ABSTRACT
Artificial spray fog will come into being cool target because of the strong evaporation and convection but weak radiation heat flux, when it is used for defence of infrared imaging guided missile. Also, when it is the contrary condition, the water fog will come into being hot target. In order to open out the phenomenon particularly, a math model which can account for the cool/hot effect produced by water fog shielding the thermal radiation is established by coupling the calculation of radiation transfer equation and energy conversation equation, based on the Mie theory. This model is proved to be accurate in comparison with the Monte-Carlo method and Lambert-Beer' law. The water fog is seemed as absorbing, emitting and anisotropic scattering medium, and the medium radiation, multiple scattering, target radiation flux, and environment influence such as the conductivity, convection turbulent heat diffusion and evaporation is calculated. The phenomenon of cool/hot target effect can be shown in detail with this model.
ABSTRACT
According to the theory of infrared radiation and principles of temperature measurement using infrared imager, a universal mathematical model of infrared imager is established. Based on the normal emissivity characteristics of measured surface, the mathematical model is simplified, and the formula of temperature measurement using infrared imager is obtained. Through the relevant experiment, it is proved that the sum of emissivity and reflectivity of objects remained basically unchanged in a certain temperature range. The sum of emissivity and reflectivity of objects is relevant to the object types, surface conditions and the object temperature. The closer an object to Lambertian objects, the greater the sum is and the closer it is to 1. The farther the surface conditions deviate from the Lambertian surface, or the smoother the surface, the smaller the sum is. Experimental results show that if the object is close to Lambertian objects, it could be regarded as Lambertian, without the need for amendments to the actual objects. For non-Lambertian body (especially the smooth surfaces and low-emissivity objects), the amendment is necessary, or the temperature measurement error will increase, or even the obtained temperature is very far away from its true temperature. The study shows that, through the amendment, infrared temperature measurement on non-Lambertian objects is available.
