Ventilation design adopts the following steps and schemes:
(1) the laboratory selects a certain number of fume hoods according to the process requirements and function layout, and some of them have partial air exhaust hood. It is usually checked that the ventilation rate is much greater than 10 times, and it is usually more than 20 to 30 times. However, the ventilation frequency is the ventilation volume calculated according to the maximum open area of the fume hood, and the data and experience indicate that only 18 or fewer people are using the 100 ventilators in 99% of the time. Therefore, the ventilation quantity and air ventilation frequency of the minimum open area of the ventilation cabinet should be checked, and the integrated exhaust ventilation system should be added if less than the number of ventilation times.
(2) the ventilation system of the laboratory is completely new, and the exhaust of the fume hood is not in the indoor circulation. Because the laboratory requires that the room is negative pressure relative to other auxiliary areas. Therefore, the new air volume of the laboratory is designed to be 70% of the exhaust volume. In addition, the new wind from the 20th-30th is sent to the laboratory assistant room, office, management room, inner corridor, etc., and then it is added to the room by door and window gap.
(3) the air volume balance of the fume hood can be controlled by the air volume control system, that is, the air volume is constant, and the air supply volume is constant and the air volume is constant. This method is suitable for the laboratory with the minimum ventilation requirement.
(4) for the exhaust air volume is greater than the minimum air volume required room can also make use of two sections of general risk control system to ensure balance, namely according to the displacement signal of fume hood, exhaust fan, there are two kinds of blower air supply condition, low air condition is applied to maintain the minimum air changes of requirements, save energy consumption. The variable air volume control system is adopted in this case. Fume hood airflow changes, also will be relatively small, exhaust air exhaust fan of the demands placed on the roof and now with the change of the position of the fume hood cupboard door and variable frequency, reduce the air volume, ensure ventilation counter wind speed is constant. At the same time, the automatic control system changes the frequency of all new wind turbines, reduces the air volume and maintains the negative pressure balance. The variable air volume system can reduce the energy consumption of the system. The maximum and minimum ventilation rate of the system is close to the consideration of the fixed air volume system, which makes the system simple and reduces the initial investment.
In addition to the special requirements for the fume hood mentioned above, the ventilation system also has certain requirements and standards for other equipment and control systems. The selection of the fume hood should not only satisfy the exhaust ventilation and capture ability, but also need to change the air volume immediately according to the adjustment door, and maintain the constant surface wind speed. The author suggests that the measurement and control of the system air volume should be measured by the displacement of the cabinet door rather than the surface wind speed. Laboratory pressure control and minimum ventilation rate in addition to the equipment type selection factors, the control of the ventilation system design and control system is the key factor, to ensure that the system response time should be enough short (< 1 second), the imbalance will lead to fume hood exhaust ventilation system and the ability to capture is lost, the air flow lab, building internal pressure is not stable.
One more thing to note is that the system should be type pressure change has nothing to do, the change of system air volume wont because of the change of the air static pressure makes slow reaction time influence the accuracy of system flow. Related model systems can also cause traffic pressure equipment cant accurate control, slow reaction time will let send reverberate exhaust equipment, speed instability will have a lot of balance problem, fluctuating send complicate airflow balance, exhaust system, and automatic control system cannot achieve regulating function.
So, is the state of the fume hood for monitoring the system first, after accepting damper sensor signal can be calculated damper area (air), the air volume to (no pressure) the valve control signal, adjust the opening of the valve, air output with immediate change, exhaust air to exhaust fan frequency conversion adjustment air output.
