US2508247A - Heat interchanger - Google Patents

Description

W; F. GIAUQUE HEAT INTERCHANGER May 16, 1950 Filed Sept. 25, 1945 FIB-1 5 Sheets-Sheet 1 MAL/AM 4 6/44/ 114 Arram/Ev May 16, 1950 w. F. .GIAUQUE HEAT INTERCHANGER 5 Sheets-Sheet 2 Filed Sept. 25, 1945 m/zwroz M1 1 MM 56/4 4412 j W Arron 5y Q \E a May 16, 1950 w. F. GIAUQUE HEAT INTERCHANGER 5 Sheets-Sheet 3 Filed Sept. 25, 1945 A TTO/C/VE Y Patented May is, 1950" HEAT m'rsncmwcna William F. Giauque, Berkeley, Calif., assignor, by mesne assignments, to Research Corporation, New York, N. Y., a corporation of New York Application September 25, 1945, Serial No. 618,439

This invention relates to heat interchangers, and is concerned more particularly with'heat interchangers constructed to obtain efficient heat transfer without excessive pressure drop.

It is a general object of the invention to pro vide an improved heat interchanger adapted for use with fluids that will provide a high heat.

transfer by providing uniform flow conditions for both of the fluids passing through the heat interchanger.

Another object of the invention is to provide an improved heat interchanger in which a large area of heat interchange surface is provided within a relatively small total volume of the interchanger.

Another object of the invention is to provide a heat interchanger of high efficiency which is easy to manufacture by commercial manufacturing processes.

Other objects and advantages of the invention will be apparent from the following description of the preferred embodiment thereof as illustrated in the accompanying drawings, in which:

Figure 1 is an elevational view of a heat interchanger embodying the invention.

4 Claims. (Cl. 257-229) the length 'of paths provided in the various tubes be substantially equal in length. Correspondmgly, for the fluid contacting the outer surfaces of the tubes, it is important that flow of fluid through the spaces between the tubes be maintamed substantially uniform by providing a substantially uniform dimension between the tubing at all points throughout the interchanger with excellent opportunity for cross mixing of fluids between the inter-tubing spaces.

The above objects are attained in the instant invention by the use of conduits or tubes wound in helical layers, the interchanger unit being composed of several such helical layers having a tubing arrangement to provide a constant length of the several pieces of tubing used and to provide a desired predetermined spacing radially with respect to the layers of tubing and axially with Figure 2 is a horizontal sectional view of the a heat interchanger-immediately below the upper manifold thereof, and taken as indicated by the line 2-2 in Figure l.

Figure 3 is a horizontal sectional view of the mid portion of the heat interchanger showing the arrangement of the crossover of the tubes, the view being taken as indicated by the line 3-3 in Figure l.

Figure 4 is a detailed elevational view of the spacing strip of the coils of the heat interchanger.

Figure 5 is a sectional view of the spacer strip taken as indicated by the line 5-5 in Figure 4.

Figure 6 is an enlarged fragmentary view illustrating a crossover arrangement of the inner group of tubes.

Figure 7 is an enlarged fragmentary view illustrating a crossover arrangement of the outer group of tubes. I

Figure 8 is a fragmentary enlarged view, partly in section, of an end of a heat interchanger unit.

Figure 9 illustrates a typical heat interchange system employing heat interchangers of the character disclosed herein.

In the construction of heat interchangers one important factor is the arrangement and relative disposition of the heat exchange surfaces of maximum area to provide for a uniform flow of the fluids through the interchanger. Thus, it is important that the tubing employed to conduct the fluid in one direction be of uniform size and that respect to adjacent turns of a layer of tubing. In order to obtain the same lengths of tubing in the various layers, in certain larger sizes of interchanger units, the layers may be made of an increased number of tubes wound per layer from the inside layer outward. With smaller interchanger units, the tubing which forms one layer, for example the outer layer of a group of tubing, through one-half of the interchanger, is crossed over midway of the length of the interchanger to form another layer, for example an inner layer of tubing. As a specific example, an interchanger having a group of tubing wound in three layers of properly related average diameters will be providedwith the same length of path of fluid flow in all the passes of the group by effecting a crossover between the inner and outer layers at the mid point of the interchanger. The same results can be obtained with any desired number of layers of tubing in a group but it is preferred to retain the number of layers small to cause less unbalance in the flow outside the tubes.

In interchangers operating at sufliciently high pressures so that a small pressure drop is not serious, it is preferred to use a crossover arrangement of the passes to enable the use of a reduced number of tubes in parallel, and a consequent increase in heat transfer on the inside tube surface.

While in general and in the usual average or small size interchanger it is desirable to maintain a uniform spacing between the respective layers of tubing, with a large interchanger the greater curvature of the inner layers will somewhat affect the flow outside of the tubes so that the spacing can be altered if desired to compensate for this effect and to obtain a substantially uniform flow ofthe fluid outside the tubes.

The invention has been illustrated in connec- 2,aoa,247

ing and with alternate layers wound oppositely to facilitate uniformity of heat transfer and cross mixing and to provide greater strength and rigidity. This type of interchanger also provides for a minimum number of tubes in parallel within a la er.

iteferring to Figures' 1, 2, 3 and 8, the heat interchanger includes a central post or support in the form of a pipe I around which two groups of heat interchange tubes II and I2 are provided within a casing 9, each-group consisting of three layers of tubing. As the upper and lower halves of each group of tubing are similar, the detailed description of the construction of each group will be made with reference to the upper half thereof. As previously stated, each layer of tubing consists of a helical coil of tubing of uniform spacing. The inner group of tubing II includes an inner layer II a, an intermediate layer H11 and an outer layer Ilc, which are wound in the resent instance with two tubes in parallel. The inner layer Ila is disposed about the pipe I0 and is spaced therefrom by an appropriate number of circumferentially spaced longitudinal spacer strips l3 which may be secured to the pipe In by soldering so that the inner layer Ila of tubing is spaced from the pipe III by the thickness of the spacer strips I3. The inner tubing layer Ila is also engaged by a plurality of spacer strips I4 (Figures 1, 2, 4 and 5) which serves to space the inter mediate layer I lb from the inner layer I la by the same amount as its spacing from the pipe I0. Each spacer strip I4 has a series of struck-out ears I4a which are spaced apart a distance equal to the outer diameter of the tubing and project inwardly between the adjacent turns of the inner tubing layer I la. so that the turns are spaced apart an equal amount by the ears I4a of the spacer strips. The ends Nb of the strips I4 asshown in Figure 8 are bent over to engage the end turns of the coil and the pipe I0 and arev secured thereto by soldered joints. If desired, the strips l4 and the tubing Ila may be secured together in assembled relation by soldering at an appropriate number of points. The middle layer Ill) and the outer layer I lc are similarly mounted and secured by spacer strips I4 having the ears Ma interposed between the turns thereof.

As previously explained, the upper and lower halves of the interchanger are similar and at the midpoint of the interchanger a crossover is effected between the inner and outer layers of the group while the intermediate layer remains in the same relative position. Referring to Figures 1, 3 and 6, it is seen that at the mid point of the interchanger the inner layer I la of the upper half is connected by a soldered sleeve joint I5 tothe tubing of the outer layer lie of the lower half, while the tubing in the outer layer Ilc of the upper half is similarly connected by a sleeve It to the tubing of the inner layer Ila of the lower half. The middle layer Nb of both the upper and lower halves are of the same diameter. In this way each of thelayers Ila, IIb and Ho of the inner group are of the same length.

The outer group of layers I2 comprising an inner tubing layer I2a, a middle tubing layer I2b and an outer tubing layer I20 are similarly constructed and arranged as the tubing of the inner group, except that this group is wound with three tubes in a set to provide a greater helix pitch or lead. The other length of the tubing can be made equal to that of the inner group of tubes wound with two tubes at a time and a correspond- 4 ing lesser lead. The outer tube group I2 is similarly provided with spacers I4 having spacing ears I4a.

At the lower end oi the heat interchanger the six pieces of tubing of the inner group II and the nine pieces of tubing of the outer group I2 are connected to an annular manifold I1 which is The pipe may be closed by means of a plug 2|.

made of suitable heat insulating material.

Referring to Figure 9, a heat interchange system is shown employing a pair of heat interchanger units I0 and Illa connected in series and disposed within an insulating casing 22, this arrangement being of the type employed, for example, in the manufacture of liquid oxygen. Associated with the heat interchanger group comprising the heat-interchanger units I0 and Illa is a forecooling refrigerant unit 23 and a fractionating column 24 both of conventional construction and illustrated herewith to show a complete system. There is also provided a source 26 of high pressure air which is connected to the lower heat interchange unit I0 through a conduit 21 to deliver high pressure air to the lower end thereof. The air passes upwardly through the heat interchanger unit I0 and is withdrawn from the upper end of this heat interchanger unit through a conduit 28 connected to the refrigerating unit 23 where a further cooling of the air is effected. The cooled air is brought back to the lower end of the upper heat interchanger Illa through a conduit 29. The discharge from the upper end of the unit Illa is provided through a conduit 3| which leads to the upper end of the fractionating column 24, the eiiluent from the top of the fractionating column 24 being returned through the pipe 32 to pass downwardly through the heat interchanger units Illa and II) to cool the air within the tubes and to be discharged at the bottom through a discharge elbow 33.

L Operation The operation of the heat interchanger will be described in connection with the system shown in Figure 9. From the above description it will be seen that high pressure air supplied through the inlet pipe 21 will travel upwardly through the tubing of the lower heat interchanger unit Ill, being cooled by the downwardly traveling eiliuent from the fractionating column 24 which travels through the spaces between the layers of tubing. The partially cooled air is carried from the manifold I9 at the upper end of the lower heat interchanger unit I0 through the discharge pipe 28 to the forecooling unit 23 where it is subjected to refrigeration in the desired degree in accordance with the fiuidsbeing employed. The cooled air from the forecooling unit 23 is returned through the pipe 29 which conducts it to the manifold Ila at the lower end of the upper heat interchange unit Illa where, as it travels upwardly, it is further subjected to cooling by the eflluent passing downwardly through this heat interchanger. Preferably, the length of the heat interchanger is so selected with respect to the use for which it is intended so that the air will be cooled to the appropriate temperature for feed- -ing through the discharge pipe 3| to the fractionating column 24 from which liquid oxygen can be obtained in the usual manner.

atoms? While the description of the unit and its mode of operation have been made in connection with the production of liquid oxygen, it will be apparent that the heat interchangers, such as units It and ma, can be used singularly or in combination for any desired character ofheat transfer at high or low temperatures with the heat transfer taking place between, on the one hand, a fluid traveling through the helical coils of tubing and, on the other hand, a fluid traveling between the helical coils of tubing.

While I have shown and described a particular form of the invention, it will be apparent that the invention can be modified or employed in other forms without departing from the scope of the invention as defined in the claims appended thereto.

I claim:

1. In a, heat exchanger, inlet and outlet manifolds spaced along a longitudinal axis, and a plurality of heat exchange tubes of substantially equal lengthand diameter having their ends connected to the manifolds, one group of said tubes being wound to form at least two helixes disposed end to end and on different diameters and with a crossover connection between the helixes, the two sets of helixes thus formed by such tubes being nested and concentric with the helixes of adjacent tubes, another group of said tubes being each wound to form at least two helixes likewise disposed end to end and on difierent diameters and with a crossover connection with the helixes, said last-named helixes being likewise nested concentric to each other and with respect to the helixes of the first-named tubes, each of the helixes formed by the tubes of the second group being formed by a number of tubes greater than the number of tubes forming the helixes of the first group of tubes whereby the lead of helixes formed by the greater number of tubes is greater than that of the helixes formed by the lesser number of tubes to obtain tubes of the same length in both groups. p

2. In a heat exchanger, inlet and outlet manifolds spaced along a longitudinal axis, and a plurality of heat exchange tubes of substantially equal length and diameter having their ends connected to the manifolds, one group of said tubes being wound to form at least two helixes disposed end to end and on different diameters and with a crossover connection between the helixes, the two sets of helixes thus" formed by such tubes being nested and concentric with the helixes of adjacent tubes, another group of said tubes being each wound to form at least two helixes likewise disposed end to end and on different diameters and with a crossover connection with the helixes, said last-named helixes being likewise nested concentric to each other and with respect to the helixes of the first-named tubes, longitudinal spacer strips between and contacting the tubes of said nested helixes and having laterally projecting ears extending between and contacting adjacent turns of each helix, each of the helixes formed by the tubes of the second group being formed by a number of tubes greater than the number of tubes forming the helixes of the first group 01 tubes whereby the lead of helixes formed by the greater number of tubes is greater than that of the helixes formed by the lesser number of tubes to obtain tubes of the same length in both groups.

3. In a heat interchanger, a plurality of groups of conduits, each of said conduits having substantially the same length and diameter, each group comprising a plurality of sets of helically disposed similar conduits having a common helix axis and arranged in predetermined radially spaced relation, the conduits of each set forming a layer of the same helical radius and lead, at least two sets of conduits forming respective layers of a group at one end of the interchanger crossing over intermediate the ends of the interchanger to replace each other in the respective layers to provide conduits of substantially the same length in said sets, and the respective numbers of conduits in each group being related to each other and to the respective diameters of the groups of conduits to provide conduits of substantially the same length in said groups.

4. In a heat interchanger, a plurality of groups of conduits, each of said conduits having substantially the same length and diameter, each group comprising a plurality of sets of helically disposed similar conduits having a common helix axis and arranged in predetermined radially spaced relation, the conduits of each set forming a layer of the same helical radius and lead, the sets of conduits forming the extreme inner and outer layers of a group at one end of the interchanger crossing over intermediate the ends of the interchanger to form the opposite extreme layers of the group at the other end of the interchanger to provide conduits of substantially the same length in said sets, and the respective numbers of conduits in each group being related to each other and to the respective diameters of the groups of conduits to provide conduits of substantially the same length in said groups.

WILLIAM F. GIAUQUE.

REFERENCES CITED The following references are of record in the iile of this patent:

UNITED STATES PATmTS Number Name Date 104,326 Long June 14, 1870 429,421 Colt June 3, 1890 1,029,981 Fahrman et al. June 18, 1912 1,464,705 Goosmann Aug. 14, 1923 1,526,320 Cook Feb. 17, 1925 1,961,202 De Bauire June 5, 1934 2,081,043 Kuhni May 18, 1937 2,141,899 Bennett Dec. 27, 1938 2,160,898 Pefl' June 6, 1939 2,241,186 Coons May 8, 1941 FOREIGN PATENTS Number Country Date 912,423 France Fab. 1, 193'!

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