NOTE: When I say you must verify your programming with hand solutions, I did not mean a separate calculation for every calculation you make, but you must make at least one or two checks for every TYPE of calculation you make. Thus if you use a computer program to calculate the length of 20 lines, you MUST have checked the lengths of at least one or two of those lines by hand to make sure that your computer equations are correct. When you then calculate the cost of the various pressure lines, you must check that the computer is giving you the correct values for low vs. high pressure lines, and the correct total cost.
The figure below shows the location on a roof where high, medium, and low pressure chloromethane lines are routed from a centralized pump to drop points through the roof, down into the building. Each drop point is fixed at the coordinates given in the table below. The pump itself can be located anywhere on the roof. The lines leading to drop points 1, 2, and 6 are high pressure lines, and cost $13/foot. Medium pressure lines are used at drop points 3 and 4, and cost $8/foot. Drop point 5 requires only a low pressure line costing $2/foot.
High pressure lines are sold in 20 foot lengths with $80 joints. Medium pressure lines come in 40 foot lengths with $50 joints, and low pressure lines come in 50 foot lengths with joints which cost $40 each. Each pipe requires a joint on each end, as well as those needed to connect the individual lengths of pipe to the pump and the drop. Thus a 60 foot long high pressure line will require 4 joints, and a 63 foot long high pressure line will require 5 joints. The pipe vender will sell you any length of pipe you need. So if you need 63.6 feet, he will sell you that exact length. Thus if you need 63.6 feet of high pressure line, you will walk out of the store with 3 stands of pipe 20 feet long, one piece of pipe 3.6 feet long, and 5 joints.
Determine the optimum location for the pump, which will minimize the cost of the lines and joints leading from the pump to the 6 drop points.
- a) (10 points) Solve this problem using EES. Also required is the hand solution that you used to check out the program’s correct operation. You did perform a hand solution to check out the proper operation of the computer program, didn’t you? And I don’t mean that all 50 equations have to be verified, but you must at least check out every TYPE of equation. Thus you don’t have to verify the accuracy of each individual pipe’s length, but you do have to verify at least one of them by hand to make sure that you and the computer agree on how long the pipes are, and how many joints are required, and how much they cost, etc. You also don’t have to check that the final answer is optimal by hand.
- b) (10 points) Include a formal engineering report and letter of transmittal with your solution (similar to those you wrote before they let you out of ENGR 111 and 112.) You can utilize the following resources for additional assistance if needed. If you do not know what should be included in your report, or are otherwise challenged in writing reports, you can also contact the TAMU Writing Center, You paid an $8 fee for their help this semester – just ask them to write it for you. Har har. Please do not ask me for help in report writing or what should be in an engineering report. I have never written one and don’t know how. That’s why I hire Aggie engineers.
Note: You must submit your report/solution electronically. It must be done using Word, and include all necessary figures and calculations in the report. PDF files and photographs are acceptable but MUST be part of your single document. They cannot be attachments or separate files. Hand calculations must be converted to pdf files and included in your document using a scanner. Scanners are available s in the upstairs computer lab. The report must be a single file, including your EES output which you can cut and paste into Word. Simply email your final report to me, using the Subject Line: 322 Roof Pump Engineering Report. Without this subject line your email will probably be automatically discarded as spam. This is the only homework that will be submitted electronically. All other homework problems are to be submitted as hard copies. Note again that this report must be a single file. Multiple files will not be accepted.
Note, from http://writing.umn.edu/tww/WID/engineering/assignments/assign4331formal.htm
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Miscellaneous:
You can assume that the roof is unlimited in size.
You can use EES’s truncate function to work this problem: trunc(length). For example, if you have a 134.2 foot pipe sold in 50 foot lengths you can use trunc(134.2/50.0) + 2 = 4 to get the number of joints required to connect the pipe.
Do not be shocked when you get different answers using a different program such as EES and EXCEL, because the two programs default to different accuracies and different solution methods. The final answers should be reasonably close, but not necessarily identical. Sometimes you can put the answer obtained in one program (EES?) into the second program (Excel?) and the second program thinks the new answer is better than the one he got. That’s because the last time he solved the program he decided he was close enough to the optimum, and quit. You can increase how much accuracy, or to what degree of optimization you wish through the Options features in most programs.
Sometimes you will also get slightly different answers from the same computer program depending on where you initially place the pump. This is because the solution is not continuous in X and Y. For example, starting on the left side of the roof and moving to the right, you may well find that the program is close to the final answer. He looks at it and says “Hummm, the price is getting cheaper by about $5/inch as I move to the right, but if I have to go another inch to the right, I will need to add another $50 joint, so I’m not going there” and he quits. He may not realize that by going another 2″ it would indeed add $100, but then continuing another 4 feet to the right it would have saved him much more. Those are called local optimums. If you had started him from the right edge of the roof with him working to the left, he might not have had to add another joint in the last few inches, and would have reported a somewhat different location, and a slightly better price. But basically, who cares? If I’m off by $200 on a $10,000 job, that’s not worth worrying about. You can, however, see if this is happening to you, by simply finding out where he wants to put the pump, then move it around by a foot or so, and tell him to re-work the problem, starting at this new starting location. If he moves to a new and cheaper location, then you were previously at what is known as a local optimum.
Drop Point |
Y Coordinate (Feet) |
X Coordinate (Feet) |
Line Pressure |
Pipe Cost/Foot $/Foot |
Manufactured Pipe Lengths (Feet) |
Cost of Joints $/Joint |
1 | 0 | 0 | High | $13 | 20 | $80 |
2 | 800 | 0 | High | $13 | 20 | $80 |
3 | 0 | 300 | Medium | $8 | 40 | $50 |
4 | 400 | 350 | Medium | $8 | 40 | $50 |
5 | 800 | 550 | Low | $2 | 50 | $40 |
6 | 150 | 650 | High | $13 | 20 | $80 |
Miscellaneous hints and answers:
From one of the companies that hire you [paraphrased, shortened]:
Lee,
As mentioned in my request to post our latest hiring opportunities, we are growing by leaps and bounds. We are currently looking to hire an Aggie to fill a full time, civil engineering EIT position in our Arlington, Texas office. [Name redacted] was one of several we are considering and we would like your opinion. After working with you for 20 years, you well know the type of employee we are looking for.
Thanks for all your help over the years,
Bill
Bill:
[Name redacted] has over a 3.5 overall so is obviously an excellent student. I often look back to grades in classes I taught them for insight into other than just their technical skills. In some classes I ask them to take one of their homework problems and write it up as a formal report. Screams of anguish invariably arise from some, with comments that they don’t know how to write a report, that this is not a writing class, am I serious, how comprehensive does it have to be, how many pages, can it be double spaced with 20 point font, etc. Then it goes on to what do I want included, how many points is it worth, if they do the technical part but don’t include a report will they get partial credit, and on and on.Anyway, in this case I can’t tell you much about their communications skills since they omitted that part of the assignment. However, I would give them a high recommendation if you are looking for someone with excellent technical skills.
Nice to hear from you again and please keep us in mind when you have future openings,
Lee
Dr. Lowery:
In the assignment, the instructions state to convert our hand calculations to a PDF. However it also states that the report should be one file only. Does word have the ability to merge a PDF file into a report? If so could you explain how to do it and if not should we just attach the PDF as another file?
Answer: Sorry, but you cannot attach a bunch of files to your electronically transmitted report and force your client to go open them all up, one at a time, using all kinds of goofy software like EES that they probably don’t even have. The report must be a single document. This is not to give you a hard time. It is to force you to learn how to do this type of work now rather than have to ask your boss how to do it once you get to your new job.
Here’s how to do it:
In Word 2003, click on “Insert”, “Object”, click on tab “Create New”, highlight “Adobe Acrobat Document”, “OK”, and browse to the pdf file to be included. Or, click on “Insert”, “Object”, click on tab “Create from file”, browse to the pdf file to be included. Or use a beautiful $20 product (your cost from SELL) called Snagit (part of Camtasia). Just display the pdf file and highlight what you want off of the page, or the whole page, and capture it to the clipboard. Then go to Word and paste it from the clipboard. One of the neatest programs you will ever find. L^3
Or, in Word, open the pdf file and click on “Edit” and then “Copy file to clipboard” (Ctrl + C). Then open your Word document, put the curser where you want the figure to be inserted, and click on “Edit, Paste” or (CTRL V). The document will be inserted at the cursor. You can change the size of the inserted item by clicking on it and dragging the corners or right click on it and “Format” it.
Howdy Dr. Lowery,
Can we put the equations into word using the equation editor instead of hand writing them and then scanning them into the computer and converting them? If I was doing this assignment for a company I would not handwrite the equations, I would plug them into word and use a calculator to solve and then put that value into the word document.
Thanks,
Joe
Joe:
That is certainly true. However, what I am trying to do is force you to learn how to make a pdf of something, anything, and include it in a report. I understand that what you propose is easier, but when someone hands you a hand sketch on the job, and you want to transmit it in the report, you will have to make a pdf of it. I want to see you do that somewhere. So no, I want to see literal handwritten calculations inserted into your report, or something similar. If you want to cut and paste the equations from EES, that will be fine, but then I want a hand sketch of a cow or a pig, or something included into the report.
L^3
EES Procedures:
NOTE: You do not have to use or even read the following. It is for students who are interested in some of the more advanced and quite powerful capabilities of EES.
For those of you who notice that if the length of the pipe is exactly a multiple of the “sold” length you don’t get the correct number of joints, the following is an example of an EES “procedure.” It serves the same purpose as a function in programming or in Excel, i.e. it lets you go to a separate set of code with a variable in your hand, and return with that variable altered to your specifications. For example, in the “procedure” shown below, you take the length of pipe that you need to connect two points, say 499 feet, and the fact that the pipe comes in 100 foot lengths, and ask the procedure to give you back the total number of joints required to connect the pipe. You do not have to use this if you don’t want to. The chance that the length will come out an exact multiple of the “as sold” lengths is probably not worth worrying about.
How to use IF … THEN … ELSE statements in EES:
In EES, IF … THEN … ELSE is a procedure, not a function, as it is in Excel.
You must put the procedure in your EES code FIRST, before any equations.
IF … THEN … ELSE procedures MUST be placed at the first of the model and then CALLED, after they have already been defined.
Use a colon to separate the input variables that you want to FEED INTO the procedure, from the output variables (answers) that are OUTPUT BACK FROM the procedure. The following example of a procedure determines how many joints are needed to connect several 100 foot lengths of pipe to make the whole pipe. Note that the “then” must be placed at the end of the line, and the “else” statement must be located as shown – I have no idea why. Note that in this case there are two input variables Lpipe = total length of pipe you need and Lsegment = the length of a segment of pipe as sold in the store, and that these variables are separated by a comma. Next you put a colon to denote ending of the input variables. Then you list Njoints = the output number of joints required to make up the whole pipe. NumberOfJoints is the “name” of the procedure, which can then later be “called”.}
PROCEDURE NumberOfJoints(Lpipe, Lsegment : Njoints)
IF ( (Lpipe / Lsegment) – trunc(Lpipe / Lsegment ) = 0 ) then
Njoints = trunc(Lpipe / Lsegment) + 1
else Njoints = trunc(Lpipe / Lsegment) + 2
END
See how it adds only 1 joint if the length of the pipe is an even multiple of the sold length, but adds 2 joints if it is not?
Typical data input data:
Lpipe1 = 499 {Total length of pipe H1 needed}
Lpipe2 = 500 {Total length of pipe H2 needed}
Lpipe3 = 501 {Total length of pipe H2 needed}
Lsegment = 100 {Length of pipe available for purchase}
Typical way to ask for answers:
CALL NumberOfJoints (Lpipe1,Lsegment : Njoints1) {This sends Lpipe1 and Lsegment TO the procedure and retrieves the answer Njoints1}
CALL NumberOfJoints (Lpipe2,Lsegment : Njoints2) {Same idea}
CALL NumberOfJoints (Lpipe3,Lsegment : Njoints3) {Same idea}
Resulting answers are Njoints = 6 joints for Lpipe1, Njoints = 6 joints for Lpipe2, and Njoints = 7 joints for Lpipe3.
Report writing 101