Reference no: EM132312306 , Length: 10
Process Engineering - Report Writing Assignment - Lab Report
You are required to prepare a lab report on the conductivity of two membranes to evaluate their use as electrolytes in proton exchange membrane fuel cells, PEMFC.
The two membranes have three components: A, S and M, in % molar compositions stated in Table 1. A and M are non-polar compounds, whilst S is a highly polar compound.
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Table 1 - Membranes and compositions
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Membrane
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% A
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% S
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% M
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A09S85M06
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9
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85
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6
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A29S36M35
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29
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36
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35
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Once central variable to determine how good a membrane is for fuel cells, is the direct current conductivity, ?dc, which measures how many ions (protons) can be transferred from anode to cathode. The higher the conductivity, the better the membrane.
In the lab, we measured the real component of the complex conductivity, σ', for the membranes in Table 1, by applying alternating electrical fields at different frequencies (Hz). We carried out these measurements in isothermal steps, on cooling from either 120oC to 30oC (A09S85M06), or 120oC to 70oC (A29S36M35). Units for conductivity are mS·cm-1, and these should be kept during all the discussion (not using International System).
The complex conductivity, σ', is frequency dependent, but allow us to calculate the direct current conductivity, σdc, which is unique for each temperature.
The aim of the experiment is to determine the evolution of the direct current conductivity, σdc, with the temperature, calculate the activation energy of σdc, and compare the results for each membrane, discussing their potential use as electrolytes in PEMFC. The activation energy can be useful to determine the optimum operation point of your fuel cell.
The raw results are found as txt files in different folders, including the name of the sample and the corresponding temperature. You are advised to import these files in Excel, for the graphical representations. You can then use Power point to format the figures (or use them from Excel directly) and then paste them in Word.
In order to show the results and calculate the previous variables, you will have to:
For each temperature (and sample), plot the σ' as a function of frequency, in double logarithmic plots.
Find plateaus in these plots, and estimate a value of σdc for each temperature, by extrapolating the σ' values when the frequency tends to zero (dc conditions, essentially, the σ' value in the plateau of the double logarithmic plots).
- Plot ln(σdc) versus 1/T (reciprocal temperature, in absolute units). Then, assuming an Arrhenius behaviour, the slope of the straight line should give you the activation energy, Ea, according to: ln(σdc) = ln(k0) - (Ea/R) 1/T Eq. 1
where k0 is a pre-exponential factor and R is the gas constant (8.31 in international system units)
You must produce (at least) two plots per sample, and obtain two activation energy values, Ea, one per sample, which must be used in the discussion.
The report must include the following sections:
- Title (front page)
- Contents
- Abstract
- Introduction (based on the relevance of Fuel Cells and particular Proton Exchange Membrane Fuel Cells and theoretical insights you consider relevant)
- Aims
- Results and discussion
- Conclusions
- References (see specific instructions below)
The assignment is designed for you to display your ability to:
Research subject matter, using the library and web based sources.
Properly format your essay and reference material (Harvard style referencing).
Import data as necessary to enhance your information.
Reference and cite correctly using the recommended style, to work within the confines of plagiarism (include at least 5 references: a minimum of 2 books, 2 web based sources plus one other of your choice).
Maximum extension of the report is 10 pages: it must be concise and individual.
Attachment:- Assignment Files.rar