US20080173035A1

US20080173035A1 - Split system dehumidifier

Info

Publication number: US20080173035A1
Application number: US11/656,270
Authority: US
Inventors: Daniel D. Thayer; David E. Beal
Original assignee: Individual
Current assignee: Individual
Priority date: 2007-01-22
Filing date: 2007-01-22
Publication date: 2008-07-24

Abstract

Mini, split-system dehumidifier that provides three modes of operation: heating and dehumidification, cooling and dehumidification, and dehumidification only. The dehumidifier maintains a set temperature of the supply air by controlling the amount of heat of rejection at the primary condenser that is cycled back into the supply air.

Description

BACKGROUND INFORMATION

1. Field of the Invention
The invention relates to the field of heating, ventilation, and air-conditioning. More particularly, the invention relates to dehumidification.
2. Description of the Prior Art
Traditionally, dehumidification of an indoor space is a by-product of the air-conditioning process. Air is cooled to below the dew point, whereby moisture naturally drops out and is then collected and drained off. The more widespread need for dehumidification of indoor spaces, independently of cooling, is relatively recent, and primarily caused by increased use of water in indoor spaces and/or the increasing tightness of building envelopes. The prevalence of indoor pools, spas and hot tubs has grown in recent decades, as have health clubs, locker rooms, physical therapy offices, and other enterprises that require the use of large quantities of water. The presence of a large quantity of water in an enclosed space and the reduction in infiltration/exfiltration creates a need for dehumidification, independently of cooling.
Indoor pool facilities, in the past, have simply exhausted a large quantity of indoor air and replaced it with drier outdoor air, as a means of controlling humidity. The energy costs related to conditioning the make-up air have made this practice progressively more expensive and undesirable. Central, ducted dehumidification systems are available, but they are expensive. An conventional central dehumidification system includes the evaporator, reheat condenser and compressor. A duct system distributes the dehumidified air to one or more rooms or spaces. A remote air-cooled condenser for cooling is a standard option and includes a condenser and a condenser fan. A water-cooled condenser is also an option in such a system. The costs of retrofitting such a system into an existing facility, especially residential pool facilities, that was not constructed originally for a ducted system can be prohibitive. The space requirements for retrofitting a ducted system may be unavailable, without extensive and expensive installation work.
It is not only commercial and pool facilities that have trouble with humidity. Residential use of water for cooking, laundry, showering and bathing, dishwashing, etc. has also increased over the years, thereby putting increased moisture into the enclosed air space. The tighter building envelopes of modern residential structures have compounded the problem, by reducing the amount of infiltration of outdoor air. As a result, humidity levels can rise to uncomfortable and unhealthful levels, causing structural problems in buildings and health problems in people due to increased presence of mold. Thus, the need for humidity control in residential structures has also been increasing. As with commercial structures, the cost of installing a central, ducted dehumidification system in a new structure is high, and the cost of retrofitting an existing structure is often prohibitive.
Conventional portable dehumidifiers are known and are frequently used to dehumidify a basement or a single room. The portable dehumidifier is a single unit that contains an evaporator, a condenser, a compressor, along with a container for collecting the water extracted from the air. This type of dehumidifier has several disadvantages, however. The extracted water must be removed periodically, either manually or via some drain system. Furthermore, the entire unit operates within the space requiring dehumidification. The heat generated by converting water vapor to liquid is thus expelled into the space. This is often undesirable.
Conventional split system air conditioners or heat pumps are known. One style of split system features a small non-ducted indoor section. Such systems are known as “mini-splits”. These systems have the advantage that they require only a relatively small wall unit to be mounted in the space to be dehumidified. The refrigeration lines are connected to a condenser that is located outside the building, thus the name “split system.” The disadvantage of such systems is that dehumidification is done only when cooling is called for. Thus, they cannot be used to dehumidify the indoor space when heating or temperature-neutral conditioning of the air is desired. Some claim dehumidification capabilities, but achieve this by reducing fan speed, still resulting in overcooling, though at a slower rate, while also increasing energy consumption.
What is needed, therefore, is a dehumidification system that enables humidity control independently of cooling. What is further needed is such a system that is easily and cost-effectively installed and as energy-efficient as possible.

BRIEF SUMMARY OF THE INVENTION

The invention is a split-system heating-cooling-dehumidifying unit that enables humidity control independently of cooling and that is easily and cost-effectively installed. For reasons of simplicity only, the system shall be referred to hereinafter simply as a “dehumidifier system.” The dehumidifier system comprises an indoor section or unit and a condensing or outdoor unit and operates in three dehumidification modes and a stand-by mode. The dehumidification modes are: neutral air (dehumidification only, that is, without effecting a change in ambient air temperature of the indoor space); heating and dehumidification; and cooling and dehumidification. In stand-by mode, only the supply-air fan in the indoor unit is energized, providing circulation of air for mixing and sensing of temperature and humidity.
In neutral air mode, the humidistat calls for dehumidification, while the thermostat calls for neither heating nor cooling. A calculated amount of heat of rejection is returned into the supply air to maintain the temperature of the supply air, without overheating the space, while any remaining heat is rejected by the outdoor condenser to the outdoors. In this mode, the evaporator, the reheat condenser, and the supply-air fan of the indoor unit are energized, as are the compressor, the condensing coil, and condenser fan of the outdoor unit. The calculated amount of heat of rejection is recycled back into the indoor unit via the reheat condenser. In cooling mode, the condensing coil, the fan, and the compressor of the outdoor unit, and the evaporator and supply-air fan of the indoor unit are energized. The heat of rejection is expelled via the outdoor condensing coil and fan, and the refrigerant bypasses the reheat condenser in the indoor unit. In heating mode, the humidistat calls for dehumidification and the thermostat calls for heat. All of the heat of rejection is recycled into the supply air. The evaporator, the reheat condenser and the supply-air fan in the indoor unit are energized, as is the compressor of the outdoor unit. The refrigerant bypasses the condensing coil in the outdoor unit and the heat in the refrigerant is applied to the reheat condenser in the indoor unit. If an auxiliary external heat source is incorporated into the dehumidifier system, it will be energized as needed to maintain the supply air at the desired temperature.
The dehumidifier system according to the invention comprises an indoor unit and an outdoor unit, but, unlike conventional central dehumidification systems, the compressor of the present invention is placed in the outdoor unit. The indoor unit includes an evaporator coil, a refrigerant receiver, an expansion valve, a reheat condenser, and a supply-air fan, and is provided as a non-ducted cabinet for mounting on a wall or as a ducted system. The outdoor unit includes a condensing coil, a condenser fan, a controller for controlling the speed of the condenser fan when both condensers are energized or for low ambient control in cooling, and a compressor. Alternatively, the condenser may be water-cooled, rather than air-cooled. In this case, the condenser fan is eliminated and the condenser encased in a water jacket that is coupled into a water loop circulation system. One or more modulating valves are provided for varying the flow of water or coolant over the water cooled condenser when both condensers are energized. The dehumidifier system also includes the conventional humidity and temperature sensors and controls, such as a humidistat and thermostat, and various valves to selectively energize or isolate the various coils and process controls. A conventional two-line set or a three-line set is used to connect the indoor unit with the outdoor unit through the envelope of the building or with the water cooled condenser.
Optionally, an electric heater or alternate auxiliary heating coil may be incorporated into the indoor unit, to provide additional heating capacity for a stand-alone unit that is the sole source of heat for an indoor space.
The dehumidifier system is energy-efficient, because it recovers heat, also referred to as the heat of rejection. Both sensible heat and the latent heat of evaporation are initially removed from the supply air in the cooling and drying process, but cycled back into the supply air, whenever the unit is in heating or neutral air (dehumidification only) mode. The ductless dehumidifier system is ideally suited for retrofit applications and installation, wherever space and/or budget limitations make the use of conventional ducted systems prohibitive. A ducted version of the indoor unit may be provided to allow for installation above a dropped ceiling, in a closet or similar location not directly in the space to be conditioned. The dehumidifier system according to the invention can also be added to an existing HVAC system to provide additional dehumidification and cooling capacity for systems that do not meet the load.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is described with reference to the accompanying drawings. In the drawings, like reference numbers indicate identical or functionally similar elements. The drawings are not necessarily to scale.

FIG. 1 is a schematic representation of the dehumidification system according to the invention, showing the indoor section, the condensing unit, and the two-line set.

FIG. 2 is a wiring diagram of the dehumidifier system of FIG. 1.

FIG. 3 illustrates a second embodiment of the condensing unit, showing a water-cooled condenser.

FIG. 4 illustrates a second embodiment of the indoor section, showing an auxiliary heat source.

DETAILED DESCRIPTION OF THE INVENTION

The present invention will now be described more fully in detail with reference to the accompanying drawings, in which the preferred embodiments of the invention are shown. This invention should not, however, be construed as limited to the embodiments set forth herein; rather, they are provided so that this disclosure will be complete and will fully convey the scope of the invention to those skilled in the art.
FIG. 1 is a schematic illustration of a dehumidifier system 100 according to the invention. The dehumidifier system 100 provides three modes of operation plus a stand-by mode: heating and dehumidifying; cooling and dehumidifying; and dehumidifying only. The dehumidifier system 100 comprises an indoor section 10, a condensing unit 40, and process controls 70, which include a thermostat 76 and a humidistat 78. Other process controls are shown primarily in FIGS. 2 and 3. As shown in FIG. 1, the indoor section 10 includes an evaporator 20, a refrigerant receiver 28, an expansion device 24, hereinafter referred to as an expansion valve, optionally a sensor for external equalization of the thermal expansion valve (TXV) 26, a reheat condenser 30, and a supply-air fan 32. In the embodiment shown, the supply fan is a draft fan, but it is understood, that the fan may be placed upstream of the evaporator 20. The condensing unit 40 includes a compressor 42, a condensing coil 60, a condenser fluid pump 50, such as a fan or a coolant pump, and a refrigerant sensor 72 or 74 for providing flow of the heat-exchange medium over the condenser 60. The outdoor condensing coil 60 is also referred to herein as a “primary” condenser. In the embodiment shown, a refrigerant or heat-exchange fluid is pumped through a two-line conduit system. A first line L1 is the conduit for the refrigerant from the condensing unit 40 to the indoor section 10, and a second line L2 is the conduit for the refrigerant from the indoor section 10 back to the condensing unit 40. A plurality of valves controls the modes of operation. Included in this plurality of valves are: a first valve V1 between the compressor 42 and the outdoor condensing coil 60; a second valve V2 between the compressor 42 and the indoor section 10; a third valve V3 between the condensing unit 40 and the reheat condenser 30; and a fourth valve V4 between the condensing unit 40 and the expansion valve 24. In a preferred embodiment, the valves V1-V4 are solenoid valves, although other flow control means may be used, such as motorized actuators. Check valves V10 and V12 are provided at the outlets of the condensers 60 and 30, respectively. First valve V1 and check valve V10 cooperate to isolate the outdoor condenser 60 from the refrigeration circuit and third valve V3 and check valve V12 cooperate to isolate the reheat condenser 30 from the circuit. The refrigerant receiver 28 is provided upstream of the TXV 24 in order to compensate for varying refrigerant charge requirements in the three dehumidification modes.
FIG. 2 is a wiring diagram of the dehumidifier system 100. These diagrams also illustrate various process controls 70, such as valves, sensors, and switches.
The dehumidifier system 100 is a split-system that is intended to dehumidify, and/or heat or cool a single space or area as needed. In a ductless system, the indoor section 10 is a spatially small unit that may be mounted on the wall in the area to be dehumidified; in a ducted system, the indoor section 10 is mounted on the floor, ceiling, or wall and provided with connections for return RA and/or supply air SA ducts 14 to conduct air from and to the space or an existing HVAC system. The condensing unit 40 is installed outside and expels sensible heat energy from the refrigerant to the ambient environment, that is, heat of rejection extracted from supply air including both sensible heat and latent heat from the conversion of water vapor to liquid. The condensing unit 40 also contains the compressor 42, which generates noise, and for reasons of comfort is ideally installed outside the space to be dehumidified.
The direction of the airflow through the indoor section 10 is indicated by the broad arrows in FIG. 1, labeled SA and RA. For simplicity sake, the airflow through the indoor section referred to hereinafter as SA refers to the air that circulates through the indoor section 20 and back into the space, that is, the initially humid air and the dehumidified air. The supply air SA is drawn across the evaporator coil 20 where it is dehumidified and, in the process of dehumidification, also cooled. The dehumidified air is then drawn across the reheat condenser 30, before being reintroduced into the space. Depending on the mode of operation, the reheat condenser 30 reheats the dehumidified supply air SA to approximately the same temperature as it was prior to dehumidification, heats it, or has no effect on it, allowing the air to remain colder, as called upon by process controls, such as a thermostat. The various modes of operation are described below.
In the heating and dehumidification mode, the first valve V1 and the fourth valve V4 are closed; the second valve V2 and the third valve V3 are open. With this configuration, the refrigerant flows from line L2 into the compressor 42, through the second valve V2 into the indoor section and through the third valve V3 into the reheat condenser 30, where heat from the refrigerant is used to warm the dehumidified supply air SA. A heating priority switch 79 is included as a process control 70. When the heating priority switch 79 is open, the compressor 42 runs only on a call for dehumidification, even if there is a call for heating. Auxiliary heating elements or other heating systems may be relied upon to meet the heating load demands. Closing the heating priority switch 79 allows the compressor 42 to run on a call for heat, with or without a call for simultaneous dehumidification. An auxiliary heating element 12, shown in FIG. 4, is incorporated into the indoor section downstream of the reheat condenser 30, to provide a second stage of heating.
In the cooling and dehumidification mode, the first valve V1 and the fourth valve V4 are open and the second valve V2 and the third valve V3 are closed. In this configuration, the refrigerant flows from the second line L2 into the compressor 42, through the first valve V1 into the condensing coil 60, where heat is expelled to the surroundings. The refrigerant then flows from the condensing coil 60 into the indoor section 10, bypasses the reheat condenser 30 and flows into the expansion valve 24 and into the evaporator coil 20.
In the dehumidification only mode, the first valve V1 and the third valve V3 are open and the second valve V2 and the fourth valve V4 are closed. With this configuration, the refrigerant flows in the second line L2 into the compressor and into the condensing coil 60 where a portion of the extracted heat is expelled, and then into the indoor section 10 into the reheat condenser 30, where the remaining heat is used to heat the dehumidified supply air SA, and then through the expansion valve 24 into the evaporator 20, where dehumidification of the humid supply air SA takes place. The process controls 70 include optionally a pressure control 72 or a temperature control 74, which directly controls the rate of flow of the heat-exchange medium over the condenser 60. The typical configuration of the dehumidifier 100 uses air as the heat-exchange medium and a condenser fan as the fluid pump 50. Depending on the amount of heat to be extracted from the refrigerant and rejected from the system, the speed of the condenser fan 50 is sped up or slowed down. For example, with a low fan speed, less heat is extracted from the refrigerant, and more heat is provided for heating the supply air SA in the indoor section.
FIG. 3 illustrates a second embodiment of the condensing unit, which is a water-cooled condensing unit 40′. The heat-exchange medium is a liquid, typically water, in a water circulation loop 80 that includes a water jacket 82 around the condenser 60. Although the water-cooled condensing unit 40′ may be located indoors or outdoors, the condenser 60 is identical in function to the primary condenser described above. A motor-driven pump 50 circulates cooling water through said water circulation loop 80. The process controls 70 include optionally a pressure control 72 or a temperature control 74, which directly controls a modulating valve or valves 84 controlling the rate of flow of the heat-exchange medium over the condenser 60. Alternatively, the process controls 72 or 74 control the speed of the fluid pump 50. In either case, depending on the amount of heat to be extracted from the refrigerant and rejected from the system, the flow of fluid through the modulating valve is sped up or slowed down. For example, with lower flow rate of flow of the heat-exchange medium, less heat is extracted from the refrigerant and more heat is provided for heating the supply air SA in the indoor section 10.
FIG. 4 illustrates an second embodiment 10′ of the indoor section, having the auxiliary heat source 12. In some cases, the dehumidification system 100 will be used as the sole source of heating-cooling-dehumidification of a small indoor space. In such cases, the auxiliary heat source 12 provides additional heat, as called for by the thermostat 76 to heat the indoor space.
Process Control. A number of the process controls 70 for controlling the heating and dehumidification/cooling and dehumidification/dehumidification only processes have been introduced above. As described above, the valves V1-V4 open and close, based on calls for dehumidification, cooling, and or heating. In stand-by mode, neither heating, nor cooling, nor dehumidification is called for, but the supply-air fan 32 runs to provide circulation. The compressor 42 is energized on a call for dehumidification or for cooling. The condenser fan 50 in the condensing unit 40 is not energized on a call for heat, but is energized on a call for dehumidification only, dehumidification and cooling, or cooling. Cooling mode is activated by a call for cooling or by a call for dehumidification and cooling. In the latter case, both the thermostat 76 and the humidistat 78 have called for system actuation. The positions of valves V1-V4 control the mode of operation, while the rate of flow of the heat-exchange medium over the condenser 60 in the condensing unit 40 determines the amount of heat that is rejected or introduced into the supply air SA via the reheat condenser 30. The control 72 or 74 is located upstream of the check valve V10, thus ensuring that whenever the condenser 60 is isolated, i.e., not energized, the condenser fan 50 is also automatically not energized.
The process control 72 or 74 directly controls the operating speed of the fluid pump 50 or the position of the modulating valve 84. This in turn controls the rate of flow of the heat-exchange medium over the condenser 60. A preferred embodiment uses refrigerant head pressure, which is measured by the head-pressure control 72. Head pressure indicates the condition of refrigerant as it comes off the condensing coil 60, thus indicating the amount of heat rejected there. The two condensing coils 30 and 60, and the evaporator 20 are matched, thus, knowing the properties and the temperature of the refrigerant, and through empirical testing, it is possible to determine the appropriate settings of the fluid pump 50 or modulating valves 84 to control the amount of heat to be recycled into the reheat condenser 30 to offset the cooling of the dehumidified supply air SA. The setting for the refrigerant head pressure control 72 is pre-determined, based on calculations and testing to balance sensible heat loss at the evaporator 20 with heat gain at the reheat condenser coil 30, whenever both condensers 30 and 60 are energized. In the following examples, the fluid pump 50 is a variable-speed condenser fan. When operating on a call for dehumidification only, that is, without heating or cooling, the speed of the condenser fan 50 is controlled to ensure that an appropriate amount of heat is left in the refrigerant to achieve the desired results at the reheat condenser 30. Alternatively, instead of the controlling the speed of the condenser fan 50 based on head pressure, a temperature-based control may be provided, based on the temperature of the refrigerant, as measured by the temperature control 74. In this case, the speed of the condenser fan 50 is directly controlled by the refrigerant temperature control 74 in response to the temperature of the refrigerant as determined through calculation and testing. Thus, the condenser fan speed is decreased when the temperature of the refrigerant falls below the low limit and increased if the temperature rises above the high limit. Either method of controlling the rate of flow of the heat-exchange medium over the condenser 60 is also used with the water-cooled unit 40′. In this case, the outdoor air and the condenser fan 50 are replaced by the water circulation loop 80. The water or other coolant in the water circulation loop 80 is driven by the fluid pump 50, which is a liquid pump. The flow of coolant is decreased or increased by modulating the valves 84 or the speed of the fluid pump 50, depending on the pressure or temperature of the refrigerant to achieve the desired heat gain at the reheat condenser coil 30.
It is understood by those skilled in the art, that the indoor section 10 may be packaged with the condensing unit 40.
It is understood that the embodiments described herein are merely illustrative of the present invention. Variations in the construction of the dehumidifier system according to the invention may be contemplated by one skilled in the art without limiting the intended scope of the invention herein disclosed and as defined by the following claims.

Claims

1: Dehumidification apparatus comprising:

an indoor section including an evaporator, a reheat condenser, and a supply-air fan;

a condensing unit that includes a compressor, a primary condenser, and a fluid pump that provides a flow of heat-exchange medium over said primary condenser;

a refrigeration circuit containing refrigerant that flows through said indoor section and said condensing unit, wherein said refrigerant selectively flows through said primary condenser and/or said reheat condenser;

a first process control for selectively enabling three modes of operation, said modes of operation including a dehumidification-and-heating mode, a dehumidification-and-cooling mode, and a dehumidification-only mode;

a second process control for directly adjusting a rate of flow of said heat-exchange medium, based on a property of said refrigerant at said primary condenser;

wherein, in said dehumidification-only mode, said second process control apportions heat of rejection to said reheat condenser and said primary condenser as required to maintain a temperature of supply air to said indoor space.

2: The dehumidification apparatus of claim 1, wherein said property of said refrigerant is head pressure and wherein said second process control includes a head-pressure sensor for measuring said head pressure and a controller for adjusting said rate of flow of said heat-exchange medium, based on said head pressure.

3: The dehumidification apparatus of claim 1, wherein said property of said refrigerant is temperature and wherein said second process control includes a temperature sensor for measuring said temperature and a controller for adjusting said rate of flow of said heat-exchange medium, based on said temperature.

4: The dehumidification apparatus of claim 1, wherein said heat-exchange medium is air and said fluid pump is a condenser fan.

5: The dehumidification apparatus of claim 1, wherein said heat-exchange medium is liquid and said fluid pump is variable-speed pump that drives fluid in a liquid circulation loop over said primary condenser.

6: The dehumidification apparatus of claim 1, wherein said heat-exchange medium is liquid and said liquid circulation loop incorporates a modulating valve to regulate the rate of flow of said heat-exchange medium over said primary condenser.

7: The dehumidification apparatus of claim 1 further comprising an auxiliary heating element for providing a second stage of heating.

8: The dehumidification apparatus of claim 1 further comprising a heating priority switch which energizes said compressor on a call for heating, without a call for dehumidification.