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    INDIAN

    INSTITUTE OFTECHNOLOGYBANARAS HINDU

    UNIVERSITY

    Project Report on

    Heat transfer and pressure drop

    characteristics of PHE Experiment and

    Data analysis

    Project undertaken by: Under Supervision of:

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    Ajay Sharma ( 11406EN007 ) Dr. J. Sarkar

    Vishal Khandelwal ( 11406EN009 ) Dr. P. Ghosh

    Table of contents

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    Introduction:For well over a century, eorts have been made to produce more ecientheat exchangers by employing various methods of heat transferenhancement. The study of enhanced heat transfer has gained seriousmomentum during recent years, however, due to increased demands by

    industry for heat exchange euipment that is less expensive to build andoperate than standard heat exchange devices. !avings in materials andenergy use also provide strong motivation for the development ofimproved methods of enhancement. "hen designing cooling systems forautomobiles and spacecraft, it is imperative that the heat exchangers areespecially compact and lightweight. #lso, enhancement devices arenecessary for the high heat duty exchangers found in power plants $i. e.air%cooled condensers, nuclear fuel rods&.

    The plate heat exchanger normally consists of corrugated platesassembled into a frame. The hot 'uid 'ows in one direction in alternatingchambers while the cold 'uid 'ows in true counter%current 'ow in theother alternating chambers. # schematic diagram of the 'ow is shown inFigure (. The 'uids are directed into their proper chambers either by asuitable gas)et or a weld depending on the type of exchanger chosen.

    Traditionally, plate and frame exchangers have been used almostexclusively for liuid to liuid heat transfer. The best example is in thedairy industry. Today, many variations of the plate technology haveproven useful in applications where a phase change occurs as well. Thisincludes condensing duties as well as vapori*ation duties. +late heatexchangers are best )nown for having overall heat transfer coecients$%values& in excess of -/ times the %value in a shell and tube designedfor the same service. +late heat exchanger is an attractive option whenmore expensive materials of construction can be employed. Thesigni0cantly higher %value results in far less area for a given application.

    The higher %values are obtained by inducing turbulence between theplate surfaces.

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    +late 1eat 2xchangers:The plate heat exchanger $+12& is a speciali*ed design well suited totransferring heat between medium% and low%pressure 'uids. "elded, semi%welded and bra*ed heat exchangers are used for heat exchange between high%pressure 'uids or where a more compact product is reuired. In place of a pipepassing through a chamber, there are instead two alternating chambers,usually thin in depth, separated at their largest surface by a corrugated metalplate. The plates used in a plate and frame heat exchanger are obtained by

    one piece pressing of metal plates. !tainless steel is a commonly used metalfor the plates because of its ability to withstand high temperatures, its strength,and its corrosion resistance. The plates are often spaced by rubber sealinggas)ets which are cemented into a section around the edge of the plates. Theplates are pressed to form troughs at right angles to the direction of 'ow of theliuid which runs through the channels in the heat exchanger. These troughsare arranged so that they interlin) with the other plates which forms thechannel with gaps of (.-(./ mm between the plates.

    The plates produce an extremely large surface area, which allows for thefastest possible transfer. 3a)ing each chamber thin ensures that thema4ority of the volume of the liuid contacts the plate, again aidingexchange. The troughs also create and maintain a turbulent 'ow in theliuid to maximi*e heat transfer in the exchanger. # high degree ofturbulence can be obtained at low 'ow rates and high heat transfercoecient can then be achieved.# plate heat exchanger consists of a series of thin, corrugated plateswhich are mentioned above. These plates are gas)eted, welded or bra*edtogether depending on the application of the heat exchanger. The platesare compressed together in a rigid frame to form an arrangement ofparallel 'ow channels with alternating hot and cold 'uids.

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    #s compared to shell and tube heat exchangers, the temperatureapproach in a plate heat exchangers may be as low as ( 56 whereas shelland tube heat exchangers reuire an approach of / 56 or more. For thesame amount of heat exchanged, the si*e of the plate heat exchanger issmaller, because of the large heat transfer area aorded by the plates

    $the large area through which heat can travel&. Increase and reduction ofthe heat transfer area is simple in a plate heat%exchanger, through theaddition or removal of plates from the stac).

    7asic 6onstruction:The plate%and%frame or gas)eted plate heat exchanger $+12& consists ofa number of thin rectangular metal plates sealed around the edges bygas)ets and held together in a frame as shown. The frame usually has a

    0xed end cover $headpiece& 0tted with connecting ports and a movableend cover $pressure plate, follower, or tailpiece&. In the frame, the platesare suspended from an upper carrying bar and guided by a bottomcarrying bar to ensure proper alignment. For this purpose, each plate isnotched at the center of its top and

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    bottom edges. The plate pac) with 0xed and movable end covers is

    clamped together byFigure: 8as)eted plate% and%frame heat exchanger$ !hah and Foc)e,

    (9&.

    long bolts, thus compressing the gas)ets and forming a seal. The carryingbars are longer than the compressed stac), so that when the movableend cover is removed, plates may be slid along the support bars forinspection and cleaning.

    2ach plate is made by stamping or embossing a corrugated $or wavy&surface pattern on sheet metal. ;n one side of each plate, specialgrooves are provided along the periphery of the plate and around theports for a gas)et, as indicated by the dar) lines. Typical plate geometries$corrugated patterns& are shown in Fig, and over

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    rigidity of the plates and form the desired plate spacing. +lates aredesignated as hard or soft, depending on whether they generate a high orlow intensity of turbulence.

    Figure: +lates showing gas)ets around the ports $!hah and Foc)e, (9&.

    Flow #rrangements:

    # large number of 'ow arrangements are possible in a plate heatexchanger depending on the reuired heat transfer duty, availablepressure drops, minimum and maximum velocities allowed, and the 'ow

    rate ratio of the two 'uid streams. In each pass there can be an eual oruneual number of thermal plates.

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    Figure: Flow arrangement $ 8enemco, Inc. >==

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    reuirement for the exchanger. #lso, the gross weight of a plateexchanger is about one sixth that of an euivalent shell%and%tubeexchanger. @ea)age from one 'uid to the other cannot ta)e place unless aplate develops a hole. !ince the gas)et is between the plates, anylea)age from the gas)ets is to the outside of the exchanger. The highthermal eectiveness $up to about 9-A& facilitates economical low%grade

    heat recovery. The 'ow%induced vibrations, noise, thermal stresses, andentry impingement problems of shell%and%tube exchangers do not existfor plate heat exchangers.

    !ome inherent limitations of the plate heat exchangers are caused byplates andgas)ets as follows:

    The gas)et materials $except for the +TF2%coated type& restrict the use of+12s in highly corrosive applicationsC they also limit the maximumoperating temperature to >

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    ;b4ective of present study:

    The primary focus of the study is to 0nd the overall heat transfercoecient and pressure drop characteristics of +12. The wor) has been

    divided into to two phases:(. ecti0cation of the setup and performing the experiment with

    distilled water and obtaining the important results. The resultsobtained after full recti0cation of the setup will serve as referencesfor all the next steps of experimentation. The ob4ective also includederror analysis of the data.

    >. +erforming the experiment with dierent concentrations ofnano'uids with varying temperature and 'ow rate and compareexperimentally the heat transfer performances of various nano'uids.

    +erform data analysis using optimi*ation techniues and 0nd theoptimal values of various parameters for maximum heat transfercoecient.

    2xperimental !etup:

    #n experimental setup that was been developed by Gr. #. Tiwari, Gr. H.

    !ar)ar Gr. +. 8hosh has been used to investigate the heat transfer andpressure drop characteristics of the corrugated channels under dierent'ow conditions. 6ommercial +12 manufactured by #lfa @aval India @imited

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    $model 3- F8& has been used for this purpose. The geometric details ofthe plates and the heat exchanger are provided in Table and Figure below

    Table 8eometrical parameters of tested plate heat exchanger+late width inside gas)et, @w $mm& (==Bertical distance between centers of ports, @v $mm& -//1ori*ontal distance between centers of ports, @h $mm& & =.-3ean channel spacing, b $mm& >.8ap between two consecutive plate, $mm& >.K6orrugation pitch, +c $mm& (K.>+late thic)ness, t $mm& =./+late pitch, p $mm& >.8as)et width, $mm& L.K

    8as)et thic)ness, $mm& =.-L6hevron angle -= degrees

    Figure: 7asic geometric parameters of chevron plate $&The experimental setup mainly includes two 'ow loops, for the cold andhot 'uids $distilled water 'ow loops&. 1ot water loop comprises with aninsulated hot water tan) of >/ @ capacity with four > )" immersionheaters. The desired temperature of hot water inlet to the +12 has beencontrolled through temperature controller $ono control mechanism&. 1otwater has been circulated through +12 using gas)eted hot water pump.6old 'uid is stored in a (/ @ container and recirculated by means of acentrifugal pump. 7efore entering the +12, the cold 'uid is cooled so thatthe inlet temperature is maintained at a constant value. Two dierential

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    pressure manometers have been used between inlet and outlet ports ofthe +12 for hot water and cold water. The temperatures of each streamare measured using high accuracy H%type thermocouples located at theinlet and outlet of the cold and hot%water streams, respectively. The coldwater tan) and piping were thermally insulated properly to minimi*e heatloss. Four terminal temperatures and 'ow rates of hot water and cold

    water have been measured under steady state during experimentation.6old water 'ow rate has been varied from $-K& lpm whereas inlet coldstream temperature ranges from -/ to -L degrees celcius. 1ot stream'ow rate has been varied from $-K& lpm with readings noted at dierenthot water inlet temperature variying from

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    setup should have been used every - months so that there is no rust

    formation inside the 'ow system and no bloc)age due to the dirt.

    #s per the inspection performed initially and followed by testing of 'ow

    circuits with the distilled water without using the heating euipmentMs,

    following inferences were drawn %

    (& @ea)age in hot water circuit pump. +ossible reasons%

    >& ;ut of the - motors, motor > corresponding to the cooling watercirculation system was found not wor)ing. +ossible reasons %- 3anometer tapping lea)age was evident from various places.K& @ea)ages in the lin) between hot water container outlet and motor

    inlet./& 1ot water side manometer not wor)ing properly due to air bubbles inthe 'ow side. corresponding to the cooling water circulation system was

    removed and inspected.Following possible reasons for its collapse were identi0ed:a. !haft 4amb. 2lectrical connections

    The electrical connections were chec)ed 0rst and loose connections weretightened and chec)ed with electronic multimeter for assurance. Thisexercise revealed that electrical connections were o)ay and shaft 4am hadto be the reason for the dysfunction.

    The motor was ta)en up to the 0tting wor)shop and opened. The impellor

    was in perfect condition but the coupling the connected the fan withmotor was 4ammed. The following 0gures show the shaft coupling thatwas 4ammed.

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    !haft coupling +hotographThe seal that covered the 4oint was also hampered and neededreplacement. That brea)ing of the seal was the main reason for thelea)age. The shaft coupling was polished and grinded in the 0tting shop.

    The re%assembling of the parts of motors was done and then tested. The

    motor was then again 0tted bac) and all the connections were retained.

    >& The next problem that was tac)led was lea)ages in the hot watercircuit pump.Initial inspection laid us to following conclusion:

    a. 6oupler problemb. @oose inlet?outlet connection

    The problem was recti0ed same as the cooling water circulation pump.The only problem that still persists in the motor is overheating and the

    reasons are excessive vibration.

    -& 7oth 6old and 1ot water sides had lea)ages which on 0rst visualinspection concluded that many of the tapping were not properly 0xedwith the clips and there was a shortage of 6%clips that were bought. =Aof the lea)age problem was solved by this simple measures andremaining >= A reuired use of sealing agent and coverings.

    K& The bubbles of the hot water side were removed using the tappingtechniue and the system was made completely close with no bubbles./& The cold water manometer was the main cause of concern as due tothe large diameter of the pipe at the outlet of the plate, a very lowpressure *one was created due to partial 0lling of the pipe. The other halfof pipe contained air. This air had to be removed for correct pressurereadings. The decision had to be made on the liuid that had to be 0lled in themanometer. 6arbon tetrachloride was selected owing to its density $ (./Kg?cmN-&. The carbon tetrachloride is slightly denser than water and wasexpected to serve our purpose the best. #n additional tapping was made on the cold side to remove excessiveair and ma)e the system completely closed. This tapping was expected to

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    show. # pressure gauge was brought for the reference and it was foundthat the manometer had little less carbon tetrachloride. #n accurateamount of 'uid had be poured. This was done by a repetitive processwhich consisted of pouring and measuring. Finally and exact amount of'uid was poured. Jow the air bubbles were to be removed from thesystem. Tapping were held open until all the air bubbles were removed

    and manometer 'uid level was constantly monitored.;nce the complete system was made air bubble free, the referencepressure was set from the pressure gauge and the manometer wascalibrated.

    H%type thermocouple open 4unction problem:Thermocouple showed no numbers on the digital indicator. #fter a littleresearch it was )nown that the thermocouple circuit was open and had tobe removed from the tubes and recti0ed. The 4unction were removed and

    it was evident that the thermocouple were having a open 4unction assown below. The 4unctions were re4oined and made sure that they donEtfall apart again.

    ;pen 4unction Thermocouple

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    Hunction closed and secured

    H%type thermocouple calibration:

    A thermocouple is calibrated by comparing its response with a standard thermometer at the sametemperature. The standard thermometer may be another thermocouple, a platinum resistancethermometer or a liquid in glass thermometer.The thermocouples are calibrated by one or more ofthree general methods, depending on

    the type of thermocouple,

    the temperature range,

    the accuracy required.

    In the first method, thermocouples are calibrated by comparison with a reference thermocouple.Inthe second method, thermocouples are calibrated against a standard platinum resistancethermometer. In the third method, thermocouples are calibrated at four defining temperatures, thefreezing points of zinc, aluminum, silver, and gold.

    Calibration problem areas are immediately apparent. There must be available:

    eans for measuring the output of the temperature sensor

    !atisfactory temperature standard

    Controlled temperature environment

    The first method of calibrating the thermocouples was adopted with reference thermocouple wasdigital thermometer.

    The si" thermocouples #unctions were made na$ed and an intimate contact was made manuallyfrom hand assuring its e"istence inside the pipe under heavy flow conditions. The contacts werecoated with epo"y resin araldite that ensured the contact all the times between two metals. Thecompleted #unctions were calibrated at various temperature with a reference digital thermometer.%wing to the fact that thermocouples don&t follow the linear relationship with temperature gradient,the calibration had to be done over a range of temperature $eeping the error within '(.Thermocouple was calibrated at ) and *) degrees Celsius alternatively to ensure the errorremains within '(.

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    After calibration of thermocouples

    Calibration over a range of temperature

    After the calibration the thermocouple were put bac$ in the drilled holes. The holes were sealedand made air tight to restrict any passage of air in or out. After the cement got dried, thetemperature reading without heaters been operated were noted and the error was found to bewithin .+(.

    After the successful calibration of both manometer and thermocouple, heaters were beeninvestigated. The heaters were found to be in perfect condition.The additional thermocouple with control mechanisms were investigated and found perfect. Thesettings were made for the e"periment.

    After completion of the rectification a thorough inspection was done and all the thermocouples,manometers were double chec$ed.

    -"periment was performed at this stage and data analysis was done on e"cel. arious graph ofimportant parameters have been plotted which are shown under results and discussions part.The various data and calculations have attached in the anne"ure with relevant names.

    esults and Giscussions:

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    6onclusion:Future wor)

    #fter successful completion of the 0rst phase of pro4ect, we loo) forward

    to ta)e our much gained experience further. "e intend to perform the

    experiment with dierent concentrations of nano'uids and use

    optimi*ation techniue to arrive at optimal solution of overall heat

    transfer coecient for given set of variables.

    The data and the results of the above wor) would be used as a reference

    and validation for the next set of results. ;ur 0nal ob4ective is to 0nd the

    optimi*ed set of parameters for maximum heat transfer coecient of the+12.

    eferences: