Heat Transfer Model Verification Tests

Stationary Tests	Test Result Inspection
Transient Tests	References

This notebook contains tests that verify that the heat transfer partial differential equations (PDE) model works as expected. To run all tests, SelectAll and press Shift+Enter. The results will then be in the section Test Result Inspection.

Note that these tests can also serve as a basis for developing your own heat transfer models. As such, the tests are grouped into stationary (time-independent) and transient (time-dependent) tests. In both categories, one- and two-dimensional tests can be found.

In each test case the visualization section is there to provide post-processing results for inspection, however, it is not a necessary part of the test. In the interest of saving runtime and reducing memory consumption the cells in the visualization section are set to not be evaluatable. To make these cells evaluatable, select the cells in question and choose Cell ▶ Cell Properties and make sure "Evaluatable" is ticked.

The heat equation is used to solve for the temperature field in a heat transfer model. Please refer to the information provided in "Heat Transfer" for more general theoretical background for heat transfer analysis.

Additionally define the axisymmetric heat transfer model representation function:

To avoid keeping memory intensive previous results set the history length to 0:

Stationary Tests

This section contains examples of stationary (non-time-dependent) heat transfer PDE models for the validation.

2D Single Equation

This section contains examples of 2D stationary heat transfer PDE model with one equation.

HeatTransfer-FEM-Stationary-2D-Single-HeatTransfer-0001

The following test case demonstrates a 2D stationary thermal analysis. The model domain is a rectangular region with a width of and a length of . At the lower boundary the temperature is kept at , and the top and right boundaries are exposed to the natural convection to the ambient environment. The remaining left boundary is thermally insulated. The ambient temperature and the heat transfer coefficient are given by and , respectively.

Test Reference:

[1], A.D. Cameron, J.A. Casey, G.B. Simpson. Benchmark Tests for Thermal Analysis. NAFEMS Documentation.

Equation:

For a steady-state heat transfer model without sources, the transient term and the source term in the heat equation are set to zero. Since a solid is modeled, internal velocity also vanishes and the heat equation simplifies to:

The heat transfer coefficient and the thermal conductivity of the medium are given by and , respectively. The ambient temperature is held at .

Define the model variables and parameters:

Set up a 2D steady-state heat transfer model:

Solution:

At the point the reference temperature value is given by .

Specify the reference temperature value at point

Boundary Conditions:

The temperature at the lower boundary is fixed at .

Set up a temperature surface boundary condition on the lower boundary:

The top and right boundaries are exposed to the natural convection to the ambient environment at temperature .

Set up a convective boundary condition on the top and right boundaries:

A default thermal insulated boundary condition is implicitly applied on the remaining left boundary.

Region:

Set up the model region:

Test 1:

Solve the PDE model and monitor time/memory usage:

Test the inactive PDE:

Visualization:

The following cells are marked as not evaluatable to save the runtime and consume memory. To make these cells evaluatable, select the cells in question and choose Cell ▶ Cell Properties and make sure "Evaluatable" is ticked.

Set up a legend bar and ContourPlot options for the temperature field plot:

Visualize the temperature field:

HeatTransfer-FEM-Stationary-2D-Single-HeatTransfer-0002

The following test case demonstrates a 2D stationary thermal analysis. The model domain is a ceramic strip that embedded in a high-thermal-conductivity material.

The side boundaries of the strip are maintained at a constant temperature . The top surface of the strip is losing heat via both convection and radiation to the environment at . The bottom boundary, however, is assumed to be thermally insulated.

Test Reference:

[2], Holman, J. P. Heat Transfer Tenth Edition, McGraw-Hill. pp. 111, Example 3-10 (2008).

Equation:

The thermal conductivity , heat transfer coefficient and emissivity of the ceramic trip are given by:

The temperature of the left and right boundaries are held at , and the ambient temperature remains at .

Define the model variables and parameters:

Set up a 2D steady-state heat transfer model:

Solution:

At points , and , the reference temperature values [3] are given by:

Specify the reference temperature value at point

Boundary Conditions:

On the left and right boundaries the temperature are held at to .

Set up temperature surface boundary condition at the left and right boundaries:

The top boundary is exposed to the environment at an ambient temperature , and losing heat by both thermal convection and radiation.

Set up the convective boundary condition with the heat transfer coefficient

Set up the thermal radiation boundary condition:

A default thermal insulated boundary condition is implicitly applied on the remaining bottom boundary.

Region:

The ceramic strip has a width of and a height of .

Set up the model region:

Test 1:

Solve the PDE model and monitor time/memory usage:

Verify the solution:

Visualization:

Set up a legend bar and ContourPlot options for the temperature field plot:

Visualize the temperature field:

Next we calculate the rate of heat loss at the top surface of the strip. The convection and radiation heat flux , are given by:

Calculate the rate of heat loss

at the top surface:

The heat loss rate of the ceramic strip is found as . This value can be checked by utilizing the law of energy conservation. That is, the total heat loss from the top surface must equal to the conductive heat gain from the left and right boundaries:

Calculate the total heat gain

from side boundaries of the ceramic strip:

Note that the heat gain value matches with the rate of heat loss .

2D Axisymmetric Single Equation

This section contains axisymmetric stationary heat transfer PDE model in cylindrical coordinates with one equation.

HeatTransfer-FEM-Stationary-2DAxisym-Single-HeatTransfer-0001

The following test case demonstrates a 2D axisymmetric steady-state thermal analysis. The model domain is a hollow cylinder with a height of . The inner radius and the outer radius are given by and , respectively. At the inner boundary a constant heat flux is applied to heat up the domain. On the outer boundary the temperature is held at . The remaining bottom and top boundaries are thermally insulated.

Test Reference:

[4], J.M. Owen and R.H. Rogers. Flow and Heat Transfer in Rotating-Disc Systems. Wiley, (1989).

Equation:

For a 2D axisymmetric stationary heat transfer model without sources, the transient term and the source terms in the heat equation are set to zero. Since the medium is solid and the model is rotationally symmetric in the direction, the terms involving the flow velocity and the axis also vanish. Then the heat equation simplifies to:

Set up a 2D axisymmetric, steady-state heat transfer model:

The material has a thermal conductivity .

Define the model parameters:

Solution:

The analytical solution of the temperature field is given by:

Set up the analytical solution for the temperature field in rod:

Boundary Conditions:

The inner boundary is subjected to a constant inward heat flux .

Set up a heat flux boundary condition on the inner boundary:

The temperature at the outer boundary is fixed at .

Set up a temperature surface boundary condition on the outer boundary:

A default thermal insulated boundary condition is implicitly applied on the remaining bottom and top boundaries.

Region:

Set up the model region:

Test 1:

Solve the PDE model and monitor time/memory usage:

Test the inactive PDE:

Visualization:

Set up a legend bar and ContourPlot options for the temperature field plot:

Visualize the temperature distribution in the radial direction:

Inspect the temperature field of the hollow cylinder:

Inspect the error at

Transient Tests

This section contains examples of transient (time-dependent) heat transfer PDE models for the validation.

1D Single Equation

This section contains examples of transient heat transfer ordinary differential equations (ODE) models with one equation. Ordinary differential equations with one independent variable are a special case of partial differential equations that usually deal with more than one independent variable.

HeatTransfer-FEM-Transient-1D-Single-HeatTransfer-0001

The following test case shows a transient heat diffusion process within a plate. The temperature on the left surface varies sinusoidally in time, on the other surface the temperature is fixed at . It is assumed that the plate is very large compared to its thickness, so the analysis reduces to a 1D heat transfer model along the thickness.

Test Reference:

[5], A.D. Cameron, J.A. Casey, G.B. Simpson. Benchmark Tests for Thermal Analysis. NAFEMS Documentation.

Equation:

For a transient heat transfer model in solid without sources, the source term and the internal velocity in the heat equation are set to zero. The heat equation then simplifies to:

The density, heat capacity and the thermal conductivity of the medium are given by and , respectively.

Define the model variables and parameters:

Set up a 1D transient heat transfer model:

Solution:

At time the reference temperature at point is given by .

Specify the reference temperature value at point

Boundary Conditions:

On the left surface the plate experiences a transient heating, where the temperature varies sinusoidally in time by: . On the right surface the temperature is held at .

Set up the temperature surface boundary condition on both ends of the domain:

Initial Conditions:

At time , the temperature of the plate is .

Specify the initial condition:

Region:

The thickness of the plate is given by .

Set up the model region:

Test 1:

Set the simulation end time

Solve the PDE model and monitor time/memory usage:

Verify the solution of the PDE:

Visualization:

Visualize the evolution of temperature field within the plate:

HeatTransfer-FEM-Transient-1D-Single-HeatTransfer-0002

The following test case demonstrates a transient heat diffusion within a rod. On the left end a constant outward heat flux is set to simulate the cooling process. On the right end the temperature is fixed at .

Test Reference:

[6], H.S. Carslaw and J.C. Jaeger. Conduction of heat in solids. Oxford at the Clarendon Press, Second Edition. (1959)

Equation:

For a transient heat transfer model in solid without sources, the source term and the internal velocity in the heat equation are set to zero. The heat equation then simplifies to:

The density, heat capacity and the thermal conductivity of the medium are given by and , respectively.

Define the model variables and parameters:

Set up a 1D transient heat transfer model:

Solution:

The analytical solution of the temperature field is given by:

Set up the analytical solution for the temperature field in rod:

Boundary Conditions:

The left end is losing heat at a constant outward heat flux .

Set up the heat flux boundary condition on the left end:

The temperature at the right end is fixed at .

Set up the temperature surface boundary condition on the right end:

Initial Conditions:

At time , the temperature of the plate is .

Specify the initial condition:

Region:

The model domain is a rod with a length of .

Set up the model region:

Test 1:

Set the simulation end time

Solve the PDE model and monitor time/memory usage:

Verify the solution of the PDE:

Visualization:

Visualize the evolution of temperature field within the plate:

Inspect the error at

2D Axisymmetric Single Equation

This section contains axisymmetric transient heat transfer PDE model in cylindrical coordinates with one equation.

HeatTransfer-FEM-Transient-2DAxisym-Single-HeatTransfer-0001

The following test case demonstrates a 2D axisymmetric transient thermal analysis. The model domain is a cylinder with a radius of and a height of . The temperature of the entire domain begins at . At outer boundaries the temperature experiences a step jump to and stays at for .

Test Reference:

[7], A.D. Cameron, J.A. Casey, G.B. Simpson. Benchmark Tests for Thermal Analysis. NAFEMS Documentation.

Equation:

When modeling the heat transfer in a solid medium without sources, the internal velocity and the source in the heat equation are set to zero. Since the model is rotationally symmetric in the direction, the terms involving the axis also vanishes. Then the heat equation simplifies to: