Executive Summary : | Most of the existing research is directed towards boiling in short microchannels for cooling electronics components. There is very limited number of experimental studies available on flow boiling in microchannels at operating conditions relevant to fuel cells applications. So, there is need of studying boiling in long or serpentine microchannels.
It is very clear from the literature that till now very few experimental/numerical studies of flow boiling of ethanol-water binary mixture in mini/microchannels has been proposed in the open literature. Thus, the fundamental underlying principles of this phenomena has not been explored explicitly. Here we propose to carry out both experimental as well numerical study of flow boiling of ethanol-water binary mixture in mini microchannels from the perspective of conjugate heat transfer. In this work the channel substrate material, substrate thickness will be varied to understand its effect on flow boiling phenomena.
Secondly, guarding the system against flow instabilities will be of utmost importance while design and development of the experimental test rig. Instabilities in phase change flow boiling refer to the hydraulic and thermal oscillations that are induced for many known and unknown reasons. Considering that instabilities are undesirable for several reasons, different means of reducing instabilities through experimental validation will be proposed by suitable modification in the channel or header in/outlet.
It is proposed to study numerically and experimentally the flow boiling phenomena of ethanol-water binary mixture. Thus, it is proposed to setup an experimental test rig for this purpose where the test section will be designed such that different mini/microchannel substrate can be placed as per requirement. Different material such as Al, Cu, and steel will be used as the substrate material to understand the effect of conjugate heat transfer on the flow boiling phenomena. Pure water, pure ethanol, and mixture of ethanol-water at different compositions to be used as the working fluid.
The objectives of this proposed experimental study are as follows:
To design and develop an experimental test rig for flow boiling study.
To fabricate mini/microchannels of different substrate material and substrate thickness.
To study thermo-hydraulic characteristics during flow boiling of ethanol-water binary mixture.
Secondly, numerical study will also be carried out simultaneously to predict the thermal condition at the solid-fluid condition correctly and understand the conjugate effects on flow boiling phenomena in mini/microchannels.
The objectives of this proposed numerical study are as follows:
To develop/apply suitable model for predicting flow boiling of pure fluids/ binary mixtures of ethanol-water.
To analyse the conjugate effect on flow boiling phenomena by varying substrate material and substrate thickness. |