代写TPFE留学生、代写Methods Group、代做Matlab、Matlab语言程序代写

日期：2018-11-29 11:14

TPFE

Experimental Methods Group Project

__________________________________________________________________________________

Heat Transfer from Extended Surfaces in a Crossflow

Introduction

Heat transfer is a major factor in many engineering situations as fluids are used to remove thermal energy from components to reduce their temperature and maintain sensible operating conditions.  Such heat transfer usually relies on convection, either due to buoyancy where heated fluid moves drawing in cooler fluid or forced by the use of a fan or some other means of moving the fluid.  

In order to improve cooling efficiencies the hot surface area can be increased by using additional material in the form of fins or plates.  This is particularly common with, for example, motor vehicle radiators, computer CPU cooling systems or amplifiers in electronic circuits.

It is important that any extended surface has a good thermal connection to the surface it is trying to cool.  In permanent structures (vehicle radiators) the extended surfaces are welded to the main pipework of the radiator.  In situations where components may need removing or replacing, the extended surfaces aren’t permanently attached to the hot component.  To maintain good thermal contact it is usually the case that thermally conductive paste is used to improve conduction,

If you consider that the thermal conductivity of air is of the order 10000 times less than that of aluminium (air 0.024W/m/K, aluminium 200W/m/K), any small air gaps will lead to high temperatures because heat isn’t being conducted as well as it could be.  Typical thermally conductive paste (usually known as heat sink compound) has a thermal conductivity of around 1W/m/K, still much less than continuous metal, but significantly better than air.

The cooling behaviour of a surface is primarily defined by its heat transfer coefficient, h, a value that can vary with flow parameters (temperature, viscosity, velocity) as well as geometric parameters (size, shape, roughness).  Because the extended surface is in a flow it will generate a boundary layer.  A laminar boundary layer is much less efficient at cooling a surface than a turbulent boundary layer because of the much reduced fluid mixing though thermal effects can cause a laminar boundary layer to undergo transition to turbulence.

In a steady state flow, the heat transfer from a surface, q, is generally defined as

where h is the heat transfer (convection) coefficient, A is the surface area, Ts is the surface temperature and Tf is the fluid temperature.

Because of the wealth of existing work that has been done on heat transfer from surfaces and extended surfaces there are values of heat transfer coefficient that can be used in analytical calculations and there are also a number of empirical relations that use the Nusselt number, Nu, Reynolds number, Re, and Prandtl number, Pr.

Project

The aim of the project is to determine the heat transfer from an internally heated aluminium block with 3 fins mounted in an array of fins, as shown in the figures below.  The grey finned section is aluminium and the yellow coloured fins are manufactured from acrylic or wood.  The bottom figure shows an example of the perforated fin that may be used to enhance turbulence.  The aim of the project is to see if it does.

The experiment will consist of tests done with different fin profiles – blank, as in the top image, and perforated, see the middle image – with different groups checking the performance of different perforations.  The metal finned surface itself consists of 3 parallel fins, 40mm high x 150mm long and 3mm thick, with one heat transfer gauge near the leading edge and the other heat transfer gauge near the trailing edge.  

Primary Instrumentation in the Experiment

Thermocouples

The thermocouples are K type thermocouples and the output from these is amplified using the AD595 instrumentation amplifier that is specifically designed for use with such thermocouples and has an output of 10mV/K.  This amplifier is inserted into a DIP socket.  In use the thermocouples need to be untwisted, i.e. the two metal wires should not contact each other, apart from at the bead itself otherwise the wrong temperature will be measured.

In this project some self-adhesive pads will be provided to stick the thermocouples to the fins, where desired, and there will be additional thermocouple extension wires and plugs/sockets to increase their length.

To make connection to the myRIO and prototyping breadboard, some screw terminal connectors will be provided

Pads : http://uk.rs-online.com/web/p/temperature-probe-accessories/7887148/

Extension wire : http://uk.rs-online.com/web/p/thermocouple-extension-wire/2363820/

Connectors : http://uk.rs-online.com/web/p/temperature-sensor-accessories/4559786/

Screw terminals : http://uk.rs-online.com/web/p/pcb-terminal-blocks/2204260/

The Task

The tests will be done in the “RON” wind tunnel in laboratory A5.  Note that due to other laboratory classes this equipment will not be available to be used until Week 9 so you have plenty of time to get code written and decide what to do in this task.

Using the supplied hardware, design and conduct an experimental campaign to:

1.Measure the heat transfer from a finned surface using thermocouples

2.Measure the heat transfer with the presence of upstream dummy fins, perforated fins and without fins.

Present this in a report format as would be expected by an industrial customer. In your report you should comment on how the heat transfer from the fins is affected by the presence of the different upstream fins.

Hardware

The thermocouples will be common to all groups and can be located as desired with the adhesive pads.  Cartridge heaters connected to a Variac to provide the heat.

In order to complete this task the wind tunnel/model will be equipped with:

1 x National Instruments myRIO 1900 with prototyping boards

8 x K type thermocouple

8 x AD 595 thermocouple amplifiers

2x cartridge heaters

1 x Variac for powering heaters

2 x Analog voltmeter/ammeter to measure supplied power (volts and current)

1 x Pressure transducer for tunnel speed.

Additional wires/cables will be provided as necessary

Groups will be provided with a myRIO in order to develop their code and this can be uploaded to the myRIO on the Wind Tunnel when tests are done.

Assessment

The final report and accompanying software will be graded with a group mark and feedback given.

Limited-participation is not acceptable and in cases where members are not contributing to the group, peer moderation will be taken into account and marks will be adjusted.

Non-participation will result in that member of the group receiving 0% for the project.

Report

The written report covering your project should contain:

1.Any background reading about the experiment

2.Your experimental design including justification

3.The method of acquisition (calibration, record rate, etc.)

4.Details of the implementation of the hardware – including calibration method

5.The experimental results

6.Uncertainty analysis of the data

7.Analysis of the data including method

8.Conclusions

9.Any future recommendations

10.References

11.An experimental log in the appendix

This report should be no longer than 8,000 words or 20 pages in total (this is a limit, not a target) otherwise a -10% penalty will apply.

Software

Software written by you will be submitted as part of your final assessment. This code should be commented, easy to follow and error free. Projects where no code is submitted will receive zero marks for this section. This software is to be submitted with your final report and will comprise 25% of your final mark for this project.

Inspiration can be taken from the supporting files supplied with the lectures on blackboard but no pieces of software should be copied from either blackboard other sources (files can be referenced but not used without acknowledgement). Any groups found copying files will receive zero marks for this section.

LabVIEW

You are required to take sample data using the sensors provided and store the data to disk. This is to be achieved using the NI myRIO device using a LabVIEW program written by you. You may want to use timed structures within this measurement to ensure timing accuracy.

Matlab

The software used to analyse your results should be based in Matlab. These files should use functions appropriately and should be submitted along with your final report.

Marks Breakdown

Introduction/background – 5%

Software (Labview and Matlab) – 25%

Methodology of the experiment and Calibration of the sensors – 15%

Recording of the data – 15%

Uncertainty analysis – 10%

Presentation of the data – 10%

Concluding from the results – 10%

Report structure and presentation – 10%

Advice

This project involves several aspects of programming, installing hardware and data analysis. It is much easier to approach a group project such as this if the group divides tasks between members evenly. Some members could focus on LabVIEW programming whilst others could focus on developing Matlab code or developing a test plan; however, the exact formulation of your group is up to you.

All group members should be familiar with the codes implemented during the project and the methods used.

Throughout the project, there will be online Blackboard discussion boards where groups can post open questions. These will, where appropriate, be answered by the course leaders but can also be answered by other groups. This should be your first port of call before asking for any more specific help.

Learning outcomes

This project will develop your ability to:

1.Design and implement an experimental campaign

2.Collect data using industry standard tools on a real structure

3.Reduce data from an experiment

4.Post process experimental data to yield desired outcomes

5.Calculate parameters based on experimental results

6.Apply a thorough error analysis

7.Present data in an appropriate and scientific fashion

8.Work effectively as a team of experimentalists

Bibliography

Extended Surface Heat Transfer, Kraus K.D., Aziz A. and Welty, J., Wiley, 2001.

Fundamentals of Heat and Mass Transfer, 6th Ed., Incropera F.P., deWitt, D.P., Bergman T.L. and Lavine A.S., Wiley 2007

Conduction of Heat in Solids, 2nd Ed., Carslaw H.S. and Jaeger J.C., Oxford Science Publications, 2000.

Reference

1.  TPFE MSC Group Project : Introduction.  Available on Blackboard on and after 3 November 2017