Case Studies

Constrained Vapor Bubble Control Box

February 2005 | Brook Park, OH Contributed by Justin L. Bail Mechanical Engineer Zin Technologies

Computational Fluid Dynamics is used to analyze airflow and thermal properties of a Constrained Vapor Bubble Control Box (a component to be used at the International Space Station). With these results, Zin engineers optimize cooling to achieve NASA's touch temperature limit of forty-nine degrees Celsius to protect astronauts.

The plot is created using iso-surfaces and Tecplot's Blanking tool. Streamlines and contours effectively communicate critical patterns such as circulation areas, dead spots, and maximum temperature and pressure locations. These properties help determine the best size and location for inlet holes which direct cool air to electrical components that are predicted to reach the highest temperatures. The simulations are modeled as worst-case situations.

The Engineer
Justin Bail is a Mechanical Engineer at Zin Technologies in Brook Park, Ohio. ZIN Technologies has over two-hundred scientists, engineers and technicians that provide integrated products and space flight hardware development services to NASA and other technology companies.

Fluids and Combustion Facility & the Constrained Vapor Bubble Control Box
NASA is developing a modular, multi-user experimentation facility for conducting fluid physics and combustion science experiments on the International Space Station (ISS). The Fluids and Combustion Facility (FCF) consists of a Fluids Integrated Rack and a Combustion Integrated Rack. These racks hold experiments that allow scientists to explore and better understand how zero-gravity effects combustion and other physical processes.

Bail's group is part of the project analysis team. They provide detailed analysis of the FCF's individual components as well as the entire system. They also perform thermal tests to validate their models. This enables engineers to reuse the models and sustain engineering once the facility is in Space.

Their current work is focused on developing a Constrained Vapor Bubble (CVB) Control Box. This device is part of the communications and power supply for the Fluids Integrated Rack. The Control Box supplies power to the Constrained Vapor Bubble Module, an experimental package placed inside the Light Microscopy Module.

A photo of the Fluids Integrated Rack with its doors open. The entire device will be flown into space and installed at the ISS. Inside you can see the the Light Microscopy Module and its supporting components. Also visible is the Optics Bench, a hollow box-like structure that provides structural support for the Light Microscopy Module. There is a large fan located at the top of the Optics Bench that pulls in air and circulates it throughout the rack. The CVB Control Box will be located in the upper right hand portion of the Optics Bench once completed. Bail's research has provided an optimal location for the Control Box's air inlet and the correct exit orifice size to achieve required pressure drops.

Simulation and Testing
Using a Computational Fluid Dynamics (CFD) code developed by Innovative Research, Inc, called COMPACT, Bail performs thermal analysis of the CVB Control Box. The three dimensional numerical analysis involves the simultaneous solution of momentum, conservation of mass, and energy equations. These computational results provide critical design information and produce substantial insight into physical processes.

The rigorous design method follows a regimented process typical of all space flight hardware. Numerical results are compared to physical testing to fulfill each design requirement, such as pressure drop across the entire package. "Tecplot’s ability to extract specific data from a solution made it easy to calculate the average pressure at the exit, compare it to test data, and finally, change it to our design target," Bail noted.

The two-dimensional plot shows flow velocity vectors around the electronics stack. On the right, a zoomed mesh view displays the resolution of the computational analysis.

Plotting and Data Visualization
Bail uses Tecplot to post-process his CFD results. His plots range from complex 3-D heat and mass transfer problems to simple graphs.

"Tecplot effectively communicates critical patterns such as circulation areas, dead spots and maximum temperature and pressure locations," Bail said. "We use the very descriptive visualizations in technical reports and presentations for design analysis and proposals."

When asked to list Tecplot’s three greatest strengths as it relates to his work, Bail started with the obvious. “The software is very user friendly,” he said.

Beyond ease-of-use, Bail cited Tecplot's add-ons, such as the CFD Analyzer, and the macro language, that enable him to automate and perform complex plotting tasks. Finally he added, "Tecplot has an exceptional technical support team."

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