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CVB: the Constrained Vapor Bubble Capillary Experiment on the International Space Station MARANGONI FLOW REGIONThe Constrained Vapor Bubble (CVB) is a wickless, grooved heat pipe and we report on a full- scale fluids experiment flown on the International Space Station (ISS). The CVB system consists of a relatively simple setup a quartz cuvette with sharp corners partially filled with either pentane or an ideal mixture of pentane and isohexane as the working fluids. Along with temperature and pressure measurements, the two-dimensional thickness profile of the menisci formed at the corners of the quartz cuvette was determined using the Light Microscopy Module (LMM). Even with the large, millimeter dimensions of the CVB, interfacial forces dominate in these exceedingly small Bond Number systems. The experiments were carried out at various power inputs. Although conceptually simple, the transport processes were found to be very complex with many different regions. At the heated end of the CVB, due to a high temperature gradient, we observed Marangoni flow at some power inputs. This region from the heated end to the central drop region is defined as a Marangoni dominated region. We present a simple analysis based on interfacial phenomena using only measurements from the ISS experiments that lead to a predictive equation for the thickness of the film near the heated end of the CVB. The average pressure gradient for flow in the film is assumed due to the measured capillary pressure at the two ends of the liquid film and that the pressure stress gradient due to cohesion self adjusts to a constant value over a distance L. The boundary conditions are the no slip condition at the wall interface and an interfacial shear stress at the liquid- vapor interface due to the Marangoni stress, which is due to the high temperature gradient. Although the heated end is extremely complex, since it includes three- dimensional variations in radiation, conduction, evaporation, condensation, fluid flow and interfacial forces, we find that using the above simplifying assumptions, a simple successful model can be developed.
Document ID
20150000890
Acquisition Source
Glenn Research Center
Document Type
Presentation
Authors
Wayner, Peter C., Jr. (Rensselaer Polytechnic Inst. Troy, NY, United States)
Kundan, Akshay (Rensselaer Polytechnic Inst. Troy, NY, United States)
Plawsky, Joel (Rensselaer Polytechnic Inst. Troy, NY, United States)
Date Acquired
January 30, 2015
Publication Date
October 22, 2014
Subject Category
Fluid Mechanics And Thermodynamics
Report/Patent Number
GRC-E-DAA-TN19372
Meeting Information
Meeting: American Society for Gravitational and Space Research Annual Meeting 2014
Location: Pasadena, CA
Country: United States
Start Date: October 22, 2014
End Date: October 26, 2014
Sponsors: American Society for Gravitational and Space Research
Funding Number(s)
WBS: WBS 904211.04.02.30.25
CONTRACT_GRANT: NNC08BA08B
CONTRACT_GRANT: NNX09AL98G
Distribution Limits
Public
Copyright
Public Use Permitted.
Keywords
heat pipes
microgravity
interfacial heat transfer
microscopy
fluid physics
capillarity

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