in MATLAB PDE Toolbox App, I've multiple objects (Rectangular shaped) in one file. For multiple objects I'd like to specify the PDE coefficients differently. How can I specify the different PDE coefficients for different objects.

As an example, I have 3 rectangular shaped objects. They share the boundary with each other. I'd like to calculate the heat transfer equation for 3 different objects. The heat source,Q is different for different objects e.g Q = [10;20;30]. So using PDE Toolbox GUI, how can I set the value ?

Answer 1

[Alan Weiss]

After you have drawn your rectangles, select PDE > PDE Mode. Then double-click each rectangle to enter its coefficients.

Alan Weiss

MATLAB mathematical toolbox documentation

[Md Shahidul Alam]

Thank you Mr. Weiss, it works.

Answer 2

[Md Shahidul Alam]

Additionally I've encountered another 3 problem.

1. What is the difference between Convection heat transfer coefficient(h) and heat transfer coefficient(q)? I know Convection heat transfer coefficient( htc ) but not sure about heat transfer coefficient. Is it the overall htc of the object?

2. In BC parameters, what is weight(h) and temperature(r)? Could you please provide any theoretical reference related with these?

3. What is the difference between Heat source(Q) and heat flux (g)? As far as I've figured out the unit for heat source(Q) is Watt and for heat flux is W/m^2. Am I right?

[Alan Weiss]

The equation that the PDE Toolbox solves is displayed above the coefficients in the PDE Specification dialog box:

 -div(K*grad(T)) = Q + h*(Text - T)

where T = temperature, k = coeff. of heat conduction, Q = heat source, h = convective heat transfer coeff., and Text = external temperature.

In the Boundary Condition dialog box, the Neumann boundary conditions are

 n*k*grad(T) + q*T = g

where g = heat flux and q = heat transfer coefficient.

In summary, Q is a coefficient of the PDE, and g is a Neumann boundary condition term.

Alan Weiss

MATLAB mathematical toolbox documentation