Papers by Author: Li Yang

Abstract: During plastic deformation of materials, part of the plastic work is converted into heat, and the temperature field will be changed, this phenomenon is well known as thermoplastic effect. Based on the analysis of thermoplastic effect, the surface temperature of Q235 steel during quasi-static tensile tests was measured by using an infrared camera, and the surface temperature field and it versus time for different strain rate were obtained. A numerical procedure was devised to model the thermoplastic effect during the tensile tests by using ANSYS software. The results showed that, the heat loss during deformation process will be smaller as the strain rate increase, and the temperature increase on the specimen surface generated by the plastic deformation will be higher. The simulation results matched well with the experiment results showed that it was a good way to analyse the thermoplastic effect by the commercial finite element software.

Abstract: Integral analysis of heat transfer of a laminar falling liquid film along a vertical heated plate with specified heat flux boundary condition was investigated. The temperature distribution of liquid film was obtained by utilizing an integral analysis method, which was compared with numerical solution and other researcher’s results. In this analysis a new concept of thermal changing point was put forward. It’s found that the Nusselt number has a characteristic relationship with thermal changing point, which is obtained by calculation. When the film flow distance is less than thermal changing point, the Nusselt number decreases rapidly. When the film flow distance is greater than or equal to thermal changing point, the Nusselt number reaches to a fixed value. A larger Peclet number or lower initial temperature generally leads to a larger Nusselt number in entrance region, whereas the wall heat flux is found to have no influence on the Nusselt number.

Abstract: Since the molecular force and the molecular volume were ignored in the ideal gas model, and it was less accurate when the ideal gas model was used to depict characteristics of real gas under high pressure, so the real gas model was adopted and the heat transfer was considered, the dynamic variation model was set up for internal gas in the pressure vessel during loading operation. The model was solved by using the numerical simulation method of Runge-Kutta. Comparison was made between the ideal gas model and the real gas model under adiabatic and non-adiabatic conditions, it showed that under low pressure the results obtained by the two models were in good agreement, but under high pressure the deviation was enlarged, the real gas model with considering the heat transfer influenced would be more coincident with the reality.

Abstract: Sea surface temperature (SST) is a prerequisite for sea surface infrared imaging simulation. A temperature model suitable for seawater heat exchange is proposed based on the heat balance of air-sea interface and equations of fluid heat exchange. The model considers the air-sea heat transfer characteristics and influences of penetrating solar radiation in seawater. Effects of the solar radiation, sea surface wind speed and air temperature on SST are analyzed. Temperature model is also used to simulate the SST diurnal variation and compared with the measured values to verify the validity of the model. The results show that the model is useful for solution of sea surface transient temperature field and provides the basis for infrared imaging simulation of sea surface.

Abstract: To improve the accuracy of temperature measurement using infrared imager in complex background environment, based on the principles and the formulas of temperature measurement using infrared imager, altering spectrum method in the infrared temperature measurement was derived. For the temperature measurement of gray body in complex background environment, three response bands should be selected in temperature measurement, and then the surface temperature could be obtained by solving responding two iterative equations. This method could be achieved technologically by two means: setting filters in front of infrared imager, or using infrared imagers with different bands. The simulation results show that the temperature of measured object could be obtained with high accuracy through the method, and its error is very small. Through this method, the temperature of measured object could be obtained without knowing its emissivity and background radiation, so the error caused by the measurement of the emissivity of measured object and background radiation could be reduced.