Tri Nguyen-Quang

This paper presents a study of frequency effects on the heating induction process for aluminum alloys. Our objectives are to deal with the more general induction heating issues in the semi-solid metal forming by taking into account the conditions of radiation and convection during the heating combined with cooling process at the surface of samples, hence the spatial-temporal variation of temperature on the whole sample volume. The Lab experiment for a cylinder aluminum alloy and numerical approaches for the physical model of a 2D heat transfer equation with the boundary conditions of convection and radiation were carried on. It is interesting to find that with a smaller rank of heating frequency 21–24KHz on the aluminum alloy, the distribution of the temperature is very homogenous on all samples from the center to surface areas, i.e. on the whole heated volume. We also observed that the quality of our samples after the induction heating process was very good and the ‘foot elephant’ pattern did not happen.

Winter design dry-bulb temperatures at 99% and 97.5% frequency levels were developed and analysed by multiple regression and spatial correlations developed using as regressors altitude, latitude and longitude. Winter design dry-bulb temperatures were negatively related to altitude and latitude. Latitude was the most influential regressor on the winter design dry-bulb temperature distributions. Summer design dry- and wet-bulb temperatures, and wet-bulb depressions at 1%, 2.5% and 5% frequency levels were also developed and analysed by multiple regression and spatial correlations were developed using as regressors altitude, latitude and longitude. Altitude was the only statistically significant influential regressor on the summer design dry-bulb temperature distributions. Latitude was the most influential regressor on the summer design wet-bulb temperature distributions. Altitude was the only statistically significant influential regressor on the summer design wet-bulb depression distributions. Spatial correlations and distributions of prevailing wind speeds, mean daily ranges, and median of annual extreme temperatures were developed and mapped.