At present, in the natural ventilation design of factory buildings, improvements should be made in the following aspects. 1. Reasonably design the area of air inlet and air outlet. The natural ventilation of the factory building is to use the hot pressure generated by the temperature difference between the air inside and outside the factory building and the wind pressure generated by the outdoor air flow to make the air inside and outside the factory building exchange continuously and form natural ventilation. However, because the wind pressure is limited by natural conditions, it is variable, and there is no wind pressure when there is no wind, so it is not suitable to be considered as the power of natural ventilation in the factory building. According to the relevant regulations, in the natural ventilation design and calculation of thermal processing plant, only the hot pressing effect is considered, and the wind pressure effect is only taken as an auxiliary factor. In the production process, the thermal processing workshop emits a lot of dirty gases such as waste heat and dust, which worsens the internal environment of the workshop. It is necessary to effectively organize the natural ventilation of the workshop and quickly eliminate the residual heat and dirty gas to improve the internal environmental quality. Under the condition that the height of the workshop and the production heat dissipation are certain, it is the key to improve the natural ventilation effect of the workshop to coordinate the import and export areas reasonably. In the natural ventilation design of the workshop, it is necessary to reasonably coordinate the areas of the air inlet and the air outlet, and strive that the area of the air inlet is not less than or greater than that of the air outlet, which should be an extremely important and effective technical measure to improve the natural ventilation effect. However. In the actual engineering design, some hot working main workshops lack careful and reasonable planning, which leads to public and auxiliary facilities and welfare buildings tightly surrounding the main workshops, making them lose a lot of valuable positions where air inlets can be opened. Without careful study and deliberation, they just gave in to the established architectural design status quo and passively and desperately increased the skylight area and skylight height to about 8m, resulting in the air inlet area being less than 13 of the air outlet area, which made the natural ventilation mode of the factory building extremely unreasonable. Although the natural ventilation skylight of the factory building has increased a lot of construction investment, it has not achieved the due ventilation effect. In a word, the natural ventilation design of the factory building must not only be based on the established architectural layout, but also determine the skylight opening area through ventilation calculation. It can be said that this is just a negative design. Active design should be careful analysis and research, repeated trial and error and correction. Reasonably coordinate the area of air inlet and air outlet, and strive to obtain the best ventilation effect with the lowest economic investment. Specifically, when designing natural ventilation in the workshop, we should first try to achieve a lower neutral surface position on the premise of meeting the ventilation demand, that is, try to set the air inlet area in a lower working area. In other words, try to move the auxiliary building that is blocked by the side wall of the factory building, and give up the precious lower side wall as the air inlet. If it cannot be moved for some reason, its lower part should be overhead, and the position of air inlet should be left to the main workshop. On the surface, it may cost more, but it is still worthwhile compared with improving the environmental quality of the factory building. And even economically, it doesn't necessarily cost much in the end. Because if the air inlet of the factory building is blocked, the ratio of F 1 and F2 will be unbalanced, the position of neutral surface will be raised, which will obviously reduce the exhaust pressure, resulting in a substantial increase in the skylight area, and the investment spent on improving the skylight may be higher than the overhead expenses of the auxiliary building. Second, efforts should be made to overcome the problem of short intake flow. The so-called short air intake flow refers to the phenomenon that fresh air entering the factory building from the air inlet is heated before entering the work area, and then rises to the skylight exhaust port and is discharged outside. Obviously, such an air inlet has not played a role in improving the air quality and thermal environment in the work area. Therefore, in order to improve the natural ventilation effect of the workshop, we should try our best to avoid this phenomenon of insufficient air intake. As mentioned above, air intake through the high side window will cause the phenomenon of short intake air flow. In addition to the reasons that have to be done in the above special circumstances, it should be avoided as much as possible in general. Because more investment is needed, it is not worth the loss to set up a large area of high side windows without playing its due role. That is to say, it is not necessary to design the high side window usually set above the crane rail surface in the factory building as an opening window, and a fixed lighting belt with low cost can be used. However, considering the ventilation needs of operators during crane maintenance, it is still necessary to set a vent on the lighting belt at regular intervals. Of course, in some cases, in order to save investment, the high-side window is sometimes considered as the exhaust outlet in the natural ventilation design, and in this case, it is of course necessary to open the window. However, in order to avoid the phenomenon of backflow when the wind pressure is greater than the hot pressing, disturb the natural ventilation organization of the factory building and worsen the indoor environment, it is necessary to set up a windshield device similar to a skylight when designing a high-side window as an exhaust outlet. There are many factors that cause short airflow in the workshop, so in the design of natural ventilation, we should carefully analyze and take effective measures to avoid this phenomenon as much as possible. For example, when the heat source in the factory building is arranged near the external wall of the factory building, short flow will inevitably occur at the air inlet. In this case, the best solution is to change the layout of the factory, but sometimes it is more difficult. Only open more windows, open large windows in the intermittent parts of heat sources, and in some cases, even open windows in higher positions to make up for the losses caused by short air intake. 3. Effective measures must be taken in the natural ventilation design of multi-span thermal processing workshop. In large iron and steel enterprises, there are some multi-span hot working workshops, such as hot coil warehouse of hot strip mill and cold bed area of hot strip mill. This kind of workshop not only has a large amount of heat dissipation, but also has many spans, and the width of some workshops exceeds 150m, so it is a long-standing problem in the natural ventilation design of workshops. Because the workshop is very wide, the air intake only depends on the external walls on both sides, not only the air intake area can not meet the requirements, but also the air intake depth is far from reaching. For the middle part of the factory building, it is bound to form an all-round short flow of air intake. In this case, if effective measures are not taken, the skylight area can only be calculated by natural ventilation, and no matter how many skylights there are, it is difficult to meet the requirements. The way out of natural ventilation design lies in broadening ideas, finding another way and taking effective measures. Fourth, don't ignore the ventilation problem in the cold workshop. There is a misunderstanding in the design of workshop natural ventilation, that is, when it comes to natural ventilation, it is only related to hot workshops. Because there is no residual heat or very little heat in the cold working workshop, the current work of natural ventilation design and calculation according to hot pressing has lost its basis. Therefore, few people care about the ventilation of the cold workshop. The author made a special investigation on indoor thermal environment of some cold working factories in southern China in summer. It is found that the indoor thermal environment quality of most cold working factories in Chongqing, Wuhan, Hunan, Taiyuan and other areas with high summer temperature is very poor in summer. Although the production waste heat discharged by the factory building is very small, it is unbearable because of the radiant heat and poor ventilation of the roof, sultry and oily smell. Workers complain, generally reflecting dizziness, irritability, anorexia and other symptoms. The indoor thermal environment of the workshop with skylight on the roof is obviously much better, because some glass window fans are open, which plays a role in ventilation. Therefore, for the cold workshop in the southern region and the hot summer region in the north, besides the roof insulation layer, good ventilation conditions must be created in the design. Two-span and below workshops can be ventilated with high side windows, and multi-span workshops must be equipped with enough skylights to solve the problem of ventilation and lighting. For smaller factories, ventilated roofs can also be used to solve the ventilation problem. It is not advisable to ignore the ventilation design because it is a cold workshop. 5. Attention must be paid to solving the problem of rainwater floating in ventilation skylight. In recent years, serious rain floating in ventilation and exhaust skylight has occurred frequently, which has caused certain losses to production. The natural ventilation design of the workshop solves the problem of ventilation and exhaust in the workshop, but it brings the disadvantages of floating rain, and the use function of the workshop is unacceptable. Therefore, it must be solved seriously in the design. At present, rectangular ventilation skylight is commonly used. In the previous design, the rectangular ventilated skylight was equipped with a rain shield at the vertical opening or a rain shield at the horizontal opening, and the rain shield at the horizontal opening was better than the former, so it was widely used in industrial workshops. Intuitively speaking, the skylight with this structure can block the floating rain at any angle in a straight line, but in fact, it is only for straight line rain. When the wind and rain are subjected to certain resistance, it will form a variant vortex wind and rain, and its rain drift angle may appear at 0. Angle, even negative angle phenomenon, that is, the wind and rain are swaying into an arc. In this case, it is inevitable that it will rain. This kind of ventilation skylight was adopted in the workshop design of a large factory. In a local rainstorm, after the wind and rain were blocked by the mountain, the local variation of vortex wind and rain was formed, which led to serious skylight rain and strong reflection. Therefore, this kind of rectangular ventilation skylight can only be used in industrial workshops in areas with large exhaust air demand, lax rain protection requirements or no heavy rain. Therefore, it is suggested that the design and construction can be carried out according to the following principles: (1) set the high-side exhaust window near the cornice of the factory building, and it is forbidden to leave a solid wall on the upper part of the exhaust window to avoid rain caused by vortex. (2) The vertical windshield of the high-side exhaust window is heightened and designed to be similar to the windshield of a fully enclosed rectangular ventilated skylight. The upper part of the windshield is folded to the roof in an inclined shape to prevent rainwater from floating at any angle. (3) Add a horizontal windshield between the wall of the lower mouth of the high-side exhaust window and the vertical windshield, leaving no gap for rainwater drainage. On the one hand, it can prevent wind and rain from pouring into the factory building through the gap, on the other hand, it can also prevent a large number of dusty rainwater from flowing down through the gap to pollute the wall and the lower side window, which is unfavorable to the environment outside the factory. It is suggested to set a downpipe for organized drainage treatment. In recent years, there are many types of ventilation skylights. In addition to the above, there are horizontal skylight, well skylight and spherical skylight. Among them, the spherical skylight is also fully enclosed, which will not cause the phenomenon of floating rain; The positions and causes of rain floating in other types of skylights are similar to those in rectangular skylights, which can be handled with reference to the analysis and improvement principles mentioned above.

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