Hello Minh Vuong
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Posted:
1 decade ago
Jan 27, 2011, 3:46 a.m. EST
Hi,
you might look at this example describing natural convection cooling of a thermos under laminar flow :
www.comsol.com/showroom/gallery/1448/
Another solution might be to use the Convective Cooling feature of the Heat Transfer package, and then to specifiy an user-defined heat transfer coefficient. In the model "power_transistor" of v4.0a, COMSOL used h=5 W/m^2.K. I thought it was more like 50, but who knows...
Note that if you have a simple object (convex shape, such as a cube) with one of its faces is at a fixed temperature, and a moderate heat source, the boundary conditions at the other faces is of little importance. For instance, using h=5-50 W/m^2.K or even the Outflow option doesn't change much the maximum temperature nor the gradient.
Hi,
you might look at this example describing natural convection cooling of a thermos under laminar flow :
http://www.comsol.com/showroom/gallery/1448/
Another solution might be to use the Convective Cooling feature of the Heat Transfer package, and then to specifiy an user-defined heat transfer coefficient. In the model "power_transistor" of v4.0a, COMSOL used h=5 W/m^2.K. I thought it was more like 50, but who knows...
Note that if you have a simple object (convex shape, such as a cube) with one of its faces is at a fixed temperature, and a moderate heat source, the boundary conditions at the other faces is of little importance. For instance, using h=5-50 W/m^2.K or even the Outflow option doesn't change much the maximum temperature nor the gradient.
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Posted:
1 decade ago
Jan 27, 2011, 3:54 a.m. EST
Hi,
I think the predominant heat transfer mechanisms at room temperature are radiation and convection. Air is quite a good thermal insulator, so conduction losses are low.
Best regards
Edgar
Hi,
I think the predominant heat transfer mechanisms at room temperature are radiation and convection. Air is quite a good thermal insulator, so conduction losses are low.
Best regards
Edgar
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Posted:
1 decade ago
Dec 23, 2011, 3:41 a.m. EST
Hi,
create the air cube a little bit bigger that object. Define cube domain as infinite element (general or something that similar). Define convective cooling in every outer cube boundary, at free convection h about 5-25 W/m²K (h depens on deltaT (air and outer temperature of object), charakterisitc length and air properties)
regards
akmal
Hi,
create the air cube a little bit bigger that object. Define cube domain as infinite element (general or something that similar). Define convective cooling in every outer cube boundary, at free convection h about 5-25 W/m²K (h depens on deltaT (air and outer temperature of object), charakterisitc length and air properties)
regards
akmal
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Posted:
1 decade ago
Nov 11, 2013, 3:23 p.m. EST
Hi there,
I am trying to do the same thing, but my air cube is around imported geometry from AutoCAD (3D). The problem I am having is that once I create the air cube around my imported geometry, the imported geometry seems to disappear (it becomes unselectable and invisible) and I can no longer assign it a material property. I definitely don't have it hidden, and I've used the same imported geometry to run a heat loss analysis before and that worked fine.
Any ideas?
Thank you
Hi there,
I am trying to do the same thing, but my air cube is around imported geometry from AutoCAD (3D). The problem I am having is that once I create the air cube around my imported geometry, the imported geometry seems to disappear (it becomes unselectable and invisible) and I can no longer assign it a material property. I definitely don't have it hidden, and I've used the same imported geometry to run a heat loss analysis before and that worked fine.
Any ideas?
Thank you