U.S. patent application number 11/656270 was filed with the patent office on 2008-07-24 for split system dehumidifier.
Invention is credited to David E. Beal, Daniel D. Thayer.
Application Number | 20080173035 11/656270 |
Document ID | / |
Family ID | 39639934 |
Filed Date | 2008-07-24 |
United States Patent
Application |
20080173035 |
Kind Code |
A1 |
Thayer; Daniel D. ; et
al. |
July 24, 2008 |
Split system dehumidifier
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.
Inventors: |
Thayer; Daniel D.; (Auburn,
ME) ; Beal; David E.; (Augusta, ME) |
Correspondence
Address: |
BOHAN MATHERS
PO BOX 17707
PORTLAND
ME
04112-8707
US
|
Family ID: |
39639934 |
Appl. No.: |
11/656270 |
Filed: |
January 22, 2007 |
Current U.S.
Class: |
62/173 ; 62/190;
62/324.6 |
Current CPC
Class: |
F24F 3/153 20130101 |
Class at
Publication: |
62/173 ; 62/190;
62/324.6 |
International
Class: |
F25B 49/00 20060101
F25B049/00; F25B 13/00 20060101 F25B013/00; F25B 29/00 20060101
F25B029/00; F25D 17/06 20060101 F25D017/06 |
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.
Description
BACKGROUND INFORMATION
[0001] 1. Field of the Invention
[0002] The invention relates to the field of heating, ventilation,
and air-conditioning. More particularly, the invention relates to
dehumidification.
[0003] 2. Description of the Prior Art
[0004] 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.
[0005] 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.
[0006] 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.
[0007] 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.
[0008] 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.
[0009] 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
[0010] 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.
[0011] 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.
[0012] 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.
[0013] 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.
[0014] 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
[0015] 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.
[0016] 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.
[0017] FIG. 2 is a wiring diagram of the dehumidifier system of
FIG. 1.
[0018] FIG. 3 illustrates a second embodiment of the condensing
unit, showing a water-cooled condenser.
[0019] FIG. 4 illustrates a second embodiment of the indoor
section, showing an auxiliary heat source.
DETAILED DESCRIPTION OF THE INVENTION
[0020] 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.
[0021] 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.
[0022] 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.
[0023] 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.
[0024] 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.
[0025] 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.
[0026] 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.
[0027] 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.
[0028] 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.
[0029] 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.
[0030] 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.
[0031] 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.
[0032] It is understood by those skilled in the art, that the
indoor section 10 may be packaged with the condensing unit 40.
[0033] 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.
* * * * *