Small Excel tip today: use the Excel functions VLOOKUP and HLOOKUP to allow you to use tables of data in your calculations. You can configure these commands to “look for the closest match” or to “only find an exact match” by setting the final argument in the functions to TRUE or to FALSE.
When could this help you? Any time you’d like to automate the reading of a table of information. Or any time you can put the action you want to perform into a table form. Or, any time looking in a table of values suits better than trying to use an equation or curve-fit to predict the values.
I have 100 items to enter into this cost estimation. If I have to lookup the material multiplier each time, I'll go make a mistake. Or I'll go crazy. Lets use VLOOKUP instead!
Here are some ideas to use these functions:
read more…
Popularity: 1% [?]
Valentines Day is coming up! So lets go off topic with some dating ideas. Everyone needs these. Even once you’re married, going on a “date” every so often is good relationship maintenance.
But rather than make a list of Valentines Day date ideas, I’ll just drop a general list, so this post helps all days of the year.
Not having a plan when you call to make the date is weak. Unorganized. Lack of effort. It really makes you look lame. Almost as lame as this picture.
read more…
Popularity: 1% [?]
This post will introduce the practice of adding fins to shell-and-tube heat exchanger tubes to increase the surface area, and discuss when to consider it and when to avoid it. This is not a post about air coolers.
Image of finned tubes: Heft Engineers Website
Review: When fluid flows through tubes in a heat exchanger, the total resistance to heat exchange is the sum of: tubeside fluid convection resistance, tube material conduction resistance, shellside fluid convection resistance. Often there is fouling, which will add tubeside and/or shellside fouling conduction resistance. The shell-side fluid resistance is governed by the equation:
read more…
Popularity: 3% [?]
It’s a new year, and maybe time for new jobs! Or at least performance reviews. Knowing your “fair salary,” or the “going market rate” that is paid for your position, can be very helpful. It’s also great to know when you’re a student graduating into your first real job.
Salary Negotiations by Mike "Dakinewavamon" Kline CC by 2.0
It’s a tricky subject, dependant on factors like your profession, location, your specific experiences, how much the interviewer likes your jacket, broad economic and demographic trends, the rigours and demands of the position you are applying to, and frankly–luck.
read more…
Popularity: 5% [?]
Let’s have a quick discussion about engineering ethics: what it is, why it’s important, and a database of ethical case rulings. I think this post might help you if you’re ever in an ethical conflict.
In many places around the world, the title of a professional engineer is closely regulated by professional engineering bodies. Much as you cannot practice medicine without a license, or cannot be a lawyer without passing the bar exam, you cannot do some key engineering activities without a license…or at least close supervision by someone with a license. To get your license, the rules vary from place to place. I know that, annoyingly, all the states of the U.S. and provinces of Canada are different. But normally you need to prove your technical and academic skills through schooling and/or competency exams, build some engineering experience in general, get specific experience in the region you are applying, prove a grasp of legal and ethical concerns, show good character, and reach the age of adulthood.
The ethical rules in each jurisdiction are different, and probably you can get the list for free by contacting your local engineering board. But usually the rules revolve around the same priorities and advise you how you must meet them:
read more…
Popularity: 6% [?]
Interesting little article I found: How to be a Star Engineer.
What the [Bell Laboratories] wanted to know was: what separates the star from the average performer? Is it innate or can star performance be learned? Could a program to improve productivity be designed that would help turn average performers into stars?
The article emphasizes making the most of non-technical skills, like building networks of people who know things, avoiding political problems, volunteering ideas and volunteering for tasks, improving themselves.
I showed it around at work: a few people thought it was very helpful. Others that “this is advice is all good, but pretty obvious.” One woman thought it was all just talking about “a person’s natural charisma, which you either have or you don’t.” (I disagree).
What do you think?
Popularity: 8% [?]
Aspentech’s Hysys is a process simulation tool. You always have to pick a “fluid package” when you use the program: a thermodynamic method it will use to calculate properties, especially vapour-liquid equilibria. I watched an old “webinar” (presentation given through the Internet) on their property packages and took some notes.
You can combine this post with the Hysys manual, the Hysys property package wizard, Aspentech Support’s advice, and books on simulation, and put it all together to choose the best package in each case. If you are in doubt Aspentech Support can always give you personalized advice.
Here are my notes:
-Hydrocarbons: normally use an Equation of State method
-Vapour pressure models are OK at low pressures
-Activity coefficient like NRTL is poor model for hydrocarbons
Equations of State:
-Peng-Robinson is most enhanced in Hysys, highest T & P range, has special treatment for key components, largest binary interaction database: good standard for hydrocarbons
-PRSV: extends PR to moderately non-ideal systems and better represents poor components and mixtures. Adds a new parameter to the equation. Slower calculation speeds than Peng-Robinson
-SRK: modified Redlich Kwong model. Similar to accuracy/use to PR, but has less enhancements in Hysys.
-PR-Twu, SR-Twu for hydrogen solutes? In liquid hydrocarbons
-TST: hydrocarbons with non-ideal components (used in glycol package)
-GCEOS: generalized cubic EOS for user to add their own parameters
read more…
Popularity: 33% [?]
For some fun, check out Engcom.net. It has engineering news, weekly trivia, humour, and also some interesting articles. You can contribute to the site if you get into it.
Popularity: 7% [?]
This is the third in a set of articles introducing the basics of pressure relief valve design from a process designer’s viewpoint. Read Part 1 here and Part 2 here.
Orifice Sizes
Now that you have the scenarios and all the fluid data for them, you can size the orifice. API 520/521 has some equations for this, as well as good advice and factors to put into the equations. There are many programs and spreadsheets out there, so find out what your office uses. You will be better off just reading the design standard you have to use, rather than I trying to explain something that may not apply to you.
One key factor that any calculation procedure will have you do is check for choked flow / critical flow. http://en.wikipedia.org/wiki/Choked_flow Choked flow is when a fluid is going so fast that it reaches sonic velocity: after that, it cannot go any faster no matter what the downstream pressure is. You should know approximately what the inlet and outlet pressure of the relief valve, so you can check if you will reach choked flow. If it is choked, then that changes your results. API discusses this. read more…
Popularity: 64% [?]
This is the second in a set of articles introducing the basics of pressure relief valve design from a process designer’s viewpoint. Read Part 1 here or Part 3 here.
Once you have decided to add a relief valve, know what equipment and pipes it is protecting, and choose the set pressure, you can finally begin to size the valve. The first step, and often the most difficult, is to determine all the different relief scenarios, also called contingencies. A scenario is an event that causes overpressure. You as a designer need to check out all the possible scenarios.
Fire is an extrememly common cause of overprotection you must design against. Photo taken by Kirrus at Flickr licensed CC-by-SA.
Here is a list of a few scenarios to consider:
read more…
Popularity: 43% [?]
Loading ...