Design for Thermal Issues

Assignment 2
Modelling heat at the system level

Covers Learning outcomes 3 & 4
Units 9–11
Notional workload 25 hours
Weighting 50%
Comments For information on submitting assignments, please refer to the AMI home page under Students, Assignments
Submission date Midnight at the end of study week 12
Please refer to the module planning chart for the date

Introduction

As described in the Module Descriptor, this module is assessed by two assignments which involve the thermal investigation of electronic assemblies. The first of these examined the detail of components on a board assembly, whereas now our focus is at the system level, on the thermal evaluation of a standard telecommunications rack.

In addition to performing a simulation and analysis of the rack by using the FLOTHERM toolset, you are expected to demonstrate a theoretical assessment of the unit’s thermal characteristics, based on the foundation material covered in other Units within the module, which may then be contrasted with the outcomes of the software simulation.

The application

The enclosure to be studied is a rack for a telecommunications system that incorporates 14 boards, of which two are the router boards that were analysed in Assignment 1. The enclosure has a fan and two vents, and its mechanical and thermal aspects are described at this link.

As head of the thermal analysis team for this organisation, you are required to undertake an evaluation of this rack in order to:

Requirement

  1. Theoretically evaluate the thermal performance of the rack.
  2. Construct the model and conduct a preliminary analysis using FLOMOTION.
  3. Ascertain which boards are being inadequately cooled and document the temperature distribution.
  4. Suggest design modifications, and demonstrate that these would improve the situation in 3 above. Note that the size of the unit is fixed, and that the boards must be positioned as shown.
  5. Produce a technical report that details your findings. State clearly any assumptions made.

You can assume that the members of your audience are aware of the components used and of the functional features of the design, but have only a partial understanding of thermal matters.

As a guide, you are unlikely to include all the points we expect to find if your main report has fewer than 2,000 words. There is no maximum word count as such, but excessive length may be penalised.

In order to keep your script concise and well-argued, and its structure clear, you may find it helpful to provide relevant supporting material in appendices to the main report. This applies particularly to detailed calculations and information collected during the analysis and simulation elements of the task.

A word to the wise . . .

In general, there are no single correct answers to simulation questions, so the key to getting high marks is to submit reports that show the thought processes through which you have gone, and display your understanding of the topics, as regards both the simulation itself and the practical issues involved in thermal management.

For this second assignment, we expect you to be able to make informed choices about issues such as the type of model and the positioning of temperature probes without our having to spell out the detail. But we also expect you to include in your report a brief rationale for each of the major decisions you take, and to discuss other key aspects such as the likely inaccuracies.

 

Health warning

In order to keep computational time to a minimum, be careful to make appropriate choices of grids, using fine meshes only where needed. And avoid high aspect ratios in grid settings: these should be as close to unity as possible, and high values lead to guaranteed non-convergence.

Also, be aware that solving any model is a considerable task, and will take substantial computing time. We recommend:

 

Caution

In writing your report, you are expected to include some evidence of having studied all the relevant course material and perhaps supplemented this with wider reading/web browsing. In order to make reference to this in an appropriate and consistent way, we recommend that:

Given the transitory nature of some web sites, we also recommend that you retain electronic copies of any material cited!

 

As always, you are strongly recommended to re-examine your draft report and conclusions to check that you have covered all the elements required in the report.

Marking scheme

The maximum marks available for each element of the report are as shown in the table below:

Element
Maximum marks
Perform theoretical assessment of rack
15%
Model the rack in FLOTHERM
15%
Evaluate temperature distribution throughout unit
10%
Perform design modifications and improvements
30%
Recommendations and conclusions
20%
Quality of presentation
10%

For information on grades, please refer to the AMI home page under Students, Assignments, Marks and Grades.

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