JPS60228894A - Flow down liquid film type heat exchanger - Google Patents

Abstract

PURPOSE:To obtain the multi-tube cylindrical flow-down film type heat exchanger capable of controlling the thickness of flow-down liquid film in order to obtain the highest heat exchanging efficiency by a method wherein a means, covering an inner circular area for distributing liquid supplied on an upper tube plate along the inner surface of respective tubes as thin flow-down films, is provided in the heat exchanger. CONSTITUTION:A liquid permeable porous plate 24, as the means covering the inner circular area, is supported on the top of the tube plate 12. The lower surface of the porous plate 24 is covered or coated by the circular layer 26 of liquid impregnatable material. The circular layer 26 is provided with a diameter slightly smaller than the inside of a tube 17 thereby making a small annular area so that the supplying liquid in a supplying liquid casing 20 contacts with the surface of the inside of the tube 17 and flows down as a thin film. The porous plate 32 is attached to the top of a separate plate 26' having larger holes 30. Heat exchanging liquid in a heat exchanging liquid casing 28 flows through the porous plate 32, passes through the annular clearances between the holes 30 and the tubes 17 and flows out downwardly under adhering to the surfaces of the tubes 17 as the thin films. In order to improve the heat exchanging efficiency, it is preferable generally to control both of the supplying liquid film and the heat exchanging liquid film simultaneously.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a multi-tubular cylindrical falling film heat exchanger, in particular, to a multi-tubular cylindrical falling film heat exchanger, in which a feed liquid and a heat exchange liquid are distributed over tube surfaces for efficient heat exchange. The present invention relates to an improved heat exchanger having means for

BACKGROUND OF THE INVENTION A multitubular cylindrical heat exchanger has a large number of tubes that extend between and pass 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 can be circulated through the shell to cool or heat the liquid flowing through the tubes.

Each end of the tube array can be opened or exposed for use in several processing operations. For alternative operations, one or both tube ends may be surrounded by a reservoir or sump header, which may include a removable cover or access port. If there is only one reservoir or header, it can be either an inlet reservoir or header, or an outlet reservoir or header. When liquid cylinders or headers are located at both ends, one liquid cylinder or header constitutes a liquid inlet, and the other forms a liquid outlet.

These are conventional one-pass or single-pass heat exchanger arrangements. The liquid inlet cylinder or header and the liquid outlet cylinder or header, or parts thereof, are provided with suitable conduit means for liquid supply and removal.

Multi-tube cylindrical heat exchangers are commonly used for feed pre-fed applications, but can also be used for liquid stream cooling.

Multi-tubular cylindrical heat exchangers of the type described herein can be used as coupled exchangers, such as in the production of fresh water from brine and seawater, in the concentration of fruit and vegetable juices, and in industrial crystallization processing. The liquid is
It flows through multiple tubes and is sufficiently cooled to precipitate a solid.

This cools seawater, obtains ice, and separates it.
For example, drinking water can be obtained by washing and dissolving. When fruit or vegetable juices are similarly cooled, they form ice which can be removed to obtain concentrated juice.

A heat exchanger of the type described herein can use any cooling liquid on its shell side for cooling 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 approximately unidirectional. Suitable coolants include ammonia and Freon brand refrigerants.

For optimum heat exchange, it is often desirable to arrange the tubes vertically and to supply one or both of the feed liquid and the heat exchange liquid to the tube surface as 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 for some time that it is desirable to control the falling liquid film thickness to obtain the highest heat exchange efficiency, conventional equipment has not generally produced acceptable results and The cost and complexity were greater than required. Therefore, Na1l U, S, patent No. 4
．． No. 33-5.581 describes a heat exchanger in which short tubes are loosely fitted into the open tops or mouths of the heat exchanger tubes so that the feed liquid flows down only between the tubes. Such equipment is
Although it provides good results for small heat exchangers, its placement in large heat exchangers is undesirable. Therefore, there is a need for an improved multi-tube cylindrical downstream liquid type heat exchanger having means for controlling the flow of the feed or heat exchange liquid over the surfaces of the tubes as 311 til.

SUMMARY OF THE INVENTION A falling film heat exchanger according to the invention comprises a plurality of spaced apart vertical tubes secured to upper and lower tube sheets and having tube ends passing through the tube sheets; a shell around the tubesheet connected to; a member communicating with the upper end of the tube and forming a feed box for containing a reservoir on the upper tubesheet; means for directing the feed stream to the feed box; upper and lower tubesheets; Around the tube inside the torso between
means for conveying and removing heat exchange liquid therefrom; means for preventing liquid from flowing down the tube top end other than in the internal circular area adjacent the inner surface of the tube; and means for directing the feed liquid in a thin stream. for distribution along the inner surface of each tube as a membrane,
means spanning an internal circular area;

The circular region can be in the form of a continuous ring or a discontinuous ring.

The means spanning the inner circular region may be a porous liquid permeable rigid or elastic material. Porous materials that can be used include carbon, ceramic materials, metallic materials, and organic polymeric materials. The means spanning the inner circular region may also be a non-porous material with vertical grooves near the inner surface of the tube.

Non-porous materials can be rigid or elastic.

The falling film evaporator described herein also has a shell section that is located below the upper tube sheet, is closely connected to the inner surface of the shell to prevent water leakage, and extends between the upper tube sheet and the shell section. a horizontal separator plate or separator plate which together with the upper tube plate forms a heat exchange liquid box; means for directing the heat exchange liquid around the tubes inside the shell and capable of directing the liquid in the direction of said heat exchange reservoir; The separator plate is configured to have means for distributing the heat exchange liquid as a downwardly flowing liquid film along the external surface of the membrane.

In order to evenly distribute the liquid on the external surface of the tube, the separator or distribution plate is provided with larger holes through which the tube passes, thereby forming an external circular area between the hole wall surface and the external surface of the tube, which allows the heat exchange liquid to Means may be formed over the external circular area for distributing the liquid as a downwardly flowing liquid film along the external surface of the sample.

The means spanning the outer circular area may be the porous liquid permeable material described above. The means spanning the external circular region may also be a non-porous material with vertical grooves near the external surface of the tube. For this purpose, the non-porous materials mentioned above can be used.

As an alternative method for evenly distributing liquid on the external tube surface, the tube receivers of the distribution plate may be provided with vertical slots spaced apart in the holes prior to tube contact placement on the large surface. At this time,
Slot size, quantity, and liquid type and liquid head determine flow rate and liquid film thickness.

In some cases, ensuring that the heat exchange liquid flows outside the tube is important independently of ensuring that the feed liquid flows down inside the tube as a thin liquid film as well. The invention therefore provides a plurality of spaced apart vertical tubes fixed to upper and lower tubesheets and having tube ends passing through the tubesheets; means communicating with the upper end to form a feed box for containing a liquid reservoir on the upper tubesheet; means for directing the feed stream to the feed box, horizontally connected below the upper tubesheet in a waterproof manner to the interior surface of the shell; Separator plate in which the separator plate, the upper tube plate, and the body portion extending therebetween form a heat exchange liquid box: a means for delivering heat exchange liquid around the tubes inside the body to heat the liquid. oriented in the direction of the exchange box, said separator plate having said means for distributing the heat exchange liquid as a falling liquid film along the external surface of the sample. We also provide heat exchangers.

DETAILED DESCRIPTION OF THE EMBODIMENTS Identical or similar elements or parts that are illustrated in the various drawings are designated by like numerals to the extent reasonable and practical.

The heat exchanger 10 includes an upper horizontal tube sheet 12 and a lower horizontal tube sheet 14.
, and a cylindrical copper 16 connected to its tubesheet.

A plurality of spaced vertical tubes 17 are connected to the tube plate 12.
and 14 and extending through it. ! 116 has a portion 18 extending above the upper tubesheet 12, thereby forming a supply box 20 on the tubesheet 12 for containing liquid. Conduit 22 communicates with supply box 20 and delivers feed liquid thereto.

The porous plate 24 is preferably made of a ceramic material.
It is supported on the top of the tubesheet 12. The lower surface of the porous plate 24 is coated or painted with a circular layer 26 of a liquid impermeable material such as metal, ceramic, or polymeric material such as epoxy. The circular layer 26 has a slightly smaller diameter than the interior of the tube 17, thereby creating a small annular area that allows the feed liquid to contact the interior surface of the tube and flow down as a thin film.

A separator plate or distribution plate 26 is provided inside the shell 16 to accommodate the upper tube plate 12.
are spaced below and thereby form a heat exchange liquid box 28. Separator plate 26 has a larger hole 30 through which tube 17 passes. At the top of the separation plate 26,
A porous plate 32 of ceramic or polymeric material is attached. The tubes 17 extend through holes in the porous plate 32 that match the tube dimensions.

Conduit 34 communicates with heat exchange liquid box 28 and is used to supply heat exchange liquid thereto. If the refrigerant is used as a heat exchange liquid, a conduit 36 is provided for removing excess refrigerant and refrigerant vapor.

The heat exchange fluid flows through the porous plate 32 and through the larger holes 3
0 and the outside of the tube 17, from which it flows downward, adhering to the surface of the tube 17 as a thin film. Excess heat exchange liquid is removed from the shell side of the heat exchanger by conduit 38, while heat exchange liquid vapor is removed by conduit 40.

Overflow pipe 42 is located in communication with the upper end of inlet or pipe 17 . The opening or upper end 44 of the overflow tube 42 is located sufficiently high above the plate 24 to allow the feed liquid to accumulate in the root soil before excess liquid is drained through the opening 44.

The heat exchanger described in connection with FIGS. 1 and 2 is particularly useful as a freezing exchanger for producing potable water from seawater by cooling the seawater until a portion of it freezes into ice. The ice crystals are separated and melted into drinking water. Ammonia or Freon branded refrigerants can be used as heat exchange fluids. When used as a freeze exchanger, it can also be used to concentrate fruit juices and beverages.

Regardless of whether the heat exchanger is used for operations performed above or below room temperature, heat exchange efficiency is improved when the feed liquid travels down the tube as a thin film and at a controlled thickness and flow rate. . Increased heat exchange efficiency can also be obtained by moving the heat exchange liquid down the tube □ with a similarly controlled thickness and flow rate. It is not essential to control both the feed liquid membrane and the heat exchange liquid membrane at the same time, as the effect can be obtained by controlling only one membrane by means of the above device, but in order to obtain the best effect, the conditions should be met. If possible, it is generally desirable to control both membranes simultaneously.

When used as a freeze exchanger, the top of the liquid supply box 20 can be left open as shown or optionally covered if desired. Similarly, the lower end of tube 17 need not be enclosed; the feed liquid flows into tank 50 (FIG. 1), from where it is removed by conduit 52, and all or part of it is recycled.

FIG. 3 shows an alternative device that can be used to form a feed liquid film descending inside tube 17. Instead of placing a porous plate on top of the tubesheet 12, a porous stopper or plug 60 is placed partially on top of the 8 tubes.

The stopper 60 can be frustoconical in shape as shown in the figures to provide natural centering at the tube end.

The bottom of each porous stopper is covered with a liquid-impermeable circular material in the form of a metallic, ceramic, or polymeric disk 62. As can be seen, the slope of the stopper determines the width of the annular region between the disc 62 and the inner surface of the tube 17 through which the feed liquid flows and forms a film on the tube surface.

4-6 illustrate alternative embodiments of the present invention.

Separator or distribution plate 26 is provided with a larger hole 70 through which tube 17 extends. A circular relief 72 with a vertical outer wall and a flat bottom is provided on top of the plate 26 and a tube receiver is provided in the axial direction of the hole 70. Distribution O-ring 74
The relief 7 is provided by a slip fit to prevent it from moving easily.
It is located at 2.

The vertically spaced radial grooves 76 are
- Cut or molded onto the inner periphery of the ring 74; The size and quantity of the grooves greatly influences the amount of heat exchange liquid that flows from the distribution box 28 into the holes 70 and down the exterior surface of the tube 17 as a thin film.

7 and 8 show other embodiments of the invention.

In this embodiment, the tube holder of the separation plate or distribution plate 26 is provided in the hole.
A plurality of slots 80 are spaced apart and cut in each hole wall. The tube attached to the hole is then rotated and extended to join the plate. The bonding is done without compromising the dimensions of the slot so that liquid flowing through the slot forms a uniform falling liquid film on the external surface of the tube.

Although the present invention has been described with a falling film of feed liquid flowing on the inside surface of the tube and a heat exchange liquid flowing on the outside surface of the tube, the liquids are reversed, the feed liquid is on the outside of the tube, and the heat exchange liquid is placed on the outside of the tube. It should be understood that it can also be internal.

The above detailed description is provided only for clarity of understanding, and it will be obvious to those skilled in the art that various modifications other than the above embodiments are possible.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram of an embodiment of a falling film exchanger with spaced vertical tubes according to the invention; FIG. FIG. 3 is a partial vertical sectional view of a heat exchanger with a porous plug or stopper provided at the top of the tube inside the heat exchanger, and FIG. FIG. 5 is a partial vertical cross-sectional view of the top of the heat exchanger of a further embodiment of the present invention, showing the refrigerant separator or distribution plate along with the distribution ring around the tubes, taken along line 5--5 in FIG. FIG. 6 is a partial cross-sectional view of the distribution pipe shown in the apparatus of FIGS. 4 and 5, and FIG. 7 is a partial vertical cross-section of the upper part of a heat exchanger according to the present invention. is a diagram,
FIG. 8, a partial view of a refrigerant distribution plate with vertical slots in the tubesheet holes, is a cross-sectional view taken along line 8--8 of FIG. 7. Figure 3 Figure I5

Claims (5)

[Claims] (1) A plurality of vertical tubes arranged at intervals from each other and fixed to the upper and lower tube sheets and having tube ends passing through them; and a shell located around and connected to the tube sheets; , means communicating with the upper end of the tube and forming a feed box for containing liquid above the upper tube sheet, and means for directing feed liquid flow to the feed box; and tubes within the waste between the upper and lower tube sheets. means for conveying and removing heat exchange liquid therefrom; means for preventing liquid from descending from the upper end of the tube other than in the internal circular region near the inner surface of the tube; and a supply liquid. means for distributing the liquid as a thin falling film along the interior surface of each tube over said internal circular area; (2) A falling liquid model evaporator according to claim 1, wherein the means spanning said internal circular region is a porous liquid permeable material. (3) The falling film evaporator according to claim 2, wherein the porous material is an elastic body. (4) The means spanning the inner circular region is a non-porous material having vertical grooves near the inner surface of the tube.
The falling liquid model evaporator described in Section 1. (5) The falling film evaporator according to claim 2, wherein the porous material is a ceramic material, a metal material, or an organic polymer material.