US1767989A - Heat interchanger - Google Patents

Description

June 24, 1930. A. E. LEEK HEAT INTERCHANGER Filed April 22. 1927 5 Sheets-Sheet l KM, 1 15mm I ,Ws

June 24, 1930. A. E. LEEK HEAT INTERCHANGER' Filed April 22, 1927 5 Sheets-Sheet 2 June 24, 1930. A. E. LEEK HEAT INTERCHANGER Filed April 22, 1927 5 Sheets-Sheet 3 June 24, 1930. A. E. LEEK 1,767,989?

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June 24, 1930.

A. E. LEEK HEAT INTERCHANGER 5 Sheets-Sheet 5 Filed April 22. 1927 J 'GMuA- m (WA 1&1 QMMMYM Patented June 24, 193% i ALBERT EDWARD LEEK, F WIGAN, ENGLAND rice HEAT INTERCI-IAN GER Applicationfiled April 22, 1927, Serial No. 185,878, and in Great Britain: December 8, 1926.

The present invention relates to improvements in heat interchangers.

Heat interchangers are known in which pairs of tubes arranged one within the other are nested within a casing, hot flue gas being passed along the spaces between an inner pipe for conveying water .to be heated and an outer pipe, over the outer surface of which later, air to be heated is passed. In such arrangement the tubes have been arranged with their axes eccentric to one another to leave longitudinal spaces of crescent shape in cross section, and the whole of the tubes-have been arranged in parallel.

Experience has shown that such arrangements are particularly liable to become rapidly choked with deposit from the. flue gases, and only a low eflicieney is obtainable due to the restricted fluid flow possible.

secure the free and unrestircted flow of'the fluids, such as flue gas, air and water.

According to the present invention means, such as fans, pumps or the like, are provided to force the fluids through the heat interchanger at high velocity. I

Further the air, gas andwater passages are arranged to avoid any dead spaces or rapid alterations in cross sectional area with a view to preventing any drop in velocity of flow, or eddies, with consequent reduction in heat transfer efliciency, damage by corrosion or the like. 7 v The invention is more particularly de- 5 scribed with reference to the. accompanying drawings in which Fig. 1 is a diagrammatic side elevation of one form of the complete apparatus.

Fig. 2 is a sectional elevation through one form of heat exchanger unit.

F Fig. 3 is a sectional View on line 33 of i 2. .Fig. 4: is a sectional elevation through a modified form of construction.

An object of the present invention is to Fig. 5 is a diagram showing a further modified arrangement in sectional elevation on line 55 of Fig. 6.

Fig. 6 is a sectional view on line 66 of Fig.

Fig. 7 is a sectional elevation of a detail. A heat interchanger plant according to the present invention will comprise a chamber 1 which may be of cylindrical cross section (Figures 1 and 2) having groups of nested tubes therein, comprising water tubes 2 co-axial with flue gas tubes 3 carried between end plates, 5 ofthe casing. The end plates are spaced away from the ends of the casing which has at one end a header 6 which presents a concave deflecting surface to the flue gas, and may have additional deflecting plates 7 to be hereinafter described, whilst at the opposite end of the casing a gas inlet 8 and outlet 9, respectively are provided.

The casing 1 further has an air inlet 10 and outlet 11 either of which is connected to a fan to induce or force as the case may be, the air at high velocity through the casing. The fan 12 is provided to force air from the atmosphere through inlet 10 into the casing and over the outside of the flues 3, and out through the hot air main 14 connected to furnaces or other industrial plant requiring heated air. Similarly hotgas may be induced from a main flue through inlet 28 and gas tubes 3 in the casing by means of a fan 17 connected to the gas outlet 9 which fan delivers the gas after it has been robbed of its heat back tothe main flue through a discharge duct. A valve or damper can be provided in the main flue to short-circuit the passage of the gas through the heat interchanger.

In the arrangement of Figure 1 the heat interchanger unit 1 is arranged vertically, which has the advantage that the bottom of the casing can be closed by doors 41 to allow any, deposits of ash, soot and the like to fall vertically into the pit 42 for removal.

In the particular arrangement shownin Figures 2 and 3, the heated gas passes along the length of the heat interchanger casing, and then back along the same in two pass, the gas passages 3 being arranged in parallel to one another in each pass, while-the water tubes 2 which they enclose, are preferably wholly in series.

Further it will be desirable to arrange the flow of air as shown, so that this passes in counter-current to the gas, and by the provision of the baflie plate also passes in twopass through the heat interchanger.

Valve means controlled by handles 21 and 22 may operate the short-circuiting of the air direct from air inlet to air outlet, and

further valve means 23 may control the short-circuiting of the gas from inlet to outlet when it is desired to put the economizer or heat interchanger out of circuit.

It will be noticed that the casing 1 has an 7 increased cross sect-ion at its ends as at 2 1,

26, to allow of free flow of the gas and air as the direction of flowis changed. If desired,

the curved internal guide plates 27*, 27 can be removed by means of a handle 28 upon theopening of the casing by a door 29 for the purpose of cleaning the apparatus. Other suitable man-holes can be provided. Baffle plates such as 7 can be provided at various places in the casing to avoid the creation of deadspaces or eddies.

In the arrangement shown in Fig. 4c, the water tubes are passed through stulfing boxes consisting, for instance, of split rings 30 in the curved tube sheets 27., 27 and in the auxiliary curved tube sheet 5 spaced from the tube sheet 5, so that the connection joint connecting the pipe unit in series may lie wholly outside the hot gas passages.

The tubes will be preferably nested in staggered formation as shown in Figure 3 I and where the outer casing for practical reasons will be of cylindrical or other uniform cross section, it will be preferred to provide internal false walls 31, which follow more closely the contour line of the nesting of the tubes, thus providing that'the air space around all tubes is substantially uniform, and avoiding all dead spaces in the air space. Heat lagging 32 can be provided between these false walls, and the outer casing to 1 present the loss of heat energy from the flue gas. Y

As the air passes through the heat interchanger, it will be desirable to modify either continuously or in steps the cross sectional area of passage-way presented to the flue gas, or the air or both. This cross-sectional area increases to afford space for the volume of air as it increases in consequence of the heating. Practically it will be-more usual to effect this in steps. This may conveniently be efiected byfor instance, providing a baffle plate 33 (Figs. 5'and 6) extending across the casing and dividing this into unequal cross sectional area of flow to the air.

so that as the volume of the gas diminishes as it cools, a corresponding change in crosssection is provided to provide substantially the same velocity of flue gas flow through the apparatus.

A convenient form of joint whereby the water tubes can be connected in series to one another is shown in Figure 7 in which a pair of tubes 2 are connected by a header 43. The tubes are slotted at 44 to allow free unrestricted flow of water therethrough, and the tubes are tapered at A5 and flexible packing a8 inserted between them and the header 43. Closing capst'l allow direct access t'ojthe tubes 2 and maintain a tight joint on the packings 46, 4:8. V

I declare that what I claim is 1. A heat 'interchanger comprising a casbattles in the path of said gases'l'ea'ving said tubes to maintain the velocity and smooth eddyless flow of said gases, and means to pass water through said water tubes in contraflow to said hot gas.

2. A heat interchanger comprising in combination a casing, end plates spaced from the ends of said casing, hot gas flues between said end plates, hot gas inlet and outlet connections to said casing between one of said end plates and the end of said casing, interconnected fluid tubes within said hot gas iflues, and detachable baffle plates within said casing in the path of the hot gases between the inlet and outlet openings and one of the said end plates.

3. A heat interchanger comprising in combination a casing, transverse end walls -in said casing to provide a hot gas header at each end of said casing, a plurality of hollow-cored members comprising inner and outer conduits extending between said end walls so that the outer conduits open into said headers, means to connect said inner conduits in series, means bination a casing, hollow-cored members therethrough comprising inner and outer conduits, said casing and conduit providing inner, middle and outer passages, means to pass hot gas at high velocity through said middle passage, means for forcing air under pressure through said outer passage, said outer passage increasing in cross sectional area from inlet to outlet, and means to pass Water through said inner passage.

In Witness whereof, I have hereunto signed my name this 17th day of March 1927.

ALBERT EDWARD LEEK.

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