US1703793A - Heat regenerator with large surface - Google Patents

Description

Feb. 26, 1929. 1,703,793

C. M. STEIN HEAT REGENERATOR WITHLARGE SURFACE Filed Aug. 8, 1924 Fig. 4

INVENTOH Patented Feb. 26, 1929.

VCHARLES M. STEIN, or PARIS, FRANCE,

PATENT OFFICE.

YASSIGNOR '10 socIE'rE. ANONYME ims APPAREILS DE MANUTENTION & FOUR-S STEIN, 0F PARIS, FRANCE, A CORPORA- TION OF FRANCE.

HEAT REGENERATOR WITH LARGE SURFACE.

Application filed August 8, 1924, Serial No. 780,998, and in France August 31, 1923.

This invention relates to improvements in the construction of heat regenerators for the purpose of providing them with a very large heating su-rface and, a high velocity of circulation of the fluids passing through them.

As is known it is necessary to provide a certain heating surface in order to obtain satisfactory recuperation of the calories contained in the flue gases.

The extent of this heating surface obvious- 1y depends, for a given set of conditions, on the Value of the coefficient of transmission of heat between the gaseous fluids and the refractory brickwork forming the regenerator chamber. transmission increases with the speed of circulation of the gaseous fluids. It is therefore advantageous to increase the speed of circulation so as to reduce the heating surface required to obtain a predetermined degree of recuperation.

But on the other hand in order to increase this velocity it becomes necessary to reduce the surface of the section of the passage for the gaseous fluids which entails areduction of the perimeter, If, therefore, the velocity is increased it will be necessary on the onc hand to reduce the length of the heating surface since'the said heating surface is decreased, whilst on theother hand the length should be increased, since the width of the heating surface (repre sentcd by the perimeter of the section of the passage) is reduced. Now, the coefficient of transmission and consequently the heating surface is less than proportionate to the square root of the velocity, whilst the perimeter of the section and consequently the length of the heating surface is in inverse ratio to that square root. It follows that the effect of reducing the perimeter is contrary to that required and that the result obtained leads to a variation in the length of the heating surface in the same sense as thatof the velocity.

\Vhen, therefore, the velocity-of the gaseous fluids circulating in an apparatus for the recuperation of heat is increased a reduction of the requiredheating surface is certainly obtained, but at the same time it will be found necessary to increase the length of the pas sage of the gaseous fluids which will involve in general an increase in the bulk of the ap- It is known that this coefficient of paratus and will consequently lead to an effect exactly opposite to that in view by increasing the velocity. I

It is for this 'eason in conjunction with a consideration of the increase in the losses of the charge with the velocity that in recuperating apparatus as hitherto-constructed only a low velocity of circulation of the gaseous fluids is employed (as a rule 1 to 2 metres per second).

The object of the present invention consists substantially in providing an apparatus which enables a considerably higher velocity of circulation to be obtained (6 to 12 metres per second) in combination with a reduction in the total bulk of the recuperator. 1

This arrangement is such that for a given velocity, that is to say for a given section of the passage for the gaseous fluids, the perimeter is a maximum with the object of reducing to a minimum the length of the pars sage of the said fluids. This result is obtained in practice by the employment of very flat sections. for the passage which has thev additional advantage that all the thin streams of fluid, laminated in this manner, are in contact with the heat transfer surface.

The characteristic feature of the system is therefore the provision of alarge surface for the recuperation of the heat combined with a small volume owing to the method of arranging the refractory walls that serve for the transfer of heat.

These walls are arranged parallel one to another and very close together so that a very thin stream of fluid passes between them which has the advantage of facilitating the transfer of heat in all the gaseous filaments of the said stream.

The several passages are arranged-in a zigzag manner and the gaseous fluids flow through them in succession so that a considerable length of passage is obtained although the distance between the two ends of the circuit is a minimum. v

The accompanying Figures 1 to 5 show the various methods of carrying out the inven- Figure 2 is a section of the elements constituting the recuperator, showing the joints thereof.

Figures 3, 4 and 5 show examples of ele mentswith corrugated walls.

Referring to Figure 1, 1t must, of course,

' be understood that the elements which are tremities and the corresponding face of the said chamber. The vertical passages 3-3 are staggered in order to obtain the desired zig-zag circulation.

'The plates shown in Figure 1 have plane faces but several other methods of construction of these plat'es constitute-also the object of the invention. Thus, for example, with the object of increasing the perimeter of the section of the passage (and consequently re ducing the length of the passage of the fluids) one may use plates provided with alternate projections on both faces of rectangular or square section, Figure 5, or even hemispherical, Figure 3. Finally, plates having both faces of wavy outline, Figure 4, may be used with the same object 1n v1ew.

The method of constructing the plates is one of the characteristic features of the invention. For example, if the arrangement according to Figure 1 with horizontal walls is adopted, each plate consists of a seriesof' elements 11, Figure 2, of the required thickness and provided with four feet 22 of a height equal to the space required between the successive plates.

For the purpose of making a tight ointbetween two adjacent elements the four vertical faces of these elements are formed midway of the thickness with a feather on two of the adjacent faces sothat when two elements of the same plate are in contact the feathers of the one will engage in the grooves of the other and vice Versa.

The elements .are therefore all interchangeable which enables any desired plate to be constructed, very rapidly, and the plates to e be built one above the other, as shown in Figure 1.

It may be added that the increase in thc rcsislance owing to the restricted passage provided for the gaseous fluids will be compensated by employingmechanical blowing of the air and mechanical extraction of the gases, which in this case has no disadvantage .since we are dealing with a heatrecupcrator and there is no fear of mixing owing to the difference in pressure between the two circuits of air and gases.

In con'iparison with standard regenerators, which are normally built of bricks 22 x 11 x 16 cm., arranged to provide passageways about 5 .cm. wide, the number of passageways and the lengththereof depending on the volume of gases and the amount of heat transfer desired, a regenerator according to applicants invention would have a passageway approximately 40 x 3 cm., the length'being designed in accordance with the heat exchange requirements.

Experience has shown that a decrease in one of the flow area. dimensions to produce an increase in speed of 6 meters per second in applicants regenerator, as compared to the normal speed of 1 meter'per'second in the usual types of standard regenerators, increases the heating surface and destroys the film of hot gases normally clinging to the heating surfaces, thus facilitating the heat exchange between the gas and the surface.

Claim:

In a; regenerator, uniform gaspassageways highly restricted in cross-sectional area as compared to the standard,inorder.to induce an increased velocityof gas flow over the normal of at least two to one, the walls ofsuch )assa ewa shavin alternate )ro'ectionsanddepressions to provide an enlargement'of the heating area.

In testimony whereof I aflix my signature.

' CHARLES M. STEIN.

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