US2059725A

US2059725A - Shell and tube evaporator

Info

Publication number: US2059725A
Application number: US714768A
Authority: US
Inventors: Willis H Carrier
Original assignee: Carrier Engineering Corp
Current assignee: Carrier Engineering Corp
Priority date: 1934-03-09
Filing date: 1934-03-09
Publication date: 1936-11-03
Anticipated expiration: 1953-11-03

Description

Nov. 3, 1936. w. H. CARRIER SHELL AND TUBE EVAPORATOR Filed March 9, 1934 2 Sheets-Sheet 1 I IN VEN TOR. wzllzs H- Carrl er ATTORNEY Nov. 3, 1936. w. H. CARRIER SHELL AND TUBE EVAPORATOR.

2 Sheets-Sheet 2 Filed March 9, 1934 R N E m 3 3 & J MN A A 0w M N N Q QR .E\ S MN mv\ll P \& mm m Q E 3 3 TI Fllllll'l- A T TORNEY Patented Nov. 3, 1936 V UNITED STATES PATENT OFFICE SHELL AND TUBE EVAPORATOR Willis H. Carrier, Elizabeth, N. J., assignor to Carrier Engineering Corporation, N. J., a corporation of New York Newark,

Application March 9, 1934, Serial No. 714,768

11 Claims.

,co-pending application Serial 110,714,767 filed March 9, 1934.

Another object of the invention is to provide a shell and tube evaporator in which the coemcient of heat transfer for each tube will be substantially constant throughout .the length of that tube, and hence, each tube in theevaporator will do a maximum amount of work.

A further object of the invention is to so design the evaporator that the rate of vapor flow over any given tube is substantially constant throughout the length of that tube.

Still another object of the invention is to confine the refrigerant liquid to the tube surfaces and to prevent the entrainment of liquor particles in the vapor leaving the evaporator.

A feature of the invention resides in the provision of an evaporator having vapor outlets at the top thereof, a tube nest passing through the evaporator, and a partial diaphragm interposed between the tubes and the vapor outlets.

Another feature of the invention resides in discharging the refrigerant over the tube nest and utilizing the diaphragm to confine the reirigerant to the tube surfaces.

In a preferred embodiment, a feature of the invention resides in utilizing a diaphragm between the outlets and the tube nest, which diaphragm has a, maximum width at a. point proximate to the vapor outlets and a minimum width at the point or points farthest from the vapor outlets.

The above objects and features, and various others making for emciency and economy, will be more apparent from the following description to be read in connection with the accompanying drawings in which: i

Fig. l is an elevation, partly in section, taken on the line a a of Fig. 2.

Fig. 2 is a plan view taken on the line 2-2 of Fig. l.

With reference to the drawings, similar designations referring to similar parts, numeral it designates a cylindrical shell having one or more vapor outlets i i proximate the top thereof. The outlets ii and the scroll I2 provide a passageway through which vapor may be removed from the shell to any desired point, for example, the inlet of a centrifugal compressor, not shown. A plurality of tubes i3, constituting a nest or bundle, pass through the evaporator and are held at the opposite ends thereof in suitable tube sheets Id. Water, or any other medium, to be cooled.

is admitted to inlet water box i5 through pipe it, passes through tubes i3 into outlet water box I], from which it may be withdrawn to any desired point of usage through pipe l8. Liquid refrigerant from a condenser, for example, is admitted to thebase of the shell through pipe i9.

Pump 20, illustrated diagrammatically, withdraws liquid from the base of he shell through stand pipe 2i and discharges t e liquid through arefrigerant distributing header 22, which header is positioned above the tubes i3.. The refrigerant is discharged from the header in a plurality of streams substantially as shown, and

upon striking the tubes, is subdivided by impact intovery fine particles. In this manner, a very complete distribution of the liquid over the entire tube nest is secured. The liquid flows by 20 gravity from the first 'row of tubes to the second, to the third, etc.,v thus providing each tube with a thin film of refrigerant. Any excess falls from the lower row of tubes and collects in the base of the shell. The refrigerating effect is, of course, secured by evaporation of a part of this film from each tube. In order to maintain correct pressure conditions within the evaporator, it then becomes necessary to remove this vapor through outlets ii and scroll i2. However, in the vapor removal process, unless the velocity of the vapor is kept relatively low, it will entrain with itself some of the liquid from the tube surfaces. Further, since the pressure reduction tends to be greatest at points closest to the vapor outlets, there is a very marked tendency to do almost the entire refrigerating work in a relatively small portion of the evaporator, that is, the vapor tends to blow-through the tube nest at one particular point, leaving these tubes dry at that point. Former practice in shell and tube evaporator construction provided a very large shell for the purpose of securing a more even vapor flow from all parts of thetube nest; and an impact, or other type, eliminator for removing entrained liquor particles. Applicant has found that by providing a diaphragm be tween the tube nest and the vapor outlets, he may utilize the small shell and at. the same time avoid the use of eliminators. Thus, in the drawings, a hood 23, constituting a partial diaphragm, covers the distributing header 22 and the tube nest, thereby dividing the'shell into a lower chamber 24 and an upper chamber 25. As can be seen, the hood is drawn down to cover a portion of the sides of the tube nest, and in a. pre.-

ferred embodiment, the edges of the hood are utilized to define the orifices 26. In the preferred embodiment, as can be seen from Fig. 2,

the hood is widest at the pointsadjacent the outlets H and narrowest at the point or points farthest therefrom; hence, the orifices 26 are narrowest at the points adjacent the vapor outlets and widest at the point or points farthest therefrom. In operation, these restricted orifices tend to equalize the pressure reduction throughout the length of the shell, thereby to equalize the rate of vapor flow fromthe tube nest. Thus, below the hood, or diaphragm, in the chamber 24, the movement of vapor is entirely upward, as indicated by the arrows 21, while, above the hood, in the upper chamber 25, the movement of vapor is longitudinal from both ends toward the outlets II, as indicated by arrows 28. By insuring equalized vapor flow from the tube nest, any tendency to blow-through is avoided. Hence, the velocity of the vapor below the hood may be kept to a value below the critical value at which vapor entrainment would take place. the upward movement of the vapor, any particles which are entrained therein will be separated out by the action of gravity. Again, as is readily apparent, the impact of the liquid from the header 22 against the tubes, results in a relatively large volume of mist being created and by the provision of the hood, this mist is prevented from being drawn ofi directly through the outlets I 1 before it can accomplish any refrigerating work. Still further, by providing equalized vapor iiow through the tube nest, it is evident that the coefficient of heat transfer for any tube in the nest will be constant throughout the length of that tube, and hence, each tube has'a maximum effectiveness in performing refrigerating work.

Since certain changes may be made in the within embodiment without in any way departing from its scope, it is intended that the matter described herein shall be construed in a descriptive and not a limiting sense.

I claim:

1. In an evaporator, a shell, a tube nest passing through said shell, a vapor outlet from the shell, means for discharging a refrigerant liquid over the tube nest, and a hood covering said tube nest, and means restricting communication between saidtube nest and said outlet to different degrees in different portions of the shell.

2. In an evaporator, a shell, 'a. vapor outlet from said shell, a tube nest passing through said shell, means for discharging liquid over said tube nest, and a hood'covering said means and said tube nest, the edges of said hood defining orifices between the tube nest and the vapor outlets, said orifices being of minimum width proximate said outlets, and of maximum width at the points most remote from the outlet.

3. In an evaporator, a shell, a vapor outlet from said shell, a tube nest passing through said shell, means for discharging liquid over said tube nest, and a hood separating said outlet and said tube nest for equalizing the pressure reduction throughout the length of said tube nest, said hood restricting communication between said outlet and said tube nest to different degrees in different portions of the shell.

4. In an evaporator,- a shell, a vapor outlet from said shell, a tube nest passing through said shell, means for discharging liquid over said tube nest, a hood covering said means and said tube Further, during nest, the edges of said hood defining orifices between the space occupied by the tube nest and said outlet, said orifices being of varying width to promote an equalized vapor fiow from the nest, throughout the length of said nest.

5. In an evaporator, a shell, a vapor outlet from the shell proximate the top thereof, a tube nest passing through said shell, means for discharging refrigerant liquid over said tube nest, and a hood completely covering said means and tube nest for confining the refrigerant liquid to said tube nest.

6- In an evaporator, a shell, a vapor outlet from the shell, a tube nest passing through said shell, a header for discharging refrigerant liquid over said tubes, and a hood separating said vapor outlet and said tube nest for preventing the re-' moval of the refrigerant from said shell before it has contacted said tube nest. 7. In an evaporator, a shell, a vapor outlet from said shell proximate the top thereof, a tube nest passing through said shell, means for discharging refrigerant liquid over said tube nest, a diaphragm separating. said vapor outlet and said tube nest for dividing said shell into an upper and a lower chamber, said diaphragm providing a plurality of orifices for promoting equalized vapor flow throughout the length of, said shellfr'om the lower chamber to the upper chamher.

8. In an evaporator, a shell, a vapor outlet from said shell in the top thereof, a tube nest passing through said shell, means for discharging refrigerant liquid oversaid tube nest, and a hood covering said means and the top of said tube nest, said hood separating said means from said outlet, said hood being drawn down partially to cover the sides of said tube nest for preventing a short circuitof refrigerant directly from said means to said outlet.

9. In an evaporator, a shell, a vapor outlet from said shell at the top thereof, a tube nest passing through said shell, means for discharging refrigerant liquid downwardly over said tube nest, and a hood interposed between said tube nest and said outlet for dividing said shell into an upper and 'a lower chamber, said hood completelyv covering said tube nest and being drawn down partially to cover the sides of said tube nest, the edges of said hood being utilized to define aplurality of orifices betweensaid upper and said lower chambers.

10. In an evaporator a hood forming an upper chamber and a lower chamber, an outlet from the upper chamber, a nest of tubes and means for discharging liquid thereover in the lower chamber, and means restricting ,communication between said tube nest and said outlet to different degrees in dlfierent portions of the shell.

11. In an evaporator, a shell, a vapor outlet, a tube nest, means for discharging refrigerant liquid over said tube nest, means for separating said vapor outlet and said tube nest and for dividing the shell into a first chamber and a second chamber, said separating means providing a plurality of orifices between said chambers for promoting equalized vapor fiow throughout the length of said shell from said first chamber to said second chamber. g WILLIS H. CARRIER.