Wind speed detection and control method of fume hood

Fume hoods are used to vent and ventilate air in the laboratory
.

The material of the fume hood is composed of a variety of all-steel, steel-wood, all-wood, aluminum-wood, plastic steel, PVC structure, etc.
, and its countertop is directly in contact with the operator, which is composed of
solid core physical and chemical plate, stainless steel plate, PVC, ceramics and other materials.

PATEO Xiaobian takes you to understand what are the wind speed and control methods of fume hoods
.

First, the role of the laboratory fume hood 1, pollutant exclusion filtration laboratory in the toxic and harmful substances test, a large number of toxic gas discharge, some laboratories use inline discharge, some use filtration discharge, if not the use of filtration form of discharge, many of these harmful gases can be sucked in by the fresh air unit and sent back to the laboratory, causing direct harm
to personnel.

2, energy consumption to often use the fume hood, fume hood can quickly exhaust the air in the room, at this time need to supplement enough fresh air, and warm air and cool air need to be provided by
the fresh air group.

The fume hood is intelligent, when the personnel operate in front of the fume hood, the fume hood is normally exhaust, when the researchers leave the fume hood, the fume hood glass window will automatically drop, the surface air speed will be automatically reduced, the exhaust air volume will be automatically reduced, so that the energy consumption of air conditioning can be reduced to less than
40%.

Second, the detection of fume hood air volume and wind speed 1, multiple detection of fume hood air volume and wind speed, under standard conditions to achieve practical results
.

2.
For the air outlet without installation of the filter device, it can be implemented
according to the current national industry standards.

3.
For circular air ducts, the cross-section and clear measurement level should be divided
according to the equal total area of the doughnut chart.

4.
The wind speed
of the exhaust hood of the test bench in the laboratory equipment.

Air volume testing is carried out
by technical professional testing as much as possible.

5.
The premise of detecting the air volume and wind speed of the fume hood is that the fan connected to the fume hood can operate normally without problems
.

The overall layout of the fume hood is reasonable and does not hinder the airflow
inside the fume hood.

6.
For rectangular air ducts, the measurement cross-section is divided into several identical small sections, and each small cross-section should be as close to the square
as possible.

The length does not exceed 200 mm, the measuring point is lower than the core of the small section, but the number of measurements on the entire section is not suitable for less than 3
.

Third, the control method of the wind speed of the fume hood 1, the control of the amount of air volume appeared in the 1940s, no matter how open the window of the fume hood in Guangzhou, the air volume always remains fixed
.

The advantage of this method is that the control is simple, but the disadvantages are also very obvious, the wind speed of the fume hood will change with the position of the adjustment window, the safety performance is poor, and the energy consumption is amazing
.

2, bistable state control This control system only has two states, high air volume and low air volume, and its typical application is that when there is no operator at night or in the laboratory, the system is reduced to low air volume operation
.

Energy consumption can be reduced to a certain extent, but like the constant air volume system, its ability to resist external disturbances is still poor, and the indoor pressure fluctuations
are relatively large during the conversion of working conditions.

3, variable air volume control variable air volume control is to adjust the change of door opening or the change of wind speed of Guangzhou fume hood surface to adjust the supply and exhaust air volume of the system through the experimental indoor fume hood, so as to ensure that no matter how the adjustment window opening is, the air speed of the fume hood surface can always be accurately controlled at 0.
5m/s
.

The system is adaptable, which can reduce energy consumption under the premise of fully ensuring safety, but the control accuracy and reaction speed of the valve are highly demanding
.

4, adaptive control adaptive control system, is on the basis of the VAV system, fume hood and biological safety cabinet installation detector, to monitor whether there is anyone active in front of the Guangzhou fume hood or biological safety cabinet, when someone operates, keep the surface wind speed constant at 0.
5m/s, so as to ensure the safety of the operator, and if no one in front of the fume hood operates, the imported wind speed is reduced to 0.
3m/s
.

With this control method, the energy consumption
can be significantly reduced again on the basis of using the VAV system.