8/13/2019 REGIM_TRANZITORIU
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MATERIAL BALANCE ON A TRANSIENT PROCESS IN A PERFECTLY
MIXED STIRRED TANK
The aim of the experimenta !or"
a) the determination of the evolution of the concentration
during a transient process
which takes place into a perfectly mixed stirred tank
b) the comparison between the experimental and theoretical
data
Theoreti#a $a#"%ro&n'
Mass balances are accounting tools that we use to keep track of
how much stuff is in a
given space; they can be viewed as formal statements of the law
of conservation of mass.
They represent the starting point either explicitly or
implicitly for almost any analysis.
They allow us to keep track of material as it is transported
physically or transformed
chemically.
! stirred tank filled with a solution may be considered
perfectly mixed if the
concentration of solid in the output stream e"uals that inside
the tank.
#n the case$
.ct GGG mO ,m I ,m ===
the relationships between the concentration of solid in the tank
and the time during thetransient process is given by the
e"uation$
%ymbols$ %ubscripts$w & the mass fraction of the solid !
& the solid' & the flow rate m & mass( & the volume
of the tank v & volumet & the time # & input
& output*+ initial
v
t / t 0 , A I , A I , A A
GV
t
e )ww( ww
=
=
w A
t0 t t
w A,0
w A,I
w A
t0
t t
w A,0
w A,I
