US20160146477A1 - Hvac systems and methods for reheat operation - Google Patents

Hvac systems and methods for reheat operation Download PDF

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US20160146477A1
US20160146477A1 US14/553,926 US201414553926A US2016146477A1 US 20160146477 A1 US20160146477 A1 US 20160146477A1 US 201414553926 A US201414553926 A US 201414553926A US 2016146477 A1 US2016146477 A1 US 2016146477A1
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valve
refrigerant
heat
reheat
pump reversing
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US14/553,926
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Terry Jewell
Eric Perez
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Lennox Industries Inc
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Lennox Industries Inc
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Priority to US14/553,926 priority Critical patent/US20160146477A1/en
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Publication of US20160146477A1 publication Critical patent/US20160146477A1/en
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    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24HEATING; RANGES; VENTILATING
    • F24FAIR-CONDITIONING; AIR-HUMIDIFICATION; VENTILATION; USE OF AIR CURRENTS FOR SCREENING
    • F24F3/00Air-conditioning systems in which conditioned primary air is supplied from one or more central stations to distributing units in the rooms or spaces where it may receive secondary treatment; Apparatus specially designed for such systems
    • F24F3/12Air-conditioning systems in which conditioned primary air is supplied from one or more central stations to distributing units in the rooms or spaces where it may receive secondary treatment; Apparatus specially designed for such systems characterised by the treatment of the air otherwise than by heating and cooling
    • F24F3/14Air-conditioning systems in which conditioned primary air is supplied from one or more central stations to distributing units in the rooms or spaces where it may receive secondary treatment; Apparatus specially designed for such systems characterised by the treatment of the air otherwise than by heating and cooling by humidification; by dehumidification
    • F24F3/153Air-conditioning systems in which conditioned primary air is supplied from one or more central stations to distributing units in the rooms or spaces where it may receive secondary treatment; Apparatus specially designed for such systems characterised by the treatment of the air otherwise than by heating and cooling by humidification; by dehumidification with subsequent heating, i.e. with the air, given the required humidity in the central station, passing a heating element to achieve the required temperature
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24HEATING; RANGES; VENTILATING
    • F24FAIR-CONDITIONING; AIR-HUMIDIFICATION; VENTILATION; USE OF AIR CURRENTS FOR SCREENING
    • F24F3/00Air-conditioning systems in which conditioned primary air is supplied from one or more central stations to distributing units in the rooms or spaces where it may receive secondary treatment; Apparatus specially designed for such systems
    • F24F3/12Air-conditioning systems in which conditioned primary air is supplied from one or more central stations to distributing units in the rooms or spaces where it may receive secondary treatment; Apparatus specially designed for such systems characterised by the treatment of the air otherwise than by heating and cooling
    • F24F3/14Air-conditioning systems in which conditioned primary air is supplied from one or more central stations to distributing units in the rooms or spaces where it may receive secondary treatment; Apparatus specially designed for such systems characterised by the treatment of the air otherwise than by heating and cooling by humidification; by dehumidification

Abstract

Systems and methods are presented that enable a heating, ventilating, and air conditioning (HVAC) system to store refrigerant within a reheat circuit. In one instance, the HVAC system includes a valve, having a first position and a second position, configured to selectively control a flow of refrigerant into a reheat coil. When in the second position, the valve enables a hot refrigerant to flow from a compressor through the reheat coil. When in the first position, the valve stops the hot refrigerant from flowing through the reheat coil but still allows refrigerant to circulate through the closed-conduit refrigeration circuit. In the first position, refrigerant remains stored in the reheat circuit, which includes the reheat coil. Other systems and methods are presented.

Description

    TECHNICAL FIELD
  • The present disclosure relates generally to heating, ventilating, and air conditioning (HVAC) systems, and more particularly, to systems and methods for reheat operation.
  • BACKGROUND
  • Heating, ventilating, and air conditioning (HVAC) systems can be used to regulate the environment within an enclosed space. Typically, an air blower is used to pull air (i.e., return air) from the enclosed space into the HVAC system through ducts and push the air into the enclosed space through additional ducts after conditioning the air (e.g., heating, cooling, or dehumidifying the air).
  • The heating aspect of an HVAC system may utilize a reheat coil to supply heat to air first cooled by an evaporator of the HVAC system. The reheat coil utilizes hot, high-pressure gas refrigerant from a compressor to supply heat.
  • BRIEF DESCRIPTION OF THE DRAWINGS
  • Illustrative embodiments of the present disclosure are described in detail below with reference to the attached drawing figures, which are incorporated by reference herein.
  • FIG. 1 is a schematic diagram of a heating, ventilating, and air conditioning (HVAC) system that includes a valve for selectively controlling a flow of refrigerant into a reheat coil, according to an illustrative embodiment;
  • FIG. 2A is a schematic diagram of a heating, ventilating, and air conditioning (HVAC) system having a valve that includes a heat-pump reversing valve, according to an illustrative embodiment;
  • FIG. 2B is a schematic diagram of the heat-pump reversing valve of FIG. 2A showing, in detail view, a third flow path and a fourth flow path active therethrough, according to an illustrative embodiment;
  • FIG. 3 is a flow chart of an illustrative method of regulating humidity in air conditioned by a heating, ventilating, and air conditioning (HVAC) system.
  • The figures described above are only exemplary and their illustration is not intended to assert or imply any limitation with regard to the environment, architecture, design, configuration, method, or process in which different embodiments may be implemented.
  • DETAILED DESCRIPTION OF THE ILLUSTRATIVE EMBODIMENTS
  • In the following detailed description of the illustrative embodiments, reference is made to the accompanying drawings that form a part hereof. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, and it is understood that other embodiments may be utilized and that logical structural, mechanical, electrical, and chemical changes may be made without departing from the scope of the invention. To avoid detail not necessary to enable those skilled in the art to practice the embodiments described herein, the description may omit certain information known to those skilled in the art. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the illustrative embodiments is defined only by the appended claims.
  • In the drawings and description that follow, like parts are typically marked throughout the specification and drawings with the same reference numerals or coordinated numerals. The drawing figures are not necessarily to scale. Certain features of the illustrative embodiments may be shown exaggerated in scale or in somewhat schematic form and some details of conventional elements may not be shown in the interest of clarity and conciseness.
  • During operation of a heating, ventilation, and air conditioning (HVAC) system, an evaporator is commonly used to cool a return air to a target temperature. However, the target temperature may be inadequate to condense sufficient moisture out of the return air to achieve a desired humidity threshold. The HVAC system may therefore employ a reheat coil in proximity to the evaporator. The evaporator first cools the return air to an intermediate temperature that is below the target temperature, but reduces the humidity. The reheat coil is then used to reheat the return air to the target temperature. It will be appreciated that the intermediate temperature corresponds to a dew-point where sufficient moisture condenses out of the return air. The return air therefore exits the HVAC system at the target temperature and the desired humidity threshold (or below).
  • In the HVAC system, the evaporator is part of a closed-conduit refrigerant circuit that includes a compressor and a condenser. The reheat coil may be part of a reheat circuit that includes a supply line and a return line. The supply line and the return line enable hot refrigerant from the closed-conduit refrigeration circuit to circulate through the reheat coil. When the reheat coil is dormant, the HVAC system typically drains refrigerant from the reheat circuit using a suction port of the compressor. The drained refrigerant is then transferred to the closed-conduit refrigeration circuit. Because the closed-conduit refrigeration circuit already contains refrigerant, this transfer of refrigerant is associated with a pressure increase within the closed-conduit refrigeration circuit. The condenser, however, may not tolerate the pressure increase in certain situations. For example, microchannel condensers may leak, burst, or trip a high-pressure safety switch if exposed to such elevated levels of refrigerant. Microchannel condensers, however, are advantageous for use in HVAC systems, bringing benefits such as improved heat-exchange efficiencies and compact dimensions (i.e., relative to conventional “tube-and-fin” designs).
  • The embodiments herein relate to systems and methods for regulating a moisture content of air conditioned by an HVAC system. More specifically, systems and methods are presented that enable a reheat circuit to store refrigerant therein, thereby avoiding refrigerant transfers between the reheat circuit and a closed-conduit refrigerant circuit. Such storage capability is particularly valuable when the HVAC system includes a microchannel condenser. In one illustrative embodiment, the HVAC system includes a valve configured to selectively control a flow of refrigerant into a reheat coil. When in a first position, the valve enables a hot refrigerant to flow from a compressor through the reheat coil. When in a second position, the valve stops the hot refrigerant from flowing through the reheat coil but still allows refrigerant to circulate through the closed-conduit refrigeration circuit. In the second position, refrigerant remains stored in the reheat circuit, which includes the reheat coil. Other systems and methods are presented below.
  • Unless otherwise specified, any use of any form of the terms “connect,” “engage,” “couple,” “attach,” or any other term describing an interaction between elements is not meant to limit the interaction to direct interaction between the elements and may also include indirect interaction between the elements described. In the following discussion and in the claims, the terms “including” and “comprising” are used in an open-ended fashion, and thus should be interpreted to mean “including, but not limited to”. Unless otherwise indicated, as used throughout this document, “or” does not require mutual exclusivity.
  • As used herein, the phrases “hydraulically coupled,” “hydraulically connected,” “in hydraulic communication,” “fluidly coupled,” “fluidly connected,” and “in fluid communication” refer to a form of coupling, connection, or communication related to fluids, and the corresponding flows or pressures associated with these fluids. In some embodiments, a hydraulic coupling, connection, or communication between two components describes components that are associated in such a way that fluid pressure may be transmitted between or among the components. Reference to a fluid coupling, connection, or communication between two components describes components that are associated in such a way that a fluid can flow between or among the components. Hydraulically coupled, connected, or communicating components may include certain arrangements where fluid does not flow between the components, but fluid pressure may nonetheless be transmitted such as via a diaphragm or piston.
  • As used herein, the terms “hot,” “warm,” “cool,” and “cold” refer to thermal states, on a relative basis, of refrigerant within a closed-conduit refrigeration circuit. Actual temperatures corresponding to these thermal states will depend on a design of the closed-conduit refrigeration circuit and its operating conditions. In general, temperatures associated with the thermal states decrease sequentially from “hot” to “warm” to “cool” to “cold”.
  • Referring now to the drawings and primarily to FIG. 1, a schematic diagram is presented of a heating, ventilating, and air conditioning (HVAC) system 100 that includes a valve 102 for selectively controlling a flow of refrigerant into a reheat coil 148. The system 100 includes a closed-conduit refrigeration circuit 101 having an evaporator 104 and a compressor 106. The evaporator 104 is fluidly-coupled to the compressor 106 through a suction line 108 and may include at least one evaporator fan 110 to circulate a return air 112 across one or more heat-exchange surfaces of the evaporator 104. The return air 112 is typically directed from a conditioned space towards the evaporator 104 by an air-handling subsystem (e.g., ducts, vents, louvers, dampers, grills, etc.). The return air 112 exits the evaporator 104 as a cooled airflow 114. Concomitantly, a low-pressure liquid refrigerant 116 enters the evaporator 104 and leaves as a low-pressure gas refrigerant 118. The evaporator 104 is configured to transfer heat from the return air 112 to the low-pressure liquid refrigerant 116. The suction line 108 conveys the low-pressure gas refrigerant 118 from the evaporator 104 to the compressor 106. The compressor 106 performs work on the low-pressure gas refrigerant 118 to generate a high-pressure gas refrigerant 120, which exits from the compressor 106 through a first discharge line 122.
  • The closed-conduit refrigeration circuit 101 also includes the valve 102, which is fluidly-coupled to the compressor 106 through the first discharge line 122. The valve 102 is configured to selectively direct refrigerant from at least one valve inlet to a plurality of valve outlets. In FIG. 1, the valve 102 is depicted as having one valve inlet fluidly-coupled with two valve outlets through a first flow pathway 124 and a second flow pathway 126. The high-pressure gas refrigerant 120 from the compressor 106 may traverse the valve 102 through either the first flow pathway 124 or the second flow pathway 126, but not both simultaneously. Activation of either the first flow pathway 124 or the second flow pathway 126 may depend on a position of the valve 102. If the valve 102 is in a first position, in which the first flow pathway 124 is active, the high-pressure gas refrigerant 120 leaves the valve 102 to enter a second discharge line 130. Alternatively, if the valve 102 is in a second position, in which the second flow pathway 126 is active, the high-pressure gas refrigerant 120 leaves the valve 102 to enter another line 154 of the HVAC system 100, as will be described below. The depiction of FIG. 1, however, is not intended as limiting. Other numbers of valve inlets, valve outlets, and flow pathways therebetween are possible for the valve 102. In some embodiments, the valve 102 includes a bleed-port reheat valve.
  • The closed-conduit refrigeration circuit 101 includes a microchannel condenser 132 fluidly-coupled to the valve 102 through the second discharge line 130. The microchannel condenser 132 may include at least one microchannel condenser fan 134 to circulate a non-conditioned air 136 across one or more heat-exchange surfaces of the microchannel condenser 132. The non-conditioned air 136 exits the microchannel condenser 128 as a warmed airflow 138. Concomitantly, the high-pressure gas refrigerant 120 enters the microchannel condenser 132 and leaves as a high-pressure liquid refrigerant 140. The microchannel condenser 132 is configured to transfer heat from the high-pressure gas refrigerant 120 to a non-conditioned air 136. A liquid line 142 fluidly-couples the microchannel condenser 132 to an expansion valve 144. The liquid line 142 enables the high-pressure liquid refrigerant 140 to reach the expansion valve 144, where the high-pressure liquid refrigerant 140 can be de-pressurized to form the low-pressure liquid refrigerant 116. The expansion valve 144 is fluidly-coupled to the evaporator 104 via a refrigerant line 146. The low-pressure liquid refrigerant 116 traverses the refrigerant line 146 to leave the expansion valve 144 and enter the evaporator 104.
  • The HVAC system 100 also includes a reheat coil 148 proximate the evaporator 104. The reheat coil 148 has an inlet 150 and an outlet 152 fluidly-coupled to, respectively, a supply line 154 and a return line 156. The supply line 154 fluidly-couples the inlet 150 of the reheat coil 148 to the valve 102, which may include the valve outlet associated with the second flow path 126. The return line 156 fluidly-couples the outlet 152 of the reheat coil 148 to the second discharge line 130.
  • It will be appreciated that the valve 102 is configured to selectively control a flow of refrigerant into the reheat coil 148. Thus, refrigerant may flow through a reheat circuit 153 defined, in part, by the reheat coil 148, the supply line 154, and the return line 156. If the second flow path 126 is active, the supply line 154 conveys the high-pressure gas refrigerant 120 from the compressor 106 through the inlet 150 of the reheat coil 148. The high-pressure gas refrigerant 120 then flows through the reheat coil 148 and exits through the outlet 152. The return line 156 conveys the high-pressure gas refrigerant 120 to the second discharge line 130. If the first flow path 124 is active, the high pressure gas refrigerant 120 traverses the valve 102 directly into the second discharge line 130. The flow of refrigerant in the reheat circuit 153 is therefore substantially stagnant. In this state, however, the reheat circuit 153 retains refrigerant for storage. Such storage avoids transferring refrigerant into the closed-conduit refrigerant circuit when the reheat circuit 153 becomes dormant (e.g., by evacuating the reheat circuit 153). FIG. 1 illustrates the valve 102 having the first flow path 124 active. Arrows representing refrigerant flow 116, 118, 120, 140 are placed along the closed-conduit refrigeration circuit 101; no refrigerant flow is depicted along the reheat circuit 153.
  • The reheat coil 148 has one or more heat exchange surfaces for transferring heat from the high-pressure gas refrigerant 120 to the cooled airflow 114 received from the evaporator 104. When the second flow path 126 is active, the high-pressure gas refrigerant flows 120 through the reheat coil 148. The cooled airflow 114 exits the reheat coil 148 as a conditioned air 158 that has been reheated to a desired temperature. When the first flow path 124 is active, i.e., the second flow path 126 is inactive, the flow of refrigerant through the reheat coil 148 is substantially stagnant, but remains in the reheat circuit 153. The conditioned air 158 exits the reheat coil 148 virtually unchanged from the cooled airflow 114.
  • In some embodiments, the HVAC system 100 includes a humidistat configured to actuate the valve 102 in response to a humidity measured in the conditioned air 158. In such embodiments, the humidistat may compare the humidity of the conditioned air 158 to a humidity threshold. If the measured humidity is greater than the humidity threshold, the closed-conduit refrigeration circuit 101 is directed to cool the conditioned air 158 below a target temperature and bring the conditioned air 158 back to approximately the target temperature 158. As part of this process, the humidistat actuates the valve 102 to activate the second flow path 126 and energize the reheat coil 148.
  • A refrigerant is disposed within the HVAC system 100. The refrigerant typically circulates through the closed-conduit refrigeration circuit 101, which includes the evaporator 104, the compressor 106, and the valve 102. In operation, the evaporator 104 receives the low-pressure liquid refrigerant 116 as a cold fluid from the expansion valve 144 via the refrigerant line 146. The cold, low-pressure liquid refrigerant 116 flows through the evaporator 104 and, while therein, absorbs heat from the return air 112. Such heat absorption is aided by the at least one evaporator fan 110 and the one or more heat-exchange surfaces of the evaporator 104. The at least one evaporator fan 110 enables a forced convection of return air 112 across the one or more heat-exchange surfaces of the evaporator 104. Absorption of heat by the cold, low-pressure liquid refrigerant 116 induces a conversion within the evaporator 104 from liquid to gas. The cold, low-pressure liquid refrigerant 116 therefore leaves the evaporator 104 as a warm, low-pressure gas refrigerant 118. Concomitantly, the return air 112 exits the evaporator 104 as the cooled airflow 114.
  • The warm, low-pressure gas refrigerant 118 traverses the suction line 108 and enters the compressor 106. The compressor 106 performs work on the warm, low-pressure gas refrigerant 118, producing a hot, high-pressure gas refrigerant 120 which exits the compressor 106 into the first discharge line 122. The hot, high-pressure gas refrigerant 120 travels through the first discharge line 122, and via the valve inlet, enters the valve 102. If a dehumidifying capacity of the reheat circuit 153 is not required, the valve 102 is activated with respect to the first flow pathway 124 and the hot, high pressure gas refrigerant 120 enters the second discharge line 130. Otherwise, if the dehumidifying capacity is needed, the valve 102 is activated with respect to the second flow pathway 126 and the hot, high pressure gas refrigerant 120 enters the supply line 154 of the reheat circuit 153. The humidistat, if present, may actuate the valve 102 in response to humidity measured in the conditioned air 158. The humidistat may compare the measured humidity against the humidity threshold, activating the valve 102 if the measured humidity is greater than the humidity threshold.
  • During activation of the first flow pathway 124, the hot, high-pressure gas refrigerant 120 traverses the second discharge line 130 to enter the microchannel condenser 132. While flowing through the microchannel condenser 132, the hot, high-pressure gas refrigerant 120 transfers heat to the non-conditioned air 136. Such heat transfer is assisted by the at least one microchannel condenser fan 134 and the one or more heat-exchange surfaces of the microchannel condenser 132. The at least one microchannel condenser fan 134 enables a forced convection of non-conditioned air 136 across the one or more heat-exchange surfaces of the microchannel condenser 132. Loss of heat from the hot, high-pressure gas refrigerant 120 induces a conversion within the microchannel condenser 132 from gas to liquid. The hot, high-pressure gas refrigerant 120 therefore leaves the microchannel condenser 132 as a warm, high-pressure liquid refrigerant 140. Concomitantly, the non-conditioned air 136 exits the microchannel condenser 132 as the warmed airflow 138. Meanwhile, proximate the evaporator 104, the cooled airflow 114 traverses the reheat coil 148 substantially unchanged and exits as the conditioned air 158 (i.e., the reheat coil 148 is dormant at this point). The air-handling subsystem (not explicitly shown) directs the conditioned air 158 back to the conditioned space.
  • During activation of the second flow pathway 126, the hot, high-pressure gas refrigerant 120 is redirected by the valve 102 to flow through the reheat circuit 153. More specifically, the hot, high-pressure gas refrigerant 120 travels through the supply line 154, enters the reheat coil 148 via the inlet 150, and exits the reheat coil 148 via the outlet 152. While flowing through the reheat coil 148, the hot, high pressure gas refrigerant 120 transfers heat to the cooled airflow 114 exiting the evaporator 104. Thus, the cooled airflow 114 is reheated. The hot, high pressure gas refrigerant 120, having lost thermal energy to the cooled airflow 114, travels to the second discharge line 130 via the return line 156. The hot, high pressure gas refrigerant 120 is then processed by the microchannel condenser 132 as described previously.
  • Reheat of the cooled airflow 114 may be necessary when a target temperature of the cooled airflow 114 is inadequate to condense of sufficient moisture out of the return air 112. The cooled airflow 114 may therefore have a humidity higher than the humidity threshold. Under such conditions, the evaporator 104 will cool the return air 112 below the target temperature. In response, the return air 112 achieves a dew point that corresponds to the humidity threshold (or below). Sufficient moisture condenses out of the return air 112, creating a cooled airflow 114 at or below the target humidity. The reheat coil 148 then heats the cooled airflow 114 to the target temperature. The conditioned air 158 exits the reheat coil 148 at the target temperature and at or below the humidity threshold. The air-handling subsystem directs the conditioned air 158 back to the conditioned space.
  • Referring back to the closed-conduit refrigeration circuit 101, the warm, high-pressure liquid refrigerant 140 exits the microchannel condenser 132 and flows through the liquid line 142 to reach the expansion valve 144. The expansion valve 144 lowers a pressure of the warm, high-pressure liquid refrigerant 140 passing therethrough. Such lowering of pressure simultaneously lowers a temperature of the warm, high-pressure liquid refrigerant 140. The expansion valve 144 therefore produces the cold, low-pressure liquid refrigerant 116 from the warm, high-pressure liquid refrigerant 140. The cold, low-pressure liquid refrigerant 116 is circulated into the evaporator 104 via the refrigerant line 146, thereby completing the closed-conduit refrigeration circuit 101. It will be appreciated that the closed-conduit refrigeration circuit 101 circulates the refrigerant to allow repeated processing by the evaporator 104, the compressor 106, the microchannel condenser 132, and the first expansion valve 144. Such repeated processing enables the HVAC system 100 to continuously produce the cooled airflow 114. Control of the reheat circuit 153 by the valve 102 (along with initial cooling of the return air 112 below a target temperature to adequately remove moisture) then allows the HVAC system 100 to regulate the moisture content of the conditioned air 158 as needed while producing the conditioned air 158 at approximately the target temperature.
  • Now referring primarily to FIG. 2A, a schematic diagram is presented of a heating, ventilating, and air conditioning (HVAC) system 200 having a valve that includes a heat-pump reversing valve 203, according to an illustrative embodiment. The HVAC system 200 of FIG. 2A is similar in features and operation to the HVAC system 100 of FIG. 1. Features analogous to both FIGS. 1 and 2A are related via coordinated numerals that differ in increment by a hundred. FIG. 2A depicts the heat-pump reversing valve 203 as having a 4-way configuration. This depiction, however, is not intended as limiting. Other configurations are possible.
  • Like the valve 102 of FIG. 1, the heat-pump reversing valve 203 includes a first flow pathway 224 that, when active, fluidly-couples a first discharge line 222 to a second discharge line 230. The heat-pump reversing valve 203 also includes a second flow pathway 228. However, unlike the valve 102 of FIG. 1, the second flow pathway 228 fluidly-couples the heat-pump reversing valve 203 to a suction line 208 line via a secondary suction line 209 (i.e., when active). The first flow pathway 224 and the second flow pathway 228 are operable to convey simultaneous and independent refrigerant flows through the heat-pump reversing valve 203. Such simultaneous flows are not present in the valve 102 of FIG. 1. (In FIG. 1, the first flow path 124 and the second flow path 126 of the valve 102 are operationally exclusive.) Activation of the first flow pathway 224 and the second flow pathway 228 of the heat-pump reversing valve 203 correspond to a first position of the heat-pump reversing valve 203.
  • The heat-pump reversing valve 203 also includes a third flow pathway 225 and a fourth flow pathway 229. FIG. 2B presents, in detail view, a schematic diagram of the heat-pump reversing valve 203 with the third flow pathway 225 and the fourth flow pathway 229 active. The third flow pathway 225, when active, fluidly-couples the first discharge line 222 to the supply line 254. The fourth flow pathway 229, when active, fluidly-couples the alternate suction line 209 to the second discharge line 230. The third flow pathway 225 and the fourth flow pathway 229 are operational to convey simultaneous and independent refrigerant flows through the heat-pump reversing valve 203. Activation of the third flow pathway 225 and the fourth flow pathway 229 correspond to a second position of the heat-pump reversing valve 203. When the second position is present in the heat-pump reversing valve 203, flow pathways corresponding to the first position are precluded and vice versa.
  • In some embodiments, the HVAC system 200 includes a first check valve 255 fluidly-coupled to the supply line 254 and oriented to prevent refrigerant from flowing towards the heat-pump reversing valve 203. The first check valve 255 is operable to partition the supply line 254 into a first portion 257 and a second portion 259. The first portion 257 of the supply line fluidly 254 fluidly couples the heat-pump reversing valve 203 to the first check valve 255. The second portion 259 of the supply line 254 fluidly couples the first check valve 255 to an inlet 250 of a reheat coil 248.
  • In some embodiments, the HVAC system 200 also includes a second check valve 231 fluidly-coupled to the second discharge line 230 between the heat-pump reversing valve 203 and a junction 260 formed by a return line 256 and the second discharge line 230. The junction 260 fluidly-couples the second discharge line 230 to the return line 256. In such embodiments, the second check valve 231 is oriented to prevent refrigerant from flowing towards the heat-pump reversing valve 203. The second check valve 231 is operable to partition the second discharge line 230 into a first portion 233 and a second portion 235. The first portion 233 of the second discharge line 230 fluidly couples the heat-pump reversing valve 203 to the second check valve 231. The second portion 235 of the second discharge line 230, which includes the junction 260, fluidly couples the second check valve 231 to a microchannel condenser 232. By means of the junction 260, the second check valve 231 is also fluidly-coupled to the return line 256.
  • The HVAC system 200 of FIG. 2A (and FIG. 2B) functions analogously to the HVAC system 100 of FIG. 1: The heat-pump reversing valve 203 serves to selectively control a flow of refrigerant into the reheat coil 248, which may also serve as refrigerant storage. During operation, a compressor 206 draws a warm, low-pressure gas refrigerant 218 from the suction line 218 and exhausts a hot, high-pressure gas refrigerant 220 into the first discharge line 222. Draw at the suction line 218 extends into the alternate suction line 209 where refrigerant, if present, is pulled into the compressor 206. When the heat-pump reversing valve 203 is in the first position, draw at the suction line 218 also extends into the second flow pathway 228 and the first portion 257 of the supply line 254. The first check valve 255, however, prevents refrigerant from flowing into the first portion 257 of the supply line 254 from the second portion 259. Thus, when in the first position, the heat-pump reversing valve 203 enables the HVAC system 200 to store refrigerant in a reheat circuit 253 defined, in part, by the reheat coil 248, the second portion 259 of the supply line 254, and the return line 256.
  • Concomitantly, the hot, high-pressure gas refrigerant 220 from the compressor 206 is able to traverse the first discharge line 222 and the heat-pump reversing valve 203 to enter the microchannel condenser 232 via the second discharge line 230. The second check valve 231 is oriented to allow refrigerant flow towards the microchannel condenser 232. It will be appreciated that the first position of the heat-pump reversing valve 203 corresponds to the reheat circuit 253 being dormant, but a closed-conduit refrigeration circuit 201 being active. FIG. 2A illustrates the heat-pump reversing valve 203 constraining flow to the closed-conduit refrigeration circuit 201. Arrows representing refrigerant flow 216, 218, 220, 240 are placed along the closed-conduit refrigeration circuit 201; no refrigerant flow is depicted along the reheat circuit 253.
  • If a dehumidifying capability of the reheat circuit 253 is required, the heat-pump reversing valve 203 switches from the first position to the second position. Upon switching to the second position, the first flow pathway 224 and the second flow pathway 228 become inactive and the third flow pathway 225 and the fourth flow pathway 229 become active. The third flow pathway 225, however, shares the same valve inlet as the first flow pathway 224. Thus, upon switching into the second position, the hot high-pressure gas refrigerant 220 stops flowing into the second discharge line 230 and starts flowing into the supply line 254. The reheat coil 248 therefore begins receiving a source of heat. Similarly, the fourth flow pathway 229 shares the same valve inlet as the second flow pathway 226. Due to draw from the compressor 206, refrigerant is drained from a continuous pathway defined, in part, by the first portion 233 of the second discharge line 230, the fourth flow pathway 229, the alternate suction line 209, and the suction line 208. The second check valve 231, however, prevents refrigerant from flowing into the first portion 233 of the second discharge line 230 from the second portion 235.
  • It will be appreciated that the second portion 259 of the supply line 254, by virtue of its length downstream of the first check valve 255, influences a storage capacity of the reheat circuit 253. Thus, physical parameters of the second portion 259 (e.g., inside diameter and length) may be modified to optimize the storage capacity of the reheat circuit 253. Such modification may be advantageous over modifying other physical parameters of the reheat circuit 253, such as those of the reheat coil 248. For example, and without limitation, a size of reheat coil 248 may be selected to ensure that sufficient conditioned air 258 is produced during operation and that such air exhibits a desired temperature and humidity. However, if the size of the reheat coil 248 is modified to alter the storage capacity, reheat performance of the reheat circuit 253 may be negatively impacted.
  • According to an illustrative embodiment, a method of regulating humidity in air conditioned by a heating, ventilating, and air conditioning (HVAC) system includes the step of moving conditioned air across a reheat coil. The method also includes the step of, while moving the conditioned air, actuating a valve having a first position and a second position into the second position to start a flow of refrigerant through the reheat coil. In the second position, the valve establishes a first flow pathway between a discharge line and a supply line to the reheat coil. The method involves the step of, while moving the conditioned air, actuating the valve into the first position to stop the flow of refrigerant through the reheat coil. In the first position, the valve establishes a second flow pathway between the first discharge line and a second discharge line. The method also involves the step of storing a refrigerant in the reheat coil when the valve is in the first position. In some embodiments, the refrigerant may also be stored in a supply line fluidly-coupled to the reheat coil and a return line fluidly-coupled to the reheat coil. In some embodiments, the step of actuating the valve into the second position and the step of actuating the valve into the first position includes using a humidistat. In some embodiments, the valve includes a bleed-port reheat valve. In other embodiments, valve includes a heat-pump reversing valve.
  • In some embodiments, the valve includes a heat-pump reversing valve and may include one or more devices to block fluid flow (e.g., check valves, solenoid valves, hydraulic valves, etc.). In such embodiments, the method further includes the step of blocking refrigerant flow towards the heat-pump reversing valve along the second discharge line while the heat-pump reversing valve is in the second position. In the second position, the heat-pump reversing valve further establishes fluid communication between a suction line and the second discharge line. The method also includes blocking refrigerant flow towards the heat-pump reversing valve along the supply line while the heat-pump reversing valve is in the first position. In the first position, the heat-pump reversing valve further establishes fluid communication between the suction line and the supply line.
  • In some embodiments, the method further includes the step of measuring a humidity of conditioned air relative to a reference humidity. The method also includes the step of actuating the valve into the second position if the measured humidity is greater than the threshold humidity and the valve is in the first position. The method also includes the step of actuating the valve into the first position if the measured humidity is less than or equal to the threshold humidity and the valve is in the second position.
  • Now referring primarily to FIG. 3, a flow chart is presented of an illustrative method 300 for regulating humidity in air conditioned by a heating, ventilating, and air conditioning (HVAC) system. The method 300 includes the step 302 of moving conditioned air across a reheat coil. The method 300 also includes the step 304 of measuring a humidity of conditioned air relative to a reference humidity. The step of measuring the humidity may include a decision, represented by interrogatory 306, of determining if the measured humidity is greater than the humidity threshold. If the measured humidity is greater than the humidity threshold, the method 300 proceeds to the step 308 of actuating a valve into a second position to start a flow of refrigerant through the reheat coil. Such actuation occurs while moving the conditioned air. In the second position, the valve establishes a first flow pathway between a discharge line and a supply line to the reheat coil. The method 300 then returns to the step 304 of measuring the humidity.
  • If the measured humidity is not greater than the humidity threshold, the method 300 may include a decision, represented by interrogatory 310, of determining if the valve is in the second position. If the valve is in the second position, the method 300 proceeds to the step 312 of actuating the valve into a first position to stop the flow of refrigerant through the reheat coil. Such actuation also occurs while moving the conditioned air. In the first position, the valve establishes a second flow pathway between the first discharge line and a second discharge line. The method 300 then continues to the step 314 of storing a refrigerant in the reheat coil when the valve is in the first position. After the step 314 of storing the refrigerant, the method 300 returns to the step 304 of measuring the humidity. If the valve is not in the second position, the method 300 returns to the step 302 of moving the conditioned air.
  • In some embodiments, the refrigerant may also be stored in a supply line fluidly-coupled to the reheat coil and a return line fluidly-coupled to the reheat coil. In some embodiments, the step of actuating the valve into the second position and the step of actuating the valve into the first position includes using a humidistat. In some embodiments, the valve includes a bleed-port reheat valve. In other embodiments, valve includes a heat-pump reversing valve.
  • Although the present invention and its advantages have been disclosed in the context of certain illustrative, non-limiting embodiments, it should be understood that various changes, substitutions, permutations, and alterations can be made without departing from the scope of the invention as defined by the appended claims. It will be appreciated that any feature that is described in connection to any one embodiment may also be applicable to any other embodiment.
  • It will be understood that the benefits and advantages described above may relate to one embodiment or may relate to several embodiments. It will further be understood that reference to “an” item refers to one or more of those items.
  • The steps of the methods described herein may be carried out in any suitable order or simultaneous where appropriate. Where appropriate, aspects of any of the examples described above may be combined with aspects of any of the other examples described to form further examples having comparable or different properties and addressing the same or different problems.
  • It will be understood that the above description of the embodiments is given by way of example only and that various modifications may be made by those skilled in the art. The above specification, examples, and data provide a complete description of the structure and use of exemplary embodiments of the invention. Although various embodiments of the invention have been described above with a certain degree of particularity, or with reference to one or more individual embodiments, those skilled in the art could make numerous alterations to the disclosed embodiments without departing from the scope of the claims.

Claims (12)

1. A method of regulating humidity in air conditioned by a heating, ventilating, and air conditioning system, the method comprising:
moving conditioned air across a reheat coil;
while moving the conditioned air, actuating a valve having a first position and a second position into the second position to start a flow of refrigerant through the reheat coil;
while moving the conditioned air, actuating the valve into the first position to stop the flow of refrigerant through the reheat coil;
storing a refrigerant in the reheat coil when the valve is in the first position;
wherein, in the second position, the valve establishes a first flow pathway between a first discharge line and a supply line to the reheat coil; and
wherein, in the first position, the valve establishes a second flow pathway between the first discharge line and a second discharge line.
2. The method of claim 1, wherein the valve comprises a bleed-port reheat valve.
3. The method of claim 1, wherein the valve comprises a heat-pump reversing valve.
4. The method of claim 1, wherein the valve comprises a heat-pump reversing valve and the method further comprises:
blocking refrigerant flow towards the heat-pump reversing valve along the second discharge line while the heat-pump reversing valve is in the second position;
blocking refrigerant flow towards the heat-pump reversing valve along the supply line while the heat-pump reversing valve is in the first position;
wherein, in the second position, the heat-pump reversing valve further establishes fluid communication between a suction line and the second discharge line; and
wherein, in the first position, the heat-pump reversing valve further establishes fluid communication between the suction line and the supply line.
5. The method of claim 1, further comprising:
measuring a humidity of conditioned air relative to a reference humidity;
actuating the valve into the second position if the measured humidity is greater than the threshold humidity and the valve is in the first position; and
actuating the valve into the first position if the measured humidity is less than or equal to the threshold humidity and the valve is in the second position.
6. The system of claim 1, wherein the step of actuating the valve into the second position and the step of actuating the valve into the first position comprises using a humidistat.
7. A heating, ventilating, and air conditioning system for regulating a moisture content of conditioned air, the system comprising:
a closed-conduit refrigeration circuit having an evaporator, a compressor, a valve, and a microchannel condenser,
wherein the evaporator is fluidly-coupled to the compressor through a suction line,
wherein the compressor is fluidly-coupled to the valve through a first discharge line, and
wherein the valve is fluidly-coupled to the microchannel condenser through a second discharge line;
a reheat coil proximate the evaporator, the reheat coil having an inlet and an outlet, the inlet fluidly-coupled to the valve through a supply line, the outlet fluidly-coupled to the second discharge line through a return line; and
wherein the valve is configured to selectively control a flow of refrigerant into the reheat coil.
8. The system of claim 7, wherein the valve comprises a bleed-port reheat valve.
9. The system of claim 7, wherein the valve comprises a heat-pump reversing valve.
10. The system of claim 7, wherein the valve comprises a heat-pump reversing valve and the system further comprises:
a first check valve fluidly-coupled to the supply line and oriented to prevent refrigerant from flowing towards the heat-pump reversing valve; and
a second check valve fluidly-coupled to the second discharge line between the heat-pump reversing valve and a junction formed by the return line and the second discharge line, the second check valve oriented to prevent refrigerant from flowing towards the heat-pump reversing valve.
11. The system of claim 7, further comprising a refrigerant disposed therein.
12. The system of claim 7, further comprising a humidistat configured to actuate the valve in response to humidity measured in air conditioned by the system being greater than a humidity threshold.
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US11143421B2 (en) 2019-05-31 2021-10-12 Rheem Manufacturing Company Sequential hot gas reheat system in an air conditioning unit

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WO2018022638A1 (en) * 2016-07-25 2018-02-01 Carrier Corporation Dehumidification system for heat pump
US10955149B2 (en) 2016-07-25 2021-03-23 Carrier Corporation Dehumidification system for heat pump
US11143421B2 (en) 2019-05-31 2021-10-12 Rheem Manufacturing Company Sequential hot gas reheat system in an air conditioning unit

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