US2181704A - Heat transfer apparatus - Google Patents

Description

Nov. 28, 1939. D. R. M NEAL HEAT TRANSFER APPARATUS 3 Sheets-Sheet 1 Filed Nov. 26, 1935 VENTOR fx/h/ TT RNEYS A z IMO -j 4 v up 4 5 W J W 7 a z W a a n a a a z n a z z n n z z z z a z s a n a n a m a s ,n A s n u 0 4 w a 5 4/ 2 m 5 a/aw I J W Z 3 Z Z .5 1 m fi Nov. 2& 1939.

D. R. M N EAL HEAT TRANSFER APPARATUS Filed Nov. 26, 1935 3 Sheets-Sheet 2 VENTOR Nov. 28, 1939. D. R. M NEAL HEAT TRANSFER APPARATUS Filed Nov. 26, 1935 3 Sheets-Sheet 5 5; INVENTOR f ATTORNEY Patented Nov. 28, 1939 UNITED STATES HEAT TRANSFER APPARATUS Daniel Raymond McNeal, Abington, Pa., assignor to Andale Company, Philadelphia, Pa., a corporation of Pennsylvania Application November 26, 1935, Serial No. 51,581

3 Claims.

This invention relates to heat transfer apparatus, particularly to a heater or c'ooler of the tube and shell type.

The invention, moreover, contemplates a tube and shell heat exchange unit particularly adapted to the cooling or condensation of gases or vapors, the gases or vapors being passed through the tubes within the shell.

Generally considered, the objects of the-invention are improvement in efliciency of heat transfer; improvement in the structure; and an increase in the ease with which repairs and maintenance may be effected, these general objects all being served by the more or less specific objects and advantages set forth below.

Another major object of the invention is to increase the uniformity of the product, such as condensate, delivered from the heat exchanger considered as a whole, and from the tubes thereof considered individually.

The foregoing objects and advantages are secured by means of the construction illustrated in the accompanying drawings and described more fully hereinafter. In the following description, moreover, numerous additional objects and advantages are brought out. In the drawings Figure 1 is a longitudinal sectional view of a heat transfer unit constructed in accordance with the present invention, this view being taken substantially as indicated by the section line l-l on Figure 2;

Figure 2 is an enlarged cross-sectional view taken as indicated by the section line 2-2 on Figure Figure 3 is an enlarged view taken on the line 3-3 of Figure 1;

Figure 4 is an enlarged elevational view of the tube bundle or nest with the baiiles associated therewith, certain parts being broken away and shown in section so as to illustrate features of construction;

Figure 5 is a fragmentary view of certain details of the baflle construction;

Figure 6 is a fragmentary view similar to the showing of Figure 1 but illustrating a receiver type separator associated with the tube sheet at the outlet end of the tube bundle;

Figure 7 is a somewhat diagrammatic view of the connections which I prefer to employ for the vent and'the outlet for the cooling medium; and

Figure 8 is an enlarged fragmentary view of a joint between a header a tube sheet and the header shell at one end thereof.

In considering the drawings and the important In addition, in accordance with my preferred 1 practice, the unit is mounted in a substantially upright position, this being of advantage and of importance in connection; with other features, as will appear in the following description.

The apparatus of this invention (see particularly Figures 1, 2 and 3) includes a shell I, having suporting brackets la, which shell is cylindrical or tubular, and having an accurately machined inside bore or surface so that, in conjunction with the use of an accurately built-up tube and baffle unit, ready removability of this unit is assured. As a result of this, the tube and baiile unit may readily be removed, replaced or substituted. The shell is provided with an inlet 8 for the cooling medium and an outlet 9 therefor, these two connections being disposed closely adjacent to the extreme ends of the shell with a view to obtaining maximum utilization of the available length within which to secure circulation of the cooling medium.

The tubes I0 may, of course, beof any desired number and, in addition, the tubes and shell may obviously be of different lengthsto meet different conditions. All of the tubes, however, are preferably combined into a single pass, this being of importance in eliminating irregularities in expansion and contraction, with consequent irregular strains and buckling tendencies on the tubes themselves and the tube sheets.

At one end of the tubes, the upper end in Figure 1, a tube sheet H is provided, this sheet being of greater diameter than the diameter of the bore in the shell. A packing i2 is interposed between the sheet II and the end of the shell which may desirably be enlarged as at l3 to provide an increase in the packing area and further to provide ample room for the ring of securing bolts it which is positioned around the outside of the packing ring I2.

The inlet header l5 for the gas or vapor is seated in a groove formed in the outer face of the tube sheet H, a packing It being interposed to provide a tight joint (see Figures 8). The header is secured to the tube sheet by means of another ring of fastening bolts ll, this ring beis completed by means of a split or multi-part ring I 8 which engages an out-turned flange l8 around the lower edge of the header l5, this flange being the part which seats against the packing l6.

With regard to the header itself, it should be noted that the body thereof is preferably of regular cylindrical shape, the same being closed at the top by a plate 20 positioned in a plane at right angles to the axis of the header. The header is further at least as great in axial dimension as the diameter thereof. This header construction is in contrast with prior types of construction, especially when considering the position of the inlet connection 2| intermediate the ends of the header, the inlet further having its axis at right angles to the axis of the header. I have found that this arrangement is of quite unexpected advantage and importance for the reason that, in spite of the angularity of the inlet connection and the axis of the header and of the space in the top of the header which is under the closure plate 20, a greatly improved distribution of gas or vapor to the tubes is provided. In a heat exchange unit of this type, in order to produce an end product of uniform characteristics, each tube of the bundle must function in essentially the same manner and effect an equal amount of heat transfer. My experiments have shown that curved inlets or inlets which are aligned with respect to the tubes have a tendency to deliver a greater volumeof gas to some tubes than to others. This tendency seems at least in large part to be overcome by the construction described above, a possible reason for this being that the angle of the inlet and the angular spaces in the top of the header may tend to smooth out swirls and eddy currents and thus establish more uniform pressure in the entrance ends of the several tubes. In any event, I have found that the condition of the gas or condensate discharged from the individual tubes at the bottom thereof when employing an inlet arrangement as already.

described is substantially uniform.

that the tubes are here expanded into another tube sheet 22, this sheet being of substantially the same diameter as the bore in the shell so that it fits therein and may float or move with the tubes as they expand and contract. The lower end of the shell is recessed at 23 to receive packing which may be advanced by means of the ring 24 secured by bolts 25 and thus maintain a tight joint. With respect to this floating tube sheet and the packing therefor, it should be noted that the packing gland (by virtue of the passage of the gas through the tubes and of the cooling medium around the tubes) is located on the liquid side of the unit. My improved device, therefore, does not require any floating connection or packing on the gas or vapor side, this being of sub stantial practical advantage in use.

The outlet header 26, similarly to the inlet header, is secured to the tube sheet 22, bolts 21 being provided for this purpose. An annular recess is provided in the outer face of the tube sheet to receive a complementarily shaped flange formed on the header, packing 28 being interposed between the two parts. The discharge connection for the outlet header is shown at 29.

A drainage port 3| for the shell space is provided adjacent the lower end thereof. In addition to this port, I prefer also to provide an additional threaded to receive the pipe 33 which extends downwardly through an aperture provided for that purpose in the lower header 26.

With a viewto providing against the accumulation and trapping of any gases or vapors in the shell, the invention providesa vent passage 30 which is formed in the upper tube sheet I I with its inlet end opening through the bottom face of this sheet. By this arrangement, and with the unit in a substantially vertical or upright position, venting of all vapors and especially any occluded gases which may be released in the shell is provided for, and in consequence maximum utilization of the tubes for heat transfer is ensured. While this venting arrangement may fully answer some requirements of use, I prefer to further ensure complete discharge of all gases by employing connections (see Figure 7) which will produce a positive pressure in the region of the outlet 9 for the cooling medium. As seen in Figure 7, a pipe 55 coupled with the outlet connection 9 extends upwardly above the level of the upper tube sheet II and then is bent downwardly with an outlet 56 positioned at a level also above the tube sheet II. This outlet is positioned within an open funnel from which the cooling medium may be carried away as by pipe 58. The pipe 59 which is connected with the vent passage 30 also includes a portion extended above the tube sheet II and similarly has an outlet 50' positioned above that level within the funnel 51. This arrangement prevents any possible syphoning action on the cooling medium and the head of water above the tube sheet affords a positive pressure in the region of the outlet connection 9. In consequence, complete dscharge of gases through the vent is ensured.

The foregoing action may still further be augmented by employing a valve 6| in the pipe 55, which valve is preferably adjusted to increase the pressure within the shell. A further and important advantage of these'arrangements resides in the fact that deposits such as scale on the outside surfaces of the tubes are materially reduced. This reduction is most noticeable when the outlet valve is adjusted to ensure a pressure in the neighborhood of about five pounds or more above atmosphere, depending on the temperature of the incoming Vapors to be condensed. The reason for this may possibly be that the increased pressure serves to reduce the liberation of occluded gases in the cooling medium, but in any event I have found from actual experiment that the arrangement produces a substantial reduction in deposit on the tubes. With respect to the amount of pressure which is preferably maintained, it might be noted that the temperature of the gases beingpassed through the tubes is of importance since with a high temperature in these gases the cooling medium within the shell will of course, also have a relatively high temperature, at least toward the upper end thereof. With a higher temperature a greater pressure is apparently required in order to prevent release of occluded gases. As indicated, I have found that where the temperature of the gases being treated is relatively low and in consequence the temperature of the cooling medium is relatively low, the pressure may be dropped to in the neighborhood of five pounds.

In considering the above it might also be noted that the foregoing is in contrast with prior practice, since I contemplate throttling or restricting the outlet passage for the cooling medium to a greater extent than the inlet therefor.

With respect to the baille arrangement, attention is directed to Figures 3, 4 and 5 in which it will be seen that a plurality of baflies 34 are positioned within the shell transversely thereof, these baflies preferably being substantially circular except for a portion which is cut away at one side, as at 35 in Figure 3. Alternate bailies are cut away at opposite sides so as to provide a zigzag pathof fiow for the cooling medium from the inlet connection 3 to the outlet connection 9. The baiiling and, in fact, the entire tube nest or bundle, is arranged to accurately fit the inside bore of the shell, an accurate fit of the tubes in the baflies also being provided for so as to prevent shortcircuiting of the cooling medium as far as possible.

Instead of spacing these baflies by placing sleeves on certain of the tubes III, as has been common heretofore, -I provide separate means for this purpose. As clearly seen in Figures 3 and 4, a plurality of positioning rods 36 are employed around the nest of tubes, and on these rods spacer sleeves 31 are arranged so as to provide the desired spacing between the battles. The spacers and baflles are tightly secured in their proper positions by means of a threaded bolt 39 having a head 39 adapted to abut against the lower face of the upper tube sheet II. This bolt carries a pair of nuts 40 and 4|, one of which (40) abuts against the uppermost bailie 34 and the other of which (4|) abuts the short spacing sleeve 42, which, in turn, bears on the subjacent baffle 34 and thus tightens all of the remaining ones against the lower tube sheet 22. The baflles are thus firmly secured in position and are not subject to vibration and'the like, with the consequent wear of the tubes where they pass through the bafiles.

A further advantage of the positioning means for the baflles is that by the employment of positioning devicex which are separate from the tubes, the tubes are all left free so that they all effect uniform heat transfer and, in consequence, produce a uniform product.

Additional longitudinally extending baflie elements 43 are employed, these being offset circumferentially of the shell substantially from the points at which the bailles 34 are cut away. The baflies 43, therefore, (see particularly Figure 3) prevent flow of the cooling medium around the tube nest considered as a whole and thus ensure maximum contact of the cooling medium with the tubes.

As seen in Figure 5, the peripheral edges of the baffles 34 are recessed to a depth equal to half the width of baflles 43 and, in addition, the baflies 43 are recessed to a depth equal to half of their own width, and these recessed portions are interfitted as at 44 so as to still further increase the rigidity of the tube bundle in general and, in particular, to further reduce vibration of the bailles.

As best seen in Figure 1, the uppermost baiile 34 may be provided with one or more apertures 34a for the purpose of ensuring passage of accumulated gases or vapors to the vent 30. This uppermost baflle, and also the one at the bottom of the unit, is of substantially complete circular shape, i. e., is not cut away at a side as are the intermediate baifles and, as a result, the cooling medium is normally confined in its fiow to the passes which lie between the uppermost and the lowermost baflies.

The showing of Figure 6 illustrates the mannerin which a receiver type separator may be applied to the lower tube sheet 22 in place of the header 26 shown in Figure 1. This device is preferably formed as a cylinder 45, the upper end of which is fastened to the tube sheet 22 by means of a ringf46 adapted to seat in the groove provided in the lower face of this tube sheet. A ring of bolts 'f4| serves to attach the member 46. The lower end of the cylinder 45 is closed as at 48, and this closure is provided with a con nection 49.

A transverse partition 50 is also positioned within the cylinder 45, this partition being centrally apertured to cooperate with the conduit 5| which depends therefrom. An apertured ring 52 is positioned around the lower end of the conduit 5|, and a vapor discharge from the space between the partition 50 and the ring 52 appears at 53. In addition, a further connection 54 communicates with the chamber between the ring 52 and the lower closure 48. a

One point to be noted in connection with the structure of Figure 6 is that the straight cylindrical wall of the separator which defines the chamber into which the tubes discharge offers minimum resistance to the discharge, which is another factor ensuring uniformity of product through each tube.

In use, either one of the connections 49 or 54 may be used for reflux or for draw, and the connection 53 as a vent. The arrangement is highly effective in separation of condensed from uncondensed products because of the downward discharge through the central conduit 5|. It is further of considerable advantage to combine the receiver type separator with the condenser, making the two as a unit, since the functions of the separator need not be taken care of by additional equipment and piping. In a typical installation, the connection 53 might be used for vent of uncondenser vapors, the connection 49 for draw-ofi of a portion of the condensed product and connection 54 for reflux, in accordance with which a portion of the product may be recirculated, for example, through distilling equipment and from there to the upper end of the condenser.

In conclusion, the following advantages of various features are further emphasized:

By virtue of securing the upper tube sheet'directly to the shell and of securing the upper header to the tube sheet, the two securing means being independent of each other, it is possible to make the various joints more leak-proof than in constructions where the tube sheet is pinched between the header and the shell. In addition, this arrangement facilitates testing for leaks and correcting for them, if found. With regard to this, it should be borne in mind that the water pressure must be kept in the shell in order to test for leaks around the tubes in the tube sheets.

If the connections of the headers to the tubeits tightness until after the gasket has been buried again and the process has been re-started. The arrangement of headers and tube sheets, including the gaskets and securing means therefor, is also of advantage since it is not necessary to break the path of the cooling medium in order to inspect or clean the tubes or replace the vapor joints.

The passage of the gas or vapor to be cooled or condensed through the tubes is further of importance in connection with the mounting of the tube sheets and of the headers thereon. By virtue of these features maximum convenience is afforded in cleaning the vapor side of the tubes, i. e., the interior of the tubes, so that in cases where the unit is used in a process necessitating an unusual degree of purity in end product, it is readily possible to maintain the desired standard. Uniformity of the end product is also improved by virtue of passing the vapor through the tubes and, in addition, by means of the special form of inlet header which provides substantially equal distribution of vapor to the several tubes of the bundle.

Another important advantage of my improved construction is the arrangement of tubes and baflles to constitute a unit which may readily be inserted in and .withdrawn from the shell. Furthermore, the accurate machining of the shell to a predetermined size is of importance not only in permitting minimum clearances between the baflles and the wall of the shell and thus reducing shortcircuiting to a minimum,- but further since the tube and bafiie units may readily be replaced with positive assurance of duplication of performance. For example, if a plurality of condensers are employed in a plant and a single tube bundle or unit is kept on hand as a spare, this unit may be inserted in any one of the condensers and the performance of that condenser still retained at the desired value. This interchangeability is further facilitated by virtue of the accurate machining of the tube sheets from forgings, as-is contemplated in accordance with this invention.

It should further be observed that the tube and baflieunit incorporates tube sheets with the tubes extended therebetween and, in addition, separate means for positioning the baflles, the tube sheets alone serving as points of reaction for the devices by means of which the baflles and spacers are tightened in position.

The arrangement of the vent 30 in the upper tube sheet, the disposition of the shell in an upright position and the maintenance of a positive pressure within the shell all cooperate in ensuring complete discharge of accumulated vapors or occluded gases from the shell space and thus not only maximum utilization of the tubes for heat transfer but also a marked reduction in the formation of deposits on the tubes.

Various of the features already mentioned are important contributors to the object of increasing the uniformity of the product discharged from each of the individual tubes of my improved heat exchanger. Greater uniformity of the product is attained principally by three features, as follows: passage of the vapor or gas to be cooled through the tubes; substantially equal distribution of the gas or vapor to the tubes by the novel header construction herein disclosed; and provision for mounting the baiiies within the shell entirely independently of the tubes so that the tubes are entirely unobstructed on their outside surfaces and may, therefore, effect uniform heat transfer.

I claim:

1. Heat transfer apparatus including a generally upright tubular shell, a nest of tubes in the shell, a tube sheet at the upper end of the shell having a diameter larger than the inside diameter of the shell, means securing the tube sheet against the end of the shell, and a vent for the shell space including a passage formed in said sheet and having its inlet end opening through the side face of the sheet presented to the'interior of the shell, and'further having its outlet end opening through a surface of the sheet adjacent the periphery thereof.

2. Heat transfer apparatus including a generally upright tubular shell, a nest of tubes in the shell, a tube sheet at the upper end of the shell having a diameter larger than the inside diameter diameter of the shell, means securing the tube.

sheet against the end of, the shell, a header associated with said tube sheet, and a vent passage formed in said sheet and having its inlet end opening through the side face of the sheet presented to the interior of the shell and its outlet end opening through a surface of the tube sheet at a point peripherally beyond said header.

DANIEL RAYMOND MCNEAL.

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