Currently, i am simulating a Ambient Air Vaporizer (AAV) for LNG Regasification terminal in HYSYS Dynamic. The UA (overall heat transfer coeff) of AAV dependent with time and position. so i wanted to simulate the change of UA in AAV that is function of time and position. i have completed the calculation and now have line equation with dependent variable is UA and the independent variable is time and position, i wanted to use spreasdsheet to use this formula, but i dont know how to import the time data (in integrator) to make my formula works, does anybody know how to do that? i really appreciate your answer thank you
I no longer have access to Hysys but I was always able to connect internal Hysys Spreadsheets to external excel spreadsheest fairly easily. Once the data you need is in the hysys environment you can do whatever calculations you want and use the result to update any value in the simulation.
Iftikhar Ahmad thanks you for your answer, but how does interfacing matlab and hysys spreadsheet works?
Hi Ahmad, it might be helpful to explain what your objective is in the modelling. There could be alternative ways to specify the problem. For example are you trying to look at reduced rate of heat transfer as frost and ice builds on the ambient air heated surface during a period of operation - which reduces heat transfer, OR are you looking at the transient situation where LNG first enters the vaporiser, and the cold 'front' moves through the vapouriser tubes in perhaps a few seconds or a minute, so that the boiling and vapourising zones and their heat transfer coefficients change with time, until an approximate steady state is reached? or both?
David Limb yes, i wanted to know the reduced rate of heat transfer as the frost builds up
OK Ahmad - I would try to formulate the differential equation that defines this. You may need to make some simplifying assumptions to get a solution. Since this is a fairly slow transient you may be able to use a pseudo steady state approach, as a rigorous model is quite complex. For each element of length the heat inflow would be a result of the overall temperature difference ambient to boiling LNG (or supercritical LNG?) and 4 resistances in series: Inside film, tube wall, ice layer (=fn(thickness)) and outside coefficient. Then heat balance for the element has to take account of latent heat release from frost buildup. Good luck!
David Limb thank you for your suggestion, i will try to formulate the equation and try it
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