CN103673223A - Air supply quality early warning based fresh air system and intelligent control method thereof - Google Patents

Abstract

The invention provides a fresh air system and an intelligent control method based on early warning of the air quality of the air supply, including a carbon dioxide concentration sensor, a non-personnel-generated pollutant concentration sensor group, an electric regulating valve, and an intelligent controller. The present invention uses various sensors to detect the air supply and indoor pollutant concentration levels, compares and determines the advantages and disadvantages of the two, and determines the air quality level of outdoor fresh air, thereby controlling the opening and closing status of fresh air valves through a certain control program to achieve the purpose of early warning. It can be widely used in the centralized ventilation and air-conditioning systems of various large public buildings, avoiding the phenomenon of poor indoor air quality due to poor outdoor fresh air quality, but constantly introducing a large amount of fresh air into the building. Through reasonable fresh air volume control, creating A healthier and safer indoor building environment.

Description

A fresh air system and intelligent control method based on supply air quality early warning

technical field

The invention belongs to the field of building ventilation and air conditioning, and in particular relates to an air supply early warning technology in a centralized ventilation and air conditioning system.

Background technique

With the development of economy and society and the widespread use of air conditioners, people pay more and more attention to indoor air quality, but the actual air pollution inside buildings is becoming more and more serious. The severe outdoor air pollution is an important reason for this phenomenon. Although the introduction of fresh air aims to replace indoor polluted air with relatively clean outdoor air, provide the oxygen supply needed for breathing by the people in the room, dilute indoor pollutants, and ensure the comfort and health of the people in the room. However, when fresh air is introduced, a certain amount of pollutants will also be introduced into the room. Therefore, when the concentration of one or more pollutants outside exceeds the standard, increasing the fresh air volume will aggravate the indoor air pollution and cause serious indoor environmental pollution. Therefore, under the above circumstances, it is necessary to judge the quality of outdoor fresh air in time and formulate a reasonable fresh air control strategy.

The disadvantage of the existing fresh air device is that when the concentration of outdoor pollutants exceeds its indoor concentration, the system will instead make a wrong judgment of increasing the fresh air supply when the fresh air supply should be reduced, resulting in a continuous increase in the concentration of indoor pollutants and causing indoor pollution. exacerbated.

Contents of the invention

One of the objectives of the present invention is to provide a fresh air system that simultaneously monitors indoor and outdoor air quality.

The technical solution adopted to achieve the purpose of the present invention is as follows, a fresh air system based on the early warning of the air quality of the supply air, which is characterized in that it includes an air conditioning unit installed outside the room, and a total return air duct, a total air supply duct, Exhaust pipe and unit air intake pipe;

The air inlet of the main air supply pipe is connected to the air-conditioning unit; the air outlet of the main air supply pipe communicates with the room through an air supply branch pipe. The air inlet of the fresh air pipe is outside the room, and the air outlet is connected with the air conditioning unit. The air inlet of the total air return pipe communicates with the room through the return air branch pipe. The air outlet of the total air return pipe is connected with the air inlet of the exhaust pipe and the air inlet of the unit air inlet pipe. The air outlet of the exhaust pipe is outside the room. The air outlet of the air inlet pipe of the unit is connected with the air conditioning unit.

A formaldehyde concentration sensor I, a nitrogen monoxide concentration sensor I, a sulfur dioxide concentration sensor I, a TVOC concentration sensor I and a carbon dioxide concentration sensor are installed in the total return air pipe section. Formaldehyde concentration sensor II, nitric oxide concentration sensor II, sulfur dioxide concentration sensor II and TVOC concentration sensor II are installed in the main air supply pipe. An electric valve is installed in the fresh air pipe.

Due to the above-mentioned structure, the present invention can obtain the quality of the indoor and outdoor air quality of the building through comparison, reasonably make early warning judgments and reasonably adjust the fresh air volume introduced into the building, so as to create a healthier and safer indoor environment.

Another object of the present invention is to provide an intelligent early warning fresh air control method based on the above system.

The technical scheme adopted for realizing the purpose of the present invention is such, comprises the following steps:

1) Start the air conditioning unit. The electric valve is adjusted to the initial opening corresponding to the designed minimum fresh air volume.

2) Set the concentration upper limit of each pollutant, namely formaldehyde: S ₁ =0.1mg/m ³ ; nitrogen dioxide: S ₂ =0.24mg/m ³ ; sulfur dioxide: S ₃ =0.50mg/m ³ ; TVOC : S ₄ =0.6 mg/m ³ .

3) The formaldehyde concentration measured by the formaldehyde concentration sensor I is C11, the nitric oxide concentration measured by the nitric oxide concentration sensor I is C12, the sulfur dioxide concentration measured by the sulfur dioxide concentration sensor I is C13, and the TVOC concentration measured by the TVOC concentration sensor I is C13. C14. calculate:

${\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; =</span>\sqrt{\mathrm{<span\; class="notranslate">\; max</span>}<span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; C</span>}\mathrm{<span\; class="notranslate">\; 11</span>}}{\mathrm{<span\; class="notranslate">\; S</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; ,</span>\frac{\mathrm{<span\; class="notranslate">\; C</span>}\mathrm{<span\; class="notranslate">\; 12</span>}}{\mathrm{<span\; class="notranslate">\; S</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; ,</span>\frac{\mathrm{<span\; class="notranslate">\; C</span>}\mathrm{<span\; class="notranslate">\; 13</span>}}{\mathrm{<span\; class="notranslate">\; S</span>}\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; ,</span>\frac{\mathrm{<span\; class="notranslate">\; C</span>}\mathrm{<span\; class="notranslate">\; 14</span>}}{\mathrm{<span\; class="notranslate">\; S</span>}\mathrm{<span\; class="notranslate">\; 4</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 4</span>}}\underset{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{\mathrm{<span\; class="notranslate">\; 4</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}\frac{\mathrm{<span\; class="notranslate">\; C</span>}\mathrm{<span\; class="notranslate">\; 1</span>}\mathrm{<span\; class="notranslate">\; i</span>}}{\mathrm{<span\; class="notranslate">\; Si</span>}}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; .</span>$

The formaldehyde concentration measured by the formaldehyde concentration sensor II is C21, the nitric oxide concentration measured by the nitric oxide concentration sensor II1 is C22, the sulfur dioxide concentration measured by the sulfur dioxide concentration sensor II1 is C23, and the TVOC concentration measured by the TVOC concentration sensor II1 is C24. calculate:

${\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; =</span>\sqrt{\mathrm{<span\; class="notranslate">\; max</span>}<span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; C</span>}\mathrm{<span\; class="notranslate">\; twenty\; one</span>}}{\mathrm{<span\; class="notranslate">\; S</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; ,</span>\frac{\mathrm{<span\; class="notranslate">\; C</span>}\mathrm{<span\; class="notranslate">\; twenty\; two</span>}}{\mathrm{<span\; class="notranslate">\; S</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; ,</span>\frac{\mathrm{<span\; class="notranslate">\; C</span>}\mathrm{<span\; class="notranslate">\; twenty\; three</span>}}{\mathrm{<span\; class="notranslate">\; S</span>}\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; ,</span>\frac{\mathrm{<span\; class="notranslate">\; C</span>}\mathrm{<span\; class="notranslate">\; twenty\; four</span>}}{\mathrm{<span\; class="notranslate">\; S</span>}\mathrm{<span\; class="notranslate">\; 4</span>}}<span\; class="notranslate">\; ,</span><span\; class="notranslate">\; )</span><span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 4</span>}}\underset{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{\mathrm{<span\; class="notranslate">\; 4</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}\frac{\mathrm{<span\; class="notranslate">\; C</span>}\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; i</span>}}{\mathrm{<span\; class="notranslate">\; Si</span>}}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; .</span>$

4) Compare the size of I ₁ and I ₂ : if I ₁ is greater than I ₂ , go to step 5). If I ₁ is less than I ₂ , close the electric valve and skip to step 7).

5) The carbon dioxide concentration sensor starts to work, measures the carbon dioxide concentration, and operates in three situations:

i When the carbon dioxide concentration is greater than 1000ppm, the opening of the electric valve is increased by 5%;

ii When the carbon dioxide concentration is less than 700ppm, the opening of the electric valve is reduced by 5%;

iii When the carbon dioxide concentration is 700-1000ppm, the opening of the electric valve remains unchanged.

After performing the actions of step i, ii or iii, wait for an interval of time Δt, and then enter the next step.

6) After repeating step 5) n times, jump to step 3).

7) The carbon dioxide concentration sensor starts to work, measures the carbon dioxide concentration, and operates in two situations:

i If the carbon dioxide concentration is greater than 1000ppm, open the electric valve and adjust to the initial opening corresponding to the minimum fresh air volume in the design;

ii If the carbon dioxide concentration is less than 1000ppm, the electric valve is closed.

After performing the actions of step i or ii, wait for an interval of time Δt, and then enter the next step.

8) Measure the concentration of carbon dioxide and perform actions in two situations:

i When the carbon dioxide concentration is greater than 1000ppm, the opening of the electric valve is increased by 5%;

ii If the carbon dioxide concentration is less than 1000ppm, the electric valve will continue to be closed. Interval time Δt.

After performing the actions of step i or ii, wait for an interval of time Δt, and then enter the next step.

9) After repeating step 8) m times, jump back to step 3).

Based on the above-mentioned intelligent control method, the present invention has the following characteristics:

1. Comprehensive consideration of indoor and outdoor air quality

This device realizes the comprehensive consideration of indoor and outdoor air quality, and judges the system operation and working mode according to the air quality comparison of fresh air and return air. Rather than simply judging the indoor or outdoor environmental quality for control, the control decision-making is more comprehensive and appropriate.

2. Create a healthier and safer indoor environment

This control device judges the quality of the fresh air introduced from the outside. By measuring the concentration of four kinds of air pollutants, it can achieve timely early warning and prevent the system from malfunctioning when the outdoor air quality is poor and increase the introduction of fresh air. Creating a healthy and safe building indoor environment provides a more reliable guarantee.

Description of drawings

Fig. 1 is a structural schematic diagram of the present invention.

Fig. 2 is a schematic structural diagram of multiple rooms in one embodiment.

In the figure: 1-formaldehyde concentration sensor Ⅰ, 2-nitrogen oxide concentration sensor Ⅰ, 3-sulfur dioxide concentration sensor Ⅰ, 4-TVOC concentration sensor Ⅰ, 5-carbon dioxide concentration sensor, 6-formaldehyde concentration sensor Ⅱ, 7-nitrogen oxide concentration Sensor Ⅱ, 8-sulfur dioxide concentration sensor Ⅱ, 9-TVOC concentration sensor Ⅱ, 10-controller, 11-air conditioning unit, 12-general return air pipe, 13-general air supply pipe, 14-fresh air pipe, 15-row Air duct, 16-unit air intake pipe, 17-room, 18-control room, 19-electric valve.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings and embodiments, but it should not be understood that the scope of the subject matter of the present invention is limited to the following embodiments. Without departing from the above-mentioned technical ideas of the present invention, various replacements and changes made according to common technical knowledge and customary means in this field shall be included in the protection scope of the present invention.

Example 1:

A fresh air system based on supply air quality early warning, including an air conditioning unit 11 installed outside a room 17, a main return air duct 12, a main air supply duct 13, an exhaust duct 15, and a unit air intake duct 16.

The air inlet of the main air supply pipe 13 is connected with the air conditioning unit 11 . The air outlet of the total air supply pipe 13 communicates with the room 17 through the air supply branch pipe: referring to Fig. 1, when there is only one room, the air outlet of the total air supply pipe 13 is in the room. Referring to Fig. 2, when there are multiple rooms, each room sends air into the room through an air supply branch pipe. The air inlet of the fresh air duct 14 is outside the room 17 , and the air outlet is connected to the air conditioning unit 11 . The air inlet of the total air return duct 12 communicates with the room 17 through the return air branch pipe: referring to Fig. 1, when there is only one room, the air inlet of the total air return duct 12 is in the room. Referring to Fig. 2, when there are multiple rooms, each room exhausts the indoor air through the return air branch pipe. The air outlet of the total air return pipe 12 is connected with the air inlet of the exhaust pipe 15 and the air inlet of the unit air inlet pipe 16 . The air outlet of the exhaust pipe 15 is outside the room 17 . The air outlet of the unit air inlet pipe 16 is connected with the air conditioning unit 11 .

A formaldehyde concentration sensor I1, a nitrogen monoxide concentration sensor I2, a sulfur dioxide concentration sensor I3, a TVOC concentration sensor I4 and a carbon dioxide concentration sensor 5 are installed in the total return air pipe section 12. Formaldehyde concentration sensor II6, nitric oxide concentration sensor II7, sulfur dioxide concentration sensor II8 and TVOC concentration sensor II9 are installed in the main air supply pipe 13. An electric valve 19 is installed in the fresh air pipe 14 .

Further, the formaldehyde concentration sensor I1, nitric oxide concentration sensor I2, sulfur dioxide concentration sensor I3, TVOC concentration sensor I4, carbon dioxide concentration sensor 5, formaldehyde concentration sensor II6, nitric oxide concentration sensor II7, sulfur dioxide concentration sensor II8 and TVOC concentration The measured value of the sensor II 9 is transmitted to the display device installed in the control room 18 through the data line. Further, it also includes a controller 10, the carbon dioxide concentration value measured by the carbon dioxide concentration sensor 5 is transmitted to the controller 10, and the electric valve 19 acts correspondingly according to the comparison result of the measured carbon dioxide concentration and the limit value.

Example 2:

This embodiment is based on the intelligent control method of the fresh air system based on the air supply air quality warning described in Embodiment 1, which is characterized in that it includes the following steps:

1) Start the air conditioning unit 11. The electric valve 19 is adjusted to the initial opening degree corresponding to the designed minimum fresh air volume, and in the embodiment, the initial opening degree is 10%-20%.

2) Set the concentration upper limit of each pollutant, namely formaldehyde: S ₁ =0.1 mg/m ³ . Nitrogen dioxide: S ₂ =0.24 mg/m ³ . Sulfur dioxide: S ₃ =0.50 mg/m ³ . TVOC: S ₄ =0.6 mg/m ³ .

3) The formaldehyde concentration measured by the formaldehyde concentration sensor I1 is C11, the nitric oxide concentration measured by the nitric oxide concentration sensor I2 is C12, the sulfur dioxide concentration measured by the sulfur dioxide concentration sensor I3 is C13, and the TVOC concentration measured by the TVOC concentration sensor I4 is C14. calculate: $I_1=\sqrt{\max (\frac{C11}{S1},\frac{C12}{S2},\frac{C13}{S3},\frac{C14}{S4})\left(\frac{1}{4}\underset{i=1}{\overset{4}{\mathrm{\&Sigma;}}}\frac{C1i}{\mathrm{Si}}\right)};$

The formaldehyde concentration sensor Ⅱ6 measures the formaldehyde concentration as C21, the nitric oxide concentration sensor Ⅱ7 measures the nitric oxide concentration as C22, the sulfur dioxide concentration sensor Ⅱ8 measures the sulfur dioxide concentration as C23, and the TVOC concentration sensor Ⅱ9 measures the TVOC concentration as C24. calculate:

${\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; =</span>\sqrt{\mathrm{<span\; class="notranslate">\; max</span>}<span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; C</span>}\mathrm{<span\; class="notranslate">\; twenty\; one</span>}}{\mathrm{<span\; class="notranslate">\; S</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; ,</span>\frac{\mathrm{<span\; class="notranslate">\; C</span>}\mathrm{<span\; class="notranslate">\; twenty\; two</span>}}{\mathrm{<span\; class="notranslate">\; S</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; ,</span>\frac{\mathrm{<span\; class="notranslate">\; C</span>}\mathrm{<span\; class="notranslate">\; twenty\; three</span>}}{\mathrm{<span\; class="notranslate">\; S</span>}\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; ,</span>\frac{\mathrm{<span\; class="notranslate">\; C</span>}\mathrm{<span\; class="notranslate">\; twenty\; four</span>}}{\mathrm{<span\; class="notranslate">\; S</span>}\mathrm{<span\; class="notranslate">\; 4</span>}}<span\; class="notranslate">\; ,</span><span\; class="notranslate">\; )</span><span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 4</span>}}\underset{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{\mathrm{<span\; class="notranslate">\; 4</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}\frac{\mathrm{<span\; class="notranslate">\; C</span>}\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; i</span>}}{\mathrm{<span\; class="notranslate">\; Si</span>}}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; ;</span>$

4) Compare the size of I ₁ and I ₂ : if I ₁ is greater than I ₂ , go to step 5). If I ₁ is smaller than I ₂ , close the electric valve 19 and skip to step 7).

5) The carbon dioxide concentration sensor 5 starts working to measure the carbon dioxide concentration: when the carbon dioxide concentration is greater than 1000ppm, the opening of the electric valve 19 is increased by 5%. When the carbon dioxide concentration was less than 700ppm, the opening of the electric valve 19 was adjusted down by 5%. When the carbon dioxide concentration is 700-1000ppm, the opening of the electric valve 19 remains unchanged. Interval time Δt. In an embodiment, Δt=10 minutes.

6) After repeating step 5n times, jump to step 3). In an embodiment, n=6.

7) The carbon dioxide concentration sensor 5 starts working to measure the carbon dioxide concentration: if the carbon dioxide concentration is greater than 1000ppm, open the electric valve 19 and adjust to the initial opening corresponding to the minimum fresh air volume designed. If the carbon dioxide concentration is less than 1000ppm, the electric valve 19 is closed. Interval time Δt.

8) Measuring the carbon dioxide concentration: when the carbon dioxide concentration is greater than 1000ppm, the opening of the electric valve 19 is increased by 5%. If the carbon dioxide concentration is less than 1000ppm, the electric valve 19 continues to be closed. Interval time Δt.

9) After repeating step 8m times, jump back to step 3). In an embodiment, m=5.

Claims (4)

1. A fresh air system based on supply air quality early warning, characterized in that it includes an air conditioning unit (11) installed outside the room (17), and a total return air duct (12), a total air supply duct (13), Fresh air duct (14), exhaust duct (15) and unit air intake duct (16); The air inlet of the main air supply pipe (13) is connected to the air conditioning unit (11); the air outlet of the main air supply pipe (13) communicates with the room (17) through the air supply branch pipe; the fresh air pipe ( The air inlet of 14) is outside the room (17), and the air outlet is connected to the air conditioning unit (11); the air inlet of the main return air pipe (12) is connected with the room (17) through the return air branch pipe; The air outlet of the air duct (12) is connected to the air inlet of the air exhaust pipe (15) and the air inlet of the unit air inlet pipe (16); the air outlet of the air exhaust pipe (15) is outside the room (17); The air outlet of the unit air inlet pipe (16) is connected to the air conditioning unit (11); The total return air pipe section (12) is installed with formaldehyde concentration sensor I (1), nitric oxide concentration sensor I (2), sulfur dioxide concentration sensor I (3), TVOC concentration sensor I (4) and carbon dioxide concentration sensor (5); Formaldehyde concentration sensor II (6), nitric oxide concentration sensor II (7), sulfur dioxide concentration sensor II (8) and TVOC concentration sensor II (9) are installed in the main air supply pipe (13); An electric valve (19) is installed in the fresh air pipe (14). 2. The fresh air system based on supply air quality early warning according to claim 1, characterized in that: the formaldehyde concentration sensor I (1), the nitric oxide concentration sensor I (2), the sulfur dioxide concentration sensor I (3) , TVOC concentration sensor I (4), carbon dioxide concentration sensor (5), formaldehyde concentration sensor II (6), nitric oxide concentration sensor II (7), sulfur dioxide concentration sensor II (8) and TVOC concentration sensor II (9) The measured values are transmitted to the display device installed in the control room (18) through the data line. 3. The fresh air system based on supply air quality early warning according to claim 1, characterized in that it further comprises a controller (10), and the carbon dioxide concentration value measured by the carbon dioxide concentration sensor (5) is transmitted to the controller (10), the electric valve (19) acts correspondingly according to the comparison result of the measured carbon dioxide concentration and the limit value. 4. The intelligent control method of the fresh air system based on the air supply air quality warning according to any one of claims 1 to 3, characterized in that it comprises the following steps: 1) Start the air conditioning unit (11); adjust the electric valve (19) to the initial opening corresponding to the designed minimum fresh air volume; 2) Set the concentration upper limit of each pollutant, namely formaldehyde: S ₁ =0.1mg/m ³ ; nitrogen dioxide: S ₂ =0.24mg/m ³ ; sulfur dioxide: S ₃ =0.50mg/m ³ ; TVOC : S ₄ =0.6 mg/m ³ ; 3) The formaldehyde concentration measured by the formaldehyde concentration sensor I (1) is C11, the nitric oxide concentration measured by the nitric oxide concentration sensor I (2) is C12, and the sulfur dioxide concentration measured by the sulfur dioxide concentration sensor I (3) is C13, The TVOC concentration sensor Ⅰ (4) measures the TVOC concentration as C14; calculation: $I_1=\sqrt{\max (\frac{C11}{S1},\frac{C12}{S2},\frac{C13}{S3},\frac{C14}{S4})\left(\frac{1}{4}\underset{i=1}{\overset{4}{\mathrm{\&Sigma;}}}\frac{C1i}{\mathrm{Si}}\right)};$ The formaldehyde concentration measured by the formaldehyde concentration sensor II (6) is C21, the nitric oxide concentration measured by the nitric oxide concentration sensor II (7) is C22, the sulfur dioxide concentration measured by the sulfur dioxide concentration sensor II (8) is C23, and the TVOC concentration sensor II (9) The measured TVOC concentration is C24; calculation: $I_2=\sqrt{\max (\frac{C\mathrm{twenty\; one}}{S1},\frac{C\mathrm{twenty\; two}}{S2},\frac{C\mathrm{twenty\; three}}{S3},\frac{C\mathrm{twenty\; four}}{S4},)\left(\frac{1}{4}\underset{i=1}{\overset{4}{\mathrm{\&Sigma;}}}\frac{C2i}{\mathrm{Si}}\right)};$ 4) Compare the size of I ₁ and I ₂ : if I ₁ is greater than I ₂ , go to step 5); if I ₁ is smaller than I ₂ , close the electric valve (19), and skip to step 7); 5) The carbon dioxide concentration sensor (5) starts working to measure the carbon dioxide concentration: when the carbon dioxide concentration is greater than 1000ppm, the opening of the electric valve (19) is increased by 5%; when the carbon dioxide concentration is less than 700ppm, the opening of the electric valve (19) is Adjust the degree down by 5%,; when the carbon dioxide concentration is 700-1000ppm, the opening degree of the electric valve (19) remains unchanged; the interval time Δt; 6) After repeating step 5) n times, jump to step 3); 7) The carbon dioxide concentration sensor (5) starts working to measure the carbon dioxide concentration: if the carbon dioxide concentration is greater than 1000ppm, open the electric valve (19) to adjust to the initial opening corresponding to the minimum fresh air volume; if the carbon dioxide concentration is less than 1000ppm, open the electric valve (19) close; interval time Δt; 8) Measure the carbon dioxide concentration: when the carbon dioxide concentration is greater than 1000ppm, the opening of the electric valve (19) is increased by 5%; if the carbon dioxide concentration is less than 1000ppm, the electric valve (19) remains closed; the interval time Δt; 9) After repeating step 8) m times, jump back to step 3).

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