Title:
Method for controling air flow rate of air conditioning system
Kind Code:
A1


Abstract:
Method for controlling an air flow rate of an air conditioning system, including the steps of measuring a concentration of volatile organic compounds in air periodically, calculating a value of concentration change from concentration values measured at the present time and in the past, and controlling the flow rate of air for cleaning or ventilating a room with reference to the present concentration and value of concentration change, whereby controlling a flow rate of room cleaning or ventilating air to cope, not only with concentration of organic compounds, but also with rapid change of the concentration of the organic compounds in the air.



Inventors:
Kim, Kyung Hwan (Seoul, KR)
Choi, Ho Seon (Sadang-dong, KR)
Yum, Kwan Ho (Seoul, KR)
Application Number:
10/911495
Publication Date:
07/21/2005
Filing Date:
08/05/2004
Assignee:
LG Electronics Inc. (Seoul, KR)
Primary Class:
Other Classes:
236/49.3
International Classes:
F24F7/00; F24F11/00; (IPC1-7): F24F7/00; F25B17/00; F25D17/04
View Patent Images:
Related US Applications:



Primary Examiner:
PETTITT, JOHN F
Attorney, Agent or Firm:
Dentons US LLP (Washington, DC, US)
Claims:
1. A method for controlling an air flow rate of an air conditioning system, comprising the steps of: (a) measuring a concentration of volatile organic compounds in air, periodically; (b) calculating a value of concentration change from concentration values measured at the present time and in the past; and (c) controlling the flow rate of air for cleaning or ventilating a room with reference to the present concentration and value of concentration change.

2. The method as claimed in claim 1, wherein the value of concentration change in the step (b) is a difference of a concentration value measured at the present time and a concentration value measured right before.

3. The method as claimed in claim 1, wherein the flow rate of the air for cleaning or ventilating a room includes a highest flow rate, a high flow rate, a medium flow rate, and a lowest flow rate.

4. The method as claimed in claim 3, wherein the flow rate of the air for cleaning or ventilating a room is controlled to be the highest flow rate when the concentration value is high, and the value of concentration change is high or medium.

5. The method as claimed in claim 3, wherein the flow rate of the air for cleaning or ventilating a room is controlled to be the high flow rate when the concentration value is high, and the value of concentration change is low, or the concentration value is medium, and the value of concentration change is high.

6. The method as claimed in claim 3, wherein the flow rate of the air for cleaning or ventilating a room is controlled to be the medium flow rate when the concentration value is medium, and the value of concentration change is medium or low, or the concentration value is low, and the value of concentration change is high.

7. The method as claimed in claim 3, wherein the flow rate of the air for cleaning or ventilating a room is controlled to be the lowest flow rate when the concentration value is low, and the value of concentration change is medium of low.

8. The method as claimed in claim 1, wherein the flow rate of the air for cleaning the room is controlled by controlling a rotation speed of a fan which draws air from the room and discharges the air to the room, again.

9. The method as claimed in claim 1, wherein the flow rate of the air for ventilating the room is controlled by controlling a rotation speed of a fan which draws outdoor air and discharges the outdoor air to the room.

10. The method as claimed in claim 1, wherein the flow rate of the air for ventilating the room is controlled by controlling a rotation speed of a fan which draws room air and discharges the room air to an outside of the room.

11. The method as claimed in claim 1, wherein the step (c) includes the steps of; (c1) determining a level of the concentration value measured at the present time, (c2) determining a level of the value of the concentration change calculated at the present time, and (c3) controlling a rotation speed of at least one of a first fan for supplying air to the room and a second fan for discharging air from the room with reference to the levels of the concentration value and the value of the concentration change.

12. The method as claimed in claim 11, wherein the step (c1) includes the step of comparing the measured concentration value to various reference values.

13. The method as claimed in claim 11, wherein the step (c2) includes the step of comparing the calculated value of concentration change to various reference values.

14. The method as claimed in claim 11, wherein the first fan and the second fan rotate at one of speeds inclusive of a highest speed, a high speed, a medium speed, and a lowest speed, respectively.

15. The method as claimed in claim 14, wherein the (c3) step includes the step of rotating at least one of the first fan and the second fan at the highest speed when the concentration value is high, and the value of the concentration change is high or medium.

16. The method as claimed in claim 14, wherein the (c3) step includes the step of rotating at least one of the first fan and the second fan at the high speed when the concentration value is high, and the value of the concentration change is low.

17. The method as claimed in claim 14, wherein the (c3) step includes the step of rotating at least one of the first fan and the second fan at the high speed when the concentration value is medium, and the value of the concentration change is high.

18. The method as claimed in claim 14, wherein the (c3) step includes the step of rotating at least one of the first fan and the second fan at the medium speed when the concentration value is medium, and the value of the concentration change is medium or low.

19. The method as claimed in claim 14, wherein the (c3) step includes the step of rotating at least one of the first fan and the second fan at the medium speed when the concentration value is low, and the value of the concentration change is high.

20. The method as claimed in claim 14, wherein the (c3) step includes the step of rotating at least one of the first fan and the second fan at the lowest speed when the concentration value is low, and the value of the concentration change is medium or low.

Description:

This application claims the benefit of the Korean Application No. P2004-0004152 filed on Jan. 20, 2004, which is hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to air conditioning systems, and more particularly, to a method for controlling an air flow rate of an air conditioning system, in which a flow rate of room cleaning or ventilating air is controlled to cope, not only with concentration of organic compounds, but also with rapid change of the concentration of the organic compounds in the air.

2. Background of the Related Art

The air conditioning system is an apparatus for maintaining room air at a most proper state according to use or purpose of the air, inclusive of air conditioners, air cleaners, ventilating devices. The air conditioner cools or heats the room by using a property of the refrigerant in which the refrigerant discharges or absorbs heat to/from an environment when the refrigerant undergoes a phase changes.

The air cleaner draws air from the room, removes foreign matters, such as dusts, from the air, and supplies cleaned air to the room again, and the ventilating device discharges room air to an outside of the room and draws outdoor air into the room.

In the meantime, recently, above three kinds of devices are provided as one air conditioning system, rather than provided as independent devices. In general, such an air conditioning system cleans room air while cooling/heating the room so as to keep a room temperature within an appropriate temperature range. However, since the air of a shut tight room is polluted gradually as time goes by, the air conditioning system ventilates the room periodically, to supply fresh air to the room.

In above process, an air flow rate of the air supplied to the room after being cooled/heated and cleaned by the air conditioning system is in general controlled according to a room temperature, and an air flow rate of the air supplied to/discharged from the room in ventilation is controlled to be constant.

However, since the foregoing typical air conditioning system is operative only taking the room temperature into account without a level of air pollution of the room, the air conditioning system fails to reflect very important factors, such as the level of pollution of the room air, and a rate of pollution of the room air, to the operation.

Moreover, in a case the room air is polluted rapidly due to various reasons, such as someone in the room smokes, or many persons use the room suddenly, or the like, typical air conditioning system can not deal with the change of room air, appropriately.

SUMMARY OF THE INVENTION

Accordingly, the present invention is directed to a method for controlling an air flow rate of an air conditioning system that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.

An object of the present invention is to provide a method for controlling an air flow rate of an air conditioning system, which can deal with a level of room air pollution, and sharp change of the pollution level, appropriately.

Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.

To achieve these objects and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described herein, the method for controlling an air flow rate of an air conditioning system, includes the steps of (a) measuring a concentration of volatile organic compounds in air, periodically, (b) calculating a value of concentration change from concentration values measured at the present time and in the past, and (c) controlling the flow rate of air for cleaning or ventilating a room with reference to the present concentration and value of concentration change.

The value of concentration change in the step (b) is a difference of a concentration value measured at the present time and a concentration value measured right before. The flow rate of the air for cleaning or ventilating a room includes a highest flow rate, a high flow rate, a medium flow rate, and a lowest flow rate.

Preferably, the flow rate of the air for cleaning or ventilating a room is controlled to be the highest flow rate when the concentration value is high, and the value of concentration change is high or medium, and the high flow rate when the concentration value is high, and the value of concentration change is low, or the concentration value is medium, and the value of concentration change is high.

Preferably, the flow rate of the air for cleaning or ventilating a room is controlled to be the medium flow rate when the concentration value is medium, and the value of concentration change is medium or low, or the concentration value is low, and the value of concentration change is high, and the lowest flow rate when the concentration value is low, and the value of concentration change is medium of low.

In the meantime, the flow rate of the air for cleaning the room is controlled by controlling a rotation speed of a fan which draws air from the room and discharges the air to the room, again. The flow rate of the air for ventilating the room is controlled by controlling a rotation speed of a fan which draws outdoor air and discharges the outdoor air to the room, or a rotation speed of a fan which draws room air and discharges the room air to an outside of the room.

In the meantime, the step (c) includes the steps of (c1) determining a level of the concentration value measured at the present time, (c2) determining a level of the value of the concentration change calculated at the present time, and (c3) controlling a rotation speed of at least one of a first fan for supplying air to the room and a second fan for discharging air from the room with reference to the levels of the concentration value and the value of the concentration change.

The step (c1) includes the step of comparing the measured concentration value to various reference values, and the step (c2) includes the step of comparing the calculated value of concentration change to various reference values. The first fan and the second fan rotate at one of speeds inclusive of a highest speed, a high speed, a medium speed, and a lowest speed, respectively.

The (c3) step may include the step of rotating at least one of the first fan and the second fan at the highest speed when the concentration value is high, and the value of the concentration change is high or medium.

The (c3) step may include the step of rotating at least one of the first fan and the second fan at the high speed when the concentration value is high, and the value of the concentration change is low.

The (c3) step may include the step of rotating at least one of the first fan and the second fan at the high speed when the concentration value is medium, and the value of the concentration change is high.

The (c3) step may include the step of rotating at least one of the first fan and the second fan at the medium speed when the concentration value is medium, and the value of the concentration change is medium or low.

The (c3) step may include the step of rotating at least one of the first fan and the second fan at the medium speed when the concentration value is low, and the value of the concentration change is high.

The (c3) step includes the step of rotating at least one of the first fan and the second fan at the lowest speed when the concentration value is low, and the value of the concentration change is medium or low.

It is to be understood that both the foregoing description and the following detailed description of the present invention are exemplary and explanatory and are intended to provide further explanation of the invention claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the principle of the invention.

In the drawings;

FIG. 1 illustrates a diagram of an air conditioning system, schematically;

FIG. 2 illustrates a block diagram showing relation between a control part and units of the air conditioning system in FIG. 1, schematically;

FIG. 3 illustrates a flow chart showing the steps of a method for controlling a flow rate by the control part of the air conditioning system in FIG. 1 in accordance with a first preferred embodiment of the present invention; and

FIG. 4 illustrates a flow chart showing the steps of a method for controlling a flow rate by the control part of the air conditioning system in FIG. 1 in accordance with a second preferred embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. In describing the embodiments, identical parts will be given the same names and reference symbols, and repetitive description of which will be omitted. FIG. 1 illustrates a diagram of an air conditioning system, schematically.

Referring to FIG. 1, there is an indoor unit 10 installed on a ceiling of a room so as to be in communication with a room. The indoor unit 10 includes an expansion device (not shown) for expanding refrigerant, an indoor heat exchanger (not shown) for making the expanded refrigerant to heat exchange with the room air, and an indoor fan (not shown) for drawing the room air into the indoor unit 10, and supplying the room air to the room again via the indoor heat exchanger.

Though not shown, the indoor unit 10 has a filter assembly provided therein. The filter assembly 10 removes foreign matters from the room air drawn into the indoor unit 10. Accordingly, the room air 10, not only cools or heats the room, but also serves as an air cleaner for cleaning the room air.

Moreover, referring to FIG. 1, there is an outdoor unit 20 on an outdoor. The outdoor unit 20 includes a compressor (not shown) for compressing refrigerant, an outdoor heat exchanger (not shown) for making the compressed refrigerant to heat exchange with outdoor air to condense the refrigerant, and an outdoor fan 21 for blowing outdoor air to the outdoor heat exchanger.

When the outdoor unit 20 and the indoor unit 10 are put into operation, the room air is drawn into the indoor unit, heat exchange at the indoor heat exchanger, and supplied to the room again. According to this, the room is cooled or heated. Along with this, since the air drawn into the indoor unit 10 is cleaned by the filter assembly (not shown), the room air is cleaned.

In the meantime, there are a plurality of air discharge ports 51 and air supply ports 41 on the ceiling at places distanced away from the indoor unit 10. The air discharge port 51 has an air discharge duct 50 connected thereto, and the air supply port 41 has the air supply duct 40 connected thereto. Each of the air supply ducts 40, and the air discharge ducts 50 has one end in communication with an outdoor.

There is a pre-heat exchanger 60 at a middle of the air supply duct 40 and the air discharge duct 50 for making the room air and the outdoor air to cross and heat exchange indirectly. The pre-heat exchanger 60 has at least one flow passage 61 in communication with the air supply duct 40 for flow of outdoor air, and at least one second flow passage 62 in communication with the air discharge duct 50 for flow of the room air. The first flow passage 61 and the second flow passage 62 are arranged to be in contact, or cross with each other. Therefore, the outdoor air and the room air heat exchange indirectly without mixed with each other when the outdoor air and the room air pass the pre-heat exchanger 60.

In the air conditioning system in FIG. 1, the air supply duct 40 and the air discharge duct 50 have an air supply fan 45 for supplying outdoor air to the room, and an air discharge fan 55 for discharging room air to an outside of the room, respectively. As shown in FIGS. 1 and 2, turn on/off and rotation speeds of the air supply fan 45 and the air discharge fan 55 are controlled by the control part 30.

Upon putting the air discharge fan 55 and the air supply fan 45 into operation, the outdoor air is introduced into the room through the air supply duct 40 and the air supply port 41, and the room air is discharged to an outside of the room through the air discharge duct 50 and the air discharge port 51. In this instance, because the outdoor air is introduced into the room after having a portion of thermal energy of the room air discharged to outside of the room transferred thereto, a heat loss caused at the time of ventilation is reduced.

In the meantime, polluted stagnant room air contains much volatile organic compounds, and give harmful influences to persons living in the room, such as diseases of the respiratory organs, allergic skin diseases, headache, and the like. For prevention of this, it is required to measure a pollution level of the room air, and control an air flow rate of the cleaning or ventilating air based on the data.

For this, the air conditioning system of the present invention includes a VOC sensor 15. As shown in FIGS. 1 and 2, the VOC sensor 15 is connected to the control part 30 electrically. Therefore, the VOC sensor 15 measures a content of the volatile organic compounds in the room air, and transmits the information to the control part 30.

Then, the control part 30 controls the indoor unit 10, the air supply fan 45, the air discharge fan 55 respectively based on the information from the VOC sensor 15, for controlling a flow rate of the cleaning, or ventilating air, i.e., supplied to/discharged from the room. A method for controlling a flow rate in accordance with a first preferred embodiment of the present invention will be described with reference to FIG. 3.

The control part 30 controls the air flow rate of the cleaning or ventilating air when the air conditioning system is set to be operative automatically. When the air conditioning system starts automatic operation, the VOC sensor 15 is stabilized for proper performance of the function. The stabilization of the VOC sensor 15 requires a certain time period, for an example, three minutes. Therefore, the control part 30 determines pass of a time period required for stabilization of the VOC sensor 30. (S1 step)

As a result of the determination, if the time period required for stabilization of the VOC sensor 15 is not passed yet, the control part 30 keeps checking pass of the time period. However, as a result of the determination, if the time period is passed, the control part 30 reads a value measured at the VOC sensor 15. (S2 step).

In the meantime, in general the VOC sensor 15 outputs a voltage proportional to a measured content of the volatile organic compounds. Therefore, the control part 30 determines a content of the volatile organic compounds in the room air with reference to the voltage from the VOC sensor 15. In this instance, for determination that how much volatile organic compound is contained in the room air, the control part 30 uses a few reference values, i.e., reference voltages, as follows.

At first, the control part 30 determines if the voltage from the VOC sensor 15 is higher than a first reference voltage, for an example, 3V. (S3 step)

As a result of this, if the voltage is higher than 3V, the control part 30 determines that the air contains much volatile organic compounds. According to this, the control part 30 controls the indoor unit 10, the air supply fan 45, or the air discharge fan 55, to maximize the flow rate of air supplied to or discharged from the room for cleaning or ventilating the room. (S4 step).

In this instance, when the control part 30 controls the indoor fan (not shown) of the indoor unit 10 to rotate at a maximum speed, the flow rate of air supplied to the room again after cleaned at the indoor unit 10 becomes the maximum. If the control part 30 controls the air supply fan 45 to rotate at a maximum speed, the flow rate of the fresh air supplied to the room becomes the maximum, if the control part 30 controls the air discharge fan 55 to rotate at the maximum speed, the flow rate of the air discharged to an outside of the room becomes the maximum. In a case the control part 30 controls the air supply fan 45 or the air discharge fan 55, it is preferable that the control part 30 controls both the air supply fan 45 and the air discharge fan 55 at the same time for effective ventilation.

In the meantime, if the voltage from the VOC sensor 15 is lower than 3V, the control part 30 determines if the voltage is higher than a second reference voltage, for an example, 2V. (S5 step).

As a result of the determination, if the voltage is higher than 2V, the control part 30 determines that the air has an ordinary content of the volatile organic compounds. According to this, the control part 30 controls the indoor unit 10, the air supply fan 45, or the air discharge fan 55, to set the flow rate of air supplied to or discharged from the room for cleaning or ventilating the room to medium. (S6 step).

Opposite to this, if the voltage is lower than 2V, the control part 30 determines that the air has a low content of the volatile organic compounds. According to this, the control part 30 controls the indoor unit 10, the air supply fan 45, or the air discharge fan 55, to minimize the flow rate of air supplied to or discharged from the room for cleaning or ventilating the room. (S7 step).

For reference, the flow rate of the air supplied to or discharged from the room for cleaning, or ventilating the room according to the measured value by the VOC sensor 15 is as shown in the following table 1.

TABLE 1
A method for controlling an air flow rate in accordance with
a first preferred embodiment of the present invention.
Measured VOC concentrationAir flow rate
Higher than 3.0 VMaximum
Below 3.0 V higher than 2.0 VMedium
Below 2.0 VMinimum

In the meantime, the control part 30 repeats a process of reading a measured value of the VOC sensor 15, and controlling the flow rate for cleaning or ventilating the room with reference to the measured value periodically during the air conditioning system is operated automatically. For this, upon finishing above process, the control part 30 determines the air conditioning system of being operated in an automatic operation mode. (S8 step).

As a result of the determination, if the air conditioning system is not in the automatic operation mode, i.e., operated manually, or stationary, the control part 30 terminates control of the flow rate required for cleaning or ventilating the room.

Opposite to this, as a result of the determination, if the air conditioning system is in the automatic operation mode, the control part 30 determines pass of the preset time period after reading the measured value from the VOC sensor 15. (S9 step)

If the preset time period is passed, the control part 30 reads the measured value from the VOC sensor 15 again, and performs above steps starting from the S2 step again. However, if the preset time period is not passed, the control part 30 repeats the S8 step and the S9 step until the preset time period passes.

Thus, the air conditioning system automatically controls the flow rate of the air supplied to or discharged from the room, i.e., flow rate of the cleaning, or ventilating air according to the content of the volatile organic compounds in the room air. Accordingly, the first embodiment of the present invention, the air conditioning system, not only controls the room air temperature, but also cleans or ventilates the room with reference to a level of pollution of the room air, to make the room more comfortable.

However, even if the flow rate of the cleaning, or ventilating air is controlled according to the content of the volatile organic compounds in the room air, the air conditioning system has a limitation in that rapid pollution of the room air can not be dealt with, effectively. That is, the air conditioning system has a limitation in that it is difficult to sense and deal with the rapid pollution of the room air caused by smoking or sudden increase of persons in the room.

Therefore, the present invention suggests an improved method for controlling an air flow rate in accordance with a second preferred embodiment of the present invention, that can overcomes the limitation. In the second embodiment that overcomes the limitation of the first embodiment, for controlling the air flow rate of the air conditioning system, not only an absolute concentration of the volatile organic compound contained in the room air, but also change of the concentration of the volatile organic compound per unit time period are taken into account.

Therefore, according to the method for controlling an air flow rate in accordance with a second preferred embodiment of the present invention, the control part 30 can determine rapid pollution or depollution of the present room air through the change of concentration, to enable to deal with the rapid pollution of the room air effectively. A method for controlling an air flow rate in accordance with a second preferred embodiment of the present invention will be described in detail, with reference to FIG. 4.

At first, when automatic operation is started, the VOC sensor 15 is stabilized. Of course, the VOC sensor 15 may perform the stabilization as soon as the air conditioning system is put into operation. Then, pass of a time period required for stabilization of the VOC 15 is determined. (S 10 step).

As a result, if the time period required for stabilization is passed, the VOC sensor 15 measures concentration of a content of the volatile organic compounds in the air, periodically. Then, a value dV of concentration change is calculated from concentration values measured at the present time and in the past. (S20) Since the concentration of the volatile organic compounds is measured periodically, the value dV of concentration change is defined as a difference of the concentration value measured presently, and the concentration value measured right before.

Thus, once the concentration of the volatile organic compounds in the air is measured, and the value of concentration change dV is calculated, the control part 30 controls at least one of the measured concentration value, and flow rate of the air supplied to or discharged from the room for cleaning, or ventilating the room with reference to the value dV of the concentration change.

For this, the control part 30 controls rotation speeds of the fan (a first fan) for supplying air to the room, and the fan (a second fan) for discharging air from the room. The first fan can be defined as at least one of the indoor fan (not shown) provided to the indoor unit 10 and the air supply fan 45 provided to the air supply duct 40.

If the first fan is defined as the indoor fan, the control part 30 controls the flow rate of the air drawn into the indoor unit 10, cleaned at the filter assembly, and supplied to the room again in air cleaning. Opposite to this, if the first fan is defined as the air supply fan 45, the control part 30 controls the flow rate of the outdoor air supplied to the room through the air supply duct 40 in ventilation.

In the meantime, though the air conditioning system can perform the step of cleaning or ventilating the room independently, the air conditioning system can perform the steps of cleaning and ventilating the room at the same time. Accordingly, it may be defined that the first fan means both the indoor fan and the air supply fan 45.

In this case, the control part 30 cleans the room air as well as ventilates the room air, during which steps the control part 30 controls rotation speeds of the indoor fan and the air supply fan 45 at the same time with reference to the concentration of the volatile organic compounds and the value dV of concentration change.

Next, the second fan can be defined as the air discharge fan 55 on the air discharge duct 50. According to this, by controlling the rotation speed of the air discharge fan 55 with reference to the concentration and the value dV of concentration change, the control part 30 can control the flow rate of the air discharged to an outside of the room through the air discharge duct 50 in ventilation.

In the meantime, the control part 30 controls the flow rate of the air supplied to or discharged from the room for cleaning or ventilating the room as shown in [Table] with reference to the measured concentration and the value dV of concentration change. For reference, the flow rate for cleaning or ventilating the room includes a highest flow rate, a high flow rate, a medium flow rate, and a lowest flow rate.

TABLE 2
A method for controlling an air flow rate according to an
improved embodiment of the present invention.
Concentration value V of VOC
High
(higherMediumLow
than(over 2.0 V(below
3.0 V)below 3.0 V)2.0 V)
Value dV ofHighHighestHigh flowMedium
concentration(higher than +0.1)flow raterateflow rate
change of VOCMediumHighestMediumLowest
(over −0.1flow rateflow rateflow rate
below +0.1)
LowHigh flowMediumLowest
(below −0.1)rateflow rateflow rate

Referring to [Table 2], if the concentration value of the volatile organic compounds is high, and the value of the concentration change is high or medium, the control part 30 determines that room is, not also polluted much presently, but also rapidly being polluted presently. According to this, the control part 30 controls such that the flow rate for cleaning or ventilating the room is set to the highest flow rate.

If the concentration value of the volatile organic compounds is high, and the value of the concentration change is low, the control part 30 determines that room is not being rapidly polluted presently, even though polluted much presently. If the concentration value of the volatile organic compounds is medium, and the value of the concentration change is high, the control part 30 determines that room is being rapidly polluted presently, even though polluted not so much presently. Accordingly, in above two cases, the control part 30 controls such that the flow rate for cleaning or ventilating the room is set to a high flow rate.

If the concentration value of the volatile organic compounds is medium, and the value of the concentration change is medium or low, or the concentration value of the volatile organic compounds is low, and the value of the concentration change is high, the control part 30 determines that room is polluted slightly presently, and a pollution rate is increasing gradually presently. Accordingly, in those cases, the control part 30 controls such that the flow rate for cleaning or ventilating the room is set to a medium flow rate.

Lastly, if the concentration value of the volatile organic compounds is low, and the value of the concentration change is medium or low, the control part 30 determines that room is clean presently, and not rapidly being polluted presently. According to this, the control part 30 controls such that the flow rate for cleaning or ventilating the room is set to the lowest flow rate.

In the meantime, referring to [Table 2], for controlling the air flow rate according to the concentration value of the volatile organic compounds, and the value of the concentration change, the control part 30 determines a level of the concentration value of the volatile organic compounds measured at the VOC sensor 15 and a level of the value of the concentration change calculated presently.

The level of the concentration value is determined by comparing the concentration value measured at the VOC sensor 15 to various reference values set in advance. The value of the concentration change is also determined by comparing the value of concentration change calculated presently to various reference values set in advance.

Once the concentration value and the value of concentration change are determined by above method, the control part 30 controls at least one of rotation speed of the first fan for supplying air to the room and the second fan for discharging air from the room, to control the flow rate of the air for the cleaning or ventilating the room. In this instance, each of the first fan and the second fan is rotated in one of various speeds inclusive of the highest speed, high speed, medium speed, and lowest speed.

When the first or second fan is rotated at the highest speed, the flow rate for cleaning or ventilating the room becomes the highest flow rate, and when the first or second fan is rotated at the high speed, the flow rate for cleaning or ventilating the room becomes the high flow rate. When the first or second fan is rotated at the medium speed, the flow rate for cleaning or ventilating the room becomes the highest flow rate, and when the first or second fan is rotated at the lowest speed, the flow rate for cleaning or ventilating the room becomes the lowest flow rate.

The flow chart in FIG. 4 shows the steps of a process for determining levels of the concentration value and the value of concentration change of the volatile organic compounds, and determining an air flow rate according to a result of the level determination, well. The air flow rate process will be described in more detail with reference to FIG. 4.

At first, the control part 30 determines if the present concentration value is higher than a first reference value, for an example, 3V, for determining a level of the concentration value of the volatile organic compounds. (S30). As a result of this, if the present concentration value is higher than the first reference value, the control part 30 determines that the present concentration value is high.

Once the level of the present concentration value is determined to be high in the step S30, the control part 30 determines a level of a value of concentration change at the present time. For this, the control part 30 determines if the calculated present value dV of the concentration change is higher than a third reference value, for an example, +0.1. (S31) As a result, if the present value dV of the concentration change is higher than the third reference value, the control part 30 determines that the level of the present value of the concentration change is high.

However, as a result of determination in the step S31, if the present value dV of the concentration change is not higher than the third reference value, the control part 30 determines if the present value dV of the concentration change is higher than a fourth reference value, for an example, −0.1V. (S32) As a result, if the present value dV of the concentration change is higher than the fourth reference value, the control part 30 determines that the present value dV of the concentration change is medium.

In the meantime, referring to [Table 2], if the present concentration value is high, and the present value dV of concentration change is high or medium, the control part 30 determines the flow rate of the air for cleaning or ventilating the room to be the highest flow rate. In this case, the control part 30 rotates at least one of the first fan and the second fan at the highest speed. (S71)

If the present value dV of concentration change is determined to be lower than the fourth reference value in the step S32, the control part 30 determines the value of the concentration change is low even if the present concentration value is high. According to this, as shown in FIG. 4 and [Table 2], the control part 30 rotates at least one of the first fan and the second fan at a high speed for having the high flow rate.

If the present concentration value is lower than the first reference value in the step S30, the control part 30 determines if the present concentration value is higher than the second reference value for determining the level of the present concentration value. (S40) As a result of this, if the present concentration value is higher than the second reference value, the control part 30 determines the present concentration value of being medium.

Then, the control part 30 determines if the present value of concentration change is higher than the third reference value, i.e., +0.1, for determining a level of the present value of concentration change. (S50). As a result of this, if the present value of concentration change is higher than the third reference value, the control part 30 determines that the present value of the concentration change is high while the present concentration value is medium.

Accordingly, in this case, as shown in FIG. 4 and [Table 2], the control part 30 rotates at least one of the first fan and the second fan to have the high flow rate. (S72).

In the meantime, if it is determined that the present value of concentration change is lower than the third reference value in the step S50, the control part 30 determines if the present value of the concentration change is higher than the fourth reference value, i.e., −0.1 for determining a level of the present value of the concentration change. (S60)

As a result of this, if the present value of concentration change is higher than the fourth reference value, the control part 30 determines that the present concentration value is medium, and the present value of concentration change is medium. Opposite to this, as a result of the determination, if the present value of concentration change is lower than the fourth reference value, the control part 30 determines that the present concentration value is medium, and the present value of concentration change is low.

According to this, in this case, as shown in [Table 2] and FIG. 4, the control part 30 rotates at least one of the first fan and the second fan at a medium speed to output a medium flow rate. (S73)

In the meantime, if it is determined that the present concentration value is lower than the second reference value as a result of determination in the step S40, the control part 30 determines that the present concentration value is low. Then, for determining the level of the present value of concentration change, the control part 30 determines if the present value of concentration change is higher than the third reference value, i.e., +0.1. (S41)

As a result of this, if the present value of concentration change is higher than the third reference value, the control part 30 determines that the present value of concentration change is high while the present concentration value is low. According to this, as shown in [Table 2] and FIG. 4, the control part 30 rotates at least one of the first fan and the second fan at a medium speed to output a medium flow rate. (S73).

Opposite to this, if it is determined that the present value of concentration change is lower than the third reference value, for determining a level of the present value of the concentration change, the control part 30 determines if the present value of concentration change is higher than the fourth reference value, i.e., −0.1. (S42)

As a result of this, if the present value of concentration change is higher than the fourth reference value, the control part 30 determines that the present value of concentration change is medium while the present concentration value is low. Opposite to this, if the present value of concentration change is lower than the fourth reference value, the control part 30 determines that the present value of concentration change is low while the present concentration value is low.

Accordingly, in this case, as shown in [Table 2] and FIG. 4, the control part 30 rotates at least one of the first fan and the second fan at the lowest speed to output a lowest flow rate. (S74)

In the meantime, the control part 30 repeats a process of reading a measured value at the VOC sensor 15, and controlling the flow rate for cleaning, or ventilating the room with reference to the measured value during the air conditioning system is operated automatically. For this, upon finishing above process, the control part 30 determines if the air conditioning system is operated in the automatic operation mode. (S80)

As a result of the determination, if the air conditioning system is not operated in the automatic operation mode, i.e., operated manually, or stationary, the control part 30 terminates the flow rate control required for cleaning, or ventilating the room.

Opposite to this, as a result of the determination, if the air conditioning system is operated in the automatic operation mode, the control part 30 determines if a preset time period is passed after reading the measured value at the VOC sensor 15. (S90)

If the preset time period is passed, the control part 30 reads the measured value at the VOC sensor 15 again, and performs above steps starting from the step S20. However, if the preset time period is not passed, the control part 30 repeats the step S80 and the step S90 until the present time period is passed.

As has been described, the method for controlling an air flow rate of an air conditioning system of the present invention has the following advantages.

Not only absolute concentration, but also a value of concentration change of volatile organic compounds are taken into account in controlling the flow rate to the air required for cleaning, or ventilating the room. Therefore, in cleaning, or ventilating room air, not only a level of pollution of room air, but also rapid room air pollution is made to deal with.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.