Why is the relative position of the equipment determined based on the annual \"minimum\" frequency wind direction conditions rather than the \"maximum\"?

Does no one know? ? ? ? ? ? ?

Are you referring to the \"Regulations on Safety and Health Design for Chemical Enterprises\"? [2.1.8] The location of chemical enterprises must take into account local wind patterns; generally, they should be situated upwind of the direction from which winds blow most frequently throughout the year in urban areas and residential zones near factories. 】It doesn’t matter even if it’s not this; the reason is similar. I remember that in the 1980s it was specified as the downwind direction of the wind direction with the highest frequency throughout the year, but it was later found that the opposite direction of the dominant wind direction is generally not the wind direction with the lowest frequency; therefore, making such a change would have a lesser impact on the local residents and is more scientific. This post was last edited by zyy1311 on 2008-2-26 09:04.]

I have been studying the meaning of the phrase \"the upwind side of the wind direction with the lowest frequency,\" and I eventually discovered that the lowest frequency is a hidden overarching concept. Generally, we believe that chemical processing plants should be located in the downwind direction, so that the exhaust gases emitted do not affect users in the downwind areas. The meaning of being on the upwind side of the minimum frequency is that this location has the lowest likelihood of being on the upwind side throughout the year; in other words, it is basically on the downwind side. JAST SO SO

Got it, thanks for everyone’s discussion.

Due to China’s monsoon climate, with north winds in winter and south winds in summer, chemical plants do not have a fixed windward or leeward side throughout the year; the side where the wind blows least frequently is the most suitable for China’s conditions.

Explanation from a design institute: 4. The layout design of the installation takes into account the influence of wind directions, primarily to avoid fires caused by wind and to minimize pollution resulting from wind patterns. In the past, the term used for wind direction was *usually “dominant annual wind direction.” In previous literature or standard specifications, whenever terms such as upwind, downwind, or side wind are used, they refer to the prevailing wind direction. According to statistics from China’s meteorological data, among the wind rose diagrams of 79 urban areas across the country, 39 locations, accounting for 50%, have their dominant wind direction and secondary wind direction on the same axis. In other words, when only the downwind direction of the dominant wind is considered, it happens to be the upwind direction of the secondary wind direction; thus, for much of the year, these areas are affected by the secondary wind direction, failing to meet the requirements for fire prevention and pollution reduction. Therefore, the term \"dominant wind direction\" is not very accurate, so wind direction frequency is used instead. Method of creating a wind direction rose chart: Wind directions are divided into 8 or 16 sectors, and the frequency of winds in each direction is represented by corresponding proportional lengths marked on the axes of the 8 or 16-axis chart. Then, the ends of the lines representing adjacent directions are connected by straight lines, forming a closed polyline; this closed polyline constitutes the wind direction rose chart. Wind direction wind roses can be classified into monthly, quarterly, and annual types. Using multi-year statistical data is the best approach, but wind direction is greatly influenced by regional factors. Due to differences in terrain, such as the presence of mountains and valleys, the data from nearby weather stations often lack consistency. It is best to conduct actual measurements in the area where it is located. In standard specifications published in recent years, the term minimum frequency wind direction has been adopted. According to statistics, among the wind direction roses for the aforementioned 79 urban areas, 69 of them, accounting for 87%, have the wind direction with the lowest frequency throughout the year located on the side of the dominant wind direction for the whole year (of which 21, or 28%, have the wind direction with the lowest frequency and the second-most dominant wind direction lying on the same axis), while in the remaining 10 cases, the wind direction with the lowest frequency and the dominant wind direction are on the same axis. As can be seen from Figure 1.1.1, the approach of using the wind direction with the lowest frequency throughout the year is reasonable. However, taking the influence of wind direction into account, only a relatively reasonable estimate can be obtained, as wind direction observations in a given area can only be made at a specific observation station within that area; this station may be quite far from the locations where factories are built in that area, leading to regional influences, which is why only a relatively reasonable estimate can be achieved.

Got it; I’ve learned quite a lot more.