US1925720A - Fin for heat exchanger - Google Patents

Description

Septg 19393 K. w. HAUPT FIN Fon HEAT-ExcHANGERs me@ nec. 20.1950

Patented Sept. 5, 1933 FIN FOR HEAT EXCHANGER Karl W. Haupt, North Providence, R. I., assignor to General Fire Extingnisher Company,

Providence, n.1., a corporation of Delaware Application December 20, 1930 Serial No. 503,701

1 Claim.

This invention relates to improvements in fins for heat exchangers.

It has been customary to provide iins on the tubes or pipes of heat exchangers for the purpose of increasing the radiating or` absorbing surface presented to the passing medium. It is an object of the present invention to provide a novel shaped fin for this primary purpose which still further increases the effective surface without enlarging the space occupied by the fins. It is also an object to provide fins capable of acting as deflectors whereby the medium flowing past the tubes may be'agitated and given a more tortuous course than results from the tubes and fins heretofore employed. And it is a still further object to so shape these fins that when employed in a cooler or evaporator, they cause rapid and substantially complete discharge of the precipitation which occurs during a defrosting of the apparatus.

These objects and the features which characterize the invention are accomplished by making a fin with a body portion adapted to t snugly about vthe tube, and with outstanding portionswhich diverge with respect to the axis of the body portion. These ns may be placed' in parallelism on the several tubes, in which case adjacent rows of iinsprovide a continuous course whose direction isfrequently altered. By 'staggering the iins of successive tubes, the outstanding portions then cause the medium to be still further diverted and intermixed. This deflecting and mingling of the currents results in all parts of the flowing medium coming in actual contact at one time or another with the surfaces of the tubes or fins and thus assures a greater and more effective transfer of the thermal units.

The best mode in which I have contemplated applying the principles of my inventionis disclosed in the accompanying drawing, but it is intended that the patent shall cover by suitable expression in the appended claim whatever features of patentable novelty exist in the invention disclosed.

In the drawing, Figure 1 is a vertical section through a heat exchanger comprising the novel fins of this invention; Figure 2 is a perspective of the improved n; Figure 3 is an elevation showing one arrangement of the tubes and fins;

Figure 4 is another elevation showing a different arrangement, and

Figure 5 is a plan of a tube and its fins as seen from line 5-5 of Figure 3. l

Referring more particularly t0 the drawing. the heat exchanger '10 is here shown as having top and lbottom headers 12 and 14 connected by a series of tubes 16. The headers and side plates 18 form about the tubes a housing which is open at bothends. In one opening is placed a fan 20 and the other opening is provided with vanes 22 which may be tilted upward or downward as desired to deileet the treated medium after it has passed -by the tubes.

Each tube is provided with a multiplicity of fins 24. Each of the latter has a body portion 24a adapted to fit snugly against Vthe outer surface of its tube. Outstanding around this body -portio'n are two at portions 24h, 24e which are inclined to the vertical with their upper edgesA meeting in a common apex or ridge 24d at the 'top. As here shown, the thickness of the fin plate is somewhat exaggerated for clearness.

In case Where the primary desireis to drive the greatest amount of air past the tubes, the fins are arranged as in IFigures 3 or 4 assuming these gures to be views looking along the axis of the fan. As thus arranged, the fins offer the least resistance to the air and thus enable the maximum amount of air to pass. When, however, the primary purpose is to effect a considerable change in temperature of the passing air, the fins are then placed as seen in Figure 1, or as shown in Figures 3 and 4, now assumingthese figures to be views taken transeverse to the fans axis.

In Figure 3, the corresponding fins on adjacent tubes are all arranged at the same level. The airI currents leaving the fan (assuming it to be at the left of the tubes) strike the sloping surfaces of vthe portions 24e and are deflected upward. This causs some of the air to strike the under surface of the fin portion 24e immediately above, while another part of the air passes over the ridge and into contact with the under surface of the other portion 24h of the same iin. In general, as indicated by the arrows, the currents assume a course between two successive rows of hns, but this 4course is constantly changing as the air meets the deecting portions of the fins in its travel. Obviously additional edding of l the air is caused and as a result of this increased turmoil substantially all of the air comes in direct contact with the n and tube surfaces several times during its movement through the ex'- changer. i

In Figure 4 the flns of one tube are at diiferent levels from the ns on the next tube in the general line of flow. This arrangement accomplishes all the deflecting of the arrangement shown in Figure 3 and in addition causes a further mixing or mingling' of the sub-currents formed by the ns, because as the yair passes from between adjacent flns on the rst line of tubes encountered part of it is deflected upward by the nearest fm on the next row and thence liasses above said nearest fin, while the remainder of the air goes by this said nearest fin and encounters the n below to be thereby deected so as to pass under said nearest iin. Thus there is a repeated separation and distribution of the air in addition to the deection and eddying. Y

It is to be noted. that the ns of this invention require no different spacing of the tubes than if flat horizontal iins were used, it being obvious that the projected space covered by each is identical. And yet because of the inclined portions, here shown as 45 to the vertical,- the surface area of the outstanding portions is approximately forty per cent greater than if these portions were the usual at horizontal ones. This increased area of exposed surface is a distinct gain when the exchanger is used as a heater, for then the number of inclined ns may be the same as though flat ns were employed.

When the exchanger is used as a cooler or evaporator, it is necessary to maintain at least a minimum distance between the inclined portions because of the collection of frost on the tubes and iins. as the passing air gives up its moisture. This requirement makes the number of inclined ns less than the number of flat fins that might be used on the same length of tube, but this loss in number is made up by the increase in area reame@ above noted. Moreover, the inclined ns greatly improve the defrosting of the cooler. This must be done at not infrequent intervals and the simplest way to do it is to cut ot the now of refrigerant to the tubes while the fan continues to run. The relatively warm air thus driven pastA the tubes quickly melts the frost. When the usual at or horizontal ns are used this moisture is quite apt to remain on the upper surface of the fin as a very thin lm which quickly changes to frost against when the refrigerant is once more flowing in the tubes. With the inclined n of the invention, no lm remains on the iins as the slope of the outstanding portions causes all moisture to run down and drip from their bottom edges as fast as it is formed. Accordingly after a defrosting operation with iins of the invention, the latter are left perfectly di'y and because of this the succeeding formation of frost is appreciably delayed. It is also to be noted that placing the ns at an angle to the axis of the tube increases `the extent of actual contact between each fm and the tube. This is advantageousforit aids in thel conduction of heat units from oneto the other and thereby improves the effectiveness of the exchanger.

I claim: l ,l Y

A iin for a tube having atubular body `portion adapted to engage the tube and a pair` of outstanding at body portions which meet and form a ridge perpendicular to the axis of said tubular body and extend downward therefrom in diverging directions, the lower edges of said flat portions being sharp and free whereby moisture collecting on said i'ln may-drop therefrom.

KA RL W. HAUPT.

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