Constant air volume air conditioning system is a kind of all air treatment system. The constant air volume air handling unit mainly refers to the constant air supply flow. In the process of air handling, the flow of circulating air is adjusted to ensure the freshness of indoor air. The energy-saving unit is double fan air handling unit. Air volume hood is widely used in air purification equipment of dust-free workshop.

The air handling unit is composed of fresh air section, mixing section, filtering section, cooling / heating section, humidification section, air supply section, return air section, etc. Fresh air section: fresh air from the atmosphere into the building. Mixing section: mix the fresh air from the outdoor with a certain proportion of air conditioning return air. Filter section: filter the mixed air of outdoor fresh air and air conditioning return air to remove dust, particles, etc. Cooling / heating section: generally, coil surface cooler is used to heat or cool the air outside the pipe through the air conditioning water flowing inside. Humidification section: humidify the air below the humidity requirement. Air supply section: the treated air is sent to the building by the air supply fan through the air supply pipe and air supply outlet. Return air section: in order to utilize the residual heat / cold, the air extracted from the building is partially discharged from the building for treatment and reuse. VAV is a kind of air conditioning system which can adjust and control the temperature of a certain air conditioning area by changing the air supply rather than the temperature of the air supply. VAV air conditioning system is convenient in design and installation, flexible in layout, small in building space, convenient in use, high in reliability, great in energy saving potential, flexible in control, and can avoid the trouble of freezing water and condensation water ceiling.

Use of air volume hood in dust-free workshop

The air volume hood is mainly composed of three parts: air volume hood, base and PDA. The air volume hood is mainly used to collect the air volume and collect the air to the air speed homogenizer on the foundation. A wind pressure sensor is installed on the uniform wind speed, which reflects the change of wind speed, and then calculates the air volume according to the size of the base. PDA is used for the display of air volume hood, and the large LCD screen is intuitive. The data of wind speed, wind temperature and air volume can be obtained directly. The recording time interval can be set for continuous parameter recording, so as to analyze the data. The measured and recorded data are recorded on the memory card and will not be lost. The data can be transferred to the PC through the serial port of the computer and further application can be made.

The air flow at the tuyere of the central air conditioning system is complex, so it is difficult to measure. Only when it can't be measured at the branch pipe, can it be measured at the air outlet. Generally, the method of air volume cover and air speed at the air outlet is used. Compared with the air velocity method, the air volume hood can quickly and accurately measure the average ventilation volume of the air outlet. Whether it is the air supply, return and exhaust outlets installed on the ceiling, wall or ground, equipped with corresponding sensors, it can directly read the wind speed, pressure and relative temperature and humidity, especially for the diffuser type air outlet. When in use, the cover shall be close to the ceiling surface to make the air outlet completely contained, so that it can be read directly.

When the size difference between the air volume hood and the tuyere is large, the measurement error will be large, so it is necessary to use the hood with similar size for measurement. According to the size and area of the air outlet to be measured, select the air volume hood with the area close to the air outlet, and the length of the long side of the hood shall not exceed 3 times of the length of the long side of the air outlet; the area of the air outlet shall not be less than 15% of the boundary area of the hood. After selecting the appropriate hood, open the measuring instrument, check that the instrument is normal, so that the settings of the instrument meet the use requirements; determine the placement of the hood Position to cover the air outlet, the air outlet should be located in the middle of the cover body; ensure no air leakage, observe the display value of the instrument, and read the air volume value after the display value tends to be stable. When the air volume of the air outlet is large, the resistance of the air volume cover body and the throttling of the measuring part to the air outlet will increase, resulting in more air volume decrease. In order to eliminate the small air volume of this part of the air outlet, back pressure compensation is needed. According to the read air volume value, consider whether back pressure compensation is needed. When the air volume value is ≤ 1500m3 / h, back pressure compensation is not needed. The read air volume value is the air volume value of the measured air outlet; when the air volume value is > 1500m3 / h, back pressure compensation baffle is used for back pressure compensation, and the read instrument display value is the air volume value after the measured air outlet compensation.

Back pressure compensation mode test: in order to make the measured air volume closer to the real value of the air volume, reduce the test error caused by the pressure loss caused by the air volume hood to the system. It is recommended to use the back pressure compensation mode to test when the air volume is more than 1500 m / h. 1) when the test mode is "b.press", press the "start" key to start the measurement, and the test will stop automatically after the air volume is stable. 2) The interface prompts "open the back pressure plate". After manually opening the back pressure plate, press the "start" key, and the instrument starts to test. 3) After the test, the instrument will stop automatically and display the air volume after the back pressure compensation. 4) If you want to save the air volume when it stops, you can press the "save" key to save the measured air volume value this time, and "cycle" will automatically add 1.

Application scope of air volume Hood: the air flow at the air outlet of the air conditioning system is complex, and the measurement work is difficult. Only when it can't be measured at the branch pipe, can it be measured at the air outlet. Generally, the method of air volume cover and air speed at the air outlet is used. Compared with the air velocity method, the air volume hood can quickly and accurately measure the average ventilation volume of the air outlet. Whether it is the air supply, return and exhaust outlets installed on the ceiling, wall or ground, it can directly read the wind speed, pressure and phase with corresponding sensors.