Patent Publication Number: US-2004045187-A1

Title: Heatless and reduced-heat drying systems

Description:
FIELD OF THE INVENTION  
       [0001] This invention relates generally to drying systems and, in particular, to drying systems that remove moisture from moist or wetted articles with either non-heated air or air heated to a reduced temperature.  
       BACKGROUND OF THE INVENTION  
       [0002] Conventional drying systems, such as for use to dry items including clothing, are of the once-through external air type. In such systems, the ambient air is heated with a heater, usually by exposing a forced flow of ambient air or other gas to heat generated by a gas heating box or an electric heating element. An air plenum conveys the heated drying air into a chamber enclosed within a tumbler drum. A load of water-impregnated articles is carried within the tumbler drum, which is rotated such that the articles will be tumbled while heated drying air flows through the drum. A full load of wet articles, particularly absorbent articles, may contain one to one and a half gallons of water that must be extracted. The heated drying air elevates the temperature of the articles and the water held by the articles. The heated water evaporates and is entrained in the heated air. The spent hot, moisture-laden air is discharged from the dryer. The discharge air path is typically vented to the outside of the building in which the dryer is positioned.  
       [0003] Conventional dryers equipped with a conventional heater for heating the drying air suffer from multiple deficiencies. Foremost among these deficiencies is that the primary energy consumption associated with the dryer arises from powering the heater. In addition, the heat transfer from the heater to the flowing air is relatively inefficient in that significant heat energy is wasted. Another deficiency is that the heat transferred from the heated air may deteriorate the articles in some way and, as a result, reduces their lifetime. Furthermore, certain articles, such as fabric articles, are prone to shrinkage when exposed to elevated temperatures. Yet another deficiency of conventional dryers is that the heater provides a significant fire or flammability hazard.  
       [0004] Similar to the operation drying systems used for fabric articles, other drying systems rely on a flow of a heated air or gas to a stationary chamber for removing moisture from moist or wetted articles. For example, the semiconductor packaging industry utilizes aqueous washing to remove solder flux residues from assembled dies and substrates. After washing, a heated stream of air is used to remove residual water from the surfaces of the assembly. Yet another drying system that relies on heated air for water removal is a dishwasher. At the end of a washing cycle of a dishwasher, residual water left on the dishes is evaporated by heating the residual water to a temperature greater than the dew point temperature of the air in the dishwasher chamber.  
       [0005] Therefore, it would be desirable to have a drying system that has reduced reliance on a heavy flow of heated air for removing the moisture from the articles being dried. Furthermore, it is desirable to significantly reduce or even eliminate the reliance of a drying system on any heat source. It is further desirable to reduce the detrimental effects of heat on the articles being dried. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0006]FIG. 1 is a diagrammatic perspective view of a dryer in accordance with principles of the invention;  
     [0007]FIG. 2 is a diagrammatic view of an embodiment of the dryer of FIG. 1 in accordance with principles of the invention;  
     [0008]FIG. 3 is a diagrammatic view of another embodiment of the dryer of FIG. 1 in accordance with principles of the invention;  
     [0009]FIG. 4 is a diagrammatic view of another embodiment of the dryer of FIG. 1 in accordance with principles of the invention;  
     [0010]FIG. 5 is a diagrammatic view of another embodiment of the dryer of FIG. 1 in accordance with principles of the invention; and  
     [0011]FIG. 6 is a diagrammatic view of another embodiment of the dryer of FIG. 1 in accordance with principles of the invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
     [0012] Although the invention will be described next in connection with certain embodiments, the invention is not limited to practice in any one specific type of drying system or dryer. It is contemplated that the invention can be used with a variety of drying systems, including but not limited to dryers for fabric articles or clothes dryers. Exemplary clothes dryers in which the principles of the invention can be used are commercially available, for example, from Maytag Corporation (Newton, Iowa), General Electric Company (Louisville, Ky.), Whirlpool Corporation (Benton Harbor, Ml), and Sears, Roebuck and Co. (Hoffman Estates, Ill.) and such commercially available clothes dryers can be adapted to include a drying system constructed in accordance with the present invention. It is appreciated that the drying systems of the invention may be used to dry other moist or wetted articles, such as dishes or electronic and semiconductor components, or any other washed or wetted components or articles that require active drying. The description of the invention is intended to cover all alternatives, modifications, and equivalent arrangements as may be included within the spirit and scope of the invention as defined by the appended claims. In particular, those skilled in the art will recognize that the components of the invention described herein could be arranged in multiple different ways.  
     [0013] With reference to FIGS. 1 and 2, a dryer  10  according to the principles of the invention includes an open-ended receptacle  12  rotatably disposed within an outer cabinet  14  consisting of a metal sheet housing attached to a rigid support frame. The receptacle  12  is rotated, when the dryer  10  is operating, by a motor  16  mechanically coupled with drum  12  by a drive mechanism for rotating the receptacle as understood by those of ordinary skill. A cabinet door  18  is pivotally movable between an open position permitting delivery of articles to be dried and a closed position when the dryer  10  is operating. In the open position, the cabinet door  18  provides access to a chamber  20  provided inside the receptacle  12 . The chamber  20  is adapted to accept wet or moist articles. In the closed position, a resiliently compressible sealing gasket (not shown) is captured between a portion of the outer cabinet  14  and an outer periphery of the cabinet door  18 .  
     [0014] A dehumidifying system, generally indicated by reference numeral  22 , is located inside the outer cabinet  14 . The dehumidifying system  22  is coupled in fluid communication with chamber  20  by an air passageway  23  with an inlet  24  provided in a stationary rear wall  26  of receptacle  12 . The dehumidifying system  22  includes a compressor  28  that intakes moisture-laden ambient air having the characteristics (i.e., dew point or relative humidity, temperature, etc.) of the surrounding environment through an air intake  30  and a dehumidifier  32  having an inlet port  33  coupled in fluid communication by an air passageway  35  with an outlet of the compressor  28 . It is appreciated that the compressor  28  may supply a flow of a moisture-laden gas other than ambient air to the dehumidifier  32 . The use of the terms “air” and “gas” with respect to the drying air or drying gas are used synonymously herein. A pre-filter  36  in air passageway  35  removes particulate matter and moisture, usually in the form of relatively-large entrained condensed droplets, from the air stream provided by compressor  28 . A drain  38  is provided for exhausting the accumulated moisture from the pre-filter  36 .  
     [0015] According to the principles of the invention, the dehumidifier  32  is operative for removing moisture from the flow of ambient air or gas supplied by the compressor  28  so as to significantly reduce the relative humidity of the ambient air provided to inlet  24  and to provide an output stream of drying air from an outlet port  39 . The drying air is significantly dehumidified for removing residual cleansing liquid, such as moisture, from the articles held within the receptacle  12 . The drying air is depleted of water molecules and, as a result, has a significantly enhanced moisture-carrying capacity compared with the ambient air. Therefore, moisture is absorbed, evaporated or otherwise captured by the drying air. The flow of drying air exiting the outlet port  39  of dehumidifier  32  is regulated by a flow control device  40  having an adjustable orifice or other variable stricture for regulating the flow rate of the air stream through the dehumidifier  32 . More specifically, the flow rate through the dehumidifier  32  is regulated by flow control device  40  so that the water molecules are effectively removed so as to provide the output stream of drying air having an effectively reduced relative humidity relative to the ambient air. For example, the drying air may be depleted of water molecules to provide a dew point in the range of about −40° C. to about −45° C., which corresponds to a relative humidity of about 0.2%.  
     [0016] With continued reference to FIGS. 1 and 2, the dehumidifier  32  has a membrane cartridge or membrane separator  42  having a plurality of hollow fiber membranes  41  operative to separate water molecules from the stream of pressurized moisture-laden air received from compressor  28  and thereafter expel the water molecules from the membrane separator  42  as water vapor or liquid condensate. The hollow fiber membranes  41  are formed of any material that is selectively permeable to water molecules. The stream of moisture-laden ambient air from compressor  28  is conveyed through the hollow portion of each fiber membrane  41  from the inlet port  33  toward the outlet port  39  of the membrane separator  42 . Water molecules entrained in the stream received from the compressor  28  permeate through the hollow fiber membranes  41  and are removed from the stream. The hollow fiber membranes  41  are arranged in the membrane separator  42  so the air stream flowing through the dehumidifier  32  cannot bypass the action of the hollow fiber membranes  41  during flow between the inlet and outlet ports  33 ,  39  of the membrane separator  42 . Water molecules permeating through the hollow fiber membranes  41  aggregates as moisture and drains from the membrane separator  42  through a weep hole  43  for disposal.  
     [0017] It is appreciated that the membrane separator  42  may be adapted for removing gaseous components, in addition to water molecules, from the ambient air stream received from compressor  28  so that the drying air is depleted of that gaseous component relative to the concentration of the gaseous component in the ambient air received from compressor  28 . For example, in drying systems of the invention adapted to remove moisture from corrosion-sensitive articles such as electronic components, the invention contemplates adapting the membrane separator  42 , such as by applying a suitable coating to the hollow fiber membranes  41 , to remove oxygen molecules as well as water molecules from the ambient air stream received from compressor  28 .  
     [0018] Fabric treatment chemicals, such as fabric softeners, anti-static agents and other fabric conditioners, may be provided by a dispenser  44  coupled in fluid communication with air passageway  23 . The fabric treatment chemical would be entrained in the drying air and conveyed to the chamber  20 . The flow of the fabric treatment chemical from the dispenser  44  to the air passageway  23  may be regulated or otherwise metered by a flow control device  46 , such as a conventional valve.  
     [0019] With continued reference to FIGS. 1 and 2, drying air from the dehumidifying system  22  is directed into receptacle  12  through air passageway  23 , through the inlet  24  into the chamber  20 , through the chamber  20 , and into an outlet  48  provided in the stationary rear wall  26  of receptacle  12 . A continuous flow of drying air is provided from the inlet  24  through the chamber  20  to the outlet  48  for removing moisture from the fabric articles therein by evaporative processes. The drying air has a moisture-carrying capacity due to its reduced dew point and becomes moisture-laden with the evaporated moisture. The stream of moisture-laden drying air and is exhausted from the chamber  20  via outlet  48 . A lint filter  52  disposed in the air passageway  51  is operative for trapping and holding lint and other air bourne particles originating from the articles and the stream of moisture-laden drying air. The moisture-laden drying air is directed through an air passageway  54  to the exterior of the outer cabinet  14 . The flow of drying air and entrained moisture into the outlet  48  and air passageway  52  may be assisted by a fan or blower  50  positioned within outer cabinet  14  and coupled in fluid communication with the outlet  48  by an air passageway  51 . However, it is appreciated that the pressurized flow of drying air from the dehumidifier  32  may suffice to provide an adequate flow.  
     [0020] A control system  56  (FIG. 2) is provided for controlling the operation of the various components of the dryer  10 . The control system  52  includes the necessary conventional electromechanical and/or electronic components as understood by persons of ordinary skill required to operate the dryer  10 . The dryer  10  may include a humidity sensor  58  (FIG. 2) operative to sample the environment inside chamber  20 , generate a signal representative of the percent relative humidity of air flowing through the dryer  10  during operation, and provide the signal to the control system  56 . Humidity sensor  58  may be any humidity sensor generally known in the art, and the invention is not limited to practice with any one particular type of humidity sensor. The control system  56  is also electrically coupled with, and controls the operation of, the motor  16 , the compressor  28 , the dispenser  44 , and the blower  50 , if present. A user interface  60  is provided for inputting a set of desired drying conditions to the control system  56 .  
     [0021] In another alternative aspect of the invention, the dryer  10  may be provided with a heater  62  powered by gas, steam or an electric heating element. The heater  62  may be used to heat the dehumidified air, either before the dehumidified air enters the chamber  20  of receptacle  12  or before the ambient air from the compressor  28  is provided to the inlet port  33  of the membrane separator  42 . The heater  62  operates generally to supplement the drying effect of the dehumidification of the drying air. It is appreciated that the reduced relative humidity of the air provided to the chamber  20  of the receptacle  12  during a drying operation, according to the principles of the invention, permits the heater  62  to provide a significantly reduced amount of heat for successfully drying the clothes and, as a result, the dryer  10  will consume less electrical power. It is further appreciated that, according to the principles of the invention, the utilization of heater  62  is optional and that heating of the drying air is not required before supplying the drying air to the chamber  20 . Operation of the heater  62  may be limited to periods in the drying cycle for the articles during which heated drying air is required, for example, to remove wrinkles from certain types of fabric articles.  
     [0022] The principles of the invention may be adapted for removing moisture from articles other than fabric articles as will be appreciated by persons of ordinary skill in the art. For example, the dehumidifier  32  may be coupled in fluid communication with a non-rotating receptacle (not shown) for supplying drying air to remove the moisture from wetted articles, such as dishes or electronic components, held in a chamber of the receptacle, similar to chamber  20 .  
     [0023] In another aspect, the dryer  10  may be provided with one or more electrostatic elements  64  positioned in the air flow path through the chamber  20 . The electrostatic elements  64  are typically positioned near the inlet  24  and/or the outlet  48  provided in the stationary rear wall  26  of receptacle  12 . The electrostatic elements  64  are operative to attract or repel moisture and/or particulate contamination in the stream of drying air. Various types of media are commercially available for use in the electrostatic elements and, preferably, the electrostatic elements  64  are made of a self-charging electrostatic filter material such as a woven polypropylene.  
     [0024] In yet another aspect and with reference to FIG. 1, the air passageway  23  of dryer  10  may be provided with a vortex impeller  25  positioned near inlet  24 . The vortex impeller  25  is a stationary structure including a plurality of vanes or blades angularly distributed about a shared central attachment point. The vanes of the vortex impeller  25  disrupt the flow of drying air and impart a cyclonic component to the drying air flowing from the inlet  24  into the chamber  20 , which assists in the drying action occurring in chamber  20  removing moisture from the fabric articles therein.  
     [0025] In use and with reference to FIGS. 1 and 2, the cabinet door  18  is opened, wet fabric articles are inserted into the chamber  20  of the receptacle  12 , and the cabinet door  18  is closed. The user selects a desired dryness or, alternatively, an appropriate drying time via the user interface  60 . The control system  56  responds to these selections by energizing at least the motor  16 , the compressor  28 , and the blower  50 , if present, in order to initiate a drying cycle. The motor  16  turns the receptacle  12  to tumble the wet articles during the drying cycle. The compressor  28  intakes moisture-laden air from the surrounding ambient atmosphere through air intake  30  and provides a pressurized flow of moist ambient air to the inlet port  33  of the dehumidifier  32 . The dehumidifier  32  removes water molecules from the flow of moisture-laden air and outputs a stream or flow of drying air from outlet port  39  having an increased capacity to receive and entrain moisture. The stream of drying air is substantially free of any heat added by the drying process because the use of dehumidifier  32  eliminates the need to heat the drying air to accomplish moisture removal from the wet fabric articles. The sole source of heat would relate to heating of the moist ambient air provided to the dehumidifier  32  due to the operation of the compressor  28 .  
     [0026] The drying air exiting the dehumidifier  32  is directed into the inlet  24  of the receptacle  12 . For drying fabric articles, dispenser  44  may supply a fabric treatment chemical to the stream of drying air that is injected between dehumidifier  32  and inlet  24 . The drying air envelopes and permeates the tumbling fabric articles and provides an atmosphere inside chamber  20  capable of effectively and efficiently removing water from the wet fabric articles by evaporation. To that end, the rate of water evaporation from the fabric articles is higher than that of moisture absorption into the fabric articles in the atmosphere of chamber  20 . The moisture-laden air exiting the receptacle  12  through the outlet  48  passes through the lint filter  52  to filter out lint and other particles and then is exhausted from the dryer  10  to the surrounding ambient atmosphere. The blower  50 , if present, aids in inducing a forced air flow from the inlet  24  to the outlet  48 . Typically, the exhausted air is vented outside of the building in which the dryer  10  is sited.  
     [0027] With reference to FIG. 3 in which like reference numerals refer to like features in FIG. 2, another embodiment of a dehumidifier  32   a  suitable for use with dryer  10  (FIG. 1) is illustrated. The dehumidifier  32   a  operates by pressure swing adsorption and generally includes a pair of adsorbent columns  70 ,  72  each having an enclosed cavity filled with an adsorbent material  74 . The two adsorbent columns  70 ,  72  are alternately cycled so that, while the adsorbent material  74  in column  70 , for example, is drying the stream or flow of moisture-laden ambient air or other gas provided by compressor  28 , the adsorbent material  74  in column  72  is being purged of accumulated moisture by a flow of drying air originating from column  70 . The adsorbent material  74  is any material capable of removing moisture from an airflow, such as, for example, activated alumina-based adsorbents, anhydrous calcium sulfate, silica gels, molecular sieves, zeolites, and non-zeolite molecular sieves, operable to remove moisture from the flow of moisture-laden ambient air and capable of continued moisture removal associated with repeated pressure swing cycling.  
     [0028] Flow control devices  76 ,  77  are provided in air passageway  35  between the compressor  28  and the columns  70 ,  72  and flow control devices  78 ,  79  are provided in air passageway  23  between the columns  70 ,  72  and the receptacle  12 . In addition, flow control devices  80 ,  81  are provided in a common vent line  84  extending from the dryer  10  to the ambient environment and a purge line  86  interconnects the output sides of the columns  70 ,  72 . The relative positions of flow control devices  76 - 81  determine which of the columns  70 ,  72  is operating by receiving the flow of moisture-laden ambient air from the compressor  28  and providing the flow of drying air to the chamber  20 , and which of the columns  70 ,  72  is being regenerated by drying air originating from the operating one of columns  70 ,  72 . Specifically, when column  70  is cycled to provide drying air to chamber  20 , devices  76 ,  78 , and  81  are opened and devices  77 ,  79  and  80  are closed. Humid ambient air pumped from the compressor  28  is admitted into column  70 . The adsorbent material  74  in column  70  removes moisture from the flowing air so as to generate the stream of drying air provided to chamber  20 .  
     [0029] A portion of the drying gas from column  70  is diverted into the output side of column  72  and reverse flows as a purge gas through the adsorbent material  74  in column  72  toward the input side. The drying gas from column  70  removes and entrains moisture held by the adsorbent material  74  of column  72 . The drying gas and moisture are exhausted through the vent line  84 . When column  72  is cycled to provide drying air to chamber  20 , the positions of valves  76 - 81  are reversed so that column  70  is regenerated. This cyclic mode of operation that alternates columns  70 ,  72  enables dehumidifier  32   a  to supply a continuous flow of drying air to the chamber  20 .  
     [0030] With reference to FIG. 4 in which like reference numerals refer to like features in FIG. 2, another embodiment of a dehumidifier  32   b  suitable for use with dryer  10  (FIG. 1) is illustrated. The dehumidifier  32   b  generally includes a desiccant container  90  filled with an adsorbent material  92 , an inlet port  94  provided in the desiccant container  90  and an outlet port  96  also provided in the desiccant container  90 . Moisture-laden ambient air or gas provided from compressor  28  enters the inlet port  94 , flows through the interconnected porosity of the adsorbent material  92  for dehumidification, and exits through the outlet port  96  as drying air which is directed to the chamber  20  of receptacle  12  (FIG. 1). The adsorbent material  92  is operative to remove water molecules from the stream of the moisture-laden ambient air entering the inlet port  94  and to discharge a stream of drying air from the outlet port  96 .  
     [0031] The adsorbent material  92  disposed inside the desiccant container  90  may be any material exhibiting a strong surface affinity for water, thereby providing the capability for separating water from the stream or flow of air or other gas provided to dryer  10 . The adsorbent material  92  should be capable of attractively holding the separated water without substantial re-release until the adsorbent material  92  is saturated and no longer effective for water removal. Suitable conventional water-adsorbing materials for use as adsorbent material  92  include, but are not limited to, activated alumina-based adsorbents, anhydrous calcium sulfate, silica gels, molecular sieves, zeolites, and non-zeolite molecular sieves. The adsorbent material  92  may be any one of these materials used individually or an appropriate combination of two or more materials. The adsorbent material  92  may assume any of various forms, including filters, fibers, meshes, spheres, pellets, lattices, rods, pleats, and other forms apparent to persons of ordinary skill in the art, having sufficient interconnecting porosity to facilitate air flow through the adsorbent material  92  without precipitating a significant pressure drop. It is appreciated that the adsorbent material  92  may exhibit a strong surface affinity for gaseous components in addition to water molecules in the air stream received from compressor  28 . For example, the adsorbent material  92  may be a molecular sieve material also having an affinity for oxygen molecules for those drying applications in which oxygen can cause corrosion of the articles being dried.  
     [0032] Molecular sieve adsorbents and silica gels suitable for use in the invention are commercially available, for example, from the Davison Chemicals Division of W. R. Grace &amp; Co. (Columbia, Md.). Alumina-based adsorbents suitable for use in the invention are commercially available from, for example, the Alcoa Adsorbents &amp; Catalysts Division of Alcoa World Chemicals (Leetsdale, Pa.). Calcium sulfate adsorbents suitable for use in the invention are commercially available, for example, under the DRIERITE® tradename from W. A. Hammond Drierite Co. Ltd. (Xenia, Ohio).  
     [0033] The adsorbent material  92  has a finite holding capacity for water molecules and eventually becomes saturated or ineffective as the holding capacity is approached with successive operations of the dryer  10 . When saturation occurs, the spent adsorbent material  92  may simply be replaced with fresh adsorbent material  92  when the dryer  10  is not operating.  
     [0034] In an alternative embodiment and with reference to FIG. 5 in which like reference numerals refer to like features in FIG. 4, the desiccant container  90  is equipped with a heating element  98 . The heating element  98  is any device operative to heat the adsorbent material  92  confined inside the desiccant container  90  to a temperature and for a time sufficient to desorb accumulated moisture. For example, the heating element  98  may be a resistive heating element. The vaporized water molecules escape from the desiccant container  90  by a vent (not shown). The heating cycle thermally regenerates the spent adsorbent material  92 , which is reused in dehumidifier  32   b  following regeneration. A temperature controller  100  is provided for electrically energizing and controlling the operation of the heating element  98 . The temperature controller  100  is any suitable conventional temperature controller operative for providing electrical energy to a heating element.  
     [0035] With reference to FIG. 6 in which like reference numerals refer to like features in FIG. 1 and according to an alternative embodiment of the invention, an appliance  110  includes the features of  10  and is further equipped with a liquid inlet  112  and a drain  114  so that the appliance  110  also serves as a front-loading washing machine for the fabric articles. As a result, both operations can be performed in a single device and without transferring the wet fabric articles from a conventional washing machine to a conventional dryer. The liquid inlet  112  and drain  114  each have one end coupled in fluid communication with chamber  20  of receptacle  12 . An opposite end of the liquid inlet  112  is coupled in fluid communication with a source of a cleansing liquid, such as water. An opposite end of the drain  114  extends to a disposal system for disposing of the liquid drained from the chamber  20 . The user interface  60  is used to input a desired wash cycle into the control system  56 . Control system  56  is operative for controlling the operation of the appliance  110  during the wash cycle, as well as the drying cycle. It is appreciated that the inlet  24  and the outlet  48  are each blocked by a suitable flow control device (not shown) during a wash cycle.  
     [0036] In use, the cabinet door  18  is opened, articles are introduced into the chamber  20  of the receptacle  12 , and the cabinet door  18  is closed. The user selects a desired wash cycle via the user interface  60 . The control system  56  responds to these selections by controlling the flow of liquid into chamber  20  through liquid inlet  112 , the draining of liquid from chamber  20  through drain  114 , and energizing the motor  16  in a sequence appropriate to accomplish the wash cycle. The motor  16  turns the receptacle  12  at a given rotation rate or angular velocity suitable to tumble the articles to provide a cleaning action. The motor  16  turns the receptacle  12  at a different rotation rate suitable to spin dry the wet or moist articles in preparation for a drying cycle. The drying cycle for the moist articles washed in the receptacle  12  is then accomplished by appliance  110  as described above with regard to FIGS. 1 and 2.  
     [0037] A drying system or dryer constructed according to the principles of the invention has a significantly improved efficiency of operation yet exhibits a drying capability comparable to a conventional dryer. Because of the improved efficiency, the drying system or dryer of the invention will consume less electrical energy than conventional dryers equipped with a conventional heater alone. In certain embodiments of the invention, power is consumed only by the electric motor driving rotation of the receptacle, if rotatable, and the blower drawing air through the chamber of the receptacle. For drying fabric articles, rotation of the receptacle tumbles the fabric articles while operating the drying system to provide a flow of drying air or gas to the chamber of the receptacle. The drying gas has an enhanced moisture-carrying capacity due to its relatively low dew point.  
     [0038] A drying system or dryer constructed according to the principles of the invention does not require 220 VAC or a gas supply to power a heater. In addition, the amount of heat generated by the operation of the drying system or dryer of the invention will be significantly reduced because of the elimination of the heater. Therefore, the heat load added to the environment of the building housing the drying system or dryer will be reduced. The drying system or dryer of the invention will also improve the control over the drying process. Moreover, because a heater is not required, the drying system or dryer eliminates the hazards associated with a heating element, such as flammability.  
     [0039] A dryer constructed according to the principles of the invention preserves the structure of the fabric articles being dried by eliminating the need to heat the drying air. In particular, fabric articles suffer less stress from the drying process and will have an extended wearable lifetime. Furthermore, fabric articles prone to shrinkage when exposed to heated air will benefit from the invention because of the substitution of dehumidified drying air, according to the principles of the invention, for heated drying air found in conventional clothes dryers. Generally, because fabric articles are dried at a significantly lower temperature, the constituent materials of the fabric articles being dried do not have to be heat resistant. In particular, heat intolerant fabric articles may be dried in the dryer of the invention.  
     [0040] While the invention has been illustrated by a description of various preferred embodiments and while these embodiments have been described in considerable detail in order to describe the best mode of practicing the invention, it is not the intention of the applicants to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications within the spirit and scope of the invention will readily appear to those skilled in the art. The invention itself should only be defined by the appended claims, wherein we claim: