U.S. patent application number 11/159925 was filed with the patent office on 2006-12-28 for method and system for dehumidification and refrigerant pressure control.
This patent application is currently assigned to YORK INTERNATIONAL CORPORATION. Invention is credited to Patrick Gordon Gavula, John Terry Knight, Anthony William Landers, Stephen Blake Pickle.
Application Number | 20060288713 11/159925 |
Document ID | / |
Family ID | 37565654 |
Filed Date | 2006-12-28 |
United States Patent
Application |
20060288713 |
Kind Code |
A1 |
Knight; John Terry ; et
al. |
December 28, 2006 |
Method and system for dehumidification and refrigerant pressure
control
Abstract
A method for dehumidification and controlling system pressure in
a refrigeration system includes providing a refrigeration system
having a compressor, a condenser and an evaporator connected in a
closed refrigerant loop. Each of the condenser and evaporator have
a plurality of refrigerant circuits. A first heat transfer fluid is
flowed over the condenser and a second heat transfer fluid is
flowed over the evaporator. At least one of the refrigerant
circuits of the condenser is isolated to provide a decreased amount
of heat transfer area within the condenser and to increase the
refrigerant pressure within the refrigeration system when the
refrigerant pressure within the refrigeration system is at or below
a predetermined pressure. At least one of the refrigerant circuits
of the evaporator is isolated to dehumidify and maintain the
temperature of the second heat transfer fluid at or above a
predetermined temperature when dehumidification is required.
Inventors: |
Knight; John Terry; (Moore,
OK) ; Landers; Anthony William; (Yukon, OK) ;
Gavula; Patrick Gordon; (Oklahoma City, OK) ; Pickle;
Stephen Blake; (Norman, OK) |
Correspondence
Address: |
MCNEES WALLACE & NURICK, LLC
100 PINE ST.
P.O. BOX 1166
HARRISBURG
PA
17108-1166
US
|
Assignee: |
YORK INTERNATIONAL
CORPORATION
York
PA
|
Family ID: |
37565654 |
Appl. No.: |
11/159925 |
Filed: |
June 23, 2005 |
Current U.S.
Class: |
62/176.6 ;
62/197; 62/199; 62/504 |
Current CPC
Class: |
F25B 2600/2517 20130101;
F25B 2600/2519 20130101; F25B 2700/197 20130101; F25B 2600/2511
20130101; F25B 2700/19 20130101; F25B 5/02 20130101; F25B 49/027
20130101; F24F 3/153 20130101 |
Class at
Publication: |
062/176.6 ;
062/197; 062/199; 062/504 |
International
Class: |
F25B 49/00 20060101
F25B049/00; F25B 41/00 20060101 F25B041/00; F25B 5/00 20060101
F25B005/00; F25B 39/02 20060101 F25B039/02 |
Claims
1. A method for dehumidification and controlling system pressure in
a refrigeration system comprising the steps of: providing a
refrigeration system having a compressor, a condenser and an
evaporator connected in a closed refrigerant loop, each of the
condenser and evaporator having a plurality of refrigerant
circuits; flowing a first heat transfer fluid over the condenser;
flowing a second heat transfer fluid over the evaporator;
controlling a flow of refrigerant in the plurality of refrigerant
circuits in the condenser to control an amount of heat transfer
between refrigerant in the condenser and the first heat transfer
fluid; controlling a flow of refrigerant in the plurality of
refrigerant circuits in the evaporator to control an amount of heat
transfer between refrigerant in the evaporator and the second heat
transfer fluid; isolating at least one of the refrigerant circuits
of the condenser to provide a decreased amount of heat transfer
area within the condenser and to increase refrigerant pressure
within the refrigeration system when the refrigerant pressure
within the refrigeration system is at or below a predetermined
pressure; and configuring the plurality of refrigerant circuits of
the evaporator to provide dehumidification of the second heat
transfer fluid without overcooling the second heat transfer
fluid.
2. The method of claim 1, further comprising drawing refrigerant
from the at least one of the circuits isolated from refrigerant
flow in the condenser by fluidly connecting the isolated portion of
the condenser to the suction of the compressor.
3. The method of claim 2, wherein refrigerant from the isolated
portion of the condenser is drawn into the refrigeration system to
increase the refrigerant pressure.
4. The method of claim 1, further comprising measuring refrigerant
pressure at a predetermined location in the refrigeration
system.
5. The method of claim 1, the method further comprising: providing
a first control valve fluidly connected to a first set of circuits
of the plurality of circuits of the evaporator, wherein the first
control valve controls flow of refrigerant to the first set of
circuits of the evaporator; and providing a second control valve
fluidly connected to a second set of circuits of the plurality of
circuits of the evaporator, wherein the second refrigerant control
valve controls flow of refrigerant to the second set of circuits of
the evaporator.
6. The method of claim 5, wherein the second control valve permits
a greater amount of refrigerant flow than the first control
valve.
7. The method of claim 6, wherein the first and second control
valves are thermostatic expansion valves.
8. The method of claim 5, the method further comprising: isolating
the first set of circuits of the evaporator from flow of
refrigerant from the condenser; and providing at least a portion of
refrigerant discharged from the compressor to the first set of
circuits of the evaporator without flowing through the
condenser.
9. The method of claim 8, wherein the step of providing at least a
portion of refrigerant includes flowing refrigerant from the
compressor through a fluid connection to an inlet of the first set
of circuits of the evaporator.
10. The method of claim 9, wherein the step of providing at least a
portion of refrigerant includes: connecting a discharge of the
compressor to an outlet of the first set of circuits of the
evaporator, flowing refrigerant from the compressor through a fluid
connection to the first set of circuits, the flow of refrigerant
from the compressor through the first set of circuits of the
evaporator being countercurrent to a flow of refrigerant in the
second set of circuits of the evaporator, and combining the flow of
refrigerant through the first set of circuits with the inlet flow
of refrigerant of the second set of circuits of the evaporator.
11. The method of claim 10, further comprising condensing the
refrigerant flowing in the first set of circuits countercurrent to
the flow of refrigerant in the second set of circuits from a gas to
a liquid, wherein the liquid flows into the second set of circuits
of the evaporator.
12. A method for dehumidification and controlling refrigerant
pressure in a heating, ventilation and air conditioning system
comprising: providing a closed loop refrigerant system comprising a
compressor, a condenser and an evaporator, each of the condenser
and evaporator having a plurality of refrigerant circuits
configured and disposed to allow isolation of at least one of the
refrigerant circuits from refrigerant flow; measuring refrigerant
pressure at a predetermined location in the refrigeration system;
determining an operational mode for the refrigeration cycle, the
operational mode being a selected from the group consisting of
cooling and dehumidification; isolating at least one of the
refrigeration circuits in the condenser from refrigerant flow when
the measured pressure at the predetermined location is equal to or
less than a predetermined pressure; isolating a first set of
refrigerant circuits in the evaporator from flow of refrigerant
from the condenser when the operational mode is dehumidification;
permitting flow of refrigerant from the condenser to both the first
set of circuits and a second set of refrigerant circuits in the
evaporator when the operational mode is cooling; and wherein the
refrigerant pressure is increased by isolation of at least one of
the refrigerant circuits in the condenser from refrigerant flow
until the measured pressure is greater than the predetermined
pressure.
13. The method of claim 12, further comprising dehumidifying a heat
transfer fluid flowing over both the first and second set of
circuits when the operational mode is dehumidification.
14. The method of claim 12, wherein the predetermined location is
the outlet of the evaporator.
15. The method of claim 14, wherein the predetermined pressure is a
pressure corresponding to an icing condition of the evaporator.
16. The method of claim 12, further comprising drawing refrigerant
from the at least one circuit isolated from refrigerant flow in the
condenser by fluidly connecting a portion of the condenser
including the at least one circuit isolated from refrigerant flow
to the suction of the compressor.
17. The method of claim 16, wherein refrigerant from the portion of
the condenser including the at least one circuit isolated from
refrigerant flow is added to the refrigeration system to increase
the refrigerant pressure.
18. The method of claim 12, further comprising: providing a first
control valve fluidly connected to the first set of circuits of the
plurality of circuits of the evaporator, wherein the first control
valve controls flow of refrigerant to the first set of circuits of
the evaporator; and providing a second control valve fluidly
connected to the second set of circuits of the plurality of
circuits of the evaporator, wherein the second refrigerant control
valve controls flow of refrigerant to the second set of circuits of
the evaporator.
19. The method of claim 18, wherein the second control valve
permits a greater amount of refrigerant flow than the first control
valve.
20. The method of claim 19, wherein the first and second control
valves are thermostatic expansion valves.
21. The method of claim 18, further comprising: providing at least
a portion of refrigerant discharged from the compressor to the
first set of circuits of the evaporator without first flowing
through the condenser.
22. The method of claim 21, wherein the providing at least a
portion of refrigerant step includes flowing refrigerant from the
compressor through a fluid connection to an inlet of the first set
of circuits of the evaporator.
23. The method of claim 21, wherein the providing at least a
portion of refrigerant step includes: connecting a discharge of the
compressor to an outlet of the first set of circuits of the
evaporator; flowing refrigerant from the compressor through a fluid
connection to the first set of circuits, the flow of refrigerant
from the compressor through the first set of circuits of the
evaporator being countercurrent to the flow of refrigerant in the
second set of circuits of the evaporator; and combining the flow of
refrigerant through the first set of circuits with an inlet flow of
refrigerant to the second set of circuits of the evaporator.
24. The method of claim 23, further comprising condensing the
refrigerant flowing in the first set of circuits countercurrent to
the flow of refrigerant in the second set of circuits from a gas to
a liquid, wherein the liquid is flowed into the second set of
circuits of the evaporator.
25. A heating, ventilation and air conditioning system comprising:
a compressor; a condenser arrangement comprising: a plurality of
circuits arranged into a first and second portion; and a valve
arrangement configured and disposed to isolate the first portion of
the condenser arrangement when the refrigerant pressure is below a
predetermined pressure; and an evaporator arrangement comprising: a
plurality of circuits arranged into a first and second portion; at
least one distributor configured to distribute and deliver
refrigerant to each circuit of the plurality of circuits in the
evaporator; and a valve arrangement configured and disposed to
isolate the first portion of the evaporator arrangement from
refrigerant flow in a dehumidification operation.
26. The system of claim 25, further comprising: a first control
valve fluidly connected to the first portion of the evaporator,
wherein the first control valve controls flow of refrigerant to the
first portion of the evaporator arrangement; and a second control
valve fluidly connected to the second portion of the evaporator
arrangement, wherein the second control valve controls flow of
refrigerant to the second portion of the evaporator
arrangement.
27. The system of claim 26, wherein the second control valve
permits a greater amount of refrigerant flow than the first control
valve.
28. The system of claim 27, wherein the first and second control
valves are thermostatic expansion valves.
29. The system of claim 25, further comprising a fluid connection
to connect the compressor to the first portion of the evaporator
arrangement, the fluid connection being configured to allow flow of
at least a portion of refrigerant discharged from the compressor to
the first portion of the evaporator arrangement without traveling
through the condenser arrangement during a dehumidification
operation.
30. The system of claim 29, wherein the fluid connection connects a
discharge of the compressor to an inlet of the first portion of the
evaporator arrangement.
31. The system of claim 29, wherein the fluid connection connects a
discharge of the compressor to an outlet of the first portion of
the evaporator arrangement, wherein flow of refrigerant from the
compressor through the first portion of the evaporator arrangement
is permitted to flow countercurrent to the flow of refrigerant in
the second portion of the evaporator arrangement, refrigerant
flowing in the first portion of the evaporator arrangement combines
with refrigerant at an inlet of the second portion of the
evaporator arrangement.
32. The system of claim 31, wherein the refrigerant flowing
countercurrent to the flow of refrigerant in the second portion of
the evaporator arrangement condenses from a gas to a liquid and the
liquid flows into the second portion of the evaporator arrangement.
Description
FIELD OF THE INVENTION
[0001] The present invention relates generally to heating,
ventilation and air conditioner systems (HVAC), including systems
that can dehumidify air.
BACKGROUND OF THE INVENTION
[0002] An HVAC system generally includes a closed loop
refrigeration system with at least one evaporator, at least one
condenser and at least one compressor. As the refrigerant travels
through the evaporator, it absorbs heat from a heat transfer fluid
and changes from a liquid to a vapor phase. After exiting the
evaporator, the refrigerant proceeds to a compressor, then a
condenser, then an expansion valve, and back to the evaporator,
repeating the loop. The heat transfer fluid to be cooled (e.g. air)
passes through the evaporator in a separate fluid channel and is
cooled by the evaporation of the refrigerant. The heat transfer
fluid can then be sent to a distribution system for cooling the
spaces to be conditioned, or it can be used for other refrigeration
purposes.
[0003] Other refrigeration purposes may include dehumidification.
Dehumidification of air in HVAC systems can occur through the use
of the evaporator in the cooling mode. One drawback to using just
an evaporator for dehumidification is an excess reduction in air
temperature that results, which is commonly referred to as
overcooling. Overcooling occurs when air that is subject to
dehumidification is cooled to a temperature that is below the
desired temperature of the air. Overcooling is a particular problem
when dehumidification is required in a room that is already
relatively cool and does not require additional cooling.
Overcooling generally involves air temperatures of approximately
50.degree. F. to 55.degree. F. or lower.
[0004] The problem of overcooling has been addressed in one
solution by utilization of a reheat coil in one solution. Air that
is overcooled by the evaporator is passed over the reheat coil in
order to increase the temperature of the overcooled, dehumidified
air to a desired temperature. The reheat coil can be heated by
diverting hot refrigerant through the reheat coil when
dehumidification is required. Reheat may also be provided by
alternate heat sources, such as electric heat or gas heat. The
reheat coil system for providing heat to the dehumidified,
overcooled air has several drawbacks including the requirement of
additional equipment and/or piping and/or additional energy
input.
[0005] Another dehumidification method known in the art is
disclosed in U.S. Pat. No. 4,182,133 (the '133 patent). The '133
patent is directed to a dehumidification method that controls
refrigerant flow through circuits within the indoor coil of an air
conditioning/heat pump unit. The '133 patent system, when providing
dehumidification, has a header that distributes the refrigerant
across several circuits within the indoor coil. At the opposite end
of the indoor coil, the outlets of the various circuits of the coil
are allowed to flow into a single common vapor header. The header
at the inlet of the indoor coil contains a solenoid valve that may
be closed to prevent refrigerant flow to one or more of the
circuits within the coil. The '133 patent system operates such that
when humidity reaches a certain level, the valve in the inlet
header is closed in order to limit the number of available circuits
for refrigerant flow. The area of the indoor coil that remains in
the active circuit and receives refrigerant flow, experiences an
increase in refrigerant flow through a given heat transfer area.
The increased flow of refrigerant results in a greater amount of
moisture being removed from the air in that portion of the indoor
coil. One drawback of the '133 patent system is that the
dehumidified air is not reheated and may be overcooled. Another
drawback of the '133 patent system is that the inlet header does
not distribute flow across the circuits of the evaporator, leading
to uneven phase distribution of refrigerant across the evaporator
heat exchanger. Another drawback of the '133 patent system is that
it is nearly impossible for a properly functioning system to
deliver supply air that has not been sensibly cooled.
[0006] One type of HVAC system is a split system where there is an
indoor unit or heat exchanger, which is generally the evaporator,
and an outdoor unit or heat exchanger, which is generally the
condenser. Often, the outdoor unit is placed outdoors and is
subject to outdoor ambient conditions, particularly temperature.
When the outdoor ambient temperature falls, the amount of heat
being removed from the refrigerant in the condenser increases. The
increased heat removal in the condenser can result in a decrease in
the refrigerant pressure at the suction line to the compressor,
commonly referred to as head pressure. The decrease in head
pressure results in a lowering of the temperature of the
refrigerant at the evaporator. When the temperature of the
refrigerant at the evaporator becomes too low, icing of the
evaporator can occur. Icing is a condition when the temperature at
the exterior of the system is sufficiently low to freeze water
present in the atmosphere. The ice formed by the water frozen on
the surface reduces the available heat transfer surface and
eventually prevents the proper operation of the HVAC system by
inhibiting heat transfer and/or damaging system components.
[0007] Some attempts to address the problem of icing have utilized
the control of system pressure. In one approach, a variable speed
condenser fan or a plurality of condenser fans having independent
controls are used to control airflow over the condenser coil. As
the amount of air passing over the coil decreases, the amount of
heat transfer taking place at the coil decreases. Therefore, the
temperature of the refrigerant in the condenser and the pressure of
the system increase to allow the indoor coil to cool the air
without icing problems. The use of the variable speed condenser fan
or a plurality of condenser fans having independent controls has
the drawback that it is expensive and requires complicated wiring
and controls.
[0008] An alternate approach for the problem of low system pressure
or icing is a parallel set of condensers in the refrigerant cycle,
as described in U.S. Pat. No. 3,631,686 (the '686 patent). In the
'686 patent system a parallel set of refrigerant condensers allows
for two modes of operation. One mode of operation allows
refrigerant to flow from only one of the refrigerant condensers.
During this mode of operation, the condenser that does not permit
the flow of refrigerant fills with liquid refrigerant. Because of
this flooding, there is a reduction in the effective surface area
of the condenser. The reduced surface area thereby reduces the
ability of the condenser to remove heat from the refrigerant.
Therefore, the temperature of the refrigerant in the condenser and
the head pressure of the system increase, allowing the indoor coil
to cool the air without icing. The use of parallel refrigerant
condensers has the drawback that it requires an additional
condenser coil and additional piping, thereby increasing the space
and cost required for installation. Another drawback associated
with refrigerant flooding of the condenser coil is the resultant
decrease in system capacity. Refrigerant normally available in a
properly operating system is trapped in the condenser coil and not
available to the compressor, thereby decreasing system
capacity.
[0009] Therefore, what is needed is a method and system for
dehumidification that dehumidifies air without overcooling,
provides control of the refrigerant pressure and provides a system
that can be retrofitted into existing systems without the drawbacks
discussed above.
SUMMARY OF THE INVENTION
[0010] The present invention is directed to a method for
dehumidification and controlling system pressure in a refrigeration
system. The method comprises the step of providing a refrigeration
system having a compressor, a condenser and an evaporator connected
in a closed refrigerant loop. Each of the condenser and evaporator
have a plurality of refrigerant circuits. A first heat transfer
fluid is flowed over the condenser. A second heat transfer fluid is
flowed over the evaporator. The flow of refrigerant is controlled
in the refrigerant circuits in the condenser to control the amount
of heat transfer between refrigerant in the condenser and the first
heat transfer fluid. The flow of refrigerant is controlled in the
refrigerant circuits in the evaporator to control an amount of heat
transfer between refrigerant in the evaporator and the second heat
transfer fluid. At least one of the refrigerant circuits of the
condenser is isolated to provide a decreased amount of heat
transfer area within the condenser and to increase the refrigerant
pressure within the refrigeration system when the refrigerant
pressure within the refrigeration system is at or below a
predetermined pressure. At least one of the refrigerant circuits of
the evaporator is isolated to dehumidify the second heat transfer
fluid and maintain the temperature of the second heat transfer
fluid at or above a predetermined temperature when dehumidification
is required.
[0011] Another embodiment of the invention includes a method for
dehumidification and controlling refrigerant pressure in a heating,
ventilation and air conditioning system. The method comprises
providing a closed loop refrigerant system comprising a compressor,
a condenser and an evaporator. Each of the condenser and evaporator
having a plurality of refrigerant circuits configured and disposed
to allow isolation of at least one of the refrigerant circuits from
refrigerant flow. Pressure is measured at a predetermined location
in the refrigeration system. An operational mode is determined for
the refrigeration cycle. The operational mode is selected from the
group consisting of cooling and dehumidification. At least one of
the refrigeration circuits in the condenser is isolated from
refrigerant flow when the measured pressure at the predetermined
location is equal to or less than a predetermined pressure. A first
set of refrigerant circuits in the evaporator is isolated from flow
of refrigerant from the condenser when the operational mode is
dehumidification. Flow of refrigerant is permitted from the
condenser to both the first and second set of refrigerant circuits
in the evaporator when the operational mode is cooling. The
refrigerant pressure is increased by isolation of at least one of
the refrigerant circuits in the condenser from refrigerant flow
until the measured pressure is greater than the predetermined
pressure.
[0012] Another embodiment of the invention includes a heating,
ventilation and air conditioning system. The system comprises a
compressor, a condenser arrangement and an evaporator arrangement.
The condenser arrangement comprises a plurality of circuits
arranged into a first and second set of circuits, and a valve
arrangement configured and disposed to isolate the first set of
circuits of the condenser arrangement when the refrigerant pressure
is below a predetermined pressure. The evaporator arrangement
comprises a plurality of circuits arranged into a first and second
set of circuits, at least one distributor configured to distribute
and deliver refrigerant to each circuit of the plurality of
circuits in the evaporator, and a valve arrangement configured and
disposed to isolate the first set of circuits of the evaporator
arrangement from refrigerant flow in a dehumidification operation
of the HVAC system.
[0013] The present invention provides an inexpensive method and
system to control head pressure, while also being capable of
reheating dehumidified air. The method and system requires little
or no additional piping in order to implement the method and system
in an existing HVAC unit. The system requires less in materials and
therefore costs less than systems having separate components, such
as separate reheat coils.
[0014] Another advantage of the present invention is that the air
conditioning or heat pump unit can operate at lower outdoor ambient
temperatures by providing an increase in system pressure to avoid
icing of the system components.
[0015] Another advantage of the present invention is that the
system and method distributes refrigerant substantially uniformly
across the evaporator to provide substantially uniform refrigerant
phase distribution and heat exchange across the evaporator.
[0016] Another advantage of the present invention is that the
system can reheat air and control head pressure without the need
for a separate airflow system.
[0017] Another advantage of the system is that the simultaneous
control of the head pressure of the system and reheating of the air
during dehumidification permits the system to be operated in a
manner that increases the efficiency and reliability of the system,
while maintaining greater control of the temperature and humidity
of the conditioned air.
[0018] Other features and advantages of the present invention will
be apparent from the following more detailed description of the
preferred embodiment, taken in conjunction with the accompanying
drawings which illustrate, by way of example, the principles of the
invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] FIG. 1 schematically illustrates a refrigeration or HVAC
system.
[0020] FIG. 2 schematically illustrates one embodiment of an
evaporator and piping arrangement of the present invention.
[0021] FIG. 3 schematically illustrates another embodiment of an
evaporator and piping arrangement of the present invention.
[0022] FIG. 4 schematically illustrates further embodiment of an
evaporator and piping arrangement of the present invention.
[0023] FIG. 5 schematically illustrates one embodiment of a
condenser and piping arrangement of the present invention.
[0024] FIG. 6 schematically illustrates another embodiment of a
condenser and piping arrangement of the present invention.
[0025] FIG. 7 schematically illustrates one embodiment of a
refrigeration or HVAC system according to the present
invention.
[0026] FIG. 8 schematically illustrates another embodiment of a
refrigeration or HVAC system according to the present
invention.
[0027] FIG. 9 schematically illustrates a refrigeration or HVAC
system of another embodiment of the present invention.
[0028] FIG. 10 schematically illustrates a refrigeration or HVAC
system of a further embodiment of the present invention.
[0029] FIG. 11 illustrates a control method of the present
invention.
[0030] FIG. 12 illustrates a control method of another embodiment
of the present invention.
[0031] FIG. 13 illustrates a control method of a further embodiment
of the present invention.
[0032] FIG. 14 illustrates a control method of a further embodiment
of the present invention.
[0033] FIG. 15 illustrates a control method of a further embodiment
of the present invention.
[0034] FIG. 16 illustrates a control method of a further embodiment
of the present invention.
[0035] Wherever possible, the same reference numbers will be used
throughout the drawings to refer to the same or like parts.
DETAILED DESCRIPTION OF THE INVENTION
[0036] FIG. 1 illustrates a HVAC, refrigeration, or chiller system
100. Refrigeration system 100 includes a compressor 130, a
condenser 120, and an evaporator 110. The compressor 130 compresses
a refrigerant vapor and delivers it to the condenser 120 through
compressor discharge line 135. The compressor 130 is preferably a
reciprocating or scroll compressor, however, any other suitable
type of compressor can be used, for example, screw compressor,
rotary compressor, and centrifugal compressor. The refrigerant
vapor delivered by the compressor 130 to the condenser 120 enters
into a heat exchange relationship with a first heat transfer fluid
150, preferably air, and undergoes a phase change to a refrigerant
liquid as a result of the heat exchange relationship with the first
heat transfer fluid 150. The first heat transfer fluid 150 is moved
by use of a fan 170, which moves the first heat transfer fluid 150
through the condenser 120 in a direction perpendicular the cross
section of the condenser 120. In a preferred embodiment, the
refrigerant vapor delivered to the condenser 120 enters into a heat
exchange relationship with air as the first heat transfer fluid
150. The refrigerant leaves the condenser through the condenser
discharge line 140 and is delivered to an evaporator 110 after
passing through an expansion device (not shown). The evaporator 110
includes a heat-exchanger coil. The liquid refrigerant in the
evaporator 110 enters into a heat exchange relationship with a
second heat transfer fluid 155 to lower the temperature of the
second heat transfer fluid 155. The second heat transfer fluid 155,
preferably air, is moved by use of a blower 160, which moves the
second heat transfer fluid 155 through evaporator 110 in a
direction perpendicular the cross section of the evaporator 110.
Although FIG. 1 depicts the use of a blower 160 and fan 170, any
fluid moving means may be used to move fluid through the evaporator
and condenser 120. In a preferred embodiment, the refrigerant vapor
delivered to the evaporator 110 enters into a heat exchange
relationship with air as the second heat transfer fluid 155. The
refrigerant liquid in the evaporator 110 undergoes a phase change
to a refrigerant vapor as a result of the heat exchange
relationship with the second heat transfer fluid 155. The vapor
refrigerant in the evaporator 110 exits the evaporator 110 and
returns to the compressor 130 through a suction line 145 to
complete the cycle. The conventional refrigerant system 100
includes many other features that are not shown in FIG. 1. These
features have been purposely omitted to simplify the figure for
ease of illustration.
[0037] FIG. 2 illustrates a partitioned evaporator 200 according to
one embodiment of the present invention. The inlet of the
partitioned evaporator 200 includes a condenser discharge line 140
from the partitioned condenser 500 (see FIG. 7), a first and second
thermostatic expansion valve (TXV valve) 260 and 265, an isolation
valve 250, and a first and second distributor 240 and 245. Although
FIGS. 2-4 and 7-9 illustrate TXV valves, any suitable pressure
reduction or expansion device may be used to control refrigerant
flow, such as a fixed orifice. The first TXV valve 260 and the
isolation valve 250 are positioned between condenser discharge line
140 and the first distributor 240. The second TXV valve 265 is
positioned between the condenser discharge line 140 and the second
distributor 245. The partitioned evaporator 200 includes
refrigerant circuits 210. Although refrigerant circuits 210 are
shown as curved lines in FIGS. 2-4, the shape shown is merely
schematic and any suitable configuration of refrigerant circuit 210
can be used. Refrigerant circuits 210 can include any configuration
of device capable of transferring heat. An example of a suitable
device includes a finned tube. The number of refrigerant circuits
210 may be any number of refrigerant circuits 210 that provide
sufficient heat transfer to maintain operation of the partitioned
evaporator 200 within the refrigeration system 100. The partitioned
evaporator 200 is preferably partitioned into a first and second
evaporator portions 220 and 230. The first and second evaporator
portion 220 and 230 may be sized in any proportion. For example,
the first evaporator portion 220 may be 60% of the size of the
partitioned evaporator 200 and the second evaporator portion 230
may be 40% of the size of the partitioned evaporator 200 or the
first evaporator portion 220 may be 40% of the size of the
partitioned evaporator 200 and the second evaporator portion 230
may be 60% of the size of the partitioned evaporator 200 or the
first and second evaporator portions 220 and 230 may each represent
50% of the size of the partitioned evaporator 200.
[0038] Although FIG. 2 shows the partitioned evaporator 200 as only
including two portions, any number of portions may be used in the
present invention. Where more than two evaporator portions are
present, the flow may be regulated to each of the portions. For
example, in the embodiment where the evaporator is split into three
portions, two of the three portions include valve arrangements that
allow independent isolation of each of these portions. One or both
of the two portions with valve arrangements may be isolated,
dependent on a signal from a controller and/or sensor. The outlet
of the partitioned evaporator 200 includes first and second
discharge headers 270 and 275, first and second thermostatic
expansion valve bulbs (TXV bulbs) 264 and 269, and an evaporator
discharge line 145 to the compressor 130. The first discharge
header 270 receives refrigerant from the refrigerant circuits 210
in the first evaporator portion 220. The second discharge header
275 receives refrigerant from the refrigerant circuits 210 present
in the second evaporator portion 230. The first TXV bulb 264 is
positioned between the first discharge header 270 and the
evaporator discharge line 145. The first TXV bulb 264 senses the
temperature of the refrigerant leaving the first discharge header
270 and compares the temperature of the refrigerant to the
temperature of the refrigerant at the first TXV valve 260 through
line 262. The flow of refrigerant through the first TXV valve 260
is increased as the temperature difference at the first TXV bulb
264 and the first TXV valve 260 increases. The flow of refrigerant
through the first TXV valve 260 is decreased as the temperature
difference at the first TXV bulb 264 and the first TXV valve 260
decreases. The second TXV valve 265 operates in the same manner
with respect to the refrigerant discharge from the second discharge
header 275 and communicates the temperature measurement to the
second TXV valve 265 through line 267. The isolation valve 250
allows the first evaporator portion 220 of the partitioned
evaporator 200 to be isolated from flow of refrigerant. In one
embodiment, to accommodate an increased flow of refrigerant to the
second evaporator portion 230, as discussed in detail below, the
size of the second TXV valve 265 (i.e., the amount of flow
permitted through the valve) is greater than the size of the first
TXV valve 260.
[0039] During operation of the refrigeration system 100 in cooling
mode, refrigerant flows from the partitioned condenser 500 to the
partitioned evaporator 200 through condenser discharge line 140.
The flow is split into two refrigerant flow paths prior to entering
the partitioned evaporator 200. Although FIG. 2 shows two paths
leading to the first and second distributors 240 and 245, the
refrigerant flow may be split into two or more paths. If the system
is in a cooling only mode, isolation valve 250 is open and
refrigerant is permitted to flow into both the first and second
evaporator portions 220 and 230 of the partitioned evaporator 200.
The two refrigerant flow paths are further split by a first and
second distributor 240 and 245 into a plurality of lines,
corresponding to the individual refrigerant circuits 210. The first
and second distributors 240 and 245 may include any arrangement
that distributes the refrigerant to the individual refrigerant
circuits 210 within the partitioned evaporator 200. The first and
second distributors 240 and 245 can preferably distribute the
refrigerant to provide uniform phase distribution across the
refrigerant circuits 210 of the partitioned evaporator 200 and,
thus, provide substantially uniform heat transfer. The first and
second distributors 240 and 245 also may include combinations of
distributor tubes and orifices to provide the uniform refrigerant
flow. The refrigerant flows into the refrigerant circuits 210 of
first and second evaporator portions 220 and 230. The refrigerant
circuits 210 permit the refrigerant to enter into a heat transfer
relationship with the second heat transfer fluid 155 to cool the
second heat transfer fluid 155. Due to the heat transfer with the
second heat transfer fluid 155, the refrigerant entering the first
and second discharge headers 270 and 275 has a higher temperature
than the temperature of the refrigerant entering the partitioned
evaporator 200. The refrigerant then travels from the first and
second discharge headers 270 and 275 past the first and second TXV
bulbs 264 and 269. The TXV bulbs 264 and 269 sense the temperature
of the refrigerant leaving the partitioned evaporator 200 and
communicate the temperature to the first and second TXV valves 260
and 265 in order to determine the appropriate refrigerant flow into
the partitioned evaporator 200. After traveling past the first and
second TXV bulbs 264 and 269, the refrigerant is delivered to the
compressor 130 through evaporator discharge line 145.
[0040] If the system shown in FIG. 2 is operated in a
dehumidification mode, isolation valve 250 is closed and
refrigerant flow to the first evaporator portion 220 is prevented.
The refrigerant flow in the second evaporator portion 230 occurs
substantially as described above with respect to evaporator portion
220 in cooling mode. However, the flow of refrigerant to the first
evaporator portion 220 is prevented. Since flow to the first
evaporator portion 220 is prevented, the flow to the second
evaporator portion 230 is increased. Due to the increased flow of
the refrigerant through the second evaporator portion 230, the
amount of heat transfer per unit area is increased and the
dehumidification per unit area is likewise increased. Therefore,
when the second heat transfer fluid 155 is passed through the
second evaporator portion 230 the second heat transfer fluid 155 is
cooled and dehumidified, and the second heat transfer fluid 155
passing through the first evaporator portion 220 remains
substantially unchanged in temperature and humidity from inlet to
outlet. The second heat transfer fluid 155 passed through the
second evaporator portion 230 is generally overcooled and the
second heat transfer fluid 155 passed through the first evaporator
portion 220 is about ambient temperature. The ambient second heat
transfer fluid 155 that passes though the first evaporator portion
220 mixes with the second heat transfer fluid 155 passing through
the second evaporator portion 230 and produces an outlet heat
transfer fluid, preferably air, that is dehumidified and not
overcooled. As shown in FIG. 2, the flow of the second heat
transfer fluid 155 is substantially perpendicular to the
cross-section of the evaporator. The direction of the flow is such
that the heat transfer fluid 155 flows simultaneously through first
evaporator portion 220 and second evaporator portion 230. A single
system for moving the second heat transfer fluid 155, such as an
air blower 160, can be used to simultaneously move air through
first evaporator portion 220 and second evaporator portion 230.
[0041] FIG. 3 illustrates a partitioned evaporator 200 according to
another embodiment of the present invention. The inlet of the
partitioned evaporator 200 includes substantially the same
arrangement of components as FIG. 2, including a condenser
discharge line 140 from the partitioned condenser 500, first and
second TXV valves 260 and 265, and first and second distributors
240 and 245. FIG. 3 further includes check valve 255 that prevents
flow of refrigerant into evaporator portion 220 and allows flow of
refrigerant out of evaporator portion 220. The partitioned
evaporator 200 includes substantially the same arrangement of
refrigerant circuits 210 as FIG. 2. The outlet of the partitioned
evaporator 200 shown in FIG. 3 includes the first and second
discharge headers 270 and 275, first and second TXV bulbs 264 and
269, an evaporator discharge line 145 to the compressor 130 and a
first discharge header discharge line 310 to a 3-way valve 910 (see
FIG. 8). The first discharge header 270 receives refrigerant from
the refrigerant circuits 210 present in the first evaporator
portion 220. The second discharge header 275 receives refrigerant
from the circuits 210 present in the second evaporator portion 230.
The first TXV bulb 264 is positioned on the first discharge header
discharge line 310. The first TXV bulb 264 senses the temperature
of the refrigerant leaving the first discharge header 270 and
compares the temperature of the refrigerant to the temperature of
the refrigerant at the first TXV valve 260 through line 262. The
flow of refrigerant through the first TXV valve 260 is increased as
the temperature difference at the first TXV bulb 264 and the first
TXV valve 260 increases. The flow of refrigerant through the first
TXV valve 260 is decreased as the temperature difference at the
first TXV bulb 264 and the first TXV valve 260 decreases. The
second TXV valve 265 operates in the same manner with respect to
the refrigerant discharge from the second discharge header 275 and
communicates the temperature measurement to the second TXV valve
265 through line 267. The use of independent first and second TXV
valves 260 and 265 allows independent control of the flow through
each of the portions of the partitioned evaporator 200.
[0042] During operation in cooling mode, FIG. 3, like in the system
shown in FIG. 2, refrigerant flows from the partitioned condenser
500 into the partitioned evaporator 200 through condenser discharge
line 140, through the valve arrangement, including the first and
second TXV valves 260 and 265, and into the first and second
distributors 240 and 245. The refrigerant circuits 210 permit the
refrigerant to enter into a heat transfer relationship with the
second heat transfer fluid 155 that flows through the circuits
perpendicular to the cross-section shown in FIG. 3. Due to the heat
transfer with the second heat transfer fluid 155, the refrigerant
entering the first and second discharge headers 270 and 275 has a
higher temperature than the temperature of the refrigerant entering
the partitioned evaporator 200. The refrigerant flow through
discharge line 310 from the first discharge header 270 travels past
the first TXV bulb 264 and travels to a 3-way valve 910, discussed
in greater detail below. The refrigerant flow through evaporator
discharge line 145 from the second discharge header 275 travels
past the second TXV bulb 269 to the compressor 130.
[0043] During dehumidification mode, refrigerant flow in the first
evaporator portion 220 is received from the 3-way valve 910 through
the discharge line 310, as discussed in greater detail below. The
flow from the 3-way valve 910 is hot refrigerant gas taken from the
compressor discharge. The flow from the 3-way valve 910 travels
through the discharge line 310 in the direction of the first
discharge header 270. From the first discharge header 270, the hot
refrigerant gas enters the first evaporator portion 220 and travels
through circuits 210 to the first distributor 240. The refrigerant
in refrigerant circuits 210 of the first evaporator portion 220 can
heat the second heat transfer fluid 155 as the fluid passes over
the refrigerant circuits 210. The hot refrigerant gas is at least
partially condensed to a liquid in the first evaporator portion
220. The refrigerant, which is at least partially condensed to a
liquid, then bypasses the TXV valve 260 by traveling through check
valve 255. The flow through check valve 255 combines with the
condenser discharge line 140 and enters the second evaporator
portion 230 through the second distributor 245. Due to the
increased flow of the refrigerant through the second evaporator
portion 230, the amount of heat transfer per unit area is increased
and the dehumidification per unit area is likewise increased.
Simultaneously, hot gas refrigerant entering the first evaporator
portion 220 of the partitioned evaporator 200 provides an increase
in the temperature of the first evaporator portion 220 due to the
at least partial condensing of the hot gas. Therefore, the second
heat transfer fluid 155 passing through the second evaporator
portion 230 is cooled and dehumidified, while the second heat
transfer fluid 155 passing through the first evaporator portion 220
is heated by the hot gas refrigerant from the compressor discharge.
This second heat transfer fluid 155 simultaneously is circulated
through first and second evaporator portions 220 and 230 by a fluid
moving system, such as an air blower 160, when the second heat
transfer fluid 155 is air. The warmer second heat transfer fluid
155 that passes though the first evaporator portion 220 mixes with
the second heat transfer fluid 155 passing through the second
evaporator portion 230 and produces an outlet heat transfer fluid,
preferably air, that is dehumidified and not overcooled.
[0044] FIG. 4 illustrates a partitioned evaporator 200 according to
a further embodiment of the present invention. The inlet of the
partitioned evaporator 200 includes a condenser discharge line 140
from the partitioned condenser 500, a bypass line 410 (see FIG. 9)
from the discharge of the compressor 130, first and second TXV
valves 260 and 265, isolation valve 250, and first and second
distributors 240 and 245. The first TXV valve 260 and the isolation
valve 250 are positioned between condenser discharge line 140 and
the first distributor 240. The bypass line 410 connects to the line
between the first TXV valve 260 and the first distributor 240.
Bypass line 410 is from the discharge of the compressor 130 and
includes a flow restriction valve 430 and a bypass valve 440. While
FIG. 4 shows both a flow restriction valve 430 and a bypass valve
440, either one or both of valves 430 and 440 may be present. The
isolation valve 250 is positioned between the condenser discharge
line 140 and the first TXV valve 260. The second TXV valve 265 is
positioned between the condenser discharge line 140 and the second
distributor 245. The partitioned evaporator 200 includes
substantially the same arrangement of refrigerant circuits 210 as
shown in FIG. 2. The outlet of the partitioned evaporator 200
includes first and second discharge headers 270 and 275, first and
second TXV bulbs 264 and 269, and evaporator discharge line 145 to
the compressor 130. The first discharge header 270 receives
refrigerant from the refrigerant circuits 210 present in the first
evaporator portion 220. The second discharge header 275 receives
refrigerant from the refrigerant circuits 210 present in the second
evaporator portion 230. The first TXV bulb 264 is positioned
between the first discharge header 270 and the evaporator discharge
line 145. The first TXV bulb 264 senses the temperature of the
refrigerant leaving the first discharge header 270 and compares the
temperature of the refrigerant to the temperature of the
refrigerant at the first TXV valve 260 through line 262. The flow
of refrigerant through the first TXV valve 260 is increased as the
temperature difference at the first TXV bulb 264 and the first TXV
valve 260 increases. The flow of refrigerant through the first TXV
valve 260 is decreased as the temperature difference at the first
TXV bulb 264 and the first TXV valve 260 decreases. The second TXV
valve 265 operates in the same manner with respect to the
refrigerant discharge from the second discharge header 275 and
communicates the temperature measurement to the second TXV valve
265 through line 267. The isolation valve 250 allows the first
evaporator portion 220 of the partitioned evaporator 200 to be
isolated from flow of refrigerant. In one embodiment, to
accommodate the increased flow of refrigerant to the second
evaporator portion 230, the size of the second TXV valve 265 (i.e.,
the amount of flow permitted through the valve) is greater than the
size of the first TXV valve 260.
[0045] During operation in cooling mode, FIG. 4, like in the system
shown in FIG. 2, refrigerant flows from the partitioned condenser
500 into the refrigerant circuits 210 of the partitioned evaporator
200 through the condenser discharge line 140, through the valve
arrangement, including the first and second TXV valves 260 and 265,
and the isolation valve 250, and into the first and second
distributors 240 and 245. In cooling mode, substantially no flow of
refrigerant takes place into or out of the bypass line 410 because
the bypass valve 440 is closed. The operation of the refrigerant
circuits 210 and the outlet of the partitioned evaporator 200,
including the first and second headers 270 and 275, the first and
second TXV bulbs 264 and 269 and the evaporator discharge line 145
to the compressor is substantially similar to the operation
described above with respect to FIG. 2.
[0046] However, if the system shown in FIG. 4 is in
dehumidification mode, isolation valve 250 is closed and
refrigerant flow to the first TXV valve 260 is prevented.
Refrigerant flow from the discharge of the compressor 130 through
bypass line 410 flows into the first distributor 240 and into the
first evaporator portion 220. The hot gas refrigerant entering the
first evaporator portion 220 of the partitioned evaporator 200
provides an increase in the temperature of the first evaporator
portion 220. Due to the increased flow of the refrigerant through
the second evaporator portion 230 by closing isolation valve 250,
the amount of heat transfer per unit area is increased and the
dehumidification per unit area is likewise increased. Therefore,
the second heat transfer fluid 155 passing through the second
evaporator portion 230 is cooled and dehumidified, while the second
heat transfer fluid 155 passing through the first evaporator
portion 220 is warmed by the hot gas refrigerant from the
compressor discharge. The second heat transfer fluid 155
simultaneously is circulated through first and second evaporator
portions 220 and 230 by a fluid moving system, such as a blower
160. The warmer second heat transfer fluid 155 that passes though
the first evaporator portion 220 mixes with the second heat
transfer fluid 155 passing through the second evaporator portion
230 and produces an outlet heat transfer fluid, preferably air,
that is dehumidified and not overcooled.
[0047] Although the partitioned evaporator 200 has been illustrated
as containing two evaporator portions 220 and 230, the partitioned
evaporator 200 is not limited to two portions. Any number of
portions may be used, so long as one or more of the portions
includes valving to isolate the respective portion from refrigerant
flow.
[0048] In another embodiment, refrigerant circuits 210 may also be
isolated individually within the first and/or second distributor.
The refrigerant circuits 210 may be isolated with flow blocking
means or flow restriction means on first and second distributors
240 and 245. In this embodiment, a controller is used to determine
the number of circuits isolated. The number of refrigerant circuits
210 isolated relates to the amount of cooling and/or heating of
dehumidified air required and may be adjusted by the
controller.
[0049] FIG. 5 illustrates a partitioned condenser 500 according to
one embodiment of the invention. Partitioned condenser 500 includes
a plurality of heat transfer circuits 510. The heat transfer
circuits 510 are preferably partitioned into a first condenser
portion 520 and a second condenser portion 530. Although heat
transfer circuits 510 in the partitioned condenser 500 are shown as
lines in FIGS. 5-6, the shape shown is merely schematic. Heat
transfer circuits 510 are preferably of any suitable configuration
capable of transferring heat. An example of a suitable device
includes a finned tube. The first and second condenser portions 520
and 530 may be sized in any proportion. For example, the first
condenser portion 520 may be 60% of the size of the partitioned
condenser 500 and the second condenser portion 530 may be 40% of
the size of the partitioned condenser 500 or the first condenser
portion 520 may be 40% of the size of the partitioned condenser 500
and the second condenser portion 530 may be 60% of the size of the
partitioned condenser 500 or the first and second condenser
portions 520 and 530 may each represent 50% of the size of the
partitioned condenser 500. When the first and second condenser
portions 520 and 530 are different sizes, e.g., 60%/40% split, the
refrigerant flow may be directed in any manner that provides
efficient condenser 500 operation. For example, the first condenser
portion 520 may constitute 60% of the size of the partitioned
condenser 500 and the second condenser portion 530 may constitute
40% of the partitioned condenser 500. When desirable, the flow may
be directed to either the 60% portion or the 40% portion and the
designation of the first and second condenser portions 520 and 530
may be alternated to the isolated portion that provides the desired
condenser 500 operation.
[0050] Inlet flow 550 includes vaporous refrigerant from the
compressor 130. Inlet flow 550 enters the partitioned condenser 500
and travels through the heat transfer circuits 510, where the heat
transfer circuits 510 can enter into a heat exchange relationship
with a heat transfer fluid such as air. The partitioned condenser
500 preferably has two condenser portions; however, the present
invention is not limited to two condenser portions. The present
invention may include more than two condenser portions. Where more
than two condenser portions are present, the flow may be regulated
to each of the portions. For example, in an embodiment where the
condenser is split into three portions, two of the three portions
include valve arrangements that allow independent isolation of each
of these portions. One or both of the two portions with valve
arrangements may be isolated, dependent on a signal from a
controller and/or sensor. In FIG. 5, isolation valves 540 are
positioned in the vapor header 590 and liquid header 592 of the
partitioned condenser 500. When isolation valves 540 are closed,
the refrigerant is prevented from flowing into the second condenser
portion 530. When isolation valves 540 are open, refrigerant is
permitted to flow to both the first condenser portion 520 and the
second condenser portion 530. The outlet flow 560 leaving the
partitioned condenser 500 comprises liquid refrigerant resulting
from the heat exchange relationship with the heat transfer fluid
and the resultant phase change. The outlet flow 560 is then
circulated to the partitioned evaporator 200.
[0051] FIG. 6 illustrates a partitioned condenser 500 according to
an alternate embodiment of the invention. Partitioned condenser 500
includes a plurality of heat transfer circuits 510. The heat
transfer circuits 510 are partitioned into a first condenser
portion 520 and a second condenser portion 530. Although FIG. 6
shows two condenser portions, the present invention is not limited
to two condenser portions. The present invention may include more
than two condenser portions. Inlet flow 550 is vaporous refrigerant
from the compressor 130 that is split into two refrigerant streams.
The two refrigerant streams enter the partitioned condenser 500
through two vapor headers 593 and 594 and travel into the heat
transfer circuits 510. Heat transfer circuits 510 can enter into a
heat exchange relationship with a heat transfer fluid such as air.
The two refrigerant streams then exit the partitioned condenser 500
through two liquid headers 595 and 596. Isolation valves 540 are
positioned on the piping to the vapor header 594 and on the piping
from the liquid header 596 of the partitioned condenser 500. When
isolation valves 540 are closed, the refrigerant is prevented from
flowing into the second condenser portion 530. When isolation
valves 540 are open, refrigerant is permitted to flow to both the
first condenser portion 520 and the second condenser portion 530.
The outlet flow 560 leaving the partitioned condenser 500 includes
liquid refrigerant that is circulated to the partitioned evaporator
200.
[0052] The system for controlling the refrigerant pressure of an
air conditioning or heat pump unit according to the present
invention includes an HVAC unit that can operate at lower ambient
temperatures. The present invention involves a piping arrangement
that partitions the circuits within the condenser of a
refrigeration system. The piping arrangement includes valves
positioned so that one or more of the circuits within the condenser
may be isolated from flow of refrigerant. The piping arrangement
may be applied to a new system or may be applied to an existing
system. Applying the piping arrangement to the existing system has
the advantage that it allows control of the refrigerant pressure
without the addition of expensive piping, equipment and/or
controls.
[0053] When the temperature around the partitioned condenser 500
decreases (e.g., when the outdoor temperature decreases), the
system refrigerant pressure also decreases. To help increase
refrigerant head pressure, the present invention uses the valves
connected to the refrigerant circuits 510 of the partitioned
condenser 500 to isolate a portion of the partitioned condenser 500
from flow of refrigerant. The portion of the partitioned condenser
500 that is not isolated remains in the active circuit and receives
refrigerant. Because the refrigerant is only permitted to flow into
a portion of the partitioned condenser 500, the heat transfer area
and the corresponding amount of heat transfer is reduced.
Therefore, less heat is removed from the refrigerant. Likewise,
less heat is transferred to the first heat transfer fluid 150,
thereby maintaining a higher refrigerant temperature. Additionally,
because the temperature of the refrigerant is higher, the
corresponding pressure of the refrigerant is also higher.
Therefore, the refrigerant pressure of the system is increased.
[0054] The piping arrangement of the partitioned condenser 500 of
the present invention includes piping sufficient to isolate the one
or more heat transfer circuits 510 within the condenser. In one
embodiment, the isolation valves 540 are positioned inside the
vapor header 590 of the partitioned condenser 500. In an alternate
embodiment, the isolation valves 540 are positioned on piping
upstream from the vapor headers 594 of the partitioned condenser
500.
[0055] The lack of additional piping for both the partitioned
evaporator 200 and the partitioned condenser 500 also allows
retrofitting of the system of the present invention into existing
systems. Because the system utilizes the same components as
existing systems, the system takes up approximately the same volume
as existing HVAC systems. Therefore, the method and system of the
present invention may be used in existing systems whose piping is
arranged according to the present invention.
[0056] FIG. 7 shows a refrigeration system 100 incorporating a
partitioned evaporator 200 and a partitioned condenser 500
according to the present invention. FIG. 7 shows the refrigeration
system 100, including evaporator discharge line 145, blower 160,
compressor 130, compressor discharge line 135, partitioned
condenser 500, fan 170, condenser discharge line 140, and first
heat transfer fluid 150, substantially as described above in the
description of FIG. 1. FIG. 7 also shows the partitioned evaporator
200, including first and second TXV valves 260 and 265, isolation
valve 250, check valve 255, first and second distributors 240 and
245, first and second discharge headers 270 and 275, arranged as
discussed above in the description of FIG. 2. For illustration
purposes, FIGS. 7-10 divides second heat transfer fluid 155 flow
into an inlet flow 710 and an outlet flow 715. The inlet flow 710,
preferably air, flows into the partitioned evaporator 200
substantially evenly across the first and second evaporator
portions 220 and 230. Blower 160 moves inlet flow 710. Although
FIG. 7 depicts a blower, any fluid moving means is suitable for
moving the fluid across the first and second evaporator portions
220 and 230. The heat transfer fluid enters into a heat exchange
relationship with the first and second evaporator portions 220 and
230 and exits the partitioned evaporator as outlet flow 715. During
cooling mode, refrigerant is circulated from the partitioned
condenser 500 to the partitioned evaporator 200, through the first
and second evaporator portions 220 and 230 and to the compressor
130 through evaporator discharge line 145. The inlet flow 710 of
heat transfer fluid is cooled by both the first and second
evaporator portions 220 and 230, providing outlet flow 715 of heat
transfer fluid that has been cooled. During dehumidification mode,
isolation valve 250 is closed, preventing flow of refrigerant into
the first evaporator portion 220. The inlet flow 710 is cooled and
dehumidified by the second evaporator portion 230 and is
substantially untreated by the isolated first evaporator portion
220. The outlet flow 715 is a mixture of the cooled, dehumidified
air that flowed through the second evaporator portion 230 and the
substantially untreated air that flowed though the first evaporator
portion 220. The resultant outlet flow 715 is dehumidified air that
is not overcooled.
[0057] The partitioned condenser 500 shown in FIG. 7 is a
partitioned condenser having two partitions, shown as the first and
second condenser portions 520 and 530. Although FIG. 7 shows two
condenser portions, the present invention is not limited to two
condenser portions. The present invention may include more than two
condenser portions. The piping to the partitioned condenser 500
includes isolation valves 540 on the inlet side and the outlet side
of the second condenser portion 530 inside the partitioned
condenser 500. Closing the isolation valves 540 prevents the flow
of refrigerant to the second condenser portion 530. The isolation
valves 540 may be operated by a controller 720. One or more
controllers 720 facilitates the closing of isolation valves 540.
The controller 720 may receive inputs from pressure measuring or
temperature measuring devices and position the isolation valves
540, e.g., open or closed. When the pressure on the compressor
suction line 145 from the partitioned evaporator 200 to the
compressor 130 reaches a predetermined level, the isolation valves
540 can be closed to the second condenser portion 530. Once
isolation valves 540 are closed, the refrigerant is only permitted
to flow through the first condenser portion 520. Because the
refrigerant is only permitted to flow into first condenser portion
520, the heat transfer area and the corresponding amount of heat
transfer occurring in the partitioned condenser 500 is reduced.
Therefore, less heat is removed from the refrigerant. Likewise,
less heat is transferred to the first heat transfer fluid 150,
thereby maintaining a higher refrigerant temperature. Additionally,
because the temperature of the refrigerant is higher, the
corresponding pressure of the refrigerant is also higher.
Therefore, the refrigerant pressure of the system is increased.
[0058] FIG. 8 shows a refrigeration system according to an
alternate embodiment. FIG. 8 includes substantially the same piping
arrangement as FIG. 7. In addition, FIG. 8 has a line with a drain
valve connecting the condenser portion 530 to the suction of
compressor 130. The refrigerant remaining in the second condenser
portion 530 after isolation valves 540 are closed may be stored in
the second condenser portion 530 or may be drawn into the
refrigeration system 100 by opening drain valve 840 and permitting
the refrigerant in condenser portion 530 to be drawn into the
active system. Because the refrigerant from the isolated portion of
the partitioned condenser 500 adds to the amount of refrigerant per
unit volume of the refrigeration system 100, the pressure of the
refrigerant in increased. Therefore, this addition of refrigerant
into the system from the isolated portion of the partitioned
condenser 500 further assists in raising the system pressure.
[0059] FIG. 9 shows a refrigeration system 100 incorporating a
partitioned evaporator 200 and a partitioned condenser 500
according to the present invention. FIG. 9 shows the refrigeration
system including evaporator discharge line 145, blower 160,
compressor 130, compressor discharge line 135, partitioned
condenser 500, fan 170, condenser discharge line 140, and first
heat transfer fluid 150, substantially as described above in the
description of FIG. 7. In addition, FIG. 9 includes a 3-way valve
910 and a discharge line 310. The 3-way valve 910 connects to the
first discharge header 270 of the first evaporator portion 220, to
the evaporator discharge line 145 and to the compressor discharge
line 135. FIG. 9 also shows the partitioned evaporator 200
including first and second TXV valves 260 and 265, check valve 255,
first and second distributors 240 and 245, first and second
discharge headers 270 and 275, arranged as discussed above in the
description of FIG. 3. Heat transfer fluid flow 710, preferably
air, flows into the partitioned evaporator 200 substantially evenly
across the first and second evaporator portions 220 and 230. A
blower 160 moves heat transfer fluid flow 710. Although, FIG. 9
depicts a blower, any fluid moving system is suitable for moving
the fluid across the first and second evaporator portions 220 and
230. The inlet flow 710 enters into a heat exchange relationship
with the first and second evaporator portions 220 and 230 and exits
the partitioned evaporator as outlet flow 715. During cooling mode,
the refrigerant is circulated from the partitioned condenser 500 to
the partitioned evaporator 200, through the first and second
evaporator portions 220 and 230 and to the compressor through
evaporator discharge line 145 and 3-way valve 910. The inlet flow
710 of heat transfer fluid is cooled by both the first and second
evaporator portions 220 and 230, providing outlet flow 715 of heat
transfer fluid that has been cooled. During dehumidification mode,
hot gas refrigerant from the discharge of the compressor flows into
the 3-way valve 910, which is opened to allow flow through the
first discharge header discharge line 310 and into the first
discharge header 270 of the first evaporator portion 220. One or
more controllers 720 facilitate the positioning of 3-way valve 910.
The controller 720 may receive inputs from pressure measuring or
temperature measuring devices and position the 3-way valve 910. The
hot gas refrigerant from the discharge of the compressor 130 enters
the refrigerant circuits 210 of the first evaporator portion 220
and at least partially condenses to a liquid. The condensing
refrigerant heats the first evaporator portion 220 and warms the
inlet flow 710 to produce a higher temperature outlet flow 715. The
refrigerant, which is at least partially condensed, travels through
the check valve 255 and combines with line 140 into the second
evaporator portion 230. The inlet flow 710 of heat transfer fluid
is cooled and dehumidified by the second evaporator portion 230 and
is heated by the isolated first evaporator portion 220, as the
refrigerant gas is at least partially condensed. The outlet flow
715 is a mixture of the cooled, dehumidified air that flowed
through the second evaporator portion 230 and the heated air that
flowed though the first evaporator portion 220. To summarize, the
resultant outlet flow 715 is dehumidified air that is not
overcooled. In cooling mode, first evaporator portion 220 and
second evaporator portion 230 of partitioned evaporator 200, act as
evaporators. However, in dehumidification mode, first evaporator
portion 220 acts as a condenser, while second evaporator portion
230 acts as an evaporator. The partitioned condenser 500 shown in
FIG. 9 operates substantially as described above in the discussion
of FIG. 7.
[0060] FIG. 10 shows a refrigeration system 100 incorporating a
partitioned evaporator 200 according to the present invention. FIG.
10 further shows the refrigeration system 100 including evaporator
discharge line 145, blower 160, compressor 130, compressor
discharge line 135, partitioned condenser 500, fan 170, condenser
discharge line 140, and first heat transfer fluid 150,
substantially as described above in the description of FIG. 7. In
addition, FIG. 10 includes one or both of a bypass valve 440, and a
flow restriction valve 430 on bypass line 410. Bypass line 410
connects the compressor discharge line 135 of the compressor 130 to
the inlet of the first evaporator portion 220 between the first TXV
valve 260 and the first distributor 240. One or more controllers
720 facilitate the positioning of isolation valves 540 and of the
bypass valve 440. The controller 720 may receive inputs from
pressure measuring or temperature measuring devices and position
the isolation valves 540 and bypass valve 440, e.g., open or
closed. FIG. 10 shows the partitioned evaporator 200, including
first and second TXV valves 260 and 265, isolation valve 250, first
and second distributors 240 and 245, and first and second discharge
headers 270 and 275, arranged as discussed above in the description
of FIG. 4. Inlet flow 710, preferably air, flows into the
partitioned evaporator 200 substantially evenly across the first
and second portions 220 and 230. The inlet flow 710 enters into a
heat exchange relationship with the first and second evaporator
portions 220 and 230 and exits the partitioned evaporator as outlet
flow 715. During cooling mode, the refrigerant is circulated from
the partitioned condenser 500 to the partitioned evaporator 200,
through the first and second evaporator portions 220 and 230 and to
the compressor 130 through evaporator discharge line 145. The
bypass valve 440 and the flow restriction valve 430 are set to
prevent flow of refrigerant through the bypass line 410. The inlet
flow 710 of heat transfer fluid is cooled by both the first and
second evaporator portions 220 and 230, providing outlet flow 715
of heat transfer fluid that has been cooled. During
dehumidification mode, isolation valve 250 is closed, preventing
flow of refrigerant into the first evaporator portion 220. The
bypass valve 440 is opened and the flow restriction valve 430 is
set to allow flow of refrigerant. Although FIG. 10 is shown with
both a bypass valve 440 and a flow restriction valve 430, either
the bypass valve 440 or flow restriction valve 430 may be removed
from the bypass line 410, so long as the flow of the refrigerant
may be stopped during cooling mode and permitted during
dehumidification mode. Hot gas refrigerant from the discharge of
the compressor 130 is then allowed to flow from the compressor
discharge line 135 through the bypass line 410 into the first
distributor 240 and the first evaporator portion 220. The hot gas
refrigerant from the discharge of the compressor 130 heats the
first evaporator portion 220 and combines with the outlet flow from
the second evaporator portion 230 into the evaporator discharge
line 145. The inlet flow 710 of heat transfer fluid is cooled and
dehumidified by the second evaporator portion 230 and is heated by
the hot gas from the discharge of the compressor in the isolated
first evaporator portion 220. The outlet flow 715 is a mixture of
the cooled, dehumidified air that flowed through the second
evaporator portion 230 and the heated air that flowed though the
first evaporator portion 220. The resultant outlet flow 715 is
dehumidified air that is not overcooled. The partitioned condenser
500 shown in FIG. 10 operates substantially as described above in
the discussion of FIG. 7.
[0061] FIG. 11 illustrates a flow chart detailing a method of the
present invention relating to head pressure control in a HVAC
system for use with the systems shown in FIGS. 7-10. The method
includes a determination of the minimum system head pressure, Pf,
at step 1101. The minimum head pressure is set to the desired
operating pressure of the refrigeration system 100. The minimum
head pressure is preferably greater than the pressure corresponding
to temperature of evaporator icing. Evaporator icing may occur when
the surface temperature of the evaporator and suction piping is
less than 32.degree. F. Pf is preferably the system high side
pressure that results in saturated suction temperatures above
freezing under most load conditions. For R22 refrigerant, a typical
value of Pf is 180 psig. Subsequent to determining the minimum
system head pressure, Pf, the actual system head pressure, Pm, is
measured at step 1103. Any suitable pressure measurement method can
be used for determining Pm. Preferably, the measurement takes place
on a line between the TXV valve 265 and the compressor 130.
Subsequent to the measurement taken at step 1103, a determination
of whether the measured refrigerant pressure is less than the
minimum system head pressure, Pf, at step 1105. If the measured
pressure of the refrigerant, Pm, is less than the pressure for
evaporator freezing, which corresponds to Pf, (i.e., "YES" on the
flowchart show in FIG. 11), isolation valve(s) 540 are closed and
refrigerant flow is blocked to one or more of the refrigerant
circuits inside of the partitioned condenser 500 in step 1107. If
the measured pressure of the refrigerant, Pm, is greater than the
minimum system head pressure, Pf, (i.e., "NO" on the flowchart
shown in FIG. 11), a determination of whether the measure head
pressure, Pm, is less than the system reset pressure, Pr as shown
in step 1110. If the measured pressure, Pm, is greater than the
system reset Pressure, Pr, (i.e., "YES" on the flowchart shown in
FIG. 11), the isolation valves 540, if closed, will be opened. If
the measured pressure, Pm, is less than the system reset pressure,
Pr, (i.e. "NO" on the flowchart shown in FIG. 11), then no action
will be taken regarding the isolation valves 540. If open, the
isolation valves 540 will remain open. If closed, the isolation
valves 540 will remain closed. The value Pr-Pf represents a
pressure buffer for the system so that the isolation valves 540
will not be inclined to open and close rapidly. The opening of the
isolation valves 540 in step 1109 allows refrigerant to flow to all
refrigerant circuits within the condenser. When the refrigerant
flows through all the refrigerant circuits 510 of the condenser,
the heat transfer to the first heat transfer fluid 150 from the
refrigerant is at a maximum. If the isolation valves 540 are closed
in step 1107, the refrigerant is only permitted to flow through a
portion of the partitioned condenser 500. Each portion has a
predetermined heat transfer surface area. Because the refrigerant
is only permitted to flow into a portion of the condenser and some
portions are isolated, the heat transfer area and the corresponding
amount of heat transfer is reduced. Therefore, less heat is removed
from the refrigerant. Likewise, less heat is transferred to the
first heat transfer fluid 150, thereby maintaining a higher
refrigerant temperature. Additionally, because the temperature of
the refrigerant is higher, the corresponding pressure of the
refrigerant is also higher. Therefore, the refrigerant pressure of
the system is increased.
[0062] In the HVAC system according to the present invention, when
the head pressure in the suction line 145 to the compressor 130
decreases, the temperature of the refrigerant in the evaporator 110
likewise decreases. When the head pressure has decreased to a
certain level, the partitioned evaporator 200 operates at
temperatures that may result in icing of the partitioned evaporator
200. Icing is a condition when the temperature at the exterior of
the refrigerant circuits of the evaporator is sufficiently low to
freeze water present in the heat transfer fluid. In particular, in
a residential system, the heat transfer fluid is typically air and
the water that freezes is humidity present in the air. The ice
formed by the water frozen on the surface of the refrigerant
circuits eventually prevents the proper operation of the HVAC
system by inhibiting heat transfer and/or damaging system
components. This icing generally begins at refrigerant saturated
suction temperatures from about 25.degree. F. to about 32.degree.
F. In order to prevent the freezing of the evaporator, the pressure
in the suction line 145 is preferably maintained above the
temperature that corresponds to the freezing point of the
partitioned evaporator 200.
[0063] In one method according to the invention, the pressure of
the refrigerant is measured and compared to a predetermined
pressure. The pressure measurement may be taken from any point in
the refrigeration system 100. However, the preferred point of
measurement of refrigerant pressure is on the evaporator discharge
line 145 to the compressor. The evaporator discharge line 145 to
the compressor also corresponds to the outlet of the partitioned
evaporator 200. The outlet of the partitioned evaporator 200
represents a low pressure point in the refrigeration system 100,
due to the phase change of the refrigerant to a vapor resulting
from the heat exchange relationship existing between the
refrigerant and the second heat transfer fluid 155 in the
partitioned evaporator 200. The predetermined pressure is
preferably a pressure that is greater than or equal to the pressure
that corresponds to a temperature that results in icing at the
partitioned evaporator 200.
[0064] FIG. 12 shows a control method according to one embodiment
of the present invention for use with the system shown in FIGS.
7-8. The method includes a mode determination step 1210 where the
operational mode of the system is determined or selected. The
operational mode can be provided by the controller and/or user,
where the mode can either be cooling only or require
dehumidification. Examples of control systems for determination of
the operational mode are described in further detail below in the
discussion of FIGS. 15 and 16. The method then includes a
decisional step 1220 wherein it is determined whether
dehumidification is required or not. If the determination in step
1220 is "NO" (i.e., no dehumidification required), then the method
proceeds to opening step 1230 wherein the valve to the first
evaporator portion 220 is opened or remains open in step 1230. The
opening of the first evaporator portion 220 to the flow of
refrigerant permits both the first and second evaporator portions
220 and 230 to provide cooling to the inlet flow 710. If the
decisional step 1220 is a "YES" (i.e., dehumidification is
required), then the valve to the first evaporator portion 220 is
closed or remains closed in step 1240. The closing of the first
evaporator portion 220 to the flow of refrigerant allows the first
evaporator portion 220 to equilibrate at a temperature
substantially equal to the temperature of the heat transfer fluid
entering the partitioned evaporator 200. After either the opening
step 1230 or the closing step 1240, the method returns to the
determination step 1210 and the method repeats.
[0065] Although FIG. 12 shows that the decisional step 1220
provides a "YES" or "NO" to steps 1230 or 1240, the method is not
limited to an open or closed isolation valve 250. A
flow-restricting valve may also be used. The use of a
flow-restricting valve allows the amount of flow into the first
evaporator portion 220 to be varied. For example, the flow
restricting valve may be used in an operational mode that is open
to full flow, partially restricted flow or closed to flow,
depending on the signal from a controller. Controller 720, using
inputs, such as refrigerant temperature, heat transfer fluid
temperatures, and humidity readings, provides a signal to the
restricting valve to determine the amount of refrigerant flow
permitted through the isolation valve 250.
[0066] FIG. 13 shows another control method according to the
present invention for use with the system shown in FIG. 9. The
method includes a mode determination step 1310 where the
operational mode of the system is determined. As in the method
shown in FIG. 12, the operational mode can be provided by the
controller and/or user, where the mode can either be cooling only
or dehumidification. Examples of control systems for determination
of the operational mode are described in further detail below in
the discussion of FIGS. 15 and 16. The method then includes a
decisional step 1320 wherein it is determined whether
dehumidification is required or not. If the determination in step
1320 is "NO" (i.e., no dehumidification required), then the method
proceeds to step 1330 wherein the 3-way valve 910 is set to provide
refrigerant flow from the discharge line 310 of the evaporator
portion 220 to the compressor suction line 145. The setting of the
3-way valve 910 allows the flow of refrigerant to both the first
and second evaporator portions 220 and 230 to provide cooling to
the inlet flow 710. If the decisional step 1320 is a "YES" (i.e.,
dehumidification is required), then the 3-way valve 910 is set to
provide refrigerant flow from the discharge of the compressor to
the discharge line 310 of the evaporator portion 220. The hot gas
refrigerant from the discharge of the compressor 130 flows into the
first evaporator portion 220 and provides heat to the first
evaporator portion 220. The directing of hot gas refrigerant to the
first evaporator portion 220 allows the first evaporator portion
220 to exchange heat with the heat transfer fluid 155 entering the
partitioned evaporator 200. The inlet flow 155 of heat transfer
fluid is cooled and dehumidified by the second evaporator portion
230 and is heated by heat exchange with the hot gas from the
discharge of the compressor 130 in the isolated first evaporator
portion 220. The outlet flow 715 is a mixture of the cooled,
dehumidified air that flowed through the second evaporator portion
230 and the heated air that flowed though the first evaporator
portion 220. The resultant outlet flow 715 is dehumidified air that
is not overcooled. After either the 3-way valve 910 directing steps
1330 or 1340, the method returns to the determination step 1310 and
the method repeats.
[0067] Although FIG. 13 shows that the decisional step 1320
provides a "YES" or "NO" to steps 1330 or 1340, the method is not
limited to an open or closed isolation valve 250. A flow
restriction valve may also be used. The use of a flow restriction
valve allows the amount of flow into the first evaporator portion
220 to be varied. For example, the flow restriction valve may be
used in an operational mode that is open to full flow, partially
restricted flow or closed to flow, depending on the signal from
controller 720. Alternatively, the flow into the first evaporator
portion 220 from the discharge of the compressor 130 in
dehumidification mode may be varied through use of the 3-way valve
910, depending on the signal from a controller. The 3-way valve 910
may also include flow restriction abilities that allow the flow of
refrigerant to be varied. A controller, using inputs, such as
refrigerant temperature, heat transfer fluid temperatures, and
humidity readings, provides a signal to the restriction valve or
the 3-way valve 910 to determine the amount of refrigerant flow
permitted through the isolation valve 250 or the amount of hot gas
refrigerant permitted through the first evaporator portion 220.
[0068] FIG. 14 shows a control method according to the present
invention for use with the system shown in FIG. 10. The method
includes a mode determination step 1410 where the operational mode
of the system is determined. As in the method shown in FIGS. 12 and
13, the operational mode can be provided by controller 720 and/or
user, where the mode can either be cooling only or
dehumidification. The method then includes a decisional step 1420
wherein it is determined whether dehumidification is required or
not. If the determination in step 1420 is "NO" (i.e., no
dehumidification required), then the method proceeds to step 1430
wherein the valve 250 to the first evaporator portion 220 is opened
or remains open. After or concurrently with step 1430, a bypass
line 410 is closed from refrigerant flow in step 1340. The opening
of the first evaporator portion 220 and the closing of the bypass
line 410 allow the flow of refrigerant to both the first and second
evaporator portions 220 and 230 to provide cooling to the inlet
flow 710. If the decisional step 1420 is a "YES" (i.e.,
dehumidification is required), then the valve to the first
evaporator portion 220 is closed or remains closed. After or
concurrently with step 1450, the bypass line 410 is opened to flow
of refrigerant in step 1460. Hot gas refrigerant from the discharge
of the compressor 130 flows through the bypass 410 and into the
first evaporator portion 220 and provides heat to the first
evaporator portion 220. The closing of the first evaporator portion
220 to the flow of refrigerant from the condenser 130 and the
directing of hot gas refrigerant to the first evaporator portion
220 allows the first evaporator portion 220 to exchange heat with
the refrigerant circuits 510 entering the partitioned evaporator
200. The inlet flow 710 of heat transfer fluid is cooled and
dehumidified by the second evaporator portion 230 and is heated by
heat exchange with the hot gas from the discharge of the compressor
in the isolated first evaporator portion 220. The outlet flow 715
is a mixture of the cooled, dehumidified air that flowed through
the second evaporator portion 230 and the heated air that flowed
though the first evaporator portion 220. The resultant outlet flow
715 is dehumidified air that is not overcooled. After either the
bypass-closing step 1440 or the bypass-opening step 1460, the
method returns to the determination step 1410 and the method
repeats.
[0069] Although FIG. 14 shows that the decisional step 1420
provides a "YES" or "NO" to steps 1430 or 1450, the method is not
limited to an open or closed isolation valve 250. A flow
restriction valve may also be used. The use of a flow restriction
valve allows the amount of flow into the first evaporator portion
220 to be varied. For example, the flow restriction valve may be
used in an operational mode that is open to full flow, partially
restricted flow or closed to flow, depending on the signal from
controller 720. Additionally, the flow through the bypass line 410
may be varied through use of the bypass valve 440 and/or flow
restriction valve 430, depending on the signal from controller 720.
Controller 720, using inputs, such as refrigerant temperature, heat
transfer fluid temperatures, and humidity readings, provides a
signal to isolation valve 250, bypass valve 440 and flow
restriction valve 430 to determine the amount of refrigerant flow
permitted through the flow restriction valve 430 in place of
isolation valve 250 and the amount of hot gas refrigerant permitted
through the first evaporator portion 220.
[0070] FIG. 15 illustrates a control method according to the
present invention that determines the operation mode of the
partitioned evaporator 200. The determination of the operational
mode is made through the use of controller 720. This determination
may be used in steps 1210, 1310 and 1410 of FIGS. 12, 13 and 14,
respectively. The determination takes place by first sensing
temperature and/or humidity in an enclosed space in step 1510. The
temperature and/or humidity measurements are made for a controller
to determine whether the enclosed space requires cooling or
dehumidification. The inputs from temperature sensors and humidity
sensors are provided to controller 720 in step 1520, where the
controller uses the sensed temperatures and/or humidity to
determine the operational mode. In step 1520, the controller
determines whether cooling is required and whether dehumidification
is required. In a first decisional step 1530, it is determined
whether the controller has determined that cooling is required. If
the first decisional step 1530 determines "YES", cooling mode is
required, the partitioned evaporator 200 in the refrigeration
system 100 is set to allow flow into all of the refrigerant
circuits 210 in the partition evaporator 200 and cool across both
the first and second evaporator portions 220 and 230 in step 1540.
In addition to cooling, cooling mode also performs
dehumidification. However, in a cooling mode, the second heat
transfer fluid is only cooled and is not heated to increase the
temperature of the second heat transfer fluid 155 once the second
heat transfer fluid 155 travels through the partitioned evaporator
200. If the first decisional step 1530 determines "NO", then a
second decisional step 1550 is made. The second decisional step
1550 determines whether the controller has determined that
dehumidification mode (i.e., dehumidification without overcooling)
is required. If the second decisional step 1550 determines "YES",
dehumidification mode is required, the operational mode is set to
dehumidification in step 1560. If the second decisional step 1550
determines "NO", dehumidification mode is not required, the
operational mode is set to inactive and the system operates neither
a cooling nor a dehumidification cycle in step 1570.
[0071] FIG. 16 shows an alternate control method according to the
present invention that determines the operation mode of a multiple
refrigerant circuit system. In the system controlled in FIG. 16,
multiple refrigerant systems 100 are utilized and one or more of
the refrigerant systems 100 include a partitioned evaporator 200
according to the invention. The control method shown in FIG. 16
operates in a similar manner to FIG. 15 in that the controller
receives inputs from temperature and/or humidity sensors in step
1610 and determines the operational mode of the system in step
1620. Likewise, if the first decisional step 1630 determines "NO",
then a second decisional step 1650 is performed. The second
decisional step 1670 determines whether the controller has
determined that a dehumidification mode (i.e., dehumidification
without overcooling) is required. If the second decisional step
1670 determines "YES", dehumidification mode is required, the
operational mode is set to dehumidification in step 1680. If
multiple refrigerant systems 100 are present, the controller 720
independently determines which of the refrigerant systems 100 are
active or inactive, based upon temperature and/or humidity
measurements. When multiple refrigeration systems 100 are present,
at least one refrigerant system 100 includes a partitioned
evaporator 200. The controller 720 independently determines which
partitioned evaporator 200 is subject to isolation of the first
evaporator portion 220, based upon temperature and/or humidity
measurements. However, if the second decisional step 1670
determines "NO", dehumidification is not required, the operational
mode is set to inactive and the system operates neither a cooling
nor a dehumidification cycle in step 1690. If the first decisional
step 1630 determines "YES", cooling is required, a third decisional
step 1640 is performed. In the third decisional step 1640, a
determination is made as to the number of stages to be activated in
order to provide the cooling. Each stage has an evaporator capable
of providing cooling to the second heat transfer fluid 155. The
greater the number of stages activated, the greater the amount of
cooling provided. At least one of the multiple refrigerant circuits
includes a partitioned evaporator 200. If the controller determines
that the cooling demand only requires one refrigerant system 100 to
be active, one refrigerant system 100 will be used to cool second
heat transfer fluid 155 in step 1650. When the partitioned
evaporator 200 is used to operate in cooling mode, the partitioned
evaporator 200 is configured to allow flow into all of the
refrigerant circuits 210 in the partition evaporator 200 and cool
across both the first and second evaporator portions 220 and 230 in
step 1660. If multiple partitioned evaporators 200 are present, all
of the refrigerant circuits 210 in each of the partition
evaporators 200 allow flow of refrigerant into both the first and
second evaporator portions 220 and 230 and cool the second heat
transfer fluid 155.
[0072] The present invention is not limited to the control methods
shown in FIGS. 11-16. The partitioned evaporator 200 and the
partitioned condenser 500 may be used in one or more refrigerant
circuits of multiple refrigerant circuit systems, where the control
of the reheating capabilities within the first evaporator portion
220 of the partitioned evaporator 200 and the head pressure control
within the first condenser portion 520 may each be independently
controlled to provide the desired temperature and/or humidity
within the conditioned space and the desired refrigerant pressure
within the system. Any combination of cooling, reheating, or
modulation of combinations of cooling and reheating may be used
with the present invention. In addition, operational modes
controlling the refrigerant pressure may be used in conjunction
with the cooling and dehumidification modes of operation.
[0073] While the invention has been described with reference to a
preferred embodiment, it will be understood by those skilled in the
art that various changes may be made and equivalents may be
substituted for elements thereof without departing from the scope
of the invention. In addition, many modifications may be made to
adapt a particular situation or material to the teachings of the
invention without departing from the essential scope thereof.
Therefore, it is intended that the invention not be limited to the
particular embodiment disclosed as the best mode contemplated for
carrying out this invention, but that the invention will include
all embodiments falling within the scope of the appended
claims.
* * * * *