GB2087532A - Heat exchangers - Google Patents

Abstract

The heat exchanger has a housing defined by a casing 10 and end assemblies defined by a collar 11, 12 and a respective end cap 13, 14. Tubes 19 extend through the housing and communicate with an inlet 26 and an outlet 27 defined by the end caps 13 and 14 respectively. A radial inlet 28 and a radial outlet 29 are provided in the collars 11 and 12, respectively. Baffles 31 and 33 are of semi- cylindrical shape and are defined by extensions of the casing 10. These baffles 31 and 33 are spaced inwardly of the inlet 28 and outlet 29 respectively and define openings which are circumferentially spaced from the inlet 28 and outlet 29. The incoming stream of fluid impinges against the baffle 31 so that erosion effects are largely dissipated. The baffle 33 is provided to serve the same effect in the event that the flow is reversed so that the roles of the inlet 28 and outlet 29 are reversed. <IMAGE>

Description

SPECIFICATION Heat exchangers This invention relates to heat exchangers of the kind comprising a housing having an inlet and an outlet for one fluid and a bundle of tubes within the housing connected with chambers having respective inlet and outlet for a second fluid. Heat exchange takes place between the two fluids as the first fluid flows around and between the tubes, while the second fluid flows through them. Such a heat exchanger will be referred to, for convenience, as being of the kind specified.

One problem with such heat exchangers is that the flow of the fluids, at high velocity, cause erosion particularly in the inlet and this erosion is especially severe if the fluid contains solids or, if gaseous, contains liquid droplets.

To overcome this, or to reduce the effect, there have been baffles fitted into the region just inside the heat exchanger inlets, these baffles taking the full velocity pressure of the incoming fluid and dissipating its force, so that the velocity of particles or droplets is decreased.

In existing heat exchangers these baffles have been local to the inlets and have intruded into the interior of the housing, thus limiting the number of tubes which can be fitted in the interior.

The object of the invention is to provide a heat exchanger of the kind specified in which the erosion effect of fluid flow into and through the heat exchanger is minimised.

According to the present invention there is provided a heat exchanger of the kind specified, characterised in that the housing is of generally circular section, an inlet for one of the fluids to flow around and between the tubes extending generally radially of the housing, a baffle being disposed in the housing at a position aligned with the said inlet, and extending around the interior of the housing, over at least half the circumference of the housing and spaced from the interior surface thereof, the baffle defining at least one opening for flow of the fluid to the spaces between the tubes, said opening being circumferentially spaced from the radial position of the inlet.

The invention will now be described by way of example with reference to the accompanying drawings in which Figure 1 is a longitudinal view partly in crosssection of a heat exchanger constructed in accordance with the invention, Figure 2 is a cross-sectional view bn the line 2-2 in Figure 2 and Figure 3 is a cross-sectional view on the line 3-3 in Figure 1.

The heat exchanger comprises a cylindrical sheet metal casing 10 to which are attached two end assemblies. Each end assembly comprises a collar 11,12 and an end cap 13, 14. The end caps are secured to the collars by respective bolts one of which is indicated at 1 5. The collars 11, 12 and end caps 13, 14 are castings and each has a drain plug 16, 17 engaged in a threaded hole normally at the bottom of the heat exchanger.

Within the casing there are a number of spaced perforated baffles 1 8. These are arranged to extend partially across the interior of the casing and are arranged alternately at opposite sides of the centre of the casing. Passing through the interior of the casing are a number of tubes 1 9.

The close packing of these is shown in Figures 2 and 3 but there are spaces defined between them for the flow of fluid as will be described.

Connecting one of the baffles 1 8 nearest to the end at which the collar 1 2 is located with the other collar 11 at the other end of the heat exchanger is a tie rod 21. This is surrounded by a spacer sleeve and it has threaded ends. One threaded end engages in the end wall of the collar 11 and the other carries a nut 22. A further tie rod 23 connects the baffle nearest to the collar 11 with the other collar 12.

The ends of the tube 19 are secured into the end walls of the collars 11 and 12 respectively so that the interiors of the tubes are isolated from the space surrounding the tubes between the collars.

However, the tube ends open into chambers 24, 25 defined within the end caps 13 and 14 respectively. Furthermore these end caps have concentric threaded openings representing an inlet 26 and an outlet 27 respectively.

The collars 1 1 and 12 have respective radially extending openings defining an inlet 28 and an outlet 29 respectively. Within each of the collars 11 and 12 is a baffle which is formed by the end portion of the cylindrical casing 10. The baffle in the collar 11 is shown in figure 2 and identified by numeral 31. It is formed by leaving a semicylindrical extension at the end of the casing 10. It is situated with the centre of the semi-cylinder adjacent to the radial inlet opening 28 as seen in figure 2. The arrangement in use is that fluid flowing in through the inlet 28 will impinge on the baffle 31 and the main force of the incoming liquid will be dissipated by such impingement. The fluid will then flow around the space 32 defined between the baffle 31 and the interior of the collar 11. The flow is limited lengthwise of the heat exchanger by the width of the collar 11.The fluid will flow into the spaces between the tubes 1 9 but can only reach this area by having flowed around the space 32 between the collar 11 and the baffle 31. Arrows in figure 2 indicate the directions of fiow. The fluid will then flow along the length of the heat exchanger being deflected by the baffles 1 8 so as to create a maximum contact between the fluid and the tubes 1 9. Outlet occurs through the collar 11 which is similarly provided with a baffle 33 to define a space 34. Although it is not so necessary in the case of the outlet to provide the baffle this configuration enables the heat exchanger to be used with flow in either of two opposite directions.

A second fluid flows through the inlet 26 in the end cap 13 through the tubes 1 9 and then into the opposite end cap 14 and through the outlet 27.

The heat exchanger can be used for liquids or mixtures of liquids or gasses and is capable of handling liquids containing solid particles the erosion effect of which will be largely dissipated by means of the baffles particularly that just inside the inlet 28.

In an alternative construction the baffles are in the form of complete cylinders being extensions of the casing 10. There is defined by the collar 11 or 12 a space 32 or 34 surrounding such baffle and the baffle has a series of spaced openings through which fluid can flow into the space occupied by the tubes 1 9. None of the openings however are opposite to the radial inlet opening 28 or outlet opening 29. The size shape and distribution of the openings in such baffles are calculated to minimise resistance to flow while providing maximum distribution of the fluid and effective dissipation of the force due to the incoming stream of fluid.

In a further alternative construction the baffle 31 or 33 is formed as a separate component from the casing 10. The construction of the casing and collars 11, 12 may be different from that shown for example being a complete housing formed as one part instead of the composite housing shown.

In addition to dissipating the erosion effect, as mentioned above, the baffles also create an improved distribution of flow across the tube bundle, thereby improving the exchange of heat.

Claims (7)

1. A heat exchanger of the kind specified, wherein the housing is of generally circular section, the inlet for the first fluid extends generally radially of the housing and a baffle is disposed in the housing at a position aligned with the first fluid inlet and extending around the interior of the housing over at least half the circumference of the housing and spaced from the interior surface thereof, said baffle defining at least one opening for flow of the fluid to the spaces between the tubes, and said opening being circumferentially spaced from the radial position of the inlet.

2. A heat exchanger as claimed in claim 1, wherein a further baffle is disposed in the housing at a position aligned with the first fluid outlet and extending around the interior of the housing over at least half the circumference of the housing and spaced from the interior thereof, wherein the outlet for the first fluid extends generally radially of the housing, and wherein the further baffle defines at least one further opening for flow of fluid between said spaces and said first fluid outlet, said further opening being circumferentially spaced from the radial positon of the first fluid outlet, whereby the direction of flow of the first fluid through the heat exchanger can be reversed.

3. A heat exchanger as claimed in claim 1 or 2, wherein said housing is defined by a cylindrical casing and two end assemblies, and said baffle and/or said further baffle, when provided, is or are each defined by an axial extension at an end of the casing.

4. A heat exchanger as claimed in claim 3, wherein the or each extension is semi-cylindrical.

5. A heat exchanger as claimed in claim 3, wherein the or each extension is cylindrical with a plurality of openings therein.

6. A heat exchanger as claimed in any preceding claim, wherein additional baffles are provided in the housing, said additional baffles being arranged alternatively at opposite sides of the centre of the housing to deflect flow of said first fluid during its passage through the spaces between the tubes.

7. A heat exchanger substantially as hereinbefore described with reference to the accompanying drawings.