US 3170512 A
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Description (OCR text may contain errors)
Feb. 23, 1965 J. F. D. SMITH HEAT EXCHANGER Filed March 29, 1963 FIG. 4
INVENTOR. JOHN F. D. SMITH.
United States Patent 3,170,512 HEAT EXCHANGER John F. D. Smith, Fayetteville, N.Y., assignor to Carrier Corporation, Syracuse, N.Y., a corporation of Delaware Filed Mar. 29, 1963, Ser. No. 268,945 3 Claims. (Cl. 165110) This invention relates generally to heat exchange apparatus. More particularly, this invention pertains to improved heat exchange tubes for use in condensers.
Typical construction of condensers herein under consideration, comprises an enclosed shell having a plurality of heat exchange tubes disposed therein forming interior passageways. The shell is provided with suitable connections for passing two fluid mediums in heat exchange relationship with each other such that heat is transferred from one of the mediums to the other. The heat exchange tubes conduct a first fluid medium through their interior and provide a surface over which a second fluid medium in the gaseous state may flow. The temperature difference between these two fluid mediums is such that the second fluid medium will condense by dissipating its heat of condensation to the first fluid medium.
A substantial quantity of heat may be rejected in this manner; however, the heat transfer capacity of a given size condenser is limited to a great extent by the temperature difference between the two fluid mediums and is also highly dependent upon the contact surface available for heat transfer.
It is an object of this invention to improve the heat transfer performance of condensers for use in refrigeration systems and the like.
Another object of this invention is to provide a heat exchange tube having a porous heat transfer surface and an arrangement for drainage of condensate.
These and other objects of this invention are achieved in the illustrated embodiments by providing a condenser having a plurality of horizontal heat exchange tubes disposed Within its outer shell. These tubes are each comprised of an impervious metal pipe substantially covered by a porous metal jacket to define an elongated opening along the bottom of the jacket. Portions of the pipe and jacket are in spaced relation forming a plurality of annular passageways in communication with the opening in the bottom so that condensate formed in the porous jacket may flow into the passageways and drain out the opening into a drain trough.
The porous jacket is formed of a compacted metal powder that provides a very large surface area in relation to its volume available for heat transfer and may be any metal possessing good thermal conducting characteristics, for example, electrolytically produced dendritic copper powder. The term porous as used herein is defined as the characteristic of a body having a large number of minute internal cavities of capillary size which form surface interstices in communication with a number of the internal cavities to provide minute passageways whereby a fluid medium may pass through the body.
The various features and advantages of this invention will become apparent from the following description when considered in connection with the drawings wherein:
FIGURE 1 is a diagrammatic sectional view of a condenser having heat exchange tubes in accordance with this invention;
FIGURE 2 is an end view of a heat exchange tube as contemplated by this invention;
FIGURE 3 is a sectional view of the heat exchange tube shown in FIGURE 2;
FIGURE 4 is a sectional view of the heat exchange tube in a modified form as contemplated by this invention.
3,170,512 Patented Feb. 23, 1965 Referring more particularly to the drawings, FIG- URE 1 shows a condenser 11 having an outer shell 13 with a plurality of heat exchange tubes 15 horizontally disposed therein and supported by the tube sheets 16. Condenser 11 is provided with connections 17 and 19 for conduction of a first fluid medium which passes through the interior of the heat exchange tubes 15. A second condensable medium enters the condenser 11 at connection 21 located in the upper portion of the shell 13 and the formed condensate leaves the bottom of the shell 13 from a drain connection 23.
The construction of heat exchange tubes 15 in accordance with this invention is shown by FIGURES 1 and 2. An impervious metal pipe 25 has formed therein a plurality of annular indentations 27 spaced along the longitudinal axis of pipe 25. A porous metal jacket 29 substantially covers the impervious metal pipe 25 and defines an elongated opening 31 (FIGURE 2) extending along the bottom of the jacket 29. Fixed within the opening is a trough 32 as disclosed in US. Patent No. 2,983,115 and is incorporated herein by reference. The porous metal jacket 29 and annular indentations 27 combine to form therebetween the walls of internal annular passageways 33 which communicates with the opening 31 at the bottom of jacket 29. The impervious pipe 25 and porous jacket 29 may be mechanically bonded totogether by any suitable method such as brazing to form a good thermal bond therebetween.
The porous metal jacket 29 employed by this invention is generally a preformed body formed of a compacted metal powder, for example, electrolytically produced dendritic copper powder. The process used to compact the metal powder may be any number of techniques in the powder metallurgical art providing the resulting compact remains porous as heretofore defined. It is desirable that the compact be sintered to provide rigidity, however, the operation must be such that the internal cavities are not sealed off from communication with each other.
In FIGURE 4, there is shown a modification of the heat exchange tube 15 as contemplated by this invention. In this construction the impervious metal pipe 25 is provided with a plurality of extended fins 35 thereon and is the type frequently employed in heat exchangers. The same porous metal jacket 29, heretofore described, substantially covers the extended fins 35 and may also be mechanically bonded thereto. A plurality of internal annular passageways 33 which communicate with the opening 31 (FIGURE 2) are again formed between the impervious pipe 25 and porous jacket 29 defined by the extended fins 35. The trough 32 is included in this construction.
The operation is such that the first fluid medium passing through the interior of the heat exchange tubes 15 removes heat from a condensable medium delivered into the condenser shell 13 through connection 21. The condensable medium enters the many internal cavities of the porous jacket 29 wherein it gives up its heat of condensation and condenses. The condensate continues on through the porous jacket 29 into the internal passageways 33 wherein it is conducted to the elongated opening 31 for drainage into the trough 32. A secondary tube sheet 34 is provided at one end adjacent one of the tube sheets 16 and interconnects the trough 32 of each tube to the connection 23 for drainage from condenser 11.
In addition to the high heat transfer performance obtained by this invention, other advantages are provided over prior art condensers. For example, it is possible to reduce the size and obtain the same capacity due to the large heat transfer area provided by the porous metal jacket without a proportional increase in volume.
Various other advantages and applications will occur 3 to those skilled in the art and it is understood that this invention is not limited to the described embodiments but may be otherwise practiced within the scope of the following appended claims:
1. A condenser comprising an elongated, heat conducting, impervious, metal, heat exchange tube, the enterior surface of said heat exchange tube having a shape defining a plurality of substantially circumferentially extending, substantially annular, grooves; a porous heat conducting, metal jacket being secured in heat exchange relation with substantially the entire exterior surface of said heat exchange tube and defining with said annular grooves a plurality of condensate passages; said porous metal jacket having formed therein an opening extending below and in communication with each said annular passage of said heat exchange tube, said opening defining a passage for the removal of condensate from said plurality of condensate passages.
2. A condenser as defined in claim 1 further including a relatively impervious, channel shaped, trough member, secured to said porous jacket and extending below said opening formed in said porous metal jacket, said trough being adapted to pass condensate from said plurality of condensate passages to a desired location.
3. A condenser of a type adapted to condense re-,
frigerant vapor for use in a refrigeration system comprising a condenser shell having a passage for admitting refrigerant vapor into said shell and a passage for withdrawing refrigerant condensate therefrom; a plurality of hollow impervious, metal heat exchange tubes disposed substantially horizontally within said shell, each said heat exchange tubes having an exterior surface having a shape defining a plurality of substantially circumferentially extending, substantially annular, grooves; a porous heat conducting metal jacket being secured in heat ex 1 impervious channel shaped trough member secured to said porous jacket and extending below said opening formed in said porous metal jacket, said trough being adapted to pass condensate from said plurality of condensate passages; a pair of tube sheets supporting said heat exchange tubes within said shell and defining with said shell a passage for the admission and withdrawal of a cooling heat exchange fluid for passage through the interior of said heat exchange tubes; a third tube sheet disposed adjacent and in spaced relation with one of said 1 pair of tube sheets, said third tube sheet defining with said one tube sheet a chamber for the collection and withdrawal of condensate, said channel shaped trough member extending through said third tube sheet and being open to said chamber formed between said third tube sheet and said one tube sheet so as to discharge condensatedrained from said condensate passages, along said trough, into said chamber.
References Cited by the Examiner UNITED STATES PATENTS 2,361,854 10/44 McCormack 62505 2,941,759 6/60 Rice et al 133 2,983,115 5/61 Caswell 165110 X CHARLES SUKALO, Primary Examiner.
KENNETH W. SPRAGUE, Examiner.