GB2284472A

GB2284472A - Spirally wound plate heat exchanger

Info

Publication number: GB2284472A
Application number: GB9422772A
Authority: GB
Inventors: James Martin Robertson
Original assignee: UK Atomic Energy Authority
Current assignee: UK Atomic Energy Authority
Priority date: 1993-12-02
Filing date: 1994-11-11
Publication date: 1995-06-07
Also published as: GB9422772D0

Abstract

A heat exchanger assembly includes a tubular mandrel 25 onto which are wound two long thin plates 30, 31. The plates are spaced apart radially, so they define passages (33, 34, figure 3) for two fluids. At the ends of the assembly the edges of adjacent plates are sealed by discontinuous strips 36, 37 between whose ends are gaps 38, 39; the gaps provide for fluid communication with the passages (33, 34). The assembly also includes headers (28, figure 1) communicating with one set of gaps 39 and so with one of the passages (34). The gaps communicating with one passage are staggered. Circumferentially relative to the gaps communicating with the other passage. <IMAGE>

Description

Heat Exchanger This invention relates to a plate-type heat exchanger.

Heat exchangers enable heat transfer to take place between two fluids by causing them to flow in adjacent ducts. In plate type heat exchangers ducts are defined between parallel spaced-apart plates, and adjacent plates may be spaced apart for example by fins integral with one or other plate, or by a corrugated spacer. For example UK patent GB 734 938 describes a plate heat exchanger matrix of generally cylindrical shape incorporating alternate corrugated sheets and flat sheets all bent into an arcuate shape; the directions of the corrugations are such that one gas flows circumferentially around the matrix and the other gas flows parallel to the axis of the cylinder.

According to the present invention there is provided a heat exchanger comprising at least two spirally-wound plates defining a generally annular heat exchange matrix, adjacent plates in the matrix being spaced apart radially so as to define at least two ducts for fluids, and at each end of the matrix the edges of adjacent plates being sealed together leaving at least one gap communicating with each duct for each turn of the spiral, the gaps communicating with one duct being circumferentially staggered with respect to the gaps communicating with another duct in an adjacent turn of the spiral.

Preferably the gaps communicating with one duct at one end of the matrix lie on generally radial lines, and the heat exchanger comprises one or more headers at that end communicating with the said gaps. Similarly, headers are provided at the other end of the matrix.

Preferably the heat exchanger also comprises a cylindrical core or mandrel for the heat exchange matrix, and a cylindrical pipe or pressure vessel in which the matrix locates. Heat exchange can be arranged to occur between a first fluid supplied via the headers to one duct in the matrix, and a second fluid flowing along the pipe and via the gaps to the other duct.

The plates may be held apart by separators, or may be ridged to define fins, or may be corrugated. The separators, fins or corrugations may be arranged to constrain the fluid flows along particular desired paths, for example to ensure flows on opposite sides of a plate are in countercurrent. The plates may be of any material which conducts heat sufficiently well, for example of metals such as titanium or stainless steel, or non-metals such as plastics or ceramics. The material must be chosen in accordance with the pressures and temperatures to which it will be subjected in use, and the required heat flux.

The heat exchanger may form part of a pipeline, which may be a high pressure pipeline, and may be of the same diameter as the pipeline. It may be a compact heat exchanger, providing more than 100 m2/m3 of heat transfer surfaces, preferably more than 200 m2/m3. The external diameter of the heat exchange matrix might be between 0.1 m and 1.5 m, and its axial length would typically be between about a half and five times its diameter. The plates might be of titanium alloy or stainless steel, of thickness between about 0.2 mm and 1.2 mm, preferably about 0.25 mm. The radial width of the ducts defined between adjacent plates might be between 1 mm and 10 mm, preferably between 1 mm and 3 mm.

The invention also provides a method of making such a heat exchanger.

The invention will now be further described, by way of example only, with reference to the accompanying drawings in which: Figure 1 shows a longitudinal sectional view of a high-pressure pipeline in which a heat exchanger is installed; Figure 2 shows a sectional view on the line II-II of Figure 1; Figure 3 shows to a larger scale and in greater detail the part of the heat exchanger of Figure 1 marked A; and Figure 4 shows a sectional view on the line IV-IV of Figure 3.

Referring to Figure 1 there is shown part of a pipeline carrying high pressure natural gas (at about 200 atmospheres, and a temperature usually about 150"C but which may be as much as 250"C), the gas flowing along a pipe 10 and then along a branch pipe 12 as indicated by arrows P. Within the pipe 10 is a heat exchange assembly 14 of cylindrical shape whose diameter is just less than that of the pipe 10. A support tube 16 extends from the upper end (as shown) of the assembly 14 through an end plate 18 which closes the end of the pipe 10, the end plate 18 being fixed to the pipe 10 by bolts 20 (only two are shown), and the tube 16 being welded to the end plate 18.

Outside the end plate 18 the tube 16 communicates with a tube 21; another tube 22 extends coaxially within the support tube 16, to emerge radially outside the end plate 18. The top end of the support tube 16 is closed and provided with a lifting ring 23.

The heat exchange assembly 14 comprises a tubular cylindrical mandrel 25 surrounded by an annular heat exchange matrix 26 described below. At each end the assembly includes a cross-shaped header 28 (see Figure 2), the header 28 at one end having the arms of the cross oriented mid-way between the orientation of the arms of the cross of the header 28 at the other end. The top header 28 communicates with the support tube 16; the bottom header 28 communicates via the mandrel 25 with the coaxial tube 22.

The matrix 26 provides ducts for fluid flow parallel to the longitudinal axis of the assembly 14 between the two headers 28. Hence in operation a coolant fluid such as water caused to flow into the tube 21, flows along the support tube 16 to the top header 28, through the heat exchange matrix 26 to the bottom header 28, and out through the mandrel 25 and the coaxial tube 22 (as indicated by arrows Q).

Referring now to Figure 3, which shows to a larger scale and in more detail the part of the assembly 14 indicated by A in Figure 1, the heat exchange matrix 26 consists of two long rectangular stainless steel plates 30, 31 each 0.25 mm thick, wound onto the mandrel 25 so as to form two multi-turn spirals; woven wire mesh spacers 32 (shown diagrammatically for the first turn only) are arranged between adjacent plates 30 31 throughout the matrix 25 to maintain a radial separation of 3 mm. The plates 30, 31 thus define two passages 33 and 34 for fluid flow, each passage 33 and 34 being of spiral shape in cross-section. The edges of the plates 30,31 are spaced apart by discontinuous sealing strips 36, 37 which are welded to the plates 30, 31, leaving gaps 38, 39 between successive sealing strips 36, 37 around any one turn of the spiral.Referring also to Figure 4 the gaps 38 communicating with the passage 33 are circumferentially staggered with respect to the gaps 39 communicating with the passage 34. Around each turn of the spiral are four gaps 39 which communicate with the arms of the header 28 (see Figure 2). Similarly, around each turn of the spiral are four gaps 38 which communicate with the pipe 10 between the arms of the header 28.

Thus in operation both gas and liquid flow in a generally axial direction through the heat exchange matrix 25, though their flows are in countercurrent. The gas flows through the gaps 38 and so through the passage 33, whereas the liquid flows through the gaps 39 and so through the passage 34.

It will be apparent that the heat exchange assembly 14 described above can provide a very large heat exchange surface area. For example if the assembly 14 is 2.0 m long, and of external diameter 0.60 m, and the mandrel 25 is of external diameter 0.25 m, then the heat exchange surface area is more than 140 m2. Thus the assembly 14 provides a heat exchange area of just over 250 m2/m3.

It will be appreciated that the heat exchanger of the invention may be modified in a variety of ways. For example the pipe 10 might be provided with means projecting from its wall onto which the bottom header 28 could rest, so that the weight of the assembly 14 is not taken solely by the support tube 16. The headers might be of a different shape, for example with three equally spaced arms, or six equally spaced arms, or with arms which are not straight (the gaps 39 being in appropriate positions accordingly). Indeed there might be a different number of plates: if there were three plates wound into a spiral as described above they would define between them three spiral passages, so that (if suitable headers were provided) a gas could be arranged to exchange heat with two separate fluid flows.

Claims

1. A heat exchanger comprising at least two spirallywound plates defining a generally annular heat exchange matrix, adjacent plates in the matrix being spaced apart radially so as to define at least two ducts for fluids, and at each end of the matrix the edges of adjacent plates being sealed together leaving at least one gap communicating with each duct for each turn of the spiral, the gaps communicating with one duct being circumferentially staggered with respect to the gaps communicating with another duct in an adjacent turn of the spiral.

2. A heat exchanger as claimed in Claim 1 wherein the gaps communicating with one duct at one end of the matrix lie on generally radial lines, and the heat exchanger comprises one or more headers at that end communicating with the said gaps.

3. A heat exchanger as claimed in Claim 1 or Claim 2 wherein the heat exchanger also comprises a cylindrical core or mandrel for the heat exchange matrix, and a cylindrical pipe or pressure vessel in which the matrix locates.

4. A heat exchanger as claimed in any one of the preceding Claims wherein the plates are held apart by separators, or are ridged to define fins, or are corrugated, the separators, fins or corrugations being arranged to constrain the fluid flows along particular desired paths.

5. A heat exchanger as claimed in any one of the preceding Claims adapted to form part of a pipeline, and being of the same diameter as the pipeline.

6. A heat exchanger as claimed in any one of the preceding Claims which is a compact heat exchanger, providing more than 100 m2/m3 of heat transfer surfaces, preferably more than 200 m2/m3.

7. A heat exchanger substantially as hereinbefore described with reference to, and as shown in, the accompanying drawings.

8. A method of making a heat exchanger substantially as hereinbefore described with reference to, and as shown in, the accompanying drawings.