Psychometic Problems while being prohibited from marking materials

[spacebanjo]

Hello,

Currently studying for Mech thermal/fluids exam in April. I am getting whooped by the MERM problems (although I understand they are much more difficult). In particular some problems require plotting Sensible heat /total Heat slopes on a psychometric chart (eg. MERM13 page 43-6 and 43-8 Recirculating Air Bypass).

I am unable to get these problems correct because I cannot plot the line slopes accurately as the scales are crude.  Furthermore, as I understand, during the exam we are prohibited from marking our reference materials which means we will not be allowed to plot lines on a psych chart --if there are multiple condition lines this would be a nightmare trying to finangle two rulers and keep them in place.

Anyone have tips for dealing with psychometric chart plotting? Am I missing some tools (compass, right angle etc) that might assist in this process?

Thanks,

 

[Ramnares P.E.]

It was my understanding that if solving a problem absolutely requires plotting on a psych chart, one would be provided in the exam booklet. 

 

[landolakes]

Google Coolerado Psychrometric chart. Its a great chart that is colored and clearer than one in NCEES and MERM.

print several copies for marking on and use one unmarked one for the exam. I just slipped mine behind the clear plastic on back of my notes binder.

 

[justin-hawaii]

Hi spacebanjo,

I don't think you should be too worried about the SHR type questions, because I doubt that a testmaker would make possible exam solutions very close to one another, such that a slight difference in a SHR would cause a different exam solution.  Also you can break up the SHR into vertical (latent change) and a horizontal (sensible change) lines.  For example, if your SHR was 0.8, then you could arbitrarily choose a sensible load of 8,000 BTUH, total load of 10,000 BTUH and a latent load of 2,000 BTUH.  Then you could use the enthalpy and the dry bulb temperature to find a new point from your original point, with a SHR of 0.8.  I am not sure how much more detail I need to provide, but let me know if that makes sense.  

Also, just fyi, one of my old coworkers was removed from the test for marking up a psychrometric chart.

 

[spacebanjo]

Justin thanks for the helpful comment. I think I understand -- that's a much better method than trying to eyeball parallel lines.

 

[starquest]

I used the attached chart, although there probably are much better versions out there.   I highlighted the major lines each in different colors to make it easier to read.   I took with me to the exam a clear plastic triangle and a 6" stainless steel rule.   With a combination of these tools, I didn't have to draw lines or make pencil marks on the sheet. 

View attachment Psychrometric Chart.PDF

 

[Audi Driver P.E.]

I used the attached chart, although there probably are much better versions out there.   I highlighted the major lines each in different colors to make it easier to read.   I took with me to the exam a clear plastic triangle and a 6" stainless steel rule.   With a combination of these tools, I didn't have to draw lines or make pencil marks on the sheet. 

View attachment 9213

I made several copies of that one and used them for practice.

 

[Audi Driver P.E.]

Google Coolerado Psychrometric chart. Its a great chart that is colored and clearer than one in NCEES and MERM.

print several copies for marking on and use one unmarked one for the exam. I just slipped mine behind the clear plastic on back of my notes binder.

I had some printouts of this one too, that I used. http://www.coolerado.com/pdfs/Psychrmtrcs/0000Psych11x17US_SI.pdf

 

[MikeGlass1969]

That ASHRAE chart appears to be identical to the chart that was included in the back of my exam booklet.  This is the chart I used to draw/write on during the exam.  

 

[spacebanjo]

I just took the official 2017 practice exam - I can confirm they supply charts for air, refrigerant etc if it is required.