GB2029950A - Heat exchanger for gaseous media - Google Patents

Abstract

A heat exchanger for transmitting heat from a first gaseous medium to a second gaseous medium at a temperature lower than the first, comprises two chambers 8, 9 which are partly filled with a solid, particulate, heat- transmitting medium, for example sand, stones, glass or metallic spheres. Pipes 22 are provided for introducing the first gaseous medium from a manifold 18 into the chamber 9, in which the upwardly flowing gaseous medium produces a fluidised bed 45 of the heat-transmitting medium. Pipes 28 are provided for introducing the second gaseous medium from a manifold 19 into the chamber 8, in which the upwardly flowing gaseous medium produces a fluidised bed 44 of the heat- transmitting medium. In each chamber 8, 9 there is a respective weir 25, 26 over which some of the fluidised bed material can flow and pass to the other chamber, the arrows C indicating this movement of the bed material from chamber 8 to chamber 9. The gaseous media leaves the chambers 8, 9 via outlets 42, 43, respectively. <IMAGE>

Description

SPECIFICATION Heat exchanger for gaseous media This invention relates to a heat exchanger for transmission of heat between gaseous media.

Regenerative heat exchangers for the transmission of heat between gaseous media are known, in which heat is transmitted from a hot gaseous medium to a heat resistant, intermediate, heattransmitting medium and from the latter to cold gaseous medium, which is heated. In one known heat exchanger of this kind, granules are injected into a container by means of gas, from where they are allowed to fall by gravity through a channel into another point of injection for gas, from which they are injected into a second chamber, which is in communication with the first-mentioned chamber.

Granules can thus be transported between the two chambers while being regeneratively heatexchanged. The problem is to make such a device work efficiently, and the present invention aims to provide a solution to this problem.

According to the invention a heat exchanger for transmitting heat from a first gaseous medium to a second gaseous medium at a temperature lower than the first, comprises at least two chambers which are partly filled with a solid, particulate, heat-transmitting medium, means for passing the first gaseous medium through a first of said chambers to effect fluidisation of the particulate material therein, means for passing the second gaseous medium through a second of said chambers to effect fluidisation of the particulate material therein, means for transporting particulate material from the fluidised bed in said first chamber into the second chamber and means for transporting particulate material from the fluidised bed in the second chamber to the first chamber, whereby the first gaseous medium is cooled and the second gaseous medium is heated in passing through the chambers.

A heat exchanger in accordance with the invention provides an efficient transfer of heat from the hotter gaseous medium to the heat-transmitting medium and from the latter heat is transferred to the colder gaseous medium, which is heated. The heat exchanger can be employed for example, for preheating the combustion air supplied to different forms of incineration devices.

The invention will now be described, by way of example, with reference to the accompanying drawing, in which Figure 1 is a schematic sectional side elevation of a heat exchanger in accordance with the invention, the section being taken on the line I - I of Figure 2, Figure 2 is a plan of the heat exchanger of Figure with its cover removed, and Figure 3 is a sectional view taken on the line Ill - Ill of Figure 1.

The heat exchanger shown in the drawing comprises a parallelepipedic tank 1 having end walls 2, 3, side walls 4, 5, a bottom 6 and a cover 7. Internally, the tank is divided into two chambers 8, 9 by a transverse partition 10.

Seven vertical partitions 11 - 17 are secured to the tank bottom 6 in parallel spaced-apart relationship, these partitions being parallel to the tank side walls 4, Sand extending only a short distance upwardly in the tank 1. Manifolds 18,19 are secured to the lower edges of the end walls 2,3, respectively.

Four pipes 20 - 23 extend from the manifold 18 across the tank bottom 6, parallel to the tank side walls 4, 5, the pipe 20 bing disposed between the side wall 4 and the partition 11, the pipe 21 being disposed between the partition walls 12 and 13, the pipe 22 being disposed between the partitions 14 and 15 and the pipe 23 being disposed between the partitions 16 and 17. Each of the pipes 20 - 23 passes through two transverse partition walls 25, 26, and the open ends of these pipes all terminate in the tank chamber 9.

Four more pipes 27 - 30 extend from the manifold 19 across the tank bottom, parallel to the tank side walls 4, 5, the pipe 27 being disposed between the partitions 11 and 12, the pipe 28 being disposed between the partitions 13 and 14, the pipe 29 being disposed between the partitions 15 and 16 and the pipe 30 being disposed between the partition 17 and the side wall 5. Each of the pipes 27 - 30 also passes through the partition walls 25, 26, and the open ends of these pipes all terminate in the tank chamber 8.

In the tank chamber 8 the upper edges of the partitions 11, 12 are bridged by the plate 31, the upper edges of the partitions 13, 14 are bridged buy a plate 32, the upper edges of the partitions 15, 16 are bridged by a plate 33 and a plate 34 bridges from the upper edge of the partition 17 to the side wall 5 of the tank. Each of the plates 31 - 34 is parallel to the tank bottom 6 and extends from the partition wall 10 to the end of the respective partitions in the tank chamber 8. In the tank chamber 9 a partition 35 bridges the gap from the upper edge of the partition 11 to the side wall 4 of the tank, the upper edges of the partitions 12,13 are bridged buy a plate 36, the upper edges of the partitions 14, 15 are bridged by a plate 37 and the upper edges of the partitions 16, 16 are bridged by a plate 38.Each ofthe plates 35-38 is parallel to the tank bottom 6 and extends from the partition wall 10 to the end of the respective partitions in the tank chamber 9.

The transverse partition wall 10 has its lower edge at the level of the plates 31 - 38. The partition walls 25, 26 extend down to the tank bottom 6 and extend from the side wall 4 to the side wall 5 above the plates 31 - 38. However, the partition walls 25,26 only traverse some of the gaps between the partitions 11 - 17, as can be seen from Figure 3. Thus the partition wall 25 traverses the gap between the tank side wall 4 and the partition 11, the gap between the partitions 12 and 13, the gap between the partitions 14 and 15 and the gap between the partitions 16 and 17. On the other hand, the partition wall 26 traverses the gap between the partitions 11 and 12, the gap between the paritions 13 and 14, the gap between the partitions 15 and 16 and the gap between the partition 17 and the tank side wall 5.

Considering, for example, the pipe 22, from the description so far it will be appreciated that the part of this pipe that is situated in the tank chamber 9 is disposed in an open-ended tunnel having side walls formed by the partitions 14 and 15 and a roofformed by the plate 37, the open end of the pipe terminating short of that end of the tunnel which is remote from the partition wall 10. The side walls of this tunnel extend into the tank chamber 8, but not the roof thereof. Accordingly, there is communication between the tank chambers 8 and 9 via a horizontal aperture 39 between the partition walls 10 and 25 and the tunnel just described. Each of the other pipes 20,21,23 and 27 - 30 has its part adjacent its open end situated in a similar tunnel which provides communication between the tank chambers 8 and 9.

The manifolds 18, 19 have inlet pipes 40, 41, respectively, and there are outlet pipes 42, 43 from the tank chambers 8 and 9, respectively.

In use of the above-described heat exchanger to effect a heat exchange between cold air and a hot gas, a particulate material, for example sand, is placed in each of the tank chambers 8 and 9, the cold air is introduced into the manifold 19 via pipe 41 and the hot gas is introduced into the manifold 18 via pipe 40. The cold air introduced into the manifold 19 flows through the pipes 27 - 30 and is discharged from the open ends of these pipes into the tank chamber 8 where it fluidises the particulate material to form a fluidised bed 44. At the same time, the hot gas introduced into the manifold 18 flows through the pipes 20 - 23 and is discharged from the open ends of these pipes into the tank chamber 9 where it fluidises the particulate material to form a fluidised bed 45.When the fluidised bed 44 has been estab lished, some of the bed material flows over the upper edge of the partition wall 25 into the space 46 between the partition walls 25 and 10 and falls through the horizontal apertures at the bottom of this space, such as the aperture 39, into the above described tunnels associated with the pipes 20 - 23.

The hot gas issuing from the pipes 20 - 23 entrains this bed material and injects it into the fluidised bed 45 in the tank chamber 9. In like manner, some of the bed material ofthefluidised bed 45 flows over the upper edge of the partition wall 26 into the space 47 between the partition walls 26 and 10 and falls into the above-described tunnels associated with the pipes 27-30. This bed material is entrained by the cold air issuing from the pipes 27 - 30 and is injected into the fluidised bed 44. In this way there is a continuous interchange of particulate material be tween the fluidised beds 44 and 45. The air flowing upwardly in the tank chamber 8 leaves the latter via the outlet pipe 42 and the gas flowing upwardly in the tank chamber 9 leaves the latter via the outlet pipe 43. There is no interchange between the air flow and the gas flow.

In Figure 1, the flow of the hot gas is shown by the single solid line arrows A and the flow of the cold air is shown by the double solid line arrows B. The flow of particulate material from the fluidised bed 44 to the fluidised bed 45 is shown by the single dashed line arrows C and the flow of particulate material from the fluidised bed 45 to the fluidised bed 44 is shown by the double dashed line arrows D.

By way of example, the apparatus described above was employed to heat air from a temperature of 0 C (at the inlet pipe 41) to a temperature of 200"C (at the outlet pipe 42) by supplying hot gas to the inlet pipe 40 at a temperature of about 400"C. The velocity of the air in the pipes 27 - 30 and of the hot gas in the pipes 20 - 23 was in the range of from 40 to 50 m/s. When the apparatus had reached a state of temperature equilibrium, the particulate material in the fluidised beds had a temperature of just over 200"C. This material flowing past the pipes 20 - 23 through which the hot gas flowed, had a cooling effect on these pipes enabling the apparatus to withstand the high gas inlet temperature.

The apparatus described above may be modified in various ways. Thus more or less than four pipes 20 - 23 and more or less than four pipes 27 - 30 may be employed and the staggered arrangement of the open ends of these pipes (which is done to provide even distribution of the air and gas into the fluidised beds) may be varied. Particulate material other than sand, for example stones, glass spheres, metallic spheres or other heat resistant granular material, may be employed in th fluidised beds.

Furthermore, the apparatus can be employed for effecting heat exchange processes between other gaseous media and at different temperatures from those mentioned above.

From the above description it will be appreciated that the heat exchanger has no movable parts and it is inexpensive to manufacture because the heat exchange surface (namely the particulate bed material) is inexpensive. Furthermore, the construction lends itself readily to a modular design.

Claims (6)

1. A heat exchanger for transmitting heatfrom a first gaseous medium to a second gaseous medium at a temperature lower than the first, comprising at least two chambers which are partly filled with a solid, particulate, heat-transmitting medium, means for passing the first gaseous medium through a first of said chambers to effect fluidisation of the particulate material therein, means for passing the second gaseous medium through a second of said cham bers to effect fluidisation of the particulate material therein, means for transporting particulate material from the fluidised bed in said first chamber into the second chamber and means for transporting particulate material from the fluidised bed in the second chamber to the first chamber, whereby the first gaseous medium is cooled and the second gaseous medium is heated in passing through the chambers.

2. A heat exchanger according to claim 1, in which the introduction of each of the gaseous media to its respective chamber is effected through at least one pipe arranged at the bottom of the respective chamber.

3. A heat exchanger according to claim 1, in which said at least one pipe enters said first or second chamber via the second or first chamber, respectively.

4. A heat exchanger according to claim 3, in which a plurality of pipes is provided for the introduction of each of said gaseous media into its respective chamber, the pipes being disposed side by-side with the pipes for the introduction of the first gaseous medium alternating with the pipes for the introduction of the second gaseous medium.

5. A heat echanger according to any of claims 2 to 4, in which the transport of particulate material from the fluidised bed of one chamber to the other chamber is assisted by injector effect of the gaseous medium entering said other chamber.

6. A heat exchanger constructed and arranged substantially as herein described with reference to, and as illustrated in, the accompanying drawing.