Principia and Design of Heat Exchanger

Device

热交换器原理与设计

School of Energy and Power Engineering, SDU

Presented： 杜文静E-mail: wjdu@sdu.edu.cn

Telephone: 88399000-2511

mailto:wjdu@sdu.edu.cn

Chapter 2 Shell-and–Tube Heat Exchanger

Shell-and-tube heat exchanger structure calculation ( 结构计算)

Determine main structure parameters and sizes, including:

Determine tube side flow area, including tube size, quantity, tube passes,

and layout in the tube sheet etc.,

Determine shell diameter,

Determine shell side flow area, including baffle type,

Determine the inlet and outlet port size.

Shell-and-tube heat exchanger

structure calculation

Tube side flow area

Based on the continuity equation 连续性方程，质量守恒方程

所需管子数

管程总的流通横截面积

Question: how to determine the flow rate in the tube side?

tube length

Ratio between tube length and the shell diameter is ranging in

4~25, and better 6~10 换热器的长径比

If tube length is large then multiple tube passes are required .

Zt: number of

tube pass

Shell-and-tube heat exchanger

structure calculation

Tube side flow area

Shell side diameter

A rough estimation of shell side diameter:

将计算数值圆整到标准尺寸根据 GB151-1999 中相关标准进行选择。

Shell-and-tube heat exchanger

structure calculation

Shell side flow area

For horizontal baffle 纵向隔板 length

Criterion : velocity in the turning location of horizontal baffle is nearly equal to that of the shell side.

Question: how to determine the flow area in the shell side ？

Shell-and-tube heat exchanger

structure calculation

Shell side flow area

2) For segmental baffle弓形折流板 cut height 缺口高度

Criterion : velocity in the cut location is equal to that of

cross flow between baffles in the shell side.

Question: how to determine the velocity in the segmental

baffles gap area？

Shell-and-tube heat exchanger

structure calculation

Shell side flow area

2) For segmental baffle弓形折流板 cut height缺口高度

Shell-and-tube heat exchanger

structure calculation

Shell side flow area

3) For disc- doughnut 盘环型折流板

Criterion : velocity in different locations is nearly equal to each other.

Shell-and-tube heat exchanger

structure calculation

Port size 进出口连接管

Based on the continuity equation

需将计算得到的管径，圆整到最接近的标准管径。

Shell-and-tube heat exchanger

structure calculation

Shell-and-tube heat exchanger thermal calculation 热力计算

1．overall heat transfer coefficient 总传热系数

o

i

oo

io

m

i

w

wi

ii d

d

d

d

d

d

K

111

i internal fouling resistance 管内壁的污垢热阻

o external fouling resistance 管外壁的污垢热阻

w thickness of tube 管壁厚度

w thermal conductivity 管材的导热系数

d0 tube outside diameter 管子的内径

di tube inside diameter 管子的外径

dm tube mean diameter 管子平均直径 (d0-di)/ln(do/di)

o

o

m

o

w

w

i

oi

i

o

io d

d

d

d

d

d

K

111

Chapter 2 Shell-and–Tube Heat Exchanger

2. . Convective heat transfer coefficient and Colburn heat transfer factor

First review several dimensionless Numbers

hlNu convection heat transfer 表面传热系数；

l: characteristic length 特征长度；

thermal conductivity 导热系数 K

Pr kinematic viscosity of fluid 运动粘度；

thermal diffusivity 热扩散率

ulRe u: velocity 流体的速度；

l: characteristic length 特征长度；

kinematic viscosity of fluid 运动粘度

2. Convective heat transfer coefficient & Colburn heat

transfer factor

Colburn heat transfer factor

Colburn mass transfer factor

1) single-phase convection heat transfer in tubes 管内无相变时

a. heat transfer coefficient inside of tube

a) turbulent flow：Re>10000

low viscous fluid nNu PrRe023.0 8.0 n＝0.4 or n＝0.3

high viscous fluid

14.0

f3/18.0 PrRe027.0

w

Nu

b) transition flow：Re＝2300～10000

Correction factor 8.1

5

Re

1061

T

c）laminar flow Re

b．heat transfer coefficient in the shell side 壳侧对流传热系数

a）without baffles external longitudinal flow internal flow with an equivalent diameter

U

Ad

4 Free-flow area and wetted perimeter

b）with baffles

**disc-and-ring (doughnut) baffle 盘环形折流板:

14.03/1

6.0

06.0 )(Pr08.2w

f

f

me

dGdNu

Gm shell side mass flow rate

**segmental baffle:

For Baffle cut of 25%, Re=2000~1000000

多雷诺法：

14.0

3/16.0 PrRe23.0

w

Nu

科恩法：

14.0

3/155.0 PrRe36.0

w

Nu

Tinker fluid flow model in the shell side 廷克模型

A: leakage from

spacing between the

tubes and tube holes

in baffles

B: crossing flow

C: leakage from

spacing between the

outside most tubes

and the shell

D: leakage from

spacing between the

baffle and the shell

E: bypass flow in the

tube baffle location

D

E

贝尔法（Bell－Delaware method）

rsblcho JJJJJjj

By correcting the ideal heat transfer coefficient hid for various leakages and

bypass flow steams in a segmental baffled shell-and-tube exchanger.

jo average shell-side heat transfer factor

jh ideal heat transfer factor for pure cross-flow in an ideal tube bank

理想管束纯横流时的柯尔本传热因子计算公式

14.03/2 )(Pr wps

oh

cGj

Gs shell side mass flow rate

Jc correction factor for baffle configuration (baffle cut and spacing). it is dependent on the

fraction of the total number of tubes in crossflow between baffle tips. Its value is 1.0 for

an exchanger with no tubes in the windows and increases to 1.15 for all baffle cuts and

decreases to 0.65 for large baffle cuts

折流板切口核跨距校正因子，用以表达因壳程折流板缺口效应时对理想传热因子的修正

Jl correction factor for baffle leakage effects including both tube-to-baffle and

baffle-to-shell leakages a typical value of J1 is in the range 0.7 to 0.8

壳流泄漏效应校正因子，包括壳体对折流板（E 流路）和管子对准拉的泄漏（A 流路）

Jb correction factor for bundle and pass partition bypass stream. Jb usually varies from

0.7 to 0.9

管束 C 流路和 E 流路的旁路校正因子

Js correction for larger baffle spacing at the inlet and outlet sections compared to the

central baffle spacing. the nozzle locations result in larger end baffle spacing and lower

velocities and thus lower heat transfer coefficients, Js usually varies from 0.85 to 1.0

管束进口区和出口区跨距与中间区不同的校正因子

Jr correction factor for any adverse temperature gradient buildup in laminar flows. This

correction applies only for shell-side Reynolds numbers below 100 and fully effective

for Re

2）multi-phase convection heat transfer 相变换热时

a) condensing heat transfer

Condensing heat transfer coefficient of a vertical tube

4/123

943.0

tl

g

L

LL

Condensing heat transfer coefficient of a horizontal tube

b) boiling heat transfer refer to heat transfer textbook

三、pressure drop calculation of shell-and-tube heat exchanger 压降计算，阻力计算

三、pressure drop calculation of shell-and-tube heat exchanger

Pressure drops of the tube side and shell side

1) pressure drop calculation at the tube side 管程阻力计算

Including: channel pressure drop, bend pressure drop, port pressure

drop

沿程阻力，回弯阻力和进、出口连接管阻力

Nrit PPPP

Pt total pressure drop, Pi channel pressure drop

Pr bend pressure drop, PN port pressure drop

a) Channel pressure drop

it

i

i

w

d

LP

2

2

Pa

Moody friction coefficient, from the Moody diagram,摩擦系数

fi: fanning friction factor 摩擦因子

di tube inside diameter, m

L tube length, m

density of fluid inside the tube, kg/m

w velocity of fluid inside the tube, m/s

i viscous correction factor

Re >2100， 14.0/ wi

Re

b) Bend pressure drop 回弯阻力

tt

i Zw

P2

42

Pa, Zt number of tube passes 管程数

c) Port Pressure Drop 进、出口连接管阻力

25.1

2

ni

wP

Pa

2）pressure drop calculation at the shell side 壳程阻力计算

a) without baffles

Equation used in channel pressure drop in straight tube

Equivalent diameter U

Ad

4 free-flow area and wetted perimeter

b) Segmental baffle

Combination of parallel flow and cross flow, The flow is very

complicated; existing gaps, leakage and bypass, therefore it is

difficulty to calculation pressure drop accurately

贝尔法（Bell－Delaware method） details on this method refers to

the textbook

四、design of shell-and-tube heat exchanger 管壳式热交换器的合理设计

1．流体在热交换器内流动空间的选择原则：

1）increasing the smaller heat transfer coefficient

提高传热系数小的一侧的换热系数

2）saving material and reducing the cost

省材料，降低成本

3）easy cleaning and checking

便于清洗检修

4）reducing the heat loss with the environment

减少和环境的热量交换

5）reducing the thermal stress

减少受热不匀造成的热应力

管内：容积流量小的，不清洁易结垢的，压力高的、有腐蚀性的，加热

设备中的高温流体或低温设备中的低温流体

壳体：容量大尤其是气体，刚性结构换热器中对流传热系数较大的流体，

饱和蒸汽等

2. Determination of temperature 流体温度和终温的确定

1）Temp different at hot side 热端温差 ≮ 20 0C

2）Temp different at cold side 冷端温差 ≮ 5 0C

3）Initial temperature of cool fluid should be higher than the solidification

temperature of hot fluid

冷流体的初温应高于热流体的凝固点

4）Temperature of cool fluid should be 5 degrees lower than the dew point of

cooled gas

冷流体的终温要求低于被冷凝气体的露点以下 5 0C

5）For air cooling heat exchanger, the difference of outlet temperature of hot fluid

and inlet temperature of air should be no less than 20 digresses

空冷式热交换器热流体出口和空气进口之间的温差不应低于 20 0C

6）The temperature cross should be avoided for multi tube passes heat exchanger

多管程热交换器要避免温度交叉

3.Select of tube diameter 管径的选择

Smaller diameter tube

Better heat transfer performance and provide more

heat transfer area in the small volume compared

with a large tube diameter;

Larger pressure drop, leaking and fouling problem

because of more tube quantity and more holes in

tube sheet;

More fouling

Larger tube diameter is favorable for gas or liquid with

high viscosity and much fouling in it.

4. Selection of fluid velocity 流体流动速度的选择

Circular water. tube side 1.0 ~ 2.0 m/s, shell side 0.5 ~ 1.5 m/s

Fresh water tube side 0.8~ 1.5m/s shell side 0.5 ~ 1.5 m/s

Gas: tube side 5 ~ 30 m/s shell side 2 ~ 15 ms/

Oil with

high viscosity tube side 0.8~ 1.5m/s shell side 0.3 ~ 0.8 m/s

Oil with

low viscosity tube side 0.8~ 1.8m/s shell side 0.4 ~ 1.0 m/s

When the allowable pressure drop is given, the maximum velocity can be

calculated.

Optimal velocity low capital cost and operating cost.

5.Thermal Compensation in the Shell-and-

Tube Heat Exchanger

管壳式换热器的热补偿问题p77

6.the Vibration and Noise in the Shell-and-

Tube Heat Exchanger

管壳式换热器的振动与噪声p81

五、design procedure of shell-and-tube heat exchanger 管壳式热交换器的设计程序

1．original design data 原始资料

2．thermophyical properties 定性温度，物性

3．Heat transfer and mass flow rate 热流量和质量流量（基于热平衡）

4．select materials 选材料

5．select flow type 选流动方式

6．calculate mean temperature difference 计算平均温差

7．preliminary calculation of heat transfer coefficient K and area F

初选传热系数 K’，初算传热面积

8．heat exchanger structure design 设计热交换器的结构

Including: diameter of tube, velocity, number of tubes and tube passes, tube

layout, number of shell passes, number of baffles, distance between the

baffles etc.

包括：管径、流速、管数、管程、管距、管子排列方式、壳程、折流板

数、折流板间距等

9．thermal calculation 热力计算

10. pressures drop calculation 阻力计算

11. verification of heat transfer coefficient and area 校核传热系数和传热面积

12. verification of wall temperature 核算壁温

13. stress calculation 强度计算和各种热应力

14. drawing, material list etc.绘制图纸、编写材料表等.