Generally speaking, environmental test equipment will have temperature uniformity requirements when doing temperature test, but as a special test equipment in the environmental testing industry------vacuum oven has no temperature uniformity requirement. Perhaps many people will be suprised why there is no temperature uniformity requirement for vacuum oven?

Temperature uniformity is an important indicator of the environmental testing industry, which is a key point that entrepreneurs in this industry must keep in mind. When the temperature uniformity of the equipment is smaller, its accuracy will be greater, and the technical parameter content of the equipment will be higher. Electric hot air drying oven has temperature uniformity requirement, and the natural convection drying oven is the upper limit of working temperature multiplied by 3%, and the forced convection drying oven is the upper limit of working temperature multiplied by 2.5%.(Yuanyao brand temperature uniformity of drying oven is ±1% of the upper limit of working temperature.)As we all know, the realization of temperature uniformity requires air circulation as a prerequisite guarantee, and the interior of the vacuum oven as a closed and clean space, it does not have an air circulation system.

But for vacuum oven, it has no temperature uniformity conception. There is almost no possibility that the temperature of the working oven can be made uniform by the movement of gas molecules in the vacuum oven. Because it is a vacuum, it cannot be like this if there is no air. Therefore, conceptually, we can no longer apply the definition of temperature uniformity stipulated by the usual electric drying oven to the vacuum oven.

The amount of heat radiation in a vacuum is inversely proportional to the square of the distance. For the same object, the radiant heat received at a distance of 20 cm from the heating wall is only 1/4 of that at a distance of 10 cm from the heating wall, it has big difference. This phenomenon is the same as when you bask in the sun in winter. There is a reason why the side exposed to the sun is warm and the side not exposed to the sun is cold.

Due to the structure of the vacuum oven, it is difficult to make the points in the three-dimensional space of the working area, that is, the radiant heat of the spherical surface uniform. At the same time, there is no authoritative evaluation method, which may be the reason why the temperature uniformity parameter is not set in the standard of vacuum oven.

Can the thermometer reading in the vacuum oven represent the actual temperature of the vacuum oven space? Usually, the readings reflected by the thermometer we see in the vacuum oven can be said to be the air temperature under the ambient conditions at that time. But in the vacuum state, there is no air, and there is no air temperature in the vacuum oven. The thermometer just feels the temperature generated by absorbing the heat radiation of the oven. The amount of heat radiation absorbed is related to the roughness of the surface of the thermometer and the ability of the material to absorb, refract and transmit infrared radiation.