Laserfiche WebLink
no <br /> -21 <br /> �W <br /> �iJ�at <br /> i <br /> b <br /> t� • <br /> �f y <br /> t� <br /> ,...::; FLOW MODELING FOR <br /> VAPOR EXTRACTION SYSTEMS <br /> by Duiron Mauldin <br /> Sacramento, CA <br /> t <br /> INTRODUCTION <br /> Q = flow rate <br /> Ld 1.36=empirical correction[actor <br /> �I 1' The tall of modeling air flow through sail was K = intrinsic permeability <br /> undertaken to provide a more scientific approach b = length of screen in vapor <br /> E in understanding the basic design parameters of extraction well <br /> a vapor extraction system. In most sail venting u = dynamic viscosity of air <br /> ]'- Pv= absolute pressure in vapor <br /> applications,it is important to knew the amount P Po <br /> of vacuum in the vapor extraction well required extraction well(vacuum) <br /> !y to produce the desired flow rate through the soil. P = atmospheric ambient air <br /> l ° This paper will present a theoretical method for pressure <br /> modeling air flow through soil. Field data is R = radius of influence <br /> 1 5 compared to the theoretical method,and present r = radius of vapor extraction <br /> 1l an empirical figure based on the theoretical well <br /> method which was adjusted by the field data. <br /> Additionally,assumptions of the equation values <br /> 4� <br /> 'l'IIGOE2E~'r1CAL METHOD were made to complete a sensitivity analysis of)� <br /> certain parameters: <br /> In 1965, Aravin and Numerov presentedewhich u = 6.3250x10'9, (ft2/lb x min) <br /> from Darcy's L <br /> equation adapted fir Ib/ft <br /> 2116.224 <br /> P = , 2 <br /> modeled air flow through a porous media. { ) <br /> R = 100, ([t) <br /> E nation 1 r = 0.1667, (ft) <br /> Q = 1.36 Kblu ](Pf"/P)-P] I lug (121r) The value for viscosity was taken at 70 degrees <br /> F and I atmosphere. Ambient air pressure was <br /> Q = [low rate assumed to he 1 atmosphere. Due to R being l� <br /> 1.36=empirical correction factor buried in the log function, it was found to be <br /> K = intrinsic permeability non-sensitive to the now rate; therefore,a value <br /> = thickness of porous media of 100 feet was used which corresponds to an <br /> h <br /> �i u = dynamic viscosity of media <br /> average long-term field measurement. A value <br /> Pf = pressure of fluid typically used in soil venting systems �:f 0.1657 <br /> p = absolute pressure feet was used as a radius of the vapor extraction <br /> A R = length of strata well. Substituting the assumed values, dividing <br /> r = radius of induction point both sides of the equation by"b;and simplifying <br /> �. yields: <br /> To adapt the Aravin and Numerov equation so <br /> that it relates let soil venting applications, the E ua <br /> definitions of the equation p:ir::metcrs were <br /> q = 7.7397x107 K ((Pwz/P)P] <br /> redefined to yield: <br /> Equation 2 Equation 3 determines the theoretical flow rate <br /> per foot of screen (rated flow rate) in a vapor <br /> Q = 1.36 Kblu [(Pv21P) P] 1 h:A (Rlr) ;hese^tEansicelpermealsi l. The elty land ion ithee dependent on <br /> amount of <br /> t <br /> is 1 <br />