US20140041833A1

US20140041833A1 - Flexible heat and moisture transfer system

Info

Publication number: US20140041833A1
Application number: US13/964,924
Authority: US
Inventors: John Edward BRESHEARS
Original assignee: ARCHITECTURAL APPLICATIONS PC
Current assignee: ARCHITECTURAL APPLICATIONS PC
Priority date: 2012-08-11
Filing date: 2013-08-12
Publication date: 2014-02-13
Also published as: US20150075747A1

Abstract

A heat and moisture transfer system may include a flexible heat and moisture exchanger in fluid communication with an environment control unit and an enclosed space. The flexible heat and moisture exchanger may include at least one flexible water vapor-permeable membrane, and may be configured to pass air streams simultaneously in different directions in adjacent subchannels formed by the membrane.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent Application Ser. No. 61/682,232, filed Aug. 11, 2012, which is hereby incorporated by reference.

INTRODUCTION

Mechanically heated or cooled and ventilated buildings and other structures require that some portion of fresh make-up air be added continuously to the total volume of circulated air to keep the space fresh, comfortable, and healthy. A corresponding portion of the air which has already been heated or cooled to the desired supply conditions must be exhausted, resulting in a loss of heat energy and a corresponding reduction in the heating or cooling efficiency of the system conditioning the air in the spaces. Heat exchangers are sometimes used in the exhaust air and makeup airflow paths of these systems such that heat is transferred between the two airstreams according to the temperature differential, leaving less cooling or heating to be performed by the mechanical system to bring the supply airstream to its desired conditions. So-called “total heat exchangers” or “energy recovery ventilators” exchange moisture as well as heat between the two airstreams, affecting the amount of humidification or dehumidification as well as the amount of heating or cooling required of the mechanical system.
Materials used for heat exchangers commonly include metal foils and sheets, plastic films, paper sheets, and the like. Good heat exchange is generally possible with these materials, but moisture exchange cannot easily be performed. Desiccants, or moisture adsorbing materials, are occasionally employed to transfer moisture. With this method, the desiccant merely holds the moisture. To effect transfer moisture between gas streams, the desiccant must be relocated from the gas stream of higher moisture content to the gas stream of lower moisture content, requiring an additional input of mechanical energy. With many desiccant materials, satisfactory performance can be achieved only with the input of additional thermal energy to induce the desiccant to desorb the accumulated moisture.
Heat and moisture exchange are both possible with an exchange-film made of paper. However, water absorbed by the paper from condensation, rain, or moisture present in the air can lead to corrosion, deformation, and mildew growth, and, hence, deterioration of the paper exchange film. The various types of heat and moisture exchangers in common usage are generally contained within an opaque metal housing and located at or near the building air handling units in the mechanical room, basement, or rooftop of the building. In the case of temporary or portable structures, the exchangers may be integrated into or located adjacent the stand alone equipment or “environmental control units” used to supply the ventilation air. The nature of moisture exchange requires a very large surface area in contact with the gas stream, and, consequently, total heat exchangers are often very large in size when compared to heat-only exchangers. A larger exchanger in the conventional location requires additional mechanical room space and/or additional load-bearing capacity of the roof in the case of a roof-top unit.
Porous polymeric or ceramic films are capable of transferring both heat and moisture when interposed between air streams of differing energy and moisture states. A system for heat and moisture exchange employing a porous membrane is described in Japanese Laid-Open Patent Application No. 54-145048. A study of heat and moisture transfer through a porous membrane is given in Asaeda, M., L. D. Du, and K. Ikeda. “Experimental Studies of Dehumidification of Air by an Improved Ceramic Membrane,” Journal of Chemical Engineering of Japan, 1986, Vol. 19, No. 3. A disadvantage of such porous composite film is that it also permits the exchange of substantial amounts of air between the gas streams, as well as particles, cigarette smoke, cooking odors, harmful fumes, and the like. From the point of view of building indoor air quality, this is undesirable. In order to prevent this contamination of make-up air, the pore volume of a porous film is preferably no more than about 15%, which is difficult and expensive to achieve uniformly. Furthermore, a porous film made to a thickness of 5 to 40 micrometers in order to improve heat exchange efficiency tears easily and is difficult to handle.

SUMMARY

In a first example, an environmental control system may include an environmental control device having a supply air inlet and a conditioned air outlet in fluid communication with an enclosed space; and a flexible heat and moisture exchanger including a flexible shell enclosing an interior channel, and a flexible, water vapor-permeable barrier disposed within the interior channel, the barrier partitioning the interior channel into a plurality of separate subchannels such that a first subchannel is in fluid communication with an atmosphere external to the enclosed space and with the supply air inlet, and a second, adjacent subchannel is in fluid communication with the external atmosphere and with the enclosed space; wherein the exchanger is configured to receive a supply air stream flowing in a first direction through the first subchannel, and to receive an exhaust air stream flowing simultaneously in a second direction through the second subchannel.
In a second example, an apparatus for enabling heat and moisture exchange may include a flexible shell enclosing an interior channel, and a flexible, water vapor-permeable barrier within the interior channel, the barrier partitioning the interior channel into a plurality of separate subchannels; wherein the apparatus is configured to receive a first gas stream flowing in a first direction through a first one of the subchannels and a second gas stream flowing simultaneously in a second direction through an adjacent second one of the subchannels.
In a third example, a heat and moisture transfer apparatus may include a flexible heat and moisture exchanger having a flexible outer shell enclosing a plurality of subchannels formed by at least one flexible, water vapor-permeable barrier; wherein the exchanger is convertible without disassembling the exchanger between an operational mode in which a first air stream is received flowing in a first direction through a first subchannel and a second air stream is simultaneously received flowing in a second direction through an adjacent second subchannel, and a collapsed mode in which the exchanger is disconnected from the first and second air streams and arranged into a portable configuration.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of an illustrative flexible heat and moisture transfer system.

FIG. 2 is a schematic diagram of another illustrative flexible heat and moisture transfer system.

FIG. 3 is an isometric view of an illustrative flexible heat and moisture exchanger showing cross-flow through a plurality of subchannels, with a cutaway view of an upper subchannel.

FIG. 4 is an isometric view of another illustrative flexible heat and moisture exchanger showing optional integration with an enclosure surface, as well as a different outer shell configuration and number of subchannels.

FIG. 5 is an isometric view of an end portion of an illustrative flexible heat and moisture exchanger, showing a transition from the exchanger to an illustrative header and manifold.

FIG. 6 is an isometric view of an end portion of another illustrative flexible heat and moisture exchanger, showing a transition from the exchanger to another illustrative header and manifold.

FIG. 7 shows an example of a flexible heat and moisture transfer system installed in operational configuration on a portable shelter.

FIG. 8 is a sectional view of the system of FIG. 7 taken at line 8-8 as indicated in FIG. 7.

FIGS. 9 and 10 are schematic side views of illustrative portable configurations of the flexible heat and moisture exchanger of FIG. 7.

DETAILED DESCRIPTION

An efficient heat and moisture exchange apparatus is described herein which will not contaminate make-up air, and which has excellent heat exchange efficiency, high moisture exchange capability, and serves as a barrier to air flow between exhaust and makeup air streams. Furthermore, the exchanger described in the present disclosure is suitable for use with lightweight temporary, portable, and permanent structures in which the mechanical conditioning and ventilation equipment may not be located within or atop the structure but may instead stand on the ground adjacent the structure. In many of these cases, the structures may be pliable and flexible to enable packing and transport, such as tents, that are not amenable to large-scale rigid elements. Accordingly, a flexible heat and moisture exchanger is described that can be used in the operation of these flexible, mobile structures but can also be packed and transported easily with them.
Illustrative flexible heat and moisture transfer systems are shown schematically in FIGS. 1 and 2 and throughout the drawings. Unless explicitly stated otherwise, the systems and apparatuses shown in the drawings may include one or more components, structures, variations, and/or functions of one or more other systems and apparatuses described in the present disclosure. Furthermore, the structures, components, functionalities, and/or variations described, illustrated, and/or incorporated herein in connection with flexible heat and moisture transfer systems may, but are not required to, be included in other heat and moisture transfer, heating, and/or cooling systems.
In general, a flexible heat and moisture transfer system may include a lightweight, flexible, compressible, resilient, counter-flow air-to-air heat and moisture exchanger in fluid communication with an enclosed space and an environment control unit (ECU) such as an air conditioner, where the ECU is used to condition the air of the enclosed space and the exchanger is used to precondition a supply stream for the ECU by extracting useful energy from an exhaust stream exiting the enclosed space. The term “environmental control device” may be used interchangeably herein with the term “ECU.”
The lightweight and flexible nature of the exchanger facilitates new capabilities such as installing one or more exchangers in an operational mode on top of an enclosed space, which may be in the form of a portable shelter such as a tent. One or more exchangers may also be integrated into the enclosing surfaces of a portable structure. A flexible and resilient exchanger may also be collapsed for transport or storage. For example, an exchanger according to the present disclosure may simply be rolled or folded without affecting the integrity of the apparatus.
Turning to FIG. 1, an illustrative flexible heat and moisture transfer system 10 includes an ECU 12, an enclosed space 14, and a flexible heat and moisture exchanger 16. ECU 12 is in fluid communication with the enclosed space and is configured to supply enclosed space 14 with conditioned air. ECU 12 may include any suitable environment control device configured to alter one or more characteristics of the air within the enclosed space, such as temperature and/or humidity. For example, ECU 12 may include an air conditioner, a dehumidifier, a humidifier, a cooler, a heater, a furnace, a heat pump, and/or any other typical HVAC device or system. ECU 12 may include a completely portable device or system. In some examples, ECU 12 may include one or more permanently installed or non-portable components.
Enclosed space 14 may include any substantially enclosed space having an internal atmosphere capable of being controlled or conditioned using ECU 12. Enclosed space 14 may include a human-occupied enclosure, and may include openings such as one or more doors, windows, ports, curtained access points, chimneys, and the like. In some examples, enclosed space 14 is configured to house equipment or vehicles, such as an enclosure for protecting electronic equipment in a cooled environment. In some examples, enclosed space 14 includes a temporary enclosure such as a tent or shed. In some examples, enclosed space 14 is itself collapsible and portable. In some examples, enclosed space 14 is a non-portable enclosure such as a house or cabin.
Streams of air are communicated through system 10. As shown in FIG. 1, a supply stream S passes into enclosed space 14, and an exhaust stream E passes out of enclosed space 14. Supply stream S may generally be driven by a motive force imparted by ECU 12 and/or an associated fan or blower. Exhaust stream E may be driven out of enclosed space 14 by a pressure differential caused by the incoming stream S, or may itself be motivated by a fan or blower. The term “make-up” may be used interchangeably herein with the term “supply.” The term “return” may be used interchangeably herein with the term “exhaust.”
Exchanger 16 is a flexible heat and moisture exchanger and may include a flexible outer shell enclosing a channel divided into at least two subchannels 18 and 20 by a membrane 22. Membrane 22 is a flexible membrane that is substantially impermeable to the constituent gases found in air, but is water vapor-permeable and capable of facilitating heat exchange. Examples of membrane 22 are described in further detail below. In some examples, membrane 22 may be separated from the outer shell and from any additional membranes included in the exchanger by including a resilient medium in each subchannel. In these examples, the resilient medium is sufficiently air-permeable to allow adequate flows of air through the subchannels during operation. For example, the resilient medium may be porous or may include apertures or channels through the medium to bias the subchannel against collapse while still allowing air flow.
Supply and exhaust streams pass through exchanger 16, and exchange both heat and moisture via membrane 22. In an example including an air conditioner (AC unit), the AC unit functions to cool and dehumidify the air in the enclosed space, and the exchanger functions to cool and dehumidify incoming air being supplied to the AC unit. Generally speaking, exhaust air from the enclosed space will be cooler and dryer than air being supplied from an atmosphere external to the space. Accordingly, heat and moisture from the supply air will be passed to the exhaust stream due to the temperature and humidity differential across membrane 22. In an example including a heating unit, the heat exchange is reversed as incoming air is cooler than the exhaust.
In this example, exchanger 16 has a cross-flow or counter-flow configuration, and supply stream S passes through subchannel 18 in one direction at the same time exhaust stream E passes through subchannel 20 in another direction. These directions may be substantially opposite to each other, or may be transverse, such as when the flows are orthogonal to each other. In some examples, a combination of opposite and transverse flow pathways may be included in the exchanger. It should be understood that in a multi-direction arrangement, the streams may at times be parallel (i.e., flowing in the same direction) without altering the substantially cross-flow nature of the exchanger. In some examples, an exchanger according to the present disclosure may be substantially completely parallel. These examples are less efficient in terms of heat and moisture exchange, but do simplify associated header configurations, and may be suitable to certain applications. The examples described herein will be cross-flow in configuration.
In some examples, more than one membrane 22 may be included, or membrane 22 may be arranged in such a way, as to create more than two subchannels. For example, multiple parallel membranes may create stacked or layered subchannels. In other examples, subchannels may be created that are side-by-side, honey-combed, or labyrinthine. In these examples, as in the one shown in FIG. 1, adjacent subchannels will be configured to pass either supply stream S or exhaust stream E (or substreams thereof) in order to effect heat and moisture exchange across the interposed membrane.
In addition to the exchanger, ECU, and enclosed space, various conduits may be used to direct the flow of supply stream S and exhaust stream E. For example, a header 24, 26 may be included at either or both ends of exchanger 16. Each header 24, 26 may include any suitable conduit structure configured to direct the flow of a stream into or out of its associated subchannels. For example, at a first end indicated at A in FIG. 1, header 24 may interface with the end of exchanger 16 such that incoming air is directed selectively into subchannel 18, while air from exhaust stream E is directed out of subchannel 20 and away from the source of incoming air to prevent exhaust from recirculating immediately into the supply system. At a second end indicated at B in FIG. 1, header 26 may interface with end B such that supply stream S is directed out of subchannel 18 and toward an inlet of ECU 12, while exhaust stream E from enclosed space 14 may be directed into subchannel 20. Specific examples of headers such as headers 24 and 26 are described below.
Additional conduits may be included at either or both ends of exchanger 16. For example, manifold 28 may be connected to header 24 and manifolds 30 and 32 may be connected to header 26 to act as conduits for supply stream S and exhaust stream E, respectively. Each manifold may include any suitable conduit structure configured to interface with one or more headers to direct either supply or exhaust air between the header and a second location. While only a supply type of manifold is shown connected to header 24, an exhaust manifold may also (or instead) be provided, to direct exhaust air away from header 24. On the other hand, header 24 may be configured such that neither type of manifold is required. These conduits are referred to as manifolds because they may be used for connecting multiple headers from multiple exchangers, to handle cumulative exhaust and/or supply streams.
Accordingly an illustrative pathway for incoming supply air (supply stream S) may be described as flowing into manifold 28 from the external atmosphere, passing through header 24 and into subchannel 18. Flowing through subchannel 18, supply stream S exchanges heat and/or moisture with a counter-flowing exhaust stream E via membrane 22. A pre-conditioned supply stream S then exits the exchanger and passes through header 26 where it is directed into manifold 30. From manifold 30, the stream passes into ECU 12, where it is fully conditioned (e.g., cooled, dehumidified, heated, etc.) and forced into enclosed space 14. At the same time, an illustrative pathway for outgoing exhaust air (exhaust stream E) may be described as flowing into exhaust manifold from within enclosed space 14, and passing through header 26 into subchannel 20. As exhaust stream E flows through subchannel 20, heat and/or moisture are exchanged with counter-flowing supply stream S. The exhaust then passes out of the exchanger and is directed by header 26 away from any intake ports or manifolds, possibly through an exhaust manifold before being exhausted into the external atmosphere.
Exchanger 16 may be disposed at least partly on or forming a part of an outer surface of enclosed space 14. Exchanger 16 may act as an insulating device positioned between the space and an external environment. Because exhaust stream E will typically be closer in temperature to the interior of space 14 than supply stream S, exchanger 16 may be disposed such that subchannel 20 is adjacent to the space to maximize insulating effect. The physical flexibility of exchanger 16 may allow the exchanger to conform to many irregular or shaped surfaces such as those found on portable structures, tents, and the like.
FIG. 2 is a schematic diagram showing another example of a flexible heat and moisture transfer system 40 similar to system 10. System 40 includes an ECU 42, an enclosed space 44, and a plurality of flexible heat and moisture exchangers 46, 48, and 50. ECU 42 is substantially identical to ECU 12, enclosed space 44 is substantially identical to enclosed space 14, and each exchanger (46, 48, 50) is substantially identical to exchanger 16. System 40 shows an example of multiple exchangers serving a single space, with a corresponding illustrative arrangement of headers and manifolds to accommodate the added exchangers.
As shown in FIG. 2, each exchanger includes a header at each end, and manifolds connect and accumulate the various respective supply and exhaust streams. Exchanger 46 includes a header 52 at a first end A′, and a header 54 at the opposite second end B′. Exchanger 48 includes a header 56 at A′ and a header 58 at B′. Exchanger 50 includes a header 60 at A′ and a header 62 at B′. Manifold 64 connects the supply subchannels of headers 52, 56, and 60, and directs supply stream S′ to each exchanger. Manifold 66 connects the supply stream subchannels at the other end, at headers 54, 58, and 62, and directs the cumulative supply stream S′ to ECU 42. Likewise, manifold 68 connects the exhaust stream subchannels at headers 54, 58, and 62 and directs exhaust stream E′ to each exchanger.
FIGS. 3 and 4 show two illustrative configurations of layered subchannels within a flexible heat and moisture exchanger similar to exchangers 16, 46, 48, and 50. FIG. 3 shows a six-subchannel flexible heat and moisture exchanger 70 in an isometric, sectional, partially cutaway view. Exchanger 70 includes a flexible outer shell 72 and five parallel membranes 74, 76, 78, 80, and 82, each an example of membrane 22, separating the channel formed by shell 72 into six subchannels 86A, 86B, 86C, 88A, 88B, and 88C. Situated within each subchannel is a biasing material 90.
Flexible outer shell 72 may include any suitable fabric or fabric-like material that is flexible, capable of withstanding environmental conditions such as adverse weather and solar radiation, and capable of being formed into a substantially airtight, substantially waterproof, lateral enclosure or housing for conducting one or more streams of air. Flexible outer shell 72 may include a flexible material that may be a cast, woven, or molded sheet. For example, outer shell 72 may include nylon, rubber, PTFE fabric, canvas, and/or other materials. In some examples, outer shell 72 may include on an outward and/or inward-facing surface, a layer that is reflective or has a low emissivity in the solar spectrum, or the material of outer shell 72 may itself have this property. For example, an emissive layer may have an emissivity in the solar spectrum of about 0.05 to about 0.15, and may have an emissivity of approximately 0.08. Such properties may be achieved by a layer of highly reflective material such as aluminum or metalized film that is coated onto, laminated together with, adhered to, impregnated into or otherwise combined with the outer shell.
Each flexible membrane 74, 76, 78, 80, and 82 is moisture- or water vapor-permeable and also capable of facilitating heat transfer between gases on either side of the membrane. The term “barrier” may be used interchangeably with the term “membrane.” In some examples, each water vapor-permeable barrier may include an anisotropic composite film made of porous polymeric substrate having applied thereto a water vapor-permeable polymeric material so as to form a nonporous barrier with respect to air and other gases. In some examples, the porous polymeric substrate may include a porous PTFE membrane. In some examples, the non-porous water vapor-permeable polymeric material may include a hydrophilic polyurethane polymer.
As generally described above, each membrane 74, 76, 78, 80, 82 may be interposed between a gas stream having a first, higher water content, and a gas stream having a second, lower water content stream. Moisture from the gas stream having the higher water content permeates through the composite film to the side adjacent the gas stream having the lower water content where the moisture is taken up by the gas stream having the lower water content. Heat from the higher temperature gas stream is conducted through the composite film and taken up by the lower temperature gas stream, thereby effecting heat and moisture exchange between the gas streams adjacent each side of the barrier.
Accordingly, supply and exhaust streams will be passed through alternating subchannels to enable the heat and moisture exchange discussed above, as shown in FIG. 3. Specifically, exhaust streams will be passed through subchannels 86A, 86B, and 86C, while supply streams are simultaneously passed through subchannels 88A, 88B, and 88C.
Biasing material 90 may be included in each subchannel to bias the respective subchannel against collapse. Because the various components of exchanger 70 are flexible, a continuous opening along the length of any given subchannel may not be guaranteed. Accordingly, some sort of biasing material or structure may be included within a subchannel to maintain a continuous path for an air stream. Biasing material 90 may include any suitable lightweight, flexible structure and/or material that is porous or permeable with respect to the constituent gases of air, while being resilient and sufficiently structural to prevent collapse of the subchannel during normal operation. In some examples, biasing material 90 may include a resilient corrugated structure forming longitudinal channels within the subchannel while separating adjacent membranes. In some examples, biasing material 90 may include a thick, porous, air-permeable sheet formed of a heat-set polyamide mesh. The term “spacer” may be used interchangeably with “biasing material.”
Biasing material 90 may also facilitate the portable or storage configuration of an exchanger, because the resilience of biasing material 90 allows the exchanger to be partly or completely collapsed and subsequently placed back into operation without losing structural integrity. In other words, the exchanger itself does not need to be disassembled in order to collapse it for transport or storage. Additionally, in some examples, the spacer material may be unattached or substantially physically independent of the membranes and outer shell, which may further facilitate collapse by preventing binding during folding or rolling of the exchanger. In some examples, the spacer material is removable for replacement or disassembly.
Spacer or biasing material 90 may function to create a more tortuous path for air flow through an otherwise continuous subchannel, thereby increasing potential heat and moisture exchange. However, biasing material 90 should not cause a large drop in pressure across the exchanger, in order to remain adequately functional as a conduit for air flow. In some examples, a permeability of the biasing material may be preferably no less than approximately 254.0 cm³/s-cm²(i.e., 500 ft²/min/ft²) when tested per ASTM Standard D737-04 (2012) at testing conditions of 21±1 degree C., 65±1% relative humidity, and 125 Pa.
FIG. 4 shows another example of a flexible heat and moisture exchanger 90 in an isometric sectional view. Exchanger 90 is substantially similar to exchanger 70. However, exchanger 90 includes an outer shell 92 that is sewn or welded together at a flange 94, and includes three membranes 96, 98, and 100 separating four subchannels 102A, 102B, 104A, and 104B, each biased against collapse by a fill material 106. In this example, exhaust air may flow through subchannels 102A and 102B, while supply air flows through subchannels 104A and 104B. In some examples, exchanger 90 may be joined to or integrated into portions of a wall or other surface 107 of the enclosed space, such as at flange 94. In these examples, the exchanger itself comprises a portion of the enclosure.
FIGS. 5 and 6 show two different examples of terminal ends of exchangers such as exchanger 70 and 90, with different header and manifold configurations. FIG. 5 is a partially-exploded, isometric view of a four-subchannel flexible heat and moisture exchanger 110 that is substantially similar to the exchangers described above. In this example, exchanger 110 includes four subchannels 112A, 112B, 114A, and 114B, and terminates in a triangular configuration 116, forming two faces 118 and 120. Each face exposes open ends of the subchannels. In this example, subchannels 112A and 112B are used for an exhaust stream, while alternating subchannels 114A and 114B are used for a supply stream. On face 118, corresponding subchannels 114A and 114B are blocked, while on face 120, corresponding subchannels 112A and 112B are blocked. Accordingly, face 118 allows the exhaust stream to pass through while blocking the supply stream, and face 120 allows the supply stream to pass through while blocking the exhaust stream.
A header 122 is configured to attach to the end of exchanger 110 as shown in FIG. 5, by sliding over the end or otherwise attaching such that faces 118 and 120 are enclosed within the header. An apex 124 where faces 118 and 120 meet is configured to contact an inner wall of the header, and the header is friction fit to the top and bottom of the exchanger, thereby isolating face 118 from 120. Header 122 includes two legs 126 and 128, each leg forming a duct or conduit extending from a respective face of exchanger 110. In this example, leg 126 extends from face 118, and leg 128 extends from face 120. A distal end of each leg is configured to be operatively connected to a manifold, such as to manifolds 130 and 132 depicted in FIG. 5.
Multiple exchangers may be disposed side by side. Accordingly, legs 126 and 128 may be shaped or positionable to avoid interfering with adjacent headers or manifolds. For example, as depicted in FIG. 5, leg 128 may have an S-shaped profile to place a distal end of the leg in a different plane than a distal end of leg 126. This arrangement would allow, for example, the overlapping configuration of manifolds shown in FIG. 2. Other configurations are possible.
Turning to FIG. 6, another example of an exchanger/header/manifold is depicted in an isometric, partially exploded view. In this example, a flexible four-subchannel heat and moisture exchanger 140 that is substantially similar to the exchangers described above. In this example, exchanger 140 includes four subchannels 142A, 142B, 144A, and 144B, and terminates in a rectangular configuration 146, forming two faces 148 and 150. Each face exposes open ends of the subchannels. In this example, similar to the example of FIG. 5, subchannels 142A and 142B are used for an exhaust stream, while alternating subchannels 144A and 144B are used for a supply stream. On face 148, corresponding subchannels 144A and 144B are blocked, while on face 150, corresponding subchannels 142A and 142B are blocked. Accordingly, face 148 allows the exhaust stream to pass through while blocking the supply stream, and face 150 allows the supply stream to pass through while blocking the exhaust stream.
As with the previous example, a header 152 is configured to attach to the end of exchanger 140 as shown in FIG. 6, by sliding over the end or otherwise attaching such that faces 148 and 150 are enclosed within the header. Here, however, the header is shaped to friction fit to all four sides of the exchanger, isolating face 148 from face 150 by providing spaced apart legs 156 and 158 that each only opens to one face of the exchanger. Each leg forms a duct or conduit extending from a respective face of exchanger 140, and includes a distal end configured to be operatively connected to a manifold, such as to manifolds 160 and 162 depicted in FIG. 6.
As in the previous example, the legs of header 152 may be shaped or positionable to avoid interference when multiple exchangers are disposed side by side. In this example, legs 156 and 158 extend in orthogonal directions to place a terminal end of leg 156 to a different plane and a different orientation than a terminal end of leg 158. This arrangement would allow, for example, the parallel manifold configuration shown in FIG. 6. Other configurations are possible.
FIGS. 7 and 8 respectively show an isometric view and a sectional view of an illustrative heat and moisture transfer system 170 installed in an operational configuration 172. System 170 includes an ECU in the form of an AC unit 174, an enclosed space in the form of a tent 176, multiple flexible heat and moisture exchangers 178, 180, and 182, and a combination header and manifold 184.
The components shown in FIGS. 7 and 8 are substantially similar to the corresponding components described above for systems 10 and 40. Exchangers 178, 180, and 182 are configured as panel-like, flexible devices that are laid side-by-side over the top of tent 176. In this example, tent 176 has a rounded roof. It should be understood that exchangers constructed according to the present disclosure could be laid over a tent or other structure having a peaked roof or any other practical profile. For ease of explanation, exchangers 178, 180, and 182 are depicted as two-subchannel exchangers. However, each exchanger may have any number of subchannels, as described above.
The three exchangers in this example are connected at one end to a single divided manifold 184 that also functions as a header similar to those described regarding FIGS. 5 and 6. Manifold 184 may be constructed of a fabric or other material similar to the outer shell of an exchanger, or may be constructed of a rigid material such as sheet metal or standard ducting. Manifold 184 may be temporarily or permanently connected to the exchangers, and may be collapsible along with the exchangers when converting them to transport or storage configuration.
Operation of the system depicted in FIGS. 7 and 8 will now be described, in order to explain further the various structures and devices involved. Beginning at the distal ends of the exchangers, supply air is drawn into a supply subchannel 186 by a motive force provided by AC unit 174 or by a fan or blower (not shown). Passing through the exchangers, supply air is cooled and dehumidified by exchanging heat and moisture with cooler, dryer exhaust air in an adjacent exhaust subchannel 188 via a membrane 190. The supply air then exits the exchangers and passes into a supply side 192 of manifold 184, where it accumulates and passes through a duct 194 leading from the manifold to the AC unit. The AC unit then conditions the air by cooling and dehumidifying, and pumps the conditioned air through a port in the tent via another duct or conduit 196.
The conditioned air then becomes a part of the general atmosphere internal to the tent. The air circulates throughout the space, and generally is heated and becomes more humid as it encounters occupants, outside air entering through a door or window, general heat transfer through the walls of the tent, and other phenomena. Due to a pressure differential or a motive force such as a fan or blower (not shown), air inside the tent is expelled through one or more exhaust ports 198 and into an exhaust side 200 of manifold 184. From there, the exhaust stream enters exhaust subchannel 188 of each exchanger, and travels through the exchangers. Because the exhaust stream is typically still cooler and dryer than outside air in the supply stream, heat and moisture are transferred to the exhaust stream from the supply stream via membrane 190. The exhaust stream then exits the exchangers, and may pass through a manifold or other conduit (not shown) before entering the general outdoor atmosphere.
FIGS. 9 and 10 are schematic side views of two different portable configurations or modes of an exchanger such as the exchangers described in the previous example. FIG. 9 shows a portable configuration or mode 202 in which an exchanger 204 is rolled. FIG. 10 shows a portable configuration or mode 206 in which an exchanger 208 is folded. One having skill in the art will appreciate that many possible configurations are possible for placing a lightweight flexible heat and moisture exchanger into a collapsed mode allowing it to be easily stored or transported. It will also be understood that, although portions of the exchanger may be collapsed, crushed, or pinched, the resilient and flexible characteristics provided by the components of an exchanger constructed according to the present disclosure will facilitate placing the exchanger back into operation without a loss of functionality.

Examples and Additional Details

Some embodiments of the present disclosure may be described as an apparatus for enhanced heat and moisture exchange between make-up and exhaust air streams including a flexible housing having an exterior wall defining an interior channel through which air streams may pass and a water vapor permeable barrier disposed within the interior channel so as to partition the interior channel into a plurality of subchannels. The flexible housing may comprise a flexible material that may be created as a cast, woven, molded sheet or other format. The layers of water vapor permeable membrane, which are also flexible, may be separated into a plurality of subchannels by the insertion of a flexible, porous sheet medium between membrane layers. The porous medium may be created from woven or non woven nylon, cast or molded plastic, or other organic and inorganic materials.
Some embodiments of the present disclosure may be described as an apparatus for enabling heat and moisture exchange including an exchanger housing comprising a flexible exterior wall defining an interior channel through which a gas stream may pass. A water vapor permeable barrier is disposed within the interior channel and partitions the interior channel into a plurality of subchannels. The subchannels defined within the apparatus are connectable to makeup and exhaust air streams or sources thereof.
Some embodiments of the present disclosure may be described as a heat exchanger enclosed in a flexible housing comprising a flexible material that may be created as a cast, woven, molded sheet or other format.
Some embodiments of the present disclosure may be described as having layers of water vapor permeable, flexible membrane that may be separated into a plurality of subchannels by the insertion of a flexible, porous sheet medium between membrane layers. The porous medium may be created from woven or non-woven nylon, cast or molded plastic, or other organic and inorganic materials.
Some embodiments of the present disclosure may be described as having the pressure of the gas streams controlled so that the makeup and exhaust streams flow through the subchannels of the exchanger apparatus in different directions.
Some embodiments of the present disclosure may be described as having the radiant exchange between surfaces of the apparatus controlled or affected through the inclusion of one or more material layers with particular reflective or transmissive properties within the radiation spectrum of interest. The radiant barrier layer or layers may comprise a layer forming the exchanger housing, an interior subchannel layer, or it may be formed by coating a substance with the desired radiant properties onto a surface of one of the existing material layers within the apparatus.
Some embodiments of the present disclosure may be described as a flexible heat and moisture exchanger mounted onto or incorporated within the exterior surface of the structure where, by virtue of the heat and moisture exchange between the airstreams flowing within it, the exchanger alters the overall transfer of heat between the interior and exterior of the structure.
Some embodiments of the present disclosure may be described as having an entire exchanger apparatus constructed from flexible materials as described above in order to enable it to conform to the surface of a structure with complex geometry. The exchanger apparatus may also be constructed from flexible materials to enable it to be packable and lightweight for easier transport.
Some embodiments of the present disclosure may be described as a flexible exchanger laid over the exterior surface or connected to the interior surface of a lightweight or temporary structure, such as a tent. In this embodiment, the subchannels of the exchanger are connected to the supply and return airstreams of the mechanical ventilation and conditioning unit serving the structure.
Some embodiments of the present disclosure may be described as a flexible exchanger integrated into the surface of a lightweight or portable structure. In the case of a tent or fabric structure, the exchanger apparatus may be sewn or welded into the tent surface. The exchanger may be connected to the supply and return airstreams as described in the previous embodiment.
Some embodiments of the present disclosure may be described as a method for exchanging heat and moisture between a first gas stream having a higher water content and a second gas stream having a lower water content comprises the steps of separating the first gas stream and the second gas stream with a flexible water vapor permeable barrier, and controlling the pressure of the first gas stream and second gas stream to enable exchange of heat and moisture between the streams.
Some embodiments of the present disclosure may be described as having a membrane dividing the two channels through which the gas streams flow, configured to maximize surface contact with the gas streams and tortuousity of the gas stream flow. Both configuring the geometry to maximize gas stream surface contact and gas stream turbulence and tortuousity serve to enhance the transfer of heat and permeation of water vapor from one gas stream to the other.
Some embodiments of the present disclosure may be described as including a membrane impregnated with a substance to enhance the permeation of water vapor from one gas stream to the other. Such substance may be highly hygroscopic. Further, the substance may be a hygroscopic electrolyte that would enhance the flux factor by two to five without any adverse effects on the selectivity. Preferably, the electrolyte is a salt of an alkali metal, an alkaline-earth metal or a transition metal. In particular, the metals lithium, sodium, potassium, magnesium and calcium are available, but also other metals from the groups named. The salt is preferably a chloride, bromide, fluoride, sulphate or nitrate. Preferably, the choice is for a salt whose saturated solution in water has a vapor tension which is lower than the partial water vapor tension of the mixture to be dehydrated. Salts such as LiBr, KCl, MgCl₂, CaCl₂, SrSO₄, and NaNO₃are found to give an excellent result. Salts which are readily soluble in water and have hygroscopic properties may be capable of producing satisfactory results.
Based on the above description and the associated drawings, the following numbered paragraphs describe examples of various embodiments of systems and apparatuses of the disclosure.
A0. An environmental control system comprising: an environmental control device having a supply air inlet and a conditioned air outlet in fluid communication with an enclosed space; and a flexible heat and moisture exchanger including: a flexible shell enclosing an interior channel; and a flexible, water vapor-permeable barrier disposed within the interior channel, the barrier partitioning the interior channel into a plurality of separate subchannels such that a first subchannel is in fluid communication with an atmosphere external to the enclosed space and with the supply air inlet, and a second, adjacent subchannel is in fluid communication with the external atmosphere and with the enclosed space; wherein the exchanger is configured to receive a supply air stream flowing in a first direction through the first subchannel, and to receive an exhaust air stream flowing simultaneously in a second direction through the second subchannel.
A1. The system of paragraph A0, further including a resilient, air-permeable spacer disposed within each subchannel configured to bias the respective subchannel against collapse.
A2. The system of paragraph A0, wherein the heat and moisture exchanger is convertible, without disassembly of the heat and moisture exchanger, between an operational configuration in which the heat and moisture exchanger conforms at least in part to a surface of the enclosed space, and a portable configuration in which the heat and moisture exchanger is collapsed.
A3. The system of paragraph A0, wherein the water vapor-permeable barrier comprises a membrane that is substantially impermeable to constituent gases of air.
A4. The system of paragraph A0, further including a conduit portion configured to conduct the supply air stream from an end portion of the heat and moisture exchanger to the supply air inlet of the air conditioning device.
A5. The system of paragraph A4, further including a header portion configured to directionally separate the supply air stream from the exhaust air stream at the end portion of the heat and moisture exchanger.
A6. The system of paragraph A0, wherein the heat and moisture exchanger is a first heat and moisture exchanger, the system further including a substantially identical second heat and moisture exchanger and a flexible manifold configured to place the respective end portions of the first and second heat and moisture exchangers into fluid communication with each other.
A7. The system of paragraph A0, wherein the flexible heat and moisture exchanger is further configured to be disposed at least partially on a surface of the enclosed space.
A8. The system of paragraph A7, wherein flexible heat and moisture exchanger is further configured to be disposed with the second subchannel disposed closer to the surface of the enclosed space than the first subchannel.
A9. The system of paragraph A0 wherein the flexible heat and moisture exchanger is integrated into a surface of the enclosed space.
B0. An apparatus for enabling heat and moisture exchange, the apparatus comprising:

- a flexible shell enclosing an interior channel; and
- a flexible, water vapor-permeable barrier within the interior channel, the barrier partitioning the interior channel into a plurality of separate subchannels;
- wherein the apparatus is configured to receive a first gas stream flowing in a first direction through a first one of the subchannels and a second gas stream flowing simultaneously in a second direction through an adjacent second one of the subchannels.

B1. The apparatus of paragraph B0, further including a resilient, air-permeable material disposed within each subchannel for biasing the respective subchannel against collapse.
B2. The apparatus of paragraph B0, wherein the water vapor-permeable barrier comprises a membrane that is substantially impermeable to constituent gases of air.
B3. The apparatus of paragraph B0, wherein the flexible shell further comprises a layer having an emissivity of about 0.05 to about 0.15 in the solar spectrum.
B4. The apparatus of paragraph B0, wherein the apparatus is configured to be in fluid communication with an enclosed space.
B5. The apparatus of paragraph B4, wherein the apparatus is configured to conform at least in part to a surface of the enclosed space.
B6. The apparatus of paragraph B5, wherein the enclosed space comprises a tent, and the apparatus is configured to conform at least in part to a roof portion of the tent.
B7. The apparatus of paragraph B4, wherein the apparatus is configured to form at least a portion of an outer surface of the portable enclosed space.
C0. A heat and moisture transfer apparatus comprising:
a flexible heat and moisture exchanger having a flexible outer shell enclosing a plurality of subchannels formed by at least one flexible, water vapor-permeable barrier;
wherein the exchanger is convertible without disassembling the exchanger between an operational mode in which a first air stream is received flowing in a first direction through a first subchannel and a second air stream is simultaneously received flowing in a second direction through an adjacent second subchannel, and a collapsed mode in which the exchanger is disconnected from the first and second air streams and arranged into a portable configuration.
C1. The system of paragraph C0, wherein the exchanger is configured to be arranged into the portable configuration by folding.
C2. The system of paragraph C0, the first subchannel of the exchanger further including a resilient, porous spacer configured to bias the first subchannel against collapse.

CONCLUSION

The disclosure set forth above may encompass multiple distinct inventions with independent utility. Although each of these inventions has been disclosed in its preferred form(s), the specific embodiments thereof as disclosed and illustrated herein are not to be considered in a limiting sense, because numerous variations are possible. The subject matter of the inventions includes all novel and nonobvious combinations and subcombinations of the various elements, features, functions, and/or properties disclosed herein. The following claims particularly point out certain combinations and subcombinations regarded as novel and nonobvious. Inventions embodied in other combinations and subcombinations of features, functions, elements, and/or properties may be claimed in applications claiming priority from this or a related application. Such claims, whether directed to a different invention or to the same invention, and whether broader, narrower, equal, or different in scope to the original claims, also are regarded as included within the subject matter of the inventions of the present disclosure.

Claims

What is claimed is:

1. An environmental control system comprising:

an environmental control device having a supply air inlet and a conditioned air outlet in fluid communication with an enclosed space; and

a flexible heat and moisture exchanger including:

a flexible shell enclosing an interior channel, and

a flexible, water vapor-permeable barrier disposed within the interior channel, the barrier partitioning the interior channel into a plurality of separate subchannels such that a first subchannel is in fluid communication with an atmosphere external to the enclosed space and with the supply air inlet, and a second, adjacent subchannel is in fluid communication with the external atmosphere and with the enclosed space;

wherein the exchanger is configured to receive a supply air stream flowing in a first direction through the first subchannel, and to receive an exhaust air stream flowing simultaneously in a second direction through the second subchannel.

2. The system of claim 1, further including a resilient, air-permeable spacer disposed within each subchannel configured to bias the respective subchannel against collapse.

3. The system of claim 1, wherein the heat and moisture exchanger is convertible, without disassembly of the heat and moisture exchanger, between an operational configuration in which the heat and moisture exchanger conforms at least in part to a surface of the enclosed space, and a portable configuration in which the heat and moisture exchanger is collapsed.

4. The system of claim 1, wherein the water vapor-permeable barrier comprises a membrane that is substantially impermeable to constituent gases of air.

5. The system of claim 1, further including a conduit portion configured to conduct the supply air stream from an end portion of the heat and moisture exchanger to the supply air inlet of the air conditioning device.

6. The system of claim 5, further including a header portion configured to directionally separate the supply air stream from the exhaust air stream at the end portion of the heat and moisture exchanger.

7. The system of claim 1, wherein the heat and moisture exchanger is a first heat and moisture exchanger, the system further including a substantially identical second heat and moisture exchanger and a flexible manifold configured to place the respective end portions of the first and second heat and moisture exchangers into fluid communication with each other.

8. The system of claim 1, wherein the flexible heat and moisture exchanger is further configured to be disposed at least partially on a surface of the enclosed space.

9. The system of claim 8, wherein flexible heat and moisture exchanger is further configured to be disposed with the second subchannel disposed closer to the surface of the enclosed space than the first subchannel.

10. An apparatus for enabling heat and moisture exchange, the apparatus comprising:

a flexible shell enclosing an interior channel; and

a flexible, water vapor-permeable barrier within the interior channel, the barrier partitioning the interior channel into a plurality of separate subchannels;

wherein the apparatus is configured to receive a first gas stream flowing in a first direction through a first one of the subchannels and a second gas stream flowing simultaneously in a second direction through an adjacent second one of the subchannels.

11. The apparatus of claim 10, further including a resilient, air-permeable material disposed within each subchannel for biasing the respective subchannel against collapse.

12. The apparatus of claim 10, wherein the water vapor-permeable barrier comprises a membrane that is substantially impermeable to constituent gases of air.

13. The apparatus of claim 10, wherein the flexible shell further comprises a layer having an emissivity of about 0.05 to about 0.15 in the solar spectrum.

14. The apparatus of claim 10, wherein the apparatus is configured to be in fluid communication with an enclosed space.

15. The apparatus of claim 14, wherein the apparatus is configured to conform at least in part to a surface of the enclosed space.

16. The apparatus of claim 15, wherein the enclosed space comprises a tent, and the apparatus is configured to conform at least in part to a roof portion of the tent.

17. The apparatus of claim 14, wherein the apparatus is configured to form at least a portion of an outer surface of the portable enclosed space.

18. A heat and moisture transfer apparatus comprising:

a flexible heat and moisture exchanger having a flexible outer shell enclosing a plurality of subchannels formed by at least one flexible, water vapor-permeable barrier;

wherein the exchanger is convertible without disassembling the exchanger between an operational mode in which a first air stream is received flowing in a first direction through a first subchannel and a second air stream is simultaneously received flowing in a second direction through an adjacent second subchannel, and a collapsed mode in which the exchanger is disconnected from the first and second air streams and arranged into a portable configuration.

19. The system of claim 18, wherein the exchanger is configured to be arranged into the portable configuration by folding.

20. The system of claim 18, the first subchannel of the exchanger further including a resilient, porous spacer configured to bias the first subchannel against collapse.