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Modeling aluminum plate heating

Posted Nov 13, 2012, 3:58 a.m. EST Heat Transfer & Phase Change, Mesh, Modeling Tools & Definitions, Parameters, Variables, & Functions Version 4.2a 3 Replies

Juan Jesus Gallardo
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Hi.

I am lost and need some help.

I need to modeling the following case: The heating suffer by an aluminum plate that it is illuminated by a lamp formed by a matrix of 7x7 leds with a total power of 49 watts. The distance between the lamp and the plate is 20 cm.

How can I do it?

What physics are involved?

Do I need to model all leds or only assume that I have one led with the total power?

What about the boundary conditions?

Please, help me!!

Thank you
3 Replies Last Post Nov 15, 2012, 1:03 p.m. EST
Nagi Elabbasi Facebook Reality Labs
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Posted: 1 decade ago Nov 13, 2012, 9:57 a.m. EST
Hi Juan,

There are different ways to model this LED-plate heating problem with varying complexity. The heat transfer from the LEDs to the Aluminum plate will be through conduction, convection and radiation with the relative contribution of each dependent on the geometries and temperatures involved.

You will have to decide whether to explicitly model convection through the air or use appropriate convection boundary conditions instead. Similarly, regarding radiation you will have to choose between modeling surface-to-surface radiation between the LEDs and plate, or using approximate expressions instead.

I would start by modeling one “distributed” LED heat source that covers the 7x7 area instead of the individual LEDs.

Nagi Elabbasi
Veryst Engineering
Hi Juan, There are different ways to model this LED-plate heating problem with varying complexity. The heat transfer from the LEDs to the Aluminum plate will be through conduction, convection and radiation with the relative contribution of each dependent on the geometries and temperatures involved. You will have to decide whether to explicitly model convection through the air or use appropriate convection boundary conditions instead. Similarly, regarding radiation you will have to choose between modeling surface-to-surface radiation between the LEDs and plate, or using approximate expressions instead. I would start by modeling one “distributed” LED heat source that covers the 7x7 area instead of the individual LEDs. Nagi Elabbasi Veryst Engineering
Juan Jesus Gallardo
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Posted: 1 decade ago Nov 15, 2012, 6:26 a.m. EST

Hi Juan,

There are different ways to model this LED-plate heating problem with varying complexity. The heat transfer from the LEDs to the Aluminum plate will be through conduction, convection and radiation with the relative contribution of each dependent on the geometries and temperatures involved.

You will have to decide whether to explicitly model convection through the air or use appropriate convection boundary conditions instead. Similarly, regarding radiation you will have to choose between modeling surface-to-surface radiation between the LEDs and plate, or using approximate expressions instead.

I would start by modeling one “distributed” LED heat source that covers the 7x7 area instead of the individual LEDs.

Nagi Elabbasi
Veryst Engineering


Hi, Nagi.

Thank you so much for your answer.

I have more doubts about this model.

Do I need to draw the lamp and setting all paremeters (geometry, materials,...) or I can "say" that the aluminum plate is heated by a lamp of 49 watts (for example) like one of the physics?

I am graduate in chemistry and not engineer. This is the reason why I ask lot of things.

Thanks again.

Regards.
[QUOTE] Hi Juan, There are different ways to model this LED-plate heating problem with varying complexity. The heat transfer from the LEDs to the Aluminum plate will be through conduction, convection and radiation with the relative contribution of each dependent on the geometries and temperatures involved. You will have to decide whether to explicitly model convection through the air or use appropriate convection boundary conditions instead. Similarly, regarding radiation you will have to choose between modeling surface-to-surface radiation between the LEDs and plate, or using approximate expressions instead. I would start by modeling one “distributed” LED heat source that covers the 7x7 area instead of the individual LEDs. Nagi Elabbasi Veryst Engineering [/QUOTE] Hi, Nagi. Thank you so much for your answer. I have more doubts about this model. Do I need to draw the lamp and setting all paremeters (geometry, materials,...) or I can "say" that the aluminum plate is heated by a lamp of 49 watts (for example) like one of the physics? I am graduate in chemistry and not engineer. This is the reason why I ask lot of things. Thanks again. Regards.
Nagi Elabbasi Facebook Reality Labs
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Posted: 1 decade ago Nov 15, 2012, 1:03 p.m. EST
Hi Juan,

I didn’t mean to give you doubts about the model. It is certainly doable but not trivial. You need more than just the amount of power generated at the lamps. You need the outer surface temperature of the lamps. If you have that measured then you will not need to model the lamp geometry in details.

As I mentioned earlier, depending on the geometry and temperatures you may find that one heat transfer mode dominates. If, for example, radiation is the dominant source then you can develop a model that only captures radiation, etc. When it comes to the plate you need proper boundary conditions that capture how the heat will escape from there.

Nagi Elabbasi
Veryst Engineering
Hi Juan, I didn’t mean to give you doubts about the model. It is certainly doable but not trivial. You need more than just the amount of power generated at the lamps. You need the outer surface temperature of the lamps. If you have that measured then you will not need to model the lamp geometry in details. As I mentioned earlier, depending on the geometry and temperatures you may find that one heat transfer mode dominates. If, for example, radiation is the dominant source then you can develop a model that only captures radiation, etc. When it comes to the plate you need proper boundary conditions that capture how the heat will escape from there. Nagi Elabbasi Veryst Engineering

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