Engineering Exam Question Missing Information...

danza

danza

danza

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Guten evening all!

Had a materials and engineering systems exam today, and one question was seemingly missing information required in order to be able to answer it. This meant nobody could answer it without making a complete guess as to the missing value, and therefore coming up with likely totally different answers to one another.

This really threw me as I thought it was something I missed during revision, and instead spent the 30 mins I should have used to answer that question double checking other answers.

It turns out that I did know how to answer the question as it was something I had revised and knew well. Other people have confirmed that the info was missing and basically guessed.

Has anyone had a similar experience, and if so, what was the outcome?

I can't believe this managed to get through and into the exam room without someone noticing. :/
 
I don't think that was meant to be the case. Nothing we were taught or told indicated that the questions would be anything other than 'straightforward', with all information provided. This was confirmed by about a dozen tutorial questions and 4 previous year's exam papers.
 
Gaseous propane (C3H8) is burned with 50% excess air in a combustion chamber. The propane enters at 25oC (298.1 K) and the air at 7oC (280.15 K). The mass flow rate of the propane is 0.1 kg/min. The products of combustion leave the combustion chamber at 1400K. The enthalpy of reaction for gaseous propane is -2214.52 MJ/kmol.

Calculate:

the mass flow rate of the air
the rate of heat transfer from the combustion chamber
Click to expand...

The question is worded in a way that could suggest that there is only one answer by the bold text above, i.e. not 'a mass flow rate of the air' etc.

The exam question was basically exactly as above, but the quantity of excess air was not given as it had been in all previous exam/tutorial questions (either that or there's been a way to calculate it from the information given). Simply, 'XX%' was missing. Also, the question was worth 18% of the exam and was one I was pretty confident in answering. :/

If I've missed a trick here, I'll gladly wear the forum's dunce hat for a day.
 
memyselfandi said:
Just use the real world method (rather than the exam method) of wild-***-guessing whatever information is missing ...

(or possibly talk to your lecturer/tutor about it; either they might be able to tell you if you were missing a trick on how to solve the problem or arrange for the issue to be investigated and potentially the marking scheme changed).
Click to expand...

Tutor has been emailed. :)

And of course, real world engineering is often far removed (but not so far) from the theoretical in order for the product to function, whilst at the same time being physically possible (we get this a lot at work).
 
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