US1673418A - Heat-exchange apparatus - Google Patents

Description

June 12, 19280 A T. W. MUNFORD HEAT EXCHANGE APPARATUS Filed April 9, 1926 yvvM-mz V aw;

WI T/VAS'SES Patented June 12, 1928.

UNITED STATES PATENT OFFICE.

THEODORE W. MUNFOBD, OF PITTSBURGH, PENNSYLVANIA, ASSIGNOR TO MAN'I'IiE ENGINEERING COMPANY, A CORPQRATION OF I'ENNSYLVANIA.

HEAT-EXCHANGE APPARATUS.

Application filed April 9, 1923. Serial No. 100,844.

This invention relates to heat exchange apparatus and more particularly to the type used in connection, with a flue chamber or the like for the purpose of utilizing the heat of combustion gases for the urpose of raising the temperature of a fluid such, for example, as air passed through the apparatus.

Although the most-form eflicient of heat exchanger is the straight counter flow type,

in which .the direction of flow of the fluid passing through the apparatus to be heated 1s 0 posite to the direction of flow of the heating gases, this t pe has certain practical disadvantages whic result from the fact that that part of the apparatus which is exposed to the highest temperature of the heating gases is also the part conveying the hottest fluid to be heated with the result that the temperature of the material from which the heat exchanger is constructed at that point may be so high as to materially reduce the effective life of the structure. In view of the fact that the counter flow type of heat exchanger insures the greatest mean temperature difference between the fluid to be heated and the heating gases, this type of apparatus takes the greatest advantage of the convected heat but fails, on the other hand to efliciently utilize the radiant heat available from sources outside of the heating gases such, for example, as the brick settings of the associated flue chamber or the like, and this is due to the fact that such heat is most intense at the point where the heating fluid enters the apparatus which, in a counter-flow type, is also the point where the fluid to be heated is hottest so that the heat transfer at this point is relatively low, due to the fact that, as stated in Stefan- Boltzmanns law, the rate of heat transfer by radiation from a hotter to a cooler bod is proportional to the difference in the fourt .powers of their absolute temperatures.

An object of this invention is to rovide a heat exchange apparatus of suc construction and arrangement that the flow of fluid to be heated through that part of theapparatus subjected to the highest temperature can be given a predetermined characteristic such, for example, as quantity flow,

regardless of the total flow through theapparatus.

A further object is to provide a device of the type set forth of such construction and arrangement as to obtain the utmost effect of the'radiant heat of the associated structure and at the same time maintain the greatest mean temperature difference between the temperature of the heating gases and that of the fluid to be heated so as to obtain the most .efiicient transfer of heat.

These and other objects which will be obvious to those skilled in this particular art are attained b means of this invention, one form of whic is illustrated in the accompanying drawing, which shows a sectional vlew through part of a heat exchange apparatus constructed in accordance with one embodiment of this invention.

The particular embodiment of this inventiouwhich has been chosen for the purposes of illustration includes a fluid transmitting chamber or section provided with an arrangement of conduits or passages through which the fluid to be heated, such as air, is passed. Two passages are provided adjacent that end of the structure which is sub jected to the highest temperature, the bottom in the illustrated form, and these passages are associated in parallel relation for the transmission of separate streams of fluid directed thereto from separate inlets. Each passage leads to the same duct or manifold where the two streams are united and through which they flow to a third passageway positioned in series relationsh1p with the preceding passageways and from which the fluid is carried to the outlet of the apparatus. As illustrated, the two passageways in parallel relation are so formed as to direct the respective streams of air assing therethrough in a cross parallel direction with relation to the direction of the heating gases while the third passageway in series with the two preceding passageways is so formed as to direct the combined streams in a cross counter flow with relation to the heating gases. The direction of flow of the heatin between the assembled sections 19 indicated by the arrow A on r the drawing. Although the drawing illustrates a. single fluid transmitting section it will, of course, be apparent that any number of these sectlons can be assembled with proper manifolding to provide a heat exchange apparatus of any desired size, as more fully described in copending applications, Serial Nos. 41,135 and 100,862 filed July 2, 1925, and April 9, 1926, respectively.

As illustrated, each section is provided with a fluid inlet 5 associated with an inlet manifold 6 leading to an entrance 7 of a passageway or conduit 8 formed adjacent that end of the section which is subjected to the highest temperature both from the flue ases and the radiant heat of the associated ue chamber. The air flows through the passage 8 in a circuitous route formed by suitable positioned baflles 9 and also in a generally upward direction parallel to the flow of the heating gases and. thence outwardly through an opening 10 into a manifold 11. A baflle 12 is positioned in the manifold 11 opposite the opening 10 for the purpose of directing the stream of air issuin therefrom into the extreme end of the manifold 11 so as to prevent the formation of a dead air pocket in the manifold between the end thereof of the outlet opening 10 which would result in such a high temperature at that point as to cause rapid deterioration of the material forming the apparatus.

A second inlet 13 admits a separate stream of air to a second inlet manifold 14 leading to the entrance 15 of a second passageway 16 associated with the first passageway 8 in parallel relation and through which the second stream of air flows in a circuitous route formed by baflles 17 into an outlet 18 leading to the manifold 11.

The two streams of air issuing from the passages or conduits in parallel with each other combine in the manifold 11 to form a single stream of air which passes through an opening 19 adjacent the opposite end of the apparatus into a passageway or conduit 20 through which it flows in a circuitous route formed by baflies 21 in a direction counter to the flow of the heating gases. The stream emerges from the counter flow passage 20- through an opening 22 to a manifold 23 through an outlet duct 24 at the top of the device to an outlet 25. A valve 26 is associated with each inlet so as to provide a. means for separately controlling the flow of the parallel streams of air admitted to the apparatus and an automatic control for the separate streams of air can be provided as described in the copending applications, above referred to, to as to obtain flexibility of operation. I

It will be apparent that either or both sets of baflles 9 and 17 in the two lower passages or conduits 8 and 16, respectlvely,

can be omitted so that the respective streams of air will flow across the hot end of the apparatus in a straight cross current direction.-

By directin two streams of relatively cold air imme 'ately into the hottest part of the apparatus the utmost advantage is taken of the radiant heat of the flue gases and the associated flue chamber construction. The introduction of relatively cold fluid at this point maintains the material from which the apparatus is constructed at a temperature within safe limits and the most eflicient heat transfer is effected. At the same time the provision of a counter flow chamber in series with two cross flow chambers insures the greatest mean temperature difference between the heating gases and fluid passing through the ap aratus so that the utmost effect is obtained from the convectcd heat of the flue gases.

Although I have described a specific form of heat exchange apparatus it will be apparent that various changes, additions, omissions and substitutions can be made therein without departing from the spirit o.- the invention or the scope of the appendedclaims.

What I claim as new and desire to secure by Letters Patent is:

1. A heat exchange apparatus having in combination a lurality of conduits for the passage of fluid to be heated assembled in parallel relation for the passage of separate streams of fluid through that part of the apparatus subjected to the highest temperature and a counter flow passage in series with said conduits for directing the fluid issuin from each of said conduits in a direction counter to the flow of the heating gases.

2. A heat exchange apparatus having in combination, a conduit for directing a'stream of air thro h that part of the apparatus subjected to t e highest temperature, an inlet for admitting relatively cold air thereto, a second conduit adjacent said first conduit an inlet for admitting a separate stream of relatively cold air to said second conduit, an air duct, an outlet from each conduit thereto and a third conduit for directing the air from said duct through the apparatus in a direction counter to the direction of flow of the heating gases.

3. A heat exchange apparatus having in combination assages for conveying separate streams of uid to be heated through the hottest part of said apparatus, means for uniting said streams and a' passage for directing said united streams in a direction counter to the direction of flow of the heat ing gases with which said apparatus is associated.

4. A heat exchaplge ap aratus having in combination a plur ty 0 passages for conveying separate streams of air through that a direction counter to the direction of flow of part of the apparatus subjected to the highthe heating gases. est temperature, a duct to which said pas- In testimony whereof, I have hereunto 1 sages lead and wherein said streams are subscribed my name this 2nd day of April 5 united, an outlet and a passage between said 1926.

duct and said outlet for directing the united streams through a part of said apparatus in THEODORE W. MUNFORD.

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