GB2239308A

GB2239308A - Supporting device for heat exchanger

Info

Publication number: GB2239308A
Application number: GB8929178A
Authority: GB
Inventors: John Brian Clarke
Original assignee: GEC Marconi Ltd; Marconi Co Ltd
Current assignee: BAE Systems Electronics Ltd
Priority date: 1989-12-23
Filing date: 1989-12-23
Publication date: 1991-06-26
Anticipated expiration: 2009-12-23
Also published as: GB2239308B; GB8929178D0

Abstract

A heat exchanger 3 for re-claiming natural heat from a water tank or the like, has a flotation device 12 connected thereto, the buoyancy of the flotation device being typically adjustable so as to vary the buoyancy of the combined heat exchanger and flotation device. The flotation device conveniently comprises a combination of one or more fixed buoyancy portions and one or more variable buoyancy portions. The heat exchanger may be moved into position in the tank while floating. <IMAGE>

Description

Supporting Device for Heat Exchanger This invention relates to a heat exchanger.

Heat exchangers which are mounted in tanks have been used in OTEC projects (Ocean Thermal Energy Conversion) as described and claimed in the applicants' co-pending UK Patent Application 8905432. The subject of the aforementioned patent application is the heat exchange plant depicted in Figure 1.

Referring briefly to Figure 1 an OTEC plant derives energy from the natural temperature difference existing at different levels in the water. Cold water is pumped from the sea bottom by pumps 1 through an inlet 2 to a heat exchanger 3 contained within a tank 3A. Working fluid, typically ammonia, is cooled and condensed in the heat exchanger 3.

Fluid is then pumped by pump 4 into a second heat exchanger 5 in a different tank 5A, where it is evaporated, obtaining its latent heat from warm water which is supplied by pumps 7 having their inlet 8 close to the sea surface. The resulting ammonia gas under pressure is used to drive a turbine 9 which is connected to an electricity generator, not shown. The ammonia gas then passes back into the heat exchanger 3 where it is once again condensed by the cold water from the sea bed. The heat exchangers comprise banks of heat exchanging panels the panels are sealed to the environment and arranged in large tanks.

These heat exchange elements are formed by a process known as roll bonding. This is defined as a process in which two sheets of material, usually aluminium, are made to adhere or cohere together in selected places but not others; and in which a fluid is then forced in to the places where the sheets have not adhered or cohered together so as to form cavities.

OTEC plants are particularly useful in tropical or sub-tropical environments where a temperature difference up to 15 0C may exist. Here OTEC can be used to generate electricity. However, communications in such environments are often poor and the OTEC plant may be situated in difficult or rocky terrain. Such terrain does not facilitate easy transportation of large, cumbersome heat exchangers or of heavy lifting equipment which is required to assemble the plant. These conditions make assembly of the said plant and transportation of lifting equipment difficult. Also the design of such plant may include piping or other structures over the top of the heat exchanger tank of these make it difficult to position the heat exchanger directly when using an overhead lifting method such as a crane.

It is an object of the present invention to provide a system which can alleviate some or all of these problems.

In accordance with one aspect of the present invention, there is provided a heat exchanger for use in a water tank or the like having a flotation device connected thereto.

Preferably, the buoyancy of the flotation device can be adjusted so as to vary the buoyancy of the combined heat exchanger and flotation device.

Typically, the flotation device comprises a combination of one or more fixed buoyancy portions and one or more variable buoyancy portions. The fixed buoyancy portions may comprise one or more bodies of a solid buoyant material such as a rigid foam. The variable buoyancy portions may comprise one or more inflatable bags or the like.

It will be appreciate that, depending upon application, only one type of buoyant body may be present furthermore the flotation body can be either demountable or permanently fixed to the heat exchanger.

In accordance with another aspect of this invention, there is provided a method of transporting a heat exchanger in a water tank or the like comprising attaching a flotation device to the heat exchanger and adjusting the overall buoyancy thereof such that the combination floats in the tank and allows the position of the heat exchanger to be varied.

The use of the flotation device with heat exchangers used in OTEC plant facilitates the assembly of large tanks and the easy location of the heat exchange panels within the tanks. The flotation devices are attached to the heat exchangers, and after being lifted into some convenient position in the tank the heat exchangers are then floated into position passing under any structures fixed over the tank. The devices may be permanently affixed to the heat exchangers, but are preferably removable once the plant is assembled. The device may be re-used to remove the heat exchange panels where maintenance is required.

By using the flotation device in the manner described in detail below, some of the problems of assembling large heat exchangers in tanks are eased and the need for expensive cranes is removed.

When the flotation device has adjustable buoyancy the heat exchangers can be floated into place and then lowered onto permanent supports.

The invention will now be described, by a way of an example only, and with reference to Figures 2 and 3 in which: Figure 2 illustrates a perspective view of four flotation devices supporting a heat exchanger in a tank, the tank is shown partially cut-away; and Figure 3 illustrates a plan view of several heat exchangers in a tank.

Referring now to the drawings the tank 3A of Figure 1 is shown in greater detail in Figure 2, the tank 3A itself being shown in partial section. The tank 3A is provided with an inlet port 14 and an outlet port 15 which allow the tank 3A to be filled or emptied of water. A row of support struts 30 are provided on the bottom of the tank 3A and a working fluid inlet pipe 29 and outlet pipe 39 are provided.

In use, the tank 3A is filled with water and a flotation device comprising buoyant members 12a, 12b, 12c and 12d are attached to the heat exchanger 3. The buoyancy of the flotation device is adjusted such that the combined heat exchanger 3 and flotation device floats. The heat exchanger 3 is floated into position adjacent the inlet and outlet pipes 29, 39 which are connected to respective valves 20, 21 provided on the heat exchanger 3. The heat exchanger is then lowered onto the struts 30 by decreasing the buoyancy of the flotation device.

In the present case, the members 12a, 12b and 12c comprise blocks of rigid foam, coated in a silicon rubber compound to import strength thereto and render them waterproof. A further member corresponding to 12b is provided on the opposite end of the heat exchanger 3 but is omitted for clarity. The member 12c comprises an inflatable bag, inflation or deflation of the bag being used to increase or decrease the overall buoyancy. Once the heat exchanger is in position, the deflated bag 12c can be removed from the heat exchanger 3A. The remaining members can remain to provide protection for the heat exchanger 3, if required.

Referring briefly to Figure 3, the flotation devices are shown in use to float an eighth heat exchanger into its correct position in a large tank. The plan view shows the tank wherein seven heat exchangers are already in position.

The orientation of the heat exchanger and the shape aids the flow of water by channelling water across the heat exchangers.

While the present invention has been described specifically in relation to a water tank situation, it will be appreciated that the invention can be applied to any situation in which a relatively large and/or heavy heat exchanger is required to be positioned in a tank of liquid.

Changes can be made while remaining within the scope of the invention, for instance, the heat exchanger may be fully or partially submerged in the tank while resting on supports or alternatively may float in the tank while in use.

Claims

1. A heat exchange for use in a water tank or the like having a flotation device connected thereto.

2. A flotation device for use with a heat exchanger as defined in claim 1, said device comprising one or more buoyant members.

3. A flotation device as claimed in claim 2 the buoyancy of which can be varied.

4. A flotation device as claimed in claim 3, comprising a combination of buoyant members having fixed or variable buoyancy.

5. A flotation device as claimed in either of claims 3 or 4 wherein at least one buoyant member comprises an inflatable bag, ballast tank or the like.

6. A method of transporting a heat exchanger in a water tank or the like comprising attaching a flotation device to the heat exchanger and adjusting the overall buoyancy thereof such that the combination floats in the tank and allows the position of the heat exchanger to be varied.

7. A heat exchanger which is substantially as herein described in relation to Figures 2 and 3 of the accompanying drawings.

8. A flotation device which is substantially as herein described in relation to Figures 2 and 3 of the accompanying drawings.

9. A method of transporting a heat exchanger which is substantially as herein described.