Max Wire Temp: Calculating Equilibrium

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    Max Temperature Wire
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SUMMARY

The discussion focuses on calculating the equilibrium temperature of a wire connected to a power supply, considering factors such as electrical power input, heat dissipation through convection and radiation, and the wire's resistance. The equation R(T) = R(1 + aT) is used to describe the wire's resistance as a function of temperature. Participants suggest setting the heating power equal to the power loss to the environment to solve for the equilibrium temperature, emphasizing the need for numerical methods due to the complexity of heat transfer dynamics. The impact of convection and the wire's orientation in the environment is also highlighted as critical for accurate calculations.

PREREQUISITES
  • Understanding of electrical resistance and temperature dependence (R(T) = R(1 + aT))
  • Familiarity with heat transfer concepts, including convection and radiation
  • Knowledge of electromagnetic radiation principles (P = eσ(T^4 - T0^4))
  • Basic numerical methods for solving equations
NEXT STEPS
  • Research numerical methods for solving nonlinear equations in thermal dynamics
  • Learn about heat transfer coefficients for different environments and orientations
  • Study the Stefan-Boltzmann law and its application in thermal radiation calculations
  • Explore thermal conductivity properties of air and their impact on wire heating
USEFUL FOR

Electrical engineers, thermal analysts, and anyone involved in the design and analysis of heating elements and thermal management systems.

abro
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Say I connect a wire to a power supply with a voltage V. The wire is a cilinder with a total surface area A, and resistance R. The wire will get hotter and hotter, and the temperature will increase linearly, according to the equation
R(T)=R(1+aT). It will give this heat off in the environment to heat up e.g. air molecules (P=λAdT/d ?, if so, what is d, assuming it reaches into infinity). And because the wire gets hotter, it will also emit electromagnetic radiation (P=eσ(T^4-T0^4 ?)
So here's my question, can we combine the electrical power input, together with the output factors such as internal and external heat and electromagnetic radiation to calculate the equilibrium temperature? Is there a formula for it? (I have seen a thread where it was derived when all the heat dissipitates through radiation)
 
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abro said:
So here's my question, can we combine the electrical power input, together with the output factors such as internal and external heat and electromagnetic radiation to calculate the equilibrium temperature?
Sure. Set heating power equal to power loss to the atmosphere, solve for T (probably numerically).
Regular thermal conductivity of air is often negligible, but you'll get convection. There are formulas to estimate its effect, but it depends on the environment of your cable (is it in free air? Horizontal, vertical, ...?).
 

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