Patent Application
20170219227
Embodiments according to the present disclosure generally relate to air conditioning and, more specifically, to an indirect evaporative air conditioning system incorporating dehumidification.
Direct evaporative coolers, employing the thermodynamic principle of adiabatic saturation, are well-known in the art. Air to be cooled is saturated with an evaporative liquid (e.g., a water mist), whose evaporation from the liquid state (mist) to vapor state takes up available (latent) heat energy from the air itself, thereby lowering its temperature. The ambient air may be cooled in the limit to its wet bulb temperature using direct evaporative cooling, the wet bulb temperature also being known as the adiabatic saturation temperature. A problem with direct evaporative cooling is the introduction of humidity into the cooled environmental space, making this method of cooling unsuitable for sustained cooling of a confined habitable space because continuous humidification of the air causes discomfort to occupants.
A different method of cooling air is termed indirect evaporative cooling, which functions by evaporating a cooling liquid, usually water, into a first air stream while transferring heat from a second air stream to the first air stream. Conventional indirect evaporative coolers have traditionally been more expensive than their evaporative counterparts. In particular, inefficiencies in the transfer of heat from the second air stream to the first air stream in conventional systems prevent sufficient cooling of air at a similar cost to evaporative coolers. These inefficiencies can be the result of a poor water supply system and/or expensive heat exchanger materials, air flow pressure issues, a large number of components that are auxiliary to the indirection evaporative cooling system, etc.
This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.
An embodiment of the present disclosure includes incremental dehumidification of a volume of air in an indirect evaporative cooler. Dehumidification processes are incorporated with the cooling processes, such that within each circuit a volume of air follows through the indirect evaporative cooler and includes dehumidification as well as cooling of the volume of air. Subsequent circuits of the volume of air, which commence at a lower starting temperature than the prior circuit, result in further dehumidification of the air.
More specifically, an aspect of the present disclosure provides an indirect evaporative cooler apparatus including: a heat exchanger comprising a dry passage and a wet passage, the dry passage in thermodynamic communication with the wet passage and separated from the wet passage by a substantially liquid-impermeable membrane having a hydrophobic surface facing the dry passage and a hydrophilic surface facing the wet passage, the dry passage comprising an intake portion, an outlet portion, and a loop portion; a mixing valve disposed in the dry passage and configured to selectively pass intake air from the intake portion, recirculation air from the loop portion, or a combination thereof; a first fan disposed downstream of the mixing valve and adapted to move a first volume of air into and through the loop portion; a diverting valve disposed in the dry passage and configured to selectively pass outlet air to the outlet portion, recirculation air to the mixing valve, or a combination thereof; and a controller adapted to operate the mixing valve, the first fan, the diverting valve, and a combination thereof, for cooling the first volume substantially to its dew point, and for incrementally further cooling and dehumidifying the first volume of air.
In an embodiment the indirect evaporative cooler apparatus further includes a water source having a pressure valve associated therewith, and a nozzle configured to wet the wet passage for evaporative cooling of the substantially liquid-impermeable membrane. In a further embodiment the water enclosure is pressurized by the pressure valve to a threshold level such that positive pressure is maintained sufficient for the nozzle to dispense water. In an embodiment the apparatus further includes a second fan and an enclosure valve associated therewith configured to develop a negative pressure relative to ambient pressure within the wet passage. In an embodiment the dry passage is arranged in a descending serpentine configuration, and further wherein the intake portion is disposed at a top portion of the descending serpentine configuration, and the outlet is disposed at a bottom portion of the descending serpentine configuration. In a further embodiment the dry passage has a hexagonal cross-section. In an embodiment the apparatus further includes a dry passage water nozzle configured to expel accumulated water from dehumidification of the first volume of air. In a further embodiment the dry passage is maintained at a positive pressure relative to ambient pressure. In an embodiment the apparatus includes air traps disposed within the dry passage. In an embodiment the apparatus includes a heat exchange coil disposed within the dry passage.
According to another aspect of the present disclosure, a method of incrementally dehumidifying air in an indirect evaporative air conditioner includes: having a heat exchanger comprising a dry passage and a wet passage, the dry passage in thermodynamic communication with the wet passage and separated from the wet passage by a substantially liquid-impermeable membrane having a hydrophobic surface facing the dry passage and a hydrophilic surface facing the wet passage, the dry passage comprising an intake portion, an outlet portion, and a loop portion; selectively passing intake air from the intake portion, recirculation air from the loop portion, or a combination thereof by a mixing valve disposed in the dry passage; moving air into and through the loop portion by a first fan disposed downstream of the mixing valve; selectively passing outlet air to the outlet portion, recirculation air to the mixing valve, or a combination thereof by a controller adapted to operate a diverting valve disposed in the dry passage; and cooling the first volume of air substantially to its dew point, and incrementally further cooling and dehumidifying the first volume of air by the controller operating the mixing valve, the first fan, the diverting valve, and a combination thereof.
In an embodiment the method further includes wetting the wet passage by a water source having an associated pressure valve and a nozzle, for evaporative cooling of the substantially liquid-impermeable membrane. In a further embodiment the method includes pressurizing the water enclosure by the pressure valve to a threshold level such that positive pressure is maintained sufficient for the nozzle to dispense water. In an embodiment the method further includes developing a negative pressure relative to ambient pressure within the wet passage, by a second fan and an enclosure valve associated therewith. In an embodiment the dry passage is arranged in a descending serpentine configuration, and further the intake portion is disposed at a top portion of the descending serpentine configuration, and the outlet is disposed at a bottom portion of the descending serpentine configuration. In a further embodiment the dry passage has a hexagonal cross-section. In an embodiment the method further includes expelling accumulated water from dehumidification of the first volume of air by a dry passage water nozzle. In an embodiment the method further includes maintaining the dry passage at a positive pressure relative to ambient pressure. In an embodiment the method further includes air traps disposed within the dry passage. In an embodiment the method further includes a heat exchange coil disposed within the dry passage.
According to an aspect of the present disclosure, a system for incrementally dehumidifying air includes: an evaporative liquid reservoir comprising a pressure valve and a channel adapted to transport evaporative liquid; a heat exchanger comprising: a dry passage and a wet passage, the dry passage in thermodynamic communication with the wet passage and separated from the wet passage by a substantially liquid-impermeable membrane having a hydrophobic surface facing the dry passage and a hydrophilic surface facing the wet passage, the dry passage comprising an intake portion, an outlet portion, and a loop portion; a nozzle coupled with the channel and configured to wet the wet passage for evaporative cooling of the substantially liquid-impermeable membrane; a mixing valve disposed in the dry passage and configured to selectively pass intake air from the intake portion, recirculation air from the loop portion, or a combination thereof; and a diverting valve disposed in the dry passage and configured to selectively pass outlet air to the outlet portion, recirculation air to the mixing valve, or a combination thereof; and a controller adapted to operate the pressure valve, the mixing valve, the diverting valve, and a combination thereof, for cooling a first volume of air substantially to its dew point, and for incrementally further cooling and dehumidifying the first volume of air.
In an embodiment the evaporative liquid reservoir is pressurized by the pressure valve to a threshold level such that positive pressure is maintained sufficient for the nozzle to dispense evaporative liquid onto the wet liquid-impermeable membrane. In an embodiment the heat exchanger further comprises a fan and an enclosure valve associated therewith configured to develop a negative pressure relative to ambient pressure within the wet passage. In an embodiment the dry passage is arranged in a descending serpentine configuration, and further wherein the intake portion is disposed at a top portion of the descending serpentine configuration, and the outlet is disposed at a bottom portion of the descending serpentine configuration. In an embodiment the dry passage has a hexagonal cross-section. In an embodiment the system further includes air traps disposed within the dry passage. In an embodiment the system further includes a heat exchange coil disposed within the dry passage. In an embodiment the system further includes a dry passage water nozzle disposed in the dry passage and configured to expel accumulated water from dehumidification of the first volume of air. In an embodiment the dry passage is maintained at a positive pressure relative to ambient pressure.
Embodiments of the present disclosure are illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings and in which like reference numerals refer to similar elements.
Reference will now be made in detail to the various embodiments of the present disclosure, examples of which are illustrated in the accompanying drawings. While described in conjunction with these embodiments, it will be understood that they are not intended to limit the disclosure to these embodiments. On the contrary, the disclosure is intended to cover alternatives, modifications and equivalents, which may be included within the spirit and scope of the disclosure as defined by the appended claims. Furthermore, in the following detailed description of the present disclosure, numerous specific details are set forth in order to provide a thorough understanding of the present disclosure. However, it will be understood that the present disclosure may be practiced without these specific details. In other instances, well-known methods, procedures, components, and circuits have not been described in detail so as not to unnecessarily obscure aspects of the present disclosure.
Some portions of the detailed description that follows are presented in terms of procedures, steps, logic blocks, processing, and other symbolic representations of operations on data bits that can be performed on computer memory. These descriptions and representations are the means used by those skilled in the data processing arts to most effectively convey the substance of their work to others skilled in the art. A procedure, computer generated step, logic block, process, etc., is here, and generally, conceived to be a self-consistent sequence of steps or instructions leading to a desired result. The steps are those requiring physical manipulations of physical quantities. Usually, though not necessarily, these quantities take the form of electrical or magnetic signals capable of being stored, transferred, combined, compared, and otherwise manipulated in a computer system. It has proven convenient at times, principally for reasons of common usage, to refer to these signals as bits, values, elements, symbols, characters, terms, numbers, or the like.
It should be borne in mind, however, that all of these and similar terms are to be associated with the appropriate physical quantities and are merely convenient labels applied to these quantities. Unless specifically stated otherwise as apparent from the following discussions, it is appreciated that throughout the present claimed subject matter, discussions utilizing terms such as “storing,” “creating,” “protecting,” “receiving,” “encrypting,” “decrypting,” “destroying,” or the like, refer to the action and processes of a computer system or integrated circuit, or similar electronic computing device, including an embedded system, that manipulates and transforms data represented as physical (electronic) quantities within the computer system's registers and memories into other data similarly represented as physical quantities within the computer system memories or registers or other such information storage, transmission or display devices.
In one embodiment of the present disclosure, an indirect evaporative cooler apparatus is able to cycle air dynamically through one or more dry passages of the indirect evaporative cooler, for cooling and/or dehumidification of a volume of air. Indirect evaporative cooling describes cooling in which an airstream is first cooled by adiabatic saturation, and then used to cool a separate, non-mixing airstream across a heat-transfer partition (e.g., an airstream of a wet passage is in thermodynamic communication with an airstream of a dry passage). The latter airstream is said to be sensibly cooled; that is, cooled without altering its absolute moisture content.
Referring now to
According to an embodiment, one or more nozzles 130 (e.g., a layer nozzle) are disposed above the one or more wet passages, the nozzles 130 configured to dispense water (or other suitable liquid) for wetting a surface of wet passage for evaporative cooling. According to an embodiment one or more dry passage nozzles 140 are disposed within the one or more dry passages, and are configured to expel water from within the dry passage. The water may accumulate, for example, via condensation from a dehumidifying function of the indirect evaporative cooling apparatus 100. The nozzle 140 can be disposed to expel the condensed water onto a surface of a wet passage located below the nozzle 140. Alternatively, the nozzle 140 can be disposed to expel the condensed water to be collected in a water reservoir, for example an external reservoir 145 and/or an internal water reservoir 165. While not shown, indirect evaporative cooling apparatus 100 can include one or more barometers, hygrometers (humidity sensors), and thermometers, that are operable to measure their respective environmental conditions in the dry and/or wet passages, and to report corresponding values to controller 103.
According to an embodiment, an external reservoir 145 supplies an evaporative liquid to nozzles 130 for wetting of wet passages of the indirect evaporative cooling apparatus 100. The evaporative liquid can be water, for example, although other liquids suitable for evaporative cooling in wet passages of the indirect evaporative apparatus 100 can be used, as is appreciated by those of skill in the art. The external reservoir 145 can have an associated pressure valve 150, along with a supply pipe 155 and a supply pump 160. According to embodiments of the present disclosure, a supply pressure of nozzles 130 is set by pressure valve 150, controlled by controller 103. According to an embodiment, indirect evaporative cooling apparatus 100 includes a manifold 180 arranged to house one or more nozzles 130 and to dispense evaporative liquid over the one or more wet passages. According to an embodiment, an optional internal water reservoir 165 is located to accumulate from nozzles 130 and/or condensed water from nozzles 140. The internal water reservoir can include an associated supply pipe 170 and pump 175 to provide accumulated water for dispensing from nozzles 130 (e.g., via optional manifold 180).
As depicted in
According to some embodiments of the present disclosure, some portions of the dry passage include one or more elements to induce a pressure differential within the dry passage (e.g., air traps 190 or a heat exchange coil, not shown). Additionally or alternatively, indirect evaporative cooling apparatus 100 can include an exhaust pipe (not shown) having an associated exhaust valve (not shown) and exhaust fan (not shown), disposed on an enclosure of apparatus 100 and operable to develop a negative pressure differential in the one or more wet passages relative to ambient pressure. These features, as well as other characteristics of the indirect evaporative cooling apparatus of the present disclosure, can be better appreciated by a description of the internal components and functions of the indirect evaporative cooling apparatus herein.
Referring now to
Referring now to
Once the volume of air substantially reaches its dew point (based on the specific humidity of the air upon intake at intake portion 105), further cooling of the now-saturated air (100% relative humidity) causes condensation of water from the volume of air. This is represented by the transition from locations B and C on the psychrometric graph. At location C the volume of air has been both cooled from its initial temperature at location A, and dehumidified from its initial specific humidity (locations A and B). The transition from locations B and C on the psychrometric graph can correspond to a further number of circuits of the volume of air through the loop portion of a dry passage, where each circuit leads to further cooling and dehumidification of the volume of air. This may be termed incremental cooling and/or dehumidification. By incremental it is meant incorporating the dehumidification processes and the cooling process, e.g., each cooling cycle the volume of air is dehumidified as well as cooled. In this manner the volume of air, as it circulates in the dry passage of the indirect evaporative cooling apparatus, is cooled and dehumidified bit by bit, each cycle (e.g., circuit of air through a dry passage) resetting the starting conditions of the volume of air. According to an embodiment of the present disclosure, condensed water is removed from the dry passage during this incremental cooling and dehumidification process, as described herein.
Referring now to
Controls module 410 is configured to send control signals to components of indirect evaporative cooling apparatus determined, from environmental conditions of the indirect evaporative cooling apparatus. Components of the indirect evaporative cooling apparatus that are controlled by controls module 410 include mixing valve 110 and intake fan 135, diverting valve 125, optional fan 185, and optional exhaust valve and fan. Controls module 410 can also control operation of reservoir valve 150, pump 160, and optional internal reservoir pump 175, along with any other electromechanical components included in the indirect evaporative cooling apparatus of the present disclosure.
Output module 420 delivers control signals to the components of the indirect evaporative cooling apparatus according to the operations determined by controls module 410. Exemplary operations include: single cycle operation; dynamic cycle operation; high pressure operation; low pressure operation; and water operation.
In single cycle operation a volume of air is controlled to move once through the dry passage(s) of the indirect evaporative cooling apparatus, which may be accomplished by opening mixing valve 110 to air from intake portion 105, and diverting valve 125 to outlet portion 120 only—that is, not mixing the volume of air through loop portion 115. Fan 135 (and/or optional fan 185) can be operated to enhance the movement of the volume of air through the dry passage(s).
In dynamic cycle operation initially mixing valve 110 is opened to air from intake portion 105, and then mixing valve 110 is closed to intake portion 105 in order to introduce a first volume of air to dry passage(s). Movement of the first volume of air through the dry passage(s) can be enhanced by operation of fan 135 and/or optional fan 185. Diverting valve 125 is controlled to close air movement to outlet portion 120, and to re-circulate the first volume of air through loop portion 115. In this manner the first volume of air can be made to circulate through the dry passage(s) a number of times, and to be continuously cooled via indirect evaporative cooling. According to embodiments of the present disclosure, dynamic cycling of a volume of air through the indirect evaporative cooling apparatus is used to dehumidify the volume of air, as well as to cool, as is described further herein below.
In high pressure operation mixing valve 110 is opened to air from intake portion 105 and diverting valve 125 is closed to outlet portion 120—that is, the volume is air is not expelled from the indirect evaporative cooling apparatus. Fan 135 (and/or optional fan 185) can be operated to enhance the movement of the volume of air into the dry passage(s). In an embodiment, diverting valve 125 is closed so that the volume of air is not diverted to loop portion 115. In an embodiment, diverting valve 125 is open to loop portion 115 (but closed to outlet portion 120), such that air is re-circulated through the dry passage(s) (e.g., for pressurization and cooling of the volume of air in the dry passage).
In low pressure operation the wet passage(s) of the indirect evaporative cooling apparatus develop of a lower pressure, with respect to the ambient pressure and/or the pressure in dry passage(s). A lower pressure in the wet passage(s) encourages evaporation of liquid at surfaces of the wet passage(s), enhancing the indirect cooling effect. According to an embodiment of the present disclosure, the indirect evaporative cooling apparatus includes an exhaust fan and valve in an enclosure. The exhaust fan and valve can be operated by controller 103 to force air out of wet passage(s) of the indirect evaporative cooling apparatus, and to thereby develop a low pressure in the wet passage(s) (e.g., a negative pressure with respect to ambient and/or dry passage pressure).
In water operation the components of the external reservoir 145 and of optional internal water reservoir 165 are controlled to store and distribute liquid for evaporative cooling of wet passages of the indirect evaporative cooling apparatus. Output module 420 can signal reservoir valve 150 to open or close, and pump 160 to operate to move liquid to external reservoir 145. In some embodiments pump 160 is operated to pressurize external reservoir 145, in order to increase a water pressure and/or a rate at which wet passage water nozzles dispense water. In an embodiment output module 420 signals optional internal reservoir pump 175 to close in order to retain accumulated water. In an embodiment output module 420 signals optional internal reservoir pump 175 to pump water up to be dispensed over wet passages, for example via optional manifold 180. In an embodiment valve 150 is signaled to open in order to return accumulated water in internal reservoir 165 to external reservoir 145. Valve 150 operation can be determined from one or more of: dry passage and/or wet passage temperature; temperature of water in internal reservoir 165 and/or external reservoir 145; a water level of internal reservoir 165 and/or external reservoir 145.
According to some embodiments of the present disclosure, for air stream detected to be substantially on its dew point, dehumidification of the air stream can be accomplished via pressure differentials within regions of the indirect evaporative cooling apparatus 100. According to some embodiments of the present disclosure, some portions of the dry passage include one or more elements to induce a pressure differential within the dry passage, for example air traps 190 and/or a heat exchange coil (not shown). Air traps 190 are disposed on one or more surfaces of the dry passage(s), and function to cause regions of increased pressure within an airstream moving through the dry passage. A higher pressure within a saturated, or nearly saturated, airstream is able to cause condensation of water from the airstream (e.g., dehumidification). Additionally or alternatively, an indirect evaporative cooling apparatus of the present disclosure can include an exhaust pipe (not shown) having an associated exhaust valve (not shown) and exhaust fan (not shown), disposed on an enclosure of apparatus and operable to develop a negative pressure differential in the one or more wet passages relative to ambient pressure. A reduced pressure in a wet passage of the indirect evaporative cooling apparatus is able to increase an evaporation of a liquid wetting a surface of the wet passage, and thereby to increase cooling of the airstream in the adjacent dry passage.
Step 503 includes determining a relative humidity of the first volume of air. The relative humidity can be determined based on a barometric pressure and/or a temperature in the dry passage. According to an embodiment, the indirect evaporative cooling apparatus can determine the barometric pressure and/or the temperature from an included one or more barometers, hygrometers (humidity sensors), and thermometers, that are operable to measure their respective environmental conditions in the dry and/or wet passages, and to report corresponding values to a controller (e.g., controller 103 of
Step 505 includes selectively generating a pressure differential in the heat exchanger upon the first volume of air determined to be substantially at its dew point, by increasing barometric pressure in the dry passage, decreasing barometric pressure in the wet passage, or a combination thereof, sufficient to condense water from the first volume of air. The selective pressure differential generation can be accomplished using a controller 103 running an air conditioning application 400, for example by performing a high pressure operation, a low pressure operation, or a combination of these as described herein.
According to an embodiment of the present disclosure water condensed from a dehumidification process of a volume of air moving through an indirect evaporative cooler can be captured and/or recycled for use in subsequent wetting of one or more wet passages of the indirect evaporative cooler. In this manner water is conserved from the incoming air stream, which, as it cools in a dry passage, approaches its dew point and then commences condensation of water contained in the air stream. This condensed water can gather on a surface of a dry passage (e.g., hydrophobic surface of a dry passage 203), and can be expelled from the dry passage. One means of expelling condensed water is by a water nozzle (e.g., water nozzle 240). The removal of condensed water from a dry passage can be aided by increasing the pressure within the dry passage, with respect to ambient pressure (and/or with respect to the wet passage).
According to an embodiment of the present disclosure an indirect evaporative cooling apparatus (e.g., apparatus 100) includes an internal water reservoir (e.g., reservoir 265), which is configured to receive water from wet passage nozzles and/or dry passage nozzles. Alternatively or additionally, captured water can be returned to an external liquid reservoir (e.g., reservoir 145). The collected water can be recycled, that is, used again to dispense water over wet passages 210 via nozzles 230 for evaporative cooling of membrane 215 (and induced cooling of a volume of air traveling through dry passages 203).
The foregoing description, for purpose of explanation, has been described with reference to specific embodiments. However, the illustrative discussions above are not intended to be exhaustive or to limit the invention to the precise forms disclosed. Many modifications and variations are possible in view of the above teachings. The embodiments were chosen and described in order to best explain the principles of the invention and its practical applications, to thereby enable others skilled in the art to best utilize the invention and various embodiments with various modifications as may be suited to the particular use contemplated.
Embodiments according to the invention are thus described. While the present disclosure has been described in particular embodiments, it should be appreciated that the invention should not be construed as limited by such embodiments, but rather construed according to the below claims.
