Hello everyone, i'm an intern in a company that produces HVAC systems, my mission is to study the transmission of the vibrations generated by the moving parts(fans, compressor...) to the bodycar, so this company didn't buy yet a licence for a FEA software like ansys or abaqus, the problem is that my tutor don't have any knowledge on finit elements analysis, so every time i talk to him about FEM it's like I'm talking in chineese. So in order to get me busy he asked me to do some studies about the vibrations of the HVAC WITHOUT A FEA SOFTWARE, and to be honest with you, i don't have any idea from where to start, i tried to simplify the system into mass spring and dumper and slove the deff equations of the system but i don't have any information about the natural frequencies of the HVAC nor what should be simplified,
thanks .
It all depends what aspect of HVAC system your mentor wants you to deal with. From your description it appears it's either vibration isolation problem or something else which you're not aware of. So welcome to the INDUSTRY. Talk to your mentor/manager and ask the specifics of the problem in hand which he needs you to work on (part of an engineer's life)...WELCOME
There are also a lot of quite good free finite element codes you could use to demonstrate the usefulness of simulation (like FEAP, calculix etc.)
thank you Abhimanyu Kumar & Martin Baeker for your advices, so to respond to you Abhimanyu Kumar, i wanted to study the mass(HVAC group) spring and dumping (dumpers installed between the compressor and the HVAC group) by a simple DE (mx''+kx+cx'=f(t) in order to demonstrate to my mentor that the solution we will get is false becasue the group has nearly 24 eigen frequencies in the excitation range, so we can't avoid the resonance,
and for mr Martin Baeker, i tried to use all the free FEA softs like calculiX however they are very limitted in the type of analysis, meshing quality, ..., but i did'nt hear about feap, so i will try to use it.
I presumed you need to analyze the HVAC system as a whole but the interacting components are behaving differently.
I guess the best way is to identify/understand the relationship between the individual part and the HVAC system as a whole. Develop spring damping relationship for each component and combine each component to calculate the natural frequency of the whole system. Be it in parallel or series configuration.
Of course, you can always start with two components interacting using the software mentioned above to verify your results. And with three, four... components when you achieve reliable results.
Hi Tarif,
HVAC (Heating, ventilation and air conditioning) system is the very huge field. First of all be specific, on which topic or area you are concerned. Then try to get the details of of that system. Model it and proceed for FEA.
Did you read the technical resources? ASHRAE has a lot of technical articles for vibration in HVAC machinery, like fans and pumps. You can read this papers because a lot of vibration analysis was made without finite element tools. You can use Matlab tou simulate the system. You can find a lot of models and Matlab code for your analisys. Please, read the alternatives over FEM cause a lot of very interesting studies was made using different approaches
Hello Tarif... First go find the current design and catalog all of the key components. You should be able to determine mass and approximate the center of gravity for all of the major parts. Then... go looking for a senior engineer who has been with the company for a few decades. Hopefully she/he is in a good mood and would not mind sharing their accumulated knowledge.
Accostics/ noise in a vehicle is a difficult determination. Harmonics and structurally borne noise can be difficult to determine source. I know the automotive industry places shock isolators everywhere and I also know they place deadener/mass in the form of a stick on sheet of mastic where oil canning is suspected.
If you've got moving parts, you'll need to learn about balancing the rotors and investigate the design of the bearings. The fan blade design can be reviewed, again balance is important. Knowing all of the load cases is very important... again the Senior Engineer "probably" has a comprehensive design specification/guide laying around in a computer file or maybe loose leaf note book.
You can use SCILAB (developed by INRA) which is a free soft with a module for simulation of dynamic systems (XCOS). A VERY low cost soft for FEA is LISA which is free for up to 1400 nodes and does cost less $100 for nolimit number. Support is very efficient. Both are easy to use.
Now you mention 24 own frequencies, I presume that amplitudes are very different I would first concentrate on major frequencies and see what would be the influences of other frequencies on the system.
Which are the sources for the 24 frequencies ?
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