Analysis of a new method of measurement and visualization of indoor conditions by infrared thermography

Abstract

We present a new tool of measurement and visualization of the indoor ambient parameters (air temperature, air speed, and mean radiant temperature) by infrared thermography. The theoretical fundamentals are discussed. They include a design stage, the mathematical modeling, the measurement procedure, and the performance evaluation through error analysis. The measuring system consists of a set of auxiliary devices (targets) arranged on a measurement grid. An infrared camera measures their temperature histories. From each temperature chronology, the three ambient parameters are locally deduced together by solving an inverse heat transfer problem. The results are then mapped to provide a 2D or 3D visualization. The question of identifiability is addressed leading to a robust parameter estimation algorithm. The robustness of the algorithm is tested for a wide range of noisy data during a numerical experiment. The numerical data are built by varying the air speed from 0 ms(-1) to 2 ms(-1) with a step of 0.2 ms(-1), the air temperature from 15 °C to 30 °C with a step of 3 °C and the mean radiant temperature from 15 °C to 30 °C with a step of 3 °C. It appears that stability and repeatability are guaranteed by the presented method for the range of ambient parameters and accuracy usually found and needed in indoor conditions. Brief illustrative experimental results are given as an initial validation of the method. Since the spatial distributions of these ambient parameters are obtained qualitatively and quantitatively, the method is suitable for indoor microclimate mapping, visualization of air patterns, building inspection, thermal comfort assessment, etc.