WO1991016578A1

WO1991016578A1 - Heating systems

Info

Publication number: WO1991016578A1
Application number: PCT/GB1990/000644
Authority: WO
Inventors: Edward John Guy
Original assignee: Edward John Guy
Priority date: 1988-11-01
Filing date: 1990-04-26
Publication date: 1991-10-31
Also published as: GB2224348B; GB8825507D0; GB8924509D0; GB2224348A

Abstract

A heating system in which gravity is used to create a pressure difference to drive heated fluid around a circuit. The circuit comprises a boiler (1) with or without a circulating pump (6), rising feed and return pipes (26 and 46) connected to the upper end of a counterflow preferably coaxial heat exchanger formed from a downward flowing channel (2a) connected to the feed pipe (2b) and an upward flow return channel (4a) connected to the return pipe (4b). The lower end of the heat exchanger is connected to a heat dispenser (3) which can be a radiator or coil for indirectly heating water in a tank. Radiators (figs. 12-18) incorporating a similar gravity induced flow by means of a downward flowing feed channel (35) closely associated with a rising return channel (36) can be used to improve flow characteristics in the system.

Description

HEATING SYSTEMS

This invention relates to a heating system for a building in which heat transfer fluid, generally water- is heated by a boiler and supplied to radiators and/or other heat dispensing devices through a pipe circuit which returns the cooled fluid to the boiler for recycling.

Heating circuits of this type generally comprise at least one pump, usually electrically driven, to provide forced circulation of fluid through the pipes. The need to provide such a pump increases the cost of the installation and increases the power consumption, also the pump requires periodic maintenance a^nd is a common cause of breakdown of the system.

It may be possible to provide a circuit which has no pump in which the fluid is passed around the circuit under the effect of temperature alone. As hot fluid has a lower density than cold fluid, when the circuit feed and return pipes extend upwardly from the boiler the heated fluid will tend to rise in the feed pipe and create a pressure difference to drive the fluid around the circuit. However an unforced circulation system of this nature can only be made to work if the radiators are at a much higher vertical level than the boiler. If the radiators are at or near the same level as the boiler, or below it, cooling of the fluid by the radiators causes a pressure difference between the inlet and outlet pipes extending above the radiator which opposes and cancels the pressure difference generated by the boiler. In modern buildings which have no basement it is often inconvenient or expensive to provide a large difference in height between the boiler and the radiators which it supplies. The present invention is intended to provide a heating system which does not require a pump to circulate the fluid and in which the radiators or other heat-dispensing devices may be at the same vertical level, or even below, the boiler.

According to the invention, there is provided a heating system comprising a boiler for heating a liquid, a feed pipe conducting heated liquid from the boiler to at least one heat dispenser and a return pipe returning cooled liquid to the boiler for recycling, the feed and return pipes extending upwardly from the boiler and downwardly towards the heat dispenser, heat exchange means arranged to transfer heat from the liquid in the downwardly , extending part of the feed pipe to the liquid in the downwardly extending part of the return pipe to at least partially equalise the liquid temperatures therein.

The heat dispenser may be positioned below or level with the boiler and may comprise a radiator, a coil for indirect heating of water in a tank, or other device intended to discharge heat. A heat sink such as a radiator or coil for indirect heating of water may be provided for withdrawing heat from the return pipe at a point between the downwardly extending part and the boiler.

Heating systems according to embodiments of the invention will now be described by way of example with reference to the accompanying drawings in which: Fig. 1 shows schematically a heating system for a single story building, according to the invention,

Figs. 2, 4 and 6 show schematically heat exchangers for use in the system of Fig. 1,

Fig. 3, Fig. 5 and Figs. 7 and 8 show cross-sections of the exchangers of Figs. 2, 4 and 6 respectively,

Fig. 9 shows a heating system in a two story house according to the invention,

Fig. 10 shows another heating system according to the invention,

Fig. 11 shows part of the system of Fig. 10,

Fig. 12 i-β a part perspective view of a panel radiator for the system of the invention,

Fig. 13 is a partial horizontal cross section of the top of the radiator of Fig. 12,

Fig. 14 is a partial cut away perspective view of another and tubular radiator for the system of the invention,

Fig. 15 is a partial horizontal cross section of the top of the radiator of Fig. 14,

Fig. 16 is a partial perspective view of another panel radiator for the system of the invention, Fig. 17 is a partial perspective view of a square tubular radiator for the system of the invention,

Fig. 18 is a partial perspective view of another tubular radiator for the system of the invention and

Fig. 19 shows another heating system according to the invention.

Referring to Fig. 1, a heating circuit in a single story building comprises a boiler 1 for heating water which is fed from the boiler through feed pipe 2 to a radiator 3 in another room of the building. The water is returned from the radiator 3 to the boiler through return pipe 4. The boiler may be of a conventional type and the circuit may be provided with an expansion tank and device for replenishing the water in the system in known manner. T^ie feed and return pipes extend upwardly above the boiler and downwardly towards the radiator, which in the embodiment shown is at substantially the same vertical level as the boiler.

The downwardly extending parts 2a and 4a of the feed and return pipes are arranged as a heat exchanger so that heat is transferred from the water in pipe part 2a to the water in return pipe part 4a before the water fed through pipe 2 reaches the radiator. The effect of this heat transfer is to remove or substantially reduce the difference in temperature between the water in pipe parts 2a and 4a. The difference in water density between these pipe parts, which would otherwise oppose circulation of water through the pipes in the desired direction, is accordingly removed or reduced. Return pipe 4 as shown also has connections to a radiator 5 in conventional manner in the downwardly extending part of pipe 4b. This radiator may be positioned in another room of the building and gives a reduction in the temperature of the water returning to the boiler. As the hotter water in part 2b has a less density than the colder water returning through part 4b, and the difference in water density between parts 2a and 4a is small, the water is driven in circulation through the circuit under the effect of gravity alone and no pump is required. The higher the heat output of the boiler, the higher the water temperature in the feed pipe so that the rate of circulation of the water is greater at higher boiler output.

Where the temperature difference betweep the flow and return line 2a and 4a at the top of the heat exchanger is adequate and/or where the transfer of heat energy between flow and return lines in the heat exchanger is sufficient to cause an increase in kinetic energy in the liquid, the thermal effect may be adequate to sustain circulation without the need for radiator 5 to be connected or operative.

Multiple return drop such as several pipes 4b are believed to assist the circulation of water within the system.

If desired, a pump 6 may be inserted in the piping in known manner to augment the flow of water. During normal operation this pump will not be required, but it may be used occasionally when the flow of water has to be increased for example for a very rapid warm up. Figs. 2, 4 and 6 show different types of heat exchange arrangement between. - parts 2a and 4a of the pipes. In the arrangement of Figs. 2 and 3 the pipe parts 2a and 4a are arranged parallel and both are surrounded by a water-filled jacket 6 so that heat is transferred from part 2a to part 4a through the water in the jacket. The jacket may be supplied with water from an external source, or supplied through orifices 8 (see below). In this arrangement pipe parts 2a and 4a may have the same diameter as the remainder of the pipes in the circuit, and resistance to flow of the water through the pipes is not restricted in any way. The heat exchanger may be constructed entirely of standard pipes and fittings and the external water jacket, surrounding pipe parts 2a and 4a completely, gives good heat transfer characteristics. This type of exchanger may be used vfith advantage in factories and offices where bulk is not a problem and in which the •» pipes of the heating circuit are commonly enclosed in ducts.

Figs. 4 and 5 show an alternative type of exchanger in which part 4a is surrounded by coaxial part 2a. This arrangement is less bulky than that of Fig. 2, a high wetted area of heat exchange is still obtained and standard pipe components may again be used. In this arrangement however the resistance to flow through the exchanger may be higher.

In the arrangement of Fig. 6 and Fig. 7 or 8 the parts 2a and 4a together form a single pipe. In the Fig. 7 arrangement the single pipe is divided by partition 7 through which the heat is conducted, partition 7 dividing the pipe into pipe parts 2a and 4a. The cross section of the single pipe shown is circular but may be square. This arrangement is economical in material and low in bulk but the area through which heat is transmitted between parts 4a and 2a is limited. The arrangement of Fig. 8 is similar but pipe part 2a comprises a pipe of lesser diameter within pipe part 4a. The Fig. 8 arrangement has a greater area available for heat transfer than the Fig. 7 arrangement. The heat exchangers shown in Figs. 2, 4 and 6 can be constructed from tubing other than having a round cross section. For instance a square cross section can be used.

In all these types of heat exchanger the materials used for components through which heat passes should be good heat conductors and it is preferable for the outer surfaces of the exchanger to be insulating. This may be achieved by making all internal components of copper, generally standard copper pipe, and by lagging the external surfaces. Alternatively, insulating materials may be used for the external surfaces.

Whatever the type of heat exchanger used, if the system is to be operated without pumping it is generally necessary to provide a priming facility to allow circulation of water unrestricted by air locks in the desired direction when starting up from cold. This may be achieved by forming an orifice of restricted diameter, marked 8 in Fig. 1, between parts 2a and 4a at the upper end of the heat exchanger. When the boiler is started heated water tends to rise through part 2b and some of the heated water, passing from pipe 2 to pipe 4 through orifice 8, induces a flow of water in the desired direction through parts 2a and 4a and hence through radiator 3. Once flow has started, the cycle of water through the system is self-sustaining while the boiler continues to heat the water. A series of orifices 8 even if not necessary may be provided along the exchanger, as shown in Figs. 2 and 4, if required. When the system is running restricted flow of water through these orifices may be used to advantage to increase the rate of heat transfer between parts 2a and 4a.

Instead of providing orifices 8 in solid pipe, the members through which heat and water are transmitted may be of porous, heat-conducting material.

In the arrangements shown in Figs. 2, 4 and 6 the radiator is connected in series with the pipes 2 and 4. Alternatively, the radiator may be connected in parallel with the pipes by suitable modificatioa either within the radiator itself or at the lower part of the heat exchanger formed by parts 2a and 4a.

Fig. 9 shows diagrammatically a possible arrangement using the heating arrangement of the invention installed in a house. A boiler 1 situated on the first floor, or the ground floor of a house having a basement, supplies hot water to a radiator 10 on the floor below, a radiator 11 on the same floor, a radiator 12 on an upper floor and the coil of a hot water supply tank 13. The water is impelled around the piping circuit by the temperature difference in the feed and return pipes leading upwardly from the boiler and the pipes extending downwardly to radiators 10 and 11 are provided with heat exchangers as described above to cancel the pressure differences opposing circulation of water. Radiator 12 and tank 13 act as heat sinks on the return pipe. In the arrangement shown the radiators are at floor level but they may alternatively be positioned at ceiling level, the heat being radiated downwardly.

Fig. 10 shows another arrangement in which a number of radiators are fed with hot water by means of a ring main. The boiler 1 supplies hot water through upwardly extending pipe 21 to a horizontal ring main 22 which, as shown in Fig. 11, comprises pipes separated by an internal heat-conducting partition 23 so that the water temperatures in the feed and return pipes are substantially equ l. The horizontal main may be installed below a floor of the building to be heated, or behind the skirting at floor level. Radiators 27, at substantially the same level as the horizontal main, may be of the parallel type in which water is withdrawn from and returned to a continuous pipe and radi tor 24, below the level of the horizontal main, is of the series type taking water from the horizontal feed pipe of the ring main and returning it to the horizontal return pipe.

Downwardly extending pipes 25 connected to radiator 24 are also joined by a heat-conducting partition.

In this arrangement pipe 21 from the boiler supplies hot water to the horizontal feed pipe of the ring main and pipe 26 withdraws water from the return pipe of the main to deliver it to the coil of hot water tank 28 acting as a heat sink. Cold water is returned to the boiler by pipe 29 and the water is impelled around the circuit by the temperature difference between pipes 21 and 26 containing hot water and pipe 29 containing colder water. In this arrangement heat exchange takes place not only in pipe 25, but also in the horizontal pipes 22. The horizontal ring main may be at, above or below the level of the. boiler and more than one ring may be installed to heat more than one floor. It is possible to use this system to provide under floor heating.

The principle and methods used to effect the heat exchange between supply and return pipes in order to enhance the gravity effect, can also be applied to radiators as shown in Figs. 12 to 19.

Figs. 12 and 13 show a panel type radiator 30 having vertical exterior walls 31 and 32 and an internal central dividing wall 33 extending from the top 39 of the radiator to a point above the expanded bottom 34 of the radiator so as to provide a downwards flow channel 35 interconnected at bottom 34 to an upwards flow channel 36. Immediately below the top 39 a horizontal inlet channel 37 is formed which is connected to the downwards ^low channel 35 and alongside channel 37 an outlet channel 38 is formed which is connected to the upwards flow channel 36 in the expanded top 39 of the radiator. Radiator inlets and outlets are connected to the respective channels 37 and 38.

Figs. 14 and 15 show a tubular radiator 40 with an upper horizontal tube 41 divided into an outlet and inlet channel by means of a plate 42. Below tube 41 is a lower undivided horizontal tube 43. The horizontal tubes are interconnected with vertical tubes 44 divided by plates 45 so that flow is induced from a radiator inlet 46 in tube 41 down each downwards flow channel 47 into lower tube 43 and up each upwards flow channel 48 to upper tube 41 and radiator outlet 49. Further radiators are shown in accordance with the invention in Figs. 16, 17 and 18. These radiators are designed to provide a more effective heat exchange between radiator inlets and outlets than those shown in Figs. 12 to 14 where only a single divider plate is provided. Fig. 16 shows a radiator 50 with outer walls 51 and 52, an upper expanded portion 53 and a lower expanded portion 54. Two divider plates 55 and 56 are mounted vertically between walls 51 and 52 to define a single upper horizontal inlet channel 53' which continues into an inner downwards flow channel 57 and two outer outlet channels 53' ' which continue into outer upwards flow channels 58. A radiator inlet is connected to inlet channel 53' and a radiator outlet is connected to outlet channels 53' ' either at the same end of the radiator or at the other end of the radiator.

Fig. 17 shows at 60 a radiator formed from square cross sectional tubing. The upper horizontal tube 61 is divided by plate 62 to provide a horizontal inlet channel 63 and a horizontal outlet channel 64. Outer square vertical tube 65 has an inner coaxial vertical tube 66 which provides a downwards flow channel 67 connected to channel 63 and an upwards flow channel 68 connected to channel 64. A radiator inlet and outlet is connected at the same or opposite ends of channels 63 and 64. In a similar way to Fig. 16, the radiator has a common undivided horizontal lower tube (not shown) connected to the bottom of vertical tubes 65 and 66 to provide an interconnection between channels 67 and 68.

Fig. 18 shows at 70 a radiator formed from circular cross sectional tubing. The connections are similar to those shown in Fig. 17 with an upper horizontal tube 71 divided by horizontal plate 72 to provide a horizontal inlet channel 73 and a horizontal outlet channel 74. An outer vertical tube 75 has an inner coaxial vertical tube 76 providing a downwards flow channel 77 connected to channel 73 and an upwards flow channel 78 connected to channel 74. A common undivided horizontal lower tube 79 is connected to the bottom of tubes 75 and 76. A horizontal plate 80 in tube 79 supports the lower end of tubes 76 and perforations 82 in plate 80 provide interconnections between channels 77 and 78.

Fig. 19 shows a possible installation for radiators shown in Figs. 12 to 18 in rooms defined upwardly by ceiling 90 and by floor 91. Vertical panel divided radiator 92 is connected by coaxial heat exchange pipes 93 and 94 to horizontal feed and return mains pipes 89 and 95. Low panel radiator 96 is similarly connected via heat exchange pipes 97 and 98. Either one or both upper corners of radiators 92 and 96 can be connected on each radiator to the feed and return mains. Radiator 99 is a similar radiator to radiator 92 but is connected conventionally to pipes 89 and 95. A boiler 100 is connected by an upwardly extending feed pipe 101 to the feed mains 89 and an upwardly extending return pipe 102 is connected to the return mains 95. Pipe 102 may be a single pipe or several pipes the total internal volume of which is between two and three and a half times the internal volume of pipe 101. In an actual installation, pipe 101 is a 28 mm pipe whilst pipe 102 is represented by four 22 mm pipes and a fifth 28 mm pipe. A comparison between one 28 mm pipe and the five pipes indicated that a flow of 0.016 litres per second (127 lbs./hour) was achieved with a single pipe whilst for five pipes the flow rate was 0.022 litres per second (175 lbs./hour). These flow rates were obtained with the restriction of an inoperative off pump, high resistance indicators and TRVS in line.

The feed and return mains are at least 2 m above the boiler and in practice about 2.44 m (8 ft.) A typical heat exchange pipe would be about 1.6 m long or 1.5 to 2 m.

Claims

CLAIMS :

1. A heating system comprising a boiler for heating a liquid, a feed pipe conducting heated liquid from the boiler to at least one heat dispenser and a return pipe returning cooled liquid to the boiler for recycling, the feed and return pipes extending upwardly from the boiler and downwardly towards the heat dispenser, heat exchange means arranged to transfer heat from the liquid in the downwardly extending part of the feed pipe to the liquid in the downwardly extending part of the return pipe to at least partially equalise the liquid temperatures therein.

2. A system as claimed in claim 1 wherein the heat dispenser is below or level with the boiler.

3. A system as claimed in claim 1 or 2 wherein the heat exchange means comprises two substantially coaxial channels.

4. A system as claimed in claim 3 wherein the outer channel is substantially a 28 mm pipe and the inner channel is substantially a 15 mm pipe.

5. A system as claimed in any one of claims 1 to 4 wherein substantially horizontal feed and return mains extend between the upwardly extending pipes from the boiler and the heat exchange means.

6. A system as claimed in claim 5 wherein the feed and return mains are at least 2 m above the boiler.

7. A system as claimed in claim 5 or 6 wherein a plurality of return pipes is provided which extend from the horizontal return mains to the boiler.

8. A system as* claimed ^• i any one of claims 5 to 7 wherein the internal— olume of the piping from the horizontal return mains to the boiler is at least twice the internal volume of the piping from the boiler to the horizontal feed mains.

9. A system as claimed in claim 8 wherein the internal volume of the piping from the horizontal return mains is between two and three and a half times the internal volume of the piping from the boiler to the horizontal feed mains.

10. A system as claimed in any one of claims 1 to 9 wherein the heat dispenser is a radiator comprising an upper horizontal outlet channel, an upper horizontal inlet channel, a lower horizontal conduit and at least one vertical downwards flow channel connecting the inlet channel and the lower conduit and at least one vertically upwards flow channel connecting the lower conduit and the outlet channel, means being provided to connect the inlet and outlet channels to the feed and return pipes.

11. A system as claimed in claim 10 wherein the upper horizontal outlet channel and upper horizontal inlet channel are formed within a divided upper part of the radiator.

12. A system as claimed in claim 10 or 11 wherein one or more vertical dividing plates extending upwardly from the lower conduit form the flow channels.

13. A system as claimed in claim 10 or 11 wherein a pair of coaxial tubes form the flow channels.

14. A radiator as claimed in any one of claims 10 to 13.

15. A heating system substantially as described with reference to Figs. 1 to 19 of the accompanying drawings.

16. A radiator as claimed with reference to Figs. 12 to 18 of the accompanying drawings.