Boiling is a process widely used in industrial and scientific applications to 
promote heat transfer because of high heat transfer coefficients associated to 
the phase change. It can be mentioned, for instance, the use of heat pipe to 
cool down compact electronic equipment and the heat exchangers in nuclear power 
reactors. Safety and design guidelines of such equipment rely on the fundamental 
understanding of heat transfer and fluid mechanics phenomena that occur in the 
near-wall region where the bubbles grow. For instance, it is well known that the 
dewetting dynamics (promoted by dry-spots formation) on the heated wall is a key 
parameter to understand the boiling crisis.  

Another near-wall feature at nucleate boiling is the formation of thin liquid 
films that can occur during the growth of vapor bubbles on the wall. This liquid 
layer with thickness up to a few microns (thus named ''microlayer'') is formed 
between the wall and the liquid-vapor interface of the bubble. The microlayer is 
a desired feature in boiling-based equipment. It acts as a heat transfer bridge, 
allowing a heat flux in the order of MW/m2 to be transferred from the wall to 
the liquid-vapor interface, promoting an efficient cooling of the wall. This 
results in the microlayer evaporation and its contribution to the overall bubble 
growth can be  up to 50%. The mechanism of microlayer formation, dry-spot 
dynamics and the related near-wall heat transfer phenomena are therefore an 
active research topic within the boiling community.         

Experiments performed in order to measure near-wall parameters, such as 
microlayer thickness and the dry spot size, are vital to validate novel physical 
models developed at CEA, in particular at STMF the ones implemented in the 
numerical simulations with TrioCFD. At STMF, a novel experimental installation 
has been developed in the framework of a PhD thesis to study the near-wall 
phenomena in boiling. The experimental setup uses advanced high-speed and high-
resolution optical diagnostics (white light interferometry, infrared 
thermography and shadowgraphy) to measure microlayer thickness, wall temperature 
distribution and macroscopic bubble shape. The installation is, therefore, able 
to fully characterize the near-wall phenomena and provide data for the 
validation of numerical simulations.    
 
The postdoctoral researcher will benefit from this experimental installation to 
perform experiments in a variety of conditions of input power and subcooling to 
study the physical phenomena related to the microlayer 
dynamics, heat transfer and dry-spot at bubble growth in nucleate boiling. 

The expertize on high speed and high resolution optical measurements 
(interferometry, infrared thermography) and on image post-processing using 
matlab are required. Experience in performing experiments on thermal 
sciences/fluid mechanics is mandatory.