Heat and Mass Transfer - finding surface temp

In summary, the conversation discusses calculating the temperature of a wire conducting electricity with given values for resistance, diameter, temperature, emissivity, and heat transfer coefficients. The approach of breaking the equation into two separate equations is questioned and it is suggested to solve the equation numerically or compare the magnitudes of convective and radiative heat transfer.
  • #1
Boom100
4
0

Homework Statement


A wire is conducting electricity, given values of :

R' = .4 ohms/m D = .002 m Tinf=300k Tsur=300k k=380W/m*C

emissivity = 1 h=10W/m^2*C Ts = Find this sigma=Stefan boltzmann

Plot the Temperature of the wire versus the current I for 0<I<10 amps.


Homework Equations



P = I^2*R' = q'

Convective heat = h(Ts-Tinf) + sigma(Ts^4-Tsur^4) = I^2*R' / pi*D = q'/pi*D = q''

The Attempt at a Solution



Ok So my attempt as essentially to break down the equation I have set to convective heat. After breaking things up and solving for Ts, I found :

"(I^2*R' / pi*D) + (h*Tinf) + (sigma*(Tsur)^4)" = Ts(h+sigma*(Ts)^3)

**Ill use " ... " for the left hand side of the equation

So my attempt was to break into into two equations:

"..." = Ts and Ts = Cubed Root ( ("..." - h)/sigma)

For some reason whenever I go to solve for Ts, I get pretty absurd numbers.

Using Kelvin I get 3932 K for I=0
I don't even think I can use celsius here because of the stefan boltzman constant (My equations are not temperature differences).

Where am I going wrong and is this approach even possible?
 
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  • #2
Where are you getting the approach of "break[ing it] into...two equations"? Like if A = BC, then A = B and A = C? That doesn't make sense to me.

How about solving the equation numerically, or calculating the magnitudes of the convective and radiative heat transfer and seeing if one dominates over the other?
 

1. What is the difference between heat and mass transfer?

Heat transfer is the movement of thermal energy from a hotter object to a cooler object, while mass transfer is the movement of mass or particles from one location to another. In heat transfer, the temperature difference between the two objects causes the energy transfer, while in mass transfer, the concentration difference of the particles drives the transfer.

2. How is surface temperature calculated in heat and mass transfer?

In heat and mass transfer, surface temperature is calculated using the convection heat transfer coefficient, the fluid temperature, and the surface area. This can be done using equations such as Newton's Law of Cooling or the Nusselt number equation.

3. What factors affect heat and mass transfer?

There are several factors that can affect heat and mass transfer, such as temperature difference, surface area, fluid properties, and flow rate. Other factors include the type of material, surface roughness, and the presence of any barriers or obstructions.

4. How does convection impact heat and mass transfer?

Convection is the transfer of heat through the movement of a fluid (liquid or gas). It can significantly impact heat and mass transfer by altering the temperature and flow patterns of the fluid. The convective heat transfer coefficient is also an important factor in calculating surface temperature.

5. What are some real-world applications of heat and mass transfer?

Heat and mass transfer have a wide range of applications in various industries, including thermal management in electronics, cooling systems in cars and buildings, food preservation, and chemical processing. It also plays a crucial role in natural phenomena such as weather patterns, ocean currents, and the Earth's climate.

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