(9)
Then, the average slope of the equilibrium curve for each
stage must be calculated from
where k (¼ m at total reflux) is some type of average value
mn ¼
n — n—1
ym¼ Fðx; PÞ (17)
whose value or method of calculation is rarely reported。6,16,17 Clearly
xn — xn—1
ln k¯
1 X lnðknÞ
(10)
Finally, the overall mass-transfer coefficient must be cal- culated at each stage from
。KOyam。ðk¯ — 1Þ 6¼ N
n¼1
ðKOyamÞjmn ðkn
— 1Þ
1 1 m
n
(18)
It is also generally true that
KOyamjn ¼ kyamjn þ kxamjn
ln k¯
N lnðknÞ
(11)
With this, all of the information necessary to compute the necessary summation is available。 Obviously, this procedure
ðk¯ — 1Þ 6¼ N
n¼1
ðkn — 1Þ
involves a great deal of calculation。
If the number of stages is large enough and the variation in the local binary relative volatility is not too severe, then a good approximation can be made to the summation in Eq。 8 by replacing it with an integral。*18,19 If we consider a small composition change over a small increment in stage number where the relative volatility is approximately constant, then
Let us now assume that the terms kya and kxa vary only slightly over the length of bed in question and that they can be withdrawn from their respective integrals and replaced by an average value for the length of bed in question。 Then
!
it is easy to show from the Fenske equation that†
Z
hHETPi ¼ N ¼ G
Cy Cx
k a þ k a
(25)
dn 1
(19)
y m x m
dx ¼ xð1 — xÞ ln½aðxÞ]
Equation 19 was derived assuming that the relative volatil- ity can be considered constant during the differentiation but
where
R xt 。
xb
1
xð1—xÞ ln½aðxÞ]
。 ln½mðxÞ]
mðxÞ—1
。 ln½mðxÞ] 。
(26)
then replaced with the compositionally dependent a after the differentiation。 Thus
Cy ¼
R xt dx
xb xð1—xÞ ln½aðxÞ]
¼ mðxÞ— 1
R xt 。 mðxÞ 。 ln½mðxÞ] 。 。
xb xð1—xÞ ln½aðxÞ]
mðxÞ—1 dx
mðxÞ ln½mðxÞ] 填料塔的新传质相关性英文文献和中文翻译(7):http://www.youerw.com/fanyi/lunwen_81699.html