ARCHITECTURAL HEAT AND MOISTURE EXCHANGE
An architectural heat and moisture exchanger. The exchanger defines an interior channel which is divided into a plurality of sub-channels by a membrane configured to allow passage of water vapor and to prevent substantial passage of air. In some embodiments, the exchanger includes an opaque housing configured to form a portion of a building enclosure, such as an exterior wall, an interior wall, a roof, a floor, or a foundation.
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This application claims priority from U.S. Provisional Patent Application Ser. No. 61/365,173, filed Jul. 16, 2010 which is incorporated herein by reference. This application also incorporates by reference in its entirety for all purposes the following: U.S. Pat. No. 6,178,966, issued Jan. 30, 2001 and U.S. Patent Publication No. 2007/0151447 to Merkel, published Jul. 5, 2007.
INTRODUCTIONIn centrally heated or cooled buildings, fresh air or “makeup air” is typically added continuously to the total volume of circulated air, resulting in some previously heated or cooled air being exhausted from the building space. This can result in an undesirable loss of energy and humidity from the building. Heat exchangers are commonly used in the exhaust air and makeup airflow paths of these systems to recover some of the energy from the exhaust air and to induce warmer makeup air during heating processes and cooler makeup air during cooling processes.
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 significant 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 effectively 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. The nature of moisture exchange requires a very large surface area in contact with the gas stream, and, consequently, so-called total heat exchangers are often very large in size when compared to heat-only exchangers. A larger exchanger in the conventional locations 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. With respect to 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.
U.S. Pat. No. 6,178,966 to Breshears addressed the shortcomings described above by describing an improved apparatus for enabling heat and moisture exchange between makeup and exhaust air streams in the heating and air conditioning system of a structure. The apparatus included a rigid frame for holding a pair of light transmitting panes, the frame and panes collectively defining an interior cavity within the apparatus. The apparatus could be integrated into the exterior walls of a building. The light transmitting properties of the panes allow incident solar radiation to permeate the panels, creating a more natural ambient environment in the interior of the structure adjacent with the panel, as well as raising the temperature of the air stream and the water vapor permeable barrier to further enhance the exchange of moisture through the barrier.
In the prior art Breshears apparatus, a water-vapor-permeable barrier was provided within the apparatus, to divide the interior of the apparatus into sub-channels for receiving makeup and exhaust air streams, respectively. The barrier was described as a composite film made of porous polymeric membrane having applied thereto a water-vapor-permeable polymeric material so as to form a non-porous barrier to block the flow of air and other gas.
Despite overcoming some of the shortcomings of preexisting systems, the prior art Breshears apparatus was limited in some ways. For example, the disclosed apparatus was limited to transparent structures configured to be integrated into the exterior of a building. Furthermore, the polymeric membranes described by Breshears were limited to certain particular membrane materials.
The present teachings relate to improved methods and apparatus for recovering energy and/or moisture as air is added to and exhausted from an enclosed space. These teachings may be combined, optionally, with apparatus, methods, or components thereof described in U.S. Pat. No. 6,178,966 to Breshears. However, the present teachings expand upon the prior art teachings by disclosing novel improvements such as an exchanger incorporated into an opaque exterior building element. These and other aspects of the present teachings are described in detail in the sections below.
This description discusses some of the basic features of heat and moisture exchangers according to aspects of the present teachings, and focuses particularly on incorporating exchangers into various external building elements, such as walls, foundations, roofs, and slab floors configured to divide an enclosed space from the ambient exterior and collectively referred to as a building enclosure system. See
In the embodiment of
Barrier 18, which divides interior channel 16 into sub-channels 20 and 22, is generally permeable to water vapor and substantially impermeable to the constituent gases of air, which principally include nitrogen and oxygen. Various types of barriers may be suitable for use with the present teachings, including microporous polymeric membranes with appropriate characteristics. One particularly suitable type of polymeric membrane is described in U.S. Patent Publication No. 2007/0151447 to Merkel, which is hereby incorporated by reference into the present disclosure for all purposes.
In a manner described in more detail below, source and exhaust gas streams, respectively denoted throughout the drawings as gas stream A and gas stream B, are directed through adjacent sub-channels 20 and 22 within exchanger 10. Due to the proximity of the air streams, heat may be conducted from the hotter gas stream through barrier 18 and into the cooler gas stream, and moisture may be transported from the gas stream of higher moisture content through barrier 18 and into the gas stream of lower moisture content. Various barrier configurations and resulting geometries of sub-channels may be chosen depending on the desired heat transfer, moisture transfer, and pressure drop characteristics. The following paragraphs include descriptions of various such arrangements, with barriers and sub-channels that function in a manner similar to those described above.
Similar arrangements having odd numbers of barriers with corresponding even numbers of sub-channels are possible, such as disposing five barriers within channel 86 to form six sub-channels evenly divided between gas stream A and gas stream B. Alternatively, some examples may have any number of barriers forming any corresponding number of sub-channels, divided unevenly between gas streams A and B. For example, four barriers may be used to form five sub-channels, with three devoted to gas stream A and two to gas stream B. In yet other examples, the barrier arrangements of exchangers 40 and 80 may be combined to produce parallel pleated or corrugated barriers, or even alternating corrugated and flat barriers, in any case forming sub-channels with corresponding shapes.
For example,
More specifically, The following description discusses some of the basic methods of configuration and integration of the heat and moisture exchangers into elements of the building according to the present teachings. See
The subsequent description also contemplates a heat and moisture exchanger for integration into a portion of the building enclosure. In this example certain portions of the exchanger may be transparent to various spectra of radiation, resulting in transfers of radiant energy between elements of the exchanger system. In this embodiment, the transmissivity of the radiation-transmitting elements and the geometry of the radiation-absorbing objects may be configured to control the fraction of heat- or light-energy incident on the exchanger housing that is transmitted through the exchanger to the building interior. The absorptivity and emissivity properties of the material from which the elements are made may be determined and selected to enhance the transmission of radiation within the desired spectra and simultaneously to maximize the absorption of radiation outside the desired spectra. These teachings expand upon the prior art teachings to address shortcomings by disclosing a radiation-energy transferring exchanger in which the energy-absorbing objects may be of various geometries and materials and may be configured within one gas stream or the other in order to best exploit the absorbed energy that is re-emitted as heat via convection into that gas stream.
In the embodiment of
Barrier 324, which divides interior channel 16 into sub-channels 20 and 22, is generally permeable to water vapor and substantially impermeable to the constituent gases of air, which principally include nitrogen and oxygen. Various types of barriers may be suitable for use with the present teachings, including microporous polymeric membranes with appropriate characteristics. One particularly suitable type of polymeric membrane is described in U.S. Patent Publication No. 2007/0151447 to Merkel, which is hereby incorporated by reference into the present disclosure for all purposes.
In the configuration represented in
The present teachings relate to improved methods and apparatus for recovering energy and/or moisture as air is added to and exhausted from an enclosed space. The heat and moisture exchangers described in the present teachings may induce some change in temperature and humidity of incoming ventilation air as it passes through the exchanger by transfer to an outgoing air stream also passing though the exchanger. In cases where further alteration of the temperature or humidity of the incoming air stream is desired beyond what is induced by the exchanger, the exchanger may be interconnected and configured to operate with a separate apparatus or device providing additional heating, cooling, dehumidification or humidification to the airstream. This heating, ventilating and air conditioning device (which may be referred to herein as simply “HVAC”) may be an apparatus of various types or functions. An incoming gas stream, designated as A, is directed through the heat and moisture exchanger and at some point on its path of travel may also be processed by the HVAC in order to alter its temperature and/or humidity. An outgoing gas stream, designated as B, may be directed from the interior space to the exterior by passing through the heat and moisture exchanger. The descriptions that follow relate to methods in which a system of heat and moisture exchangers and HVAC devices may be configured to alter the temperature and humidity of an air stream as it is added to an enclosed space. See
An enclosed space 410 is depicted in
An enclosed space 410 is depicted in
In
The disclosure set forth herein encompasses multiple distinct inventions with independent utility. While each of these inventions has been disclosed in its preferred form, the specific embodiments thereof as disclosed and illustrated herein are not to be considered in a limiting sense as numerous variations are possible. Each example defines an embodiment disclosed in the foregoing disclosure, but any one example does not necessarily encompass all features or combinations that may be eventually claimed. Where the description recites “a” or “a first” element or the equivalent thereof, such description includes one or more such elements, neither requiring nor excluding two or more such elements. Further, ordinal indicators, such as first, second or third, for identified elements are used to distinguish between the elements, and do not indicate a required or limited number of such elements, and do not indicate a particular position or order of such elements unless otherwise specifically stated.
Claims
1. An apparatus for enabling heat and moisture exchange, comprising:
- an exchanger housing including an exterior wall defining a channel through which a gas stream may pass;
- a barrier, permeable to water vapor and substantially impermeable to oxygen and nitrogen, disposed within the interior channel and partitioning the interior channel into a plurality of separate sub-channels;
- wherein a first of the sub-channels is adapted to receive a first gas stream at the same time a second of the sub-channels is adapted to receive a second gas stream; and
- wherein at least a portion of the exterior wall forms a substantially opaque portion of a building enclosure system.
2. The apparatus of claim 1, wherein at least a portion of the exterior wall of the exchanger housing forms a portion of a wall of the building enclosure system.
3. The apparatus of claim 1, wherein at least a portion of the exterior wall of the exchanger housing forms a portion of a roof of the building enclosure system.
4. The apparatus of claim 1, wherein at least a portion of the exterior wall of the exchanger housing forms a portion of a floor of the building enclosure system.
5. The apparatus of claim 1, wherein at least a portion of the exterior wall of the exchanger housing forms a portion of a foundation of the building enclosure system.
6. The apparatus of claim 1, further comprising a layer of insulation disposed adjacent to at least a portion of the exterior wall of the exchanger housing.
7. The apparatus of claim 1, wherein at least a portion of the exterior wall of the exchanger housing is exposed to outdoor environmental conditions and wherein the exposed portion is constructed from a weather-resistant material.
8. The apparatus of claim 7, wherein a first portion of the exterior wall of the exchanger housing is exposed to outdoor environmental conditions and a second portion of the exterior wall of the exchanger housing is exposed to a building interior.
9. The apparatus of claim 7, wherein the exposed portion of the exterior wall of the exchanger housing forms a portion of an outermost layer of a rain screen enclosure system.
10. The apparatus of claim 9, further including a weather-resistant layer separate from the exchanger housing, wherein the exposed portion of the exterior wall of the exchanger housing and the weather resistant layer form a continuous layer configured to prevent ingress of water into a building.
11. An apparatus for enabling heat and moisture exchange, comprising:
- an exchanger housing defining an interior channel;
- a membrane disposed within the housing and dividing the interior channel into a first sub-channel through which a source gas stream may pass and a second sub-channel through which an exhaust gas stream may simultaneously pass;
- wherein the membrane is permeable to water vapor and substantially impermeable to constituent gases of air; and
- wherein at least a portion of the exchanger housing forms a substantially opaque portion of a building enclosure system.
12. The apparatus of claim 11, wherein a portion of the exchanger housing forms an interior wall portion of the building enclosure system.
13. The apparatus of claim 11, wherein a portion of the exchanger housing forms an exterior wall portion of the building enclosure system.
14. The apparatus of claim 13, wherein the exterior wall portion is exposed to outdoor environmental conditions and is constructed from a weather-resistant material.
15. The apparatus of claim 11, wherein a first portion of the exchanger housing forms an interior wall portion of the building enclosure system, and a second portion of the exchanger housing forms an exterior wall portion of the building enclosure system.
16. The apparatus of claim 11, wherein a portion of the exchanger housing forms a roof portion of the building enclosure system.
17. The apparatus of claim 11, wherein a portion of the exchanger housing forms a floor portion of the building enclosure system.
18. The apparatus of claim 11, wherein a portion of the exchanger housing forms a foundation portion of the building enclosure system.
19. The apparatus of claim 11, further comprising a layer of insulation disposed adjacent to at least a portion of the exchanger housing.
20. A heat and moisture exchanger system, comprising:
- a rain screen layer attached to a building and defining a gap between the rain screen layer and an exterior wall of the building;
- an exchanger forming a portion of the rain screen layer and also passing through the exterior wall to an interior of the building; and
- a membrane dividing an interior channel of the exchanger into a plurality of sub-channels, the membrane configured to allow passage of water vapor and to prevent substantial passage of air;
- wherein the exchanger is configured (a) to allow passage of a source air stream from outside the building, through one of the sub-channels, to inside the building, (b) to allow passage of an exhaust air stream from inside the building, through another of the sub-channels, to outside the building, and (c) to transfer heat and moisture through the membrane between the exhaust air stream and the source air stream.
Type: Application
Filed: Jan 22, 2013
Publication Date: May 23, 2013
Applicant: ARCHITECTURAL APPLICATIONS P.C. (Portland, OR)
Inventor: ARCHITECTURAL APPLICATIONS P.C. (Portland, OR)
Application Number: 13/747,218
International Classification: F24F 3/147 (20060101);