TWO-PHASE FLOW EXPERIMENTAL STUDY: INFLUENCE OF GRAVITY LEVEL ON LOCAL BOILING HEAT TRANSFER INSIDE A MINICHANNEL

Flow boiling in minichannels is the most complex convective phase change process. Indeed, there are a lot of physical parameters that influence the two-phase flow during boiling. Here, we will focus on the influence of one of this factor: the gravity level. Actually, there are not many mechanisms that have been proposed for the role of this bound on boiling phenomena. In fact, there is not complete agreement on the importance of gravity on heat and mass transfers with phase change because there is a lack of experimental data at this small scale and because reproducing different gravity levels during parabolic flights has a cost. In this line, the goal of this work is to obtain benchmark data on the local heat transfer coefficient in a minichannel during hyper and microgravity. We want to acquire a better knowledge of the elementary phenomena which control the heat and mass transfers during convective boiling. Indeed, boiling in microscale geometry is a very efficient mode of heat transfer since high heat and mass transfer coefficients are achieved. Actually, minichannels and microchannels are widely used in industry and they are already attractive in many domains such as design of compact evaporators and heat exchangers. They provide an effective method of fluid movement and they have large heat dissipation capabilities. In these situations, their compact size and heat transfer abilities are unrivalled. In this communication, the objective is to acquire better knowledge of the conditions that influence the two-phase flow under microgravity. The expected results will contribute to the development of microgravity models. To perform these investigations, we used an experimental data coupling with an inverse method based on BEM (Boundary Element Method). This non intrusive approach allows us to solve a 3D multi domain IHCP (Inverse Heat Conduction Problem). With this analysis, we are able to quantify the local heat flux, the local temperature and the local heat transfer coefficient in a minichannel (254 mu m) by inversing thermocouples data without disturbing the established flow.