Study On Simulating Natural Wind And Its Thermal Comfort Evaluation

In modern society, people's living and working environment are related to the indoor thermal environment closely. Good indoor thermal environment is not only beneficial to people's physical and mental health, but also helps to improve work efficiency and reduce building energy consumption. However, using electric fans and air conditioner by artificially can establish indoor thermal-neutral environment, it also leads to a series of indoor environment problems, such as indoor environment pollution, energy consumption increased, body temperature regulation function and adaptable ability reduced. It is different from natural environment, which has natural, fresh, soft, changeable, hair feel comfortable and good cooling effect by natural wind.Signal test technique, analog control technique, fractal and chaotic theory, and thermal comfort theory are used to study on the airflow characteristics of natural wind and mechanical wind, the simulation technology of natural wind, the fractal and chaotic characteristics of natural wind and simulating natural wind, and the thermal comfort evaluation of simulating natural wind. It is purposed to study the characteristics of natural wind, and apply to air-condition device. The simulation of natural wind is used to improve air supply mode of air-condition terminal device, which improve the thermal comfort of hair feel and the comfort of indoor thermal environment, and save energy.The natural wind concept is identified firstly in the research, which has good thermal comfort to human body. It is defined the object of natural wind analysis and natural wind simulation by air-condition device.Natural wind of different environment and mechanical wind of different devices are sampled to establish wind sample database. The airflow characteristic parameters of wind sample are analyzed, such as average velocity, velocity probability distribution, turbulence intensity, self-correlation function and spectral function. It is showed that the fluctuation, velocity probability distribution, turbulence intensity, self-correlation function and spectral function of sampled natural wind and mechanical wind are different significantly.Based on Takens theorem and phase space reconstruction theory, GP algorithm and small data sets are employed to calculate natural wind sample. The fractal dimension and largest Lyapunov index are obtained by using least squares linear regression analysis, which show natural wind has fractal and chaotic characteristics separately. At the same time, an improved method to identify scaleless region easily is put forward. Factors of velocity change and system effective degrees of freedom are given. It is showed that natural wind has fractal and chaotic characteristics.An air-condition device of simulating natural wind is developed by PLC signal control technique. The characteristics of simulating natural wind under variable speed operating condition and steady-state mechanical wind under constant speed operating condition by motor in air-condition device are tested and analyzed, such as the fluctuation, turbulence intensity, probability distribution, self-correlation and spectral characteristic. It is showed, when natural wind signal as control signal to simulate natural wind, the device can generate dynamic wind which is similar to natural wind. The turbulence characteristics of dynamic wind are good agreement with control signal, and energy is higher in low frequency region and lower in high frequency region. The spectral curve of wind changes rapidly. When the motor of device is constant speed operating condition, the spectral curve changes flatly. At the same time, GP algorithm and small data sets are employed to calculate the sampled simulating natural wind and control signal natural wind. The fractal dimension and largest Lyapunov index of simulating natural wind and control signal natural wind are obtained, which show fractal and chaotic characteristics separately. It is showed that fractal and chaotic characteristics of simulating natural wind and control signal natural wind are similar. Based on human thermal comfort equation, PMV-PPD thermal comfort model is used to calculate PMV-PPD index for evaluating simulating natural wind under isothermal condition. The relationship between dynamic velocity and PMV-PPD is put forward. At the same time, the voting indexes of questionnaire survey are obtained by human thermal comfort experiment under two different airflow models of simulating natural wind and steady-state mechanical wind, such as hair feel, thermal environment comfort, thermal comfort index TSV and thermal sensation index TCV, and so on. Studies have shown that simulating natural wind has wider thermal range than steady-state mechanical wind to suit for different human. The hair feel, thermal environment comfort, thermal comfort index TSV and thermal sensation index TCV of simulating natural wind are improved. The simulating natural wind and its dynamic indoor thermal environment have a good thermal comfort evaluation.