2. pure water and salt granules are continuously fed into a well-mixed tank at a rate qw(t) [L/s] and w(t) [g/s], respectively, to produce saline solution. let c(t) [g salt/L solution] be the concentration of salt in the saline solution in the well-mixed tank and qout (t) [L/s] be the volumetric flow rate of saline solution out of the tank. in contrast to the lecture notes, here qw + qout- to relate qw to qout, we model the density p [g/L] of the saline solution as a function of the salt content, via p(c) = Pw+ac where pw [g/L] is the density of pure water and a [g/g] is a constant identified from experimental data as in the plot below. Salt solids w gls water saline water density conveyor que qw LIs model 1200- experinental data 1150 1100 saline solution p=p{c)= Pw + ac a = 0.64 g solution/g salt 1050 Jout LIS C g/L 1000 - 0.0 salt concentration, c [g salt/L solution] 0.1 0.2 0.3 (a) (b) Figure 2: (a) our familiar saline solution process except qw 7 qout• the volume V of liquid in the tank is constant because of the overflow line. (b) density of saline solution versus concentration of salt. the line shows the model p(c) = Pw+ac. your goal is to derive a dynamic model for c = and w = w(t). c(t) in terms of the two inputs qw = qw(t) density of solution, p (g solution/L solution]

Introduction to Chemical Engineering Thermodynamics
8th Edition
ISBN:9781259696527
Author:J.M. Smith Termodinamica en ingenieria quimica, Hendrick C Van Ness, Michael Abbott, Mark Swihart
Publisher:J.M. Smith Termodinamica en ingenieria quimica, Hendrick C Van Ness, Michael Abbott, Mark Swihart
Chapter1: Introduction
Section: Chapter Questions
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2. pure water and salt granules are continuously fed into a well-mixed tank at a rate qw(t)
[L/s] and w(t) [g/s], respectively, to produce saline solution. let c(t) [g salt/L solution] be
the concentration of salt in the saline solution in the well-mixed tank and qout (t) [L/s] be
the volumetric flow rate of saline solution out of the tank. in contrast to the lecture notes,
here qw # qout. to relate qw to qout, we model the density p [g/L] of the saline solution as a
function of the salt content, via p(c) = Pw+ac where pw [g/L] is the density of pure water
and a [g/g] is a constant identified from experimental data as in the plot below.
Salt solids
w gls
water
saline water density
conveyor
qw LIs
model
1200-
experimental data
1150
1100 -
saline solution
p=p(c) = pw+ ac-
a = 0.64 g solution/g salt
1050
Jout LIS
C g/L
1000
0.0
0.1
0.2
0.3
salt concentration, c [g salt/L solution]
(a)
(b)
Figure 2: (a) our familiar saline solution process except qw # qout. the volume V of liquid in the
tank is constant because of the overflow line. (b) density of saline solution versus concentration
of salt. the line shows the model p(c) = Pw + ac.
qw(t)
your goal is to derive a dynamic model for c = c(t) in terms of the two inputs qw =
and w = w(t).
density of solution, p
Ig solution/L solution]
Transcribed Image Text:2. pure water and salt granules are continuously fed into a well-mixed tank at a rate qw(t) [L/s] and w(t) [g/s], respectively, to produce saline solution. let c(t) [g salt/L solution] be the concentration of salt in the saline solution in the well-mixed tank and qout (t) [L/s] be the volumetric flow rate of saline solution out of the tank. in contrast to the lecture notes, here qw # qout. to relate qw to qout, we model the density p [g/L] of the saline solution as a function of the salt content, via p(c) = Pw+ac where pw [g/L] is the density of pure water and a [g/g] is a constant identified from experimental data as in the plot below. Salt solids w gls water saline water density conveyor qw LIs model 1200- experimental data 1150 1100 - saline solution p=p(c) = pw+ ac- a = 0.64 g solution/g salt 1050 Jout LIS C g/L 1000 0.0 0.1 0.2 0.3 salt concentration, c [g salt/L solution] (a) (b) Figure 2: (a) our familiar saline solution process except qw # qout. the volume V of liquid in the tank is constant because of the overflow line. (b) density of saline solution versus concentration of salt. the line shows the model p(c) = Pw + ac. qw(t) your goal is to derive a dynamic model for c = c(t) in terms of the two inputs qw = and w = w(t). density of solution, p Ig solution/L solution]
(b) write an overall (salt + water) mass balance. it will be a differential equation.
(c) use the overall mass balance to eliminate qout from the salt balance, so that the input
qw appears in the salt balance. also, use p(c) = Pw + ac to eliminate p from your
dynamic model. write the final dynamic model as
dc
(..
:).
dt
with .. representing algebraic (not differential) expressions.
Transcribed Image Text:(b) write an overall (salt + water) mass balance. it will be a differential equation. (c) use the overall mass balance to eliminate qout from the salt balance, so that the input qw appears in the salt balance. also, use p(c) = Pw + ac to eliminate p from your dynamic model. write the final dynamic model as dc (.. :). dt with .. representing algebraic (not differential) expressions.
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