IE55000B1

IE55000B1 - Segmental baffle high performance shell and tube heat exchanger

Info

Publication number: IE55000B1
Application number: IE449/84A
Authority: IE
Original assignee: Baltimore Aircoil Co Inc
Priority date: 1983-02-28
Filing date: 1984-02-24
Publication date: 1990-04-11
Also published as: DK157707B; AU2507584A; AU562526B2; CA1218357A; ZA841421B; NZ207208A; DK105184D0; MX158862A; GR79819B; DK157707C; EP0117820B1; DE3467399D1; DK105184A; IE840449L; ATE30769T1; EP0117820A1; BR8304340A; JPS59164895A

Abstract

The invention comprises a high performance segmented baffled shell and tube heat exchanger (1) in which baffles (4, 5, 6 and 7) are oriented at angles less than 180 DEG adjacent one another.

Description

2 2 5» 5 ϋ «I Ο This invention relates to a segmental baffle high performance shell and tube heat exchanger.

In the past, several methods were used to obtain better heat transfer coefficients in shell and tube heat exchangers, briefly, these methods were 1) increasing the flow rate and increasing the pressure drop in typical shell and tube heat exchangers, 2) by increasing the heat transfer surface area in shell and tube heat exchangers, such as by using a fluted tube, or 3) by using a different type of heat exchanger than the shell and tube heat exchanger altogether, such as a plate and frame heat exchanger, which utilizes extremely narrow flow passages to enhance heat transfer. Thus, those skilled in the art continue to look for desiqns of shell and tube heat exchangers of more compact size which occupy less space and/or which lead to high overall heat transfer coefficients combined with low pressure drops over a broad range of fluid flow rates in the shell and tube heat exchangers. 3 355000 The invention relates to a high performance shell anti tube heat exchanger and a method of obtaining high overall heat transfer coefficients at low pressure drops and low flow rates in said shell and tube heat exchangers wherein the shell and tube heat exchangers utilize segmented shell-side baffles which are oriented one from the other along the line of tubes in the shell and tube heat exchanger at angles other than 180° and preferably at lesser angles such as about 90°. Further, it has been found that if one uses fluted or corrugated tubes in the shell and tube heat exchanger along with the segmented baffles being spaced adjacent from one another at angles less than 180°, along the direction of flow of the fluid within the shell, overall heat transfer coefficients are improved to a greater extent than one would expect by summing the improvements that are obtained from using (a) fluted tubes with no shell-side baffles plus (b) smooth tubes with non-180° seqmental shell-side baffles.

This is to say that one expects a given improvement in thermal overall heat transfer coefficient Uo or K when using either (a) or (b) above rather than smooth tubes in a 180° segmentally baffled heat exchanger. However, the unexpected findinq is that the given improvement in K when using both (a) and (b) simultaneously is greater than the sum of individual improvements (a) plus (b).

Thus, it is an object of this invention to obtain high overall heat transfer coefficients at low pressure drops and low fluid flows in shell and tube heat exchangers by using a shell and tube heat exchangee having segmented shell-side baffles therein which are oriented at angles less .than 180° -adjacent each other and along the flow direction of the fluid within the shell of said shell and tube heat exchanger.

It is a further object of this invention to provide a heat exchanger which eliminates or reduces U>e amount of tube vibration that may exist due to tube support baffle peripheral clearance tolerances.

Accordingly, the present invention provides a shell and tube heat exchanger comprising: a) an outer shell; b) a plurality of tubes within said shell; c) a series of circular segmental baffles forming a partial barrier to liquid flow each having holes therethrough for blocking the fluid flow around the tubes passing through said holes, said baffles being spaced axially along said tubes within said outer shell and being oriented such that a twist angle is formed by the diameter or chord line of one baffle and the diameter or chord line of an adjacent baffle in said series of baffles, said twist angle appearing between adjacent baffles arranged with the same torsion of angle, the tubes being continuously fluted along substantially the complete tube length, each baffle having a -segmented baffle angle of about 180°, and said twist angle between adjacent baffles being about 90°.

This combination improves considerably the heat transfer coefficients, due to a highly effective combination of wave-like undulating flow and rotating helical flow.

According to a preferred embodiment of the present invention, the baffles are located a distance apart of at least 0.7 times the diameter of the baffle but not greater than 6 times the diameter of the baffle. With such a space between adjacent baffles, a natural spiral and wave-like pattern of fluid flowing through the shell and tube heat exchanger is easy to form.

To better describe the invention there are included herein Figures l;and 2.

Figure 1 shows a cutaway view of a typical shell and tube heat exchanger with the segmented baffles therein, and Figure 2 shows the same cutaway view of the baffles and shell without the individual tubes of the shell and tube heat exchanger.

Referring now to Figures 1 and 2, a central portion 1 of a typical shell and tube heat exchanger is shown. Typical flanges for enclosing the shell ends, inlet and outlet piping portions and tube sheets or tube end walls are not shown in the diagram but would be well known to those skilled in the art. This heat exchanger consists of a housing or shell portion 2 shown in cutaway views having therein a plurality of fluted tubes 3. These tubes can be arranged within the heat exchanger in a typical spaced pattern, and the number and size of the tubes 6 will vary depending on the type of heat exchanger one is using. The fluid or material to be cooled is typically, though not necessarily always, within the shell 1_ of the heat exchanger 1 flowing in one direction whereas the heat exchange fluid inside of the tubes 3 flows in the opposite direction. Also, the tubes .3 are continuously fluted 9_, along substantially the complete tube length, except for each tube end J5, where the tube surface is smooth to permit a proper seal or tube end attachment to a separating tube end wall at the ends of tubes which encloses and seals the outside of all tube ends from the outer shell region 10.

Located within the shell and tube heat exchanger £ are a plurality of segmented-circular baffles £, £, £, and £. These baffles are in the form of a circular segment having an arc of 180° (segmented baffle angle). These baffles are provided in the heat exchanger 1 such that adjacent haffles are oriented at an angle of 90°C (twist ancle) as illustrated in the Figures. The baffles are constructed with holes such that they fit snugly over the plurality of tubes 3 provided within the heat exchanger and would prevent the flow of fluid outside the tubes where the baffle is located since the baffle forms a wall against fluid flowing in the direction of the baffle, thereby causing a rotating flow direction or a combination rotating flow with undulating flow pattern.

As can be seen in Figure 2, the plurality of baffles £ through £ ate oriented at an angle of 90° from each other in such a way so that fluid flowing within the shell 2 forms a helical spiral configuration (shown as 815) as it flows along. In addition 7 55000 to forming a helical spiral fluid flow (β15) a poll ion ol the fluid also flow;; in The baffles can be constructed of any material such as for example metal or other material which preferably is noncorrosive to the fluid flowing therethrough.

Although the segmented baffle angle of the baffles is shown in figure 2 as 180°, one skilled in the art would realize that any segmented baffle angle slightly more or less than 180° would be satisfactory, with a variation of some degrees from the precise value of 180°.

Furthermore, although the angles at which the baffles are oriented one from the other are shown in figure 2 as 90°, one skilled in the art would realize that any twist angle slightly more or less than 90° would be satisfactory, with a variation of some degrees from the precise value of 90°.

The particular 90° twist angle is shown in figure 2 such that if one takes baffle 4 with one side of the angle as the diameter line 60 which is an extension of the diameter line of the baffle (9), and one takes the diameter or chord line of the next adjacent baffle 5 (shown as line 61), it can be seen that the twist angle of difference thereto is 90°.

This follows similarly with baffles 5 and 6 where the twist angle is also 90° taken as an extension of the diameters of the adjacent baffles.

The baffles are spaced apart in the shell and tube heat exchanger at such a distance as to provide a natural spiral helical and wave-like flow path of any fluid therethrough. The baffles must be located a distance apart at least 0.7 times the diameter of the baffle or shell but not greater than 8 8 5 5 Ο Ο () 6.0 times the diameter of the shell and cannot be at such a close or extremely far distance so that any spiral and wave-like pattern of fluid flowing therethrough would be difficult to form.

These baffles have an outside diametric clearance to fit within the shell with ease.

However, it should be noted that the baffles are not physically attached to the inside wall of the shell, but rather held in position axially by rods (not 10 shown) which parallel the tubes. Therefore, it is conceivable that the baffles can vibrate within the shell due to the clearance tolerances. It is further important to note that segmental baffles at 180° twist positions as shown at figure 8 of US Patent 15 Specification No. 3 696 863, could vibrate over a greater distance in the direction perpendicular to the straight cut segment side, than in any other direction.

Therefore, orienting each second baffle at about 90° will prevent vibration in the assembly by means of 20 alternate supporting baffle orientation of the straight edge.

The above description refers to an illustration of the invention and is not intended to be limitative thereof. For example, the invention includes consideration for any generic type of segmental baffle, such as single, double, 25 triple, or any multiple-segmental baffle component.

Claims

9 9 55000

1. A shell and tube heat exchanger comprising: a) an outer shell; b) a plurality of tubes within said shell; c) a series of circular segmental baffles forming a partial barrier to liquid flow each having holes therethrough for blocking the fluid flow around the tubes passing through said holes, said baffles being spaced axially along said tubes within said outer shell and being oriented such that a twist angle is formed by the diameter or chord line of one baffle and the diameter or chord line of an adjacent baffle in said series of baffles, said twist angle appearing between adjacent baffles arranged with the same torsion of angle, the tubes being continuously fluted along substantially the complete tube length, each baffle having a segmented baffle angle of about 180°, and said twist angle between adjacent baffles being about 90°.

2. A shell and tube heat exchanger according to claim 1, wherein the baffles are located a distance apart of at least 0.7 times the diameter of the baffle but not greater than 6 times the diameter of the baffle.

3. A shell and tube heat exchanger according to Claim 1, substantially as hereinbefore described with particular reference to and as illustrated in the accompanying drawings. F.R. KELLY & CO., AGENTS FOR THE APPLICANTS.