US 3369592 A
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Rib, 2Q, w L DEDQW Bgg REGENERATR FOR A REGENEHATIVE HEAT EXCHANGER Filed July 1, 1965 2" sneeisheei 1 .1. DEDOW 3,369,592
REGENERATOR FOR A REGENERATIVE HEAT EXCHANGER Feb. 20, 1968A 2- Sheets-Sheet 2 Filed July l, 1965 United States Patent O 3,369,592 REGENERATOR FOR A REGENERATIVE HEAT EXCHANGER loachim Dedow, Olpe, Westphalia, Germany, asslgnor to Apparatebau, Rothemuhle Brandt & Kritzer, Westphaiia, Germany, a company of Germany Filed July 1, 1965, Ser. No. 468,870 Claims priority, application Germany, July 16, 1964, A 22,110 3 Claims. (Cl. 165-10) A regenerative heat exchanger includes, inter alia, a heat exchange member, referred to herein as a regenerator, which comprises a casing containing a mass of plates or tubes which provide passages through the regenerator, hot gas being led through said passages in order to give up its heat to the said mass, Whereafter air is led through the same passages in order to pick up the -heat from the said mass.
The present invention relates to such regenerative heat exchangers, and particularly to a regenerator thereof which comprises a mass of plates, the mass being provided by plates provided with or forming proturberances and hereinafter referred to as protuberant plates, alternating with other plates, the alternation of plates thereby forming the passages, such a regenerator being referred to hereinafter as of the -kind referred to.
Efficient heat exchange between the flowing media (hot air or cold gas) and the mass of heat-storing plates, consonant with keeping the costs and space requirements of regenerative heat exchangers of the kind specified as low as possible, depends upon how closely the plates can be placed together. The gas flow channels formed between the plates are therefore required to have very small hydraulic radii-as a rule, something of the order of from 3 mm. to 10 mm. At the conventional gas speeds of from to 15 metres per second, hydraulic radii as small as this lead to laminar ow which is associated with a much poorer heat exchange than is a turbulent ow. The designing of the shape yof the passages in the mass is therefore mainly directed towards so affecting gas and air flow that heat exchange coetlcients substantially the same as for a turbulent How are produced. To this end, various kinds of protuberant surface shapes of the plates are used, such as corrugations extending inclinedly or transversely of the gas tlow, lor corrugations which extend in different directions from one another and which produce Ia wallie effect. It has also been proposed to provide the protuberant plates with dimples, pimples or other projections or indentations at suitable intervals and spacing. Unfortunately, the protuberances reduce the free flow crosssection in the narrow gas passages lbetween the plates, and therefore red-uce the plate packing density correspondingly, with the result that the dimensions of the exchanger must be increased, with a corresponding higher cost. Another disadvantage of these protuberances is that they encourage deposition on to the plates of fly ash or other impurities in the flowing media, more particularly in cases where a precipitation of moisture on to the plates occurs because of the temperature dropping below dew point, which results in encrustation of the impurity.
The object of the present invention is to provide an improved regenerative heat exchanger regenerator of the kind referred to.
According to this invention, a regenerative heat exchanger regenerator comprising a casing, a mass of plates within the casing and providing passages through the regenerator extending between opposite ends of the regenerator, the mass of plates comprising protuberant plates alternating with other plates to form the passages, is characterised in that the protuberant plates are corrugated to provide a substantially stair-like section, the
walls of the corrugations between adjacent ridges and furrows 4being substantially straight in section, each wall being displaced at positions along its length to provide steps extending transversely of the wall between adjacent ridges and furrows, the protuberant plates :being positioned within the regenerator with the ridges and furrows extending in the direction from one of the opposite ends of the regenerator toward the other end.
One embodiment of the invention is shown in the accompanying drawings, wherein:
FIG. 1 is a perspective -View of part of a regenerator of the kind referred to;
FIG. 2 is a perspective view of an assembly of a flat plate, a protuberant plate, and a part of another flat plate;
FIG. 3 is a plan view of a protuberant plate; and
FIG. 4 is a sectional elevation of a protuberant plate, on an enlarged scale, taken on the line IV-IV in FIG. 3.
FIG. 5 is a perspective view of an assembly of a shallowly corrugated plate, a deeply corrugated protuberant plate, and a part of another shallowly corrugated plate.
A regenerator comprises a casing 11 containing a mass 12 of plates disposed so as to provide passages 13 extending from one end 14 of the regenerator to the opposite end 15.
The mass 12 of plates comprises deeply corrugated protuberant plates 17 alternating with other plates 16.
The protuberant plates 17 are deeply corrugated so that the plates have the section seen at the bottom end of FIG. 2, with ridges 18 and furrows 19, the walls 20 and 21 being substantially straight between adjacent ridges and furrows.
Each wall 20 and 21 is displaced at 22 for a distance along the wall whereby to form an ascending step 23 at one end of said displacement and a descending step 24 at the other end of said displacement. The displacements in the two walls 20 and 21 extending from a furrow 19 or a ridge 18 are such that the ascending step 23 in one of the two walls is at one end of the displacement in the wall Vwhile the ascending step 23 in the other of the two walls is at the opposite end of the displacement in the other wall, relative tothe direction of the passages 13 and to the gas or air flow therein.
The rise of each of said steps 23 and 24 extends along the plate for a distance s shown in FIG. 3. The depth of said rise is shown at b in FIGS. 3 and 4.
The extent `of the displacement 22 along the plate, that is in the direction of the ow of gas or air through the regenerator, is indicated at a in FIG. 3.
The other plates (16 in FIG. 1) which alternate with the deeply corrugated protuberant plates 17 may be at and smooth plates, as shown `at 25 in FIG. 2, :but preferably they are shallowly corrugated plates 'as shown at 26 in FIG. 5, the furrows 27 and ridges 28 of the corrugations extending substantially diagonally of the plates so that they cross the ridges 18 and .furrows 19 of the plates 17 at an angle.
The stepwise displacement of the walls of the, corrugations causes very little reduction of the free cross-sections of the gas flow passages 13 between the plates, so that for given operating conditions a high plate density can be obtained. Another advantage has to do with the manufacture of these stepped plates. The conventional plates with pimples or dimples cause heavy wear of the rolls used to form the plates. The rolls have pins for impressing the pimples or dimples into the plates during rolling, but pimple or dimple impression is unsatisfactory and the depth to which the pimples or dimples are impressed decreases rapidly as the pins wear. The improved plates lead to a .better process for manufacturing them. They are produced by means of rolls in the form of individual discs which are displaced relatively to one another. Roll wear is relatively reduced, and the displacement of the walls 3 of the corrugationsof the platescan be applied to plates having small corrutgation depth, leading to llarge plate group density in the mass .12.
The displacements 22 in the plates 17 disturb the flow of gas or air over a wide front instead of just atdiscrete places, as in the case `ot pimples or dimples, and therefore provide regularly repeated cavitation eddies which,
as well as breaking iup the laminar boundarylayer, are
strong enough to extend over the whole width of the passage cross-section where there is also, of course, a laminar flow. The reason for this considerable effect on flow is that the step rise b of the ow cross-section occurs over a relatively short ow distance a.
Experiments have shown that to produce su'lciently strong cavitation eddies in the range of conventional gas speeds, the steps need to be based on the following approximate dimensional relationships:
Rise of steps 11:0.15 r to 0.70 r; Longitudinal extent `of steps s=0.l5 r to 0.70 r; Length a between steps=5 r to 50 r;
where r==hydraulic radius of passages 13.
What I claim anddesire to secure by Letters Patent is:
tions on one said wall which ascends on vboth sides of said intermediate portion and for-rn on opposite ends descending step portions, the other side wall having step portions which descend transversely at opposite ends, said plates being disposed in said casing so that the ridges and furrows extend in the direction from one of the oppo-z site ends of the regenerator to the other.
2. The improvement according to claim 1 Whereinthe other plates which alternate with the deep corrugated protuberant plates are corrugated protuberant plates having a shallower cornugation relative to the `deep corrugated protuberant plates.
3. The improvement according tov claim 2 wherein the shallower corrugationsin the alternate plates extend substantially diagonally of the deep corrugated plates.l
References Cited 1 UNITED STATES PATENTS 1,808,921 6/1931 Frankl 165-10 2,023,965 12/1935 Lysholm 165-10 X 2,066,779 12/1936 Przyborowski 165-79 2,647,731 8/1953 Ludlow 165-152 Xr 3,262,495 7/1966 Baird 165-152 FOREIGN PATENTS t 542,570 l/ 1942 Great Britain. 750,303 6/1956 Greatv Britain.
ROBERT A. OLEARY, Primary Examiner.
MEYER PERLIN, Exmnzner.
T. W. STREULE, Assistant Examiner.
UNITED STATES PATENT OFFICE CERTIFICATE 0F CORRECTION Patent No. 3,369,592 February Z0, 1968 Joachim Dedow It is certified that error appears in the above identified patent and that said Letters Patent are hereby corrected as shown below; I
Column 4, line 21, "2,066,779" should read 2,066,279
Signed and sealed this 10th day of February 1970.
Edward M. Fletcher, Jr.
Attestng Officer Commissioner of Patents WILLIAM E. SCHUYLER, JR.