Subject: SV: [Fwd: Help for use the low-dimensional dynamic model for slugging] From: "Einar Hauge" Date: Mon, 2 Jul 2007 13:02:59 +0200 To: CC: , , Hi, See comments below: >> -----Opprinnelig melding----- >> Fra: Sigurd Skogestad [mailto:skoge@ntnu.no] >> Sendt: 20. juni 2007 17:31 >> Til: espen.storkaas@no.abb.com; einarha@stud.ntnu.no; >> vidar.alstad@hydro.com >> Emne: [Fwd: Help for use the low-dimensional dynamic model for slugging] >> >> Hei gutter! >> >> Har noen av dere noen kommentar her! >> Vennlkigst send kopi også til meg! >> >> -Sigurd >> >> -------- Original Message -------- >> Subject: Help for use the low-dimensional dynamic model for slugging >> Date: Tue, 19 Jun 2007 20:36:03 -0300 >> From: Rafael Moraes >> To: skoge@chemeng.ntnu.no >> References: >> >> >> >> >> Hi Storkaas, >> >> My name is Rafael and I´m trying to reproduce your model described in >> the paper "A low dimensional dynamic model of severe slugging for >> control design and analysis" but I´m facing some troubles. >> >> When calculating the angle Phi, the expression >> >> acos(1-(H1-h1)*cos(Theta)) >> >> gives a complex number >> >> 0 + 6.3995i >> >> which is, in my opinion, weird. >> >> The values of H1 and h1 used for testing the expression are the same >> used in the code found in your webpage: >> >> H1 = 0.12 m >> h1 = 300 m >> Theta = 0.0274 h1 is the liquid level upstream the dip (see figure 3.1 in Storkaas thesis) and H1 is the critical liquid level. As long as h1 is less than H1, gas will pass through the riser (I think you mix h1 with H2). However, I have seen a problem with an imaginary angle phi. The problem then was that the files didn't take into consideration when h1 was higher than H1 (the case when the liquid prevents the gas for flowing into the riser) This can be prevented by using the following code if(h1data.r)*(acos((data.H1-h1)*cos(data.theta)/dat a.r-1)); A1=data.r2*(pi-phi-cos(pi-phi)*sin(pi-phi)); A=A1; elseif(h1>=data.H1) A1=0; A=A1; end >> >> If it´s right, please, explain the meaning of this complex angle. Or if >> it is, somehow, wrong (maybe the values for the heights are incorrect), >> tell me what must be corrected. >> >> Another problem is the gas mass flow calculation in section 1. The >> expression I found for wg1 is >> >> wg1 = K2*f(h1)*sqrt(rhog1(P1-P2-rhoL*g*alphaL*h2)) Referring to the file slug3DAE (which files are you reffering to?), vg1 is calculated : v_G1=(h10)*(P1-P2-data.rho_ L*data.g*data.H2*alpha_L)/rho_G1); which is the same as in (B.20 in Storkaas thesis) (it is only added that the expression under the square root has to be larger than zero) Note that the angle phi (and the area A) is only used for computing v_G1. Because of the expression (h1> >> which is different from the equation 10 found in the paper cited above. >> Is it right? >> >> I hope I was sufficiently clear to make my questions understandable! >> Please, let me know if I wasn´t clear enough! >> >> Your help will be very important for this work! >> >> Thanks in advance! >> >> Best regards, >> >> Rafael >> >> -- >> ************************************************************************ >> Sigurd Skogestad, Professor and Head of Department Phone: +47-7359-4154 >> Department of Chemical Engineering Home: +47-7393-6855 >> Norwegian Univ. of Science and Technology (NTNU) Fax: +47-7359-4080 >> N-7491 Trondheim, Norway Mobile:+47-9137-1669 >> http://www.nt.ntnu.no/users/skoge email: skoge@.ntnu.no >> ************************************************************************ >> Regards, Einar Hauge