US2993563A

US2993563A - Method and apparatus of conditioning air

Info

Publication number: US2993563A
Application number: US727436A
Authority: US
Inventors: Carl G Munters; Per G Norback
Original assignee: Individual
Current assignee: Individual
Priority date: 1957-04-12
Filing date: 1958-04-09
Publication date: 1961-07-25
Anticipated expiration: 1978-07-25
Also published as: DE1176335B; SE179887C1

Description

July 25, 1961 c. G. MUNTERS ETAL 2,993,563

METHOD AND APPARATUS 0F CONDITIONING AIR Filed April 9, 1958 4 Sheets-Sheet 1 Fig.1

INVENTORS. 52 OAQI- GEZPG/MMVE'AS BY PEIE Gwyn/A l 4 v y 1961 c. G. MUNTERS ETAL 2,993,563

METHOD AND APPARATUS OF CONDITIONING AIR Filed April 9, 1958 4 Sheets-Sheet 2 INVENTOR-5 Q 47L G E0475 700725 V Y BY Elf Quin/vhf Afmegz k y 1961 c. s. MUNTERS EIAL 2,993,563

METHOD AND APPARATUS OF CONDITIONING AIR 4 Sheets-Sheet 3 Filed April 9, 1958 twill/Z74..

INVENTORS; CA L. GEESC My N/EfS Y ?Gw ww Maya/ac d zjzwm July 25, 1961 c. G. MUNTERS EIAL 2,993,563

METHOD AND APPARATUS OF CONDITIONING AIR Filed April 9, 1958 4 SheetsSheet 4 United States Patent O 2,993,563 METHOD AND APPARATUS OF CONDITIONING AIR Carl G. Munters, 3 Danderydsvagen, Stocksund, Sweden, and Per G. Norbiick, 1 C Bergsliden, Lidingo, Sweden Filed Apr. 9, 1958, Ser. No. 727,436 3 Claims. (Cl. 183--4.6)

The present invention relates to a method and apparatus for use in a moisture transferrer and which includes a transferrer body to which a gas stream releases its vapor while a regeneration stream picks up this vapor at another location in the transferrer body. The moisture transferrer includes a casing provided with an inlet and an outlet for the two streams, the casing and the transferrer body moving relatively to one another in a closed circuit, while the two streams are conducted through the tr-ansferrer body from locations separated from one another.

The transferrer body is composed of a mass forming a series of passages made up of a material capable of absorbing or adsorbing moisture from the air, or else consists of a material impregnated with a substance capable of absorbing or adsorbing such moisture. In the following specification the important embodiments of the invention will be described and in which an air stream containing water vapor is dehumidified in the moisture transferrer and the active mass of the transferrer body possesses hygroscopic characteristics.

It is known in this art to provide moisture transferrers with a stationary casing in which a transferrer body moves in a closed circuit and in which the different parts of the transferrer body during the course of one cycle are alternately passed on one side by the air stream which is to be dehumidified, hereinafter called the primary air stream, and on the other side by a regenerating air stream which should have a sufliciently low relative humidity in order to drive out the moisture picked up by the transferrer body.

The transferrer body is usually in the form of a rotor or a wheel. The low relative humidity which the regencrating air stream requires can be obtained in a simple manner such as by means of a heating element arranged in the regeneration circuit. During its passage through the transferrer body the moisture content of the regenerating stream is incremed with a simultaneous drop of its temperature, but the regenerating stream in practice usually still contains a considerable over-temperature or waste heat upon its discharge from the apparatus. The regenerating stream therefore, must be given a heat surplus which fixes the limit of the heat economy of the moisture transferrer.

Where the moisture transferrer is a component part of an apparatus or system for conditioning the air in a room to a lower temperature and a lower moisture content than that possessed by the outer air, this air in the dehumidifying step should have as slight a temperature increase as possible over the air which is required for the actual dehumidification and which in the diagram shown in the drawings is represented by the enthalpy lines. In a moisture transferrer of the above type therefore, the transfer of sensible heat from the transferrer body to the primary air stream is held down by reducing as much as possible the sorbtion mass of the transferrer body which is carried over per 'unit by time, from one air stream to the other. 7, Inorder to further reduce this undesirable heat addition to the dehumidified primary air it has been suggested to providebetween the regenerating zone and the dehumidifying zone of the moisture transferrer, a smaller sector which can be purged by untreated primary air which cools the transferrer body before the latter, during its rotation enters the drying Zone or the dehumidifying zone. The small amount of air required for the cooling is then inducted into the regenerating airv stream so that the heat picked up by the latter can be utilized for the regeneration. While these steps are intended to im prove the heat economy of the moisture transferrer they still have the disadvantage in that outgoing regeneration air contains a great amount of unused heat as indicated above.

It is one of the objects of the present invention to improve the coefficient of performance of the moisture transferrer, i.e. the ratio between the heat of evaporation and the heat equivalent of the external work supplied by the apparatus. This is obtained principally by the fact that the additional heat which is required for the regeneration of the sorbtion mass is supplied wholly or partly by a medium that is passed through the passages in the mass and which medium is caused to circulate in a circuit between the mass and a heating device.

Another object of the invention is to supply the heat required for the regeneration either fully or partly by means of a steam-enriched gas stream which before, as well as after its passage through the mass, has a higher, and preferably a considerably higher, vapor content capacity or absolute moisture or humidity level than that of the primary air. Should the gas consist of air and the steam of water vapor, the circulation is adjusted to an absolute humidity level which before as well as after its passage through the mass is higher and preferably considerably higher than the absolute humidity level of the primary stream and the surrounding atmosphere.

A still further object of the invention is to provide a method and apparatus for conditioning air for a dwelling by recirculating and reusing a regenerating air stream which has been heated to a high absolute humidity level and from which a small portion of air is discarded during its circulation and an equal quantity substituted therefor with a resultant saving in the heat required for the regeneration.

Another object is to rout fresh ambient air or previously dehumidified air through a Zone intermediate the regenerating zone and the dehumidifying zone of the sorption mass, before co-mingling it with the recirculated regeneration air stream, thus preheating said fresh air and precooling the sorbent mass.

Still another object is to reduce the ratio of the regenerating air to the air to be conditioned with a consequent reduction of the waste heat loss.

It has been found in air conditioning that the regeneration canbe accomplished by an amount of air which is the equivalent of only 5% of the primary air.

Thus in terms of one broad aspect, the invention contemplates the utilization of a relatively very small portion of either the room air or separate ambient air for the regeneration step and discharging a corresponding amount of the regeneration air of a high absolute humidity level on the psychrometric chart after the regeneration of the sorption mass. However, if a volume of air which is only 5% of the air to be conditioned were used for the regeneration, then it would have to be heated to a temperature close to 800 C. or 1500 F. at which temperature the sorption mass simply would be consumed by combustion. The present invention, on the other hand, provides for the circulation of air in a closed circuit through a sector of the wheel which air may be heated to a temperature of only C. to 250 C. or less. As this stream is circulated through the wheel, it picks up moisture but a relatively small portion of this moisture-laden air is bled off and an equal amount of fresh outdoor air or previously dehumidified air taken from the air to be conditioned is inducted into the regencrating circuit and this small amount when heated, without addition of moisture, to a temperature on the order ably about slightly less than 2 mm.

of the radially-extending

partitions

20 and 22. the transferrer the casing isprovidedwith partitions 24 than the sector 32.

ing the enclosure.

3 of 100 C. to 250 C. will acquire the necessary moisture holding capacity to carry away the moisture driven out from the sorption mass. The cost of heating this small amount of air is very low in relation to its increased capacity to pick up moisture, with a consequent increase .in the coelhcient of performance of the apparatus.

The invention is described in greater detail with reference to the accompanying drawings which show, by way of example, several different embodiments for carrying out the objects of the invention.

FIGS. 1, 3, 5 and 7 show in perspective, four embodiments of the invention and in which parts of the casing ferrer body 12 is journalled on an axle 14. The transferrer body or rotor 12 comprises a mass having hygroscopic characteristics and which mass preferably consists of a carrier base for the hygroscopic substance. A series of passages is provided in the transferrer body and said passages are arranged to extend axially therein. In the embodiment shown the transferrer mass iscomposed of a series of partitions or sheets which preferably consist alternately of a plain sheet 16 and a corrugated sheet 18 which together form said axially extending passages and which passages are separated laterally from one another. The mass of the rotary transferrer is therefore preferably constructed so as to provide open passages in an axial direction while the media are prevented from streaming or flowing in a peripheral diirection during their course through the passages in the mass.

The partitions or

sheets

16 and 18 are suitably made of paper, such as asbestos paper which can be subjected to relatively high temperatures, and which is impregnated with a moisture-absorbing substance such as lithium bromide or lithium chloride. The distance between the plain sheets 16, inorder to obtain a high exchange per unit of volume, or in other Words a high coeflicient of performance, is slightly less-than 3 mm. and more prefer- At the lower part of the apparatus the casing is divided into two sectors or

chambers

19 and 21 by means Above and 26 which lie in the same plane as the first mentioned partitions, and with a third partition 28 so that the upper part of the casing is divided into three'sectors or chambers all separated from one another.

T The primary air from the enclosure which is to be conditioned is impelled by a fan 30 through the left lower sector 19. The air thus impelled passes through the passages of the transferrer partly through the. sector ;32 which is defined by the casing "10 and the

partitions

26 and 28 and partly through'the sector 34 whidh is defined .by the wall of thecasing and the

partitions

24 and 28.

The sector 34 extends over a considerably smaller area The direction of flow is indicated by the arrows on the

double lines

36 and 38." Line 36 represents the air stream which flows through the' langer sector 32 and which, after dehumidification, is to be used forits intended purpose, such as for induction air enter- The line 38 represents an auxiliary or branch strearmthe object of which is to dehumidify and cool the transferrer body, and which will be hereinafter explainedin detail. a

Through the sector 40 defined by the wall of the casing 10 and the

partitions

24 and 26 flows a streamin the direction indicated by the "arrows on the doubleline 42.

This stream is exhausted from the sector 21 and 'is then drawn, by means ofa fan 44, through a heating element 4 46 and thereafter returned to the sector 40 as shown by the double line 48. The directions of flow are therefore indicated by the

double lines

36, 38, 42 and 48, whereas the flow connections to and from the casing, and which may be of conventional design, have been eliminated in order to simplify illustration.

The ordinate in the diagram shown in FIG. 2 represents the absolute vapor content of the air, for example in gram per kilogram of airpand the abscissa represents the temperature of the air. The curves represent the different relative humidity conditions of the air. The primary air is drawn in by means of a fan 30 and has the psychrometric condition corresponding to the point 50 which may be 60% relative humidity and 25 C. In the present apparatus this air is dried to the psych-rornetric condition 52 which, for example, may be 5% relative humidity and 50 C. The differencein distance between these points from the abscissa represents the amount of moisture that has been removed from the air. The transferrer 12 rotates slowly, such as at a speed on the order of a few rotations an hour, in the direction indicated by the arrow 54. During the moisture pick up in the portion of the transferrer mass that is opposite to the sector 32, this mass will become wetter and wetter so that it must be regenerated.

As this portion of the mass enters between the

sectors

21 and 40 it is heated by the stream circulating in the

circuits

42, 48. In the embodiment shown in FIGS. 1 and 2 it is assumed that this stream consists principally of water vapor or steam. In the diagram shown in FIG. 2 it is assumed that the changes in psychrometric conditions of the steam-enriched atmosphere follow the line 56 which extends parallel with the abscissa. The line 56 is in reality located very high up on the diagram of FIG. 2 but since the diagram is not drawn to scale, this line is in a lowered position to save space in illustrating.

Beforereaching the heating element 46 the steamenriched atmosphere has the psychrometric condition 58 and it leaves the heating element with the pyschrometric condition 60. The circulating steam-enriched atmosphere passes, after it has been heated to the condition 60, through the passages in the transferrer body 12 and heats the mass. The steam-enriched atmosphere thus becomes cooled and as there will be no moisture pick up, the condition of the atmosphere is changed along the same line 56 but in an opposite direction and when it leaves the transferrer it has rc-acquired the condition indicated at 58. The condition 58 corresponds to a temperature of over 100 C. such as of the order of 120 C. and a relative humidity of the order of 30%. The condition corresponding to the point 60 is assumed to be 220 C. and 2 /2 relative humidity. Thus no moisture has, as yet, been removed from the mass of the transferrer body but it has been heated to a temperature which is immediately below that corresponding to the point 60.

During the continued rotation of the transferrer the mass comes directly opposite the narrow sector 34 where the mass is passed by the branch stream 38 having the initial condition 50. By reason of the preceding heating,

the mass has picked up so much heat that this heat is V a relative humidity which gives it the capacity to pick up moisture from the mass by evaporation. The branch stream therefore, will increase in temperature as well as in absolute moisture content and at its exitfrom the transferrer will have driven out the moisture which has been picked up by thetransferrer during the passage of the latter past'the sector 32.

. a determined by the relation between the volume of the air streams 36 and 38. Thus, if the air stream 38 is composed of 5% of the stream 36 and the latter gives up 8 grams/kg. to the transferrer, the moisture level of the air stream 38 will rise with 160 gr./kg. In FIG. 2 this moisture level has been indicated by the broken line 64. It will be noted that the temperature of this air stream is lower than that corresponding to the point 60. It is desirable that the absolute moisture level of the stream 38 shall be maintained of the order of 5 to 50 times that of the air to be conditioned.

The transferrer mass, when it enters the sector 32, is regenerated and is capable of drying the air stream 36 along the line 66 of FIG. 2 to the point 52. Simultaneously the mass has been cooled by the air stream 38.

The advantage of having the steam-enriched atmos phere circulating in a closed circuit resides, on the one hand, in the fact that the amount of heat remaining in the air stream after having passed through the transferrer, is continuously returned to the transferrer and not wasted as has heretofore been the case. On the other hand the temperature of the mass is sufiiciently high so that a very small portion of the primary air inducted by the fan 30 has to be sacrificed in order to evaporate the steam picked up by the mass. The branch stream 38 leaves the apparatus with a temperature which, in comparison with conventional systems, may be considerably higher. Despite this fact, the amount of heat which is thus lost will be considerably less than in conventional systems on account of the small volume of the air stream 38. This in turn afiects the drying economy which, according to the present invention is greatly increased. If it be assumed that this small volume of air alone is required to drive out the moisture, i.e. without the aid of the hot steam-enriched atmosphere, then this air stream must be heated to a temperature which is practically unconceivable. If the temperature of the circulating steamenriched atmosphere is assumed to vary between 120 C. (point 58) and 220 C. (point 60) and the volume circulated is five to ten times larger than the volume of the air stream 38 figured per unit of time, it is believed that the small air stream 30 must be heated in proportion to a still higher degree, i.e. to a temperature exceeding 500 to 1000 C.

The embodiment disclosed in FIGS. 3 and 4 differs from the preceding embodiment principally by reason of the fact that the air is continuously inducted into the steam-enriched atmosphere circulating in the

circuits

42, 48 while a corresponding portion of the mixture is discharged tothe surrounding atmosphere. In this case the small auxiliary air stream, whose purpose it is to remove moisture from and cool the heated mass by assistance of previously dehumidified primary air or possibly untreated air as stated in the preceding example, or vice versa, may consist of dehumidified primary air.

The

radial partitions

22 and 26 are arranged in the ,same axial plane in the embodiment of FIGS. 3 and 4. On thelower end of the transferrer is inserted a partition 68 which, together with the partition 22, divides the cylindrical space within the casing into the two sectors and 21, which sectors may be of similar size, or the "sector "19' may be larger.

The partition 24 is in the same position as that shown in the preceding embodiment, while in this embodiment the partition 28 is eliminated so that as a result the sector 32 extends over a greater area. The primary air introduced by the fan 30 is dehumidified as previously described, between the

points

50 and 52 in FIG. 4. In the sector 32 the air stream 36 is divided so that a portion thereof follows the double line 70 to be used for the intended conditioning, while a small auxiliary stream 72 is returned through the transferrer mass through a sector thereof whose angle is de fined by the

partitions

24 and 68. The auxiliary air stream 72 as previously described consists of only a small 8 portion such as 2-6 to 15% of the total volume of the primary air.

The auxiliary air stream 72 is suitably introduced into the circulating steam-enriched atmosphere in advance of the heatingelement 46. The mixture is assumed to have acquired the condition 74 in FIG. 4 and is heated by the heating element along the horizontal line 76 to the condition 78. The line 76 extends along a lower level on the diagram than the line. 56 in FIG. 2, but as previously pointed out the diagram does not reflect a definite scale. The steam-enriched mixture flowing toward the transferrer along the line 42 consists, to a large extent, of steam such as of the order of 30% per volume. However, the induction of air into the steam-enriched atmosphere has the effect that this mixture cannot only heat the transferrer mass along the sector 40, but also acquires the capacity to pick up moisture from the same. Despite the fact that the volume of the auxiliary air stream 72 is small the mixture has such a high temperature that the moisture pick-up capacity of this small volume of air has greatly increased. The changes in psychrometric conditions of the steam-enriched atmosphere follow during its passage through the transferrer mass substantially as shown by the line 80 in FIG. 4. The moisture content of the steam-enriched atmosphere increases and the line 80 forms an angle with the line 76. The final condition designated at 82 indicates that an amount of moisture corresponding to the distance of the ordinate between the points 74 and 82 has been added to the steam-enriched atmosphere.

A bleed-01f duct 83 extends from the

circuit

42 and 48 through which an amount of the steam-enriched atmosphere of the condition 82 is discharged corresponding to the amount of air added to the circuit by the auxiliary air stream 72. As in the previous embodiments, the pressures in the different parts of the apparatus must be calculated so that the intended flow directions will be obtained. Here as in all other embodiments of the invention possible leakage must always follow a direction away from the sector passed by the primary stream to the other sector or sectors and not in the opposite direction. Thus the absolute pressure shall be higher in the first-mentioned sector than in the other sector or sectors. The importance of their pressure difference is readily understood when regarding the sector 40 in FIGURE 3 where the transferrer is dried by addition of a few percent of auxiliary air. If now a few percent of the steam-enriched atmosphere should penetrate from their sector into the sector for the primary stream the drying efiect would be destroyed more or less completely.

The small auxiliary air stream 72 does not have to carry the load of removing the entire amount of the steam which is to b driven out of the transferrer and the auxiliary stream therefore, acquires a condition before its mixture with the circulation atmosphere corresponding to the moisture level 84 which represents a part of the moisture removal from the rotor mass.

In the embodiment shown in FIGS. 5 and 6 the small auxiliary air stream, Whose purpose is to remove moisture from and cool the transferrer mass 12 after the latter has passed the steam-enriched zone, is passed twice through the transferrer. In this case the small auxiliary stream is drawn from the outdoor air by means of a fan 86, and is thereafter impelled upwardly in a sector defined by the

partitions

68 and 88 in the lower part of the apparatus. The air stream passes upwardly through the transferrer along the double line 38 and is introduced into a sector which is defined by the

partitions

24 and 28 in the upper part of the apparatus. It is conducted therefrom through a duct located outside of the casing 10 represented by the double line 90 back to a sector in the lower part of the casing and which sector is defined by the

partitions

80 and 92. The air stream then passes again through the transferrer and is discharged by means of an upper sector defined by the

partitions

24 and 94. In this case the auxiliary stream is intended to be discharged to the surrounding atmosphere but it can also be introduced into the

circuit

42, 48 according to FIG. 3.

The steam-enriched atmosphere in this circuit is subjected to substantially the same changes in psychrometric conditions as in the embodiment disclosed in FIGS. 1 and .2. The'primary air is assumed to be humidified in the same manner as in the preceding embodiments. As the small auxiliary air stream is composed of outdoor air, it will have an initial psychrometric condition 96, accordingto FIG. ,6, which is .dilferent from that of the primary air, and may therefore, by way of example, correspond to. a relative humidity of 50% and a temperature of 35 T C. The final moisture level of the auxiliary air stream after the double passage through the transferrer is indicated by the line 98 in FIG. 6. This moisture level indicates a better utilization of the auxiliary air stream than in the preceding embodiments due to the repeated passage through the mass.

The embodiment shown in FIGS. 7 and 8 diifers from the preceding embodiments by the fact that the auxiliary air stream circulates in a closed circuit. The fan 86 impels the air stream upwardly between the

partitions

66 and 88 through the transferrer mass into the sector 99 between the

partitions

24 and 28 as indicated by the double line 38. The dehumidifying zone 32 and the steam circulation zone 40 are arranged on the opposite sides of smaller sectors 100, 102 defined by the

partitions

26 and 104 above the transferrer body and by the

partitions

22 and 106 below the same. The small auxiliary air stream transcends at the upper part of the apparatus to the upper sector 100 and from there downwardly 7 through the transferrer according to the double line 108 to the lower sector 102 and thereafter back to the fan 86. The transferrer 12 is cooled by the upwardly flowing branch 38 of the air stream and is pre-heated by the downwardly flowing branch 108. The cooling is effected by the transfer of sensible heat to the air stream vor by evaporation of moisture from the transferrer into the same. Similarly the pre-heating is effected by transfer of sensible heat in an opposite direction and by condensationof moisture in the transferrer. The steam content in the auxiliary air stream will be high and but for leakage and dilution with air contained in the transferrer and especially in the branch 108, might well reach atmospheric pressure. Otherwise the conditions in the steam circulating system are the same as in FIG. 1. Due to the fact that this embodiment has closed circulation circuits on the regeneration side, a bleed-off of steam from the

circulation system

42, 48 must take place, and this is elfected by the discharge 83.

A small auxiliary air stream may be introduced into the

circulation circuit

42, 48 directly from the outer air, particularly in the embodiment shown in FIGS. 7 and 8, and which is indicated by the intake 110 shown in broken lines and which may be arranged on the suction side of the fan 44 and in such case may be provided with a restriction for the flow. V

During the starting period, when the circulation circuit as shown in the several embodiments, contains atmospheric air from the start, the vapor content of the latter will progressively increase by evaporation from the 8 transferrer mass until the above described condition has been reached.

It is to be understood that the invention is not limited to the specific embodiments shown but may be expressed in a number of other embodiments all within thescope of the basic concept. For example, the casing 10 maybe rotatable while the moisture-absorbing mass remains stationary. In addition, the casing as well as the transferrer body might be made to be stationary. These and other variations are considered to be within the scope of the invention and the claims appended hereto.

What is claimed is:

1. A system for conditioning atmospheric air for an enclosure with the aid of heat and natural media .comprising, a first passage for the air to be conditioned, a

second passage for recirculating a regenerating gaseous medium and an intermediate third passage for secondary air, means for impelling said air :and said medium through said passages, a moisture transferrer comprising a solid sorbent material mounted to rotate between said passages, means for so moving said transferrer, means for heating said regenerating medium to bring it to pick up moisture to a high absolute moisture level, said third passage being connected to said first passage and to said second passage and said secondary air constituting a portion of conditioned air and being impelled through the transferrer into said second passage, and means for bleeding off a-corresponding portion of the medium in said second passage.

2. The method of conditioning atmospheric air for an enclosure which comprises the steps of passing the air to .be conditioned through a drying zone, to remove moisture therefrom, passing a heated gaseous regenerating medium through a regenerating zone, moving an air permeable mass of solid sorbent material cyclically between said zones, continuously circulating and reusing said regenerating medium through said regeneratingvzone, said .regenerating medium being heated to such a degree as to cause it to hold moisture at an absolute moisture level on the psychrometric chart which is many times higher than that of the air to be conditioned, maintaining the moisture picked up by said regenerating medium in a vaporized condition, maintaining a lower pressure in said regenerating zone than in the drying zone to provide a head suflicient to prevent the regenerating medium from flowing towards the drying zone in the event of leakage and thereby contaminate the air being conditioned, and continuously bleeding ofl" moisture from said regenerating medium only to such an extent as 'to maintain said high absolute moisture level.

3. Method of conditioning atmospheric air for .an enclosure according to claim 2, in which a corresponding amount of fresh air is substituted for the imoisture bled off from the regenerating medium.

References Cited in the file of this patent UNITED STATES PATENTS 2,053,159 Miller Sept. 1, 1936 2,535,902 Dailey Dec. 26, 1950 FOREIGN PATENTS 817,110 France of 1937