US2321262A - Space heat transfer apparatus - Google Patents

Description

June 8, 1943, w. H. TAYLOR SPACE HEAT TRANSFER APPARATUS Filed Nov.- 1,' -1959 5 Sheets-Sheet 1 2 a N R m IA June'8, 1943. w. H. TAYLOR 2,321,262

SPACE HEAT TRANSFER APPARATUS I Filed Nov. 1, 1939 3 Sheets-Sheet 2 7 HEAT Tzmuswez B.T.U.s.

' III\IVENTOR June 8, 1943. w. H. TAYLOR SPACE HEAT TRANSFER APPARATUS 5 Sheets-Sheet 3 Filed Nov. 1, 1939 f V///////////I W RY m my m A M w V BY m1. Ao afizya.

atented June UNITED. STATES PATENT OFFICE srAcE HEAT TRANSFER APPARATUS William H. Taylor, Waukesha, Wis. Application November 1, 1929, Serial No. 392,315

20 Claims.

This invention relates to improvements in space heat transfer apparatus, and the present application is a continuation in part of my former application, Serial No. 113,327, filed November 30, 1936, under the same title; The present application contains additional disclosures.

The invention may be used either for heating or cooling and is particularly useful for air conditioning purposes, and is peculiarly adapted for use in cold storage rooms.

Broadly, it is one of" the primary objects of the invention to provide a heat transfer apparatus for eificiently transferring heat between a .solid surface and a fluid such as air or gas, or from a confined fluid refrigerant, through a container wall to a moving sheet or stream of fluid, the surface exposed to such fluid being continually scraped or wiped in a manner suitable for the removal of frost and films of adherent or static fluid upon or next to the surface-whereby such films or layers of fluid may be kept in motion and mixed with the major portion of the stream in a manner to substantially equalize the velocity and also the temperature of any given stage of advancement.

I have discovered that the rate of heat transfer between a moving body of elastic fluid such as air or gas and a heated or chilled surface such as a wall (usually a metal wall), is dependent upon various factors, some of which have not heretofore been appreciated.

It has long been known that if the elastic fluid contains moisture which is precipitated or frozen by reason of such heat transfer, the rate of transfer through the wall is impeded and to maintain efficiency it is necessary to provide for frequent removal of accumulations of moisture or frost. But I have discovered that various other factors contribute to a loss of efficiency, including the tendency of the elastic fluid to become stratified.

the central portions maintaining their initial velocity and the side portions maintaining their initial stationary films covering the wall surfaces through which the heat is to be transferred.

These films-or strata cannot be dislodged by increasing the velocity of the air stream but require mechanical displacement and inasmuch as they reconstitute themselves as thermalinsulation blankets in an extraordinarily short space of time, it is necessary to the eflicient operation of the apparatus to wipe the heat transfer surface at minute intervals and by such means as will facilitate a change of air on the surface without inducing eddy currents.

Between these relatively stationary films and Also, in refrigerating apparatus, accumulations of frost have less heat conductivity than the same quantity of frozen material if converted into ice. Therefore it is my object to construct apparatus in which these various factors of reduced efllciency will be minimized or eliminated, and all portions of the elastic fluid may be caused to travel at substantially the same rate for any given cross section of the stream and the stream maintained as nearly as possible at the same temperature for any given cross section.

More specifically stated, the objects common to the use of my apparatus for heating and for cooling include: First, the provision of means for passing the air or gasto be heated or refrigerated over a heat transfer surface with a minimum of eddy currents either on said surface or upon delivery therefrom, and a repeated wiping or scraping of the surface at minute intervals to remove the adherent stratum or film of insulating gas and to dellverofl the gas of said film without permitting it to become reconstituted on the heat transfer surface and without impeding free air circulation over such surface; Secondly, the provision of means for causing the air or gas to be heated or refrigerated by movement radially in a thin sheet over an annular heat transfer surface or between spaced pairs of such surfaces with all portions of the sheet of air at a given radius moving at uniformv velocity, comparatively free of eddy currents, and with constant air change on said surfaces, the air being delivered to the surrounding atmosphere at decreased velocity and with a minimum of eddy current disturbance or friction; and Thirdly, to use for air circulation the same means employed for wiping the heat exchange surface either in contact therewith or in sufficiently close adjustment to continuously displace that portion of the air tending to adhere in a film to such surface, the air circulating and wiping means being numerous and relatively narrow to permit adequate, eddy-free air movement.

Where my apparatus is used for refrigeration my specific objects further include the provision of means whereby the heat transfer surface is not merely traversed by the .wiping blades (which need not be in actual contact with the surfaceto without material dehydration except in cases where air or gas is to be dehydrated by refrigeration, in which event a modification of my apparatus may be utilized to collect 'e precipitated frozen particles and permanent y remove them from the refrigerated air or gas.

Other objects of theinventlon include the provision of specifically designed assemblies of air circulating and scraping means, in one of which the scraper blades will be held centrifugally to the surfaces over which they ride and are so designed that the blades, even when worn, will have minimum tendency to ride upon or over the deposits of frost, but will operate with a scraping action and maximum efiiciency for frost removal.

In another embodiment of my invention, blades which operate with a scraping action are supplemented by blades having cylindrically rounded bearing surfaces or rollers which follow the scraping blades along the annular surfaces from which the frost is to be removed and compress the residual particles of frost into a film of ice having greater heat conductivity than the frost from which the ice is formed.

Other objects of the invention will appear from the accompanying disclosure.

In the drawings:

Figure 1 is a. view in horizontal section on line l-I of Figure 2, illustrating substantially in plan one unit of the embodiment of my invention shown in Figures 1 to 3 inclusive.

Figure 2 is a view taken largely in vertical axial section through a. multiple unit device embodying the invention shown in Figure 1.

Figure 3 is a developed sectional view taken on line 3-3 of Figure 1 and illustrating the relation of the fan blades, scraping blades, and the wiping or compression blades, to each other.

Figure 4' is an end view of a compressing roller and'associated parts used in substitution for the wiping and compressing blades shown in Figure 3.

Figure 5 is aview, partly in elevation and partly in section, on the same plane as Figure 1, showing a modified form of construction of a heat transferring unit.

Figure 6 is an efliciency diagram illustrating the manner in which the rate of heat transfe is affected by varying the number of fan blades employed to drive the elastic fluid through the heat exchanger.

Figure 7 is a sectional view of a modified form of construction drawn generally to line of Figure 8.

Figure 8 is a view taken largely in vertical axial section through a multiple unit device containing the modification illustrated in Figure 7.

Figure 9 is a detail sectional view drawn to the plane indicated by line 8-9 in Figure 8.

Figure 10 is a view similar to Figure 9, illustrating a slight modification.

Figure 11.is a view on a reduced scale showing in perspective a form of the invention used in dehydration.

Figure 12 is a detail sectional view, showing a combination wiping and compressing blade.

,curved convergently in opposite directions to an annular apex 2i. If more than one chamber I5 is employed, these chambers are spaced from each other at a distance substantially equal to the spacing between the respective chambers and the casing walls l6 and II, a series of radially extending passages being thus provided between the chambers i5 and between them and their associated casing walls. Each of these passages has an expanded outlet provided by the oppositely curving walls and the casing walls 18 and IS.

The fluid to be refrigerated enters these passages through central apertures 23 which register with the space encircled by the chamber or chambers I5. This fiuid may be expelled from said central space through the above mentioned passages by revolving fan and wiping blades 25 supported by radial arms 26 from central hubs 21 mounted upon an axially disposed driving shaft 28 connected with any suitable source of power, such as motor 54, Figure '7. The blades 25 are fiat and their transverse dimensions are slightly less than the diameters of the respective passages in which they revolve. The relation of two of these blades 25 to the walls of the middle passage illustrated in Fig. 2 (the opposing walls of the chambers i5) clearly appears in Fig. 3. which also illustrates a form of the scraping blades now to be described.

In each passage one or more scraping blades are interposed between sets of wiping blades. In Figure 3, which illustrates the central passage,

- there are two of these scraping blades 30 and 3| which respectively face in opposite directions and are adapted to scrape frost from the opposing walls or annular side walls of the chambers i5 illustrated in Figure 2. These scraping blades are clamped by bolts 32 between pairs of supporting arms 33, Fig. 1, which project along radial lines from the hub 21. Interposed between the clamping armsand the blades, I preferably employ pads 35 of rubber, fiber or equivalent material, for absorbing blade vibration which would otherwise be transmitted through the arms to the entire unit with objectionable noise or chatter.

The leading side 36 of each scraping blade is preferably made concave and the rear or following side 31 of the blade is made convex and converged to the concave surface, thus giving to the blade a sharp edge.

The compressing blades 38 are similarly formed and supported from the hub 21. As shown in Figure 3, they have rounded bearing surfaces 39 which bear upon the surf-aces of the refrigerating chambers over which they travel and press residual films of accumulating frost into an extremely thin film of ice of less resistance to the transfer of heat than the same mass in the form of frost. If desired, blades 38a, corresponding to the blade 38, may be provided with bearing rollers 40 in substitution for the rounded surfaces 39.

The working edge of each blade extends radially across the associated annular passage wall. which also occupies a radial plane transverse to the shaft axis.

Instead of using scraping blades 30 and compressing blades 38 as shown in Figure 3, I may employ the blade construction illustrated in Figure 12, wherein a plate 30a of abrasive material, such as carborundum, is mounted between two hard rubber plates 34, which are suificiently rigid to prevent the abrasive. plate 30a from breaking. These three plates form a composite blade in which the abrasive grinds away the frost, and the hard rubber plates compress residual frost and convert it into ice. The mounting of these composite blades is similar to that described with reference to the blades 30. each composite blade being clamped between supporting arms 83 by means of a clamping bolt 32 with cushioning pads 35 interposed between the composite blades and the arms to prevent the transmission of vibration and noise, and also allow the blades to yield slightly under pressure which otherwise might break them.

The working edges of the blades need not be in absolute contact with the metal surfaces, although substantial contact exists when the blades are not in motion.

Either the scraping blades 30 or the abrading blade 30a keep the permanent layer of ice at minimum thickness. The scraping blade serves shaft 28 was rotated at 635 R. P. M.

as an abrading element, although its action is more nearly a cutting than a grinding action.

The number of blades is such that their inner ends are quite close together, thus sub-dividing the outwardly moving air into comparatively small sections which can be driven outwardly at high velocity with less turbulence and with less energy than that required for wider passages or for passages with only one or two blades.

The margins of these blades would wear excessively if in contact with the metal surface, but they are kept as'close as possible to the surfaces so that they not only propel the main body of air but constantly displace that portion thereof which tends to stratify in a film on the surface.

In my improved apparatus, in which the air moves substantially parallel to the smooth parallel surfaces or side walls of the passage, frictional resistance is at a minimum and very high air velocities with corresponding high rates of heat transfer result. v

Also due to the fact that the fan blades and the cutter and compression blades extend along radial lines, their divergence in the direction of their outer ends tends to allow each sheet of air to expand with proportionate loss of radial speed, which continues as the air stream passes between the cap members I8 to 2i inclusive, whereby the air stream is delivered into the surrounding atmosphere with little disturbance and encounters minimum resistance. Also the thin sheets or segments of air in the passages have all portions much more nearly at the same temperature than that subsisting in the corresponding passages of any other refrigerating or heat transfer apparatus with which I am familiar.

The diagram appearing in Figure 6 illustrates the increased efliciency resulting from a multiplication of the number of blades. This diagram indicates the rates of heat transfer from steam in chambers I5 to air passing radially through the spaces between them from a source of supply under pressure suflicient in each instance to drive the air through the passage inlets at the uniform It was found that in test 1, with no vane in the passage, the rate of heat transfer was comparatively low, amounting to only about 17 B. t. u.s per square foot per hour per degree F., whereas test 2 with a. single vane 26 in the passage, showed a rate of heat transfer 23% higher, amounting to approximately 21 B. t. u.s. although the-air speed through the apparatus was the same. Test 3 with two vanes in the passage, increased the rate of heat transfer to nearly 22 B. t. u.s. whereas test 4 with five vanes in the passage showed an increase in rate of heat transfer to 25 B. t. u.s, and test 5 with six vanes in the passage showed a rate of heat transfer amounting to approximately 26 B. t. u.s. All other conditions, such as initial temperature of the air, the temperature of the steam in chambars 55, the air velocity, and the shaft rotation, were maintained uniform in the various tests.

The air velocity pattern in the apparatus is somewhat different with six vanes instead of one, but the average velocity over the whole area is substantially the same, yet the rate of heat transfer with six vanes is-22% higher than the rate of heat transfer with a single vane.

My experiments indicate that the stagnant film or layer of air, the removal of which accounts in large part for the efllciency of my apparatus, requires about 6 of a second to reestablish itself, and the number of vanes and speed of rotation should be determined that each part of the heat transfer surface will preferably be traversed by a closely adjusted blade approximately sixty times per second.

Each channel I5 is provided with inlet and outlet pipes 45- and 46 connected by supply and discharge headers 48 and 49, respectively, and the apparatus will ordinarily be supported near the ceiling of the room or compartment to be refrigerated if refrigeration is desired. Figures 7 and 8 show the form of construction disclosed in my said former application and I have illustrated hangers 50 supporting a frame 58 which carries the supply and discharge headers and an operating motor 54. These parts are omitted from Figure 2 as they form no part of the invention herein claimed.

In Figure 8 chambers i5b, corresponding functionally with the chambers [5 in Figure 2, are of a generally triangular form in cross section and are concentric with the armature shaft 28b of the motor. They are provided with inlet pipes 45b and outlet pipes 46b, respectively, connected by headers 48b and 49b. Chambers i5b may be provided with interior radial reenforcing baffles 56 so located as to reduce the'charnber capacity in the vicinity of the outer wall and increase the flow of the refrigerant or other medium at the tapering inner portion of the chamber. Arms 51 extend radially from the hub 21b and support a ring 58 in the space-between the motor shaft and the chambers i512. Each ring 58 serves as a mounting for a combination set of circulating blades 33b, which may also serve as wipers for the side walls of the chambers lib. Each of these blades is shaped approximately like a cotter pin, with its legs divergent at substantially the angle of the walls of the chamber l5b with which they are associated.

The blades may have their eyes packed as closely as possible on the mounting ring between the arms 51, and they embrace the ring sufficiently to be securely retained, although each may be removed by spreading its arms. The arms 33b, or at least those portions in frictional contact with the chambers i5b, are caused by the frictional resistance to bend in a direction opposite the direction'of rotation, whereby the wiping or scraping edges will operate to remove moisture or frost from the walls of the chambers lib with what is ordinarily termed a drawing and scraping movement.

These blades are adapted to serve the double purpose of fan blades and scraping blades, and the centrifugal force developed in the legs of the blades by high speed operation of the rotor will cause the legs to bear firmly upon the oblique hard material applied to the blade by plating,

by metal spraying, or by welding a thin sheet of hard material to the working edge of the blade. This is indicated at 59.

In this form of construction, turbulence in the air stream may be kept at a minimum by making each blade streamlined in form, as indicated at 330 in Figure 10.

Obviously the illustrated construction is merely an exemplification of one of many ways in which centrifugal force may hold the blades to the surfaces.

My apparatus may be used for heating purposes if a heating fluid is supplied to the chambers. If refrigerant is substituted, the fluid in the passages will be chilled.

My apparatus may also be used to accomplish dehydration, in which event I may enclose it in a jacket 60, as indicated in Figure 11. This jacket is provided with a tagential outlet 6| which may lead to an ordinary dust collector or separator 62, having a top air outlet at 63 and a hopper 64 at the bottom for the collection of frost or other separated material. The hopper may have a bottom outlet through which the separated material may pass. When the jacket is employed, the precipitated particles dislodged by the brushes, wipers or scrapers from the walls of the chambers i5 or i511 will not become discharged into the surrounding atmosphere to be again vaporized, but will be collected in the hopper 64. Therefore, the fluid escaping through the top opening will be dehydrated.

The various modifications herein disclosed relate to individual elements which are interchangeable, the general principle of operation remaining the same. In each case I provide smooth surfaced heat transferring walls in radial planes, and arrange the associated walls to form narrow radially extending passages through which the fluid to be conditioned in tempertaure is driven outwardly at high velocity, with minimum turbulence in the passages and minimum disturbance to the surrounding atmosphere, due to the expanding area occupied by the stream and the resultant decrease in velocity. Also, in each instance the heat transferring wall is kept, as nearly as possible, free from accumulations of stratified adherent films of fluid and free from frost or moisture, if the conditions are such as to cause precipitation of moisture from the fluid in the passage. In refrigerating apparatus the driving shaft is preferably employed to actuate scraping, abrading, and compressing means, as well as the wiping and air circulating blades, which largely sub-divide the passage into radial segments.

the arcuate width of which increases along radial lines.

In each case the abrading means may comprise either scraping blades 15 or blades of abrading material, as shown in Figure 12.

In heating apparatus, or in any case when frost is not being precipitated on the heat transferring walls, hard surfaced or sharp-edged scraping or abrading blades may be dispensed with and the wiping blades may be used exclusively for the removal of moisture or films of more or less static fluid from such walls.

Also, in each form of construction provision is made for avoiding eddy currents and countercurrents, while maintaining all portions of each individual air sheet as nearly as possible hemogeneous in temperature at any given radial distance from the passage inlet. Within practical limitations, maintenance of such uniformity in temperature, while avoiding eddies and counter-currents, becomes increasingly possible in proportion to the proximity of the passage walls.

My improved construction not only shows increased efliciency over all other heat transfer apparatus of which I am aware, as measured by the rate of heat transfer per square foot of surface exposed, but also by a marked reduction in the power required to drive a given volume of fluid through the passages I claim:

1. Heat transfer apparatus, comprising the combination of a driving shaft, a set of chambers extending about the shaft and provided with inlet and outlet ducts, annular walls at the ends of said set of chambers and spaced therefrom axially of the shaft, said walls and at least one of said chambers having open central ports of substantial area and defining .radially outwardly opening passages adapted to permit radial flow of fluid outwardly from the vicinity of the driving shaft, fanning and wall wiping means in each passage connected with the driving shaft and extending nearly the full axial distance between said chambers and walls and adapted, when the shaft is rotated, to drive fluid radially through said passages, said passage walls being flat, smooth surfaced and in sufficient proximity to allow the fanning and wiping means to maintain outwardly moving thin sheets of fluid at predetermined velocities and with minimum turbulence, and means for actuating said shaft to impel said fanning and wall wiping means at a rate sufficient to maintain centrifugal delivery of fluid with substantial velocity through said passages.

2.. Heat transfer apparatus, comprising the combination of a closed chamber having heat transfer walls and adapted to receive either a heating or a refrigerating fluid, walls spaced from said chamber walls and adapted to form therewith narrow passages arranged for fluid discharge directly outwardly from between said walls and through which sheets of fluid to be modified in temperature may be projected, said walls and the opposing chamber walls having flat smooth surfaces offering minimum resistance to the passage of such fluid, and means having high speed actuating connections and operative in and substantially spanning said passages to remove frost and other static, adherent or slow moving material from the heat transferring walls and for driving fluid through said passages at high velocity and with minimum turbulence.

3. Heat transfer apparatus comprising the combination with an annular chamber having smooth surfaced radial walls, of associated walls co-operative with said smooth surfaced walls tochamber, and blades carried by said rotor and extending outwardly away from said-axis and operative in said passages to propel fluid therethrough, certain of said blades being in wiping relation to each wall and said blades being sufliciently numerous to be closely spaced peripherally of said chamber about said axis, together with means for operating said rotor and blades rotatably to propel said blades between said walls at a speed such as to develop eflective centrifugal delivery of a fluid through said passages without substantial turbulence.

'4. Heat transfer apparatus, comprising the combination of an annular chamber having smooth surfaced walls in radial planes, associated walls cooperative with said smooth surfaced walls to define annular passages for radial flow of fluid, means for periodically wiping the said surfaces of the radially extending chamber walls comprising blades operative in said passages to drive fluid therethrough, said blades having flat faces in planes perpendicular to the walls of the passage which they occupy and nearly spanning the space between said walls, and the walls being in sufficient proximity to each other to allow the blades to drive fluid through the passages substantially with minimum turbulence, said passage walls being provided with oppositely curving divergent extensions adapted to allow the delivered fluid to expand and enter a surrounding atmosphere with minimum resistance.

5. Heat transfer apparatus comprising the combination of a driving shaft, a chamber extending about the shaft provided with inlet and outlet ducts and provided with fiat side walls in radial planes, walls spaced from the sides of the chamber walls provided with central inlet ports and defining radially extending outwardly opening passages adapted to permit outward flow of air and other fluids in sheet-like currents, fan blades in said passages, having flat working faces normal to the chamber walls, and nearly spanning the space between them, and means adapted to scrape material from said walls into the path of fluid driven through said passage by the fan blades, said fan blades and scraping mean being connected with the shaft to be driven thereby in an annular path between the walls, and means for driving said shaft at substantial velocities, whereby air and entrained material may be driven outwardly by centrifugal force.

6. A device of the character described comprising the combination with an annular heat exchanging surface having means for admitting air centrally thereto, of a rotor co-axial therewith, and wiping means carried by the rotor and co-acting with said surface for maintaining it free from particles of gas or solids tending to rotating the rotor and wipers at a rate such as to traverse a given point on said surface at least approximately sixty timesper second. 4

7. In a device of the character described, the combination with an annular heat exchanger having its opposite faces converging centrally toward a median plane, of a rotor within said heat exchanger, and wiping means connected with said rotor adjacent said plane-and diverging in wiping contact with the faces of saidheat exchanger.

8. In a device of the character described. the combination with an annular heat exchanger having an internal cavity and external surfaces mutually convergent toward a common apex,

a rotor having a portion revoluble near said apex,

a series of wiping means each having a head connected with said portion of said rotor and having divergent legs engaged with the respective surfaces and arranged for wiping contact thereover during the operation of said rotor. g

9. In a device of the character described, the combination with an annular heat exchanger having an internal cavity and external surfaces mutually convergent toward a common apex, a rotor having a portion revoluble near said apex, a series of wipers, each having a head connected with said portion of said rotor and having divergent legs engaged with the respective surfaces and arranged for wiping contact thereover during the operation of said rotor, said rotor being disposed within said heat exchanger and said apex being centrally directed.

10. In a device of the character described, the combination with an annular heat exchanger member having an interior cavity and having external heat exchanging surfaces mutually convergent toward a common apex, of a rotor comprising a ring mounted co-axially with said heat exchanger and substantially in the plane of said apex, ;and a series of wiping blades having eye portions threaded upon said ring and having yieldable leg portions in wiping engagement with I said surfaces.

11.},In a device of the character described, the

. combination with an annular heat exchanger member having an interior cavity and having exadhere thereto, at least a portion of the periphery of said surface being fully exposed for free radial discharge of air whereby said wiping means is adapted to induce a centrifugal flow of air across the surface wiped, said wiping means constituting an annular series of wipers at slight angular spacing from each other, and means for ternal heat exchanging surfaces mutually convergent toward a common apex, of a rotor comprising a ring mounted co-axially with said heat exchanger and substantially in the plane of said apex,fiand aseries of wiping blades having eye portions threaded upon said ring and having yieldable leg portions in wiping engagement with said surfaces, said heat exchanger being outside of said ring and said surfaces being in the path of centrifugally induced movement of said wiping blades, whereby centrifugal force will maintain said blades in intimate contact with said surfaces.

12. In a device of the character described, the combination with an annular hollow heat exchanging body having opposed converging surfaces, of a bifurcated blade having its legs divergent for engagement with the respective surfaces, and means for rotating said blade upon the axis of said body.

13. A method of dehydration which consistsof refrigerating surface, scraping said surface at short intervals to free it of condensate, circulating' gas over said surface, discharging the condensate from said surface with the circulating gas. and subjecting the gas and the gas borne condensate to inertia forces f r separating the condensate from the gas while p eumatically carried thereby.

14. A method of dehydration which consists in repeatedly scraping a chilled surface and concurrently delivering a current of gas oversaid surface, discharging said gas and the liquid and solid matter scraped concurrently from said surface for the pneumatic delivery of such matter, and the separation of the liquid and solid matter from the gas while such matter is pneumatically carried by the gas.

15. An apparatus of the character described comprising a heat exchange surface having means for the admission of a gaseous fluid to said surface and for the discharge of fluid therefrom, means for refrigerating said surface to the point of tending to induce frost to form thereon and means movable over said surface for the circulation of fluid thereover and for wiping frost from said surface as well as a stratum or fllm of fluid adherent thereto, said means comprising blades and means for actuating said blades over said surface at sufficiently frequent intervals to substantially prevent accumulations of frost and relatively static gaseous fluid material.

16. An apparatus of the: class described, comprising a heat exchange surface having means for the admission of a gaseous fluid to said surface and for the free peripheral discharge of fluid therefrom in substantially all directions, in combination with means movable over said surface in an endless path for the circulation of fluid outwardly thereover and the free discharge f such fluid in substantially all directions and for wiping from said surface a stratum film of relatively fixed gaseous fluid, said means comprising blades in wiping relation to said surface and means for actuating them in a succession of wiping operations having a frequency of approximately sixty of such operations per second.

17. Heat transfer apparatus, comprising the combination of a driving shaft, a chamber about the shaft provided with inlet and outlet ducts, at least one annular wall spaced axially of the shaft from the radially extending side of the chamber and provided with a central aperture of substantial area and defining a radially outwardly opening passage adapted to permit radial flow or fluid outwardly from the vicinity of the driving shaft, and fanning and wall wiping means in such passage connected with the driving shaft and nearly equal in axial extent to the space between the chamber and said wall and adapted, ,when the shaft is rotated, to drive fluid radially through said passage without substantial turbulence, and means for operating said fanning means at a speed such as to develop effective centrifugal delivery of fluid through said passage.

18. A method of heat exchange which comprises passing a dry gaseous fluid over a heat exchange surface radially in all directions from a central point and concurrently positively wiping from said surface with at least a frequency approximating sixty times per second dry gaseous constituent portions of said fluid tending to form a superficial film at said surface.

19. A method of heat exchange which comprises passing a gas current in a thin sheet over a heat exchange surface, developing on such surface a temperature sufliciently low to, induce frost formation thereon and in motion with said current positively wiping said surface to displace from each portion of said surface, with at least a frequency approximating sixty times per second, both frost and gaseous matter tending to accumulate on said surface.

20. A method of heat exchange which com tion of said surface, with at least a frequency approximating sixty times per second, matter tending to accumulate on said surface, and discharging such matter with said current.

WILLIAM H. TAYLOR.

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