FEM Thermal Analysis
- Finite element analysis (FEA)
- Finite different approaches
- 1D Thermal networks
- Thermal analysis of computational fluid dynamics (CFD) simulation solutions.
Where do FEM Thermal Analysis Fit in the development process?
Discover FEA Simulation to Bring further Advantages.
The similarity between Structural and Thermal Modeling
- Variable involved we are solving for (Linear Displacements is replaced by Temperatures)
- Input Terms in the Matrix equations that we are building (Stiffness is changed to Thermal conductivity)
FEA Software Key features
- Accurate noise and vibration diagnostics with Professional Technical Analysis Assistance from FEA modal, grid, panel, energy, and path contribution FEA Analysis Using the Finite Element Method FEA Software
- During a Pipe Stress Analysis, the Professional Structural Engineer performing the FEA Stress Analysis Services are Capable to Accurately Map test data and predecessor simulation data – multibody, electromagnetics (EM), computational fluid dynamics (CFD) – onto the vibro-acoustic Simulation model, including time-to-frequency domain conversion for Receiving realistic Loading Values
- The Nonlinear FEA Software Include frequency response function (FRF) and modal Modeling for Structure components in assembly context using Both Numerical simulation Modeling or Theoretical Testing data
- Include acoustic Translation vectors (ATV) or vibroacoustic transfer vectors (VATV) Modeling representations for acoustic or vibroacoustic components, which are Re-cyclable for multi-load case scenarios for Stress Engineering & powertrain noise or Passenger cabin wind noise
The Simcenter Femap NX Nastran Distinctive advantage
3. LS-DYNA Consulting
We Help Our Clients Gain Valuable Insights to Optimize and Improve Product Performance, Reliability, and Efficiency.
1. Powerful ANSYS FEA Simulation Software Tools
2. FEA Consultants with Extensive Research & Professional Experience
3. FEA projects Completed in a Timely and Cost-effective Manner
4. Proven Track Record
6. Full Knowledge Transfer
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Important Considerations when Performing FEM Thermal Analysis
1. Conduction Considerations
Amount of Temperature DifferentialThermal heat energy will flow from the hotter region to the cooler region.The larger the temperature differential the more thermal energy that is being transferred
Component material Cross-Sectional AreaThe bigger the component cross-sectional dimension, the more the thermal energy that is being transferred
Thermal conductivity of Component MaterialHow well material is able to conduct Thermal energy depends on its Thermal conductivity which is an inherent material property. In general, a metal material (eg. Copper) is able to efficient at conducting more thermal heat energy than non-metal (eg. Ceramics)
2. Forms of Convection Heat Transfer
- The temperature difference between the surface and the free fluid
- Area of Heat transfer Surface
- Value of the material Convective heat transfer coefficient
Basic Forms of Convective Heat Transfer
Free ConvectionIn free convection scenario, the fluid is initially in a stationary condition. Fluid circulation starts when there is an occurrence of local thermal heating.*Notes that the orientation of the thermal heat transfer surface relative to the direction of the gravity force also makes a difference in the convection heat transfer. If a surface is vertically positioned, the effects of gravity can help in encouraging fluid circulation. However, if the body surface is horizontally orientated, gravity does not help in heat circulation.
Forced ConvectionIn a Forced convective heat transfer, the adjacent fluid is being entrained to move along by some external driving force. An example of such a setup includes having a fan blowing across a body heat transfer surface. This assists in providing a more energetic driven medium for the fluid to move away from the heated surface.*Note that as the Computation of the actual convective heat transfer under forced conditions is generally more complex, a coupled Computational Fluid Dynamic (CFD) analysis can be used to give an accurate simulation model.
3. Radiation Calculations
- Emissivity and Absorptivity of the material surface properties
- The angle of the photon transmission path in relation to the body surface.
Four Types of Analysis Solutions
1. Linear Solutions
In a Linear analysis solution, the material thermal properties stay constant is not dependent on time or temperature.
Also for Linear solution scenarios, it is required that there is no radiation heat transfer and no presence of other nonlinear physical effects.
*As the default solution setting defined in most CFD simulation software solvers is usually nonlinear, it can sometimes be administratively confusing to define a linear solution during the initial setup of the simulation.
2. Nonlinear Solutions
In a nonlinear simulation modeling, where radiation is present, most simulation parameters involved can fluctuate with temperature variations.
Such physics parameters with nonlinearity properties can include
1. Material Thermal properties
This includes Thermal conductivity, Convective Heat transfer coefficient
2. Thermal boundary conditions
3. Thermal Loading conditions
This includes externally applied heat flux from a thermal heat source which is a function of temperature. It is important to note that a Nonlinear analysis solution requires an incremental loading approach whereby the Total thermal loading is broken down into successive steps.
3. Steady-State Thermal Analysis
The steady-state condition in a thermal event happens when the thermal temperature distribution and all thermal energy flows are stabilized and remain relatively constant over time.
The steady-state analysis can be easily derived by carrying out an energy balance calculation which assumes a stabilized condition.
Often times such Steady-state conditions are key for deriving the temperature distribution over component, which is then used as an input parameter to perform structural stress analysis.
4. Transient Thermal Analysis
In the Transient Thermal analysis the initial conditions are defined and then an incremental time stepping solving approach is implemented out base on the thermal loading and thermal boundary conditions.
The simulation calculation can be carried out through to a steady-state thermal condition, or to evaluate initial thermal shock loadings, for instance where the steady-state thermal analysis condition is not the primary concern.
One of the considerations in the transient thermal analysis, which is in many ways analogous to a transient dynamic analysis, is an accurate calculation of the time step required.
This time step requirement can be established by the Stability criteria, either automatically by the simulation software solver or manually controlled by the end-user.
Adaptive Time Stepping
The Adaptive time stepping feature included in many simulation solvers can optimize the time step by accounting with such as
Note that it is not advisable to have a Time steps with a granularity coarser than the stability limit.
5. Thermal Strain Loading in a Stress Analysis
In many cases, the main objective of FEM thermal analysis is to provide insights into the thermal temperature distribution for use as input in a subsequent stress analysis.
In a typical uncoupled thermal and structural simulation modeling, a steady-state temperature distribution is mapped from the thermal model to the structural model.
Mapping can either be direct mapping within the same physical mesh or interpolated between dissimilar mesh models. In either case, both mapping approach will result in thermal strains throughout the structure.
Thermal strain values vary proportionally to the change in temperature from initial conditions and are influenced by the value of the thermal expansion Coefficient.
Free Expansion – Zero Stress
If a physical component subjected to a uniform change in temperature is allowed to expand freely, it will result in a uniformly constant thermal strain throughout the component and result in Zero stress.
Restrained Expansion – Thermal Stress
when a component subjected to thermal expansion is secured at 2 points, the component is physically restrained from expanding naturally.
This mechanical strain results in Thermal strain and Thermal Stress which has a relatively more complicated thermal distribution & Mechanical boundary conditions.
Regardless of whether a Temperature dependency of a specific material is linear or nonlinear, the Material structural properties can still allow for a linear static simulation modeling and steady state thermal heat transfer.
A nonlinear static solution may need to be adopted if the thermal heat loading exceeds the Linear structural responses. In many cases, this involves occurrence of regions of material non-linear plasticity, or Physical geometric effects such as large displacement, buckling or mechanical contacts
Experienced judgment is needed here to determine whether a fully coupled solution should be adopted whereby both thermal nonlinearity and structural nonlinearity are constantly updated throughout the duration of the FEM Thermal simulation analysis.
Accuracy & Applicability FEM Thermal Analysis Solution
FEA simulation methodology has a certain level of inaccuracies as it fundamentally involves the discretization of a continuous response.
As the temperature distribution obtained from the thermal analysis is used as input for subsequent structural analysis
It is important to evaluate the sensitivity of that structural simulation analysis to inaccuracies in the thermal distribution.
The observable physical response in the Structural analysis is based on Displacement field.
Assessment of the accuracy of a Structural analysis is determined by analyzing the jump in stress values between adjacent elements and attempt to achieve a convergence.
The observable thermal response in the Thermal analysis is based on temperature distribution, which is typically presented as a contour plot.
The distributions of heat flux passing through each element are able to give us a better sense of the thermal analysis solution compared to the use of temperature distributions.
Heat flux convergence is better than a smooth temperature contour plot as an indicative guide to Accuracy and Convergence because it is similar to the stress convergence in a structural solution.
In mesh refinement analysis, the singularity is retained, but its effect is suppressed, and the overall accuracy of the heat flux distribution, is vastly improved.
Types of Boundary condition for use in Simulation Analysis
1. Application of Physical Mechanical constraints
2. Application of equivalent pressure loading
Challenges of Analysis
Although FEA Thermal analysis solutions are relatively straightforward to set up, there are some inherent challenges involves in such analysis, such as
Types of Heat Transfer
Fundamentally there 3 Modes of heat transfer methods that we have to consider
1. Conduction Heat Transfer
Heat transfer equations: Q = K A (Tupper – T lower)/L
Q = Heat
K = Thermal Conductivity
A = cross-sectional area
Tupper = Temperature at Hot region
Tlower = Temperature at Colder region
L = Path Length
2. Convection Heat Transfer
Heat transfer equations for Natural & Forced Convection from Surface: Q = h A (Tsurface – Tfree)
Q = Heat
h = Convection Coefficient
A = surface area
Tsurface = Temperature at surface
Tfree = Temperature in free stream
3. Radiation Heat Transfer
Heat transfer equations q = ε σ (T4 surface)
q = Heat Flux
ε = Emissivity
σ = Stefan-Boltzmann Constant
T4 surface = Temperature at Surface
The physics of each of these and implications for the FEA solution are discussed in turn.