The estimation of thermal diffusivity using NPE method

비선형 매개변수 추정법을 이용한 열확산계수의 측정

The method of nonlinear parameter estimation(NPE), which is a statistical and an inverse method, is used to estimate the thermal diffusivity of the porous insulation material. In order to apply the NPE method for measuring the thermal diffusivity, and algorithm for programing suitable to IBM personal computer is established, and is studied the statistical treatment of experimental data and theory of estimation. The experimental data obtained by discrete measurement using a constant heat flux technique are used to find the boundary conditions, initial conditions, and the thermal diffusivity, and then the final values are compared with the values obtained by some different methods. The results are presented as follows:(1) NPE method is used to establish the estimation of the thermal diffusivity and compared results with experimental output shows, that this method can be applicable to define the thermal diffusivity without considering hear flux types. (2) Because of all of the temperatures obtained by the discrete measurement on each steps of time are used to estimate the thermal diffusivity. Although some error in the temperature measurements of temperature are included in estimating process, its influences on the final value are minimzed in NPE method. (3) NPE method can reduce the experimental time including the time of data collecting in a few minutes and can take smaller specimen compared with steady state method. If the tube-type furnace is used, also the adjusting time of surrounding temperature can be reduced.

본 연구에서는 역산법으로 열확산계수를 추정하기 위하여 비선형 매개변수 추 정법을 사용하며, 실험데이터의 통계적 처리방법, 추정이론을 정리하여 이 추정법에 적합한 알고리즘을 만들었다. 수정된 Gauss법을 컴퓨터에 사용할 수 있도록 프로그 램을 개발하였으며, 이 방법의 정확성을 증명하기 위하여 일정열유법과 동일한 실험장 치를 사용하되 경계조건이나 초기조건을 시간의 변화에 따라 이산적으로 측정하여, 매 개변수인 열확산계수를 온도의 함수로 찾고자 하였으며, 통계적인 개념보다는 역산적 인 면에 더 치중하였다.