化工原理设计原油换热器.docx
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化工原理设计原油换热器
化工原理课程设计
题目:
原油加热器——固定式换热器
指导教师:
李先生院士
职称:
国家特级院士
班级:
高分子材料与工程系
学号:
学生姓名:
一.绪论·····················································································3
二、设计条件及主要物性参数··························································4
1、设计条件···········································································4
2、定性温度的确定··································································4
三.确定设计方案··········································································5
1、选择换热器的类型································································5
2、流程安排···········································································5
四.估算传热面积·····································································5
1、热流量··············································································5
2、平均传热温差·····································································5
3、传热面积···········································································5
五.工程结构尺寸·········································································6
1、管径和管内流速··························································6
2、管程数和传热管数··························································6
3、平均传热温差校正及壳数······················································6
4、传热管的排列和分程方法···············································7
5、折流板···············································7
6、接管···············································7
六、换热器核算···············································8
1、壳程传热系数···············································8
2、管程传热系数···············································8
3、污垢热阻和管壁热阻···············································9
4、总传热系数K···············································10
5、传热面积裕度··············································10
7、管程流动阻力···············································11
8、壳程流动阻力···············································11
七、设计计算结果汇总···············································12
一、绪论
1.加热器简介
.固定管板式
固定管板式换热器的两端管板和壳体制成一体,当两流体的温度差较大时,在外壳的适当位置上焊上一个补偿圈(或膨胀节)。
当壳体和管束热膨胀不同时,补偿圈发生缓慢的弹性变形来补偿因温差应力引起的热膨胀。
特点:
结构简单,造价低廉,壳程清洗和检修困难,壳程必须是洁净不易结垢的物料。
形管式
U形管式换热器每根管子均弯成U形,流体进、出口分别安装在同一端的两侧,封头内用隔板分成两室,每根管子可自由伸缩,来解决热补偿问题。
特点:
结构简单,质量轻,适用于高温和高压的场合。
管程清洗困难,管程流体必须是洁净和不易结垢的物料。
.浮头式
换热器两端的管板,一端不与壳体相连,该端称浮头。
管子受热时,管束连同浮头可以沿轴向自由伸缩,完全消除了温差应力。
特点:
结构复杂、造价高,便于清洗和检修,完全消除温差应力,应用普遍。
本实验采用的是浮头式加热器,包括输油管,输油管上套有密闭的外壳,外壳的一段管道上设有加热体,该加热体用固定卡固定在外壳表面上,所述外壳的外表面上包覆有保温层。
本实用新型具有传热速度快、均温性好的特点,避免了在输送过程中热损失大而导致油品凝固难以输送的问题。
2.设计目的
培养学生综合运用本门课程及有关选修课程基础理论和基础知识完成某项单元操作设备设计的实践操作能力。
设计的设备必学在技术上是可行的,经济上是合理的,操作上是安全的,环境上是友好的。
二、设计条件及主要物性参数
设计条件
由设计任务书可得设计条件如下表:
数
参
类型
体积流量
(标准t/h)
进口温度
(℃)
出口温度
(℃)
设计压力
(Kpa)
柴油
34
175
---
80
原油
33
70
110
80
项目
密度ρ(kg/m3)
比热Cp(kJ/kg?
?
C)
导热系数(W/m2?
℃)
黏度μ(Pa?
s)
柴油
715
原油
815
.定性温度的确定
Wc:
原油流量(kg/h)Wh:
柴油流量(kg/h)Cpc:
原油比热容
Cph:
柴油比热容t1,t2:
原油的出、进口温度
T1、T2:
柴油的进、出口温度
根据《夏清陈常贵化工原理(上)》P225,公式(4-33),
热流量为
Qc=WcCpc(t1-t2)=33000××(110-70)/
=806667W
柴油出口温度:
Qh=Qc=WhCph(T1-T2)
806667=34000××(175-T2)/
T2=℃
可取流体进出口温度的平均值。
管程柴油的定性温度T=(175+)/2=157.5℃
壳程原油的定性温度为t=(70+110)/2=90℃
三、确定设计方案
选择换热器的类型
由设计任务选择固定管板式换热器。
流程安排
柴油温度高,走管程可减少热损失,原油黏度较大,走壳程在较低的Re数时即可达到湍流,有利于提高其传热膜系数。
四、估算传热面积
热流量
平均传热温差
根据《化工原理课程设计》P47,公式(3-9)
===℃
传热面积
根据《夏清陈常贵化工原理(上)》P356表,初步设定K=160W·m-2·℃-1。
根据《化工原理课程设计》P47,公式(3-5)
五.工程结构尺寸
管径和管内流速
选用φ25×2.5mm的传热管(碳钢管)。
管程数和传热管数
根据估算的传热面积,然后查JB1145-73得:
公称直径D(mm)
管
程
数
管
数
管
长
(mm)
管程流通面积()
500
2
168
6000
传热面积A=
外径D=500mm
管程N=2
单程传热管数n=168
管程流通面积S=
该换热器型号为G500Ⅱ
平均传热温差校正及壳程数
根据《化工原理课程设计》P47,公式(3-12)
平均传热温差校正系数
R==
P==
根据《夏清陈常贵化工原理(上)》P231,公式(4-46)
平均传热差校正为△tm=×△tm’=×=(℃)
由于平均传热温差校正系数大于,同时壳程流体流量较大,故取单壳程合适。
传热管的排列和分程方法
采用正三角形排列法,则管间距t=32mm
折流板
采用弓形折流板,
取折流板间距B=400mm。
折流板数NB=-1=-1=14块
折流板圆缺面水平装配。
接管
(1)壳程流体进出口接管
取接管内液体流速u1=1.0m/s,
=
圆整后取管内直径为120mm.
(2)管程流体进出口接管
取接管内液体流速=s,
圆整后取管内直径为130mm
六.换热器核算
总传热系数核算
6.1.1壳程传热系数
根据《夏清陈常贵化工原理(上)》P253,公式94-77a)得
=
其中:
①粘度校正为=
②当量直径,管子为正方形旋转45形排列时,根据《化工原理(上)》P253,公式(4-78)
得
de===
③壳程流通截面积,根据《化工原理(上)》P253,公式(4-80),得
Ao=BD(1-)=××(1-)=
式中B—两挡板间距离,m
D—换热器间的外壳内径,m
④壳程原油的流速及其雷诺数分别为
uo===m/s
Reo===860
⑤普朗特准数(<传热传质过程设备设计>P26,公式1-43)
Pr===
因此,壳程水的传热膜系数为
=
==308W/(m2·℃)
6.1.2管程传热系数
根据《夏清陈常贵化工原理(上)》P248,公式(4-70a)得
i=其中:
①管程流通截面积Si=
②管程柴油的流速及其雷诺数分别为
ui===m/s
Re===11172
③普兰特准数
Pr===
因此,管程空气的传热膜系数i为
i=××6.1.3污垢热阻和管壁热阻
查阅《夏清陈常贵化工原理(上)》P354,附录表20,得
原油侧的热阻Rso=·℃·W-1
柴油侧的热阻Rsi=·℃·W-1
查阅《化工原理(上)》P354,附录表13,得
碳钢的导热系数λ=50W·m-1·℃-1
6.1.4总传热系数K
因此,查《夏清陈常贵化工原理(上)》P227,公式(4-40)
=+Rso+++
=+++
+
解得:
=172W/(m2·℃)
b:
管壁的厚度d0:
管的外径dm:
管的平均直径di:
管的内径
6.1.5传热面积裕度
根据《化工原理课程设计》P47,公式(3-5)
Si=Qi/(△tm)==
该换热器的实际传热面积Sp
Sp==××6×168=
依《化工单元过程及设备课程设计》P76,公