US1895755A - Heat exchange apparatus - Google Patents

Description

Jan. 31, 1933. E, B, FREEMAN I H'EAT EXCHANGE APPARATUS Filed March 24, 1932 frwenior ll J|- Wiines; Chas. T. Olson pasta 1.... 31,

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The present invention relates ,to heat exchange apparatus. 7 I

In he ordinary heat exchange apparatus such as an economizer em- 'loying tubular water conduits, it is found that the gases do not contact with the entire surfaces of-the tubes, but permit the formation of dead spaces. These dead spaces occur in the rear of each tube (that is, on .the side opposite to the side at which the gases first contact with the tube) and not only represent a diminution' in the affective heating surface of the apparatus, but also form a region in which ed ying takes place, thereby causing in-' '"creased resistance to the passage of the through the 'pparatus. The region of ed y- .ing is a re on of nearl triangular crosssection int 6 rear of eac tube which is occupied with turbulent and slow' moving currents of gas. The breaking u of the gas stream by the tubes and the e dying in the rear thereof, particularly at high gas velocities, are conducive to a high draft loss and a consequent high expenditure for draft power.

The object of the present invention is to provide a heat exchange apparatus in which eddy re ions are eliminated and in which two flui s, such as water and air, may be 1ndependently heated with maximum economy and minimum expenditure for draft power.

With this object in view, the principal feature of the present invention comprises a heat exchange apparatus including a pluralit of double elements, the external contour 02 the elementsbeing streamlined to provide for minimum eddymg. In the preferred form of the invention, each streamlined element comprises a round tube which may carry water under high pressure,.provided with a streamline fairing in the rear thereof which may carry air to be preheated. Thus, the streamline fairing not only prevents theoccurrence of eddies, but also affords a conduit for heating of a fluid. When the apparatus is used as a combined economizerand airheater, the water is under the boiler pressure carried by the round portion of consid-. erable mechanical strength, and the air which is under relatively low pressure is safe.- 5 3 1y carried in the fairing. v .Other features of the invention comprise certain novel features of construction, comrbmatlons and arrangement of arts hereinafter described and particular y defined in the claims.

In the accompanyingdrawing, Fig. 1 is anelevation, partly in section, of the preferredform of the invention, and Fig. 2 is a section on line 22 of Fig. 1.= V

The illustrated embodiment of the invent1on comprises a-combinedeconomizer and air'preheater having a casing 4 enclosinga plurality of elements indicated generally 6. Each element 6 comprises a pair of square end flanges 8 through which extends a round water .tube 10. The water tube protrudes some distance throu h the flanges.

Attached to the tu 10 is a hollow streamline fairing member 12. The member 12 may be of a single piece of sheet metal secured to the tube 10 by welding. The member 12, together with aportion of the outer wall of the tube 10, forms an internal passage 14 of generally triangular cross-section. The shape of the fairing member is of a shape which is aero-dynamically' satisfactory for providing smooth streamline flow over the elements and preventing the occurrence of eddies. In practice, a fairing memberof the type shown, of generally triangular shape, with a slight- 1y rounded edge, is preferred because of economy of manufacture. Each end flange 8 is provided with an opening of the same shape as the external contour of the com-- pleted streamline 12. The fairing member of each element extends to a position flush with the outer surface ofthe flan e. Both the tube 10 and the streamline e ement 12 are 00 secured to the end flanges by welding, as indicated at 16.

The elements are superposed, as shown in Fig. 1, the adjacent faces of the flanges 8 abutting to form continuous walls constituting a gas flue 18. Preferably, the contacting faces or edges of the flanges are recessed or grooved to receive the packing 20. The tubes are preferably staggered, as shown in Fig. 2. In the construction shown in the drawing, the gas passes upwardly through the apparatus; therefore, the streamline fairing members 12- are attachedto the upper sides of their respective tubes. The invention may be embodied in a construction in which the gas flows in any desired direction, but in any case, the fairing is attached to the rear side of each tube, that is, to the side at which the gas last contacts with the tube.

The spaces 22 and 24 between the walls of the casing 4 and the flue 18 constitute inlet and outlet air chambers for conducting air to and from the air conduits'12. The air passes from the inlet chamber 22 through all of the air conduits 12 in parallel and thence to the outlet chamber 24.

The water tubes 10 may be connected in any desired manner, as by headers or return bends. In the form of the invention shown in the drawing, the water is conducted serially through the tubes and return bends 28, to be finally discharged at the outlet connection The present invention provides a compact, eflicient, and rugged structure. It accommodates in a given space as much heating surface forwater tubes as could be accommodated with the conventional round tubes, and in addition, without increasingthe same space occupied, affords considerable heating surface for the air by virtue of the use of the streamline fairing. The efliciency of the'apparatus is greatly improved because of the elimination of wasteful eddying which would oppose a high resistance to the passage of as through the apparatus. The water tu es being of standard tube construction with circular cross-section, offer a maximum strength against the water pressures. At the same time, the construction of the hollow fairing members provides ample strength for the relatively low pressure of air to be heated.

2, While I have shown the present invention as embodied in a particular construction, it isto be understood that it is not limited thereto but thespecific forms and arrangements of the several parts may be varied as desired andwithin the scope of the appended claims. Having thus described the invention, what is claimed is: I

1'. Heat exchange apparatus comprising water 'tubes, a hollow streamline fairing member attached to each tube, and means for passing air to be preheated through the fairingmembers. v

2. Heat exchange apparatus comprising a plurality of tubes, each of external streamline shape and including a round portion for carrying water under pressure, anda hollow fairing portion to carry air.

3. Heat exchange apparatus comprising a flue, air chambers at the sides of the flue, a plurality of water tubes extending through the flue and into the air chambers, hollow streamline fairing for the water tubes extending across the flue and terminating in the air chambers tocarry air to be heated.

4. Heat exchange'apparatus comprising a plurality of elements, each element compris ing end flanges, a water tube extending through the end flanges, hollow streamline fairing attached to the tube and the end flanges, the elements being superposed in a manner to cause the flanges to form a flue, air chambers external to the flue for passing air to the fairing members, and connections for the water tubes in the air chambers.

5. Heat exchange apparatus comprising water tubes, a hollow angular streamline fairing member welded to each tube, and means for passing air to be preheated through the fairing members.

6. Heat exchange apparatus comprising water tubes, a hollow angular streamlinefairing member welded to each tube, and means for passing air to be preheated through the fairing members, end flanges having openings to receive the tubes and fairing members, the tubes protruding beyond the flanges, the

tubes and fairing members being welded to the end flanges.

In testimony whereof I have signed my name to this specification.

ERNEST B. FREEMAN.

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