Types of Evaporator in Air Conditioning

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ContentsSummary.................................................................................................................... 3

Introduction................................................................................................................ 4

What is evaporator.................................................................................................. 4

History.....................................................................................................................5

How does evaporator work......................................................................................5

Types of evaporator.................................................................................................... 6

Centrifua! evaporator............................................................................................ 6

"anfactures#........................................................................................................$

%otary evaporator...................................................................................................$

&around..............................................................................................................'

(esin.................................................................................................................. '

)!ooded evaporators................................................................................................*

(irect +,pansion Coi! +vaporator..........................................................................-

Types of evaporator used today...............................................................................-/

Circu!ation evaporators......................................................................................... -/

0atura! Circu!ation evaporators.............................................................................-3

)orced Circu!ation +vaporator...............................................................................-3

Batch pan Evaporators..............................................................................................-4

%isin 1!m +vaporator...........................................................................................-5

)a!!in )i!m +vaporator.......................................................................................... -6

%isin2)a!!in +vaporator....................................................................................... -$

"u!tip!eeect evaporators................................................................................... -'

itated thin 1!m evaporators...............................................................................-'

Conc!usion#............................................................................................................... -*

-



)iure -# Schematic diaram of evaporator................................................................4

)iure /# an e,amp!e of evaporation process.............................................................5

)iure 3# Typica! refrieration Cyc!e............................................................................6

)iure 4# Cutaway imae of HT4 Centrifua! +vaporator.........................................$

)iure 5# &7chi %otavapor %/ with 898 assem:!y ;vertica! water condenser<.... .'

)iure 6# =ooded evaporator.................................................................................... -)iure $# (irect e,pansion coi! evaporator...............................................................--

)iure '# direct e,pansion evaporator......................................................................-/

)iure *# 9ertica! tu:e forcedcircu!ation evaporator................................................-3

)iure -# 0atura! Circu!ation evaporators...............................................................-3

)iure --# )orced Circu!ation +vaporator..................................................................-4

)iure -/# &atch pan +vaporators............................................................................-5

)iure -3# %isin 1!m evaporator..............................................................................-6

)iure -4# )a!!in)i!m +vaporators...........................................................................-$

)iure -5#%isin2)a!!in +vaporator..........................................................................-$

)iure -6# (ou:!eeect fa!!in 1!m evaporator.......................................................-'

)iure -$# >ey e!ement of vertica!thin evaporator..................................................-*

/



Summarys one of the most enery intensive processes used in the dairy? food and chemica!

industries? it is essentia! that evaporation :e approached from the viewpoint of

economica! enery uti!i@ation as we!! as process eectiveness. This can :e done

on!y

if the eAuipment manufacturer is a:!e to oer a fu!! se!ection of evaporation

techno!oy

and systems deve!oped to accommodate various product characteristics? the

percent

of concentration reAuired? and reiona! enery costs.

This hand:ook descri:es the many types of evaporators and operatin options

avai!a:!e throuh the e,perience and manufacturin capa:i!ities of B9.

3



Introduction

What is evaporator

An evaporator is a device used to turn the liquid form of a chemical into its gaseous form. The liquidis evaporated, or vaporized, into a gas.

Figure 1: Schematic diagram of evaporator

Evaporation is a special case of heat transfer to a boiling liquid. This particular heattransfer application is so common and important that it is treated as a separate unit

operation.

The intent is to concentrate a non-volatile solute from a solvent, usually water. This is

done by boiling off the solvent. Concentration by evaporation is normally stopped

before the solute begins to precipitate; if not, the operation is better considered

as crystallization.

Evaporation is usually treated as the separation of a liquid mixture into a liquid product concentrate or thick liquor ! and a vapor byproduct, although in special cases

such as water treating and desalination, the vapor is the product instead of the thic"

liquor.

The evaporator is kind of heat transfer apparatuses where the heat transfer is done :y

forced convection or natura! convection. nd its an important component of

4



refrieration system and air conditionin system.

+vaporation process is reDection of water ;or other !iAuids< :y concentratin the

so!ution. The reAuired time for this process can :y shortened :y increasin the surface

area? the so!ution is e,posed to it? or :y e,posin the so!ution to heatin to a hiher

temperature.

Figure 2: an example of evaporation process

History

The invention of the mu!tip!e eect evaporator is enera!!y credited

to 0or:ert %i!!ieu,. %i!!ieu, deve!oped a mu!tip!e pan evaporation

system for use in suar re1nin. %i!!ieu, was :orn in Eouisiana and

trained in )rance. "ost of his workin career was spent in the F.S.?

a!thouh he !ater returned to +urope where he is :uried in the

famous Bere Eachaise cemetery in Baris. %i!!ieu,Gs achievements

were !itt!e acknow!eded durin his !ifetime? :ecause accordin to

the !aws of the time he was 8a free person of co!or.8 He was a!so the

1rst cousin? once removed? of the painter +dar (eas.

How does evaporator wor )or a :asic refrierant cyc!e shown in 1ure -? which is used in many forms in a!!

common air conditionin? refrieration? heat pump app!ications. It uses a proper

refrierant that has the capa:i!ity to chane phase from !iAuid to as and from as to

5



!iAuid.

)or a home air conditionin e,amp!e? the refrierant enters the compressor is a !ow

pressure coo! as? where it compressed to a hih pressure hot as? then passes to the

condenser. In the condenser coi!? the refrierant phase chanes from hot as at hih

pressure to hot !iAuid at hih pressure. This condensation causes a !are heat reDectionto surroundin.

The !iAuid refrierant is then passed throuh a 1,ed no@@!e or e,pansion device to e,it

as a co!d !iAuid at a !ow pressure. )ina!!y refrierant enters the evaporator at a:out

$ to ' !iAuid and / to 3 vapor.

In the evaporator a very !are amount of heat is a:sor:ed from surroundin ;the indoor

air< causin the !iAuid refrierant to :oi! and turn into a as phase? which is passed to

compressor to repeat the cyc!e aain unti!e the indoor air :e comforta:!e and

sucient!y coo!.

The evaporator works at a constant temperature as !on as the pressure remainsconstant.

Figure !: "ypical refrigeration Cycle

"ypes of evaporator

The evaporators may :e c!assi1ed into a forced convection type or natura! convection

type? dependin on whether the su:stance to :e coo!ed !ows natura!!y :y dierence in

density throuh the heat transfer surfaces of the evaporator or forced :y pump or fan.

6



In some kinds of evaporator? the refrierant =ows in the tu:es and su:stance to :e

coo!ed surroundin it. &ut in other cases? su:stance to :e coo!ed in the tu:es and the

refrierant is in the she!!.

+vaporator are a!so c!assi1ed into =ooded type and dry e,pansion type? dependin on

whether the refrierant covers a!! the surface of heat transfer or some portion of heat

transfer surface is havin as :ein superheated.

Centrifugal evaporator A centrifugal evaporator is a device used in chemical and biochemical laboratories for the efficient

and gentle evaporation of solvents from many samples at the same time, and samples contained in

microtitre plates. If only one sample required evaporation then a rotary evaporator is most often

used. The most advanced modern centrifugal evaporators not only concentrate many samples at the

same time, they eliminate solvent bumping and can handle solvents with boiling points of up to 220

!. This is more than adequate for the modern high throughput laboratory.

Figure #: Cutaway image of H"$#% Centrifugal &vaporator

'anfactures:

!entrifugal evaporators were invented in "#$0s by %avant Inc of &%A, with their mar'et leading

%peed(ac brand. )ther well 'nown manufacturers of centrifugal evaporators are the *erman

company +artin !hrist, abconco !orp. of &%A and *enevac of &-.

(otary evaporator A rotary evaporator or rotavap/"1rotovap is a device used in chemical laboratories for the efficient

and gentle removal of solventsfrom samples by evaporation. 3hen referenced in the chemistry

research literature, description of the use of this technique and equipment may include the phrase

4rotary evaporator4, though use is often rather signaled by other language e.g., 4the sample wasevaporated under reduced pressure4.

$

https://en.wikipedia.org/wiki/Rotary_evaporator


https://en.wikipedia.org/wiki/Bumping_(chemistry)

https://en.wikipedia.org/wiki/Rotary_evaporator#cite_note-HarwoodMoodyEOCPAP-1

https://en.wikipedia.org/wiki/Chemical

https://en.wikipedia.org/wiki/Solvent

https://en.wikipedia.org/wiki/Evaporation




https://en.wikipedia.org/wiki/Bumping_(chemistry)

https://en.wikipedia.org/wiki/Rotary_evaporator#cite_note-HarwoodMoodyEOCPAP-1

https://en.wikipedia.org/wiki/Chemical





Figure ): * +,chi (otavapor ($2-- with ./. assem0ly vertical water condenser3

+aground

A simple rotary evaporator system was invented by yman !. !raig./2

It was first commercialized bythe %wiss company 56chi in "#78. )ther common evaporator brands are 9eidolph, abTech, %tuart,

9ydrion %cientific, %:;!), I-A and :<:A. In research the most common form is the " bench=top

unit, whereas large scale e.g., 20=70 versions are used in pilot plants in commercial chemical

operations.

4esign

The main components of a rotary evaporator are>

". A motor unit that rotates the evaporation flas' or vial containing the user?s sample.

2. A vapor duct that is the a@is for sample rotation, and is a vacuum=tight conduit for the vapor

being drawn off the sample.

. A vacuum system, to substantially reduce the pressure within the evaporator system.

B. A heated fluid bath generally water to heat the sample.

'

https://en.wikipedia.org/wiki/Rotary_evaporator#cite_note-2

https://en.wikipedia.org/wiki/Heidolph


https://en.wikipedia.org/wiki/Vacuum

https://en.wikipedia.org/wiki/Rotary_evaporator#cite_note-2


https://en.wikipedia.org/wiki/Vacuum



7. A condenser with either a coil passing coolant, or a 4cold finger 4 into which coolant mi@tures

such as dry ice and acetone are placed.

$. A condensate=collecting flas' at the bottom of the condenser, to catch the distilling solvent

after it re=condenses.

8. A mechanical or motorized mechanism to quic'ly lift the evaporation flas' from the heating

bath.

The vacuum system used with rotary evaporators can be as simple as a water aspirator with a trap

immersed in a cold bath for non=to@ic solvents, or as comple@ as a regulated mechanical vacuum

pump with refrigerated trap. *lassware used in the vapor stream and condenser can be simple or

comple@, depending upon the goals of the evaporation, and any propensities the dissolved

compounds might give to the mi@ture e.g., to foam or 4bump4. !ommercial instruments are

available that include the basic features, and various traps are manufactured to insert between theevaporation flas' and the vapor duct. +odern equipment often adds features such as digital control

of vacuum, digital display of temperature and rotational speed, and vapor temperature sensing.

Flooded evaporators

=ooded evaporator type with =oat contro! va!ve shown in 1. the !iAuid =ow on !ow

passaes passes the tu:es upwords? and :oi!s due to heat adsorption from the warmer

su:stance? which is coo!ed. The resu!ted vapor so formed on :oi!in :u::!es up in =ash

cham:er? where separates !iAuid from vapor.

Separated vapor passes to compressor? and !iAuid =ows :ack to the evaporator. The

=ash cham:er co!!ects the vapor formed :y !iAuid refrierant :oi!in in the evaporator?

and vapor o:tained in the e,pansion device.

In a =ooded type evaporator refrierant !iAuid !eve! is maintained. )!oat va!ve is used as

thrott!in device.

The heat transfer eciency increases :ecause the entire surface is in contact with the

!iAuid refrierant. &ut the refrierant chare is re!ative!y !are as compared to dry

e,pansion type.

The accumu!ator or =ash cham:er is used to prevent !iAuid Cray over to compressor.

The evaporator coi! is contacted to accumu!ator and the !iAuid =ow from the

accumu!ator to the evaporator coi! is enera!!y :y ravity. The vapor formed :y the

vapori@in of the !iAuid in the coi! :ein !ihter rises up and passes on to the top of the

accumu!ator from where it enters the suction !ine.

*

https://en.wikipedia.org/wiki/Condenser_(heat_transfer)

https://en.wikipedia.org/wiki/Cold_finger

https://en.wikipedia.org/wiki/Condenser_(heat_transfer)

https://en.wikipedia.org/wiki/Cold_finger



In some cases !iAuid e!iminators are provided in the accumu!ator top to prevent the

possi:!e carry over of !iAuid to suction !ine. !so a !iAuid suction heat e,chaner is used

on the suction !ine to superheat the suction vapor.

Figure 5: 6ooded evaporator

4irect &xpansion Coil &vaporator

the evaporator is ca!!ed direct e,pansion evaporator if the coi!s of the evaporator with

refrierant passin throuh them are used direct!y to coo! air :y natura! or forced

convection.

To improve the !u:ricatin oi! return to the compressor? the refrierant feed comes

throuh the thermostatic e,pansion va!ve more often !ocated at the top particu!ar!y for

)-/? )//. ir is :!own over the outside of the 1nned tu:es.

The direct e,pansion coi! is preferred )or air conditionin purposes? where the

evaporator is very near to the compressors. This is direct method of coo!in the

su:stance and? therefore Auite e1cient. it is preferred to chi!! the water and pump it to

the aircoo!in coi!? when the coi! has to :e !ocated very far away from the compressor.

There is possi:i!ity of refrierant !eakae for !on distances? and the cost of therefrierant wou!d :e hih. !so the pressure drop in the !ine wou!d decrease evaporator

coecient of performance and eciency.

The e,pansion va!ve contro!s the rate of the refrierant to evaporator in such a way that

a!! the !iAuid is vapori@ed and the vapor is a!so superheated to a !imited e,tent. The

inside of evaporator is far from dry :ut wetted with !iAuid.

-



!! the same? this type is ca!!ed dry e,pansion to distinuish it from =ooded system and

a!so pro:a:!y :ecause :y the time the refrierant reaches the evaporator out!et it from

=ooded system and a!so pro:a:!y :ecause :y the refrierant reaches the evaporator

out!et it is no more wet :ut dry superheated vapor.

Figure 7: 4irect expansion coil evaporator

--



Figure 8: direct expansion evaporator

"ypes of evaporator used today

Circulation evaporatorsCirculation evaporators are a type of evaporating unit designed to separate mi@tures unable to be

evaporated by a conventional evaporating unit. !irculation evaporation incorporates the use of

both heat e@changers and flash separation units in conCunction with circulation of the solvent in order

to remove liquid mi@tures without conventionalboiling. There are two types of !irculation

:vaporationD ;atural !irculation :vaporators and Eorced !irculation :vaporators, both of which are

still currently used in industry today, although forced !irculation systems, which have a circulation

pump as opposed to natural systems with no driving force, have a much wider range of appropriate

uses.

-/

https://en.wikipedia.org/wiki/Evaporator

https://en.wikipedia.org/wiki/Heat_exchanger




https://en.wikipedia.org/wiki/Boiling


https://en.wikipedia.org/wiki/Evaporator






Figure 9: /ertical tu0e forced$circulation evaporator3

atural Circulation evaporators

In Natural Circulation evaporators, short vertical tubes, typically 1-2 m long and 50- 100 mm in

diameter, are arranged inside the tubes, and the product is concentrated. The concentrated liquid

falls back to the base of the vessel through a central annular section. A shell-and-tube heat

exchanger can be provided outside the main evaporation vessel to preheat the liquid feed. The most

common application for this type of unit is as a reboiler at the base of a distillation column. νNatural

Circulation evaporators

Figure 1-: atural Circulation evaporators

-3



Forced Circulation &vaporator

Forced Circulation Evaporator The forced circulation evaporator was developed for processing

liquors which are susceptible to scaling or crystallizing. Liquid is circulated at a high rate through the

heat exchanger, boiling being prevented within the unit by virtue of a hydrostatic head maintained

above the top tube plate. As the liquid enters the separator where the absolute pressure is slightlyless than in the tube bundle, the liquid flashes to form a vapor.

Figure 11: Forced Circulation &vaporator

Batch pan Evaporators

Batch pan Evaporators The batch pan evaporator is one of the simplest and oldest types of

evaporators used in food industry. Now-a-days it is outdated technology, but it still used in a few

limited applications, such as the concentration of jams and jellies where whole fruit is present and in

processing some pharmaceutical products. Up until the early 1960's, batch pan also enjoyed wideuse in the concentration of corn syrups. In batch pan evaporator the product is heated in a steam

jacketed spherical vessel. The heating vessel may be open to the atmosphere or connected to the

condenser and vacuum. The heat transfer area per unit volume is in batch pan evaporator is small.

Thus, the residence time normally is many hours. Therefore, it is essential to boil at low

temperatures and high vacuum when a heat sensitive or thermo degradable product is involved.

-4



Figure 12: +atch pan &vaporators

(ising ;lm &vaporator

Rising-film Evaporators These are considered to be the first 'modern' evaporator used in the industry,

the rising film unit dates back to the early 1900's. The rising film principle was developed

commercially by using a vertical tube heated from the outside with steam. Liquid on the inside of the

tube is brought to a boil, with the vapor generated forming a core in the center of the tube. As thefluid moves up the tube, more vapors are formed resulting in a higher central core velocity those

forces the remaining liquid to the tube wall.

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Figure 1!: (ising ;lm evaporator

Falling Film &vaporator

Falling-Film Evaporators The falling-film evaporators has a thin liquid film moving downward under

gravity on the inside of the vertical tubes. The design of such evaporators is complicated by the fact

that distribution of liquid in a uniform film flowing downward in a tube is more difficult to obtain than

an upward-flow system such as in a rising- film evaporator. This is accomplished by the use of

specially designed distribution or spray nozzles. The falling-film evaporators allow a greater number

of effects then the rising-film evaporator. The falling-film evaporator can handle more viscous liquids

than the rising film type. This type of evaporators is best suited for highly heat sensitive products

such as orange juice

-6



Figure 1#: Falling$Film &vaporators

(ising<Falling &vaporator

Rising/Falling Evaporator In the rising/falling evaporator, the product is concentrated by circulation

through a rising-film section followed by a falling-film section of the evaporator. The product is first

concentrated as it ascends through a rising tube section, followed by pre concentrated product

descending through a falling-film section, there it attains its final concentration.

Figure 1):(ising<Falling &vaporator

-$



'ultiple$e=ect evaporatorsFn!ike sin!estae evaporators? these evaporators can :e composed of up to seven

evaporator staes ;eects<. The enery consumption for sin!eeect evaporators is

very hih and is most of the cost for an evaporation system. Buttin toether

evaporators saves heat and thus reAuires !ess enery. ddin one evaporator to the

oriina! decreases enery consumption to 5. ddin another eect reduces it to33 and so on. heatsavinpercent eAuation can :e used to estimate how much

one wi!! save :y addin a certain amount of eects.

The number of effects in a multiple=effect evaporator is usually restricted to seven because after that,

the equipment cost approaches the cost savings of the energy=requirement drop.

Figure 15: 4ou0le$e=ect falling ;lm evaporator

!ondensing vapors from flash tan' 5" heat evaporator A2. "Ffeed, 2Fproduct, Fsteam, BFvapors

*gitated thin ;lm evaporators Agitated thin=film evaporation has been very successful with difficult=to=handle products. %imply

stated, the method quic'ly separates the volatile from the less volatile components using indirect

heat transfer and mechanical agitation of the flowing product film under controlled conditions. The

separation is normally made under vacuum conditions to ma@imize GT while maintaining the most

favorable product temperature, and to ma@imize volatile stripping and recovery.

Agitated thin=film evaporators are attractive for the concentration, distillation, stripping or deodorization of

liquids in a broad variety of chemical=process=industries !HI applications where the process streams aretemperature sensitive and must have only brief e@posure to heat, viscous, or tend to foul or foam.

-'



Figure 17: >ey element of vertical$thin evaporator

.

-*



Conclusion:Whi!e the desin criteria for evaporators are the same reard!ess of the industry

invo!ved? two Auestions a!ways e,ist# is this eAuipment :est suited for the duty? and

is the eAuipment arraned for the most ecient and economica! useJ s a resu!t?

many types of evaporators and many variations in processin techniAues have :een

deve!oped to take into account dierent product characteristics and operatin

parameters.

When you are in industry you reAuired a machine which is most ecient and

economica! for your need. So thats why there are many dierent types evaporator

avai!a:!e in market. +ach evaporator has its on advantae or disadvantae. +very

evaporator manufactures provide a chart with evaporator :asic temperature?

pressures and properties. There are varieties of evaporator from you can choosewhich evaporator is most appropriate for your Do:.

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Types of Evaporator in Air Conditioning