US2201688A - Method of and apparatus for conditioning air - Google Patents

Description

I May ZL EMQD w. R. ZUHLKE METHOD OF AND APPARATUS FOR CONDITIONING AIR Filad Oct. 24, 1936 s Sheets-Sheet 1 cno 4 VENTOR W. R. ZUHLKE mam-1o 0? mm APPARATUS FOR coumuowme AIR Filed Oct. 24, 1936 s Shets-Sheet 2 ZQOLg w. R. ZUHLKE METHOD OF AND APPARATUS FOR CONDITIONING AIR Filed Oct. 24, 1936 6 Shaets-Sheet 3 R O T N E V m May 2i, i%@. w. R. ZUHLKE METHOD OF AND APPARATUS FOR CONDITIONING AIR Filed Oct 24, 1936 6 Sheets- Sheet 5 I I I I l l INVENTOR May 21, 1940."

w. R. ZUHLKE METHOD OF AND APPARATUS FOR CONDITIONING AIR Filed Oct. 24, 1936 6 Sheets-Sheet 5 I INVENTOR Patented May 21, 1940' METHOD or AND arrana'rus FOB CONDITIONING Am William B. Zuhlke, Yonkers, N. 1., assignor, by mesne assignments, to American Radiator & Standard Sanitary Corporation, New York,

N. Y., a corporation of Delaware Application October 24, 1936, Serial No. 107,376

12 Claims." (01. 183-4) The general object of my invention is to provide an improved method of and apparatus for 55 periods suitably short in which the supply of fresh conditioning air, and particularly air for ventilating rooms or spaces used for human occupancy.

My invention is characterized by, and comprises, an improved method of, and apparatus for reducing the moisture content of, or dehumidifying air, and in some cases, its dehumidification is the only significant change in the condition of the air effected by the use ofmy invention. However, my method of dehumidiflcation involves an initial heating and subsequent cooling of the air, and the air cooling operation may advantageously be carried out in some cases, so asto make the delivery temperature of the conditioned air less than the initial temperature of the air conditioned.

In conditioning air in accordance with the present invention, I eliminate moisture from theair by bringing itinto contact with some material such as silica-gel or calcium chloride which in a dried, or activated, condition is adapted to absorb a large amount of moisture from air brought into contact with the material, and which after having its moisture absorbing capacity reduced by absorbed moisture which it holds, can have that capacity restored or 'increased, by a reactivation or'regeneration treatment, which I efiect by bringing into contact with thematerial, hot air admixed with products of combustion of fuel burned to heat the air. The words absorb and absorption, as herein are intended to generically include the action specifically designated by the words adsorb and adsorption.

Heretofore various proposals have been made for the use of absorbing material of the character above mentioned, to dehumidify air and for the regeneration or reactivation of the material, from time to time, by bringing hot gases into contact with the material. \A

My invention is characterized, however, by novelty in the means for and method of carrying out and relating the dehumidiflcation and regeneration steps or stages, by which the moisture absorbing material is alternately used as a dehumidifying agent and is subjected to a regeneration or reactivation action.

My invention takes into account and makes use of the fact that room atmosphere conditions suitablefor the comfort. and health of the room occupants may be maintained by the intermittent supply of an adequate supply of fresh air to the room, and that if the periods during which air is supplied are suitably long, and alternate with air is interrupted, the'general ventilation and conditioning effect will be practically equivalent to that obtainable by the continuous supply of substantially the same amount of fresh air to the room. While the precise duration of the succes-' 5 sive dehumidifying and regenerating stages of the cyclic operation which I provide, may vary with conditions, I note, by way of example, that a preferred formof apparatus for the practice 01' my invention, hereinafter described in detail, was designed, and is adapted, for successive operation cycles, each comprising a 40 minute dehumidiil-- cation stage or period, and a regeneration stage or period of from 13 to minutes, depending on the amount of moisture absorbed during the 15 previous dehumidification period.

My invention, in its preferred form, is also characterized by novel means and steps provided to permit or facilitate .the regeneration "of the moisture absorbing material, ina period approxi- U mately only one-third to one-half as long as the immediately preceding 40 minute dehumidification period.

In the preferred form of my invention I continuously move air, drawn directly from the atmosphere or other source of air to be conditioned, into contact with the moisture absorbing material by which the air is dehumidifled. During the dehumidification stage or period of each cycle, the air after passing out of contact with the moisture absorbing material, is subjected to a cooling action to suitably lower the temperature of the air, which is raised while in contact with said material, by the addition to the air of sensible heat corresponding in amount to the latent heat 5 of evaporation of the moisture absorbed from the air by the material. During each regeneration, or reactivation, period orstage, the air is subjected to a heating action, suitably diminishing the relative humidity of the air, prior to the 40 passage of the air into contact with the absorbing material then regenerated or reactivated, and the air then passing out of the contact with the absorbing material, and carrying with it the moisture which it drives out of that material, is 46 diverted from the air cooling means used in the dehumidification stage and from the room or rooms ventilated, and is ordinarily discharged to waste. I v

The capacity for the regeneration of the mate- 0 rial in approximately one-third to one-half of the time in which the-material is used in dehumidifying ventilation air, is made practically possible in accordance with the present invention, by the use of simple and eiiective means for heating the regeneration air approximately to the maximum temperature to which the absorbing material can be safely and economically subjected, and by disposing the moisture absorbing material relative to the path of air flow, so that in each dehumidification stage, the air passes in series through different portions of the material, while during each regeneration stage, different portions of the regenerating air passes in parallel through the said different portions of the material.

For the practice of my invention I have devised a novel air conditioning apparatus unit of such character that it may be located in the cellar or furnace room of an ordinary dwelling house of moderate size, and used in conditioning the air for ventilating some or all of the various rooms of the house. Said unit is adapted, however, for use with no significant change, except in its dimensions, to provide conditioned air in larger amounts as required, for example, in the ventilation of office buildings, and of restaurants, theatres, and other large assembly rooms.

The improved unit in its preferred form is especially adapted for domestic use and without requiring skilled attendance, by the mechanically simple and reliable character of the provisions for carrying out, and for automatically repeating the dehumidification and regeneration actions at regular intervals.

The air cooling action to which the dehumidified air is subjected, may be efiected by mechanical refrigeration means, by the use of cooling water drawn from city water supply mains or other available source of cooling water, and by other means, and the character of the cooling means desirably employed in difierent installations, will ordinarily depend on cost and convenience considerations which will vary in different installations. Wherever it is especially desirable, or the cost of the additional cooling required is not economically objectionable, the cooling action may be carried out so as to make the delivery temperature of the conditioned air appreciably lower than the temperature of air supplied for conditioning. For ordinary ventilation purposes, in localities and under conditions in which I anticipate that the greatest practical use of the invention will be made, practically effective and satisfactory air conditioned results are obtainable Without any significant reduction in the temperature of the conditioned air below the prevailing atmospheric temperature, since, for example, air at a temperature as high as 85 or 90 F., in ordinary rooms, does not seriously inconvenience or give discomfort to the occupants of the room, provided the humidity of the air is suitably low. For such installations, and particularly where it is not convenient or too expensive to cool the air by other means, I advantageously cool the air by an evaporative action, and the air cooler in a desirable form of my unit illustrated herein, includes a heat exchanger comprising passages for the air to be cooled, which are in good heat transfer relation with passages through which I pass atmospheric air after spraying water into that air.

With such evaporative cooling, itis practically possible to reduce the temperature of the conditioned air appreciably below the atmospheric dry bulb temperature.

In addition to the general features mentioned above, my improved apparatus in preferred forms, comprises various novel features of construction and arrangement. While the various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this specification, for a better understanding of the invention and its advantages, reference may be had to the accompanying drawings and descriptive matter in which I have illustrated and described a preferred embodiment of my invention.

Of the drawings, Fig. l is a sectional elevation of a conditioning unit constituting one embodimerit of the invention, the section being taken on the broken line ii of Fig. 5;

Fig. 2 is a perspective view of the unit shown in Fig. 1;

Fig. 3 is a section of an air cooler portion of the unit shown in Figs. 1 and 2, the right hand portion of the section being taken on. the line 3a ila, and the left hand portion on the line Fig. i is a section on the broken line i-t of Fig. 3;

Fig. 5 is a plan section on the line it'si of Fig. 6 is a plan section on the line 6-6 of Fig.

Fig. '7 is an elevation in section on the line ll-l of Fig. 1;

Fig. 8 is an elevation in section on the broken line 8i3 of Fig. 6; and

Fig. 9 is a diagrammatic representation of automatic control means.

The air conditioning unit shown in Figs. 1 to 7, comprises an insulated housing or casing i, provided at its top-with an inlet 2 for air to be conditioned, a conditioned air outlet 3, and a waste outlet t, through which moisture laden air mixed with products of combustion is discharged during the regeneration stage of the operating cycle, and through which warm humid air, used in cooling the conditioned air, is discharged during the dehumidification stage of operation.

The inlet 2 for air to be conditioned, opens into a plenum space or chamber 5, within the housing I, from which, during the air conditioning stage of the operating cycle, the air to be conditioned is moved by a blower or fan 6 through a duct 1 into a chamber 8. The latter encloses air heating apparatus, collectively designated 9, and

V hereinafter described in detail, which, is used in the regeneration stage, but is inoperative during the air conditioning stage of the operating cycle. The chamber 6 is shown as above and opening through a bottom outlet part It) into, a chamber H. The latter is surrounded by a pervious wall including moisture absorbing material H. The air passes from the chamber I I through said pervious wall into a surrounding space l3, enclosed by a casing or shell H.

The pervious wall, space l3 and shell H are extended downwardly so that their lower portions surround a chamber I5 directly beneath the space H and separated from the latter by a partition l6 formed with a large central port, which is closed by a damper or valve I1 during the air conditioning stage. The air received in the space l3 from the chamber H during the air conditioned stage, passes againthrough the pervious well including the water absorbing material [2, into the chamber 15. The latter is provided at its bottom with an outlet port I8 which is open during the air conditioning stage, but is closed by a damper or valve l9, during the regeneration stage. The port I8 opens into one end of a conmouse clan air cooler 22, through which the air passes I upward to the conditioned air outlet 3.

As hereinafter explained in detail, the air cooler- 22 is a channelled'structure including passages 24, separate from the conditioned air passages 23, for the flow of the cooling agent. That agent in the unit form shown in Figs. 1 to 7, is air drawn from the plenum chamber 5 through an inlet 25, into an air humidifying chamber 26 having an upper portion extending through an opening in the top wall of the housing, and into which water is sprayed by nomles 21. The chamber 26 has anoutlet 28 communicating with the upper ends of the cooling agent passages 24 of the air cooler 22, at the top of the latter. The

last mentioned passages communicate at the bottom of the air cooler with a duct connected by a conduit 30 to the inlet of a fan or blower 3I, employed to move air from the chamber 5 through the cooling fluid passages 24 of the air cooler 22, and which delivers that air through a discharge'conduit 32 opening into a'waste conduit-or chamber 33 beneath, and opening directly' to, the waste outlet 4. -The chamber or conduit portion 33 is provided at its bottom with a port 34 which is closed during the air conditioning stage of. the cycle by a valve or damper i During the air conditioning stage of the cycle of operation of the unit, air to be conditioned flows continuously from the inlet 2, through the chamber 5, fan or blower 6, duct I, chamber 8, chamber-II, chamber I3, chamber I5, port I8,

- duct 20, and the conditioned air passages 23 of air cooler 22, to the conditioned air outlet 3.

As the air passes from the chamber II into the chamber is, some of its moisture is absorbed as it passes through the upper portion of the bed of absorbing material I2 then traversed, and as the air passes from the chamber I3 into the chamber I5, the lower portion of the bed of material I2, then traversed, absorbs the remainder of the moisture eliminated from the conditioned air in the unit.

With the chambers II and I5 symmetrically disposed and similar in their dimensions as shown, some 65 or 70% of the total amount of moisture eliminated ifrom the conditioned air, is eliminated as the air passes from the chamber II into the space I3, and the remaining 35-30% of I the moisture eliminated, is eliminated from the air as it passes from the chamber I5.

For the general purposes of the present invention, the bed material I2 employed,-may be any available material having suitable moisture absorption and regenerative capacity." Various known substances other than silica-gel and sub chamber I3 into the stances consisting of, or including calcium chlo- I humidification procedure described, the material I2 will continuously absorb about 70% of the moisture in the air passed into the chamber I i throughout e'a ch dehumidification period of about 40 minutes.

As already indicated, the moisture absorbing action of the material I2 is adiabatic, and the passage oi the air dehumidiiied through the material I2. increases the temperature of the air in correspondence with the. latent heat of evaporation of the moisture absorbed. substantially all of such latent heat being transferred to the air.

With the type of evaporative air cooler 22 employed, it is possible to cool the conditioned airdown in its passage through the air cooler .to within 5 or so of the wet bulb temperature of the air supplied through the inlet 2 to the inlet chamberl. Thus, with the above assumption of an inlet air temperature of 85 and relative humidity oi 70%, it is practical to cool the conditioned air delivered. through, the outlet 2, to a temperature of about 82 F.

For regeneration stage operation, the dampers or valves I1 and 35 are opened, the damper I8 is closed, and the air heating apparatus a is set 1 into .operation to heat and dry air. which is moved by the blower 6 from the chamber 5 through the conduit 1, and chamber 8 and'port I0 into the upper end of the chamber I I as in the dehumidification stage. Since the chambers II and ii are" then in free communication, some of the air entering the chamber II will pass downward through the latter into thechamber'ili. The air passing into chamber II and not entering chamber I5, and the air which does enter the chamber I 5, pass in parallel through the respective upper and lower portions of the pervious material 'I2 into the space or chamber I3, which opens y at its upper end into a-conduit or chamber 38 extending beneath the previouslyrmentioned waste conduit or chamber 33, with which the chamber 36 is in direct communication when the valve or damper 35 is open. As will be apparent with the chambers II and I 5 similar to'one another in their dimensions, appreciably less thanQone half of the air entering the chamberv II will pass from the latter into the chamber I5. This is desirable with the described arrangement, in which as already noted-approximately 65 or 70% of the moisture eliminated from the air in the conditioning stage is absorbed by the upper portion of the material I2 surrounding the chamber i I, so that the material I2 surrounding the chamber I I, needs to be subjected to a much greater regeneration efiectthan does the lower portion of the material I2 surrounding the chamber I5. With the apparatus proportioned as illustrated, no throttling by valve II of the port which it controls, is

necessary to so proportion the relative amounts of air passing through the portions of material I2, respectively surrounding the chambers Ii and I5, as

to subject those portions to appropriate regenera tion effects.

While the parts of the unit shown in Figs. 1-7 already mentioned, comprise all that are essential tothe operation of the unit in the general manner described, said unit comprises automatic control mechanism andnumerous special features of construction and arrangement, not previously men-.-

tioned but hereinafter described, which are novel,.

and contribute to the practical merit and'utility of the unit. I

Theunit casing I, as shown, and conveniently,

is in the form of a box formed of 'metal plate's'ections welded together, and open at its bottom,

with the lower edges 01" its vertical walls adapted to rest on the floor of the cellar furnace room, or

other room of the building in which the unit is located. It may be lined with any suitable heat insulating material 39. Conveniently, the casing is rounded at one end to conform with the circular outline of the shell I4. The casing may be formed with openings for conduit connections and for access to the mechanism within the casing, and be provided with suitable covers for the latter, as conditions require or make convenient.

The apparatus within the casing is supported on a base member 40in the form of a hollow box formed by metal plates welded together, and forming the walls of the previously mentioned conduit 20. The top wall of the base member is formed with a circular opening at the end of the base member which is rounded to conform with the rounded end of the casing In this opening is secured a. ring frame 4| member of angle bar cross section, supporting the shell l4 and the portion of the apparatus within, and associated with that shell.

At its said rounded end, the base member includes an end part 42, which is removable to permit access to the valve l9 and associated valve mechanism parts. At its opposite end, the top wall of the base member is cut away to provide the previously mentioned port 2| through which the conduit 20 opens to the air cooler 22. To provide additional support for the latter, the end wall of the base member proper is reinforced by an external channel bar 43. Associated with the base member 40 are floor engaging leveling screws 44 serving as legs by which the bottom of the base member is held slightly above the floor level.

Associated with the base member 40, is an uprising frame structure 45 which includes a horizontal air cooler supporting channel bar 45a, a motor supporting platform 45b, and a channel bar 450, forming a part of an enclosure for control mechanism terminals, hereinafter described. The uprising frame structure 45 also includes frame parts, other than those mentioned, which do not need to be described, or further referred to herein, as their specific form and arrangement constitutes no part of the present invention, and they may be varied as conditions make desirable.

Anelectric motor 46 mounted on the platform 45b is employed to drive through a belt 41, a common shaft 48, suitably journaled in the framework of the apparatus, and carrying the impellers of the two previously mentioned fans or blowers, and 3|. The latter may be of any known and suitable type and form, and as shown are Sirocco blowers.

The pervious wall or bed including the material l2, comprises inner and outer spaced apart screen sections of perforated sheet metal. As shown there are two end to end inner sections 55 and 5|, between which a marginal portion of the previously mentioned partition I6 extends to thereby support the upper section 50, and a single outer section 52. Each of the sections 50, 5|, 52 is formed with deep groove and rib forming 'corrugations parallel to the common axis of the chambers Hi and I5. The internal corrugation grooves and ribs of the outer section 52 nest with the corresponding external ribs and grooves of the inner sections, to provide a space for the material |2 which is of substantially uniform thickness and extends in zig-zag fashion about an inch in diameter, per square inch of screen surface.

The sections 50, 5|, and 52 may advantageously be formed of very thin sheet metal, and because of their thinness and deep corrugations, reinforcing bands 53 are advantageously welded or riveted to the innersides of the inner sections, one adjacent each end of each of the latter, each band 53 being riveted to the crests of the internally extending corrugation ribs of the corresponding screen section. Similar bands 54 are welded or riveted to the crests of the outwardly extending corrugation ribs of the outer section 52, adjacent each end of that section. The bands 53 and 54 assist in preserving the proper relative disposition of the different corrugations of the sections, particularly in assembling the apparatus.

Thelower edges of the lower inner section 5| and the outer section 52 rest on an annular bed plate 55, which, in turn, rests upon and is supported by the annular base member part 4|. The previously mentioned port I8 is in the form of a central opening in the bed plate 55. The top end of the upper section 50 is shown as spaced from the outer section 52 by clips 55.

The previously mentioned inlet port III to the chamber is formed in a platelike part 51 which rests on the upper ends of the screen sections 50 and 52, and is provided at its periphery with 9. depending skirt or cylindrical extension part 58. The latter forms the upper portion of the previously mentioned shell I4, or outer wall for the space I3. The shell I 4 comprises a cylindrical body portion in telescoping relation at its upper end with the skirt or cylindrical part 58, and at its lower end with a cylindrical part 59 which rests upon the bed plate 55. In the assembled apparatus, the upper end portion 58 of the wall or shell I4 is anchored to the bed plate 55 by tiebolts 60, which advantageously include bends to permit of sufllclent elongation and contraction in length of the tie-rods to accommodate the elongation and contraction of the screen sections, 55,

' 5|, and 52, as the latter heat up in the regeneration stage, and cool down in the dehumidiflcation stage, of each cycle. As shown, the tie-rods 80 pass at their lower ends through apertures formed in the bed plate 55 and have their upper ends passing through lug or ear parts 6| welded on the top member or skirt part 58.

The air heating apparatus 9 in the chamber 5 as shown is directly supported by the plate part 51 and comprises parts novel in their construction and arrangement, peculiarly adapting the heating apparatus to its intended use. Said parts include a multiplicity of similar vertically disposed burner elements 10, arranged in a circular series about the common axis of the port l0 and chambers H and I5. Each element 10 includes a chamber 1| receiving fuel gas mixed with primary air, through a passage 12 axially disposed in a nipple extension 13 of the element at its top. inner wall of each chamber 1| is formed a multiplicity of burner orifices 14 directed toward the center of the cylindrical space surrounded by the series of elements 10. The elements 10 comprise portions extending outwardly beyond the corresponding chambers II and curved so that each element forms a vane cooperating with each adjacent element to form a curved nozzle or air inlet passage 15 between each pair of elements 10, which leads horizontally inward from the space at the outer sides of the elements 10, into the cylindrical space surrounded by those elements.

The vertical wall 16 of the chamber 8, as is clearly shown in Fig. 5, is shaped to give the portion of the chamber'8 between it and the element 10, the form of a scroll or spiral space, di-

In the 'minishing in cross section as the angular distance about the axis of the chambers II and I5, from the intersection ofv the conduit 1 with the chamber 8 increases. The curvature of the passages 15 is such that the outer ends 'of those passages approach a tangential relation with cylindrical inner side of said scroll space, and I face the direction of flow from the conduit 1 through said scroll space. In consequence, as

those skilled in the art will understand, the air entering the scroll space from the conduit I,

- nipple extensions 13 at the tops of the burner elements are externally tapered, and are snugly received in tapered apertures in a superposed manifold element. The latter, as shown, comprises four quadrantal are shaped hollow bodies a 18, bolted together at their ends to form a rigid annular element. receives fuel gas mixed with primary air for combustion, through a Venturi tube shaped tubular member 19, providing a mixing passage similar in form and effect to the characteristic mixing passage of an ordinary Bunsen burner. Each member I9 receives fuel gas through a nozzle part 88 extending axially into the inner end of the member and forming the delivery end of a corresponding pipe branch 8| from a primary gas supply manifold 82 of cruciform shape, including one arm for and supplying gas to each of the mixing members 18. The primary manifold 82 receives gas through a supply pipe 83 including a control valve 84 automatically actuated as hereinafter described. Primary air is aspirated into the inlet end of each mixing member 18, through air inlet ports 85 in apertured diaphragm plates 86 surrounding the corresponding gas nozzle 88,

and adapted for adiustment in a manner com-' monly employed in Bunsen burner mixers. The burner elements 18 have hollow vane tip portions and their light weight, coupled with their relatively large heat dissipating surfaces, permits of a suitably large heating capacity with such small heat storage capacity that their significant air heating eifect ceases almost immediately when their fuel gas supply is interrupted.

The gas supply control valve 84 and the gas burning parts above the burner element 18, are

located in anuprising extension from the chamber 8, which is surrounded by a cylindrical casing element 81. Thelatter extends upwardly through the top wall of the housing I, and is closed at its upper end by a cover 88, removable to permit access to the air heating apparatus. The cover 88 isv formed with a vent opening, normally closed by a light weight disk valve 98, which is moved upward into vent'closing position by the pressure of the air in the chamber 8, when that chamber is receiving air from the fan v6 during the dehumidiflcation and regeneration stages in normal operation. When the operation of the fan 8. is interrupted, as it may be during certain hours of the day, or other periods in which operation of the apparatus is temporarily un- Each manifold quadrant I8- necessary, the disk valve 98 drops and opens the vent 88. The latter is provided primarily to permit the escape of products of combustion produced by a pilot burner 9|, when the latter is left in operation during periods in which the operation of the blower 6 is temporarily interrupted. The purpose of the pilot burner is to ignite the gas and primary airmixture discharged through the burner element ports 14, when the gas supply valve 84 is opened at the beginning of each regeneration stage. The pilot burner receives gas through a supply pipe 92, separate from the pipe 83 and not controlled by the main gas supply valve 84.

The air cooler 22, as shown, is formed by vertically disposed plates I88 and I8I, which as assembled are right and left hand counterparts of each other, and which alternate in the assembled group of plates which are held in contact with one another.

The plates I88 and I8I asshown, are actually identical in form but are reversely arranged. Each plate I88 is formed at one side with a series of vertical ribs I82 and which may be regarded as forming the sides of corresponding vertical grooves, the width ofeach of which is appreciably greater than the width of each rib I82. The ribs I82 of each plate I88 extend centrally intothe said grooves of the immediately adjacent counterpart plate I8I, and the ribs I 82 of the last mentioned plate extending centrally into the grooves between the ribs I82 oi the first mentioned plate, as is clearly shown in Figs. 3 and 4. The opposing grooves of each plate I 88 and its counterpart plate I8! at the right, as seen in Figs. 3 and 4 collectively form one of the cooler channels 23 for the dehumidified air; Each such channel, zig zag in horizontal cross section as clearly shown in Fig. 4, extends for nearly the full width of the cooler in the direction'of the plates I88 and I8I. As previously stated, each channel 23 opens at its lower or in-' let end to the outlet part 2! of the conduit 28 and. opens at its upper end to the conditioned air outlet part 3 of the casing I. a

At the sides of the plates I88 and IN opposite to those carrying the ribs I82, each plate is formed with a groove extending for nearly the full width of the plate. Said groove in each plate I88 and the opposing groove in the plate IIJI to the left, as seen in Figs. 3 and 4, collectively form one of the previously mentioned cooling agent channels 24. Each of the said grooves thus forming a part of a channel 24 has an upper end portion I88 closed at its upper side and extending horizontally to the right hand edge of the corresponding plate as seen in Fig. 1, and increasing in depth as it approaches that edge. The opposing groove portions I83 thus unite to form an enlarged inlet portion for the corresponding channel 24 which opens directly to the outlet 28 of the spray chamber 28. At the bottom of the cooler, the opposing grooves forming each channel 24 are laterally extended to provide a horizontal outlet portion I88 at its opposite edges and intermediate their.

ends, and one tenon of each plate is snugly -received in the previously mentioned channel bar framework portion 45a. In practice, provisions, which may be of any suitable or known character and .hence need not be described in detail, 7

are provided to seal the joints between the plates I and IOI, adjacent the edges of the cooler. As will be apparent also, suitable provisions are needed to prevent leakage between the plenum space within the casing and the joints between the cooler and the conduit and outlet 3. As will be apparent also, suitable provisions should be made for sealing the joint between the lower portion of the casing or shell It and the conduit 20, since in operation, the air pressure in the flow paths, through which air is passed by the fan 6,

to the dehumidifled air outlet 3 and the waste outlet 0, is above the pressure of the atmosphere prevailing in the space 5. In the portion of the cooling agent flow path, at the inlet side of the port 3i, the pressure will be lower than the pressure of the atmosphere and suitable provisions are necessary to prevent any leakage of air from the space 5 into that flow path portion. The leakage preventing provisions need not be further described or further referred to however, as those skilled in the art will understand how to provide suitable provisions for the purpose.

The nozzles 2? in the spray chamber 26 discharge jets of water downward against a deflecting target member IIEl located in the spray box 26 adjacent the inlet thereto. The target member breaks up or atomizes the water in l the jets impinging against it and the water thus broken up, is deflected by the target away from the latter in the form of a mist moving in the general direction of the air stream passing through the spray box inlet 25 to its outlet 28 and into which stream, the water mist is dispersed. In the unit illustrated, a drain pipe 00. is provided for the discharge of unevaporated spray water carried into and collecting on the floor of the conduit 29.

As shown, the valve or damper members ll and it are connected L0 a common vertical operating spindle H5, which is engaged at its lower end by a lever pivoted at III in a bracket carried by a beam or bar M8. The latter extends chord-like across a portion of the member M at oneside of the port I8, and may be welded at its ends to the depending vertical flange portion of the member 4I. The end of the lever I I6 remote from the valve spindle H6, is connected to the lower end of a vertically movable spindle or rod I20, which is connected at its upper end to, and carries and operates the damper 35. When the rod I20 occupies its upper position, shown in Fig. l, the valve member I'I closes the port in the partition I6, the valve member I9 opens the port I8, and the valve member 35 closes the port between the waste conduit or chamber 33 and the conduit or chamber 35, which communicates with the space I3. When the valve spindle I20 is lowered from its position shown in Fig. 1, the valves 35 and I1 are moved to their open positions and the valve I9 is moved to its closed position.

The valve rod I20 is periodically moved between its upper and lower position by means of a crank arm I2I angularly adjusted by a periodically operating electric damper motor'I22. As shown, the crank arm I2I is connected to the rod I20 at points respectively above and below the crank arm "by means of upper and lower springs I23 and I24 respectively. The lower spring I24 is put under tension'to insure snug engagement of the valve members I1 and 35 with their respective seats, when those valves are moved into their closed positions, and the upper ductor spring I23 is put under tension to insure snug engagement with its seat of the valve member I9 in the event of one or more contingencies making the continued operation of the apparatus unsafe or undersirable. In Fig. 9, I and I3I represent electric current supply conductors, supplying energy for the operation of the previously mentioned fan and damper operating motors iii and IE2, and for energizing control elements as hereinafter described, through terminals carried by a terminal board I32. The latter is conveniently located in a space I33, the enclosing wall of which is formed in part by the previously mentioned channel bar frame part 450.

A main terminal I3Ila of the terminal board M32, is directly connected to the supply con- I30. The cooperating main terminal lSIa is connected to the conductor I3I by a branch conductor I30 and switch element I35, only when the latter is held in its closed position, by the energization of .a coil I36. Conveniently, and as shown, the coil I36 is energized by the low voltage current in the secondary circuit I31 of a step down transformer I3'Ia, having its primary winding connected across the supply conductors I30 and I3I. The secondary circuit It? may be closed to energize the coil I36, by the adjustment into its closed position of either of two movable switch elements I30 and I39. The switch element I38 may be a so called owner's switch, manually adjustable by the attendant in charge of the operation of the apparatus, or it may be a humidostat, automatically moving the switch member I38 into and out of its closed position, as the humidity in some room supplied with conditioned air by the apparatus rises to, or falls below a predetermined value.

The switch element I30 is automatically actu ated by an electric clock I40, which, as hereinafter explained, is operative to directly determine the duration of each dehumidiflcation stage. As diagrammatically shown, the switch element I39 is an arm carried by a shaft rotated by the clock I40, to thereby move the arm I39 into and out of engagement with a contact I once for each complete operative cycle of the apparatus. As hereinafter explained, the clock control switch I39 is provided to prevent interruption of the operation of the apparatus, by an. opening adjustment of the switch element I38 at a, time when the bed of moisture absorbing material I2, is in the wet condition normally prevailing at the end of each dehumidiflcation stage. The contact MI is elongated and disposed so as to be in engagement with the switch element I39 for a couple of minutes or so prior to the hereinafter described interruption of the clock-movement occurring at the end of each dehumidiflcation period. I The terminals of the fan or blower motor 40 are connected by conductors I42 to the terminals I30a and I3Ia, so that the motor 46 isenergized, so long as the coil I36is energized. The terminals I 30a and I3Ia are connected tdconductors I43 and I 44, respectively, which supply current.

for energizing the damper motor I22, but the latter is a reversible motor, which is operatively en ergized only when a switch element I45 is adjusted to connect a common motor control'conductor I46 to one, or to the other, of two other control conductors I41 and I48. The switch element I 45 forms a part of the clock or timing mechanism I40, and is given one complete rotation, effected in two steps, for each operating cycle of the dehumidifying unit. When the switch member I45 connects the conductors I46 and I41, the motor I 22 is operated to give the half turn to the motor crank arm I2I, required to shift the valves or 'describedherein, wherebythe motor automatically de-energizes itself at the end of each of its movements giving the arm IZI a half turn in one direction or the other. I

In the control system shown in Fig. 9, the op-. eration of the clock I40, while determining the duration of each dehumidification period, is intermittently in operation, and does not control the duration of the activation or regeneration periods. The energizing circuit connection for the clock I4Ii,includes an energizing conductor I49 directly connected to the terminal I30a, and a cooperating energizing conductor I50 intermittently connected to, and disconnected from the terminal I3Ia, at intervals controlled and determined by two switch mechanisms. those mechanisms includes a, switch arm I5I adjusted by the damper motor I22 on each operation of the latter, and the second mechanism, I152, is automatically responsive to the tempera,- ture in the waste air outlet 4 of the unit, or in the exhaust or stack connection leading away from that outlet.

During each period in which the adjustment position of the motor I22 and its crank arm I2I, is such as to hold the damper I9 open, and the dampers I1 and 35 closed, as required for dehumidification, the clock I4!) is energized by a circuit closed by the switch arm I5I, and not controlled by the switch mechanism I52. The clock energizing circuitthen closed includes the energized terminal IlIIa, conductors I49 and I55, energized terminal I5Ila, of terminal board I82, conductor I 53, switch arm I5I, conductor I54 and I44, and energized terminal I3Iat' The clock energizing circuit just described is broken, and the clock operation interrupted, by the movement of switch arm I5I out of operative connection with the conductor I53, effected when the motor I22 is energized by movement of clock switch arm I45 to close damper I9 and open dampers I1 and 35, for regenerative air flow through the material- I2.

That operation of the motor I22 moves the switch arm I5I out of its previously maintained engagement with the switch contact connected to the conductor I55, and opens the previously described clock energizing circuit, and the operation of the clock then ceases until a second clock One of energizing circuit is established by the operation of the switch mechanism I52. The latter may be of the commercial form manufactured'by the Detroit Lubricator Company and designated Control switchNo. 250 Type MEI-2, and operatesto adjust the switch arm I55 with a snap action from its left hand, full line position, into its right hand, dotted line position shown in Fig. 9, or from said dotted line, into said full line position, accordingly, as the waste air temperature attains or is below a predetermined temperature, which normally is within a range of- 250 to 300 F. That temperature is attained in the normal operation of the dehumidifying unit illustrated, when, and only when, the material I2 is adequately regenerated or activated. During, and

prior to the completion of, the desired activationv operation, the moisture given up by the material I2 to the regenerating air cools the latter, so that it reaches the outlet 4 at a temperature 'below that required for the movement of the switch arm I55 into its dotted line position.

The said second. clock energizing circuit closed by the movement of the switch arm, I55, into its dotted line position, includes conductors I49 and I50, a conductor I56 connecting contact I5Ila, to a stationary contact of switchtmechanism I52 then engaged by switch arm I55, a conductor I51 connecting arm I55 to a terminal" 658, of termi-' nal board I32, a conductor I59 connecting terminal I58 to a stationary contactof the damper motor switch mechanism, said stationary contact being then engaged by the switch arm i5I an thereby connected to conductor Md.

Following the closure of the' energizing circuit just described, the clock I40 starts into operation, and runs during a short purging period of three minutes or so, before the resultant movement of the clock switch arm I45 brings the latter into circuit relation with the control conductor I48, and thereby actuates the motor 922 to adiust the dampers II, I9, and 35 into their dehumidifying positions and initiate the following dehumidification stage. The last mentioned operation of motor I22, moves the switch arm i5i out of connection with conductor I59, thereby breaking the conductor I 54, thus immediately restoring the first mentioned energizing circuit for the clock m, which thereafter runs continuously until the last mentioned dehumidification stage is completed. i

-Dur ing the above mentioned purging period, which may be regarded as a final portion of the regeneration period, the main gas valve 84 is Y closed, and the air then passing to the waste air outlet through the material I2, subjects the latter to a substantial cooling action, desirable priorto use of the material in the following dehumidificationstage.

With the control system shown in Fig. 9,,the

operation of the main gas valve 84 is electri- .caliy controlled, and the valve can be moved into and maintained in its open position only during a period in which the dampers I'I, I9, and 35 are not only adjusted for regenerative action, but in which the waste air temperature is suitably low, and then only it there is a pilot burner heme, and it the air heater temperature is notabnormally high.

The valve 84 illustrated, is a so called motorized valve of known type including an electric motor I 50 is connected in the secondary circuit I6I of a transformer I62. The primary winding I63 of the transformer is included in a circuit which is energized only when the switch arm I55 of switch mechanism I52 is in its low temperature, full line position, and the switch arm I5I is in the position occupied when the dampers I! and 35 are open and the damper I9 is closed. With the switch arms I55 and I5I in said positions, the primary winding I53 is connected between the energized terminals I3Ila and Iiila, in series with a terminal I65 of terminal board I32, conductor Hi5; switch arm I55, conductor I57, terminal I58, conductor I59, switch arm I5I, conductor 55 i and conductor I 'iii.

The secondary transformer circuit liiI includes in series with the motor I50, a fusible link I55, and a switch Hilassociated with a valve I58 in the pilot valve supply pipe 92, and controlled by a device H69 responsive to the heat of the flame from the pilot burner 9|.

The fusible link I65 is located in the upper burner extension of the chamber 8, so as to be subject to the temperature therein, and is adapted to give way and open the transformer circuit IEI, and thereby effect the closure of the main gas valve 845, when said temperature rises above normal, as it would on interruption of the flow of regeneration air through the chamber 8. Such air flow interruption might result from the breakage of the fan belt 41, or from the development of some condition, other than the failure of the supply current, making the fan motor 65 inoperative. The fusible link is not necessary to protect the apparatus against an interruption of the current supply by conductors I35 and ISI, since that interruption would deenergize the solenoid I36 and permit the switch m5 to open under its spring bias and thereby effect the closure of the main gas valve 84.

The opening of switch I6? opens the secondary circuit Ifii, and thereby closes the main ,gas valve M if previously open. The switch Iii'l is held in its closed position by the device I69, when the latter is subjected to the heating action of the normally continuously burning pilot burner flame. In case of the accidental extinction of that flame, the device I69 permits or effects the opening of the switch I61. The device I69 may be any suitable thermally responsive device, but advantageously, is of a known commercial form, including the hot junction of a thermo-couple having its leads, enclosed by a couple I10, connected to an electric magnetic device I'II, which is actuated by the thermo-couple current due to the heating eiIect of the pilot burner flame, to maintain the switch I61 in its closed position. Advantageously also, the device III is associated with the valve I68 so as to effect the closure of the latter, andthereby interrupt the gas flow to the pilot burner, when its flame is extinguished. The mechanical details through which the energization and deenergization of the electromagnetic device III result in the opening and closing, respectively, of the valve I68, form no part of the present invention, and hence need not be further described or referred to herein.

In the contemplated normal operation of the unit illustrated, as will be apparent from what has already been said, the fan or blower 6 moves air continuously into contact with the material I2 during the successive dehumidification and regeneration stages or periods. During each de-' humidifying period, the air flows downward through a flowpath portion including the chamtion period, the air flows downward through the chambers II and I5 and upward through the chamber I3, the flowpath in each case being U shaped.

In the contemplated normal operation of the unit, the fan 3| moves air through the air cooler passages 24 and the nozzles 2? supply water to the spray chamber, during the activation periods, as well as during the dehumidification periods. The resultant subjection of the air cooler to a cooling action during the dehumidification periods, would be unnecessary with other air cool ers which may be employed in some cases, but is desirable with the evaporative air cooler illustrated, because of the considerable heat storage capacity of the latter. In consequence, of that heat storage capacity, the cooling action to which the cooler is subjected during the regeneration periods, is advantageous because it results in a lower average cooler temperature during the dehumidification periods than would otherwise prevail, and thereby increases the effective cooling capacity of the cooler.

While general principles of the invention disclosed may be utilized in apparatus differing widely in form from that disclosed, the particular unit construction and arrangement illustrated possesses important practical advantages for the use of the unit in the cellar, basement, or analogous furnace room, of a dwelling house of moderate size.

For that use, the inherent compactness of the unit illustrated, and the location of the air inlet and air outlets at the top of the unit, are of practical importance. The unit illustrated may be generally similar in bulk, and in its space requirements, to an ordinary house heating furnace such as would ordinarily be installed in the same furnace room of a dwelling house in which the improved air heating unit is located. For such use, the location of the air inlet 2 and air outlets 3 and 4 at the top of the unit is practically convenient and desirable because of the resultant disposition permitted of the associated air conduits. For the normal contemplated use of the unit, the conditioned air outlet 3 must be connected to a conduit system through which the conditioned air is passed to the room or rooms in which that air is used, and in practically all cases, the waste air outlet 4 should be connected to a conduit leading to a stack or otherwise arranged for the discharge of the waste air into the outside atmosphere. While in some cases, the inlet 2 may open directly into the room in which the unit is located, it is generally desirable-to provide a fresh air conduit leading to the inlet 2 from the outside atmosphere. The air conduits required are of substantial cross sectional area and flow capacity, since the amount of air conditioned is desirably much in excess of the amount of fresh air needed to satisfy the standard minimum fresh air ventilation requirements of the rooms in which the conditioned air is used for conditioning, as well as for purely ventilation purposes. 4

A disposition of the moisture absorbing material I2 relative to the air flow provisions, permitting of the movement of the air to be dehumidified into series contact with the different portions of the moisture absorbing material, and the passage of the heated activating air in parallel streams into contact with said portions, contributes both to the compactness of the unit and to J may be effected with apparatus very different in form from that illustrated, but the arrangement of the material l2 in a wall or bed in the form of a corrugated cylinder and in conjunction-with valves or dampers and flowpath provisions as illustrated in the drawings, permits of the at- .tainment of the series parallel flow of air into contact with the material, in apparatus which is compact, and in. which the extent of absorbing material bed area in a direction transverse. to

the air flow, is relatively large.

In the unit arrangement illustrated, the utilization of practically the entire vertical height of the unit to accommodate thedehumidifying section of the apparatus and the necessary inlet and outlet fiowpath provisions associated therewith, contributes to the compactness of the unit, and permits the air heating apparatus to be located at the top of the unit, as is practically convenient and desirable, without necessarily increasing the vertical dimensions of the unit exsure over the pressure of the air admitted to the cept for a slight vertical elongation of the inlet air flowpath portion formed by the chamber 8,

and for the provision of the space to accommo-- date the burner gas supply connections.

The air heating apparatus illustrated has certain special advantages for use as an airheater, particularly, with the gas and air pressure conditions prevailing with the intended normal use of the unit illustrated. For that use, it is desirable that the conditioned air should be supplied to the rooms to be conditioned at a pressure slightly,

in excess of atmospheric pressure, so as to minimize the infiltration of atmospheric air into those rooms. As is well known to those skilled in the art, in an ordinary moderate sized dwelling house of normal construction and with a moderate summer wind velocity of 15 miles per hour, the amount of atmospheric air entering the house through leaky windows and other joints, is ordinarily assumed to be that required for a complete change of air in the house in some 30 to minutes. Such a considerable infiltration of atmospheric air into-rooms would materially reduce the sought for advantage of supplying dehumidified air to the rooms. By supplying the conditioned air at a pressure slightly above that of the atmosphere, the otherwise normal. amount of atmospheric air infiltration may be materially reduced.

When air to be conditioned is supplied under pressure to the chamber 8 as provided for in the particular unit construction illustrated, the air pressure in the chamber 8 may well be above the atmospheric pressure, by an amount corresponding to about one and a half inches of water. The ordinary domestic valve gas supply pressure may be expected to normally exceed the atmospheric pressure by an amount corresponding-to about two and a'half inches of water. As will be apparent, the arrangement of the burner elements to provide the special nozzle shaped flow passages 15 for the air passinginto the'combustion space surrounded by the burner elements 10, is of advantage in securing the required relatively large amount of gasflow,- through the ports 14, notwithstanding the small excess of the gas preschamber 8. With the described nozzle arrangement, the high velocity of the air streams 'disadjacent air streams.

reduces the pressure at/tha outlet 'ends of said I ports. In'effectTt he gas passing through those ports, is subjected to an aspirating action by the In my copending application Ser. No. 155,403, filed July 24, 1937,- I disclose other forms of apparatus for accomplishing the general purposes of, and obtaining advantages obtainable with, the apparatus disclosed herein, and in said application, Serial No.- l55,403, I am generically claiming features of invention disclosedin common in the last mentioned application and herein. Y

As will be apparent to those ,skllled in the art? changes may be made in the form of the apparatus illustrated and described herein without departing from the spirlt'of my invention as set forth in the appended claims, and in some cases use may advantageously be made of certain fea-- tures of my invention without a corresponding use of other features.

Having now described my invention, what I claim as new and desire to secure by Letters Pat.- ent, is:

1. Regenerative dehumidifying means comprising a pervious wall including moisture absorbing material and surrounding a space, valved partition means operable to open and close full communication between opposite end portions of said space, means defining an enclosed space surrounding said pervious wall, means operable to supply air to be dehumidified to one of said end portions and to withdraw dehumidified air from the other end portions when said portions are not in free communication, means for supplying heated air to one of said end portions and thereby to the other when the two end portions are in free communication, and means for withdrawing air from said surroundingspace.

2. Regenerative dehumidifying means comprising inner and outer screen walls in the form of corrugated spaced apart cylinders with the corrugation ribs and grooves of each wall extending parallel to the axis of the cylinders and nesting with the corrugation grooves and ribs'of the other cylinder, moisture absorbing material in the space between the shells, means defining an enclosed space surrounding the outer screen .wall, valved partition means within the inner screen wall operable to .open or close direct communication between opposite end portions of the space surrounded by the inner screen wall means for passing air into one of said end portions, means adjustable to pass air either from the opposite end portion or from said enclosing space, and air.

heating means operable to heat the air entering the first mentioned space when said end portions are in direct communication.

3. Regenerative dehumidifying means, comprising a pervious wall including moisture absorbing material surrounding a space, valve means in said space alternately operable to establish and to interrupt communication between opposite end portions of said space, casing means providing a second space surrounding said wall, and having an air outlet, intermittently operable air heating means, means operable to move air past said heating'means into one of said end portions, the

, second of said end portions having an air outlet,

valve means operable to permit or prevent the outflow of. air from said second end portion,

through its said outlet, valve means controlling the outlet from said second space, and a common operating means for the three valve means operable to adjust the latter for airfiow from said one end portion through said wall into said second space and thence through said wall into said second end portion and thence through the second mentioned outlet, and for airflow from the first mentioned end portion directly into the other end portion and from each of said end portions through said wall into said second space and thence through the first mentioned outlet.

4. Regenerative dehumidifying means comprising a pervious wall including moisture absorbing material surrounding a space, means in said space alternately operable to establish and to interrupt direct communication between opposite end portions of said space, means operable when said communication is interrupted to pass air to be dehumidified into one of said end portions, thence outwardly through the portion of said wall surrounding said one end portion and thence back into the other end portion through the portion of said wall surrounding the last mentioned end portion, and means operable when said communication is established to pass heated air into both of said end portions and thence outwardly from each of the latter through the portions of said wall respectively surrounding said end portions.

'5. In dehumidifying apparatus comprising material adapted when activated, to absorb moisture' from air in contact therewith and to be reactivated by contact with the air when the latter is heated, a chamber through which air normally passes into contact with said material at a pressure above that of the atmosphere, a gas burning air heater in said chamber, fuel gas supply means adjustable to supply fuel gas to said heater during reactivation periods and to interrupt the supply of fuel gas to the heater during dehumidification periods, a pilot burner in said chamber, said chamber having a vent to the atmosphere, and pressure responsive valve means controlling said vent and closing the latter when the pressure in said chamber is in excess of atmospheric pressure and opening said vent when the pressure in said chamber diminishes, whereby the products of combustion formed by the operation of the pilot burner may be discharged through said vent when the,normal air flow through said chamber is interrupted.

6. In dehumidifying apparatus comprising material adapted when activated to absorb moisture from air in contact therewith and to be reactivated by contact with the air when the latter is heated, a chamber through which air normally passes into contact with said material at a pressure above that of the atmosphere, a gas burning air heater in said chamber, fuel gas supply means adjustable to supply fuel gas to said heater during reactivation periods and to interrupt the supply of fuel gas to the heater during dehumidification periods, a pilot burner in said chamber, said chamber having a vent to the atmosphere, pressure responsive valve means controlling said vent and closing the latter when the pressure in said chamber is in excess of atmospheric pressure and opening said vent when the pressure in said chamber diminishes, whereby the products of combustion formed by the operation of the pilot burner may be discharged through said vent when the normal air flow through said chamber is interrupted, and means responsive to the temperature to which the air is heated by said heater for interrupting the fuel gas supply thereto when said temperature exceeds a predetermined amount.

'7. Apparatus for conditioning the air for room spaces comprising a body of material capable when activated of absorbing moisture from a stream of air passing thereover, and adapted to be reactivated by giving up previously absorbed moisture to a relatively warm air stream passing thereover; conduit means providing for the passage of air over said material and into the room space; means for moving air over said material and through said conduit means into the room space; means for periodically heating the air flowing to said material; means operable simultaneously with said heating means for diverting the warm air from said conduit means; timing -mechanism operable to effect the flow of air over said material and through said conduit means and into the room spaces for dehumidifying periods of fixed duration, and for rendering said heating means and air diverting means operative at the end of each dehumidifying period; and means responsive to 'a characteristic reflecting the moisture content of said material for rendering the heating means and air diverting means inoperative and the timing mechanism operative.

8. The method of conditioning the air in room spaces which comprises moving air at its prevailing temperature through a body of material, adapted when activated to abstract moisture from the air, for intermittent dehumidifying flow periods of equal and relatively long duration; establishing a flow path for such dehumidified air as it leaves said body of material which path leads to the space to be conditioned and lowering the dry bulb temperature of such air as it traverses such flow path; moving reactivating air through said body of material for substantially the entire duration of each of the intervals between dehumidifying flow periods to provide reactivating periods alternating with the dehumidifying flow periods, with the reactivating periods being of relatively shorter duration than the dehumidifying flow periods and being of lengths respectively dependent upon a characteristic reflecting the moisture content of said body of material; heating the reactivating air prior to contact with said body of material for at least a substantial portion of each reactivating period; and diverting the reactivating air from said flow path.

9. A method as specified in claim 8 wherein the characteristic reflecting the moisture content of the material is measured by the temperature of the reactivating air leaving the material and wherein the reactivating periods are terminated H in response to a predetermined temperature of the outgoing air indicating that the material is substantially free of moisture.

10. A method as specified in claim 8 wherein each dehumidifying period is of the order of 40 minutes and wherein the duration of each reacti vating period is of the order of 13 to 20 minutes.

11. A method as specified in claim 8 wherein all of the air moving over the moisture absorbing material is taken from a common source and moves along a single flow path leading to the material.

12. A method as specified in claim 8 wherein the air flows in series through different portions of the moisture absorbing material during dehumidifying periods and through such portions in parallel during reactivating periods.

WILLIAM R. ZUHLKE.

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