U.S. patent application number 10/891589 was filed with the patent office on 2006-01-19 for hvac&r humidity control system and method.
This patent application is currently assigned to YORK INTERNATIONAL CORPORATION. Invention is credited to Ronald Richard Rayburn.
Application Number | 20060010891 10/891589 |
Document ID | / |
Family ID | 35597977 |
Filed Date | 2006-01-19 |
United States Patent
Application |
20060010891 |
Kind Code |
A1 |
Rayburn; Ronald Richard |
January 19, 2006 |
HVAC&R humidity control system and method
Abstract
A controller controls operation of a HVAC&R device to reduce
an interior humidity level for a structure to provide comfort for
occupants of the structure. The controller includes a first sensor
for sensing a temperature inside a structure and a second sensor
for sensing a humidity level inside the structure. A controller is
responsive to the first and second sensors for the HVAC&R
device operating in a cooling mode to reduce the humidity level
inside the structure. The controller calculates a temperature
correction to a predetermined temperature setting for the
HVAC&R device, the temperature correction calculation being
obtained by subtracting the sensed humidity level from a
predetermined humidity level and dividing the result by a
predetermined factor. The controller initiates operation of the
HVAC&R device when the sum of the sensed temperature and the
temperature correction is greater than the predetermined
temperature.
Inventors: |
Rayburn; Ronald Richard;
(Norman, OK) |
Correspondence
Address: |
MCNEES, WALLACE & NURICK LLC
100 PINE STREET
P.O. BOX 1166
HARRISBURG
PA
17108-1166
US
|
Assignee: |
YORK INTERNATIONAL
CORPORATION
York
PA
|
Family ID: |
35597977 |
Appl. No.: |
10/891589 |
Filed: |
July 15, 2004 |
Current U.S.
Class: |
62/176.6 |
Current CPC
Class: |
F24F 2120/20 20180101;
F24F 11/0008 20130101; F24F 2110/10 20180101; F24F 11/30 20180101;
G05D 27/02 20130101; F24F 2110/20 20180101 |
Class at
Publication: |
062/176.6 |
International
Class: |
F25D 17/04 20060101
F25D017/04; F25B 49/00 20060101 F25B049/00 |
Claims
1. A method for controlling humidity in a structure with a
HVAC&R system, the method comprising the steps of: sensing a
temperature and a humidity level inside a structure; calculating a
temperature correction value in response to a predetermined
humidity level, the sensed humidity level and a predetermined
humidity sensitivity factor; comparing a predetermined temperature
setting for a HVAC&R device with the sum of the sensed
temperature and the temperature correction value; and initiating
operation of the HVAC&R device to reduce the humidity level
inside the structure when the sum of the sensed temperature and the
temperature correction value is greater than the predetermined
temperature setting.
2. The method of claim 1 further comprising the step of selecting
the predetermined humidity level, the predetermined temperature
setting and the predetermined humidity sensitivity factor.
3. The method of claim 1 wherein the predetermined humidity
sensitivity factor is between about 1 and about 10.
4. The method of claim 1 wherein the predetermined humidity level
is greater than about 45 percent.
5. The method of claim 1 further including, after the step of
initiating operation of the HVAC&R device, the step of
repeating the steps of sensing a temperature and a humidity level,
calculating a temperature correction value, comparing a
predetermined temperature setting and initiating operation of the
HVAC&R device.
6. The method of claim 1 wherein the step of calculating a
temperature correction value includes the steps of: subtracting a
predetermined humidity level from the sensed humidity level to
generate a humidity difference; dividing the humidity difference by
the predetermined humidity sensitivity factor to generate the
temperature correction value.
7. The method of claim 1 wherein the step of calculating a
temperature correction value includes the steps of: comparing the
temperature correction value to a maximum temperature correction;
changing the temperature correction value to the maximum
temperature correction in response to the temperature correction
value being greater than the maximum temperature correction.
8. A controller for controlling humidity in a structure with a
HVAC&R system, the controller comprising: a first sensor for
sensing a temperature inside a structure and a second sensor for
sensing a humidity level inside the structure; a controller
responsive to the first and second sensors for a HVAC&R device,
the controller calculating a temperature correction value in
response to a predetermined humidity level, the sensed humidity
level and a predetermined humidity sensitivity factor; and wherein
the controller initiating operation of the HVAC&R device to
reduce the humidity level inside the structure when the sum of the
sensed temperature and the temperature correction value is greater
than the predetermined temperature setting.
9. The controller of claim 8 wherein the predetermined humidity
sensitivity factor is between about 1 to about 10.
10. The controller of claim 8 wherein the predetermined humidity
level is greater than about 45 percent.
11. The controller of claim 8 wherein the structure is a commercial
building.
12. The controller of claim 8 wherein the structure is a
residential building.
13. The controller of claim 8 wherein the temperature correction
value is calculated by subtracting a predetermined humidity level
from the sensed humidity level to generate a humidity difference,
and then dividing the humidity difference by the predetermined
humidity sensitivity factor to generate the temperature correction
value.
14. The controller of claim 8 wherein the temperature correction
value is calculated by comparing the temperature correction value
to a maximum temperature correction, and then changing the
temperature correction value to the maximum temperature correction
in response to the temperature correction value being greater than
the maximum temperature correction.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates generally to a control
application for a HVAC&R system. More specifically, the present
invention relates to a system and method for humidity control in a
HVAC&R system.
[0002] To achieve climate control for a structure or enclosed
space, a heating, ventilation, air conditioning and refrigeration
(HVAC&R) or air treatment system is commonly used. The
HVAC&R system is typically thermostat controlled to provide
temperature control for the interior space of the structure.
However, in addition to temperature, other parameters are
significant for providing comfort to the occupants within the
structure. For example, relative humidity, or the ratio of the
amount of water vapor actually present in the air to the greatest
amount possible at the same temperature, is one such parameter. At
increased levels of relative humidity, the temperature must be
lowered to provide an equivalent level of comfort for an
individual. Complicating matters, individual sensitivity to changes
in humidity and temperature differ, so that it is not possible to
provide a definitive temperature correction when humidity levels
are elevated.
[0003] Several techniques have been used to control humidity within
a structure. These techniques typically include a combination of
reheating and/or cooling the air. Cooling the air, such as by
passing the air through evaporator coils, removes moisture from the
air since an amount of the air moisture collects and condenses on
the evaporator coils. Heating may then need to be performed to
raise the air temperature to a level that is comfortable to the
occupant. Having both heating and cooling adds HVAC&R
components, complexity and cost.
[0004] What is needed is a control for use with HVAC&R systems
that is simple to operate, and which can provide an individualized
temperature/humidity correction inside a structure in response to
elevated humidity levels.
SUMMARY OF THE INVENTION
[0005] The present invention is directed to a method for
controlling humidity in a structure with a HVAC&R system. The
method steps include: sensing a temperature and a humidity level
inside a structure; calculating a temperature correction value in
response to a predetermined humidity level, the sensed humidity
level and a predetermined humidity sensitivity factor; comparing a
predetermined temperature setting for a HVAC&R device with the
sum of the sensed temperature and the temperature correction value;
and initiating operation of the HVAC&R device to reduce the
humidity level inside the structure when the sum of the sensed
temperature and the temperature correction value is greater than
the predetermined temperature setting.
[0006] The present invention further includes a controller for
controlling humidity in a structure with a HVAC&R system. The
controller includes a first sensor for sensing a temperature inside
a structure and a second sensor for sensing a humidity level inside
the structure. A controller is responsive to the first and second
sensors for a HVAC&R device, the controller calculating a
temperature correction value in response to a predetermined
humidity level, the sensed humidity level and a predetermined
humidity sensitivity factor. The controller initiates operation of
the HVAC&R device to reduce the humidity level inside the
structure when the sum of the sensed temperature and the
temperature correction value is greater than the predetermined
temperature setting.
[0007] One advantage of the present invention is that it reduces
elevated humidity levels within a structure.
[0008] Another advantage of the present invention is that it can
provide a selectable relationship between temperature and elevated
humidity levels within a structure.
[0009] A further advantage of the present invention is that it
requires a minimum amount of memory to operate.
[0010] A yet further advantage of the present invention is that it
is extremely simple to operate.
[0011] 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
[0012] FIG. 1 illustrates schematically an embodiment of a heating,
ventilation and air conditioning or refrigeration system for use
with the present invention.
[0013] FIG. 2 illustrates a flow chart detailing the humidity
control method of the present invention.
[0014] 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
[0015] One embodiment of the heating, ventilation and air
conditioning or refrigeration (HVAC&R) system 10 of the present
invention is depicted in FIG. 1. Compressor 12 is connected to a
motor 14 and inverter or variable speed drive (VSD) 16, for
selectively controlling operational parameters, such as rotational
speed, of the compressor 12. Compressor 12 is typically a positive
displacement compressor, such as screw, reciprocating or scroll,
having a wide range of cooling capacity, although any type of
compressor can also be used. The controller 20 includes logic
devices, such as a microprocessor or other electronic components,
for controlling the operating parameters of compressor 12 by
controlling VSD 16 and motor 14. AC electrical power received from
an electrical power source 18 is rectified from AC to DC, and then
inverted from DC back to variable frequency AC by VSD 16 for
driving compressor motor 14. The compressor motor 14 is typically
an AC induction motor, but might also be brushless permanent magnet
motor or switched reluctance motor.
[0016] Refrigerant gas that is compressed by compressor 12 is
directed to the condenser 22, which enters into a heat exchange
relationship with a fluid, preferably water, flowing through a
heat-exchanger coil 24 connected to a cooling tower 26. The
refrigerant vapor in the condenser 22 undergoes a phase change to a
refrigerant liquid as a result of the heat exchange relationship
with the liquid in the heat-exchanger coil 24. The condensed liquid
refrigerant from condenser 22 flows to an expansion device 28,
which lowers the pressure of the refrigerant before entering the
evaporator 30. Alternately, the condenser 22 can reject the heat
directly into the atmosphere through the use of air movement across
a series of finned surfaces (direct expansion condenser).
[0017] The evaporator 30 can include a heat-exchanger coil 34
having a supply line 34S and a return line 34R connected to a
cooling load 36. The heat-exchanger coil 34 can include a plurality
of tube bundles within the evaporator 30. Water or any other
suitable secondary refrigerant, e.g., ethylene, calcium chloride
brine or sodium chloride brine, travels into the evaporator 30 via
return line 34R and exits the evaporator 30 via supply line 34S.
The liquid refrigerant in the evaporator 30 enters into a heat
exchange relationship with the water in the heat-exchanger coil 34
to chill the temperature of the water in the heat-exchanger coil
34. The refrigerant liquid in the evaporator 30 undergoes a phase
change to a refrigerant gas as a result of the heat exchange
relationship with the liquid in the heat-exchanger coil 34. The gas
refrigerant in the evaporator 30 then returns to the compressor
12.
[0018] Controller 20, which controls the operations of HVAC&R
system 10, employs continuous feedback from indoor temperature
sensor 38 and humidity sensor 40 to continuously determine whether
to incorporate a temperature correction to achieve a reduction in
the humidity level within the structure being cooled by the system
10. In other words, the humidity reduction control of the present
invention is preferably used when the HVAC&R system 10 is in a
cooling mode.
[0019] The HVAC&R system 10 is first discussed without
considering the humidity sensor 40. An operator initially inputs a
desired temperature setting "T.sub.D", or settings if multiple
temperatures are to be achieved at different times of the day or
different days, which are typically referred to as programmed
settings. Once the desired temperature setting(s) T.sub.D have been
input, the sensed temperature inside a structure "T.sub.S" as
sensed by the indoor temperature sensor 38 is compared to the
desired temperature setting T.sub.D which was previously input into
the controller 20 by the operator. When the inside temperature
T.sub.S of the structure as sensed by the indoor temperature sensor
38 is greater than the desired temperature setting T.sub.D, the
controller 20 activates the HVAC&R system 10 to operate in
cooling mode. The HVAC&R system 10 continues to operate in
cooling mode until the desired temperature setting is achieved,
wherein upon achieving the desired setting, the HVAC&R system
10 is deactivated. This process is then repeated to provide
temperature control inside of the structure.
[0020] While providing temperature control of the temperature
inside of the structure, other parameters important to the comfort
of the occupants of the structure, such as humidity control, are
not taken into account in the above-referenced process. The
HVAC&R system 10 is again discussed, with the addition of the
humidity sensor 40, which senses a relative humidity percentage
inside the structure "H.sub.S", and a corresponding control
algorithm that is programmed into the controller 20. In addition to
initially inputting a desired temperature setting(s) T.sub.D, an
operator additionally inputs a desired relative humidity percentage
"H.sub.D" and a humidity sensitivity factor "H.sub.stv". A humidity
sensitivity factor "H.sub.stv" is a correction factor that
correlates an excess in percentage of the relative humidity inside
the structure to a reduction of the temperature inside the
structure, which reduction in temperature being referred to as a
temperature correction "T.sub.C". More specifically, the
temperature correction T.sub.C can be calculated by subtracting the
desired relative humidity percentage H.sub.D from the sensed
relative humidity H.sub.S, and dividing that result by the humidity
sensitivity factor H.sub.stv as shown in equation 1.
T.sub.C=(H.sub.S-H.sub.D)/H.sub.stv [1]
[0021] Stated another way, a humidity sensitivity factor of 5, for
example, means that for every 5 percent the sensed humidity
percentage H.sub.S, as sensed by the humidity sensor 40, exceeds
the desired relative humidity percentage H.sub.S, the temperature
correction T.sub.C inside the structure must be lowered by one
.degree. F. to achieve a similar level of comfort due to the
humidity. The humidity sensitivity factor H.sub.stv is subjective,
possibly differing for each individual, and can range from about 1
up to about 10, although typically it is about 5 or less.
[0022] In operational example, assume the following input values:
desired relative humidity percentage H.sub.D is 50 percent, the
humidity sensitivity factor H.sub.stv is 5, the desired temperature
setting TD is 70.degree. F. and a maximum correction temperature
"T.sub.CMAX" is 5. The maximum correction temperature T.sub.CMAX is
an operator-input maximum deviation temperature from the desired
temperature T.sub.D. Further assume a sensed relative humidity
H.sub.S of 80 percent and a sensed inside structure temperature
T.sub.S of 70.degree. F. In a conventional HVAC&R system, since
the sensed inside structure temperature T.sub.S and the desired
temperature setting T.sub.D are equal, the HVAC&R system would
remain deactivated. However, since the sensed relative humidity
H.sub.S is greater than the desired relative humidity H.sub.D,
occupants within the structure can be made more comfortable by
cooling the temperature within the structure as provided by the
control algorithm. The temperature correction T.sub.C as provided
by equation [1] is calculated as follows: (80-50)/5, which
simplifies to 6.degree. F. However, in this example, the maximum
correction temperature T.sub.CMAX is 5, or 5.degree. F., so the
maximum correction temperature value is applied in place of the
calculated correction temperature. By application of the control
algorithm in this example, the equivalent temperature inside the
structure is reduced by the maximum correction temperature
T.sub.CMAX, so that the HVAC&R system is activated to operate
until the temperature inside the structure is lowered to 65.degree.
F., at which point the HVAC&R system is deactivated.
[0023] In summary, for the above example, occupants inside the
structure are made more comfortable by operation of the control
algorithm, since the elevated level of relative humidity is reduced
as the air inside the structure is passed through the evaporator
coils for the additional time required to cool the structure by the
amount of temperature correction T.sub.C. This process is then
repeated to provide temperature and humidity control inside of the
structure.
[0024] After the control algorithm completes a cycle, especially
when the sensed relative humidity H.sub.S is significantly greater
than the desired relative humidity H.sub.D, the reduction of the
sensed relative humidity H.sub.S is typically sufficient to
likewise reduce the amount of temperature correction T.sub.C. In
the above example, after the temperature inside the structure is
lowered to 65.degree. F., if the relative humidity inside the
structure is reduced to 70 percent, the temperature correction of
equation [1] is calculated as follows: (70-50)/5, which simplifies
to 4.degree. F. By application of the algorithm, the equivalent
temperature inside the structure is reduced by less than the
maximum correction temperature T.sub.CMAX, or 4.degree. F. Thus,
upon the temperature inside the structure being sufficiently raised
to activate the HVAC&R system, the HVAC&R system operates
until the temperature inside the structure is lowered to 66.degree.
F., at which point the HVAC&R system is deactivated. In other
words, so long as the control algorithm removes more moisture from
the air inside the structure than is added, such as by activities
of the occupants or by moisture producing processes occurring
within the structure, the temperature correction should continue to
decrease. As the relative humidity inside the structure is reduced
to the desired humidity level, the temperature correction
approaches zero.
[0025] Although the desired relative humidity level could be set to
an extremely low level, such as thirty percent or less, there is
typically little benefit, from a comfort standpoint, to reduce the
humidity below a level of about 45 percent.
[0026] The controller 20 can include an analog to digital (A/D)
converter, a microprocessor, a non-volatile memory, and an
interface board to control operation of the HVAC&R system 10.
The controller 20 can also be used to control the operation of the
VSD 16, the motor 14 and the compressor 12. The controller 20
executes a control algorithm(s) or software to control operation of
the system 10. In one embodiment, the control algorithm(s) can be
computer programs or software stored in the non-volatile memory of
the controller 20 and can include a series of instructions
executable by the microprocessor of the controller 20. While it is
preferred that the control algorithm be embodied in a computer
program(s) and executed by the microprocessor, it is to be
understood that the control algorithm may be implemented and
executed using digital and/or analog hardware by those skilled in
the art. If hardware is used to execute the control algorithm, the
corresponding configuration of the controller 20 can be changed to
incorporate the necessary components and to remove any components
that may no longer be required.
[0027] FIG. 2 illustrates a flow chart detailing the control
process of the present invention relating to cooling control in an
HVAC&R system 10, as shown in FIG. 1, wherein control is
maintained by the thermostat (not shown). The cooling control
process of FIG. 2 can also be implemented as a separate control
program executed by a microprocessor, or control panel, or
controller 20 or the control process can be implemented as a
sub-program in the control program for the HVAC&R system 10.
Once the process is started in step 105 of FIG. 2, values are
selected and set for the desired humidity percentage H.sub.D, the
humidity sensitivity factor H.sub.stv, desired temperature T.sub.D
and the maximum temperature correction T.sub.CMAX in step 110.
Controller keypads on existing controllers 20 or other suitable
entry devices can be used with the control algorithm and can be
used to enter all required parameters. After the desired humidity
percentage H.sub.D, humidity sensitivity factor H.sub.stv, desired
temperature T.sub.D and maximum temperature correction T.sub.CMAX
are set, the temperature inside the structure T.sub.S as sensed by
the indoor temperature sensor 38 and the relative humidity H.sub.S
as sensed by the humidity sensor 40 are sensed in step 115. Once
the temperature inside the structure T.sub.S and the relative
humidity H.sub.S are sensed, the sensed relative humidity H.sub.S
is compared to the desired humidity percentage H.sub.D in step
120.
[0028] In step 120, if the sensed relative humidity H.sub.S is
greater than the desired humidity percentage H.sub.D, then a
calculation is performed to determine the humidity correction
temperature T.sub.C in step 125. However, if in step 120, the
sensed relative humidity H.sub.S is not greater than the desired
humidity percentage H.sub.D, a humidity temperature correction is
not greater than zero, the humidity temperature correction T.sub.C
is set to zero in step 140 and control of the process is returned
to step 145.
[0029] Once the humidity temperature correction T.sub.C in step 125
has been calculated, the humidity temperature correction T.sub.C is
compared to the maximum temperature correction T.sub.CMAX in step
130. If the humidity correction temperature T.sub.C is greater than
the maximum temperature correction T.sub.CMAX in step 130, the
humidity temperature correction T.sub.C is set equal to the maximum
temperature correction T.sub.CMAX in step 135 and control of the
process is returned to step 145. However, if the humidity
temperature correction T.sub.C is not greater than the maximum
temperature correction T.sub.CMAX in step 130, the value of the
humidity temperature correction T.sub.C is retained, and control of
the process is returned to step 145.
[0030] In step 145, the desired temperature T.sub.D is compared to
the resulting value obtained by adding the humidity temperature
correction T.sub.C and the sensed temperature inside the structure
T.sub.S. If the desired temperature T.sub.D is less than the
resulting value obtained by adding the humidity correction
temperature T.sub.C and the sensed temperature inside the structure
T.sub.S, the HVAC&R system 10 is activated in step 150 and
control of the process is returned to step 145. However, if in step
145 the desired temperature T.sub.D is greater than the resulting
value obtained by adding the humidity correction temperature
T.sub.C and the sensed temperature inside the structure T.sub.S, a
query is performed as to whether the HVAC&R system 10 is
activated in step 155. If the HVAC&R system 10 is activated,
the HVAC&R system 10 is deactivated in step 160 and control of
the process is returned to step 115, wherein the process between
steps 115-160 are repeated. However, if the HVAC&R system 10 is
not activated in step 155, control of the process is returned to
step 115, wherein the process between steps 115-160 are
repeated.
[0031] In another embodiment, after activating the HVAC&R
system 10 in step 150, the control can return to step 115 and steps
115-160 can be repeated.
[0032] In addition to use with commercial HVAC&R systems,
including roof-mounted configurations, the control process of the
present invention can also be used with residential structures. The
residential structures include split systems where the condenser is
located outside the structure.
[0033] 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.
* * * * *