化工原理英文教材-传质与分离部分cha
化工原理英文教材传质分离过程Mass Transfer and Separation Processes
•How to separate a solution of salt and water?
(Problem for producing fresh water from the sea.) (1)Supply heat and boil water off; (2)Supply refrigeration and freeze out pure ice; (3)Pump the water to a higher pressure and force it through a thin solid membrane that will let water through preferentially to salt (reverse osmosis)反渗透.
•Thinking (introspection): Many environmental pollution problems are caused by separation itself?
Why? How to solve this problem?
13
3. Definition of Separation Processes
Product Streams (different in composition, at least 2 streams)
19
Example: Distillation Fractionating
column
Feed
Overhead product
Bottom product
20
•The separation is caused by the addition of a separating agent）. •separating agent: matter or energy •Usually the separating agent will cause the formation of a second phase of matter. • •Separation methods(mass transfer between two immiscible phases):
化工原理英文教材-分离设备部分chapter6
Slurry: solid liquid mixture
Slurry filtration:
Fluid flows through a filter medium by virtue of a pressure difference across the medium.
Most industrial filters are either pressure filters or vacuum filters. They are also either continuous or discontinuous.
Separation of solids from gases; cyclones
Most centrifugal separators for removing particles from gas streams contains no moving parts.
They are typified by the cyclone separator shown in Figure.
1 clarifiers 2 cake filters 3 Cros Filtrate: liquid got from solid liquid mixture by filtration
Septum (filtration media) like paper or cloth. Cake: solid got from solid liquid mixture by filtration.
Clarifying filters
Clarifying filters are also known as ―deep-bed filters‖ because the particles of solid are trapped inside the filter medium.
化工原理英文教材流体输送与计量泵设备Transportation and metering of fluids
If the suction pressure is actually less than the vapor pressure, cavitation will occur in the suction line, and no liquid can be drawn into the pump.
化工原理 Principles of Chemical Industry
Transportation and metering of fluids
The engineer is concerned with practical problems in transporting fluids from one place to another and in measuring their rates of flow.
Such devices increase the mechanical energy of the fluid.
The energy may be used to increase the velocity, the pressure, or the elevation of the fluid.
W
pb
gZb
ub2 2
pa
gZa
ua2 2
(8-1)
The equation(8-1) can be divided by g, gives
H
pb
g
Zb
ub2 2g
pa
g
Za
ua2 2g
(8-1a)
The quantity H is called developed (total) head, in which each term has the dimension of length.
天大化工原理-英文版课件-Chapter 1-11Definitions and Principles
4. Course objectives
• Understand the basic principles of and equipment of the unit operations. • Include designing or selection of devices. operatioroubleshooting of various unit operations.
• The international steam table calorie (calIT), used in heat power engineering, is defined by • 1 calIT=4.1868*×107 ergs = 4.1868* J (1.22)
25
• The standard gravity acceleration
gn 980.665cm / s
2
26
3. FPS Units
• The standard for mass is the avoirdupois pound (lb), • 1 lb = 0.45359237* kg (1.26) • The standard for length is the inch (in.), • 1 ft= 12× 2.54×10–2m= 0.3048* m (1.27) • The standard for time remains the second (s). • The thermodynamic temperature scale is called the Rankine scale,
9
1.1 UNIT OPERATIONS
• • • • 1. Unit operations 2. Classification of unit operations 3. Course description 4. Course objectives
化工原理英文教材-传质与分离部分chapter7
6
3. Thermodynamic relationships
1)Equilibrium ratio ( or equilibrium constant or K
yA KA xA
Where KA=Equilibrium ratio KA AB yA=mole fraction of component A in vapor KB xA= mole fraction of component A in liquid
Chapter 7 Equilibrium rela
1
1. Phase Rule
•F =
C–Φ+2 F = number of degrees of freedom, or variance C= number of components Φ= number of phases 2 —— only temperature and pressure may affect th e.g.: In systems of two components, C=2；Φ=2； therefore, F = 2 - 2 + 2 = 2
The above equations can be rearranged give
(重新整理)
to
16
AB x A yA 1 ( AB 1) x A
Let xA=x；yA=y:
Phase equilibrium equation:
x y 1 ( 1) x
The above equation is used to express the concentration of component A in the vapor as a function of its concentration in the liquid and relative volatility.表示在总压一定时,气液平衡时
化工原理09-传质概论共32页
（质量分率与比质量分率） 3、摩尔分率xA与摩尔浓度cA
4、质量分率aA与摩尔浓度cA
例：8—1（P4）
浓度 换 算
aA
xA aA
MA aB
MA
MB
Y A 1 yA yA ;
yA 1 Y Y A A ;
CACmxA
CA MA aA
实验室测得在 1at总 m及压温2度0C下1， 00g水中含1g氨 时， 液面上氨的平衡6m分m压 H。为 g求气、液相组摩成皆 尔浓度表示时的关相系平。衡
化工原理
（下册）
第八章：传质过 程导论
化工原理下册——传质过程导论
第八章 传 质 过 程 导 论 第一节 概述 一、传质过程（Mass transfer process) 物质从一相（转移到） 另一相的传递过程
气体的吸收(absorption):分离气体混合物 气—液
气
空气
水
吸收
液
NH3 解吸 NH3
律）
牛顿粘性定律 t - m dur
dr
在一定的T、P及CM下，均相
混合物的分子扩散通量为：
JA - DAB
化工原理英文教材传热原理Principles of heat flow in fluids
Principles of heat flow in fluids
Typical heat-exchange equipment
Single-pass shell-and-tube condenser
Expansion joint
It is clear from Fig.11-4 that Δt can vary considerably from point to point along the tube, and, therefore, the flux also varies with tube length.
The local flux dq/dA is related to the local value of Δt by the equation
because, as inspection of Figs11-4a and b will show, it is
not possible with this method of flow to bring the exit temperature of one fluid nearly to the entrance temperature of the other and the heat that can be transferred is less than that possible in countercurrent flow.
The temperatures plotted Fig11-4 are average stream temperatures.
The temperature so defined is called the average or mixing-cup stream temperature.
化工原理课件第七章
7. 传质与分离过程概述
§7.
传质与分离过程概述
§7.1. 概述
一.
1.
传质过程
单相传质过程 在气相或液相中的物质传递
z
推动力：浓度差 ∆Ci 宏观上 — 分子或流体质点由于浓度的不同引起的迁移； 微观上 — 分子的热运动产生的扩散； 热力学基础 — 熵增加过程为自发过程。
z
平衡：体系内浓度均匀
2.
液体中的扩散系数 对于很稀的非电解质溶液,有半经验式：(P14 页 7-43 式) D～溶质的体积、溶剂的粘度及分子量、溶剂的缔合参数、T 有关。由于液体压缩性小,故 忽略 P 的影响。
3.
固体中的扩散系数 z 正常扩散(或体积扩散)：单相扩散 z 努森扩散：分子在孔道中的碰撞扩散+体积扩散 z 结构扩散：分子在孔道中的碰撞扩散 z 表面扩散：分子在孔道表面上吸附扩散 方程形式(略)
p DP ln B 2 RT Z p B 1 p A1 − p A 2 =1 pB 2 − pB 1
因为：P= pA1+pB1= pA2+pB2 则：pA1- pA2= pB2 -pB1 →
那么：NA=
p DP DP p − p A2 DP p A1 − p A 2 ln B 2 A1 = = (pA1-pA2) RT Z p B 1 p B 2 − p B 1 RT Z p B 2 − p B 1 RT Z p Bm p ln B 2 p B1 DC (CA1–CA2) ZCBm
液相
NA=
z
质量浓度： ci=
mi V ni V
kg/m3 kmol/m3
z
摩尔浓度： Ci = 浓度换算：
z
ρ = m/V = ∑ci ( i =A、B、…) ci = mi/V =aim/V = aiρ Ci=ni/V=xin/V=xiC (C=n/V→混合物的总摩尔浓度,kmol/m3) 对于气体混合物： Ci= ni/V=pi/RT ci= mi/V =Mini/V =Mi pi/RT …… 见 P5 页。
化工传质与分离过程第2版
化工传质与分离过程第2版
今天我想谈谈化工传质与分离过程第2版（Imparted and Separation Processes in Chemical Engineering）。
它是一本全面的基础与应用科学的全套教材，涵盖了质量传递，化工流动学，传热和其他分离过程，以及生物及膜技术的信息。
它主要关注的是化工物料的化学性质，物性参数的测量，热物理，传热及物料流动学。
该书由经验丰富和研究精湛的专家撰写，其内容涵盖了流体动力学，传质传热，热力学，生物及膜传质，扩散，乳化，催化，浓缩，氯化，焙烧和干燥等主题。
所有内容均有中英文表述，让学习更加贴近实践，引导读者在理论的前提下，深入到产品开发和工艺设计的实践中去。
化工传质与分离过程第2版具有图表论述，流程图，模型预测及计算题等，从而鼓励学生深度钻研并形成知识链条。
除此之外，该教材还在不同标准下呈现了全面而准确的重要物质运输参数，热力学数据及其他最新技术，进一步提高了学生对物质传质，分离和传热的理解。
总而言之，化工传质与分离过程第2版是传质和分离学的重要参考，涵盖了所有重要内容，是目前最畅销的科技图书之一，值得领域内所有学者广泛阅读。
化工原理02separation
• 通用方法：混合物 + 分离剂 = 相1 + 相2
– 用什么分离剂? （热量 or 纯物流） – 设计什么样的方法和流程? （多级逆流方法，连续 逆流方法） – 用什么设备? （板式塔，填料塔） – 操作参数和设备尺寸? （回流比，板数，填料层高 度） – 热力学和动力学基础 （气液平衡关系，传质速率方 程） – 处理方法：理论级模型
– 重力沉降
Feed oil containing certain amount of water
Oil containing small amount of water How to remove? water
均相混合物的分离
• 均相混合物则是指由不同组分组成的混合物为 均一的液相或气相。 其分离方法为本课程的重 点。 • 通用方法：混合物 + 分离剂 = 相1 + 相2
• 傅立叶定律: q = - (dT/dz)
传质的基本定律
• 某一相内对流传质 • N = k (C-Ci)
• 对流换热: q = (T-Ti)
传质的基本定律
• 两相间传质 • N =K(C-C*)
• q = K (T-T*) • q = K (T1-T2)
与其它课程的关系
• 物理化学 (相平衡关系等的原理) • 化工热力学(相平衡关系等的预测) • 传递原理 (动力学的具体描述和求解)
分离过程引言(?)
INTRODUCTION TO SEPARATION PROCESSES
1 分离过程在化工中的地位 2 常见的分离过程及其分类 3 分离过程中的热力学基础 4 分离过程中的动力学基础
《化工原理》8传质过程导论1.
D RT
dpA dz
将上式中的p、z 对应积分，整理得：
D
NA RTz (pA1 pA2 )
同理，组分B有
D
NB
JB
RTz
pB1 pB2
若为液相，则有
D
N A z cA1 cA2
D
NB z cB1 cB2
例1. 氨气（A)与氮气（B）在一等径管两端相互扩散，管 子各处的温度均为298K，总压均为1.013×105Pa。在端点 1处，氨气的摩尔分数yA1=0.15；在端点2处，yA2=0.06， 点1、2间的距离为1m。已知此时扩散系数DAB=2.3×105m2/s。试求A组分的传质通量。
§8-1-2 相组成的表示方法
1、质量分数和摩尔分数
质量分数
wA
mA m
wB
mB m
wi 1
摩尔分数
xA
nA n
xB
nB n
xi 1
相互换算关系：
wA
xA M A
wi
i Mi
（一般液相用x，气相用y）
wA xAM A
xi M i
i
2、质量比和摩尔比（常见于双组分物系）
扩散：物质在单一相内的传递过程
流体中物质扩散的基本方式：
扩散方式 分子扩散 涡流扩散
作用物 流体分子 流体质点
作用方式 热运动 湍动和旋涡
作用对象 静止、滞流
湍流
分子扩散：
推动力 浓度差 物质传递 简称为扩散
终点： 浓度差为〇
扩散快慢？
College of Power Engineering NNU WANG Yanhua
化工原理英文教材-传热 无相变传热Heat transfer to fluids without phase change
A recognized empirical correlation, for long tubes with sharp-edged entrances, is the Dittus-Boelter equation
Nu hid 0.023Re0.8 Prn k
Where n is 0.4 when the fluid is being heated and 0.3 when it is being cooled.
A better relationship for turbulent flow is known as the Sieder-Tate equation
Nu 0.023 Re0.8 P(r112/-33(2) )0.14 w
Equation(12-32) should not be used for Reynolds numbers below 6000 or for molten metals, which have abnormally low Prandtl number.
Estimation of wall temperature tw
The estimation of tw requires an iterative calculation based on the resistance equation
tm To tw ti 1 1 b do 1 do U o h o k dm hi di
At ordinary velocities the heat generated from fluid friction is negligible in comparison with the heat transferred between the fluids.
化工原理英文教材传热相变传热过程Heat transfer to fluids with phase change
In dropwise condensation
the condensate begins to form at microscopic nucleation sites. Typical sites are tiny pits, scratches, and dust specks.
The drops grow and coalesce with their neighbors to form visible fine drops.
It is the layer of liquid interposed between the vapor and the wall of the tube which provides the resistance to heat flow and therefore which fixes the value of the heattransfer coefficient.
化工原理 Principles of Chemical Industry
Heat transfer to fluids with phase change
Processes of heat transfer accompanied by phase are more complex than simple heat exchange between fluids since it concerns about thermodynamic and hydrodynamic.
friction losses in a condenser are normally small, so that condensation is essentially a constantpressure process.
化工原理英文教材-分离-相间扩散和传质原理Principles of Diffusion and Mass Transfer Between Phases
cAM A cBM B const
••sTtSMJhFucMJhuAemoDAAeAbDMrAmdAsMvdoABcntMBooAcifAodtAcadlldAdtuuaAcdAvhncbctrAmcbdMoAdeidAJBnJMvclebMJvuAcMBgoABtoMBmBdBrl(d代BunldiAcMcu入cemAcBAJMBm)BffBBEellDBdeoodMqDn0MtcwwBdbr0.BABB00(i/A1c0rcaddMo7acdcRfdba.nntPrBlc1eboTnosBJ3twsdi0)MAsssPMRi(ttn1Bdh(hVT17tBueeo.71eJmr.E013etBC0)3ooqfe)l.oda(rn1erif7sn(fft1.uclD1(o7e1s4wA.i71)poB.4dln1grda)dnai4nvcit)bAseAeezs,tetihrmDoede.BnsAB
A
EqAuilibrium
LVab,,xyab VVbb,,yybb VLb ,b ,yxb b LLbb,,xxbb LVb ,,xyb VV,,yy
VL,,yx VLLa,,,xxya
Ay Dfroirvciyneyg
yx
AA
curve
y
yy
y
yy
Driving
force x
VLa,,xya La , xa
J A N A cAu0 cA(uA u0 ) (17.4)
J A =Diffusion flux of component A in the mixture
12
J B NB cBu0 cB (uB u0 ) (17.5) J B =Diffusion flux of component B in the mixture
化工原理-传质基础-1-xw-20190326
对于气相：
CA
PA RT
N Dp p
A RTZA1 A2
对于B 组分，有同样的公式。
(3) 单向扩散
气 相 主 体
N
相界面
JA
N cA
NA
c0
N cB
c0
JBB
液
相
主
体
A可被吸收
B不被吸收
A组分不断被吸收，产生浓度梯度，B组分不被吸收， 也产生反向浓度梯度，故有以上的分子扩散。
总体流动：在压力差的作用下，单相主体向界面移动 称为总体流动。总体流动造成A，B向同一方向移动。
6.2.2 组分运动速度及传质通量
(1) 组分运动速度
a. 绝对速度ui i 组分通过空间某一静止平面的速度。
b. 物系平均速度u
u N c0
u-混合体系的平均速度，m/s;
c0-混合物的表观物质的量浓度，kmol/m3; N- 单位面积上混合物系的摩尔流量,kmol/(m2s)
由于： N Ni, Ni ciui
过程方向、极限、推动力──热力学
分离均相混合物 (用传质过程组织) 所需解决的问题
单相传质 分子扩散 过程速率
对流扩散 相间传质
──动力学
过程计算（设计计算、操作型计算）
6.2 均相混合物内的质量传递
6.2.1 传质的基本方式
单相内的传质机理： （1）分子扩散: 分子随机热运动的宏观结果。 固体、静止的流体和作层流流动的流体内部单独存在 （2）涡流扩散：质点的湍动和旋涡的扰动引起。 湍流流动的流体内（分子扩散的影响可忽略）
D z c0 ln
cB2 cB1
D z
c0
cA1 cA2 cB2 cB1
化工原理英文教材管道和渠道中的不可压缩流动Incompressible flow in pipes and channels
Integration of equation(5-10) with the boundary condition ur=0, r=rw gives
ur
w 2 rw
rw2 r 2
(5-11)
The maximum value of the local velocity is denoted by umax and is located at center of the pipe. The value of umax is found from equation (5-11) by substituting 0 for r, gives
This chapter deals with the steady flow of incompressible fluids through closed pipes and channels
Shear stress and skin friction in pipes
Sheer—stress distribution
The treatment is especially straightforward fluid, for which quantities such as the velocity distribution, the average velocity, and momentum and kinetic energy correction factors are readily calculated.
τ
Flow
p
rw
r
-(p+dp)
τ
Figure
dL
Fluid element in steady flow through pipe.
化工原理英文教材chapter1
2024/2/10
化工原理英文教材chapter1
化工原理英文教材chapter1
v Preparing lessons or preview before class
v →Review after class v Don't take the course just for the grade. v Practice makes a master. If you don't
represented by a letter which symbolizes that quantity, this letter is called dimension. v For SI system, L for length, M for mass, T for temperature, for time. v 3 Unit conversion.
化工原理英文教材chapter1
Background
v What is the text book? Unit Operations of Chemical Engineering.
v It is most popular in Chem. Eng. major in USA univ.
v Authors? Warren L. McCabe, Julian C. Smith and Peter Harriott.
化工原理英文教材 chapter1
2024/2/10
化工原理英文教材chapter1
Introduction
v About the Courses and time scheduling Lecturing (theory)： 14 weeks, 4 classes each week
化工原理英语.doc
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