学习了流体流动、间壁式换热器、二元精馏和精馏塔
意义：对理解实际生产过程的原理很有利
Fluid flow, wall heat exchanger, binary distillation and distillation tower were studied
机械能守恒——伯努利方程
条件：流体不可压缩，即密度为常数
流体的运动参数不随时间发生改变，只与空间有关，
The fluid is incompressible, that is, the density is constant
The motion parameters of the fluid do not change with time, they are only related to space.
在实际问题比如流体管道输送问题中，涉及到机械做功和流体阻力损失（黏性引起）：动能、位能、静压能、机械对流体做功、流体流动损失
In practical problems, such as pipeline transportation, mechanical work and fluid resistance loss (caused by viscosity): kinetic energy, potential energy, static pressure energy, mechanical work on fluid, fluid flow loss
应用：不能离运动中的火车太近Cannot be too close to a moving train
流体流动的分类（根据流体内部的流动结构）
层流流动：流体质点运动规则、稳定。流体层之间基本没有影响，速度分布为抛物线型。在管中心注入有色示踪剂，示踪剂将在管中形成一条有色直线，直到分子扩散作用使其逐渐消失。
Laminar flow: fluid particles move regularly and stably. There is no influence between the fluid layers, and the velocity distribution is parabolic. When a colored tracer is injected into the tube center, the tracer will form a colored straight line in the tube until the molecular diffusion makes it disappear gradually.
湍流流动：流体质点运动紊乱、不稳定。流体质点的横向运动导致流体层之间的混合加强，管壁附近速度梯度大，意味着湍流时管壁与流体的摩擦力增加。示踪剂在管中很快弥散，不能形成一 条直线
Turbulent flow: fluid particle movement is disordered and unstable. The transverse motion of the fluid particle results in the enhancement of the mixing between the fluid layers and the large velocity gradient near the tube wall, which means that the friction between the tube wall and the fluid increases when the turbulence occurs. The tracer disperses quickly in the tube and cannot form a straight line
间壁式换热器
作用：用于在具有不同温度的流体和流体之间、流体和固体之间传递热量的装置。使热量从温度较高的流体传给温度较低的流体
A device for transferring heat between a fluid and a fluid with different temperatures and between a fluid and a solid. To transfer heat from a hotter fluid to a hotter fluid
分类：Shell and tube heat exchanger
在圆筒形壳体中放置管束，管子的端部固 定在管板上，管板与壳体焊接，为了改善壳程传热性能和支承管子，在壳程安装折流板，用拉杆 和定距管将其固定组装
The tube bundle is placed in the cylindrical shell, the end of the tube is fixed on the tube plate, and the tube plate is welded with the shell. In order to improve the heat transfer performance of the shell side and support the tube, the baffle plate is installed on the shell side, and fixed and assembled with the pull rod and the distance tube
优点：结构坚固，可靠性高，适应性广，易于制造，处理能力大，生产成本低，清洗方
便，能承受较高的压力和温度 缺点：金属消耗量大，结构紧凑性一般
Advantages: solid structure, high reliability, wide adaptability, easy to manufacture, large processing capacity, low production cost, easy to clean, can withstand high pressure and temperature
disadvantages: large metal consumption, general compactness
套管式换热器
结构：1——U形管；2——内管；3——外管 原理：一种流体走内管，一种流体走内外管之间的环形间隙，内管的壁面为传热面
The utility model relates to a fluid flowing through an inner tube, a fluid flowing through an annular gap between the inner and outer tubes, and the wall surface of the inner tube is a heat transfer surface
特点 优点：结构简单，传热面积增减方便 缺点：检修、清洗、拆卸麻烦，连接处容易泄漏
Advantages: simple structure, convenient heat transfer area increase and decrease disadvantages: maintenance, cleaning, disassembly trouble, easy to leak
at the connection
板面式换热器
结构：通过板面进行传热Heat transfer by plate surface
优点：传热性能比管式换热器好，而且由于结构 特点，使流体在低速下能达到湍流状态，从而强 化传热
The heat transfer performance is better than that of tube heat exchanger, and because of the structural characteristics, the fluid can reach turbulent state at low speed, thus enhancing the heat transfer
缺点：Withstanding voltage
结构
管程：换热管内部分及与其连通部分Tube side: inner part and connecting part of heat exchange tube
换热管Common size (outer diameter × wall thickness)常用尺寸（外径×壁厚）：φ19mm×2mm、 φ25mm×2.5mm的无缝钢管，管长有1.5m、 3m、6m等
排列方式: 正三角形：利用率高，用得最普遍，不易清洗。正方形：容易清洗，机械清洗。Triangle: high utilization, most commonly used, not easy to clean. Square: easy to clean, mechanical cleaning
管板：tube sheet
作用 排布换热管 将管程流体和壳程流体分开 承受管程、流体的压力和温度
Arrange heat exchange tubes to separate tube side fluid and shell side fluid, and bear the pressure and temperature of tube side and fluid
管箱 Tube box
作用：把输送来的流体均匀分布给换热管，然后再收集换热管里的流体送出换热器
Evenly distribute the delivered fluid to the heat exchange tube, and then collect the fluid in the heat exchange tube and send it out of the heat exchanger
壳程：换热管外部分及与其连通部分. Shell side: outer part of heat exchange tube and its connecting part
壳体 shell
A connecting pipe is welded on the shell for the shell side fluid to enter and exit. Bearing pressure
折流板Baffle plate 增加湍流程度，增大传热系数，同时还能支承管束Increase turbulence, increase heat transfer coefficient, and support tube bundle at the same time
换热器的传热. 传热过程：热量由热流体以对流方式传递到间壁→热
量以导热方式穿过间壁→间壁通过对流方式将热量传给冷流体
Heat transfer process: heat is transferred to the wall by convection from hot fluid → heat passes through the wall by conduction → the wall transmits heat to cold fluid by convection
热传导 ：由于物体各部分之间不发生运动，仅依靠原子、分子等微观粒子的热运动而产生的热能传递
Because there is no movement between the parts of the object, only the heat transfer generated by the thermal movement of micro particles such as atoms and molecules
定律（公式
傅里叶导热定律：导热速率的大小与该处的温度梯度、导热面积成正比，负号表示其方向与温度梯度的方向相反。Q热传导速率（单位时间传导的热量）W，λ为热导率（传热系数，表示物体导热能力的大小）W/（m·℃），S导热面积m²，温度梯度。Fourier law of heat conduction: the magnitude of heat conduction rate is directly proportional to the temperature gradient and heat conduction area. A minus sign indicates that the direction is opposite to the direction of temperature gradient. Q heat conduction rate (heat conduction per unit time) W, λ is the heat conductivity (heat transfer coefficient, indicating the size of the object's heat conduction ability) w / (m
·℃),
s
heat
conduction
area
m2,
and
temperature
gradient.
热对流 是指存在温差时，流体宏观流动引起的冷、热流
体相互掺混所导致的热量迁移It refers to the cold and heat flow caused by the macro flow of fluid in the presence of temperature difference
The heat transfer caused by the mixing of solids
但在实际问题中以不同温度的流体和固体表面发生的热量传递过程为主要研究，称为对流传热 However, in practical problems, the main research is the heat transfer process on the surface of fluid and solid at different temperatures, which is called convective heat transfer
牛顿冷却定律：单位面积的换热量与壁面和流体之间的温度差成正比
Φ=h·A·Δt
Φ is the total heat transfer rate, w
H is the surface heat transfer coefficient
A is the total heat transfer area
总传热速率：导热速率+对流传热速率 Total heat transfer rate:
heat transfer rate + convection heat transfer rate
总传热速率方程：Q=KSΔtm Total heat transfer rate equation
Q总传热速率，J/S或W Total heat transfer rate
K总传热系数Total heat transfer coefficient单位W/(㎡·℃)，可通过计算、查表、实验三种方法得到
S换热器传热面积Heat transfer area of heat exchanger
Δtm总平均温度差：Total average temperature difference采用逆流，Δt1热流体进口冷流体出口，Δt2热流体出口-冷流体进口。逆流的平均温差总大于并流。所以多采用逆流操作
精馏塔 Distillation column
板式塔 The tower is equipped with a tray, and the air flow generates bubbles in the liquid layer of the tray, and the mass transfer is carried out by the bubble surface
泡罩塔：每层塔板开有若干圆孔，上边覆盖泡罩。工作时，液体横流过塔板，泡罩下边缘齿缝浸没在液层中，上升气体通过齿缝进入液层，分散成若干小气泡Bubble cap tower: each layer of tower plate is provided with a number of round holes, and the upper edge is covered with bubble cap. During operation, the liquid flows across the tray, and the lower edge of the bubble cap is submerged in the liquid layer. The rising gas enters the liquid layer through the gap and disperses into several small bubbles
Advantages: large operation flexibility, stable operation of the tower in case of large load fluctuation, not easy to block
Disadvantages: complex structure, high cost and trouble in maintenance
筛板塔：上升气流通过板上的筛孔分散成细小的股流，在板上的液层
中鼓泡而出，气液间进行接触。
Sieve plate tower: the updraft is dispersed into small streams through the sieve holes on the plate, bubbling out in the liquid layer on the plate, and gas-liquid contacts.
优点：结构简单，成本低，维修方便
缺点：气量太小时，容易漏液
Advantages: simple structure, low cost and convenient maintenance
Disadvantages: easy to leak
流体流动阻力系数的测定实验
Measurement experiment of resistance coefficient of fluid flow
为什么测？因为在工业中阻力系数一般都是选取的，不准确，最准确的是自己测定
Why? Because in the industry, the resistance coefficient is generally selected, inaccurate, and the most accurate is self-determination
流动阻力分为直管阻力和局部阻力。∑hf=hf+hf‘。
直管阻力由于流体内摩擦引起 测定压差、流速。Δp压力降Pa，ρ流体密度kg/ m³，
λ直管摩擦阻力系数，l管长m，d管内径m， u流速m/s
局部阻力是由于流体流经阀门、 管件等管截面突然扩大或缩小， 或者流动方向发生改变的地方增大流体内摩擦从而引起的阻力
The local resistance is caused by the sudden expansion or reduction of the cross section of the pipe such as the valve and pipe fitting, or the increase of the internal friction of the fluid at the place where the flow direction changes
测定压差、流速。Δp 压力降Pa，ρ流体密度kg/m³，ζ局部阻力系数，u流速m/s
实验装置：水箱、泵、出口阀、闸阀、截止阀、压差计、文丘里流量计
Inspection device: water tank, pump, outlet valve, gate valve, stop valve,
differential pressure gauge, venturi flowmeter
步骤
测定直管摩擦阻力系数：26阀全开，3457阀全关，启动离心泵，调节出口阀1，管路流量从大到小取6次，每次取值等到 直管的压差读数稳定后，记录下压差和流量，根据公式计算
Measure the friction resistance coefficient of straight pipe: 26 valve is fully open, 3457 valve is fully closed, start centrifugal pump, regulate outlet valve 1, take 6 times of pipeline flow from large to small, take each value until the reading of differential pressure of straight pipe is stable, record the differential pressure and flow, and calculate according to the formula
测定局部阻力系数：26阀关闭，3457阀全开，调节出口阀1，管路流量从大到小取6次，每次取值等到控制柜上的仪表示数稳定之后，记录下管路流量、闸阀的压差、截止阀的压差，根据公式计算
Measure the local resistance coefficient: close valve 26, fully open valve 3457, adjust outlet valve 1, take 6 times of pipeline flow from large to small, take each value until the instrument indication on the control cabinet is stable, record the pipeline flow, differential pressure of gate valve and differential pressure of stop valve, and calculate according to the formula
实验结果：λ直管阻力系数0.025左右，闸阀的局部阻力系数1.4左右，截止阀的局
部阻力系数12. 8左右
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