US2694554A - Cooling unit - Google Patents

Description

Nov. 16, 1954 M, B. LEMESHKA 2,694,554

' COOLING UNIT Filed Dec. 30, 1948 I 3 Sheets-Sheet l L NN!!! lNVENTOR MILTON B. LEM E'SHKA ATTO Nov. 16, I954 M'. B. LEMESHKA 5 COOLING UNIT Filed Dec. 30, 1948. 3 Sheets-Sheet 3 EXIT/{IR TEMR um WIDTH W I INC/I55 v INVENTOR MILTON B. LEMESHKA RNEY United States Patent COOLING UNIT Milton B. Lemeshlta, Lancaster, Pa., assignor to Radio Corporation of America, a corporation of Delaware Application December 30, 1948, Serial No. 68,335

17 Claims. (Cl. 257-263) This invention relates to cooling or heat exchange units or devices through which a coolant is circulated and more particularly to such units or devices composed of a plurality of similar fins or blades radially disposed about a common axis and through which the coolant is circulated generally in a longitudinal or axial direction.

A fin structure which has been found to be considerably more efficient than those heretofore used forms the subject matter of a co-pending application and includes an elongated body portion transversely slit and expanded to form a plurality of transverse ribs. I found that by adopting the constructional features hereinafter more fully pointed out the operation of such a slit and expanded fin may be so improved as to result in a substantially more eflicient cooling device and one which is silent in operation.

When a coolant such as air is forced through a radiator having such ribbed or discontinuous surfaces, loud whistle-like tones can be produced, the pitch of which may be changed by varying the velocity of the air flowing through the radiator or cooler. Such whistling tones may become audible at a fraction of the rated air flow necessary to maintain the temperature of the objects such as an electron discharge device at the proper level. Furthermore, the whistling tones continue in such cases as the air flow is increased up through the full air flow rating. Such tones are highly objectionable since they increase in intensity as the size of the radiator is increased. In the case of devices requiring larger radiators the tone becomes so intense as to make it extremely uncomfortable for anyone to remain in the vicinity for any length of time. Such tones present a serious drawback in that an electron discharge device cooled by such a radiator may often be required to operate near or even in a broadcast studio.

Furthermore, in any finned or bladed heat transfer I device heretofore in use there is a decreasing fin temperature radially along the fin as the distance from the heat source increases. This is particularly undesirable in the case of electron discharge devices. Since the temperature of the exit coolant as it leaves the cooling device varies proportionately with the temperature of the surfaces over which it has passed, it is clear that a cross section of coolant taken at the exit will vary in temperature from a high corresponding to the portion of coolant closest the device to be cooled to a low for the portion most removed therefrom. Thus, the cooler portion of the exit coolant such as air is generally dissipated without being utilized while only the hotter exit coolant is directed against portions of the electron discharge device located downstream from the cooling unit.

Thus, a principal object of my invention is to provide a cooling device which is considerably more eflicient in operation than those heretofore used.

Another object is the provision of such a device which will operate free of objectionable noise.

A further object is the provision of such a device from which the exit coolant will have a substantially uniform temperature distribution.

Still other objects will appear as the-nature of my invention is more fully understood from the following description taken in conjunction with the'accompanying drawings wherein like parts are identified by identical numerals in the several views.

In the accompanying drawings, wherein are shown, by way of illustration, several of the embodiments which the present invention may take:

Figure l is an elevational view of a cooling system constructed in accordance with my invention;

Figure 2 is a top plan view on an enlarged scale of the radiator assembly shown in Figure 1 with the electron discharge device removed;

Figure 3 is a perspective view of one of the fins;

Figure 4 is a front elevational view of the fin shown in Figure 3;

Figure 5 is a top plan view of the fin shown in Figure 4;

Figure 6 is a sectional view through the line 66 of Figure 4;

Figure 7 is a fragmentary elevational view of a fin illustrating a second embodiment of my invention;

Figure 8 is a sectional view through line 88 of Figure 7;

Figure 9 is a fragmentary elevational view of a fin illustrating a third embodiment of my invention;

Figure 10 is a sectional view through line 1010 of Figure 9;

Figure 11 is a graph of the relation of the temperature ofdexit air across the cooler plotted against fin radius; an

Figure 12 is a graph of heat transfer coeificient of a fin plotted against rib width with air velocity held constant.

Referring now to the drawings in detail, Figures 1 and 2 illustrate one form which my invention may take when utilized in connection with an object such as an electron discharge device indicated generally at 15. The device 15 to be cooled has a radiator 16 disposed in heat transferring relation with respect thereto as will be clearly pointed out hereinbelow. As most clearly shown in Figure 2, radiator includes a core 17 which may enclose all or part of the object to be cooled. Though core 17 is shown as being substantially cylindrical, the core may take any desired form and as will be seen may even be dispensed with entirely. Radially disposed about the periphery of core 17 are cooling fins or blades 18 each of which may be similar in every respect one to the other.

One such fin 18 is shown most clearly in Figures 3, 4, 5 and 6, having a body portion or member 19, a mounting flange 20 along the inner side of the body portion or member and a spacer flange portion 21.

As stated, the inner edge of body member 19 is provided with a mounting flange 20 which may be integral therewith or connected thereto by any convenient means such as welding or the like. Flange 20 is struck up from body member 19 at a suitable angle with respect thereto and has a shoulder or bend forming an offset portion 20a (Figure 5) permitting the mounting flanges of adjacent fins to nest one with the other as is most clearly shown in Figure 2.

The body portion 19 of fin 18 has a plurality of heat transfer elements or ribs 22, 23 and 24 which may be formed by slitting member 19 intermediate its sides into a plurality of strips and then expanding alternate strips to form ribs which lie in a plane outside that of member 19. If desired, the ribs may be connected to member 19 over suitably formed openings by means of welding or other means as may be more convenient in the case of fins of considerable size. As shown in Figure 4, the heat transfer elements or ribs may increase in length in a downstream direction, the coolant traveling in the direction of arrows 25 the purpose of which will be more fully pointed out.

Cooling unit or radiator assembly 16 may be assembled by alining the fins with mounting flanges 20 in juxtaposition so that each flange nests with the preceding one. In such position the flanges may be connected to each other and to the core 17. The flanges, if desired, may be connected to each other and directly to the object to be cooled or apart thereof such as anode 36 in the case of an electron discharge device. When so assembled, the object to be cooled, device 15, and the radiator may be positioned in a forced air duct 37.

As pointed out hereinabove, a radiator having discontinuous or ribbed surfaces produces in operation whistlelike tones. I have found by analysis that such tones correspond to the organ pipe leading me to believe that the space or passage between adjacent fins 18, core 17,

' and the duct was acting in a manner similar to the space in an organ pipe, reinforcing and resonating vibrations harmonical-ly related to the natural "period-"of this *fin pipe. I further concludedthat the origin of the oscillation, as in the case of a pipe organ, was one or more ofthe: rib :edges. v(Dd-experimentingfurther, I found: that the lowermost ribs; that; is the first or second r-ibs farthest upstream rwithirespect io the direction of. coolant .fiow, were producing' the oscillations resulting in the: audible tones and served as the same type'of oscillatory:mechanism as. dQesL-the e'dge inrthe throat-.of -such-organapipes of the 'class referred to. Apparently,- therefore, a'istable system of vortices is formed between the lowermost rib edge'an'd: the origin of theainstream directed-upon said edge. This stableasystem' 'of* vorticesin the air stream provides the periodic compressional pulse which, when reinforced by apipe' harmonieallyrelatedto the frequency of the pulse; results' in a' sustaine'dtone.

To prevent the formation of*tones I provide each fin 18 with turbulence forming means (Figure 6) in the form of a substantially-V=shaped tab 26 having -arms' or- sides 27, 28 and-a-U shaped end' portion26aWhich-rnay be integral-with= bodyrneniber 19 as shown or connected thereto by means of welding or other suitable means. Tab 26 is locatedsuificiently close'-to the-lowermost rib 22 asto'prevenb theformatiomofstable'systems of vortices in the air stream afterit leaves the tabs 26 and before'it arrivesatthe-edgeof-'the 'lowermost rib. Fins provided with such turbulence forminguneans may be operated at. any. air. flow up to and even above the maximum rated fiow 'without'producingany whistling tones.

I have 'alsofound'that the length and widthof the ribs has a marked effect upon"the eificiency'of'the radiator or cooler. By'the width of aribI'wish to be clearly understood as'referring to'the dimension w (Figure 6) of each'r'ib in the directionbf air flow While by length I-wish to be understood as'referring'tothe dimension 1 transverse to thedirection'of flow (F igure'4) As 'will-"bemoted from Figure '4, ribs22 are of such length'and are'so"disposed"that substantially more of theirlengthextends'tothe right 'ofthe vertical center line of 'that'portion ofdin"18 than extends to the left. Thus the midpoint of any rib is clearly seen to be displaced radially outward-with respect to the center line of its corresponding portion offinflS.

Aspointed"outihereinabove, uniform radial air temperature across the. radiator is highly"desirable,particularly when an object suchas'electron discharge device is being cooled. Asfshown'in Figured. such a device rests in the radiator'f16 .by. means'ofan anodeflange 29 resting on a seat"30',(see' Fig.2) provided on the end of core 17. Above anodeflange29 is locate'dthe seal structure. 'Where "the surfacesare substantially uniform in a radial -direction,lthat is,.'in the .direc'tion outward from device .15, as. is the. case Where thei'fins have plane surfaces or where the surfacesof theJfins are provided with obstructions to. the flowof coolant which are spaced substantially uriifornilyin a radial .'direction then the temperature of thecoolant air .when it leaves the radiator will vary from a..minimum value at that part of the radiator having 'thegreatest ra'diusto a maximum value closest to 'the device 115. By,increasing the resistance to the airflow as the radiusfrom the object to be cooled increases, I secure.asubstantiallyuniform radial air temperature distribution. This is most clearlyshown in the graph of Figure 11 where curveA represents the radial temperature distributionofthe exit. air that is the temperature of the airasit leaves a. radiator. having fins of plane surface or uniformly distributed resistance to air flow. Point Oat the minimum point of this curve corresponds to the temperature .ofthatJexitair leaving the radiator at the greatest distance or radius from the cooled object. Point P- correspondsto thetemperature of the exit air closest to.the.cooled object. A fin and.electron discharge .device .is schematically indicated below the graph. Curve B is a similar. curve for theradial air temperature distributiomover .the .exit vof.:a radiator con strueted in accordance with myinventionypoint Q corresponding to the temperature .Of theeXitair leaving the radiator at the greatest radius from -the cooled object while pointR correspondsto the temperature of theexit air leaving the.radiator.atuthe shortest radius. From curve A'it-is :apparentLthatlthe coolest air is dissipated without serving .any useful function while in my construction where radialair temperature .is substantially "or "near 'the seal structure "of the electron discharge device 15.

I further increase the efiiciency of my fins and hence the radiator formed therefrom by using a rib width w substantially less than heretofore used. I have determined from tests that there is a threshold value for width w below which there is an accelerated rise in the heat transfer coefiicient (Ho) .of each:fin as width w is further decreased. In Figlre 12 is shown the heat transfer He (British thermal-units transferred per hour through one square foot of area per degree Fahrenheit temperature difference) against width w in inches with the air velocity held constant (V :K).

From an inspection of this curve it is apparent that there is a pronounced knee as width w is decreased from .3 inch to .1 inch. For widths above .3 inch there is relatively only slight variation in the heat transfer coefficient while below 3 inch slightdecreases in width w result in increasingly larger and-larger' gains in heat transfer coefficient. 'Thus, bemerely decreasing width wfrom .25 inch to .15 inch the-heat transfer coe'fiicient is in creased from approximately 'l9-to 25 or-somewhat better thana 30% improvement. The extent ot'which-width w may be decreased depends upon practical considerations of present machine-methods and the minimum'structural strength requirements-in accordance with the conditions under which the fin -or radiator assembly is to 'be operated.

Another construction embodying my invention is illustrated in Figures 7 and-8-where a"fin 31is providedwith ribs -32 having length-l and width w. At itslower'or upstream en'd,'fin '31 has :a'bent up or tongue portion'33 which has a substantial-tone *ornoise eliminating effect as compared to the samefin 31 without tongue'33. I find this form of turbulence former convenient where ribs 32 start close to the upstream end of the fin.

The turbulence former'may also take anotherform as in the 'case 'of finI-34, (Figures' 9 and 10) having ribs-35. The lower end offin' 34-is' bent 'up along a diagonalfline to form a lip '37. Byproviding fin 34 with lip'37 I eliminate audible tones which would otherwise bepresent when aradiator assembled with such fins is operated at its rated air flow.

On comparing fins31 and 34, it is apparent that 'ribs 32 are disposed with considerably more of their length to the right or radially outward of the fin vertical center line than ribs 35. Radiators constructed of these respective fins differ in operation under identical conditions substantially in accordance with the.curves.ofFigurelll. The radiator composedroffins -31 has a substantially more uniform exit air temperature distribution than the radiator composed of 'fins 34.

It should also .be.clearly..understood that in addition to changing the tone producing characteristics my turbulence formers also improve .the eificiency of resulting radiators as will'be apparent from thefollowing tabulation of a test conducted with one type of radiator constructed of fins without. and then with turbulence .forming tongues 33.

P. C.'F.'M. E- g Percent Cooler I without turbulence former .93 142 132 Cooler II with turbulence former .61 107 65:2 149:4

Where:

Ps=Static pressure: drop across the 'cooler r in inches of water C. F. M.=Air flow in cubicfeet per 'minute A. H. P. C.=Air horse powercoefiicient ls-x C.F. M.

ments of my invention and described it in detail with respect thereto, I do not wish to be limited to the exact construction set forth but desire to claim all modifications thereof that come within the scope of the appended claims.

What I claim is:

l. A cooling fin for positioning in a stream of coolant, comprising a body portion having an upstream and a downstream end and having a plurality of substantially similar heat transfer members thereon intermediate said ends, and turbulence forming means on said bodyportion and disposed intermediate said upstream end and the heat transfer member nearest thereto for forming greater turbulence in said stream than'formed by any one of said heat transfer members. i

2. A cooling fin for a cooling unit for positioning in a stream of air, comprising an elongated body member, a plurality of substantially similar heat transfer members on said body member, and a turbulence forming member disposed intermediate one end of said body member and said heat transfer members and for forming greater turbulence in said stream than any one of said heat transfer members, said turbulence forming member presenting a substantially greater surface area to said air stream in an upstream direction than any one of said heat transfer members.

3. A cooling fin for positioning in a stream of coolant, comprising an elongated body portion having a plurality of spaced transverse slots formed therein, a plurality of elongated ribs one for each of said slots and in registration therewith, the ends of each of said ribs being connected to said body portion, and a turbulence forming member connected to said body portion upstream of all said ribs for forming greater turbulence in said stream than formed by any one of said ribs, said turbulence forming members presenting a substantially greater surface area in an upstream direction than any one of said ribs.

4. A fin for a cooling unit for positioning in a stream of air with its axis parallel to said stream, comprising a body member, a plurality of heat transfer members disposed in spaced apart relation on said body member, and a member substantially V-shaped in cross section in the direction transverse to said axis disposed upstream of all said heat transfer members and for forming greater turbulence in said stream than any one of said heat transfer members, said substantially V-shaped member presenting a substantially greater surface area to said stream in an upstream direction than any one of said heat transfer members.

5. A fin as described in claim 4 wherein said substantially V-shaped member has a curved base.

6. A cooling fin for a cooling unit for positioning in a stream of air with its axis parallel to said stream, comprising a body member having an upstream and a downstream edge, a plurality of heat transfer members disposed in spaced relation on said body member intermediate said edges, said body member having a transverse slot intermediate said upstream edge and the heat transfer member nearest thereto, and a turbulence forming tab for forming turbulence in said air stream connected to said body member and extending into said slot.

7. A fin for forming a cooling unit by assemblage of a plurality of such fins, comprising a body member having an upstream end and a downstream end, a plurality of heat transfer members transversely disposed in spaced relation intermediate said ends on one side of said body member, and a tab for forming turbulence disposed on said body member intermediate said upstream end and the heat transfer member nearest thereto, said tab presenting a greater surface area in an upstream direction than at least the next adjacent heat transfer member 8. A fin for forming a cooling unit by assemblage of a plurality of such fins, comprising a body member having an upstream end and a downstream end, a plurality of heat transfer members transversely disposed in spaced relation intermediate said ends on said body member, said body member having a plurality of slots formed therein one for each of said heat transfer members, the slot for the heat transfer member disposed closest said upstream end extending beyond said transfer member and toward said upstream end, and means for forming turbulence comprising a tab connected to said body mem ber and disposed through said last mentioned slot.

9. A fin for forming a cooling unit by assemblage of .6 a plurality of such fins'comprising a body member having an upstream and a downstream'end, a plurality of ribs transversely disposed in spaced relation intermediate said ends on said body member, said body member having a plurality of slots formed therein one in registration with each of said ribs, the slot for the rib disposed closest said upstream end extending beyond said rib toward said upstream end, and a V-shaped tab for forming turbulence disposed in said last mentioned slot and having a curved base projecting on one side of the body member, one

.side of said V-shaped tab being connected along its length to said body member, the other side of the tab extending through-said slot.

10. A fin for forming a cooling unit by assemblage of a plurality of such fins comprising a body member having an upstream and a downstream end, aplurality of ribs transversely disposed in spaced relation intermediate said ends on'said body member, said body member having a plurality of slots formed therein one in registration with each of said ribs, the slot for the rib disposed closest said upstream end extending beyond said rib toward said upstream end, and a V-shaped tab for forming turbulence disposed in said last mentioned slot and having a curved end projecting on one side of the body member, one side of said V-shaped tab being connected along its edge to said body member, the other side of the tab extending through said slot and beyond the other side of body member.

11. A fin for forming a cooling unit by assemblage of a plurality of such fins, comprising a body member having an upstream and a downstream end, said body member having a plurality of transverse slots formed therein and spaced apart intermediate said ends, a plurality of ribs one overlying each of said slots and connected at the ends thereof to the end walls of said slots, and the portion of said body member from said upstream end to a point adjacent thereto and intermediate said ribs and said upstream end forming means for forming greater turbulence than any one of said ribs.

12. A fin for forming a cooling unit by assemblage of a plurality of such fins, comprising a body member having a plurality of transverse slots formed therein and spaced apart intermediate said ends, a plurality of ribs one overlying each of said slots and connected at the ends thereof to the end walls of said slots, each of said ribs being positioned on the same side of said body member, said body member having a portion of its upstream end upturned on said side for forming turbulence.

13. A cooling unit for an electron discharge device having an anode and for positioning in a stream of coolant, said unit comprising a plurality of similar fins adapted to be radially disposed about said anode, each fin having a plurality of ribs transversely disposed thereon, and each fin having means for forming greater turbulence in said stream than formed by any one of said ribs, said means being disposed upstream of said ribs.

14. A cooling unit for an electron discharge device having an anode and for positioning in a stream of coolant, said unit comprising a plurality of similar fins adapted to be radially disposed about said anode, a plurality of ribs transversely disposed on each of said fins and intermediate the radially inward and outward edges thereof, the center of the ribs on each of said fins being offset radially outward with respect to the axial center line of said fins, and means on each of said fins disposed upstream of said ribs and for forming turbulence in said stream.

15. A cooling unit for positioning in a stream of coolant, comprising an assemblage of substantially similar fins adapted to be disposed in spaced relation to form an assembled unit with circulating passages for said coolant between adjacent fins, a plurality of ribs transversely disposed on each of said fins and extending into said passages, and means on each of said fins upstream of said ribs for forming greater turbulence than any one of said ribs.

16. A cooling unit for positioning in a stream of coolant, comprising a plurality of substantially similar fins adapted to be disposed in spaced relation to form an assembled unit with circulating passages for said coolant between adjacent fins, each of said fins having a plurality of slots formed therein, a plurality of ribs on each of said fins one overlying each of said slots, the ends of each of said ribs being connected to the end walls of the corresponding slot, said ribs extending into said passages, and

- means ridisposed :on: said fins upstream :;of;- said sribssfor :forming substantially szmore turbulence :said :stream :.than. formed ,by, any one ofisaid ribs.

1 I7. -A fintforza'cooling 'nnit. for;positioning:in. a stream in the direction .transverse.to:said axis andsubstantially coextensive with the heat :transfer-membersjn'the direction transverse to the length of said body member.

References Cited in the file of thisi'patent UNITED STATES PATENTS Number Name Date 1,346,535 IFeddenetal 1J uly1-3, 1920 1,416,570 Modine May '16, 1 922 Number Number 8 :Name "Date .Murphy v July 23, .1929 Jaffe June 19, .1934 Schank et -al Dec. '4, .1-934 Emmons Oct. 18, 1938 Merry May 14, 1946 Holihan Apr. '22, 1947 -Spender Jan. 20, 1948 Dailey "June 20, 1950 Chausson Dec. 26, 1950 Simpelaar Mar. 6, 1952 FOREIGN "PATENTS Country vDate France 'June.15, 1936 (Addition to No. 793,344) Denmark Feb.=.22, 1943

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