JPH0256594B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a multi-tubular cylindrical falling film heat exchanger. More particularly, the present invention relates to an improved heat exchanger having a plurality of tubes arranged in radially concentric circles and means for uniformly distributing the feed liquid to the tubes.

BACKGROUND OF THE INVENTION A multitubular cylindrical heat exchanger has a large number of tubes that extend between and through two spaced apart tube sheets surrounded by a shell. The shell is provided with an inlet and an outlet so that a suitable heat exchange liquid or gas can be circulated through the shell to cool or heat the liquid flowing through each tube.

Each end of the plurality of tubes may be open or exposed and used for some processing operation. In another application, one or both ends of the tube may be surrounded by a liquid storage header, which may be fitted with a removable cover or access port. If there is only one liquid header, it can be used as a liquid inlet or a liquid outlet. If headers are placed at both ends, one header can constitute the liquid inlet and the other can serve as the liquid outlet. The above is the arrangement of a conventional single superheat exchanger or single flow heat exchanger. The liquid inlet header and the liquid outlet header, or parts thereof, are provided with suitable conduit means for supplying and removing liquid.

Shell-and-tube cylindrical heat exchangers are typically used for heating feed streams, but can also be used for cooling streams. Multi-tubular cylindrical heat exchangers of the type described here can be used as freezing exchangers, for the production of fresh water from brine and seawater, for the concentration of fruit and vegetable juices, and for industrial crystallization processes. As the liquid flows through each tube, it is cooled sufficiently to precipitate solids from the liquid. This cools seawater and produces ice,
It is separated, washed and melted to obtain drinking water.
Similar cooling of fruit or vegetable juices results in the formation of ice, which is removed to yield concentrated juices.

On the shell side of the heat exchanger of the type described here,
Any cooling liquid can be used to cool the liquid flowing through the tubes. Liquid is supplied from one end of the heat exchanger and removed from the other end, but the flow is generally unidirectional. Suitable coolants include ammonia and Freon refrigerants.

For optimal heat exchange, it is often desirable to have the tubes arranged vertically and have the feed liquid applied to the tube surface be a falling or descending liquid film.
This not only allows the feed liquid to approach the temperature of the heat exchange liquid more quickly, but also reduces the need for liquid recirculation and reduces energy consumption.

Although it has been recognized that it is desirable to control the thickness of the falling film to obtain the highest heat exchange efficiency, commercially available equipment has not generally produced acceptable results, and The cost and complexity of the system exceeded the requirements. Therefore, U.S.
Patent No. 4,335,581 discloses a heat exchanger in which short tubes fit loosely into the open tops or openings of the heat exchanger tubes so that the feed fluid flows only between the tubes. However, while such equipment provides good results for small heat exchangers, it is not desirable for deployment in large heat exchangers.

Typically, the heat exchangers are arranged generally adjacent to each other in rows parallel to the diameter of the tubesheet. If the tube tops are flush with the top surface of the upper tubesheet, the liquid supplied to the top of the tubesheet will generally not be evenly distributed to each tube opening, resulting in inconsistent falling film thickness and flow rate. This has a negative impact on heat exchange efficiency.

The top of the tube was extended 24 inches from the tubesheet surface to improve liquid distribution to the tube. Although this improved liquid distribution to the tubes somewhat, it did not provide satisfactory results because it did not allow flow control of all tube openings when the liquid was supplied from one or two locations.

Therefore, there is a need for an improved multi-tube cylindrical falling film heat exchanger that has a means for controlling the liquid supply flow rate to consistently supply a substantially uniform amount of liquid to each tube.

Structure of the Invention The falling film heat exchanger provided in accordance with the present invention includes: a shell connected to vertically spaced horizontally arranged circular upper and lower tube sheets; installed in a plurality of concentric circles; a plurality of vertically installed parallel tubes extending through and connected to the holes in each tubesheet; devices for supplying and extracting heat exchange fluid from the shell side of the heat exchanger; surrounding the top of the shell; a wall joined to said wall for storing a liquid layer on the upper tube sheet at a depth equal to or greater than the upper end of the tube; a liquid distributor located on the upper tube sheet, having a bottom and a peripheral wall extending upward; Box: A short tube extending downward from the liquid distribution box and allowing the liquid inside the box to flow onto the tube sheet, located in a plurality of concentric circles, the concentric circles extending from the inner adjacent short tube circle to the upper tube sheet. short tubes adapted to be spaced radially outwardly by a distance approximately equal to the radial distance between the circles of the tubes; and means for supplying a feed liquid to the liquid distribution box. The circles of each short tube are aligned radially so as to alternate with the circles of the tubes, and the circles of the short tubes are aligned midway between adjacent tube circles.

It is desirable that the height of the upper end of the tube be equal to the height above the upper tube sheet, and that the lower end of the short tube be below the upper end of the tube.
However, the lower end of the short tube may be equal to or higher than the upper end of the tube.

The distribution box of this falling film heat exchanger is fixed, but can be mounted such that the tubes are fixed and the distribution box rotates about a vertical axis.

The distribution pipe can be made of metal or polymeric material. If it is made of metal, the area around the distribution pipe can be insulated.

The liquid distribution box can be insulated by including a bottom and perimeter wall of polymeric material. In such a box,
The tube may be made of a polymeric material and protrude downwardly from the polymeric bottom. The sole is made of polymer material,
It can be supported on a metal plate with larger holes through which the polymeric material tube passes.

To minimize corrosion, the bottom of the distribution box can be made of metal from which the metal anode extends downwardly and projects between a ring at the top of the tube that extends above the plate of the top tube.

A seal may be provided between the distribution wall and the peripheral wall of the top to prevent vapor from flowing around the liquid distribution pipe. This prevents ice formation when the device is used as a freeze exchanger.

DETAILED DESCRIPTION OF THE EMBODIMENTS Identical or similar elements or parts in the drawings may include:
Use identical numbers to the extent reasonable and practical.

In FIG. 1, heat exchanger 10 has a vertical cylindrical metal shell 12 that connects to an upper tube sheet 14 and a lower tube sheet 16. In FIG. The conical end 18, which connects to the lower end of the shell 12, is provided with an outlet connection 20 through which liquid is removed from the tube side of the heat exchanger 10. The heat exchange liquid passes through the connection port 22 and enters the heat exchanger 1.
0 and is removed from the upper connection port 24. A peripheral wall 26 extends upwardly from the end of the upper tubesheet 14.
(FIGS. 1 and 2) extends, and an overflow liquid drain pipe 28 is attached thereto.

A plurality of parallel, vertical heat exchange tubes A- are typically of the same size and project through the tube sheets 14 and 16. This tube is press-fit into a hole in the tubesheet to form a watertight connection. All of tube A- are concentric circles (Figure 3)
will be placed in In other words, multiple tubes A are placed in one circle, multiple tubes B are placed in a second concentric circle with a larger radius, and multiple tubes C are placed in a third concentric circle with a larger radius than the circle containing tube B. In this way, the outermost concentric circle containing the plurality of tubes is arranged. It is desirable that the intervals between a set of adjacent circles be the same. However, since it is desirable that each tube be arranged at equal intervals from each adjacent tube, regardless of the circle to which it belongs, the number of tubes in each circle generally increases as the circumference increases.

The upper end or top portion 30 of tube A- is connected to upper tube sheet 1
4, extending slightly above the top surface, e.g., 5.1 cm (2 inches). Circular and lateral plane block 3
2 is installed in the axial direction on the tube sheet 14. The block 32 projects slightly from the top 30 of the tube and forms a liquid bank for restricting liquid from flowing out into the top 30 of the tube and the drain pipe 28.

Two to four or more diametrically opposed vertical legs 34 (only one shown in FIG. 1).
is supported on a bracket 36 connected to the top of the barrel 12. A horizontal drive support arm 38 is supported radially from the top of the leg 34. Drive mechanism 40
is mounted on arm 38 and rotates about vertical axis 42, for example at about 1 RPM. A hub 44 attached to the lower end of shaft 42 is axially attached to a horizontal circular base plate 46 spaced above tubesheet 14 . A vertical cylindrical wall 48 is connected to the periphery of the bottom plate 46 and projects upwardly therefrom. bottom 46 and wall 48
forms a liquid distribution box 50. An inwardly facing ring flange 52 is attached to the upper end of the wall 48 to prevent liquid from splashing.

The bottom plate 46 of the liquid distribution box 50 is provided with a series of radially concentric holes, which concentric circles are preferably equally spaced radially from adjacent concentric circles. Typically, most or all of the holes are fitted with liquid distribution pipes D1-D10 extending downwardly, as shown in FIGS.
The lower liquid distribution end 54 is located slightly above the top surface of the tubesheet 14.

The circle containing the plurality of distribution pipes D1 is a concentric circle radially inner to the circle containing the pipe A, and the concentric circle containing the plurality of distribution pipes D2 is concentric with the circle of the pipe A and the circle of the pipe B, It is located between them. In this way, the concentric circles including the plurality of distribution pipes D10 are
Located close to and outside the circle containing the tube.
A distribution box having a distribution pipe arranged as described above is free to rotate together with the distribution pipe without being obstructed by the upper end of the pipe. (Figures 1-3).

One or more inlet liquid supply conduits 56 are provided to supply liquid to the distribution box 50. Also,
If the temperature of the feed liquid is significantly higher or lower than the outside temperature, a heat insulating layer 58 is installed on the lower surface of the distribution box bottom 46.
(Figure 2) is often desirable.

The heat exchanger shown in FIGS. 1 and 2 is particularly useful as a freeze exchanger or freeze exchanger, and is especially useful for concentrating aqueous solutions and dispersions. For example, by supplying seawater to the distribution box 50,
Can be used for freezing and concentrating seawater. Seawater flows to the top surface of tube sheet 14 through the circle of distribution pipes D1-D10. When the liquid level on the tube plate reaches the tip 30 of the tube,
The liquid overflows into the tube as a falling thin film. This thin film of salt water is indirectly cooled by heat exchange with the ammonia liquid on the shell side. This cools the salt water sufficiently, leading to the formation of ice crystals in the water. The formed ice and water slurry flows from the tube to the conical end 18 and exits through the outlet connection 20. This slurry is recycled to the distribution box 50 to increase the amount of ice before being sent to the separator.
Remove the ice from the concentrated brine. Drinking water can be obtained by cleaning and melting ice.

Use of the above-described device allows liquid to be more uniformly supplied to each tube than by supplying liquid directly from conduit 56 onto tube sheet 14. Although this result can be obtained by fixing the distribution box 50, better results are usually obtained by rotating the distribution box 50.

When the device is used as a freeze exchanger, it is desirable to cover the external surfaces of distribution pipes D1-D10 with a polymeric insulation layer 60, as seen on pipe D9 in FIG. 4, to prevent ice formation on the pipes. Polyethylene, nylon, and epoxy polymeric materials are suitable for this purpose.

FIG. 5 shows a second embodiment of a liquid distribution box that can be used in the device of the invention. Distribution box 70 has the metal bottom 46 and walls 48 previously mentioned. However, a circular plate 72 of polymeric insulation material is attached to the top of the bottom 46. A vertical wall 74 of polymeric insulation material projects upwardly from the periphery of plate 72. A polymeric distribution tube 76 extends downwardly from the plate 72 through a larger hole 78 in the metal base 46. Distribution tubes 76, like tubes D1-D10, are arranged concentrically so that the feed fluid flows between the concentric upper ends of the tubes. Distribution box 70 is particularly useful when the device is used as a freeze exchanger.

In either case, the lower end 5 of the distribution pipes D1-D10
4 protrudes below the upper end of tube A-.
Not a necessary condition. In some heat exchangers, the lower ends 54 of the distribution tubes may be flush with or slightly above the upper ends 30 of the tubes to distribute liquid into the tubes, as shown in FIG.

When the apparatus of the present invention is used to treat corrosion-inducing liquids such as seawater, the anode is suitably positioned and anodic protection applied by passing electrical current in any suitable manner well known in the art. As shown in FIGS. 7 and 8, among any suitable number of circular tubes,
By replacing several distribution pipes D1-D10 with metal anode rods 80, a sufficient number of anodes can be installed. The bottom 82 of each anode rod 80 can be widened to improve the anodic protection effect.

Air outside the heat exchanger flows into the space between the tube sheet 14 and the bottom 46 of the distribution box, and the distribution box is used to prevent water vapor from condensing and freezing on the tubes and tube tips in that space. wall 48 and extension 92 of wall 26
It is practical to provide a seal 90 between the two. The seal used is preferably one that allows the distribution box 50 to rotate while the wall extension 92 remains stationary. The construction of such seals is well known to those skilled in the art.

[Brief explanation of the drawing]

FIG. 1 is a partial elevational view, partly cut away and partly in section, of a heat exchanger according to the invention. FIG. 2 is an enlarged elevational view, partially in section, of the heat exchanger of the present invention, showing several liquid distribution pipes and the tops of the pipes. FIG. 3 is a partial plan view of the top of the upper tube sheet and the upper ends of the tubes of the heat exchanger shown in FIGS. 1 and 2. FIG. FIG. 4 is a partial elevation view, partially in cross section, of an insulated liquid distribution pipe. FIG. 5 is a vertical cross-sectional view of a second embodiment of a liquid distribution box that can be used in the heat exchanger of FIG. FIG. 6 is an elevational view showing the liquid distribution pipe, partially in section. The lower end of this liquid distribution pipe terminates slightly above the upper end of the heat exchanger.
FIG. 7 is an elevational view, partially in section, showing the metal anode projecting downwardly from the bottom of the distribution box. 8th
The figure is a side view taken along line 8--8 of FIG. 7.
FIG. 9 is an elevational view, partially in section, showing a steam seal covering the gap between the distribution box wall and the heat exchanger wall extending above the tube top;

Claims (1)

[Scope of Claims] 1. A falling film exchanger comprised of the following elements: a. vertically spaced, horizontally arranged circular upper and lower tube sheets, and cylinders connecting the upper and lower tube sheets; b. parallel tubes, each tube extending through a hole in each tube sheet and connecting to the tube sheet; c. means for supplying heat exchange liquid to the shell side of the heat exchanger and for supplying heat exchange liquid to the shell side; c. d. A wall surrounding the top of the body and connected to the top of the body, for storing a liquid layer on the upper tube sheet at a depth deeper than the upper end of the tube; e. above, a liquid distribution box having a bottom and an upwardly extending peripheral wall; f a plurality of short tubes extending downwardly from the liquid distribution box for fluidly passing liquid from inside the box onto the upper tube plate; The tubes are arranged in a plurality of concentric circles spaced outwardly from the rings of the short tubes adjacent to the inner side by a distance equal to the radial distance between the rings of tubes in the upper tubesheet. a plurality of short tubes arranged and radially aligned such that each ring of short tubes is alternating with the rings of tubes, with a ring of short tubes being located between adjacent rings of tubes; ; g Device for delivering the feed liquid to the liquid distribution box. 2. A falling film heat exchanger according to claim 1, in which the upper ends of the tubes extending above the upper tube plate have the same height, and the lower ends of the short tubes are lower than the upper ends of the tubes. A falling film heat exchanger. 3. A falling film heat exchanger according to claim 1, which has means for fixing the tubes and for attaching the liquid distribution box to rotate around a vertical axis. exchanger. 4. The falling film heat exchanger according to claim 1, wherein the short tube is made of metal and the outside of the short tube is insulated. 5. A falling film heat exchanger according to claim 1, wherein the liquid distribution box has a bottom and a surrounding wall made of a polymeric material, and the liquid distribution box has a bottom made of a polymeric material and a surrounding wall made of a polymeric material, and the polymeric material is A falling film heat exchanger with a short tube made of aluminum that protrudes downward. 6. A falling film heat exchanger according to claim 5, wherein the bottom made of a polymeric material is placed on a metal plate having a larger hole for passing a tube made of a polymeric material. Supported falling film heat exchanger. 7. The falling film heat exchanger according to claim 1, wherein the distribution box has a metal bottom, and the metal anode extends downward from the metal bottom and connects to the upper tube. A falling film heat exchanger that is inserted between the rings at the top of the tubes that extend above the plate. 8. A falling film heat exchanger according to claim 3, in which there is a structure between the distribution wall and the wall around the top of the body to prevent steam from flowing around the liquid distribution pipe. Falling film heat exchanger with seal.