| The display and storage of many space precious cultural relics call for great demand on the dominate quality of air humidity. The humidity sensor is not suitable to be installed in the display or storage space, but installed in the tube connected which is communicated with the display or storage environment for the safety, display and dominate of equipment maintenance and other considerations of cultural relics. For time-lag phenomenon with the use of tube connected in the cultural relics’cabinet, it is researched on the transmission characteristics of humidity signal in the tube connected with the changes of feature size providing correct control parameters for humidity controller in the thesis.First of all, it is established with regard to steady state diffusion model of the two component diffusion of water vapor and air with the combination with the basic theory of water vapor diffusion through stagnant air. Results show that the equivalent diffusion coefficient in steady state increases with the increase of temperature and the diameter of tube connected, and gradually close to the free diffusion coefficient; The change on the length has little influence on it. In order to overcome the shortcoming of the above method that the test cycle is too long, a method for retrieving the equivalent diffusion coefficient of water vapor according to the change of humidity with time is provided based on the inverse problem of humidity transfer in the non-steady state. The data in effective test time is obtained by the experimental method of solve the problem; It is acquired to establish of humidity transfer model in non-steady state and then make the equivalent diffusion coefficient of water vapor as optimization variable, using finite difference method to obtain the stable instantaneous humidity field; It is demanded to make the difference of Simulation values and experimental values as the optimization objective function. By the minimization of the optimization objective function, the optimal solution of the inverse problem is obtained. The obtained equivalent diffusion coefficient is in agreement with the method of steady state.The hysterics time and time constant of humidity transfer in the different characteristic dimension of are obtained by solving model of non-steady state humidity transfer. And then results show that the time-lag with humidity transmission of tube connected increases linearly as the length increases and the time constant decreases with the increase of the diameter of the tube connected obeyed the exponential law.The transfer function of the tube connected is established and it is solved by the non-steady response curve. The simulation curve and field experimental data curve are compared to verify the validity of the established system model. The results show that transfer function of the humidity signal from the display or storage environment to the tube connected is composed of pure lag link and first order inertia link.On the basis of the results of the above study, it is given about the estimated chart on delay time and the time constant of the tube connected humidity signal. The estimated results show that lag time of humidity transfer increases linearly with the increase of the length of tube connected, and the time constant decreases with the increase of the diameter of the tube connected obeyed the exponential law. |
