Comparison between four types of heat exchangers Sam kk / / February 15, 2012
We come across heat management and controlling during a design of any mechanical or chem chemic ical al unit unit equi equipm pmen ents ts.. A phys physic ical al and and chem chemic ical al chan change ge ino inol les es some someho ho! ! the the application of heat e"changer in order to maintain the temperature as per the condition to run the system. #"change of heat of the $uid system from a point to other point of interest interest is done using a piece of equipment called heat e"changer and of course it may di%er from the application but ultimate principle behind it !or&ing is same. 'heory behind heat e"changer e"changer is simple, (ust the allo!ing heat energy to $o! in perfectly designed system by means of conduction, conection in case of $uids and !hen dealt !ith direct )ring radiation !ill be inoled. We discuss about four main types of heat e"changers e"changers by comparing their application, capacity and range of duty !hich are classi)ed based on the $o! pattern of $uid in them. 1. 2. . -. Plate
*lat *late e heat heat e"c e"cha hang nger er +hell +hell and and tube tube heat heat e"cha e"change ngerr Fin type type hea heatt e"c e"cha hange ngerr 'ubula ubularr heat heat e"c e"chan hanger ger type heat exchanger
*late heat e"changer t is an arrangement of plates side by side )"ed along !ith gas&ets. #ach plate !ill be haing four opening ports, a gas&et gas&et !hich is )tted bet!een t!o ad(acent plate !ill ma&e the $uid to $o! bet!een t!o ports by bloc& remaining ports, to imagine a rectangle plate haing four holes near at its edges and these are )"ed in such a !ay that gas&et bet!een plate ma&e a enough room for $uid to $o! and change the direction of as required. 'his operates $uids in counter current !ise for attaining ma"imum heat e"change.
t has advantages !hich advantages !hich oercome other heat e"changer are egligible heat loss oerall !eight of set set is less Fits in less space ess maintenance cost and erall heat transfer coe3cient is more #asy installation Disadvantages: ot compatible for higher temperature and pressure say aboe 200 o4 and 20 bars. Application: sed in oil cooling cooling system system in automobil automobiles, es, steam steam condensa condensations tions,, s!imming s!imming !ater cooling systems, refrigeration refrigeration systems. Shell and tube heat exchanger t contains tubes inside a shell !hich is basic and basic design of heat e"changers, it is heay heay duty duty equipm equipment ent !hich !hich is !idely !idely used used in proce process ss indust industri ries es it can handle handle higher higher temperature up to 600 degree centigrade7s een more. • • • • • •
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'emperatur 'emperature e of $uids are ma"imum at !all than the $o!ing stream and the heat has to redistribute eenly, ba8e arrangement ma&e the $o! some!hat turbulent for better heat transfer disturbing the boundary layer and supporting the tube also. n most cases hot $uid li&e steam if fed to!ards tube side and cold $uid is sent into shell side of shell and tube heat e"changer. 9ased on the design and pattern of $o! of $uid internally internally it can be classi)ed as single pass, 1:2 pass, 2:- pass, $oating head heat e"changers;inter e"changers;internal nal $oating head and outside pac&ed $oating head<, )"ed tube sheet, :tube types . t accomplish the duty of condenser !hen it function is to cool a stream and similarly it operates as reboiler !hen used for changing the phase of the stream. t operates in countercurrent and cocurrent $o! pattern and their approach !ill di%er for same equipment. +=# A> '9# =#A' #?4=A@# 4A4A' Advantages: 4an handle heay duty and high temperature and pressures #asy control and operate:able Disadvantage: equired large space Baintenance cost is more Application: sed Application: sed as regular heat e"changer for distillation columns, chemical equipment7s stream cooling and heating purpose. sed internally in reboilers and eaporators. • •
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Fin type heat exchanger 'hese are called as e"tended surface e"changers e"changers it is used in the conditions !here !hen a process $uid is haing ery lo! heat transfer coe3cient !hen compared to other $uids because the oerall heat transfer coe3cient decreases !hich a%ect the capacity of heat transfer by the aailable surface area so the area of contact is to be increase. We come across across this type of problem problem !hen heat transfer transfer is dealt dealt !ith heating heating of air or gas streams streams and for cooling iscous liquids li&e engine oil.
A metal piece is !elded to the surface of the tube to increase the surface are !hich are called as )n and mostly found on outside of the tube. Fin type heat e"changer is classi)ed classi)ed to longitudinal )ns type and transerse )ns type Advantages: se to handle lo! heat transfer coe3cient $uids sed for cooling and heating of ast quantity of gases Disadvantage: +lurry $uids cannot be handled >eposition of particle at )n corner 4leaning di3culty =igh pressure drop Application: sed Application: sed as economiCers, automobile radiators, radiators, air cooled condensers Tubular heat exchanger t is a pipe in pipe heat e"changer commonly &no!n as double pipe heat transfer equipment !hich is named by its construction because t!o pipes are pipes are )tted in such !ay that one pipe is )tted into other inside space. 9y cross section they loo& concentric by coa"ial ie!. ie!. t is e"tended to the required required length and bent li&e hair pin shape at the edges to ma&e it )t in particular area. =ot $uid is fed into the inner tube and cold $uid is fed into the space bet!een inner and outer pipes. • •
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'he tubular condenser consists consists of 1. A bundle bundle of parallel parallel tubes tubes !hose !hose ends ends are e"pan e"panded ded into into tube sheets. sheets. 2. 'he tube bundle is inside a cylindrical cylindrical shell and is proided proided !ith t!o channels, one at each end ,and t!o channel coers. . +team or other pure pure apour is introduced introduced into the shell:side shell:side surrounding surrounding the tubes, condensate is !ithdra!n from the shell. -. Any non:con non:condens densable able gas is is remoed remoed through through ent. ent. 5. 'he $uid $uid to be heated heated is pumpe pumped d through through the the tubes. tubes. D. '!o $uids ;$uid, ;$uid, steam< are are physically physically separated separated but are are in thermal thermal contact contact !ith the thin metal tube separating them. E. =eat $o!s through the the tube !alls !alls from from the condensing condensing apor apor to the cooler $uid in the tubes. . Fluid $o!ing $o!ing in the tube side gain heat heat and increase increase it temperature temperature from from inlet to to outlet of the tubes. 6. 'he temperature temperature of the shell side $uid $uid is constant constant for the the pressure pressure maintained on the shell side. 10. ' 10. 'ypes ypes of $o!s in heat e"changer e"changer Advantages: #asy in construction 4an handle slurries 4an be used at lo! heat transfer areas 4heap #asy cleaning 4oncurrent and counter current $o! can be ad(usted easily Disadvantages: ea&age corners Baintenance is time consuming ccupy more $oor space compared to others Application: sed Application: sed for refrigeration process in appliance li&e refrigerators, domestic heating systems and car radiators etc. • • • • • •
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