THE RESEARCH OF METROLOGICAL CHARACTERISTICS OF THE THERMO ANEMOMETER BASED ON THE MEASUREMENT CONTROL OF THE HEAT FLOW OF THE MICROWAVE CAMERA

Abstract

The purpose of the article is to study the rational operation of the hot-wire anemometer in accordance with the dynamic characteristics and measurement errors, when implementing the process of drying raw nuts in an industrial microwave chamber. The technique of studying the informative parameters of the heat flow was used to determine the rational mode of operation of the hot-wire anemometer and to reduce the time of heat treatment of nut raw materials. The characteristics of the thermal transient process of drying raw nut materials in a microwave chamber are investigated. Theoretical substantiation and an algorithm for determining the dynamic characteristics of the hot-wire anemometer under the external sinusoidal effect of the heat flow temperature are given, algorithms for determining the instantaneous values of the temperature increments of the hot-wire anemometer sensitive element in the process of drying nut raw materials are given. On the basis of the general theory of errors of indirect measurements in the investigated range of variation of the rate V of the heat flow, the values of the relative systematic errors of indirect measurements of the rate of heat flow in the range from 10 to 40 m / s were determined. It was found that in accordance with the dynamic characteristics and measurement errors when blowing a moving heat flow of nut raw materials, the most rational is the mode of constant resistance of the hot-wire anemometer. Solutions of the differential equation describing the dynamic heat process when the temperature of the moving heat flow changes according to the periodic law, i.e. stationary, non-stationary and complete. The results of calculating the constant times of the hot-wire anemometer thread τ_п and τ_тп of the moving heat flow, respectively, were τ_п = 0.59 s and τ_тп = 0.6 s, the time constant of the hot-wire anemometer is practically commensurate with the thermal time constant of the moving stream blowing over the nut raw material. It consists in the fact that the theoretical position of the hot-wire anemometer has been further developed in the direction of researching the characteristics of the thermal transient process of processing nut raw materials, all this makes it possible to determine the ranges of changes in the signals of the thermal device, which correspond to the ranges of change in the informative characteristics of the moving heat flow, and also allows the selection measuring equipment, establish rational operating modes of hot-wire anemometers and automated devices that use them in accordance with errors and sensitivities. The proposed algorithms for determining the informative parameters of the heat flow in the study of the transient process of heat transfer from the moving air flow to the sensitive element of the transducer, the results of the errors in measuring the velocity V of the moving heat flow, make it possible to calculate, design and create measuring automated devices that use hot-wire anemometers in food and processing industry, instrument making and chemical engineering.