Using Solve Block to solve a Fourier's Law for Furnace

[ptc-4516337]

I have an assignment where I need to solve the steady-state rate of heat transfer through multiple layers of a Furnace wall with Fourier's Law. I am supposed to use solve block once to solve the entire problem, but I am having trouble because Mathcad keeps telling me that I have an undefined variable and I am not understanding what I am doing wrong. Below is the image of the furnace and I attached what I tried so far. Thank you for your help.

[ValeryOchkov]

One same problem on Mathcad Server:

http://twt.mpei.ac.ru/MCS/Worksheets/Thermal/T-T-2-Chapter-3-3-3-1.xmcd

[ValeryOchkov]

See please in attach thermal conductivities as functions of temperature.

[Fred_Kohlhepp]

need to find temperatures to balance

[ValeryOchkov]

Sorry Fred!

In attach your file, but more correct!

[ValeryOchkov]

Do you know: we can have one expression as two equations in the Given-find Block:

[ValeryOchkov]

For nonlinear (common view) functions of thermal conductivity(T):

[ValeryOchkov]

See too http://twt.mpei.ac.ru/MCS/Worksheets/Thermal/Heat-Flow-1a.xmcd

and the picture:

[ValeryOchkov]

Sorry - the correct solution is below and in attach:

[ValeryOchkov]

Sorry again!

It was very interesting my error with work with units!

The unit of Thermal conductivity is not W/(m K) but W * m / (m^2 K) and we can not simplify it to W/(m K).

It will be good to have in Mathcad two or more same units for different physical quantity with same units.

For example we have in Thermal conductivity two meter but the first meter W * m / (m^2 K) is an unit of lenth and second one is an unit of square root of surface W * m / (m^2 K).

Second example.

I have in my Mathcad Server calculation of the binar thermal cycle

http://twt.mpei.ac.ru/MCS/Worksheets/PTU/PGU-eng.xmcd

two unit of mass kg. But the first one is mass of water and second one - mass of gas!

[ValeryOchkov]

brandon raines wrote:

I have an assignment where I need to solve the steady-state rate of heat transfer through multiple layers of a Furnace wall with Fourier's Law. I am supposed to use solve block once to solve the entire problem, but I am having trouble because Mathcad keeps telling me that I have an undefined variable and I am not understanding what I am doing wrong. Below is the image of the furnace and I attached what I tried so far. Thank you for your help.

This problem on Mathcad Server

http://twt.mpei.ac.ru/MCS/Worksheets/Thermal/Heat-Flow-3layers.xmcd

[ValeryOchkov]

Same problem but not for the plate - for the tube:

http://twt.mpei.ac.ru/MCS/Worksheets/Thermal/Heat-Flow-3radius.xmcd