Ventilation control issues in grain storage silos
01. Practical application
[Example 1] Ventilation control problem in grain storage warehouses. In grain storage, appropriate humidity is a prerequisite for ensuring grain quality. Generally speaking, if the absorption and evaporation of grain moisture are equal, this humidity is called the equilibrium point humidity. Only when the actual humidity is below the equilibrium point humidity can grain quality be guaranteed. In the ventilation control of grain storage silos, it is necessary to calculate the equilibrium point humidity based on grain temperature and grain humidity, and compare it with the atmospheric humidity, and then decide whether to automatically ventilate based on the ventilation simulation conditions. Some measured data on the relationship between equilibrium point humidity, grain temperature, and grain humidity are shown in Table 1. Please complete the following operations.
(1) Calculate the equilibrium point humidity for every 1°C change in temperature and 1% change in humidity within the corresponding range.
(2) Draw the equilibrium point humidity distribution diagram according to (1).
(3) Mark the highest equilibrium point humidity with a red five-pointed star according to (1).
■ Table 1 Relationship between equilibrium point humidity b, grain temperature t, and grain humidity w
According to the meaning of the question, the equilibrium point humidity is related to the grain temperature and grain humidity, that is, b=f(t,w). But we don’t know what function f here is. All we know is a part of discrete test data. There is no way to support decision-making by relying solely on this part of the data. Therefore, two-dimensional interpolation is used to calculate more data.
Procedure 1:
Figure 1 shows the interpolation results. It can be seen that the data is richer and more detailed. Based on this result, the automatic grain condition measurement and control system can achieve ventilation control more accurately.
■ Figure 1 Grain storage ventilation control interpolation results
Program 2: The sample point data can be a row vector or a column vector. One of the interpolation point parameters must be a column vector but not both at the same time. For example, the following program can achieve the same effect as Program 1.
