Energy saving method of traditional ventilation cabinet in laboratory

With the development of science and technology, the laboratory fume hood is widely used in scientific research institutions, universities and various laboratories The exhaust air volume of laboratory fume hood is usually determined by the method of controlling wind speed From the theory of air flow, we know that the speed of suction flow decays rapidly In order to ensure that the whole operation port has a certain control of wind speed and avoid harmful substances in the cabinet escaping from the room, the lining needs a lot of power consumption In addition, the ventilation cabinet in the laboratory exhausts a lot of wind and indoor air, which will cause a lot of cold basin loss in the air-conditioned room season and a lot of hot basin loss in winter For the need of energy saving, many energy-saving measures have been put forward, such as air supplement type laboratory fume cupboard, variable air laboratory fume cupboard and air curtain type laboratory fume cupboard Although these measures have certain energy-saving effect, there are more or less some problems in these measures Next, we will discuss the characteristics and existing problems of these energy-saving measures Make up air type laboratory fume cupboard: the characteristic of make up air type laboratory fume cupboard is that the air supply outlet is set at the front and upper part of the laboratory fume cupboard, and about 70% of the total exhaust air is sent out from here When the cabinet door is opened, the air supply airflow forms the air curtain at the operation port to block the escape of harmful gas, and only about 30% of the air is supplemented from the room When the cabinet door is closed, the air accounting for about 70% of the total exhaust air is directly sent to the cabinet and discharged together with the harmful substances in the cabinet This kind of laboratory fume hood does not affect the air flow in the room, nor is it affected by the air flow in the room Because there is less indoor air discharged, it is beneficial to energy saving in air-conditioned rooms at night However, although the air make-up type laboratory fume hood has the above characteristics But it also has the following problems: 1 Because a supply air system is added to the air supply cabinet of the ear filling type laboratory, the initial investment is increased, and the power consumption required is also increased, that is, the operation cost is increased Therefore, when using the air filling type laboratory ventilation cabinet, the recovery period of the whole system should be evaluated In addition, the design of the air supply system should be reasonable, otherwise the energy-saving effect of the air supplement type will be greatly reduced 2 The energy saving of the air supplement type laboratory fume cupboard is attributed to the use of unheated air supply, which will reduce the indoor air temperature and humidity conditions In addition, outdoor air supply in winter will bring uncomfortable feeling to human body and reduce the safety of the operator If the air supply is heated in winter, the air supply degree should be higher than the room temperature, which greatly reduces the possibility of energy saving The operation results of many laboratory fume hoods are not energy-saving, and some systems even consume more energy than the traditional laboratory fume hoods 3 If the air supply speed of the air supply outlet is too large, the venturi effect will be produced, thus the harmful substances will be induced to the working area Second, the ventilation cabinet of the wind changing laboratory: the core of the ventilation system of the ventilation cabinet of the wind changing laboratory is the control system At present, there are many ways to change the air flow through the operation port of the ventilation cabinet of the laboratory by the Zui ventilation control system These methods ensure that when the height of the operation port changes, the operation port still has certain control air speed At present, the two main control methods used by people are the automatic side detection method of wind speed and the automatic side detection method of ventilation cabinet in Shanghai laboratory However, the speed sensor in the ventilation cabinet system of VAV laboratory is a very important component In order to ensure the accuracy of its measurement, temperature compensation is generally needed to ensure its reliable measurement in the laboratory temperature range In addition, when selecting the speed sensor, the durability and the quick response to the speed change should be considered From the above introduction, we can see that the core of the ventilation system of the ventilation cabinet in the VAV laboratory is the VAV control system, but the cost of this system is relatively high According to the operation of some foreign systems, the cost recovery period is more than 2-7.5 years In addition, to ensure the energy-saving effect, the cooperation of operators is essential Third, air curtain ventilation refused: Because of the high energy density and slow speed decay of the jet, in order to overcome the problems existing in the traditional laboratory fume cupboard, a kind of laboratory fume cupboard with air supply outlet is designed The center line of the air supply outlet and the outer edge of the operation port are on a vertical line The operation port of the laboratory fume cupboard is closed by the jet (air curtain) sent from the air supply outlet, and the harmful substances are controlled in the laboratory In the air cabinet, discharge with harmful substances This kind of laboratory fume hood with air supply is called air curtain type laboratory fume hood In fact, the air supply and exhaust system of the air curtain type laboratory ventilation cabinet is the well-known blowing and suction ventilation system It is characterized by that a small amount of outdoor air or indoor air is sent out through the slot type air supply outlet through the air supply system, and the exhaust fan is used to exhaust air from the laboratory fume hood At this time, the laboratory fume hood must be in a negative pressure state, so there is a pressure difference △ P on both sides of the jet, and the jet deflects under the effect of this pressure difference △ P when the ratio of air supply and exhaust is appropriate, the jet just ventilates the laboratory The cabinet operation port is completely closed However, the research results show that for the same supply air volume, with the increase of the width of the supply air outlet, the required exhaust air volume decreases, that is, the air volume in the jet entrainment chamber decreases, the cooling or heat consumption also decreases, and the energy-saving effect is good; on the contrary, for the same supply air volume, with the increase of the height of the operation port of the laboratory ventilation cabinet, the required exhaust air volume increases, that is, the jet entrainment chamber air With the increase of cooling capacity or heat consumption, the energy saving effect is poor Therefore, in order to save energy, it is beneficial to increase the width of the air supply outlet or reduce the height of the operation port of the laboratory fume hood Although the air supply power consumption of the air curtain type laboratory fume hood is increased, the exhaust air volume and exhaust power consumption of the air curtain type laboratory fume hood are greatly reduced Therefore, the energy-saving benefits of the air curtain type laboratory fume hood are great, and some problems need further study Above we introduced three kinds of energy-saving measures and existing problems of the laboratory ventilation cabinet It should be noted that when considering these measures, the air balance and pressure balance of the whole room should also be considered In addition, the energy-saving effect of the laboratory fume hood is closely related to the temperature of harmful substances, the structure of the laboratory fume hood, the rationality of the system design and installation, etc as long as the majority of leisure communication professionals are brave to explore according to the specific situation, they will save more energy.