AIR CONDITIONING SYSTEM AND CONTROL METHOD

Abstract

A cooling and dehumidification system including at least one passive heat transfer device with desiccant coated on some extent of the exposed surface, another passive heat transfer device without desiccant coating, a compressor through which refrigerant flows, an expansion device, a refrigerant control valve, and valves to direct airflow in relation to the passive heat transfer devices.

Description

RELATED APPLICATION

This application claims the benefit of co-pending U.S. Provisional Application Ser. No. 63/184,070, entitled AIR CONDITIONING SYSTEM AND CONTROL METHOD, filed May 4, 2021, the teaching of which are expressly incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to system and method to provide cooling and dehumidification to a space.

BACKGROUND OF THE INVENTION

The rising demand for cooling is putting an enormous strain on the environment, grid infrastructure, and the global climate. Meeting the world's demand for cooling while minimizing its negative impacts will be one of the defining challenges of our time. This challenge can be addressed by redesigning today's air conditioning systems to take advantage of new materials and chemical processes.

Conventional vapor-compression based air conditioning systems provide cooling and dehumidification by passing air over a cooling coil. The coil is maintained at a lower temperature than the air by the flow of refrigerant through the coil. Sensible cooling is achieved by passing air over a cooling coil which is cooler than the entering air, resulting in heat transfer from the air to the refrigerant and reducing the temperature of the air. Latent cooling, or dehumidification, is achieved by passing air over a cooling coil which is below the dewpoint of the entering air. This results in moisture from the air forming condensate on the coil surface and transferring the latent heat of vaporization to the refrigerant. In such systems, sensible and latent heat removal are coupled such that either sensible or latent cooling can be controlled, but not both. Furthermore, to meet high latent loads the cooling coil must operate at very low temperatures, resulting in poor efficiency of the vapor compression system.

SUMMARY OF THE INVENTION

The present disclosure overcomes the disadvantages of the prior art by providing a cooling and dehumidification system, comprising: at least one passive heat transfer device with desiccant coated on some extent of the exposed surface, another passive heat transfer device without desiccant coating, a compressor through which refrigerant flows, an expansion device, a refrigerant control valve, and valves to direct airflow in relation to the passive heat transfer devices.

In and illustrative embodiment, An air-handling system and method comprises a heat pump configured to move heat energy between a plurality of passive heat transfer devices. The plurality of passive heat transfer devices, define a first surface of at least one of the plurality of passive heat transfer devices that is thermally in contact with the heat pump, and a second surface of at least one of the plurality of passive heat transfer devices that is exposed to allow the transfer of heat to or from the heat pump. A desiccant can be in thermal contact with the exposed surface of at least one passive heat transfer device and configured to exchange moisture with air. A plurality of air directing valves are configured to direct process and regeneration air to and from the plurality of passive heat transfer devices with desiccant. A heat pump reversing device can be configured to change the direction of heat flow in the heat pump between two modes of operation, and a control system with communication lines can control air directing valves, reversing device, and heat pump operation. A control operation process can operate a control mode in which desiccant regeneration time is modulated. Illustratively, the passive heat transfer devices can comprise tube and fin heat exchangers or microchannel heat exchangers. The desiccant can form a coating on the exposed surface of the heat exchanger fins, which can be a partial coating with an uncoated section first exposed to airflow followed by a desiccant coated second section exposed to airflow. A passive heat transfer device without desiccant can be configured for exchanging sensible heat with ambient air, and/or the passive heat transfer device without desiccant can be configured for exchanging sensible heat with indoor air. The desiccant can comprise any acceptable material, or combination of materials, including at least one of silica gel, alumina, zeolite or a metal-organic framework (MOF) material.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention description below refers to the accompanying drawings, of which:

FIG. 1A depicts a cooling and dehumidification system with two desiccant coated passive heat transfer devices and a third uncoated passive heat transfer device in a first mode of operation.

FIG. 1B depicts a cooling and dehumidification system with two desiccant coated passive heat transfer devices and a third uncoated passive heat transfer device in a second mode of operation.

FIG. 2A depicts a cooling and dehumidification system with two desiccant coated passive heat transfer devices and a third uncoated passive heat transfer device in a first mode of operation.

FIG. 2B depicts a cooling and dehumidification system with two desiccant coated passive heat transfer devices and a third uncoated passive heat transfer device in a second mode of operation.

FIG. 3A depicts a cooling and dehumidification system with one desiccant coated passive heat transfer device and two uncoated passive heat transfer devices in a first mode of operation.

FIG. 3B depicts a cooling and dehumidification system with one desiccant coated passive heat transfer device and two uncoated passive heat transfer devices in a second mode of operation.

FIG. 4A depicts a cooling and dehumidification system with two desiccant coated passive heat transfer devices in a first mode of operation.

FIG. 4B depicts a cooling and dehumidification system with two desiccant coated passive heat transfer devices in a second mode of operation.

FIGS. 5A-5D depict embodiments of a refrigerant flow and metering device in two modes of operation.

FIG. 6A depicts a cross sectional view of an embodiment of an indoor cooling and dehumidifying device in a first mode of operation.

FIG. 6B depicts a cross sectional view of an embodiment of an indoor cooling and dehumidifying device in a second mode of operation.

FIG. 7 depicts a method of control for a desiccant cooling and dehumidification system.

DETAILED DESCRIPTION

FIGS. 1A and 1B show schematic views of an exemplary desiccant cooling and dehumidification system 100. In operation, system 100 cycles between two modes of operation: a first mode (also referred to as a first half-cycle), and a second mode (also referred to as a second half-cycle). FIG. 1A illustrates the first mode of operation and 1B illustrates the second mode of operation. System 100 includes a heat pump comprising compressor 103, uncoated (i.e., free of desiccant material) passive heat transfer device 104, refrigerant reversing valve 105, a first desiccant coated passive heat transfer device 107, expansion valve 108, and a second desiccant coated passive heat transfer device 109. System 100 further includes first air directing valve 113, second air directing valve 114, and first fan 115. System 100 further includes first air duct 119, third air directing valve 120, fourth air directing valve 121, second fan 122, and second air duct 123. System 100 further includes third fan 128.

As shown in the example of FIGS. 1A and 1B, compressor 103, uncoated passive heat transfer device 104, refrigerant reversing valve 105 and fan 128 are located outside of the conditioned space within one or more housing structures and form outdoor device 102. Desiccant coated passive heat transfer devices 107 and 109, air directing valves 113, 114, 120, and 121, fans 115 and 122, and expansion valve 108 are located inside the conditioned space in one or more housing structures and form indoor device 101. The indoor space and outdoor space are separated by dividing wall 125. Indoor device 101 and the outdoor device 102 are thermally connected through refrigerant lines 106 and 110 that pass through the dividing wall 125. Furthermore, indoor device 101 is physically connected to air ducts 113 and 118 which pass through dividing wall 125 to the outdoor space.

System 100 operates in a cyclic manner, alternating between two modes of operation, shown by FIGS. 1A and 1B. During the first half-cycle, desiccant coated passive heat transfer device 109 is in process mode and desiccant coated passive heat transfer device 107 is in regeneration mode. During the second half-cycle, the roles of desiccant coated passive heat transfer device 109 and desiccant coated passive heat transfer device 107 reverse such that desiccant coated passive heat transfer device 109 is in regeneration mode and desiccant coated passive heat transfer device 107 is in process mode.

By way of non-limiting example, the desiccant can comprise any appropriate material clear to those of skill, which is designed to capture moisture using a desiccant material such as a silica gel, alumina, zeolite or a metal-organic framework (MOF) material. The desiccant media comprising a plurality of desiccant structures can be manufactured/applied, based upon known techniques and equipment, for example, using a composite material that consists of the active desiccant powder embedded within a rigid binding material such as a ceramic or plastic that does not affect the desiccant material's ability to adsorb moisture. Such is applied to the heat exchanger using conventional coating or layering techniques, or is otherwise applied to, e.g. fins of the heat exchange element.

FIG. 1A shows the first half-cycle of operation of system 100. Low-pressure refrigerant at a first pressure state enters compressor 103 and is compressed to a second pressure state (e.g., high-pressure state) that is higher than the first pressure state. Refrigerant then flows through uncoated passive heat transfer device 104, releasing some heat to ambient airstream 126. Refrigerant then flows through refrigerant reversing valve 105 (configured in a first valve state) and is directed to refrigerant line 106. Refrigerant then flows through refrigerant line 106 from outdoor device 102 to indoor device 101. Refrigerant then flows through desiccant coated passive heat transfer device 107, releasing some heat to regeneration airstream 118. Refrigerant then flows through expansion valve 108 which takes the refrigerant from a high-pressure state to a low-pressure state. Refrigerant then flows through desiccant coated passive heat transfer device 109 absorbing some heat from process air 111. Refrigerant then flows through refrigerant line 110 from indoor device 101 to outdoor device 102. Refrigerant then flows through reversing valve 105 (in the first valve state) and back to compressor 103, completing the circuit.

Process air 111 to be cooled and dehumidified enters indoor device 101 through air inlet 112 and is directed by air directing valve 113 to desiccant coated passive heat transfer device 109. Process air passes over the exposed surface of desiccant coated passive heat transfer device 109, cooling and dehumidifying the air. Moisture from the air is adsorbed onto the desiccant, increasing the moisture content of the desiccant. The heat of adsorption from the desiccant is transferred to passive heat transfer device 109 by conduction, and to the refrigerant flowing through. Sensible heat from the process airstream is also transferred to passive heat transfer device 109 and to the refrigerant flowing through. The cooled and dehumidified air is then drawn through air directing valve 114 by process fan 115, and passes through air outlet 116 to the conditioned space 117.

Regeneration air 118 enters indoor device 101 through inlet duct 119 and is directed by air directing valve 120 to desiccant coated passive heat transfer device 107. Regeneration air passes over the exposed surface of desiccant coated passive heat transfer device 107. Heat passes from the refrigerant to passive heat transfer device 107, and on to the desiccant, causing desorption of moisture from the desiccant to the passing air. In this way the desiccant is regenerated to begin the next cycle. Regeneration air is then drawn through air directing valve 121 by fan 122 and through outlet duct 123 to the outdoor space 124.

Ambient air 126 from the environment enters outdoor device 102 through inlet 127. Air passes over the exposed surface of passive heat transfer device 104. Heat passes from the refrigerant to passive heat transfer device 104, and from passive heat transfer device 104 to the air. Air is drawn by fan 128 from passive heat transfer device 104 through outlet 129 and back to the outdoor space 130.

FIG. 1B shows the second half-cycle of operation of system 100. Low-pressure refrigerant at a first pressure state enters compressor 103 and is compressed to a second pressure state (e.g., high-pressure state) that is higher than the first pressure state. Refrigerant then flows through uncoated passive heat transfer device 104, releasing some heat to ambient airstream 126. Refrigerant then flows through refrigerant reversing valve 105 (configured in a second valve state) and is directed to refrigerant line 110. Refrigerant then flows through refrigerant line 110 from outdoor device 102 to indoor device 101. Refrigerant then flows through desiccant coated passive heat transfer device 109, releasing some heat to regeneration airstream 118. Refrigerant then flows through expansion valve 108 which takes the refrigerant from a high-pressure state to a low-pressure state. Refrigerant then flows through desiccant coated passive heat transfer device 107 absorbing some heat from process air 111. Refrigerant then flows through refrigerant line 106 from indoor device 101 to outdoor device 102. Refrigerant then flows through reversing valve 105 (in the second valve state) and back to compressor 103, completing the circuit.

Process air 111 to be cooled and dehumidified enters indoor device 101 through air inlet 112 and is directed by air directing valve 113 to desiccant coated passive heat transfer device 107. Process air passes over the exposed surface of desiccant coated passive heat transfer device 107, cooling and dehumidifying the air. Moisture from the air is adsorbed onto the desiccant, increasing the moisture content of the desiccant. The heat of adsorption from the desiccant is transferred to passive heat transfer device 107 by conduction, and to the refrigerant flowing through. Sensible heat from the process airstream is also transferred to passive heat transfer device 107 and to the refrigerant flowing through. The cooled and dehumidified air is then drawn through air directing valve 114 by process fan 115, and passes through air outlet 116 to the conditioned space 117.

Regeneration air 118 enters indoor device 101 through inlet duct 119 and is directed by air directing valve 120 to desiccant coated passive heat transfer device 109. Regeneration air passes over the exposed surface of desiccant coated passive heat transfer device 109. Heat passes from the refrigerant to passive heat transfer device 109, and on to the desiccant, causing desorption of moisture from the desiccant to the passing air. In this way the desiccant is regenerated to begin the next cycle. Regeneration air is drawn through air directing valve 121 by fan 122 and through outlet duct 123 to the outdoor space 124.

Ambient air 126 from the environment enters outdoor device 102 through inlet 127. Air passes over the exposed surface of passive heat transfer device 104. Heat passes from the refrigerant to passive heat transfer device 104, and from passive heat transfer device 104 to the air. Air is drawn by fan 128 from passive heat transfer device 104 through outlet 129 and back to the outdoor space 130.

In some embodiments of system 100, a common fan is used to perform the functions of fans 115 and 122. In some embodiments of system 100, fan 122 may be placed at any other location along the airflow path between 118 and 124, similarly fan 115 may be placed at any other location along the airflow path between 111 and 117.

FIGS. 2A and 2B show schematic views of an exemplary desiccant cooling and dehumidification system 200. In operation, system 200 cycles between two modes of operation: a first mode (also referred to as a first half-cycle), and a second mode (also referred to as an a second half-cycle). FIG. 2A illustrates the first mode of operation and 2B illustrates the second mode of operation. System 200 includes a heat pump comprising compressor 203, uncoated passive heat transfer device 209, refrigerant reversing valve 204, a first desiccant coated passive heat transfer device 206, refrigerant flow directing and metering device 208, and a second desiccant coated passive heat transfer device 211. System 200 further includes first air directing valve 215, second air directing valve 216, and first fan 217. System 200 further includes first air duct 221, third air directing valve 222, fourth air directing valve 223, second fan 224, and second air duct 225. System 200 further includes third fan 230.

As shown in the example of FIGS. 2A and 2B, compressor 203, uncoated passive heat transfer device 209, refrigerant flow directing and metering device 208, refrigerant reversing valve 204 and fan 230 are located outside of the conditioned space within one or more housing structures and form outdoor device 202. Desiccant coated passive heat transfer devices 206 and 211, air directing valves 215, 216, 222, and 223, and fans 217 and 224 are located inside the conditioned space within one or more housing structures and form indoor device 201. The indoor space and outdoor space are separated by dividing wall 227. Indoor device 201 and outdoor device 202 are thermally connected through refrigerant lines 205, 207, 210, and 212 that pass through the dividing wall 227. Furthermore, indoor device 201 is physically connected to air ducts 221 and 225 which pass through dividing wall 227 to the outdoor space.

System 200 operates in a cyclic manner, alternating between two modes of operation, shown by FIGS. 2A and 2B. During the first half-cycle, desiccant coated passive heat transfer device 211 is in process mode and desiccant coated passive heat transfer device 206 is in regeneration mode. During the second half-cycle, desiccant coated passive heat transfer device 211 and desiccant coated passive heat transfer device 206 reverse such that desiccant coated passive heat transfer device 211 is in regeneration mode mode and desiccant coated passive heat transfer device 206 is in process mode. In both modes, refrigerant flow directing and metering device 208 passes high pressure refrigerant first through uncoated passive heat transfer device 209 and then through an expansion valve contained therein. FIG. 3 shows possible embodiments of refrigerant flow directing and metering device 208.

FIG. 2A shows the first half-cycle of operation of system 200. Low-pressure refrigerant at a first pressure state enters compressor 203 and is compressed to a second pressure state (e.g., high-pressure state) that is higher than the first pressure state. Refrigerant then flows through refrigerant reversing valve 204 (configured in a first valve state) and is directed to refrigerant line 205. Refrigerant then flows through refrigerant line 205 from outdoor device 202 to indoor device 201. Refrigerant then flows through desiccant coated passive heat transfer device 206, releasing some heat to regeneration airstream 220. Refrigerant then flows through refrigerant line 207 from indoor device 201 to outdoor device 202. Refrigerant then flows through refrigerant flow directing and metering device 208 to uncoated passive heat transfer device 209 releasing some heat to ambient airstream 228 and then through an expansion valve in refrigerant flow directing and metering device 208. Refrigerant then flows through refrigerant line 210 from outdoor device 202 to indoor device 201. Refrigerant then flows through desiccant coated passive heat transfer device 211, absorbing some heat from process air 213. Refrigerant then flows through refrigerant line 212 from indoor device 201 to outdoor device 202. Refrigerant then flows through reversing valve 204 (in the first valve state) and back to compressor 203, completing the circuit.

Process air 213 to be cooled and dehumidified enters indoor device 201 through air inlet 214 and is directed by air directing valve 215 to desiccant coated passive heat transfer device 211. Process air passes over the exposed surface of desiccant coated passive heat transfer device 211, cooling and dehumidifying the air. Moisture from the air is adsorbed onto the desiccant, increasing the moisture content of the desiccant. The heat of adsorption from the desiccant is transferred to passive heat transfer device 211 by conduction, and to the refrigerant flowing through. Sensible heat from the process airstream is also transferred to passive heat transfer device 211 and to the refrigerant flowing through. The cooled and dehumidified air is then drawn through air directing valve 216 by process fan 217, and passes through air outlet 218 to the conditioned space 219.

Regeneration air 220 enters indoor device 201 through inlet duct 221 and is directed by air directing valve 222 to desiccant coated passive heat transfer device 206. Regeneration air passes over the exposed surface of desiccant coated passive heat transfer device 206. Heat passes from the refrigerant to passive heat transfer device 206, and on to the desiccant, causing desorption of moisture from the desiccant to the passing air. In this way the desiccant is regenerated to begin the next cycle. Regeneration air is then drawn through air directing valve 223 by fan 224 and through outlet duct 225 to the outdoor space 226.

Ambient air 228 from the environment enters outdoor device 202 through inlet 229. Air passes over the exposed surface of passive heat transfer device 209. Heat passes from the refrigerant to passive heat transfer device 209, and from passive heat transfer device 209 to the air. Air is drawn by fan 230 from passive heat transfer device 209 through outlet 231 and back to the outdoor space 232.

FIG. 2B shows the second half-cycle of operation of system 200. Low-pressure refrigerant at a first pressure state enters compressor 203 and is compressed to a second pressure state (e.g., high-pressure state) that is higher than the first pressure state. Refrigerant then flows through refrigerant reversing valve 204 (configured in a second valve state) and is directed to refrigerant line 212. Refrigerant then flows through refrigerant line 212 from outdoor device 202 to indoor device 201. Refrigerant then flows through desiccant coated passive heat transfer device 211, releasing some heat to regeneration airstream 220. Refrigerant then flows through refrigerant line 210 from indoor device 201 to outdoor device 202. Refrigerant then flows through refrigerant flow directing and metering device 208 to uncoated passive heat transfer device 209 releasing some heat to ambient airstream 228 and then through an expansion valve in refrigerant flow directing and metering device 208. Refrigerant then flows through refrigerant line 207 from outdoor device 202 to indoor device 201. Refrigerant then flows through desiccant coated passive heat transfer device 206, absorbing some heat from process air 213. Refrigerant then flows through refrigerant line 205 from indoor device 201 to outdoor device 202. Refrigerant then flows through reversing valve 204 (in the second valve state) and back to compressor 203, completing the circuit.

Process air 213 to be cooled and dehumidified enters indoor device 201 through air inlet 214 and is directed by air directing valve 215 to desiccant coated passive heat transfer device 206. Process air passes over the exposed surface of desiccant coated passive heat transfer device 206, cooling and dehumidifying the air. Moisture from the air is adsorbed onto the desiccant, increasing the moisture content of the desiccant. The heat of adsorption from the desiccant is transferred to passive heat transfer device 206 by conduction, and to the refrigerant flowing through. Sensible heat from the process airstream is also transferred to passive heat transfer device 206 and to the refrigerant flowing through. The cooled and dehumidified air is then drawn through air directing valve 216 by process fan 217, and passes through air outlet 218 to the conditioned space 219.

Regeneration air 220 enters indoor device 201 through inlet duct 221 and is directed by air directing valve 222 to desiccant coated passive heat transfer device 211. Regeneration air passes over the exposed surface of desiccant coated passive heat transfer device 211. Heat passes from the refrigerant to passive heat transfer device 211, and on to the desiccant, causing desorption of moisture from the desiccant to the passing air. In this way the desiccant is regenerated to begin the next cycle. Regeneration air is then drawn through air directing valve 223 by fan 224 and through outlet duct 225 to the outdoor space 226.

Ambient air 228 from the environment enters outdoor device 202 through inlet 229. Air passes over the exposed surface of passive heat transfer device 209. Heat passes from the refrigerant to passive heat transfer device 209, and from passive heat transfer device 209 to the air. Air is drawn by fan 230 from passive heat transfer device 209 through outlet 231 and back to the outdoor space 232.

In some embodiments of system 200, refrigerant flow directing and metering device 208 is located within indoor device 201 instead of outdoor device 202.

In some embodiments of systems 100 and 200 the air switching valves are arranged in an alternative configuration such that two inlet air valves are arranged to select between return air from the conditioned space and outside air through an inlet air duct. Furthermore two exit valves are arranged to select between the conditioned space supply duct and to outside air through an exhaust air duct. In this embodiment each desiccant coated passive heat transfer device is associated with a single inlet air valve and a single exit air valve.

FIGS. 3A and 3B show schematic views of an exemplary desiccant cooling and dehumidification system 300. In operation, system 300 cycles between two modes of operation: a first mode (also referred to as a first half-cycle), and a second mode (also referred to as an a second half-cycle). FIG. 3A illustrates the first mode of operation and 3B illustrates the second mode of operation. System 300 includes a heat pump comprising compressor 304, uncoated passive heat transfer device 305, refrigerant reversing valve 307, desiccant coated passive heat transfer device 320, expansion valve 308, and a second uncoated passive heat transfer device 310. System 300 further includes first air directing valve 319, second air directing valve 322, and first fan 321. System 300 further includes air ducts 331 and 332, second fan 327, and third fan 314.

As shown in the example of FIGS. 3A and 3B, compressor 304, uncoated passive heat transfer device 305, and fan 327 are located outside of the conditioned space within one or more housing structures and form outdoor device 303. Desiccant coated passive heat transfer device 320, air directing valves 319, and 322, fan 321, reversing valve 307, and expansion valve 308 are located inside the conditioned space in one or more housing structures and form indoor device 302. Uncoated passive heat transfer device 310 and fan 314 are located inside the conditioned space in one or more housing structures and form indoor device 301. The indoor space and outdoor space are separated by dividing wall 334. Indoor device 301 is thermally connected to indoor device 302 through refrigerant line 335. Indoor device 301 is thermally connected to outdoor device 303 through refrigerant line 311 that passes through the dividing wall 334. Indoor device 302 is thermally connected to outdoor device 303 through refrigerant line 306 that passes through the dividing wall 334. Furthermore, indoor device 302 is physically connected to air ducts 331 and 332 which pass through dividing wall 334 to the outdoor space.

System 300 operates in a cyclic manner, alternating between two modes of operation, shown by FIGS. 3A and 3B. During the first half-cycle, desiccant coated passive heat transfer device 320 is in process mode. During the second half-cycle, desiccant coated passive heat transfer device 320 is in regeneration mode.

FIG. 3A shows the first half-cycle of operation of system 300. Low-pressure refrigerant at a first pressure state enters compressor 304 and is compressed to a second pressure state (e.g., high-pressure state) that is higher than the first pressure state. Refrigerant then flows through uncoated passive heat transfer device 305, releasing some heat to ambient airstream 325. Refrigerant then flows through refrigerant line 306 from outdoor device 303 to indoor device 302. Refrigerant then flows through reversing valve 307 (configured in a first valve state) and is directed to expansion valve 308, which takes the refrigerant from a high-pressure state to a low-pressure state. Refrigerant then flows through desiccant coated passive heat transfer device 320 absorbing some heat from process air 317. Refrigerant then flows through reversing valve 307 (in the first valve state) and is directed to refrigerant line 335. Refrigerant flows through refrigerant line 335 from indoor device 302 to indoor device 301. Refrigerant then flows through uncoated passive heat transfer device 310 absorbing heat from process air 312. Refrigerant then flows through refrigerant line 311 from indoor device 301 to outdoor device 303 and returns to compressor 304, completing the refrigerant circuit.

Process air 312 to be cooled enters indoor device 301 through air inlet 313 and passes over the exposed surface of uncoated passive heat transfer device 310, cooling the air.

Process air 317 to be cooled and dehumidified enters indoor device 302 through air inlet 318 and is directed by air directing valve 319 to desiccant coated passive heat transfer device 320. Process air passes over the exposed surface of desiccant coated passive heat transfer device 320, cooling and dehumidifying the air. Moisture from the air is adsorbed onto the desiccant, increasing the moisture content of the desiccant. The heat of adsorption from the desiccant is transferred to passive heat transfer device 320 by conduction, and to the refrigerant flowing through. Sensible heat from the process airstream is also transferred to passive heat transfer device 320 and to the refrigerant flowing through. The cooled and dehumidified air is then blown through air directing valve 322 by process fan 321, and passes through air outlet 323 to the conditioned space 324.

Ambient air 325 from the environment enters outdoor device 303 through inlet 326. Air passes over the exposed surface of passive heat transfer device 305. Heat passes from the refrigerant to passive heat transfer device 305, and from passive heat transfer device 305 to the air. Air is drawn by fan 327 from passive heat transfer device 305 through outlet 328 and back to the outdoor space 329.

FIG. 3B shows the second half-cycle of operation of system 300. Low-pressure refrigerant at a first pressure state enters compressor 304 and is compressed to a second pressure state (e.g., high-pressure state) that is higher than the first pressure state. Refrigerant then flows through uncoated passive heat transfer device 305, releasing some heat to ambient airstream 325. Refrigerant then flows through refrigerant line 306 from outdoor device 303 to indoor device 302. Refrigerant then flows through reversing valve 307 (configured in a second valve state) and is directed to desiccant coated passive heat transfer device 320. Refrigerant then flows through desiccant coated passive heat transfer device 320, releasing some heat to regeneration airstream 333. Refrigerant then flows through expansion valve 308, which takes the refrigerant from a high-pressure state to a low-pressure state. Refrigerant then flows through reversing valve 307 (in the second valve state) and is directed to refrigerant line 335. Refrigerant flows through refrigerant line 335 from indoor device 302 to indoor device 301. Refrigerant then flows through uncoated passive heat transfer device 310 absorbing heat from process air 312. Refrigerant then flows through refrigerant line 311 from indoor device 301 to outdoor device 303 and returns to compressor 304, completing the refrigerant circuit.

Process air 312 to be cooled enters indoor device 301 through air inlet 313 and passes over the exposed surface of uncoated passive heat transfer device 310, cooling the air.

Regeneration air 333 enters indoor device 302 through inlet duct 332 and is directed by air directing valve 319 to desiccant coated passive heat transfer device 320. Regeneration air passes over the exposed surface of desiccant coated passive heat transfer device 320. Heat passes from the refrigerant to passive heat transfer device 320, and on to the desiccant, causing desorption of moisture from the desiccant to the passing air. In this way the desiccant is regenerated to begin the next cycle. Regeneration air is then blown through air directing valve 322 by fan 321 and through outlet duct 331 to the outdoor space 330.

Ambient air 325 from the environment enters outdoor device 303 through inlet 326. Air passes over the exposed surface of passive heat transfer device 305. Heat passes from the refrigerant to passive heat transfer device 305, and from passive heat transfer device 305 to the air. Air is drawn by fan 327 from passive heat transfer device 305 through outlet 328 and back to the outdoor space 329.

In some embodiments of system 300, indoor devices 301 and 302 may be combined within a common housing structure. Various embodiments are possible with devices 301, 302, and 303 located inside or outside the conditioned space as separate devices or combined in a common housing structure. In some operating modes of system 300, uncoated passive heat transfer device 310 may be operated below the dewpoint of process air 312. Such an operating mode allows uncoated passive heat transfer device 310 to dehumidify process air 312 as well as cooling it. In some embodiments, an additional expansion valve is added to refrigerant line 335 between reversing valve 307 and uncoated passive heat transfer device 310.

FIGS. 4A and 4B show schematic views of an exemplary desiccant cooling and dehumidification system 400. In operation, system 400 cycles between two modes of operation: a first mode (also referred to as a first half-cycle), and a second mode (also referred to as an a second half-cycle). FIG. 4A illustrates the first mode of operation and 4B illustrates the second mode of operation. System 400 includes a heat pump comprising compressor 402, refrigerant reversing valve 403, first desiccant coated passive heat transfer device 406, expansion valve 405, and a second desiccant coated passive heat transfer device 404. System 400 further includes first air directing valve 409, second air directing valve 415, first fan 410, second fan 416, and air duct 419.

As shown in the example of FIGS. 4A and 4B, all components are located inside the conditioned space in one or more housing structures and form indoor device 401. The indoor space and outdoor space are separated by dividing wall 417. Indoor device 401 is physically connected to air duct 419 which passes through dividing wall 417 to the outdoor space.

System 400 operates in a cyclic manner, alternating between two modes of operation, shown by FIGS. 4A and 4B. During the first half-cycle, desiccant coated passive heat transfer device 404 is in process mode and desiccant coated passive heat transfer device 406 is in regeneration mode. During the second half-cycle, desiccant coated passive heat transfer device 404 is in regeneration mode and passive heat transfer device 406 is in process mode.

FIG. 4A shows the first half-cycle of operation of system 400. Low-pressure refrigerant at a first pressure state enters compressor 402 and is compressed to a second pressure state (e.g., high-pressure state) that is higher than the first pressure state. Refrigerant then flows through reversing valve 403 (configured in a first valve state) and is directed to desiccant coated passive heat transfer device 406. Refrigerant then flows through desiccant coated passive heat transfer device 406 releasing some heat to regeneration airstream 413. Refrigerant then flows through expansion valve 405, which takes the refrigerant from a high-pressure state to a low-pressure state. Refrigerant then flows through desiccant coated passive heat transfer device 404 absorbing some heat from process air 407. Refrigerant then flows through reversing valve 403 (in the first valve state) and returns to compressor 402, completing the refrigerant circuit.

Process air 407 to be cooled and dehumidified enters indoor device 401 through air inlet 408. Process air passes over the exposed surface of desiccant coated passive heat transfer device 404, cooling and dehumidifying the air. Moisture from the air is adsorbed onto the desiccant, increasing the moisture content of the desiccant. The heat of adsorption from the desiccant is transferred to passive heat transfer device 404 by conduction, and to the refrigerant flowing through. Sensible heat from the process airstream is also transferred to passive heat transfer device 404 and to the refrigerant flowing through. The cooled and dehumidified air is then drawn through air directing valve 409 by process fan 410, and passes through air outlet 411 to the conditioned space 412.

Regeneration air 413 enters indoor device 401 through inlet duct 414. Regeneration air passes over the exposed surface of desiccant coated passive heat transfer device 406. Heat passes from the refrigerant to passive heat transfer device 406, and on to the desiccant, causing desorption of moisture from the desiccant to the passing air. In this way the desiccant is regenerated to begin the next cycle. Regeneration air is then drawn through air directing valve 415 by fan 416 and through outlet duct 418 to the outdoor space 419.

FIG. 4B shows the second half-cycle of operation of system 400. Low-pressure refrigerant at a first pressure state enters compressor 402 and is compressed to a second pressure state (e.g., high-pressure state) that is higher than the first pressure state. Refrigerant then flows through reversing valve 403 and is directed to desiccant coated passive heat transfer device 404. Refrigerant then flows through desiccant coated passive heat transfer device 404 releasing some heat to regeneration airstream 407. Refrigerant then flows through expansion valve 405, which takes the refrigerant from a high-pressure state to a low-pressure state. Refrigerant then flows through desiccant coated passive heat transfer device 406 absorbing some heat from process air 413. Refrigerant then flows through reversing valve 403 (configured in a second valve state) and returns to compressor 402, completing the refrigerant circuit.

Process air 413 to be cooled and dehumidified enters indoor device 401 through air inlet 414. Process air passes over the exposed surface of desiccant coated passive heat transfer device 406, cooling and dehumidifying the air. Moisture from the air is adsorbed onto the desiccant, increasing the moisture content of the desiccant. The heat of adsorption from the desiccant is transferred to passive heat transfer device 406 by conduction, and to the refrigerant flowing through. Sensible heat from the process airstream is also transferred to passive heat transfer device 406 and to the refrigerant flowing through. The cooled and dehumidified air is then drawn through air directing valve 415 by process fan 410, and passes through air outlet 411 to the conditioned space 412.

Regeneration air 407 enters indoor device 401 through inlet duct 408. Regeneration air passes over the exposed surface of desiccant coated passive heat transfer device 404. Heat passes from the refrigerant to passive heat transfer device 404, and on to the desiccant, causing desorption of moisture from the desiccant to the passing air. In this way the desiccant is regenerated to begin the next cycle. Regeneration air is then drawn through air directing valve 409 by fan 416 and through outlet duct 418 to the outdoor space 419.

In some embodiments of system 400, air inlets 408 and 414 are shared and the process air splits to passive heat transfer devices 404 and 406 after entering the device. In some embodiments of system 400, all or some components of the device are located outside the conditioned space and achieve air exchange with the indoor space through additional ducts through dividing wall 417. In some embodiments of system 400, a second duct through dividing wall 417 and two additional air directing valves are included so in regeneration mode air is supplied from the outdoor space instead of the indoor space.

In some embodiments of systems 100-400, a liquid-line suction line heat exchanger is used. The direction of airflow through the desiccant coated passive heat transfer devices shown schematically in systems 100-400 is arbitrary. Specifically, each system includes embodiments in which the direction of airflow through the desiccant coated passive heat transfer devices is the same in both modes of operation (parallel flow) and in which the direction of airflow through the desiccant coated passive heat transfer devices reverses between the first and second modes of operation (counterflow).

FIGS. 5A through 5D shows details of two embodiments of refrigerant flow directing and metering device 208 in two modes of operation. FIG. 5A shows embodiment A in mode 1. FIG. 5B shows embodiment A in mode 2. FIG. 5C shows embodiment B in mode 1. FIG. 5D shows embodiment B in mode 2. Embodiment A is comprised of refrigerant check valves 502, 503, 506, and 508, expansion valve 509, and refrigerant lines 501, 504, 505, and 507. Embodiment B is comprised of refrigerant check valves 510 and 515, expansion valves 511 and 514, and refrigerant lines 510, 514, 516, and 517.

As shown in FIG. 5A, in mode 1 of embodiment A, high pressure refrigerant enters the device through refrigerant line 501. Refrigerant passes through check valve 502 and is blocked from passing through check valve 503. Refrigerant flows out of device 208 through refrigerant line 504. High pressure refrigerant enters the device through refrigerant line 505, then passes through expansion valve 509, which takes the refrigerant from a high-pressure state to a low-pressure state. Low pressure refrigerant then passes through check valve 506 and is blocked from passing through check valve 508. Refrigerant then flows out of device 208 through refrigerant line 507.

As shown in FIG. 5B, in mode 2 of embodiment A, high pressure refrigerant enters the device through refrigerant line 507. Refrigerant passes through check valve 508 and is blocked from passing through check valve 506. Refrigerant flows out of device 208 through refrigerant line 504. High pressure refrigerant enters the device through refrigerant line 505, then passes through expansion valve 509, which takes the refrigerant from a high-pressure state to a low-pressure state. Low pressure refrigerant then passes through check valve 503 and is blocked from passing through check valve 502. Refrigerant then flows out of device 208 through refrigerant line 501.

As shown in FIG. 5C, in mode 1 of embodiment B, high pressure refrigerant enters the device through refrigerant line 517. Refrigerant passes through check valve 510. Refrigerant flows out of device 208 through refrigerant line 512. High pressure refrigerant enters the device through refrigerant line 513. Refrigerant is blocked from passing through check valve 515 and passes through expansion valve 514, which takes the refrigerant from a high-pressure state to a low-pressure state. Low pressure refrigerant then flows out of device 208 through refrigerant line 516.

As shown in FIG. 5D, in mode 2 of embodiment B, high pressure refrigerant enters the device through refrigerant line 516. Refrigerant passes through check valve 515. Refrigerant flows out of device 208 through refrigerant line 513. High pressure refrigerant enters the device through refrigerant line 512. Refrigerant is blocked from passing through check valve 510 and passes through expansion valve 511, which takes the refrigerant from a high-pressure state to a low-pressure state. Low pressure refrigerant then flows out of device 208 through refrigerant line 517.

FIGS. 6A and 6B show two modes of operation of one embodiment of an indoor unit of system 100, 200, 300, or 400 in cross-section view. In this embodiment the desiccant coated passive heat transfer device is a fin-and-tube heat exchanger with desiccant partially coated on the fins of the heat exchanger, and the fan is a crossflow fan.

As shown in FIG. 6A, in mode 1 heat exchanger 604 is in process mode. Return air 601 from the conditioned space enters device 600 through opening 602 and passes through air directing valve 603 in a first position to heat exchanger 604. The air is first exposed to the uncoated fin surface 610, cooling the air. At surface 610, sensible heat is transferred from the air to heat exchanger 604 and to the refrigerant flowing through. The air is then exposed to desiccant coated fin surface 605, cooling and dehumidifying the air. At surface 605, moisture from the air is adsorbed onto the desiccant, increasing the moisture content of the desiccant. The heat of adsorption from the desiccant is transferred to heat exchanger 604 by conduction, and to the refrigerant flowing through. Sensible heat from the process airstream is also transferred to heat exchanger 604 and to the refrigerant flowing through. Air is then drawn through crossflow fan 606 and passes by air directing valve 607 in a first position through opening 608 to the conditioned space 609.

As shown in FIG. 6B, in mode 2 heat exchanger 604 is in regeneration mode. Outdoor air 614 enters device 600 through opening 611 and passes through air directing valve 603 in a second position to heat exchanger 604. The air is first exposed to the uncoated fin surface 610, heating the air. At surface 610, sensible heat is transferred from refrigerant flowing through heat exchanger 604 to the exposed surface 610 and onward to the air. The air is then exposed to desiccant coated fin surface 605, heating and humidifying the air. At surface 605, heat is transferred from refrigerant flowing through heat exchanger 604 to the desiccant coated on surface 605 causing desorption of moisture from the desiccant to the passing air. Air is then drawn through crossflow fan 606 and passes by air directing valve 607 in a second position through opening 612 to the outdoor space 613.

In some embodiments of device 600 an additional operation mode allows outdoor air to be drawn from ambient air 614 through opening 611 while heat exchanger 604 is in process mode to cool and ventilate the conditioned space.

In the examples described above, at least a portion or an entire surface of any of the passive heat transfer device(s) described above can be at least partially or completely coated with a desiccant material according to various examples. In one example, a surface of the passive heat transfer device can be between at least one tenth covered (e.g., 10% covered) and up to completely covered (100% covered) with desiccant material, or any coverage value in between the described range.

FIG. 7 depicts a method of control for a desiccant cooling and dehumidification system as described in the examples above. In an example, the method can be implemented by a process(or) and a non-transitory storage medium (e.g., memory) having instructions stored thereon and configured to be executed by the processor. Upon startup 701, the system measures the temperature and humidity of the indoor and outdoor space 702. These measurements are used to set system parameters for a default operating mode 703. During default operating mode, the temperature and humidity at the inlet and outlet of each desiccant coated passive heat transfer device is measured. After some time, the desiccant of the process stream will become saturated and the rate of moisture removal from the process airstream will decrease. At this time, the outlet humidity ratio will approach the inlet humidity ratio. The control system logs this as the required desiccant load time 704. Similarly, after some time, the desiccant of the regeneration stream will become desaturated, and the rate of moisture addition to the regeneration airstream will decrease. At this time, the outlet humidity ratio will approach the inlet humidity ratio. The control system logs this as the required desiccant unload time 704.

While the system is running in default mode 703, the indoor temperature and humidity are measured over time, and the sensible and latent load are determined 705. In one operating mode, sensible cooling is adjusted to match sensible load, and latent cooling is adjusted to match latent load. In one embodiment, sensible cooling is adjusted by modulating process fan speed. In one embodiment, latent cooling is adjusted by modulating the process duty cycle, defined as the required loading time over the switching time. In a preferred operating mode, the required desiccant unload time is modulated to equal the switching time by controlling the compressor speed and regeneration fan speed.

The foregoing has been a detailed description of illustrative embodiments of the invention. Various modifications and additions can be made without departing from the spirit and scope of this invention. Features of each of the various embodiments described above may be combined with features of other described embodiments as appropriate in order to provide a multiplicity of feature combinations in associated new embodiments. Furthermore, while the foregoing describes a number of separate embodiments of the apparatus and method of the present invention, what has been described herein is merely illustrative of the application of the principles of the present invention. For example, as used herein, the terms “process” and/or “processor” should be taken broadly to include a variety of electronic hardware and/or software based functions and components (and can alternatively be termed functional “modules” or “elements”). Moreover, a depicted process or processor can be combined with other processes and/or processors or divided into various sub-processes or processors. Such sub-processes and/or sub-processors can be variously combined according to embodiments herein. Likewise, it is expressly contemplated that any function, process and/or processor herein can be implemented using electronic hardware, software consisting of a non-transitory computer-readable medium of program instructions, or a combination of hardware and software. Additionally, as used herein various directional and dispositional terms such as “vertical”, “horizontal”, “up”, “down”, “bottom”, “top”, “side”, “front”, “rear”, “left”, “right”, and the like, are used only as relative conventions and not as absolute directions/dispositions with respect to a fixed coordinate space, such as the acting direction of gravity. Additionally, where the term “substantially” or “approximately” is employed with respect to a given measurement, value or characteristic, it refers to a quantity that is within a normal operating range to achieve desired results, but that includes some variability due to inherent inaccuracy and error within the allowed tolerances of the system (e.g. 1-5 percent). Accordingly, this description is meant to be taken only by way of example, and not to otherwise limit the scope of this invention.

Claims

1. An air-handling system comprising: the plurality of passive heat transfer devices, defining a first surface of at least one of the plurality of passive heat transfer devices that is thermally in contact with the heat pump and a second surface of at least one of the plurality of passive heat transfer devices that is exposed to allow the transfer of heat to or from the heat pump;

a heat pump configured to move heat energy between a plurality of passive heat transfer devices;

a desiccant in thermal contact with the exposed surface of at least one passive heat transfer device and configured to exchange moisture with air;

a plurality of air directing valves configured to direct process and regeneration air to and from the plurality of passive heat transfer devices with desiccant;

a heat pump reversing device configured to change the direction of heat flow in the heat pump between two modes of operation;

a control system with communication lines to control air directing valves, reversing device, and heat pump operation; and

a control operation process operating a control mode in which desiccant regeneration time is modulated.

2. The system of claim 1 wherein the passive heat transfer devices comprise tube and fin heat exchangers or microchannel heat exchangers.

3. The system of claim 2 wherein the desiccant forms a coating on the exposed surface of the heat exchanger fins.

4. The system of claim 3 wherein the desiccant forms a partial coating with an uncoated section first exposed to airflow followed by a desiccant coated second section exposed to airflow.

5. The system of claim 1, further comprising, a passive heat transfer device without desiccant configured for exchanging sensible heat with ambient air.

6. The system of claim 1, further comprising, a passive heat transfer device without desiccant configured for exchanging sensible heat with indoor air.

7. The system of claim 1 wherein the desiccant comprises at least one of silica gel, alumina, zeolite or a metal-organic framework (MOF) material.

8. A method for handling air in a space comprising the steps of:

moving, with a heat pump, heat energy between a plurality of passive heat transfer devices, in which a first surface of at least one of the plurality of passive heat transfer devices is thermally in contact with the heat pump and a second surface of at least one of the plurality of passive heat transfer devices is exposed to allow the transfer of heat to or from the heat pump;

providing a desiccant in thermal contact with the exposed surface of at least one passive heat transfer device and configured to exchange moisture with air;

directing, through a plurality of air directing valves, process and regeneration air to and from the plurality of passive heat transfer devices with desiccant;

changing a direction of heat flow in the heat pump between two modes of operation; and

controlling the plurality air directing valves, reversing device, and heat pump operation in a control operation mode to modulate desiccant regeneration time.

9. The method of claim 8 wherein the passive heat transfer devices comprise tube and fin heat exchangers or microchannel heat exchangers.

10. The method of claim 9 wherein the desiccant forms a coating on the exposed surface of the heat exchanger fins.

11. The method of claim 10 wherein the desiccant forms a partial coating with an uncoated section first exposed to airflow followed by a desiccant coated second section exposed to airflow.

12. The method of claim 8, further comprising, exchanging, using a passive heat transfer device without desiccant, sensible heat with ambient air.

13. The method of claim 8, further comprising, exchanging, using a passive heat transfer device without desiccant, sensible heat with indoor air.

14. The method of claim 8 wherein the desiccant comprises at least one of silica gel, alumina, zeolite or a metal-organic framework (MOF) material.