How Different is the 2016 NCEES Practice test from the 2011 one?

I see that they have a new one listed, copyright November 2016. Anyone have both and compare?

I suspect the new one is aligned to the new test format that essentially does away with breadth questions.

Well, I said the above without even looking at their site, and from their description of the new booklet:

"Some new questions have been added to represent the revised exam specifications, but most are the same great questions reused from previous editions and selected by the engineers who write the actual exam. "

The booklet contains exam spec before the exam. It's updated to reflect revised specification. 

Notice this thread. See my post here...

http://engineerboards.com/index.php?/topic/24508-how-i-passed-the-thermal-fluid-pe-exam/&do=findComment&comment=7404137

I'm bought the new book when I registered for the exam (saved a few bucks that way).  I took a quick look through it (I bought the Mechanical Systems and Materials) and I saw 28 new questions.  The questions are in a different order than the 2011 book, so it threw me off at first.  Even if I mistook a few for new, there's easily 25% new questions in the book.  If the book goes for $40, you're spending about $25-$30 for new questions.  To me it's worth it, YMMV.

aakrusen said:

I'm bought the new book when I registered for the exam (saved a few bucks that way).  I took a quick look through it (I bought the Mechanical Systems and Materials) and I saw 28 new questions.  The questions are in a different order than the 2011 book, so it threw me off at first.  Even if I mistook a few for new, there's easily 25% new questions in the book.  If the book goes for $40, you're spending about $25-$30 for new questions.  To me it's worth it, YMMV.

Click to expand...

I meant to say that I bought the Machine Design and Materials book, not the MSM book.  MSM is what they called it before 2017.

Just wanted to point out that I have found several errors in the book.  Most of the errors are in the answers for the problems.  The incorrectly show how to answer the question and the answer they get doesn't jive with the way they show how to do it.  This may cause frustration for those that are not as familiar with the content (meaning those types of problems) and may require additional research while trying to learn the material.

aakrusen said:

Just wanted to point out that I have found several errors in the book.  Most of the errors are in the answers for the problems.  The incorrectly show how to answer the question and the answer they get doesn't jive with the way they show how to do it.  This may cause frustration for those that are not as familiar with the content (meaning those types of problems) and may require additional research while trying to learn the material.

Click to expand...

Would you mind pointing out which problems are solved incorrectly? The only mistake I have found thus far is that they solved the problem as I have and arrived at the same answer but selected the wrong letter (problem 515).

Sorry, I can't find an edit button. I realized you were talking about a different exam.

The only error I found in the TFS 2016 exam was problem 515. My mistake.

What do you guys think about problem 124?  I think 3 pumps is much closer to about 55 ft (~167 gpm on pump curve*3= 500 gpm and intersects system curve at around 55 ft of head) which isn't close to the choices available. In any cause it is clearly below 65 ft, but clearly above 38 ft.

This was excellently answered by Audi on this other post, but I wanted to add here in case someone only clicks on this thread.

The solution appears to me to be correct. I get 65-70 ft estimating off of the diagram with a ruler (3xdistance measured to the intersection). I'm also not sure how you got ~167 GPM as the intersection occurs ~230 GPM. 3x230 = 690 GPM

Pump in parallel you sum the flow while head remains constant. Then where the system curve intersects the sum of the parallel pump curves you get your operating point. 3 pumps in parallel @ 230*3=690 GPM the pump provides 35 ft of head not 65-70 ft.

I didn't use a ruler but eyeballing 65 ft on the system curve I get about 600 GPM. Divide this by number of pumps (3) I get 200 gpm required by a single pump at 65ft head. The single pump curve is clearly lower than 200 gpm. 

167 gpm is where the combined 3 parallel pump curve intersects the system curve.

167 gpm is where the combined 3 parallel pump curve intersects the system curve.

By the statement above I mean 167 gpm each which multiplied by 3 gives total flow of 500 gpm and intersects at 55 ft head on system curve

Essentially 1 pump 167gpm 55 ft head, 3 pumps in parallel 500 gpm 55 ft head, system curve 500 gpm @55 ft of head therefore new operating point is 500 gpm 55 ft head. Sorry I'm writing this from my phone so hopefully this makes sense

Here's a illustration that should help clarify things...

Sorry really struggling on this...hopefully that will be out of my system come Friday! See attached

Nevill24 said:

Pump in parallel you sum the flow while head remains constant. Then where the system curve intersects the sum of the parallel pump curves you get your operating point. 3 pumps in parallel @ 230*3=690 GPM the pump provides 35 ft of head not 65-70 ft.

I didn't use a ruler but eyeballing 65 ft on the system curve I get about 600 GPM. Divide this by number of pumps (3) I get 200 gpm required by a single pump at 65ft head. The single pump curve is clearly lower than 200 gpm. 

167 gpm is where the combined 3 parallel pump curve intersects the system curve.

Click to expand...

First of all, there are no units on the flow, so that should be a clue to you that this is a logic problem and not one where you need to find a hard and fast solution.

Second, as I noted in the other post, for a SINGLE pump, you have about 38ft of head where the pump curve intersects the system curve.  Adding pumps is NOT going to move you backward on the system curve to any point lower than that.  In fact, it does the opposite.  So, as you add pumps and flow, you actually DO move up in head because of the shape of the system curve given.

The only logical choice given the answers provided is 65 ft. Why? Because 38 ft. is the head for one pump, not three. 30 ft is moving the wrong direction on the system curve, and 210 ft is not achievable with the pumps in the scenario.  65 ft may not be the exact answer given the curve they provided, but they are NEVER asking for the exact answer, only the CLOSEST answer.

I don't disagree with anything your saying Audi. I took the practice exam and selected 65ft for the reasons you point out. That said, I just feel it is a poor choice provided by NCEES. Only way you go above the pump curve like that is with an oversized impeller, clearances are tightened, VFD, etc changes are made to the original pump. Obviously since others have posted this problem within the forums I'm not the only one that sees issues with it.

Once again 65 ft is the best choice, but in my opinion a poor one. I think it's worth discussing so people understand such as amats believing the pump curve would intersects the system curve at 690 gpm. If say 55 ft was given as a choice in place of say 210 ft he would have chosen the wrong one (see my graph showing actual intersection).

Go over the pump curves?  I don't think you're fully grasping parallel flow.  Either that or you're not looking at the graph close enough...  and you may not be.  For example, I don't get where you come up with 167 for flow and 55 ft of head on the single pump graph that is given.  The values at the intersection of the pump and system curve are closer to 38 and 230.  And the chart you provided here doesn't quite jive with the one given either.  In any case, the solution chart they plotted and provide in the answer is pretty accurate for the assumptions you have to make to solve this problem.

The only ACTUAL issues with this problem is that there is not a very good way to come up with the exact 65 ft figure, given the plot you're given.  As I noted that is the answer because it's still below the max pump head and is higher than the other two answers that are also disqualified purely by using logic.  Really it's between 210 and 65, but 210 is way out of range because it's above what the weakest pump can produce (75 ft)... by a factor of at least two.

You must be looking at the graph incorrectly.  See below. Do you not agree that the flow for 3 pumps in parallel triples that of a single pump at a given head?  Look at the uploaded image of the curves given on the practice exam.  The graph i have in my post above is just taking the data from the curves given on the practice exam and plotting it in excel with the parallel pump curve and if you look closely you can see that the intersection is around 520 gpm and 55 ft head.


Head


Flow 1 pump


Flow 3 pumps


70


0


0


65


100


300


45


200


600


0


300


900

And "go over the pump curve" by that i mean you are given a design pump curve that is tested at the factory.  Any way to operated above the curve is if changes are made (e.g. impeller sizes, motor speed, tighter clearances, etc).  Only way you operate below the curve is intentionally due to VFDs or loss of efficiency (opened up clearances, worn impeller, cavitation, etc.)