US2240203A - Heat exchanger - Google Patents

Description

April 1941- w. H. ARMAcpsT V 2,240,203

' HEAT EXCHANGER Filed Nov. 25, 1938 l/VLE T 0U TLE T AIR M547 RESAm/W STEEL INLET I 646 INVENTOR W/LBUR fl HRMACOST.

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ATTORN EY Patented Apr. 29, 1941 UNITED STATES PATENT OFFICE HEAT EXCHANGER- Application November 25, 1938, Serial No. 242,363

1 Claim.

The present invention relates to improvements in heat exchangers and particularly to plate type exchangers in which a fluid to be heated, such as air, flows through passages extending in directions transverse to the flow of the heating gases which may be derived from a boiler.

In this type of heater the portions of the plates which are located nearest to the source of the heating gases frequently become oxidized and burnt due to the high temperatures to which they are subjected. An object of the present invention is to eliminate or at least reduce the oxidation and burning of these portions of the plate elements of the heat exchangers.

The invention will best be understood upon consideration of the following detailed description when read in conjunction with the accompanying drawing inrwhich the single figure is a diagrammatic representation of a plate type heat exchanger embodying the invention.

In the drawing the numeral l designates a conduit through which gases flow in the direction indicated by the arrow from a furnace or the like to an outlet or stack. Interposed in this conduit are a pair of heat exchangers II and I2 arranged in series so that the gases flow first through the exchanger H and then through exchanger l2. The heat exchangers are of the well known plate type familiar to those skilled in the art and have passages alined with the conduit Ill for the flow of heating gases alternating with transversely extending passages for the flow of the fluid, such as air, that is to be heated.

The air to be heated initially enters the exchangers at I3 and passes from the outlet M of the exchanger |2 to the inlet l5 of the exchanger H through a duct I6 having walls I! and 8 and located out of the path of the heating gases. Extending longitudinally or axially through the duct I6 is a partition 20 so arranged that the air passing over the parts of the exchanger |2 which are most remote from the source of heat in the direction of gas flow are directed to and pass over the portion 2| of the plates in the exchanger l which are nearest to the heat source in the direction of gas flow. The end of portion 2| of the partition 20 adjacent the exchanger |2 extends transversely across the air passages of this heater and ,is pivotally supported at 22 near this end so that air from an area of greater or less extent may be diverted from the relatively cool portion of the heater l2 through the subdivision 23 of duct l6 formed by the outer wall I"! and partition 20 to flow over the hottest portion 2| of the plates in the heater As illustrated an additional partition 24 is provided in the duct l6 forming further passages 25 and 26 through which air from the relatively cooler portions of the exchanger I2 is directed to portions of the exchanger II which are subjected to cooler gases than pass over the most intensely heated section 2|.

As a further means for reducing the cost of economizers of this type, while at the same time afi'ording protection against the hot gases encountered in service, the plates of the exchanger 2 may be made of carbon steel while the portions 2| of the plates of the exchanger II that are subjected to the hottest gases may be made of a heat resistant alloy such as a steel including 18% chrome and 8% nickel while the more remote portions 24 of the plates of the exchanger I may be of 5% molybdenum steel alloy. The plates of the exchanger l2 and the portions 2'! of the plates in the exchanger II are shown corrugated while the most intensely heated portions 2| of the plates in the exchanger II are indicated as of plain construction, 1. e. not corrugated.

It will be seen from the foregoing that in service the portions 2! of the plates in the exchanger II that are subjected to the hottest gases are protected by receiving air which has previously had its temperature increased the least because of its passage through the portion of the exchanger |2 that is most remote from the source of heat in the direction of gas flow, i. e. by air which has been heated by transfer of heat from gases which have been cooled considerably in passing over the plates in exchanger H and I2 that are nearer to the source of heat.

What I claim is:

In heat exchange apparatus; a conduit for the passage of heating gases; a pair of heat exchangers each having passages for the flow of a fluid to be heated, such as air, in a direction transverse to the flow of the heating gases, said exchangers being arranged in series in said conduit so that the heating gases flow through said exchangers in succession; a duct located out of the path of the heating gases and connecting the air outlet of one heat exchanger to the air inlet of the other heat exchanger so that the air passes through said exchangers in a direction generally counter to that of the heating gases; and a partition extending longitudinally of said duct and so located as to direct air from the portion of said one exchanger that is last contacted by said heat-- ing gases to the portion of said other exchanger that is first contacted by the heating gases; and means movably supporting the portion of said partition having an end edge adjacent and extending across the air passages at the outlet of said one exchanger so that said partition portion may be moved to direct air through said duct from an area of larger or smaller extent at the air outlet of said one exchanger.

WILBUR H. ARMACOST.

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