6 replies to this topic

[medelamine]

Hello Everbody, 

 

I would like to ask about the dynamic simulation with hysys, is it an important aspect of simulation ? and what questions can it bring answers to ?

 

My question might be a bit wide, but I'd like to have a practical view on that subject. 

 

Thank you all in advance 

[shan]

A dynamic simulation is for an unsteady condition process such as plant start-up and shut-down when the heat and the material are not balance at that moment.

[medelamine]

So that is the main use of it ? analyzing the start-up and hut-down processes !  

Thanks shan 

[shan]

While, it also was used to analyze the moment of heat exchanger tube raptures and control valve position changes.

[cylai]

Imagine that there is a batch product that needs to be delivered. Dynamic simulation can predict if the controls, hold up time, accumulation and so on is sufficient or you can further optimize your system.

[shantanuk100]

Hello Medelamine,
 

In any Process in any industry, our view of it is usually theoretical and approximated to suit reality.

It is difficult to model exactly as in real life. 

So when we consider these process, a lot of our calculations and understanding are based on the steady state of the system, since that is the state that is easily predictable and calculable. It is the state where all the respective properties being considered, such as speed, temp, heat flow, etc. do not vary with respect to time.

 

Concept

Most of our simulations though, are done for the purpose of emulating a real life scenario and predicting the outcome to a reasonable extent. 

Now, prior to reaching the steady state, any system has to undergo the dynamic state where a lot of parameters vary depending on the time, and there are a lot of fluctuations and disturbances. These situations, are modelled using dynamic simulations, in order to account for the uncertainty in the process. 

For steady states there should be no collection/accumulation of mass or energy over the time period. In dynamic states, this accumulation is possible and is accounted for using time dependent derivative terms. 

 

Scenarios

Since time dependence has now been accounted for, numerous other scenarios can now be modelled, such as startup, shutdown of plants, where a lot of variables vary unpredictably initially.
Scenarios where there is a change in one/more of the parameters in between the process, also, can now be modelled where the transition occuring due to that parameter change is also accounted for. In steady state we are unable to account for all this since the basic assumption itself is that the system has already achieved steady state prior to calculation.

 

Some examples where we might need dynamics include, compressor startup and shutdown, time dependent heat and mass transfer processes, computational fluid dynamics etc.

I am sure you have heard of the Navier stokes equations, a set of time dependent equations that can have dynamic variants as well.

There are innumerable cases where dynamic simulation might be required. It need not be restricted to only startup and shutdown processes. You might, in your term of work, encounter processes where rates of production/ consumption, flow etc. might change with time. In all those situations too, dynamic simulation is equally applicable.

 

Dynamic simulation is also used in electrical processes, mechanical analyses etc. as well so it is already an integral tool in the real world today.

 

 

Regards,

Shantanu

Edited by shantanuk100, 18 November 2015 - 12:59 AM.

[medelamine]

Thank you all dear colleagues,

and thank you shantanu for ur detailed answer !