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How to model ambient air for heat transfer
Posted Jan 6, 2017, 1:55 p.m. EST Version 5.2a 1 Reply
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Hi,
I am very new to using COMSOL. The first thing I am working on is a cylindrical metal wire encapsulated in a polymer jacket surround by ambient room temperature air. The metal wire is set to an initial temperature, and I want to model how quickly the polymer jacket heats up. But the polymer jacket is surrounded by room temperature air. How to I create an essentially infinite air surrounding this wire and jacket that will be acting as a cooling force that is moving convectively and not warming up like a solid. Right now I have an air boundary that is basically a cylinder twice the diameter of the polymer jacket and the outer boundary of the air cylinder is set as a boundary condition to be room temperature, but this is obviously not a real world scenario, and I'm not sure my assumption of the air cylinder being twice the diameter of the polymer jacket is a good assumption, as when I change it to 3 of 4 times the diameter I get pretty different results. I assume there is a very easy setting I'm not aware of to just surround this wire and jacket with air that is essentially supplying convective cooling.
Thanks,
Josh
I am very new to using COMSOL. The first thing I am working on is a cylindrical metal wire encapsulated in a polymer jacket surround by ambient room temperature air. The metal wire is set to an initial temperature, and I want to model how quickly the polymer jacket heats up. But the polymer jacket is surrounded by room temperature air. How to I create an essentially infinite air surrounding this wire and jacket that will be acting as a cooling force that is moving convectively and not warming up like a solid. Right now I have an air boundary that is basically a cylinder twice the diameter of the polymer jacket and the outer boundary of the air cylinder is set as a boundary condition to be room temperature, but this is obviously not a real world scenario, and I'm not sure my assumption of the air cylinder being twice the diameter of the polymer jacket is a good assumption, as when I change it to 3 of 4 times the diameter I get pretty different results. I assume there is a very easy setting I'm not aware of to just surround this wire and jacket with air that is essentially supplying convective cooling.
Thanks,
Josh
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1 Reply Last Post Jan 6, 2017, 6:11 p.m. EST
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Posted:
8 years ago
At jacket outer boundary you can impose convective cooling boundary with heat transfer coefficient around 20 W/m^2/K. Another approach is to add laminar fluid flow for surrounding air and heat transfer in fluid for air. Impose the outer boundaries of air domain as open boundary in both heat transfer and fluid flow. For air convection due to bouncy, add gravity factor in fluid flow node.