natural convection boundary condition

thomasyangfly · June 22, 2012, 13:14

Hello all dear,

I am doing the cooling problem of a block of liquid aluminum filled in container. I want to see how long it takes to cool down the liquid to solid with natural convection thermal boundary condition. However, unfortunately, I cannot find how to set the thermal boundary condition as natural convection.

Please help me. Thanks a lot!

dmilano · June 22, 2012, 15:19

You can set the heat transfer coefficient in the "surface properties" section of the tree on the M&G tab. If you leave the heat transfer coefficient =-1 the code will estimate what the HTC should be based on correlations. You can also estimate what the HTC is from a correlation and input this directly. Finally, you can assume that the HTC is very large and that conduction in the fluid is the controlling parameter. To use this assumption, just put in a large value for the HTC but you'll need to make sure that the assumption is physically valid.

thomasyangfly · August 24, 2012, 03:38

Thank you very much for the kindly help.

stefmascio · September 11, 2012, 11:14

you will also have to switch on the density evaluation model (and setting a thermal expansion coefficient) if you want to see convective motions inside the water.

June 22, 2012, 13:14	natural convection boundary condition	#1
thomasyangfly New Member Xiaohu Yang Join Date: Sep 2011 Posts: 5 Rep Power: 15	Hello all dear, I am doing the cooling problem of a block of liquid aluminum filled in container. I want to see how long it takes to cool down the liquid to solid with natural convection thermal boundary condition. However, unfortunately, I cannot find how to set the thermal boundary condition as natural convection. Please help me. Thanks a lot!

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June 22, 2012, 15:19		#2
dmilano Member Join Date: Mar 2012 Posts: 72 Rep Power: 14	You can set the heat transfer coefficient in the "surface properties" section of the tree on the M&G tab. If you leave the heat transfer coefficient =-1 the code will estimate what the HTC should be based on correlations. You can also estimate what the HTC is from a correlation and input this directly. Finally, you can assume that the HTC is very large and that conduction in the fluid is the controlling parameter. To use this assumption, just put in a large value for the HTC but you'll need to make sure that the assumption is physically valid.

August 24, 2012, 03:38		#3
thomasyangfly New Member Xiaohu Yang Join Date: Sep 2011 Posts: 5 Rep Power: 15	Thank you very much for the kindly help.

September 11, 2012, 11:14		#4
stefmascio Member Stefano Join Date: Mar 2009 Posts: 59 Rep Power: 17	you will also have to switch on the density evaluation model (and setting a thermal expansion coefficient) if you want to see convective motions inside the water.