Mode of heat transfer between two cubes and to its surroundings
Mode of heat transfer between two cubes and to its surroundings
(OP)
Hi all,
I am trying to mathematically proof that one can neglect convection and radiation when two cubes (paraffin-based, 1x1x1cm) are in direct contact on one side whilst the other 5 sides are perfectly insulated. Any ideas on how to calculate the Nusselt number here?
How do you justify that radiation can be neglected? Can they actually be neglected?
How would the mode of heat transfer be changed if the cubes were not perfectly insulated, but instead were surrounded by air?
It would be fantastic if anyone could give me any hint! Many warm wishes and thanks so much in advance!
I am trying to mathematically proof that one can neglect convection and radiation when two cubes (paraffin-based, 1x1x1cm) are in direct contact on one side whilst the other 5 sides are perfectly insulated. Any ideas on how to calculate the Nusselt number here?
How do you justify that radiation can be neglected? Can they actually be neglected?
How would the mode of heat transfer be changed if the cubes were not perfectly insulated, but instead were surrounded by air?
It would be fantastic if anyone could give me any hint! Many warm wishes and thanks so much in advance!





RE: Mode of heat transfer between two cubes and to its surroundings
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RE: Mode of heat transfer between two cubes and to its surroundings
How could I mathematically (with a formula) explain that convection does not play a role here?
I am trying to determine whether heat radiates from the hot paraffin cube (ca. 100°C) to the other cube or to the surrounding air and whether it is significant with regards to conduction?
Does this answer your question? Thanks again so much for your help!
RE: Mode of heat transfer between two cubes and to its surroundings
There are equations for convection, based on Raleigh and Nusselt numbers; when graphed as a function of separation, the convection coefficient is inversely proportional to the Rayleigh number. At some separation, however, I think the standard equations break down, since it becomes strictly conduction, rather than convection. You'll need to consult someone or some book that is better versed in convection in small gaps.
> I am trying to determine whether heat radiates from the hot paraffin cube (ca. 100°C) to the other cube or to the surrounding air and whether it is significant with regards to conduction?
You'll have to do the numbers, but given that paraffin is essentially a thermal insulator, conduction and radiation are probably comparable. You are just going to have to create a model that can given you a live estimate of what's going on.
TTFN

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RE: Mode of heat transfer between two cubes and to its surroundings
RE: Mode of heat transfer between two cubes and to its surroundings
TTFN

FAQ731-376: Eng-Tips.com Forum Policies
Need help writing a question or understanding a reply? forum1529: Translation Assistance for Engineers