# Transient Thermal Analysis in Ansys (APDL)

• grey
In summary, the speaker is seeking guidance on how to model a transient thermal problem in Ansys, specifically the cooling of a solar collector receiver tube. They have attempted to set initial conditions and boundary conditions, but are unsure if these are sufficient for a solution. They are also concerned about the results they are getting and are seeking advice on how to properly interpret them. Suggestions are given to check the heat capacity of the tube and to set a different bulk temperature to confirm if the model is working properly. The speaker is also advised to check for any default starting temperatures that may be affecting the results.
grey
Hi,

I have to model a transient thermal problem in Ansys. I just need an outline of how I should proceed.

The Problem:
I am trying to model the cooling of a solar collector reciever tube from 150 degree celsius to ambient.

My attempts have involved the following:
1. Initial condition of 423 at the inner dia of the circle
2. Convection Boundary condition (film coefficient of 25 and bulk temp of 298) at the outer dia of the circle

It is not displaying the results properly (or I am reading them wrong). It shows the entire system at 298 apparently all the time.

Are these conditions sufficient to constitute a solution in Ansys? What else am i doing wrong or I need to do?

Not sure about ANSYS specifically, but are you sure the results are unrealistic? Is the time between steps smaller than your estimated time to reach equilibrium?

Have you specified heat capacity of the tube? With that zero it'll probably reach equilibrium instantly.

Try putting a different bulk temperature somewhere and see that it produces a temperature gradient between then. That should confirm that it's at least doing something! And suggest that it's cooled too quickly.

Did you set an initial condition for the starting temperature of the parts? Default starting temperature is 298 or so, this might be your problem...

## 1. What is transient thermal analysis in Ansys (APDL)?

Transient thermal analysis in Ansys (APDL) is a simulation technique used to analyze the thermal behavior of a system over time. It takes into account the effects of heating or cooling on the system and how it changes over time.

## 2. How is transient thermal analysis different from steady-state thermal analysis?

The main difference between transient thermal analysis and steady-state thermal analysis is that transient analysis takes into account the time-dependent behavior of the system, while steady-state analysis assumes that the system reaches a steady temperature distribution over time and does not consider the transient effects.

## 3. What are the advantages of using Ansys (APDL) for transient thermal analysis?

Ansys (APDL) offers a comprehensive set of tools and features for transient thermal analysis, allowing for accurate and detailed simulations of complex thermal systems. It also allows for parametric studies and optimization, making it a powerful tool for design and analysis.

## 4. What are the steps involved in performing a transient thermal analysis in Ansys (APDL)?

The steps involved in performing a transient thermal analysis in Ansys (APDL) include defining the geometry and materials of the system, applying boundary and initial conditions, setting up the analysis parameters, solving the equations, and post-processing the results to analyze the thermal behavior of the system.

## 5. What are some common applications of transient thermal analysis in Ansys (APDL)?

Transient thermal analysis in Ansys (APDL) is commonly used in various industries, such as aerospace, automotive, and electronics, to analyze the thermal behavior of components and systems. It is also used in heat transfer studies, thermal stress analysis, and thermal management of electronic devices.

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