# NECEES Mechanical PE Reference Manual Released



## cvanwy02

Has anyone seen that NCEES has released the Mechanical PE reference manual which will be used for the computer based exams?

https://core-ncees-org.s3.amazonaws.com/pdfs/pe-mec-handbook.pdf?X-Amz-Content-Sha256=UNSIGNED-PAYLOAD&amp;amp;X-Amz-Algorithm=AWS4-HMAC-SHA256&amp;amp;X-Amz-Credential=AKIAIHJFPKLZRKQERK5A%2F20190225%2Fus-east-1%2Fs3%2Faws4_request&amp;amp;X-Amz-Date=20190225T165150Z&amp;amp;X-Amz-SignedHeaders=host&amp;amp;X-Amz-Expires=300&amp;amp;X-Amz-Signature=33b87488392a4db45188f9966447e3fd83390eae8d35e6719aaceea76c187917


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## Slay the P.E.

cvanwy02 said:


> Has anyone seen that NCEES has released the Mechanical PE reference manual which will be used for the computer based exams?
> 
> https://core-ncees-org.s3.amazonaws.com/pdfs/pe-mec-handbook.pdf?X-Amz-Content-Sha256=UNSIGNED-PAYLOAD&amp;amp;X-Amz-Algorithm=AWS4-HMAC-SHA256&amp;amp;X-Amz-Credential=AKIAIHJFPKLZRKQERK5A%2F20190225%2Fus-east-1%2Fs3%2Faws4_request&amp;amp;X-Amz-Date=20190225T165150Z&amp;amp;X-Amz-SignedHeaders=host&amp;amp;X-Amz-Expires=300&amp;amp;X-Amz-Signature=33b87488392a4db45188f9966447e3fd83390eae8d35e6719aaceea76c187917


The link doesn't work because one has to be logged in to myNCEES to download the manual.

I'm going to urge* HVAC* people to download and review this ASAP. It should put to rest any doubt about what ASHRAE handbooks to bring to the test. Here NCEES has copied everything they deem important. You should review the Refrigeration, HVAC, and Combustion sections and make sure you understand how to use every table and graph in those sections. They're virtually all taken straight from the ASHRAE handbooks.

Similarly for *MDM*. This handbook definitely helps determine which areas of Shigley's you should really emphasize in your prep.

After a quick review with an eye for the *TFS Exam*:


YIKES! no Mollier diagram anywhere in sight. Makes steam turbine problems unnecessarily long.

There are no Normal Shock compressible flow tables, but they do provide the equations, so people taking CBT will have to solve shockwave problems without the benefit of the table. That's not nice of them.

Their table of unit conversions is appallingly sparse.

The psychrometric charts are preposterously blurry, bordering on unreadable.


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## SacMe24

@squaretaper PE....aren't you glad we passed the PE when we did? Imagine taking this exam wihout the use of personal notes, references, books, etc. Look at the evaluation above for the guide that's offered for the TFS exam in particular. WDYT?


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## cvanwy02

Everyone still has two more tries in the pencil and paper!


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## squaretaper LIT AF PE

SacMe24 said:


> @squaretaper PE....aren't you glad we passed the PE when we did? Imagine taking this exam wihout the use of personal notes, references, books, etc. Look at the evaluation above for the guide that's offered for the TFS exam in particular. WDYT?


Yowza...If anyone has been following my posts, I think I've said on no fewer than ten occasions I couldn't have survived without the Mollier diagram. This is just yet another reason people should just get the Mollier diagram tattooed on their forearms! :rotflmao:


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## squaretaper LIT AF PE

@SacMe24 I think this wouldn't hurt MDM folks as much, what are your thoughts?

I can say that TFS people should consider taking the paper-and-pencil exam this year if they can. I might take a crack at trying to do a practice exam with just this reference, just to see. But some of these tables are pretty hard to read. Look at the Moody diagram on page 204, that's pretty hard to use with an embedded table blocking the lines. Especially in the case of water where the Moody friction factor is 0.02 (usually, approximately) with turbulent flow (most real-life cases), kinda sucks to eyeball across that embedded table.


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## squaretaper LIT AF PE

I actually think this might force NCEES to water down the questions. Who really knows...


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## SacMe24

squaretaper PE said:


> @SacMe24 I think this wouldn't hurt MDM folks as much, what are your thoughts?
> 
> I can say that TFS people should consider taking the paper-and-pencil exam this year if they can. I might take a crack at trying to do a practice exam with just this reference, just to see. But some of these tables are pretty hard to read. Look at the Moody diagram on page 204, that's pretty hard to use with an embedded table blocking the lines. Especially in the case of water where the Moody friction factor is 0.02 (usually, approximately) with turbulent flow (most real-life cases), kinda sucks to eyeball across that embedded table.


I looked at the MDM section and WOW, it's basically just a collection of equations. Little to no explanations or examples like in MERM, I'm just VERY glad I took the exam when I did.


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## 23and1

I've downloaded and started going through it. I suppose I'll be one of the lab rats who get to test this out by bringing it with me to the exam in April.


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## Abraham5G PE

I'm logged in to MyNCEES and the link isn't working for me, anyone know where I can download this?

Edit: Nevermind, I found it.


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## squaretaper LIT AF PE

23and1 said:


> I've downloaded and started going through it. I suppose I'll be one of the lab rats who get to test this out by bringing it with me to the exam in April.


I don't want to discourage new test takers with any unnecessary fear mongering about references (or lack thereof). Regardless of whether you will take the new or old tests, if you diligently work a sufficient number of practice questions/exams and really internalize what's really going on with respect to theory, you'll see that it's really quite repetitive (speaking from a TFS standpoint, but I'm sure HVAC and MDM are probably the same, ask those weirdos :rotflmao: ) and you'll pretty much memorize most forms of equations you'll ever need. I got to a point where I pretty much memorized steam table values and only looked things up as a sanity check.

Remember, you're all very smart, beautiful, and capable, AND already working engineers. You can do it!


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## cvanwy02

squaretaper PE said:


> I don't want to discourage new test takers with any unnecessary fear mongering about references (or lack thereof). Regardless of whether you will take the new or old tests, if you diligently work a sufficient number of practice questions/exams and really internalize what's really going on with respect to theory, you'll see that it's really quite repetitive (speaking from a TFS standpoint, but I'm sure HVAC and MDM are probably the same, ask those weirdos :rotflmao: ) and you'll pretty much memorize most forms of equations you'll ever need. I got to a point where I pretty much memorized steam table values and only looked things up as a sanity check.
> 
> Remember, you're all very smart, beautiful, and capable, AND already working engineers. You can do it!


True that.  I haven't taken the test yet but I'm going through the Slay the PE test bundle and have already memorized most formulas and conversions needed for the PE exam... Once you truly understand the concepts, the NCEES questions are not that hard.  I started out with the 2016 NCEES practice exam and got to where I could get a 100% but never TRULY understood what was going on.  It was more like wrote memorization.


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## Workx

HI,

 Can anyone guide me how to get? I logged into NCEES and I can't find it. 

NEVER MIND: I got it.


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## GordyJ

23and1 said:


> I've downloaded and started going through it. I suppose I'll be one of the lab rats who get to test this out by bringing it with me to the exam in April.


Lab rats unite!


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## Dr. Barber

squaretaper PE said:


> Yowza...If anyone has been following my posts, I think I've said on no fewer than ten occasions I couldn't have survived without the Mollier diagram. This is just yet another reason people should just get the Mollier diagram tattooed on their forearms! :rotflmao:


Yeah, no Mollier diagram which is a major bummer.

However, they did put in some really useful and important stuff such as the charge of an electron, Faraday's constant, and the conversion factor from hectares to acres. ¯\_(ツ)_/¯


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## monty01

PEinIllinois said:


> Yeah, no Mollier diagram which is a major bummer.
> 
> However, they did put in some really useful and important stuff such as the charge of an electron, Faraday's constant, and the conversion factor from hectares to acres. ¯\_(ツ)_/¯


Dude.  You mean you don't have the conversion from hectares to acres memorized?  Fo shame!


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## Dr. Barber

monty01 said:


> Dude.  You mean you don't have the conversion from hectares to acres memorized?  Fo shame!


I don't have it memorized, so I'm lucky they were smart enough to include it. 

I'm also grateful they made some room for these ever useful trig identities. I mean, these are crucial for the P.E. exam:

 ​


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## Audi Driver P.E.

Well, I am sorry to any long time engineers that are going to have to take the CBT. That reference is utter shit. One of the main things that saved me for my exam, was that I could bring along equation formats I was used to, which I can tell you right now were different than many of the things included in the MERM. Some of my undergraduate profs wrote their own texts and used unique terms/terminology that, even though it matched 1:1 (in most cases) with other references, would have required me to relearn what I already knew.

Also, it's a mere 522 pages without any explanations. On my paper/pencil exam there were questions that made you reason out answers based on formula derivations, principles and so forth. I have to assume those are going bye bye? This reference is little more than a collection of equations.

First they did away with subject matter that would require an engineer to be well rounded and now this. What a pile of horse hockey this test is becoming.


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## Ramnares P.E.

Audi driver said:


> Well, I am sorry to any long time engineers that are going to have to take the CBT. That reference is utter shit. One of the main things that save me for my exam, was that I could bring along equation formats I was used to, which I can tell you right now were different than many of the things included in the MERM. Some of my undergraduate profs wrote their own texts and used unique term/terminology that, even though it matched 1:1 (in most cases) with other references would have required me to relearn what I already knew.
> 
> Also, it's a mere 522 pages without any explanations. On my paper/pencil exam there were questions that made you reason out answers based on formula derivations, principles and so forth. I have to assume those are going bye bye? This reference is little more than a collection of equations.
> 
> *First they did away with subject matter that would require an engineer to be well rounded* and now this. What a pile of horse hockey this test is becoming.


Concur with this.  The change from the "general" morning is a detriment to the exam and the introduction of this reference manual is more akin to the FE where you're testing to what's provided and not testing to what is representative of the industry.


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## Dr. Barber

I hope CBT takers never are asked to find the entropy of a saturated liquid-vapor mixture of water at 100 psia.

​


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## Dr. Barber

Simple question:

What is the specific volume of saturated water vapor at 2 psia?

The superheated vapor tables in the handbook have a line for the saturated liquid and one for the saturated vapor. From this table, vg(2 psia) = 192.368 ft3/lb

​




...but the saturated vapor table in the handbook begs to differ:


 ​
The saturation values in the superheated vapor table (6.3.3) are wrong. The right answer by the way is 173.7 ft^3/lbm  confirmed by the table in MERM13 and the NIST ChemistryWeb site. https://webbook.nist.gov/cgi/fluid.cgi?Action=Load&amp;amp;ID=C7732185&amp;amp;Type=SatT&amp;amp;Digits=5&amp;amp;PLow=2&amp;amp;PHigh=2&amp;amp;PInc=1&amp;amp;RefState=DEF&amp;amp;TUnit=F&amp;amp;PUnit=psia&amp;amp;DUnit=lbm%2Fft3&amp;amp;HUnit=Btu%2Flbm&amp;amp;WUnit=m%2Fs&amp;amp;VisUnit=uPa*s&amp;amp;STUnit=N%2Fm


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## YW55

Taking the April 2019 MDM exam and printed out the first 200pgs of this reference manual as a quick reference and have MERM, Kennedy and Shigley's as backups. The MDM section heavily relied on the Shigley book for reference. Went through all the MDM section in the manual line by line to make sure I'm familiar with the material. Nothing surprising on there if you have done section 45 to 60 on MERM.

My weak point will be Quality Control/Statistics so I'll be concentrating on that before the exam.


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## Audi Driver P.E.

Dr. Barber said:


> Simple question:
> 
> What is the specific volume of saturated water vapor at 2 psia?
> 
> The superheated vapor tables in the handbook have a line for the saturated liquid and one for the saturated vapor. From this table, vg(2 psia) = 192.368 ft3/lb
> 
> View attachment 12674​
> ...but the saturated vapor table in the handbook begs to differ:
> 
> View attachment 12675​
> ​
> The saturation values in the superheated vapor table (6.3.3) are wrong. The right answer by the way is 173.7 ft^3/lbm  confirmed by the table in MERM13 and the NIST ChemistryWeb site. https://webbook.nist.gov/cgi/fluid.cgi?Action=Load&amp;amp;ID=C7732185&amp;amp;Type=SatT&amp;amp;Digits=5&amp;amp;PLow=2&amp;amp;PHigh=2&amp;amp;PInc=1&amp;amp;RefState=DEF&amp;amp;TUnit=F&amp;amp;PUnit=psia&amp;amp;DUnit=lbm%2Fft3&amp;amp;HUnit=Btu%2Flbm&amp;amp;WUnit=m%2Fs&amp;amp;VisUnit=uPa*s&amp;amp;STUnit=N%2Fm


I haven't looked. Have they published any errata for this yet?


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## Dr. Barber

Audi driver said:


> I haven't looked. Have they published any errata for this yet?


Not as far as I can tell. I've just sent them a message about these issues with their steam tables.


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## ChooChooEngineer_PE

So I see here that no errata has been posted for the PE ref manual. Don't know if anyone else but me decided to practice with it for the MDM practice test. Page 178, the configuration for the weld you need on the exam problem has b and d flipped. I'm sitting here banging my head against a wall thinking how is it a 1" weld I need? Used the right Ju equation and no problem. has anyone checked the other weld groups for correct Ju formulas? The manual has some nice info and I'd want to use it but if this is wrong, what else is? Thanks in advance.


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## Dr. Barber

ChooChooEngineer said:


> So I see here that no errata has been posted for the PE ref manual. Don't know if anyone else but me decided to practice with it for the MDM practice test. Page 178, the configuration for the weld you need on the exam problem has b and d flipped. I'm sitting here banging my head against a wall thinking how is it a 1" weld I need? Used the right Ju equation and no problem. has anyone checked the other weld groups for correct Ju formulas? The manual has some nice info and I'd want to use it but if this is wrong, what else is? Thanks in advance.


Haven't done a thorough check of the table in page 178, but here it is side by side with its equivalent from Shigley's so you can compare the Ju equations: (the highlighted ones seem different)

From the NCEES Handbook




From Shigley's:


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## Audi Driver P.E.

Folks with an interest in the exam better start piping up to NCEES about this, because this seems like a pretty big Charlie Foxtrot from my vantage point.


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## Dr. Barber

COP for the gas refrigeration cycle (page 265) is wrong.




Here is the correct definition from the Thermodynamics textbook by Cengel and Boles (also, see equation 33.17 in MERM13)


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## Dr. Barber

Audi driver said:


> Folks with an interest in the exam better start piping up to NCEES about this, because this seems like a pretty big Charlie Foxtrot from my vantage point.


I've been sending them the errata I"ve been posting here.


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## Dr. Barber

The clusterfudge continues...

COP for dual-stage vapor compression refrigeration cycle is wrong. The mass flow rate through the low pressure circuit in a dual-stage system is never the same as that of the high pressure circuit. See example 4 in ASHRAE Fundamentals, Section 2.5 "MULTISTAGE VAPOR COMPRESSION REFRIGERATION CYCLES"

The expressions for COP of the system shown in page 264 of the handbook should have the mass flow rates included.

COP_REF_ = m5(h5 - h8)/[m1(h2-h1) + m5(h6-h5)] where m5 = mass flow rate of refrigerant through low pressure circuit and m1 = mass flow rate of refrigerant through high pressure circuit. It looks like the authors of the manual assumed that m5 = m1 to obtain their expression. Like I said, this is wrong.


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## Dr. Barber

*Train wreck city, baby.*

Thermal efficiency of the Otto cycle is wrong:




Compare to Thermo textbook by Cengel and Boles (shown here) or equation 28.42 of MERM13


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## YW55

The entire welding table is a big fail, I couldn't get a practice question right last night and found out why. At this point I'm extremely hesitant on using this as a reference for the April 2019 test coming up.


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## 23and1

Yeah, I've ABSOLUTELY changed my mind about using this reference for the upcoming exam


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## Audi Driver P.E.

23and1 said:


> Yeah, I've ABSOLUTELY changed my mind about using this reference for the upcoming exam


I know I wouldn't use it.


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## Dr. Barber

Dr. Barber said:


> Haven't done a thorough check of the table in page 178, but here it is side by side with its equivalent from Shigley's so you can compare the Ju equations: (the highlighted ones seem different)
> 
> From the NCEES Handbook
> 
> View attachment 12690
> 
> 
> From Shigley's:
> 
> View attachment 12691


I have reviewed this and although the expressions I highlighted here in purple_ appear_ to be different, it turns out they really aren't. Takes some algebra, but it can be shown that they're the same. So, I'm taking this back. Looks like they got this one right.


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## ChooChooEngineer_PE

The galvanic series in it is also off when compared to MARKS and MERM.


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## YW55

For the Johnson's Intermediate columns formula, some references omits the K factor while some references uses K^2 instead of K. I'm confused on which one is the right equation.


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## YW55

Spring Ks factor equation is different than MERM and Kennedy's book. It gets you close enough number though. Makes you wonder which formula NCEES exam makers are using.


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## Ramnares P.E.

YW55 said:


> Spring Ks factor equation is different than MERM and Kennedy's book. It gets you close enough number though. Makes you wonder which formula NCEES exam makers are using.
> 
> View attachment 12748


The Ks defined is the Wahl factor which is well known in the spring manufacturing industry.  Also, refer to Shigley who also defers to the Wahl factor.


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## YW55

Ramnares P.E. said:


> The Ks defined is the Wahl factor which is well known in the spring manufacturing industry.  Also, refer to Shigley who also defers to the Wahl factor﻿.


Which is 




 correct? I'm not sure where the reference manual got the other equation from.


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## Ramnares P.E.

Apologies @YW55, you are correct that equation is the Wahl factor.  The equation in the NCEES manual is the Bergstrasser factor which is a simplified version of the Wahl factor.  

Essentially Shigley says that since the results of the two equations typically differ by 1%, the Bergstrasser (NCEES equation) is preferred.


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## YW55

Ramnares P.E. said:


> Apologies @YW55, you are correct that equation is the Wahl factor.  The equation in the NCEES manual is the Bergstrasser factor﻿ which is a simplified version of the Wahl factor.
> 
> Essentially Shigley says that since the results of the two equations typically differ by 1%, the Bergstrasser (NCEES equation) is preferred.


According to the following link the max difference can be up to 7.5%? I think I'll stick to Wahl factor since the time saved is insignificant.

https://www.chegg.com/homework-help/shigley-s-mechanical-engineering-design-9th-edition-chapter-10-solutions-9780073529288


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## Ramnares P.E.

Those are theoretical problems for students so not sure that 7.5% is valid.  I presume Shigley's statement regarding 1% is from industry experience.


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## MattW

I was looking at the Affinity Laws and page 228 and a couple don't seem to agree with the MERM.  For Q the MERM has the D term to the 3rd power where it is to the first power in the handbook.  For Hp the MERM has the D term to the 5th power where it is to the first power in the handbook.  Those seem wrong to me but I am just starting my studying so I may be missing something.




Also, I cannot fine errata for this handbook.  Is it available on-line somewhere?


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## Dr. Barber

MattW said:


> ...I cannot fine errata for this handbook.  Is it available on-line somewhere?


There is no errata.

I’ve been reporting to NCEES all the typos I’ve listed in this thread. I always get an email saying this [emphasis mine].

”_Thank you for your input. I will forward your questions and concerns to the committee responsible for creating and revising the PE Mechanical Exam Reference Handbook. If there are issues found with the publication, changes will be made on the next version. *NCEES does not publish errata since the handbook is revised frequently*. If no changes occur as a result of reviewing your concerns and questions, no further action will be taken._”

So if it still says “version 1.0” on the cover, none of the typos have been addressed.


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## Vel2018

squaretaper PE said:


> I actually think this might force NCEES to water down the questions. Who really knows...


Hmmmm..I don't think so..You really don't need those huge diagrams. 

What I would suggest is that, during the course of your study, try using the reference material with your desktop! That sucks but it will greatly help you prep for the CBT.


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## ChooChooEngineer_PE

Vel2018 said:


> Hmmmm..I don't think so..You really don't need those huge diagrams.
> 
> What I would suggest is that, during the course of your study, try using the reference material with your desktop! That sucks but it will greatly help you prep for the CBT.


Gotta get that CTRL-F training down when you use the CBT version


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## Audi Driver P.E.

MattW said:


> I was looking at the Affinity Laws and page 228 and a couple don't seem to agree with the MERM.  For Q the MERM has the D term to the 3rd power where it is to the first power in the handbook.  For Hp the MERM has the D term to the 5th power where it is to the first power in the handbook.  Those seem wrong to me but I am just starting my studying so I may be missing something.
> 
> View attachment 12884
> 
> 
> Also, I cannot fine errata for this handbook.  Is it available on-line somewhere?


I'm not seeing the issue. The MERM 13th Ed. p.18-19 agrees with this table.


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## Dr. Barber

Audi driver said:


> I'm not seeing the issue. The MERM 13th Ed. p.18-19 agrees with this table.


Equations 18-45, and 18-47 of MERM13 are valid when you reduce the diameter by trimming the impeller. 

The relationships for changes within a family of geometrically similar pumps are different (I guess trimming the impeller makes the new pump not "geometrically similar" as the original)

Consider Equation 18-52 and set n1=n2 (same speed for both pumps), the result is Q2 = Q1 (D2/D1)^3, which is NOT equation 18-45.

Consider Equation 18-53 and set n1=n2 (same speed for both pumps), the result is P2 = P1 (D2/D1)^5, which is NOT equation 18-47.

This is also done in Fluids textbooks. Here is a screenshot of the book by Munson, Young and Okiishi.

I guess the take-away message is to be careful and make sure to know how is the impeller diameter changing: Is it being trimmed? or is it being replaced by a smaller one, but geometrically similar? The equations can be quite different.


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## Audi Driver P.E.

Dr. Barber said:


> Equations 18-45, and 18-47 of MERM13 are valid when you reduce the diameter by trimming the impeller.
> 
> The relationships for changes within a family of geometrically similar pumps are different (I guess trimming the impeller makes the new pump not "geometrically similar" as the original)
> 
> Consider Equation 18-52 and set n1=n2 (same speed for both pumps), the result is Q2 = Q1 (D2/D1)^3, which is NOT equation 18-45.
> 
> Consider Equation 18-53 and set n1=n2 (same speed for both pumps), the result is P2 = P1 (D2/D1)^5, which is NOT equation 18-47.
> 
> This is also done in Fluids textbooks. Here is a screenshot of the book by Munson, Young and Okiishi.
> 
> I guess the take-away message is to be careful and make sure to know how is the impeller diameter changing: Is it being trimmed? or is it being replaced by a smaller one, but geometrically similar? The equations can be quite different.
> 
> View attachment 12957


Equations 18.49 thru 18.54 are Pump Similarity laws, not Pump Affinity laws. The Handbook table being discussed shows equations for Pump Affinity laws. And the table is correct.


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## Dr. Barber

Audi driver said:


> Equations 18.49 thru 18.54 are Pump Similarity laws, not Pump Affinity laws. The Handbook table being discussed shows equations for Pump Affinity laws. And the table is correct.


Agreed. I haven’t said they’re wrong.

I guess I was “thinking out loud” and figuring out when to use similarity and when to use affinity. Still not clear.


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## Audi Driver P.E.

Dr. Barber said:


> Agreed. I haven’t said they’re wrong.
> 
> I guess I was “thinking out loud” and figuring out when to use similarity and when to use affinity. Still not clear.


Knowing when to use the similarity laws vice affinity laws is important for the exam, to be sure. Generally speaking if you have more than 1 parameter changing at a time (propeller diameter and shaft speed, for example) you need to use the similarity laws.

Note: the MERM seems to suggest the word "homologous" is something to key on. I wouldn't bet on that for the PE exam, but it is applicable.


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## Dr. Barber

Audi driver said:


> Knowing when to use the similarity laws vice affinity laws is important for the exam, to be sure. Generally speaking if you have more than 1 parameter changing at a time (propeller diameter and shaft speed, for example) you need to use the similarity laws.
> 
> Note: the MERM seems to suggest the word "homologous" is something to key on. I wouldn't bet on that for the PE exam, but it is applicable.


Some more clarification:

https://www.eng-tips.com/viewthread.cfm?qid=89032


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## Atf TX

Anyone taking the October 2019 exam, this would be a handy reference book that you could use, in addition to other resources.


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## Audi Driver P.E.

Atf TX said:


> Anyone taking the October 2019 exam, this would be a handy reference book that you could use, in addition to other resources.


If you correct all the errors in it, yes.


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## Mechanical Ryan

500 plus pages hehehe


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## YW55

Atf TX said:


> Anyone taking the October 2019 exam, this would be a handy reference book that you could use, in addition to other resources.


Used it for my April 2019 MDM exam and passed. You just have to practice with it and all the errors will come up and you can correct it. Think of it as a treasure hunt.


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## cjcarter

I went over the reference manual, having taken the October 2019 pe exam, i am convinced that NCEES will be changing the type of questions asked for the CBT style exam due to some of the 2019 October exam questions not being covered by the reference manual. Besides the computer glitches ( the screen may freeze or load slowly while scrolling down) and using a marker on a plastic pad, the CBT style exams should be easier. I don’t think they can ask a question outside the reference manual. You can use that to your advantage.


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## TX_PE_Oct19

asu said:


> I went over the reference manual, having taken the October 2019 pe exam, i am convinced that NCEES will be changing the type of questions asked for the CBT style exam due to some of the 2019 October exam questions not being covered by the reference manual. Besides the computer glitches ( the screen may freeze or load slowly while scrolling down) and using a marker on a plastic pad, the CBT style exams should be easier. I don’t think they can ask a question outside the reference manual. You can use that to your advantage.


True. However they may ask questions outside the reference manual. It clearly stated on the front page of the manual that It may not be sufficient to solve all the questions. So basically they still CAN/MAY ask anything they want and no one can argue with it. Sorry...


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## cjcarter

TX_PE_Oct19 said:


> True. However they may ask questions outside the reference manual. It clearly stated on the front page of the manual that It may not be sufficient to solve all the questions. So basically they still CAN/MAY ask anything they want and no one can argue with it. Sorry...


*Asking questions outside of the reference manual WAS only valid for the April 2019 and October 2019 exams as shown below; *

_Using the Handbook for the April and October 2019 Paper Exams
The Principles and Practice of Engineering (PE) Mechanical exam is an open-book pencil-and-paper exam through October
2019. The PE Mechanical Reference Handbook is a reference you may use on exam day. It contains charts, formulas, tables, and
other information that may help you answer questions on the PE Mechanical exam. However, it does not contain all information
required to answer every question; theories, conversions, formulas, and definitions that examinees are expected to know have
not been included.
This PE Mechanical Reference Handbook is intended solely for use on the NCEES PE Mechanical exam. You may bring your
personal copy of the Handbook into the exam room as long as it is bound and remains bound according to the policies in the
NCEES Examinee Guide. Additional references that adhere to policies in the Examinee Guide are allowed in the exam room for
the April and October 2019 exam._

*If you read it that is the case only for the April and October 2019 Paper exams.*

*For the computer based exam it says the following; *

_Using the Handbook for the April 2020 Computer-Based Exam
Beginning in April 2020, the PE Mechanical exam will be computer-based, and the PE Mechanical Reference Handbook will
be the only resource material you may use during the exam. Reviewing it before exam day will help you become familiar with
reference information provided. You will not be allowed to bring a copy of the Handbook into the exam room. Instead, the
computer-based exam will include a PDF version of the Handbook for your use. The PE Mechanical Reference Handbook is
intended solely for use on the NCEES PE Mechanical exam._


----------



## Edgy Cheesy Graphite PE

asu said:


> *Asking questions outside of the reference manual WAS only valid for the April 2019 and October 2019 exams as shown below; *
> 
> _Using the Handbook for the April and October 2019 Paper Exams
> The Principles and Practice of Engineering (PE) Mechanical exam is an open-book pencil-and-paper exam through October
> 2019. The PE Mechanical Reference Handbook is a reference you may use on exam day. It contains charts, formulas, tables, and
> other information that may help you answer questions on the PE Mechanical exam. However, it does not contain all information
> required to answer every question; theories, conversions, formulas, and definitions that examinees are expected to know have
> not been included.
> This PE Mechanical Reference Handbook is intended solely for use on the NCEES PE Mechanical exam. You may bring your
> personal copy of the Handbook into the exam room as long as it is bound and remains bound according to the policies in the
> NCEES Examinee Guide. Additional references that adhere to policies in the Examinee Guide are allowed in the exam room for
> the April and October 2019 exam._
> 
> *If you read it that is the case only for the April and October 2019 Paper exams.*
> 
> *For the computer based exam it says the following; *
> 
> _Using the Handbook for the April 2020 Computer-Based Exam
> Beginning in April 2020, the PE Mechanical exam will be computer-based, and the PE Mechanical Reference Handbook will
> be the only resource material you may use during the exam. Reviewing it before exam day will help you become familiar with
> reference information provided. You will not be allowed to bring a copy of the Handbook into the exam room. Instead, the
> computer-based exam will include a PDF version of the Handbook for your use. The PE Mechanical Reference Handbook is
> intended solely for use on the NCEES PE Mechanical exam._


That says that the Mechanical Reference Handbook is the only reference you're allowed to use and will be provided electronically, but I don't read anything that says that *everything* you need to know is contained in it. I'm sure NCEES can ask whatever they want including questions that may be outside the scope of the provided reference.


----------



## cjcarter

jean15paul_PE said:


> That says that the Mechanical Reference Handbook is the only reference you're allowed to use and will be provided electronically, but I don't read anything that says that *everything* you need to know is contained in it. I'm sure NCEES can ask whatever they want including questions that may be outside the scope of the provided reference.


Then what is the purpose of the given reference manual versus bringing your own material? They can still do computer based exams and let you bring your own material. It doesn't make sense to me.


----------



## Edgy Cheesy Graphite PE

asu said:


> Then what is the purpose of the given reference manual versus bringing your own material? They can still do computer based exams and let you bring your own material. It doesn't make sense to me.


That is a good question. My guess, easier administration. They can allow any CBT center to administer the test with little-to-no special training.

If you allow people to bring their own materials then you need proctors to know what is and isn't allowed (e.g. it needs to be bound; staples don't count; are handwritten references ok; pencil or pen; etc). Also you have to worry about testers writing down problems, so proctors have to be constantly paying attention.

With only the electronic reference allowed, it doesn't matter what you do while you're testing as long as you enter and exit empty handed.


----------



## cjcarter

jean15paul_PE said:


> That is a good question. My guess, easier administration. They can allow any CBT center to administer the test with little-to-no special training.
> 
> If you allow people to bring their own materials then you need proctors to know what is and isn't allowed (e.g. it needs to be bound; staples don't count; are handwritten references ok; pencil or pen; etc). Also you have to worry about testers writing down problems, so proctors have to be constantly paying attention.
> 
> With only the electronic reference allowed, it doesn't matter what you do while you're testing as long as you enter and exit empty handed.


I refuse to believe NCEES can ask questions which requires equations or conversions outside of the reference manual to be solved. Some questions may not need equations but common knowledge on the subject but numerical questions should be covered by the equations shown in the reference manual. Maybe ChemE and other disciplines taking the CBT exam can shed a light over this.


----------



## TX_PE_Oct19

There are some questions in the exam just to take your time and stress you out. Those questions designed to test your ability to pass, don't be stress, using your time efficiently, etc. So, IF they ask something out of the reference manual (probably a few) you need to identify it, pass it, If you have extra time at the end of the exam you may use your engineering judgment to solve/guess it to some extent.

So, yes I still believe that they can (and probably will) ask some questions off-scope of the provided reference manual. I may be wrong but this is how I interpret these type of exams, not only the PE.


----------



## Edgy Cheesy Graphite PE

asu said:


> I refuse to believe NCEES can ask questions which requires equations or conversions outside of the reference manual to be solved. Some questions may not need equations but common knowledge on the subject but numerical questions should be covered by the equations shown in the reference manual. Maybe ChemE and other disciplines taking the CBT exam can shed a light over this.


Maybe you're right. I can't say that I know. I'd be curious to hear from some ChemE's also.

But IMO ... the thinking that "Every equation is in the book; I just need to find it and use it." sounds like a very FE thought process. The PE exam is testing _*you*_, your years of experience and your engineering _knowledge_. You have to know your shit. There are definitely problems that I'd describe as, "If you're going to call yourself a PE then you should know this, with or without a reference."
There's some stuff that a PE needs to know. There's other stuff that no one would be expected to remember.

Also keep in mind how the cut score is determined. The question that NCEES asks is "what percentage of competent PEs should be able to answer this question?" and then questions are weighted based on that (subjective) percentage. No one is expected to know everything. You don't have to score 100%. The expectation of how many people could answer is built into the scoring.


----------



## cjcarter

jean15paul_PE said:


> Maybe you're right. I can't say that I know. I'd be curious to hear from some ChemE's also.
> 
> But IMO ... the thinking that "Every equation is in the book; I just need to find it and use it." sounds like a very FE thought process. The PE exam is testing _*you*_, your years of experience and your engineering _knowledge_. You have to know your shit. There are definitely problems that I'd describe as, "If you're going to call yourself a PE then you should know this, with or without a reference."
> There's some stuff that a PE needs to know. There's other stuff that no one would be expected to remember.
> 
> Also keep in mind how the cut score is determined. The question that NCEES asks is "what percentage of competent PEs should be able to answer this question?" and then questions are weighted based on that (subjective) percentage. No one is expected to know everything. You don't have to score 100%. The expectation of how many people could answer is built into the scoring.


I wish that was the case but the PE exam is far away from needing the industry experience or testing your knowledge over it. For example most of the engineers that I worked with took it right after their FE exam without any experience. They took it when they were graduating. State of IL allows that. The questions are mostly basic questions but need to know what equation to use quickly and where to find them. It gets tricky when NCEES decides to change the exam formatting or doesn't stick with their own exam specifications. If the goal is to make it harder for the test takers, might as well also limit the licenses to people with MS, MENG or PHD degrees.


----------



## Ramnares P.E.

asu said:


> I wish that was the case but the PE exam is far away from needing the industry experience or testing your knowledge over it. For example most of the engineers that I worked with took it right after their FE exam without any experience. They took it when they were graduating. State of IL allows that. The questions are mostly basic questions but need to know what equation to use quickly and where to find them. It gets tricky when NCEES decides to change the exam formatting or doesn't stick with their own exam specifications. If the goal is to make it harder for the test takers, might as well also limit the licenses to people with *MS, MENG* or PHD degrees.


There are some who advocate for this and may not be an entirely bad idea.


----------



## OldSquaw

Has anyone noticed that table 1.2.1 Properties of Air at Atmospheric Pressure, the columns for Kinematic and Absolute Viscosity seem off? Nothing seems to match what I am getting using NIST Refprop. 

From what I can tell, it looks like the table says "centistokes" for kinematic viscosity but it should say "ft^2/sec" if the numbers are to be correct in the table. As for the absolute viscosity, they said "centipoise" but the numbers are for lbf-sec/ft^2.


----------



## Dr. Barber

OldSquaw said:


> Has anyone noticed that table 1.2.1 Properties of Air at Atmospheric Pressure, the columns for Kinematic and Absolute Viscosity seem off? Nothing seems to match what I am getting using NIST Refprop.
> 
> From what I can tell, it looks like the table says "centistokes" for kinematic viscosity but it should say "ft^2/sec" if the numbers are to be correct in the table. As for the absolute viscosity, they said "centipoise" but the numbers are for lbf-sec/ft^2.


Agree with you 100%,
I will be adding this to my long list of errata and email them about it.


----------



## OldSquaw

Dr. Barber said:


> Agree with you 100%,
> I will be adding this to my long list of errata and email them about it.


Thanks for your help Dr. Barber. I'll post here as I continue to find errors in this manual.


----------



## OldSquaw

Has anyone else tried to solve problems using the psychrometric chart in the reference manual? I tried using only the chart in the PDF, since that's all I will have on exam day. It's almost impossible to use, especially if you have to use the sensible heat ratio. Hopefully they will present the questions in a way that the PDF can actually be used. I just can't seem to use this chart without drawing on it and using a straight edge.


----------



## Dr. Barber

OldSquaw said:


> Has anyone else tried to solve problems using the psychrometric chart in the reference manual? I tried using only the chart in the PDF, since that's all I will have on exam day. It's almost impossible to use, especially if you have to use the sensible heat ratio. Hopefully they will present the questions in a way that the PDF can actually be used. I just can't seem to use this chart without drawing on it and using a straight edge.


It’s a complete train wreck. You have to zoom in to get decent resolution of the lines, but when you do so, the humidity and dry bulb axes are off-screen. Like wtf?

It would be ridiculous if a question requires using the SHR protractor. I guess you’d have to use the miniature white board as a ruler.


----------



## OldSquaw

Table 6.2 on page 284, Flow Rate of Steam in Sch. 40 Pipe does not have any units for the flow. I know it's lb/hr, but it doesn't say that anywhere.


----------



## OldSquaw

Pages 381,382,383,385,386,387,389,390,391,393,394,395,397,398,399,401,402,403 Property charts for R22, R123, R134a, R410a, R717, R1234yf all have Enthalpy in units of Btu/lb-F. This is a typo and should read Btu/lb.


----------



## OldSquaw

Also just in case anyone was curious, I have been studying for the exam using the online "learning hub" through PPI. It's an online database of practice problems, quizzes, and books. I have also found several errors in these practice problems. Most of the errors are in the solutions to the problems. I haven't been using this resource very long either. It is extremely frustrating to study for the exam using a reference manual and practice problems that are both filled with errors. I'm really starting to think this whole new format is a complete joke.


----------



## Edgy Cheesy Graphite PE

OldSquaw said:


> Also just in case anyone was curious, I have been studying for the exam using the online "learning hub" through PPI. It's an online database of practice problems, quizzes, and books. I have also found several errors in these practice problems. Most of the errors are in the solutions to the problems. I haven't been using this resource very long either. It is extremely frustrating to study for the exam using a reference manual and practice problems that are both filled with errors. I'm really starting to think this whole new format is a complete joke.


To be fair, there are lots of errors in the MERM and in the old NCEES practice exam. ... and in every other thing every published. But they have been around a long time so (1) many errors have been corrected during multiple revisions, and (2) erratas are readily available. Eventually these newer resources will catch up. But I feel what you're saying, it kinda sucks to be the gen1 guinea pig.


----------



## Audi Driver P.E.

OldSquaw said:


> Also just in case anyone was curious, I have been studying for the exam using the online "learning hub" through PPI. It's an online database of practice problems, quizzes, and books. I have also found several errors in these practice problems. Most of the errors are in the solutions to the problems. I haven't been using this resource very long either. It is extremely frustrating to study for the exam using a reference manual and practice problems that are both filled with errors. I'm really starting to think this whole new format is a complete joke.


Look at it this way. If you're able to discern why the problem solution is wrong, you're probably going to do OK on the exam.


----------



## Dr. Barber

The unit conversion table in page 2 erroneously has the viscosity unit "reyn" as equal to 1 lb-ft/s^2 where it should be 1 lbf-s/in^2.


----------



## Dr. Barber

Ok, I welcome any clarification and pointing out what I'm doing wrong here. If I'm not making any dumb mistakes, then this is further proof that this handbook is an unmitigated disaster.

Consider this simple question: What is the dynamic viscosity of SAE 50 oil at 50C?

If we use the graph in page 10, we get... what do we get? I have no idea. is this 4.5? 45? 450?

Note there is a 10^2 below the horizontal red line and another 10^2 above the red line. At first I thought the 10^2 below was a typo and should be just 10, but there is already a 10 further below. So, ¯\_(ツ)_/¯




Then I thought I could use the imperial units graph of page 9. Going in there at 122F (50C) I get 16 reyn, which is 1.1x10^8 mPa*s which is nowhere near anything close you could get from the SI chart.  So, yeah, unless I'm doing something really wrong, this is REALLY screwed up.


----------



## Edgy Cheesy Graphite PE

Dr. Barber said:


> The unit conversion table in page 2 erroneously has the viscosity unit "reyn" as equal to 1 lb-ft/s^2 where it should be 1 lbf-ft/s^2.


Well. I'm old school solid mechanics guy....
lb ALWAYS means lbf. lbm is a unit for mass that I personally hate and never use because gc is evil. 
SLUGS 4 LIFE!!!!

But I know that's not how yall thermal-fluids engineers think.


----------



## Dr. Barber

jean15paul_PE said:


> Well. I'm old school solid mechanics guy....
> lb ALWAYS means lbf. lbm is a unit for mass that I personally hate and never use because gc is evil.
> SLUGS 4 LIFE!!!!
> 
> But I know that's not how yall thermal-fluids engineers think.




 That's the kicker with this manual. They use lb, lbf and lbm. Sometimes by "lb" they mean "lbm" and sometimes they mean "lbf". I mean, this thing is just a real hoot.


----------



## Audi Driver P.E.

Dr. Barber said:


> Ok, I welcome any clarification and pointing out what I'm doing wrong here. If I'm not making any dumb mistakes, then this is further proof that this handbook is an unmitigated disaster.
> 
> Consider this simple question: What is the dynamic viscosity of SAE 50 oil at 50C?
> 
> If we use the graph in page 10, we get... what do we get? I have no idea. is this 4.5? 45? 450?
> 
> Note there is a 10^2 below the horizontal red line and another 10^2 above the red line. At first I thought the 10^2 below was a typo and should be just 10, but there is already a 10 further below. So, ¯\_(ツ)_/¯
> 
> View attachment 14551
> 
> 
> Then I thought I could use the imperial units graph of page 9. Going in there at 122F (50C) I get 16 reyn, which is 1.1x10^8 mPa*s which is nowhere near anything close you could get from the SI chart.  So, yeah, unless I'm doing something really wrong, this is REALLY screwed up.
> 
> View attachment 14552


What a Charlie Foxtrot.  First of all, at 50C, SAE 50 Oil would be about 97 *mPa-s*, which is 14.1E-6 Reyn. So the first chart would (apparently???) indicate a value of 45 (to be in the correct ballpark for factors of 10), but that corresponds to the _actual_ value for SAE 30 oil (from other references I have). If you look at the Imperial units graph, you will note that it properly has a mu symbol (indicated on the Y axis label) but for some reason there is a comma between that and reyn. That chart is closer to correct, value-wise, for micro reyn. If you use a value of 16 micro reyn, you get about 110 *mPa-s*, which is closer to the actual value. I don't know how to read that first chart. On your exam, I would use the second chart, convert, and call it a day.


----------



## OldSquaw

Here's another issue I found:


----------



## Dr. Barber

Audi driver said:


> What a Charlie Foxtrot.  First of all, at 50C, SAE 50 Oil would be about 97 *mPa-s*, which is 14.1E-6 Reyn. So the first chart would (apparently???) indicate a value of 45 (to be in the correct ballpark for factors of 10), but that corresponds to the _actual_ value for SAE 30 oil (from other references I have). If you look at the Imperial units graph, you will note that it properly has a mu symbol (indicated on the Y axis label) but for some reason there is a comma between that and reyn. That chart is closer to correct, value-wise, for micro reyn. If you use a value of 16 micro reyn, you get about 110 *mPa-s*, which is closer to the actual value. I don't know how to read that first chart. On your exam, I would use the second chart, convert, and call it a day.


Thanks. I hadn't noticed the "mu" -- good catch. Yeah, what a sh*t show. That first chart is useless. In their defense, they do provide a reference to where the chart came from. Maybe it's messed up in the original source and they just copied it.  It shows, however, that nobody who is participating in the creation of this manual has used the dang chart.


----------



## Dr. Barber

OldSquaw said:


> Here's another issue I found:
> 
> View attachment 14678


LOL

JFC


----------



## OldSquaw

Dr. Barber,

Are you reporting all of this to NCEES? I haven't reported anything in hopes that you were, lol! If you're already doing this then I won't bother.

I'm one of the poor people that is taking the exam in April with this reference.


----------



## Dr. Barber

Yes.

I have reported most of the things in this thread to them. Not this latest set of findings, but I will get around to it probably this weekend.


----------



## OldSquaw

Awesome! Thanks!


----------



## Audi Driver P.E.

@EB NCEES REP, not sure if you have any sway over this or not (I kiiiiiiinda doubt it), but worth the tag, probably. This exam booklet is a total Charlie Foxtrot.


----------



## OldSquaw

5.2.2 Transient conduction using lumped capacitance model:

The reference manual says to use units for thermal conductivity in Btu-in/hr-ft^2-F in the equation for Biot number. If you use the rest of the units they suggest, the units don't work out. Should be in Btu/hr-ft-F.

It would be better if they just said nothing regarding the units and let the test taker work out the units on their own. When they state which units to use, it makes you think that you can use those units...but they yield the wrong answer.


----------



## OldSquaw

Guys,

FYI, I just logged into my account and noticed there is a version 1.1 out. I haven't looked through it yet but I'm thinking they've probably addressed some of the issues.

I just skimmed through the new reference manual and all the refrigerant properties charts still have units of Btu/lb-F for enthalpy...

Rather than fixing the equation for two stage refrigeration cycle COP they just put "FOR EQUAL MASS FLOW RATES IN STAGES 1 AND 2"


----------



## Dr. Barber

OldSquaw said:


> Rather than fixing the equation for two stage refrigeration cycle COP they just put "FOR EQUAL MASS FLOW RATES IN STAGES 1 AND 2"


LOL WHAT?!?!?!?!?! 

OMG the mass flow rates in the two stages can never be the same.

Energy conservation in the intercooler requires: 

m6h6 + m4h4 = m1h1 + m7h7. (assuming a well-insulated chamber)

Now let m_highP = m1 = m4 and m_lowP = m6 = m7. Put these in the energy balance to obtain:

m_lowP (h6 - h7) = m_highP (h1 - h4) thus the mass flow ratio is:

m_lowP/m_highP = (h1-h4)/(h6-h7)

Look now in the P-h diagram for the cycle to see that the ratio (h1-h4)/(h6-h7) is ALWAYS &lt; 1 and can never be 1.

I'm speechless.


----------



## Dr. Barber

Looks like in the new version 1.1, they fixed the efficiency of the Otto cycle and the COP of the gas refrigeration cycle.


----------



## OldSquaw

Dr. Barber said:


> LOL WHAT?!?!?!?!?!
> 
> OMG the mass flow rates in the two stages can never be the same.
> 
> Energy conservation in the intercooler requires:
> 
> m6h6 + m4h4 = m1h1 + m7h7. (assuming a well-insulated chamber)
> 
> Now let m_highP = m1 = m4 and m_lowP = m6 = m7. Put these in the energy balance to obtain:
> 
> m_lowP (h6 - h7) = m_highP (h1 - h4) thus the mass flow ratio is:
> 
> m_lowP/m_highP = (h1-h4)/(h6-h7)
> 
> Look now in the P-h diagram for the cycle to see that the ratio (h1-h4)/(h6-h7) is ALWAYS &lt; 1 and can never be 1.
> 
> I'm speechless.
> 
> View attachment 14809


I agree. This is pretty concerning to me as a test taker.


----------



## Dr. Barber

Dr. Barber said:


> I hope CBT takers never are asked to find the entropy of a saturated liquid-vapor mixture of water at 100 psia.
> 
> View attachment 12668​


They fixed this too.


----------



## Dr. Barber

Definition of hydraulic radius, RH, and hydraulic diameter, DH, are wrong. They are saying RH = (1/2)*A/P where A=flow area and P=wetted perimeter. They are also saying DH, = RH/2)

 ​
But in reality, RH = A/P and RH, = DH/4 as shown in these 2 different sources: 

*1. MERM13:*




*2. Fluid Mechanics by Cengel and Cimbala:*


----------



## Dr. Barber

So, this should be a "4" instead of a "2"


----------



## Dr. Barber

After shitting on them so much, I figured it's time to throw them some love.  The Moody chart in the manual has a secondary horizontal axis for the product of the flow velocity in fps and the pipe ID in inches.  This is nice because with this you don't have to look up viscosity and calculate the Reynolds number.  It's a time saver for sure...

I spot-checked a couple of values and it works.  Now, this works only for 60F water so if a problems says its another fluid or its water at like 150F then this shortcut will not work well.


----------



## Dr. Barber

The line for f=0.022 is partially missing.


----------



## OldSquaw

Dr. Barber said:


> The line for f=0.022 is partially missing.
> 
> View attachment 15619


Thanks for letting us know! I've been studying and haven't found anymore major problems lately.


----------



## OldSquaw

3.9.2,  Properties of Aqueous Solutions of Ethylene Glycol:

Units for specific heat are in Btu-°F/lb

thermal conductivity is in Btu-ft-°F/hr-ft^2

This error is on all of the glycol charts including the propylene glycol charts.

There's still data missing from the steam tables.

Table 9.1.15 has thermal conductivity in units of Btu-in/hr-ft^3-°F. They screwed up the units in note a on the same page too.

Looks like someone needs a lesson in units!


----------



## Dr. Barber

The analytical expression to calculate enthalpy of moist air is wrong


This is the correct one, from ASHRAE Handbook of Fundamentals


----------



## Dr. Barber

Analytical expression to calculate humidity ratio at saturation is wrong:




The correct expression, from ASHRAE Handbook of Fundamentals:


----------



## Audi Driver P.E.

@Dr. Barber I assume any new errors you post here are from the updated manual?


----------



## Dr. Barber

Audi driver said:


> @Dr. Barber I assume any new errors you post here are from the updated manual?


Correct. Version 1.1


----------



## OldSquaw

I'm certainly not a vibration expert, but the equation for transmissibilty in 2.15.3 appears to have an extra r^2 term.

Can someone check me on that?


----------



## Dr. Barber

OldSquaw said:


> I'm certainly not a vibration expert, but the equation for transmissibilty in 2.15.3 appears to have an extra r^2 term.
> 
> Can someone check me on that?


I'm no expert either, but I agree with you. Screenshot of NCEES manual and of MERM13 for comparison: 




MERM13:


----------



## DKS

OldSquaw said:


> I'm certainly not a vibration expert, but the equation for transmissibilty in 2.15.3 appears to have an extra r^2 term.
> 
> Can someone check me on that?


@OldSquaw and @Dr. Barber

I believe that the equation for transmissibilty in 2.15.3 appears is correct as it is for force transmitted _due to base excitation_, rather than for force applied to an oscillating mass (through, for example, rotating unbalance).

An equation that is equivalent to 60.55/60.56 from MERM13 appears on page 691 (equation 9.94) of the Fourth Edition of Mechanical Vibrations by S.S. Rao for force applied to an oscillating mass, whereas an equation that is equivalent to the equation that appears in Section 2.15.3 of the NCEES manual appears on page 241 (equation 3.74) of the Fourth Edition of Mechanical Vibrations by S.S. Rao for base excitation.

Basically both the equations in the NCESS manual and MERM13 are correct, but are used for two different methods of exciting the mass.

Hope that helps.


----------



## Dr. Barber

DKS said:


> @OldSquaw and @Dr. Barber
> 
> I believe that the equation for transmissibilty in 2.15.3 appears is correct as it is for force transmitted _due to base excitation_, rather than for force applied to an oscillating mass (through, for example, rotating unbalance).
> 
> An equation that is equivalent to 60.55/60.56 from MERM13 appears on page 691 (equation 9.94) of the Fourth Edition of Mechanical Vibrations by S.S. Rao for force applied to an oscillating mass, whereas an equation that is equivalent to the equation that appears in Section 2.15.3 of the NCEES manual appears on page 241 (equation 3.74) of the Fourth Edition of Mechanical Vibrations by S.S. Rao for base excitation.
> 
> Basically both the equations in the NCESS manual and MERM13 are correct, but are used for two different methods of exciting the mass.
> 
> Hope that helps.


Ah, ok. Gotcha.


----------



## Dr. Barber

Section 5.2, units of thermal resistance are wrong.

The units they specify in 5.2.1 (which I highlighted in blue here) are actually units of R-value, which is NOT the same as thermal resistance.


----------



## Dr. Barber

Section 5.2.4, the equation for fin heat transfer rate is not correct. If there is negligible heat transfer from the tip, then you use the actual fin length _L_, not the corrected length _L_c. The corrected length is used when calculating fin heat transfer rate for a tip with convection at the tip.

Also, if you use the units for thermal conductivity as specified here, the equation needs a "12" somewhere, or better yet, the units for _k_ should be specified as (Btu/h)/(ft F) and not as (Btu/h) in/(ft^2 F).


----------



## Audi Driver P.E.

Dr. Barber said:


> Section 5.2.4, the equation for fin heat transfer rate is not correct. If there is negligible heat transfer from the tip, then you use the actual fin length _L_, not the corrected length _L_c. The corrected length is used when calculating fin heat transfer rate for a tip with convection at the tip.
> 
> Also, if you use the units for thermal conductivity as specified here, the equation needs a "12" somewhere, or better yet, the units for _k_ should be specified as (Btu/h)/(ft F) and not as (Btu/h) in/(ft^2 F).
> 
> View attachment 16008


I have never seen those equations in such an odd form.  Yikes.


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## Dr. Barber

Audi driver said:


> I have never seen those equations in such an odd form.  Yikes.


Actually, that's how I've always seen them. Here are snapshots from the heat transfer book by Cengel and from Incropera. The NCEES manual is wrong though, in the use of _L_c for the case of negligible heat transfer at the tip.


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## Dr. Barber

The correlation for the Nusselt number for constant wall temperature, laminar, fully developed flow is wrong. As shown in the attachment, they have _Nu_ = 4.66 and it should be _Nu_ = 3.66. I am attaching screenshots from two different heat transfer textbooks to show the correct one. Furthermore, this correlation (as well as the one for constant wall heat flux; _Nu_=4.36) are valid for fully developed flow only, but the manual does not give the correlations for the entry length, which one needs in order to figure out if the flow is fully developed. ¯\_(ツ)_/¯ 




Textbook by Incropera et al:


 

Textbook by Cengel:


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## Dr. Barber

When using _Q_=_UAF_ΔTlm for a "complex" heat exchanger the LMTD is the one as defined for the simple counter-flow tube-in-tube heat exchanger.  The NCEES manual does not specify this. Also, what's the deal with using 2.3 log10(x) instead of ln(x)? I mean, I know it's the same thing, but do they think the approved calculators don't have keys for natural log?


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## Dr. Barber

Typo in one of the radiation heat transfer equations:


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## OldSquaw

Dr. Barber said:


> Typo in one of the radiation heat transfer equations:
> 
> View attachment 16078
> 
> 
> View attachment 16079


Dr Barber NCEES seriously needs to pay you for single handedly fixing their screwed up reference manual.

Are you an under cover secret NCEES agent ?


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## Dr. Barber

OldSquaw said:


> Dr Barber NCEES seriously needs to pay you for single handedly fixing their screwed up reference manual.
> 
> Are you an under cover secret NCEES agent ?


LOL

 I’m a developer of technical content for @Slay the P.E.. Re-writing all the problems so they can be solved using only the handbook has been... an adventure.
 

Having said that, I’m never acting in an “official” capacity when I’m snarky or when I use profanity and sarcasm


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## Edgy Cheesy Graphite PE

Dr. Barber said:


> LOL
> 
> I’m a developer of technical content for @Slay the P.E.. Re-writing all the problems so they can be solved using only the handbook has been... an adventure.
> 
> 
> Having said that, I’m never acting in an “official” capacity when I’m snarky or when I use profanity and sarcasm


I know you're doing your work and working to improve @Slay the P.E.'s course content.

But (I'm sure you realized this) you're doing a HUGE favor to mechanical engineers everywhere by submitting these errors to NCEES. 

... I wish/hope someone on the MDM side is getting this deep into finding errors.


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## Audi Driver P.E.

jean15paul_PE said:


> I know you're doing your work and working to improve @Slay the P.E.'s course content.
> 
> But (I'm sure you realized this) you're doing a HUGE favor to mechanical engineers everywhere by submitting these errors to NCEES.
> 
> ... I wish/hope someone on the MDM side is getting this deep into finding errors.


Exactly. I would be terrified right now if I had to take the exam using that text.


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## OldSquaw

Audi driver said:


> Exactly. I would be terrified right now if I had to take the exam using that text.


Luckily I'm taking the HVAC&amp;R test. From what I can tell, it looks like most of the major issues have been reported and should be fixed soon (for the HVAC&amp;R and probably most of the thermal and fluids stuff). The other key is knowing how to solve problems using (aka not using) this reference manual. I have learned my lesson to ALWAYS check my units and never use the "convenient" equations from the reference manual where the units have been "worked out for you." They are usually wrong.

Hopefully the problems and solutions on the real test are not based on the screwed up reference manual. Because then you could potentially get a problem technically correct but incorrect according to NCEES.


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## Audi Driver P.E.

I simply don't see how the exam could be designed to be solved using the reference NCEES has published. To create exam questions, they would certainly have to vet out the problem solution given only the information in the booklet. Either the correct answer will actually be an incorrect answer or the solution will actually require additional information not in the booklet.


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## Edgy Cheesy Graphite PE

Audi driver said:


> I simply don't see how the exam could be designed to be solved using the reference NCEES has published. To create exam questions, they would certainly have to vet out the problem solution given only the information in the booklet. Either the correct answer will actually be an incorrect answer or the solution will actually require additional information not in the booklet.


They specifically say that the solutions _could_ require additional information not in the booklet.


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## Audi Driver P.E.

jean15paul_PE said:


> They specifically say that the solutions _could_ require additional information not in the booklet.


And when info conflicts, then what?


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## OldSquaw

Audi driver said:


> I simply don't see how the exam could be designed to be solved using the reference NCEES has published. To create exam questions, they would certainly have to vet out the problem solution given only the information in the booklet. Either the correct answer will actually be an incorrect answer or the solution will actually require additional information not in the booklet.


I’m not sure if this is any help to anyone but I managed to score an 83% on the NCEES practice exam using only the NCEES reference manual. The practice exam is the same as the one that you were allowed to use your own references on. So the new reference manual can be used with some success.


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## OldSquaw

I've noticed a recurring error in the PPI practice problems where in the solution to the problem they multiply lbm by the acceleration to get lbf. They neglect to divide by g_c. This error is on every problem that I have encountered where you have to convert lbm to lbf. I just solved a problem, and got it "wrong" of course. Only to find out that according to PPI, a 100lbm object weighs 3,220 lbf on earth.

The whole concept of lbm is completely stupid, but they should at least use it correctly.


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## Edgy Cheesy Graphite PE

OldSquaw said:


> I've noticed a recurring error in the PPI practice problems where in the solution to the problem they multiply lbm by the acceleration to get lbf. They neglect to divide by g_c. This error is on every problem that I have encountered where you have to convert lbm to lbf. I just solved a problem, and got it "wrong" of course. Only to find out that according to PPI, a 100lbm object weighs 3,220 lbf on earth.
> 
> *The whole concept of lbm is completely stupid, *but they should at least use it correctly.


Spoken like a true MDM mechanical engineer! 

SLUGS 4 LIFE  (only half joking)


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## Edgy Cheesy Graphite PE

OldSquaw said:


> I've noticed a recurring error in the PPI practice problems where in the solution to the problem they multiply lbm by the acceleration to get lbf. They neglect to divide by g_c. This error is on every problem that I have encountered where you have to convert lbm to lbf. I just solved a problem, and got it "wrong" of course. Only to find out that according to PPI, a 100lbm object weighs 3,220 lbf on earth.
> 
> *The whole concept of lbm is completely stupid*, but they should at least use it correctly.






jean15paul_PE said:


> Spoken like a true MDM mechanical engineer!
> 
> SLUGS 4 LIFE  (only half joking)


Dr. Tom said something so great in his MDM course. (Paraphrasing) _If you see "lb" always it's ALWAYS a force. Even if it says "lbm" treat it like a force. Then you never have to use gc and the units always work out._ This approach is 100% effective in MDM problems and is usually simpler.

I think this less effective in TFS. From what I understand: lbm is genuinely useful in solving TFS problems, and if you use it _and_ gc correctly, then it simplifies many problems. 

_edit: added the "I think" and "from what I understand" because TFS really isn't my thing._


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## Dr. Barber

jean15paul_PE said:


> Dr. Tom said something so great in his MDM course. (Paraphrasing) _If you see "lb" always it's ALWAYS a force. Even if it says "lbm" treat it like a force. Then you never have to use gc and the units always work out._ This approach is 100% effective in MDM problems and is usually simpler.
> 
> This less effective in TFS. lbm is genuinely useful in solving TFS problems, and if you use it _and_ gc correctly, then it definitely simplifies many problems.


I like the approach of Cengel and Boles in their absolutely wonderful undergrad Thermo book. At Slay the PE this is how we handle this issue because our hate for _g_c is unparalleled.


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## OldSquaw

Dr. Barber said:


> I like the approach of Cengel and Boles in their absolutely wonderful undergrad Thermo book. At Slay the PE this is how we handle this issue because our hate for _g_c is unparalleled.
> 
> View attachment 16362


My best advice is to abandon the English system of units altogether. I almost never use English units at work. I just convert the answer to English at the end. That's the easiest way to stay out of trouble. But that doesn't work too well on the PE exam, especially the HVAC exam.


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## Audi Driver P.E.

Dr. Barber said:


> I like the approach of Cengel and Boles in their absolutely wonderful undergrad Thermo book. At Slay the PE this is how we handle this issue because our hate for _g_c is unparalleled.
> 
> View attachment 16362


This methodology is superior in exactly every respect. Thank you for proffering this.


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## OldSquaw

Page 383 and 385, note 3, Saturation temperature DeltaT for other capacities and equivalent length:

The equation in the NCEES reference manual is DeltaT = Table DeltaT*[(Actual Le/Table Le) * (Actual Capacity/Table Capacity)]^1.8

According to the ASHRAE refrigeration handbook, the equation is supposed to be DeltaT = Table DeltaT*(Actual Le/Table Le) * (Actual Capacity/Table Capacity)^1.8


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## Dr. Barber

OldSquaw said:


> Page 383 and 385, note 3, Saturation temperature DeltaT for other capacities and equivalent length:
> 
> The equation in the NCEES reference manual is DeltaT = Table DeltaT*[(Actual Le/Table Le) * (Actual Capacity/Table Capacity)]^1.8
> 
> According to the ASHRAE refrigeration handbook, the equation is supposed to be DeltaT = Table DeltaT*(Actual Le/Table Le) * (Actual Capacity/Table Capacity)^1.8


@OldSquaw Did you report this to NCEES? Just want to check before I do it.

I have a screenshot of *2018* Refrigeration which I get online. NCEES say they copied their table from *2014* Refrigeration, though. Do you have access to that version? I don't. Maybe (doubtful) it changed from 2014 to 2018. I doubt it, but maybe that would explain it.







FYI, I have reported every typo we've discussed in this thread, prior to this post.


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## OldSquaw

Yes I reported this to NCEES.

I only have access to the 2018 ASHRAE Refrigeration Handbook.


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## Dr. Barber

Fun fact: The handbook is missing page 281, which contains the correlation for Nusselt number for turbulent flow in pipes and the natural convection correlations for vertical plates suspended in a stationary fluid.


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## Dr. Barber

Dr. Barber said:


> Fun fact: The handbook is missing page 281, which contains the correlation for Nusselt number for turbulent flow in pipes and the natural convection correlations for vertical plates suspended in a stationary fluid.


Yeah, never mind. I downloaded it again this morning and that file does have this page. I'm not sure how it went missing from the file I had been working with.


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## cjohnson

Is there a comprehensive list somewhere of the known errors in handbook version 1.1, specifically as it pertains to MDM?  I am taking the exam on Monday and would like to review all know errors.


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## ChooChooEngineer_PE

Admittedly vibrations are not my strong suite in MDM but noticed this when I was reviewing some topics with a colleague. Seems they added an extra r^2 to the formula when going to  version 1.1

In MERM this term is absent so I'm pretty sure the formula in 1.1 is wrong but someone who knows better please confirm.


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## Slay the P.E.

ChooChooEngineer_PE said:


> Admittedly vibrations are not my strong suite in MDM but noticed this when I was reviewing some topics with a colleague. Seems they added an extra r^2 to the formula when going to  version 1.1
> 
> In MERM this term is absent so I'm pretty sure the formula in 1.1 is wrong but someone who knows better please confirm.
> 
> View attachment 18727


This was already clarified in this previous post:

http://engineerboards.com/topic/33324-necees-mechanical-pe-reference-manual-released/?do=findComment&amp;comment=7618245


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## ChooChooEngineer_PE

Slay the P.E. said:


> This was already clarified in this previous post:
> 
> http://engineerboards.com/topic/33324-necees-mechanical-pe-reference-manual-released/?do=findComment&amp;comment=7618245


Well I said Vibrations aren't my strong suit, apparently neither is searching


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