A New Method for Estimating Bubble Diameter At Different Gravity Levels for Nucleate Pool Boiling

Nucleate boiling has significant applications in earth gravity( in industrial cooling applications) and micro-gravity conditions (in space exploration, specifically in making space applications more compact). However, the effect of gravity on the growth rate and bubble size is not yet well understood. We perform numerical simulations of nucleate boiling using an adaptive Moment-of-Fluid (MoF) method for a single vapor bubble (water or Perfluoro-n-hexane) in saturated liquid for different gravity levels. Results concerning the growth rate of the bubble, specifically the departure diameter and departure time have been provided. The MoF method has been first validated by comparing results with a theoretical solution of vapor bubble growth in super-heated liquid without any heat-transfer from the wall. Next, bubble growth rate, bubble shape and heat transfer results under earth gravity, reduced gravity and micro-gravity conditions are reported and they are in good agreement with experiments. Finally, a new method is proposed for estimating the bubble diameter at different gravity levels. This method is based on an analysis of empirical data at different gravity values and using power-series curve fitting to obtain a generalized bubble growth curve irrespective of the gravity value. This method is shown to provide a good estimate of the bubble diameter for a specific gravity value and time.

CHARACTERIZING DUAL MATRIX COMPOSITE ORIGAMI DEPLOYMENT

Lightweight strain-energy deployable structures are well suited for applications in spacecraft structures and deployable habitats. Dual matrix composite origami describes a composite structure that utilizes two uniquely different matrix systems in the same fiber structure. An epoxy matrix is used to form rigid sections and a silicone matrix creates bending regions where one can create a collapsible structure. The added elastic properties of the silicone matrix allow the composite to harness internal strain-energy to spring open from a folded configuration to a flat plane. This is advantageous for solar arrays as they can be folded for compact transit and then return to a flat surface after being deployed. In this work, initial ground testing is used to verify repeatable deployment prior to micro gravity flight testing. To characterize the motion of the composite structures as they deploy, OptiTrack Flex 13 cameras are used in sync with a deployment mechanism that repeatably releases and tracks the origami structures. The data collected in this study will be used to validate the use of the flight rig, deployment mechanism, and motion tracking system for future micro gravity flight testing. Once tested and characterized in a micro gravity setting, the dual matrix composite origami structures developed in this work can be applied to large solar arrays to power next generation spacecraft and satellites with lower complexity compared to other deployable technology.

Effect of micro vibration from two space platform on liquid mixture during thermodiffusion experiment

In the present study, a two-dimensional numerical simulation was carried out for binary mixture. The influence of micro gravity vibration or acceleration on board Iinternational Space Station and FOTON-M3, influence of different cavities size as well as the effect of the sign of the Soret coefficient (fluid flow, heat and mass transfer and concentration) in the solvent were investigated in detail. It must be noted that based on previous experiences with this investigation using the same mixture and cavity by Saghir and Parsa [

Effect of micro vibration from two space platform on liquid mixture during thermodiffusion experiment

In the present study, a two-dimensional numerical simulation was carried out for binary mixture. The influence of micro gravity vibration or acceleration on board Iinternational Space Station and FOTON-M3, influence of different cavities size as well as the effect of the sign of the Soret coefficient (fluid flow, heat and mass transfer and concentration) in the solvent were investigated in detail. It must be noted that based on previous experiences with this investigation using the same mixture and cavity by Saghir and Parsa [