过程装备与控制工程专业英语翻译_19

2021年2月1日发(作者：节约用电)

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Unit 19 Types of Heat Exchangers

Heat

exchangers

are

equipment

primarily

for

transferring

heat

between

hot

and cold have separate passages for the two streams and

operate most versatile and widely used exchangers are

the shell-and-tube types but various plate and other types are valuable

and

economically

competitive

or

superior

in

some

other

types will be discussed briefly but most of the space following will be

devoted

to

the

shell-and-tube

types

primarily

because

of

their

importance

but

also

because

they

are

most

completely

documented

in

the

they can be designed with a degree of confidence to fit

into a other types are largely proprietary and for the most

part must be process designed by their manufacturers.

Plate-and-Frame

Exchangers

Plate-and-frame

exchangers

are

assemblies of pressed corrugated plates on a frame. Gaskets in grooves

around

the

periphery

contain

the

fluids

and

direct

the

flows

into

and

out

of the spaces between the spacing and the presence of the

corrugations

result

in

high

coefficients

on

both

sides

several

times

those

of

shell- and

?

tube

equipment

and

fouling

factors

are

accessibility

of

the

heat

exchange

surface

for

cleaning

makes

them

particularly suitable for fouling services and where a high degree of

sanitation

is

required

as

in

food

and

pharmaceutical

ing

pressures and temperatures are limited by the natures of the available

gasketing materials with usual maxima of 300 psig and 400 F.

Since

plate-and-frame

exchangers

are

made

by

comparatively

few

concerns most process design information about them is proprietary but

may be made available to serious on factors and heat

transfer

coefficients

vary

with

the

plate

spacing

and

the

kinds

of

g

costs

per

unit

of

heat

transfer

are

said

to

be

lower

than for shell-and-tube equipment.1n stainless steel construction the

plate-and-frame construction cot is 50%-70% that of the shell-and- tube.

Spiral Heat Exchangers

In spiral heat exchangers the hot fluid

enters at the center of the spiral element and flows to the periphery;

flow of the cold liquid is countercurrent entering at the periphery and

leaving at the transfer coefficients are high on both sides

and

there

is

no

correction

to

the

log

mean

temperature

difference

because

of the true countercurrent'action. These factors may lead to surface

requirements 20% or so less than those of shell-and-tube exchangers.

Spiral types generally may be superior with highly viscous fluids at

moderate pressures.

Compact

(Plate- Fin)

Exchangers

Compact

exchangers

are

used

primarily for gas lly they have surfaces of the order of

1200

m2

/m3

corrugation

height

3.8-11.8

mm

corrugation

thickness

0.2-0.6

mm

and

fin

density

230-700

fins/

large

extended

surface

permits

about

...

. .

..

..

four times the heat transfer rate per unit volume that can be achieved

with

shell-and-tube

have

been

designed

for

pressiIres

up

to

80

atm

or

close

spacings

militate

against

fouling

cially compact exchangers are used in cryogenic services

and also for heat recovery at high temperatures in connection with gas

mobile units as in motor vehicles compact exchangers have

the

great

merits

of

compactness

and

light

kind

of

arrangement

of cross and countercurrent flows is feasible

and

three

or

more

different

streams

can

be

accommodated

in

the

same

re

drop

heat

transfer

relations

and

other

aspects

of

design

are

well

documented.

Air

Coolers

In

such

equipment

the

process

fluid

flows

through

finned

tubes and cooling air is blown across them with fans. The economics of

application

of

air

coolers

favors

services

that

allow

25-40

1

temperature

difference between ambient air and process the range above 10

Mbtu/l air coolers can be economically competítíve with watercoolers

when water of adequate quality is available in su Hicient amount

Double-Pipe

Exchangers

This

kind

of

exchanger

consísts

of

a

central

pipe supported withín a larger one by packíng glands. The

straight

length

is

limited

to

a

maximum

of

about

20

ft;otherwise

the

center

pipe

wi1l

sag

and

cause

poor

distribution

in

the

is customary

to operate with the high pressure high temperature high density and

corrosive

fluid

in

the

inner

pipe

and

the

less

demanding

one

in

the

annulus.

The inner surface can be provide with scrapers as in dewaxing of oils or

crystallization

from

al

longitudinal

fins

in

the

annular

space

can

be

used

to

improve

heat

transfer

with

gases

or

viscous

greater

heat

transfer

surfaces

are

needed

several

double-pipes can be stacked in any combination of series or parallel.

Double-pipe

exchangers

have

largely

lost

out

to

shell-and- tube

units

in recent may be worth considering in these situations:

1. When the shell-side coefficient is less than half that of the tube

side;the annular side coeHicient can be made comparable to the tube

side.

2. Temperature crosses that require multishell shell-and-tube units can

be avoided by the inherent true countercurrent flow in double pipes.

3. High pressures can be accommodated more economically in the annulus

than they can in a larger diameter shell.

4. At duties requiring only 100~200 sqft of surface the double-pipe may

be more economical even in comparison with off-the-shell unts.

Shell-and-Tube

Exchangers

This

type

of

exchangers

will

be

discussed

in the following section.

(Selected from: Stanley

Chemical Process Equiment Butterworth Publishers 1988.)

Words and Expressions

e n.

通道，通过

...

. .

..

..

ile a.

多用途的，通用的

etary a.

专利的，私有的

ate v.

成波纹状，起波纹

;corrugation n

n.

沟，槽

cient n.

系数

n.

密封垫片

v.

弄脏，堵塞

;fouling factor

污垢系数

tion n.

卫生

ceutical a.

制药的；药物的

rcurrent n. a.

逆流

n.

< br>翅片

;v.

装翅片

te v.

妨碍，起作用

nic a.

冷冻的，低温的

ry n.

恢复，回收，再生

n.

填料盖，密封套

v.

下垂，下沉

s n.

环状空间

; annular a

环形的

.

v.

脱蜡

llization n.

结晶，结晶体

n.

堆积，烟囱

nt α.在的，固有的

odate v.

调节，适度，容纳

Unit 19

换热器的种类

< /p>

换热器起初是为了在热流和冷流中传热。对两种冷热流体一般有单独的通

< br>道，

一般是连续性操作。

最通用的换热器是壳管式换热器 。

但是不同种类板式和

其他形式是有价值的和经济竞争能力。< /p>

虽然一些其他形式也被讨论，

但是接下来

大部分都在讨论壳管式的。

起初是因为它们的重要性也是应为他们在文献中由较

完整的记载。

因袭它们可以以一种适当过程的准确标准被设计。

其他类型的基本

上市带有专利性的，并且多数必须有他们的制造厂来进行 工艺设计。

板框式换热器

板框式换热器是在一个结构上压紧波纹板的装配体。围在< /p>

边缘的够槽中密封垫片含有液体，

并且控制板间液体的流入与流出 空间。

紧密的

缝隙和波纹的板框换热器，

在两侧的上部达到了管壳式换热器的几倍，

而且板框

式换热器 的污垢系数较小。

换热表面对于清扫的容易性德尔板框式换热器特别适

< br>用于污垢设备，

也适用于卫生要求较高的行业，

比如制药 和食品工业，

受到可能

的垫圈式的密封材料性能的影响，一般最 高压力值为

300

psig

，最高温度为

400

0

F

.

。

< p>

由于较少气液制造板框式换热器，

大多数关于板 框式换热器的工艺设计资料

到有专利性，

但也许提供给负责的工 程师。

摩擦饮食和热传递系数碎着班的空间

和波纹的种类变化。

泵花费的每个热传递单元比壳管式设备低。

用纯钢制造板框

式换热器的费用是管壳式的

50~70%

。

螺旋型换热器

在螺旋形换热设备中，热流进入螺旋单元的中心，并且流

到边缘。

冷流体是逆流的。

在边缘进入并在中心位置流出。

在 两边热传递系数较

高。由于真正的逆流形式没有原来形式的温差，这些因素可能导致表面 要求

20%

或更小的壳管式换热器。螺线形式对于中等压力的高 粘性流体比较适合。

...

. .

..

..

翘片式换热器

翘片式换热器首 先被应用在油气设备中。

典型的翘片式换

热器在单位体积上有< /p>

1200

平方米的表面积，翘片高度

3. 8

～

11.8

mm

< br>，翘片的厚

度是

0. 2

～

0. 6 mm,

片的密度是

230

～

700

片 每米。在单位体积上翘片式换热器

是壳管式换热器的

4

倍。

翘片式换热器的操作压力设计为

80atm

。因为翘片式换热器之间的间距小，

所以不适合易堵塞的设备。

从商业上说，

翘片式换热器适用于低 温设备，

也是用

于与汽轮机相关的高温恢复设备。

对于动力设备来说，

比如在有发动机的交通工

具中，

翘片式换热器有结构紧凑和质量轻的优点。

错流和逆流的任何排 列形式都

是可行的，

并且在同一设备中可以安排三种或三种以上 的流束，

压力下降、

热交

换关系的设计 其他方面被很好的记载。

空气冷却器

这种设备是指由流体流过翘片式的管道，

并且有风扇冷却的

空气通过管道。

考虑空气冷却器的经 济性，

可以允许流体与周围空气和出口的温

差为

25~40

0

F

。荡船热效 率超过每小时

1

千万英热时单位时，空气冷却器与水

< p>
满足要求且供应量充足时，与水冷在经济上不分上下。

套管式换热器

套管式换热器 是由一个尺寸比较大的和中间一个尺寸比

较小的中央管通过塑料密封套连接而成。直线长 度被限制在

20

ft

，否则中心管< /p>

将下沉并且使环面的分配空间较小。一般情况，高温、高压、高密度和腐蚀性的

< p>
液体放在管上，

较小要求的液体被放在外侧管子上。

当在处理石油脱蜡和液体结

晶时，

表面上应该提供刮刀。

在环状的空间上，

轴向翘片可以改善气体和粘性流

< br>体的热交换效率。

假如应用较大的热交换表面。

套管可以 排布堆积起来，

也可以

应用平行方式。

这些套管式换热器已经逐渐被管壳式换热器所取代。

在以下情况

下，是值得考虑的。

（

1

）

当壳侧系数比管侧系数一样小时，这时壳侧系数可以与管侧相比了

（

2

）

我们可以在套管式换热器中采用真正意义上的逆流来代替，

因为温度

较高需要多个套管单元。

（

3

）

在与大直径壳体相比，

我们的环装空间是使用较高压力来满足经济性

能

（

4

）

而与开放式壳体换热器相比，当我们的换热器表面仅仅是

100 ~ 200

sqft

时，我们套管式换热器有较高的经济性

壳管换热器

这种换热器将在以后几章讨论。

Notes

①

本句可译为：

“其他类型基本上是带有专利性的，

并且多数 必须由它们的制造

厂进行工艺设计”

。

②

本句可译为：

“由于较少企业制造板框式换热器，

大多数关于板框式换热器的

工艺设计资料是带有专利性的，但也许可以提供给负责任的工程师”

。

“

N

isavailable to M

”

，

M

可以得到

N.

句中的“

concers

”作企业

,

财团解释。

③

本句可译为：

“错流和逆流的任何排列形式都是可行的，

并且在同一设备中可

以安排三种或多种流束”

。

④

本句可译为：

“当传热速率超过每小时

1

千万英热单位时，

空气冷却器与水质

满足要求且供应量充足时水冷却器在经济性上不相上下”< /p>

。

Exercises

...

. .