 2, for simplicity, wall 34 is shown as a single solid structure, but of course in many cases in the UK it will be a double wall with a cavity (possibly containing insulating material) without in any way affecting the present invention.

In this embodiment of the invention the boiler flue arrangement is of the so-called "balanced flue" kind in which a combined inlet/outlet assembly is provided comprising flue 28 and an air inlet duct 38 through which combustion air is drawn to the boiler combustion chamber. The inlet air is drawn in at a location close to heat exchanger 1 6 without in any way affecting the performance thereof.

Heat exchanger 1 6 is mounted on a shelf 40 on external wall 34. The heat exchanger is mounted within an insulated housing 42 having gas outlets 44, 46 through which the flue gas is discharged to atmosphere after extraction of heat therefrom.

Heat exchanger 1 6 will now be described in more detail with reference to Figs. 3 onwards.

As shown in Fig. 3, heat exchanger assembly 1 6 comprises an inlet/outlet manifold 48 and an end manifold 50 connected by multiple water tubes 52. Fig. 10 shows inlet/outlet manifold 48 in more detail. Water enters through an inlet opening 54. A baffle 56 on manifold end plate 58 inhibits upward circulation of the water and the water proceeds through the lower assembly of water tubes 52 to end manifold 50 shown in Fig. 8 where the water proceeds upwards and enters the upper assembly of water tubes 52 and returns to manifold 48 in a heated condition and is discharged from the heat exchanger.

Manifolds 48, 50 have similar tube plates 60, 62 respectively to which the water tubes are secured in the positions indicated in Fig. 7. End manifold 50 has an end plate 64 corresponding to end plate 58. Sealing gaskets (not shown) are provided between the end plate and tube plate of each manifold and the assembly secured together by bolts (not shown). An outlet opening 66 in end plate 58 is connected to outlet tube 32 to complete the water flow circuit.

It should be noted that no pump is provided for the heat exchanger system as such. The latter system is connected in parallel with the primary system 12. The primary heating system itself may have a water circulating pump or may rely on gravity feed and convection.

-As shown in Fig. 3 housing 42 for heat exchanger 1 6 has an opening 68 connected to boiler flue 28 and exhaust gases therefrom pass outwards in the directions indicated by the arrows.

The housing itself is constructed of asbestos or any other suitable insulating material. Gas outlets 44 are formed at the top of the housing, one at each end, and an outlet baffle 70. is mounted above heat exchanger tubes 52 so as to promote the extraction of heat from the exhaust gas before discharge to atmosphere. The lower portion 72 of the housing 42 is double-walled or lined with insulation material to reduce heat loss.

In the embodiment of Fig. 5, the heat exchanger 1 6 is constructed as described above but the housing 74 therefor is modified somewhat so that the heat exchanger assembly can be incorporated in the flue system of an oil fired boiler which does not employ a balanced flue inlet/outlet assembly.

The housing inlet 76 is provided with a steel baffle plate 78 to disperse the flue gases over the heat exchanger tubes 52. The housing outlet 80 is directly connected to the remainder of the boiler flue for discharge upwards through a chimney assembly 82 or the like.

In use, boiler 20 operates in the usual way to heat the water flowing around primary heating system 12. Flue gases passing through the housing of heat exchanger 1 6 raise the temperature of water in tubes 52 thereby causing the heat exchanger system to exert a pumping effect drawing in cold water from cold feed pipe 24 through inlet tube 30 and discharging this water at a higher temperature through outlet tube 32 back into cold feed pipe 24, whereby the cold feed to the boiler is considerably raised in temperature.

In this way, a proportion of the heat otherwise discharged to atmosphere through the boiler flue is recaptured and fed into the heating system and usefully employed in heating the dwelling.

Among modifications which could be made in the above-described embodiments are modifications to the structure of the heat exchanger 1 6. For example, coiled tubes could be employed or a structure more analogous to that of the radiator of the cooling system of an internal combustion engine. The heat exchanger could be mounted in series with the cold feed pipe to the boiler, or even in series or in parallel with the hot feed outlet from the boiler, but neither of these arrangements is expected to be as efficient as that described above. A pump could be provided to circulate fluid through the heat exchanger. Many design modifications could be made to the housing for the heat exchanger for the purpose of improving heat transfer to the heat exchanger, including modified baffle arrangements.Likewise, modifications can be made for the purpose of improving the flow of flue gas through the housing and over the heat exchanger, for example by modified gas outlets and/or the provision of draught assistance means such as a fan.

While the invention has been described with particular reference to gas and oil-fired domestic heating systems, the invention is equally applicable to solid fuel systems in which there is a comparable loss of heat by virtue of the flue gases, and a heat exchanger in accordance with the present invention can be provided in such a heating system to advantage the arrangement being similar to that described above in relation to Fig. 5.

A further modification is illustrated in Fig. 1.

There is provided temperature-responsive means to cause rapid warm-up of heat exchanger 1 6. For this purpose, a pipe 100 is tapped into the hot feed pipe 26 to deliver hot water from boiler 20 through a thermostatically controiled valve 102 to heat exchanger 16 on initial start-up of the boiler.

Valve 102 closes once the heat exchanger has reached its normal operating temperature. This reduces condensation on the heat exchanger and improves efficiency. When valve 102 has closed under normal operating conditions, the system operates exactly as described above.

Claims

1. Heating apparatus comprising a primary heating system having an outlet for heated gas, a heat exchanger positioned in the path of said heated gas, and heat transfer means to transfer heat from the heat exchanger to the primary heating system.

2. Heating apparatus comprising a primary heating system having a boiler or furnace suitable for use in a domestic dwelling house and having an outlet for heated gas, a heat exchanger positioned in the path of said heated gas after same has left the boiler or furnace, and heat transfer means interconnected with a water circulation system of the primary heating system to transfer heat from the heat exchanger to the primary heating system.

3. Heating apparatus according to claim 1 or claim 2 wherein the outlet of the primary heating system comprises a flue or exhaust duct of the boiler or furnace and said heat exchanger is mounted in the flue or exhaust duct.

4. Heating apparatus according to claim 3 wherein the heat exchanger is mounted in a housing having an inlet connected to or positioned to receive heated gas from the boiler exhaust duct.

5. Heating apparatus according to claim 4 wherein an outlet of the housing is directly connected to atmosphere.

6. Heating apparatus according to any one of the preceding claims wherein said outlet for heated gas from the primary heating system comprises a balanced flue adapted to pass through an opening in a wall of a dwelling house and having an air inlet for the boiler or furnace surrounding or adjacent to the flue.

7. Heating apparatus according to any one of the preceding claims wherein the heat exchanger is mounted on an external wall of a dwelling house adjacent the outlet of the boiler flue.

8. Heating apparatus according to claim 4 wherein said housing outlet is connected to a continuation of the boiler flue or chimney.

9. Heating apparatus according to any one of the preceding claims wherein the primary heating system comprises a hot liquid circulation system and the heat exchanger comprises liquid-filled tubes with end manifolds connected to said circulation system.

10. Heating apparatus according to any one of the preceding claims wherein the heat exchanger is connected to the primary heating system on the upstream side of the boiler with respect to the direction of liquid flow around the circulation system.

11. Heating apparatus according to claim 10 wherein the inlet and outlet to the heat exchanger are connected to the primary heating system with the heat exchanger inlet connection upstream of the heat exchanger outlet connection.

1 2. Heating apparatus according to any one of the preceding claims wherein temperature responsive means is provided to cause said primary heating system to transfer heat to the heat exchanger during an initial warm-up period on commencing use of the heating apparatus.

13. Heating apparatus according to claim 12 when dependent on claim 11 wherein said temperature responsive means comprises a temperature responsive valve operative to control the passage of heated liquid from the output of the boiler or furnace to the heat exchanger.

14. Heating apparatus according to any one of the preceding claims wherein the inlet and outlet connections to the heat exchanger are provided through a manifold at one end of the heat exchanger, an internal baffle being provided in said manifold between the inlet and outlet connections.

1 5. Heating apparatus according to claim 4 or any one of claims 5 to 14 when dependent on claim 4, wherein said housing of the heat exchanger is insulated to reduce heat loss through the walls of the housing.

1 6. Heating apparatus according to claim 1 5 wherein baffle means is provided in said housing to spread heated gas over the surfaces of the heat exchanger.

1 7. A kit of parts for the conversion of a domestic boiler or furnace to provide heating apparatus as defined in any one of the preceding claims.

1 8. Heating apparatus according to claim 1 substantially as described herein with reference to the accompanying drawings.

1 9. Heating apparatus substantially as described herein with reference to the accompanying drawings.

20. Heating apparatus comprising any novel feature or combination of features disclosed in this application.