Pascale Wouters

Global modelling of heat transfer in crystal growth furnaces

Abstract A quantitative prediction of the thermal field and the location of the melt-crystal interface during growth requires a precise knoqledge of the heat transfer taking place in the entire furnace. The problem is highly complex since it involves an accurate calculation of radiation between the different surfaces and conduction in the constituents. Radiative exchanges are calculated with the assumption of diffuse surfaces and with use of a viewed and hidden part algorithm together with a Galerkin discretization. The model has been extended for taking semi-transparent materials into account. The shape of the liquid-solid interface is a variable of the problem and is calculated as being the melting isotherm. Examples of germanium and gallium arsenide furnaces are analysed, showing the efficiency of the method.

Numerical-calculation of the Global Heat-transfer in a Czochralski Furnace

Abstract A quantitative prediction of the thermal field and of the location of the interface in the Czochralski process requires a precise knowledge of the heat transfer taking place in the entire furnace. The problem is highly complex, since it involves radiation, heat conduction, heating elements and convection-diffusion in the melt. These features are taken into account in our model while outer control parameters - such as power dissipated in the heater and convective losses on the enclosure - are used as input instead of arbitrary boundary conditions. Each constituent such as the heater, the crucible, the melt and the crystal is covered by a finite element mesh. The radiative exchanges within each enclosure are calculated with the assumption of the diffuse-gray surfaces and with the use of a viewed and hidden part algorithm together with a Galerkin discretization. The model allows one to investigate the sensitivity of the temperature field with respect to the geometry of the furnace, the presence of a heat shield and the material properties of the constituents.

Avoiding compliance and resistance through collaboration? A Belgian teaching portfolio case

In this paper, the authors describe the implementation process of a teaching portfolio at a Belgian university. The case is intriguing because it departs substantially from what others have described as the typical antagonistic way in which academic developers interact with formal leaders. Rather than being caught in an edgy game of compliance and resistance, the actors present themselves as partners in a collaborative process throughout three consecutive phases. To interpret this process, reference is made to a collaborative framework from a social psychology perspective that could help avoid compliance and resistance.