Heat disipation required to keep below a temp threshold

In summary, the microprocessor needs to dissipate 100W of heat to maintain a temperature below 60°C, and the specific heat transfer coefficient depends on the shape and conditions of the surface. In order to dissipate the heat effectively, heat sinks and fans are used to increase the surface area and the convective heat transfer coefficient.
  • #1
CraigH
222
1
This question is easier to explain with an example.

A silicon microprocessor consumes 100W of real power. If the surrounding air has a temperature of 22°C, and the temperature of the microprocessor must stay below 60°C, how much heat must the microprocessor dissipate?

This isn’t a homework or coursework question. I just want to know the formulas and relationships involved.

Thanks!
 
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  • #2
CraigH said:
This question is easier to explain with an example.

A silicon microprocessor consumes 100W of real power. If the surrounding air has a temperature of 22°C, and the temperature of the microprocessor must stay below 60°C, how much heat must the microprocessor dissipate?

This isn’t a homework or coursework question. I just want to know the formulas and relationships involved.

Thanks!

Seems like in the steady state, it would have to dissipate all 100W to keep from heating up more...

A more precise question would be what the thermal resistance θja would have to be to keep the IC junction temperature below 60C. Do you know how to calculate that?
 
  • #3
berkeman said:
Seems like in the steady state, it would have to dissipate all 100W to keep from heating up more...

Ahh of course. Thanks. I'm going to delete this question and ask a better one in the morning.
 
  • #4
CraigH said:
Ahh of course. Thanks. I'm going to delete this question and ask a better one in the morning.

No, please don't delete or alter your OP. That is against the PF rules. Just add your new question later here, or you could start a new thread if the question is different enough. :-)
 
  • #5
CraigH said:
A silicon microprocessor consumes 100W of real power. If the surrounding air has a temperature of 22°C, and the temperature of the microprocessor must stay below 60°C, how much heat must the microprocessor dissipate?

You probably want to ask how much heat should it dissipate if it has to stay below 60°C for a certain amount of time.
 
  • #6
As berkeman pointed out, the heat that the processor has to dissipate is 100W. Due to the temperatures involved, almost all the heat transfer will be through convection:

Q=hc·A·ΔT

You know the power you have to dissipate (Q). Depending on the conditions (mainly the shape and position of the surface and whether it is induced or forced convection) you can estimate the convective heat transfer coefficient (hc).

If the heat is directly dissipated through the microprocessor's surface, and we can consider it to be at 60°C, we would already know the difference of temperatures, therefore we could calculate the required surface you need (A) in order to get rid of the heat.

But I'm afraid you will get a much bigger surface than the microprocessor's, that's why they put heat sinks (the aluminium plates with fins) so there is a much bigger surface. And also they put fans on top of that: forced conductivity with a significant air velocity through the fins means the convective heat transfer coefficient (hc) is much higher.
 

What is heat dissipation and why is it important?

Heat dissipation is the process of transferring heat from one object to another or from one location to another. It is important because excessive heat buildup can damage equipment and cause safety hazards.

How does temperature affect the need for heat dissipation?

Temperature plays a crucial role in the need for heat dissipation. As the temperature increases, so does the amount of heat that needs to be dissipated in order to maintain a safe operating temperature.

What factors determine the amount of heat dissipation required to keep below a temperature threshold?

The amount of heat dissipation required depends on several factors, including the ambient temperature, the heat generated by the object or system, and the efficiency of the cooling system.

What are some common methods of heat dissipation?

Some common methods of heat dissipation include conduction, convection, and radiation. Conduction involves the transfer of heat through direct contact, convection involves the movement of heat through a fluid, and radiation involves the emission of heat in the form of electromagnetic waves.

How can I calculate the amount of heat dissipation required for a specific temperature threshold?

The amount of heat dissipation required can be calculated by using the formula Q = mcΔT, where Q is the amount of heat, m is the mass of the object, c is the specific heat capacity, and ΔT is the change in temperature. This calculation can help determine the necessary cooling capacity for a system to maintain a specific temperature threshold.

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