US1891879A - Heater suitable for gaseous fluids - Google Patents

Description

Patented Dec. 20', 1932 UNITED STATES PATENT OFFICE ALEXANISRE FOLLIET AND NICOLAS SAINDERICHIK, F PARIS, FRANCE HEATER SUITABLE FOR GASEOUS FLUIDS Application filed December 26,.1930, Serial No. 504,818, and in Trance' December 80, 1929.

This invention relates to heaters suitable for gaseous fluids. At the present time, many different kinds of apparatus are known for heating air or reheating or superheating steam, but in general such apparatus comprises banks of tubes traversed by the gases to be heated and placed in a chamber through which gaseous products of combustion pass.

Apart from the devices used for facilitating the transfer of heat, (such for example as the use of refractory masses inside the tubes) difliculties are experienced in uni; formly dividing the flow of gaseous fluid to be heated or to be superheated through a large number of tubes in parallel.

Moreover, arising from the actual construction of such apparatus, the distribution of the heating medium through the apparatus is very irregular, this disadvantage bein particularly noticeable in the latest forms 0 apparatus employing gas or oil burners.

The use of refractory tubes, such as fused quartz, was abandoned at an early stage of develo ment on account of their fragilit at the di erent working temperatures, and t eir very low coefficient of thermal conductivity. The use of calorized steel tubes, special cast irons, chromed tubes, and so forth, led to an improvement from the point of view of strength and duration, but did not permit a high temperature and a satisfactory thermal efliciency to be obtained in a manner both practical and economical.

Considerableprogress, especially from the point of-view of efiicient utilization of the available heating surface was made, especially in the superheating of steam, when the tubes instead of being traversed in parallel, were traversed successively in series.

Nevertheless, no real solution has been found to the problem of heating gases continuously and uniformly and with aghigh thermal efliciency to a temperature of 800 C. or more without deterioration in the strength of the tubes.

With the object of overcoming such difiiculties, the present invention consists in fluidheating apparatus comprising the combinaline 4 -4: of Figures '1 and 2 and v tion of elements hereinafter described and particularly pointed out in the claims.

The accompanying drawing illustrates a form of construction of the invention by way of example inwhich use is made of weldless steel tubes bent as shown and traversed by the hot gases in two sets in parallel, the fluid to be heated (air or other gas or steam) passing in succession from the coldest to the hottest part of each set of tubes.

Figure 1 is a longitudinal sectional elevation, showing the devices for admitting and burning the heating gases and the means by which the upper part of one tube communicates with its neighbour;

Figure 2 is a vertical section taken on the line-,22 of Figure 1, showing in side view the shape of the curved tubes, the tube headers, and the apertured plate for the production of thin sheets of gas in the spaces between the suspended tubes;

Figure 3 is a sectional plan taken on the line 3-3 of Figure 1; while finally Figure 4 is a sectional plan taken on the Figure 5 a sectional plan on the line 5-5 p of Figure 1, of the last chamber communicating with the chimney.

According to'the formshown, the gases to be heated enter the apparatus through the inlet, 2, and after reaching a high temperature, leave by the outlet, 3, traversing in their passage the tubes, 4, curved as shown and arranged in two sets in parallel.

In the example under description, fuel is burned on the grate, 5, the roducts of combustion passing from the urnace, 6, to the adjoining chamber, 7, to receive a first supply of secondary air by Way of the valve, 8, and duct, 9.

Alternatively, if desired, the grate, 5, may be replaced by burners using coke-oven or other gas, or by heavy-oil burners.

From the chamber, 7, the heating gases pass through the plate, 10, provided with narrow slots,11, arranged parallel to onegases rise between the rows of 'tubes, 4, in 9 the form of thin sheets of gas producing a maximum heating eifect on the surfaces of the tubes, 4, without directly impinging thereon.

' A further supply of secondary air is in-', troducedby way of the valve, 12, and refractory tubes, 13, the upper. part of the latter being provided with transverse saw cuts, 14, spaced so as to alternate with the parallel rows of tubes, 4.

2 ed from one tube to the next, so that the gases pass in series through all the tubes of the same set, these headers being secured by any suitable means to the bottom tube plate of the closed chambers, 17. If desired, they may be replaced by any other fluid-tight device, which connects one tube with the next in order to obtain a circulation of the gas to be heated through each of the tubes in succession of the same set.

It will be noted (see Figures 1, 3 and 5) that the groups of tubes, 4, in the heating chambers are connected by U-s haped stirrup connections, 20, to the'right-hand flue, 18,

5(forming a heat-insulated chamber) and to the left-hand chamber, 19, leading. to the chimney.

The course of the heating gases after passing through the slotted plate, 10, is thus up.- wards through the chamber, 21, where combustion is practically completed, through top connecting duct, 22, downwards through chamber, 23, through bottom connecting duct, 24, upwards through chamber, 25, through top connecting duct, 26, and downwards through left-hand chamber, 19, and so through the duct, 27, to the chimney.

The heating gases therefore move on the whole from right to left.

The gases to be heated, on the contrary, pass in parallel through the two sets of tubes, 4, on the whole from left to right, communication between the tubes, 4, in adjacent chambers being effected by the connectingpipes, 28, 29and 30 as shown."

By virtue of the arrangement described above, the tubes with the header to which they are attached can be quickly removed for repairs. As the ends of the tubes are rolled into the bottom tube plate of the header, or otherwise secured thereto, the tubes and headers can be removed as a unit, and with a complete spare unit available a change can be effected with a minimum of delay. In this way without interrupting the working of the apparatus, the necessary time is available for repairing or replacing worn tubes in the unit removed.

The upper part of the apparatus and also the connections and external portions of the tubes are covered with a layer of suitable heat-insulating material.

The object of the curves given to one of the branches of each tube, 4, is to provide a large heatingsurface in a series of vertical parallel planes and to obtain as uniform a heating as possible of the gas passing through these bends.

The invention-is, however, in no way limited to this particular way of bending one of the branches of each tube, 4, and any other curves in a vertical plane may be adopted without departing from essential principles of the invention.

In accordance with the present invention, it will be seen that the gases or vapours to be heated pass in succession through all the tubes of a set and are heated gradually and uniformly while their velocity increases correspondingly,their maximum temperature being attained when they reach the righthand end chamber.

The eflective thermal efiiciency of such an apparatus is very high, on account of the large tube surface disposed in vertical paralll planes and subjected to the energetic heat radiation of the thin sheets of burning gas, while at the same time the difl'erence between the temperature of the heating gases and that of the gases to be heated, it may be c to 800 C. or more, is always less than 200 C.

The leaving temperature of the heating gases, measured at the damper at the foot of the chimney, is of the order of 150 C. in the case of air heated to 800 Q.

We claim: 1. Fluid-heating apparatus, comprising in combination a series of tubes arranged in parallel vertical planes and spaced apart to contain the fluid to be heated, and means disposed below said tubes 'for introducing between said tubes and without contact therewith thin moving sheets of a heated gaseous medium to heat said tubes by radiation, said introducing means including a plate and a series of slot-like nozzles alternating in position with said vertical planes.

' 2. Fluid-heating apparatus comprising the combination of elements claimed in claim 1, together with a furnace, gaseous products from which serve as said gaseous heating medium and means for adding air to said gaseous products at a certain distance from said introducing means, said adding means having spaced. air-supplying deliveries coinciding in position with said thin gaseous sheets.

Fluid-heating apparatus comprising the combination of elements claimed in claim 1, 7

together with a furnace, gaseous products from which serve as said gaseous heating medium and means for adding air to said gaseous products at a certain distance from said introducing means, said adding means including an air-supply duct arranged transversely of said arallel planes and elongated apertures in said duct disposed parallel to said parallel planes, said apertures coinciding in position with said thin gaseous sheets and delivering air in the upward direction in which said thin gaseous sheets flow.

4. Fluid heating apparatus comprising the combination of elements claimed in claim 1, in which said slot-like nozzles converge to a Width less than the clear distance between said tubes arranged in said parallel vertical planes.

In testimony whereof we have signed our names to this specification.

ALEXANDRE FOLLIET. NICOLAS SAINDERICHIN.

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