study of heat exchangers in different hydraulic circuits in hsm

7/31/2019 Study of Heat Exchangers in Different Hydraulic Circuits in Hsm

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Study of Heat Exchangers in Different Hydraulic Circuit in HSM

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A

ON

PROJECT GUIDE: SUBMITTED BY:Mr. Braj Kishor Kumar Arindam Paul

HSM Dept. SP No. VT0512134151


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It has been an immense pleasure and truly enriching experience doing my vocational

training at TATA STEEL Ltd., Jamshedpur. I take this opportunity to thank all those

people who have made this experience a memorable one. First, I would like to thank myguide Mr. BRAJ KISHOR KUMAR, HSM, who has been the guiding force behind the

completion of this project and correcting various documents of mine with utmostattention and care. He ensured necessary correction as and when needed. I am heartilythankful to Mr.M. B. VICTOR JOSEPH and also thankful toMAYANK PANDEYfor

their co-operation, valuable support and proper guidance whenever I approached them in

any problem. I am sincerely thankful to all staff members of HSM Dept. for theirvaluable help and guidance in the completion of my training.

Finally, I am grateful for the support from TATA STEEL Ltd. as a whole for the

opportunity and assistance they provided me to do my training here.


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This report prepared at TATA STEEL Limited, Jamshedpur contains a detailed

description of plate type Heat Exchangers in different hydraulic system in HSM Dept.

The details of the project done as a part of practical training along with the details of the

methodology and procedure adapted as a part of the project work is also presented in this

report.


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1.TITLE OF THE PROJECT :

2. DURATION OF THE PROJECT : 15-May-2012 TO 12-June-2012

3. PROJECT GUIDE AT DEPT. : Mr. Braj Kishor Kumar

4. NAME OF THE TRAINEES : Mr. Debarpan Saha

: Mr. Arindam Paul

: Mr. Soumya Kanti Mandal

: Mr. Neeraj Kumar Singh


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This is to certify that MMrr.. AArriinnddaamm PPaauull, SP No-VT0512134151,

Ref. No. VT20120025 has successfully completed his project at H.S.M.

from 15th

May, 2012 to 12th

June, 2012. He has participated in a project

titled

. He has worked on the above subject and successfully

completed it. He is a diligent trainee of his batch and also an excellent

team man. I wish him well in his future endeavors.

Braj Kishor Kumar (Project Guide)

Manager, HSM Mechanical


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Table of contents

1. WHAT IS HEAT EXCHANGER...72. FUNCTION OF HEAT EXCHANGER.7

3. WORKING PROCEDURE84. TYPES OF HEAT-EXCHANGER.94.1. PARRALEL FLOW, COUNTER FLOW & CROSS FLOW9

4.2. SHELL & TUBE TYPE HEAT EXCHANGER.114.2.1. THEORY & APPLICATIONS.11

4.3 .PLATE TYPE HEAT EXCHANGER.12

5. DIFFERENT PARTS OF PLATE TYPE HEAT-EXCHANGER & ITS WOKINGPRINCIPLE13

5.1. DIFFERENT PARTS OF PLATE TYPE HEAT-EXCHANGER...13

5.2. PROCESS OF HEAT TRANSFER THROUGH CHANNEL PLATES.15

5.3. PRESSURE DROP-PROBLEM OF HEAT TRANFER THROUGH CHANN-

EL PLATES..165.4. DIFFERTENT TYPES OF PLATE TYPE HEAT-EXCHANGER..16

5.4.1. PARRALEL FLOW TYPE HEAT-EXCHANGER.165.4.2. DIAGONAL FLOW TYPE HEAT-EXCHANGER17

6. ADVANTAGES OF PLATE TYPE HEAT EXCHANGER18

7. GENERAL BLOCK DIAGRAM OF HYDRAULIC SYSTEMS20

8. HOW HEAT-EXCHANGER IS USEFUL IN HYDRAULIC SYSTEMS .219. STUDY OF DIFFERENT HEAT EXCHANGERS IN HSM DEPT.,TATA

STEEL LTD..25

10. CONCLUSION28


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Heat exchangers are the devices those facilitate the exchange of heat between the

two fluids that are at different temperature while keeping them from mixing with each

other. Heat exchangers are commonly used in practice in a wide range of applications,from heating and air-conditioning system in a household to chemical processing and

power production in large plants. Heat exchangers differ from mixing chambers in that

they do not allow the two fluids involved to mix. In a car radiator, for example, heat istransferred from the hot water flowing through the radiator tubes to the air flowing

through the closely spaced thin plates outside attached to the tubes.

Heat transfer in a heat exchanger usually involves convection in each fluid and

conduction through the wall separating the two fluids. In the analysis of heat exchangers,it is convenient to work with an overall heat transfer coefficient (U) that accounts for the

contribution of all these effects on heat transfer.

The rate of heat transfer between the two fluids at a location in a heat exchanger depends

on the magnitude of the temperature difference at that location, which varies along theheat exchanger. In the analysis of heat exchangers, it is usually convenient to work with

the logarithmic mean temperature difference LMTD, which is an equivalent mean

temperature difference between the two fluids for the entire heat exchanger.


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The basic principle of heat exchanger is the energy flow between hot and cold

streams. As a result the temperature of the hot fluid decreases increasing the temperature

of the cold fluid. Normally the hot and cold streams are separated by a solid medium (in

case of wall separating heat exchanger) which must have high conductivity. Heat transfermode is by convection at two surfaces of the solid medium which are exposed to the hot

and cold fluid and by conduction across the solid medium. For the efficient heat transferprocess the thermal resistance for these conductive and convective heat transfers should

be as low as possible. Proper design of the flow and the material of the solid medium

reduce the thermal resistance. The proper choice of flow direction also improves theefficiency (ex. in counter flow the temperature difference between hot and cold fluid is

higher compared to parallel flow at any position, thus equivalent temperature difference

is also higher).Heat exchanger also may be of radiative type which involves radiative heat

transfer.


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The classification of heat exchanger is shown in the above chart. There are other heat

exchangers like-

1. Adiabatic wheel heat exchangers

2. Plate fin heat exchangers

3. Fluidized bed heat exchangers

4. Spiral heat exchangers

5. Phase-change heat exchangers

Parallel and counter flow provide alternative arrangements for certain specialized

applications. In parallel flow both the hot and cold streams enter the heat exchanger at the

same end and travel to the opposite end in parallel streams. Energy is transferred along

the length from the hot to the cold fluid so the outlet temperatures asymptoticallyapproach each other. In a counter flow arrangement, the two streams enter at opposite

ends of the heat exchanger and flow in parallel but opposite directions. Temperatures

within the two streams tend to approach one another in a nearly linearly fashion resultingin a much more uniform heating pattern. Shown below the heat exchangers are

representations of the axial temperature profiles for each. Parallel flow results in rapid

initial rates of heat exchange near the entrance, but heat transfer rates rapidly decrease asthe temperatures of the two streams approach one another. This leads to higher exergy

HeatExchanger

Contact basis Physically On the basis offlow direction

Direct Contact WallSeparating

Streams

Plate type Shell & tubetype

Parallel flow Counter Flow Cross Flow


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loss during heat exchange. Counter flow provides for relatively uniform temperature

differences and, consequently, lead toward relatively uniform heat rates throughout thelength of the unit.

Another type of heat exchanger, which is specifically designed to realize a large heattransfer surface area per unit volume, is the compact heat exchanger. In compact heat

exchangers, the two fluids usually move perpendicular to each other, and such flow

configuration is called cross-flow. The cross-flow is further classified as unmixed and

mixed flow, depending on the flow configuration, as shown in following Figure. In (a)the cross-flow is said to be unmixed since the plate fins force the fluid to flow through a

particular interfin spacing and prevent it from moving in the transverse direction (i.e.,

parallel to the tubes). The cross-flow in (b) is said to be mixed since the fluid now is freeto move in the transverse direction. Both fluids are unmixed in a car radiator. Thepresence of mixing in the fluid can have a significant effect on the heat transfer

characteristics of the heat exchanger.


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A shell and tube heat exchangeris the most common type of heat exchanger in oil

refineries and other large chemical processes, and is suited for higher-pressure

applications. As its name implies, this type of heat exchanger consists of a shell (alarge pressure vessel) with a bundle of tubes inside it. One fluid runs through the tubes,

and another fluid flows over the tubes (through the shell) to transfer heat between the two

fluids. The set of tubes is called a tube bundle, and may be composed by several types oftubes: plain, longitudinally finned, etc.

Two fluids, of different starting temperatures, flow through the heat exchanger. One

flows through the tubes (the tube side) and the other flows outside the tubes but inside the

shell (the shell side). Heat is transferred from one fluid to the other through the tube walls,

either from tube side to shell side or vice versa. The fluids can be eitherliquids or gases on either the shell or the tube side. In order to transfer heat efficiently, a

large heat transfer area should be used, leading to the use of many tubes. In this way,waste heat can be put to use. This is an efficient way to conserve energy.

Heat exchangers with only one phase (liquid or gas) on each side can be called one-phase

or single-phase heat exchangers. Two-phase heat exchangers can be used to heat a liquid

to boil it into a gas (vapor), sometimes called boilers, or cool a vapor to condense it into aliquid (called condensers), with the phase change usually occurring on the shell side.

Boilers in steam engine locomotives are typically large, usually cylindrically-shaped

shell-and-tube heat exchangers. In large power plants with steam-driven turbines, shell-and-tube surface condensers are used to condense the exhaust steam exiting the turbine

into condensate water which is recycled back to be turned into steam in the steamgenerator.


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Plate and frame (or just plate) type heat exchanger has found widespread use, whichconsists of a series of plates with corrugated flat flow passages. The hot and cold fluids

flow in alternate passages, and thus each cold fluid stream is surrounded by two hot fluid

streams, resulting in very effective heat transfer. Also, plate type heat exchangers can

grow with increasing demand for heat transfer by simply mounting more plates. They arewell suited for liquid-to-liquid heat exchange applications, provided that the hot and cold

fluid streams are at about the same pressure.


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1. SUPPORT COLUMN:-The two bars are suspended between theframe plate, to which in most cases the piping isconnected, and a support column.

2.CONNECTIONS:-Holes matching the piping lead through the frame plate, permitting the media to enterinto the heat exchanger. Threaded studs around the holes secure the pipes to the

equipment. Depending on the application, metallic or rubber-type linings may protect the

edges of the holes against corrosion.

3. TIGHTENING BOLTS:-With the package of thin plates hanging between the frame plate and the pressure plate, a

number oftightening bolts are used to press the thin plates together bringing them intometallic contact, and to compress the gaskets enough to seal off the narrow passages

which have now been formed between the plates.

5. GUIDING BAR:-The plates hang from a carrying barat the top and are kept in line by a guiding barat the

bottom.


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6. GASKET:-These plates are called channel plates. A groove along the rim of the plate and around theports hold a gasket, usually made of a rubber-type material. Heat is transferred through

the surface which is contained by the gasket, except for some small areas near the corners.

The number of plates in your heat exchanger is determined by the size of the heat transfer

surface required.

The GASKET is molded in one piece. The material is normally an elastomer, selected to

suit the actual combination of temperature, chemical environment and possible other

conditions that may be present

Different parts of gasket:-

The one-piece gasket consists of:1. One field gasket

2. Two ring gaskets

3. Links

The field gasket is by far the larger part containing the whole heat

transfer area and the two corners connected to it. The ring gaskets

seal off the remaining two corners.

These three pieces are held together by a few short links, which haveno sealing function at all. Their purpose is simply to tie the pieces

together and to add some support in certain areas. On some plate

heat exchangers, the gasket is held in place on the plate by means ofa suitable cement or glue.


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Functions of parts of gasket:-

As already demonstrated, the two media are effectively kept apart by the ring and

field gaskets. To prevent intermixing of the media in the corner areas where field and ring

gaskets are very close to each other, the link pieces have a number of slots which opensthe area between the field and ring gaskets to atmosphere. Any leakage of media across

either gasket will escape from the heat exchanger through the slots.

Precautions using gaskets:-

It is important that these openings are kept clear. If they are not, there is a risk thatshould a leak occur in that region of the plate, there might be a local pressure build-up,

which could allow one medium to mix with the other. Care should be taken not to cut or

scratch the gaskets while handling plates.

The purpose of the equipment is to transfer heat from one medium to another. Heat

passes very easily through the thin wall separating the two media. The novel pattern into

which the plate material has been formed not only gives strength and rigidity, but greatly

increases the rate of heat transfer from the warmer medium to the metal wall and from thewall to the other medium. This high heat flow through the walls can be seriously reduced

by the formation of deposits of various kinds on the wall surfaces. The pattern of

corrugation on plates induces highly turbulent flow.

The turbulence gives strong resistance to the formation of deposits on the plate surface;

however, it cannot always eliminate fouling. The deposits may increase the total wall

thickness substantially, and they consist of materials that have a much lower thermal


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conductivity than the metal plate. Consequently a layer of deposits can severely reduce

the overall heat transfer rate.

Pressure drops are wasted energy. All pipe systems and equipment included in themoffer resistance to media flowing through them. Some pressure drop is unavoidable, but

for a given PHE it should be kept as close as possible to the designed value. Theformation of deposits on the heat transfer surfaces instantly leads to a reduction of the

free space between the plates. This means that more energy is needed to get the desired

flow through the equipment.

Plate type heat exchangers are generally classified in twocategories depending upon the direction of flow-

Parallel flow

Diagonal flow

When a package of plates are pressed together, the holes at the corners form continuous

tunnels or manifolds, leading the media (which participate in the heat transfer process)from the inlets into the plate pack, where they are distributed in the narrow passages


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between the plates. Because of the gasket arrangement on the plates, and the placing of

A and B plates alternately, the two liquids enter alternate passages, e.g. the warmliquid between even number passages, and cold liquid between odd number passages.

Thus the media are separated by a thin metal wall. In most cases the liquids flow in

opposite directions. During the passage through the equipment, the warmer medium will

give some of its heat energy to the thin wall, which instantly loses it again to the coldermedium on the other side. The warmer medium drops in temperature, while the colder

one is heated up. Finally, the media are led into similar hole-tunnels at the other end of

the plates and discharged from the heat exchanger.

The working principle of diagonal flow plate type heat exchanger is same as parallel flow

plate type heat exchanger. The difference between them is the direction of flow of water

and oil between two plates. The direction of oil and water is shown in the above figure.The heat exchange between oil and water is more than the parallel flow plate type heat

exchanger.


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Compact design delivers greater efficiency

With densely-packed surface area and overall superior thermal efficiency, platetype Heat Exchangers use up to 80% less floor space and often weigh 10 times less than

shell-and-tube exchangers. Plus, they use less surface area to transfer the same heat. That

makes them easier, safer, faster, more efficient and far more economical to ship, handle,install and use.

Close temperature approachIn the plate type heat exchanger two fluids can be delivered due to true

countercurrent flow, which directs the two media in opposite directions across the plate.

This results in maximum temperature differences and minimum heat transfer surface

requirements. In fact, temperature approaches as close as 1 to 2F can be obtained.

No cross-contaminationDue to the gasket design of the Plate Heat Exchanger units are well-suited to

applications where inter-leakage is a critical concern. Hot and cold media circuits are

individually gasketed with the area in between vented to the atmosphere, assuring the

integrity of both circuits.

Low hold-up volumePlate Heat Exchanger users enjoy shorter response times and more accurate process

control. This advantage is the direct result of inherent design considerations that allow for

an internal volume of up to 80% less than tubular designs.

Minimum FoulingUniform flow and high fluid turbulence is achieved due to the design of plates

which also minimizes fouling. The continual scrubbing action taking place in this type of

heat exchangers eliminates the need for frequent cleanings required by other types of heat

exchangers.

Ease of maintenanceThis is due in large part to reduced fouling, but, in addition, low media holdup also

allows for easy drainage. Since connections are usually made to the front of the unit,piping can stay in place when the unit is opened, and all of the components can be

removed within the length of the frame, minimizing downtime.

ExpandabilityPlate Heat Exchangers are designed to expand with heat transfer needs. It can be

done by simply loosening the compression bolts and adding the plates what are needed.

That's flexibility is far beyond the fixed capacity of other exchangers which would berendered obsolete in similar circumstances.


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FlexibilityThe widest variety of plate sizes helps us deliver maximum economy for any size

application. Because of the variety of plates sizes is offered, the most economical designs

for all types of heat transfer applications is provided.Several plate sizes for each

connection size is also provided. In addition, plates are pressed in the patterns that arebest suited to optimizing the performance of the system. By combining the right plate

geometry, patterns and connections the heat exchanger can be customized to achieve a

design that is ideal for application.


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There are many reasons which are responsible for the generation of heat in any

hydraulic or fluid system. Fluid systems generally produce heat by converting mechanical

energy or fluid pressure energy. Friction is the process of conversion because molecularfriction generates heat in a sheared fluid.

Effect of high viscosity of the working fluid

The higher the viscosity of the working fluid, the more heat this friction

produces because of higher frictional resistance. For example, frictional drag acts on the

fluid as it courses through orifices, restricted passages etc. But viscosity is greatly

affected by the temperature. Generally higher the temperature, lower the viscosity and

vice-versa.

The heat generated by the friction is either dominated by the cold atmospheric conditionor not causing two different results which are following.


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Effect of Low viscosity of the working fluid

Low viscosity fluid also contributes to heat generation because it inherently fails to

maintain a crucial lubrication film between moving surfaces. This failure to separate the

running surfaces results not only in wear (abrasion and adhesion of the two surfaces) butalso in excessive leakage. The resulting wear increases the frictional loss and the rise of

temperature of the working fluid. A viscous cycle of thermal failure is shown in the

which shows how the rise in temperature is gradually assisted by lowering the viscosityof the working fluid.


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Viscous Cycle of Thermal Failure

The effect of the temperature rise

The result of the frictional effect first causes the loss of energy in terms of heat.

The heat which is dissipated increases the temperature of the working fluid graduallywith the number of cycle. There are some other reasons of temperature rise like hotatmospheric condition, presence of any heat source near the hydraulic system etc. which

assist the viscous cycle of thermal failure.No matter how careful designers of fluid systems are, excessive heat generation

sometimes occurs. If a machine like a hydraulic system has an overall efficiency of 80

percent, rough approximations would indicate that the amount of generated heat for an

average fluid system is equal to 20 percent of the connected shaft power. This heat must

be dissipated to the surroundings in some way, otherwise the fluid temperature will keeprising until the system either stabilizes (where the heat dissipated to the environment

balances the heat generated by the system) at some undesired elevated temperature ordestroys itself. When the rise in temperature crosses particular limit oil gets hot and

breaks down. It looks dark and smells burnt. Thermally degraded oil is thinner and much

less slippery than new oil definitely fails to serve its purpose further. So in everyhydraulic system it is required to maintain the temperature of the working fluid within a

working range.


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Heat exchanger for maintenance of temperature within a range

The first avenue of escape from generated heat is by natural dissipation. With

natural cooling, heat in the system fluid dissipates into the surrounding air, primarily by

conduction and convection. But in most of the cases it is not enough to serve the purposein the industry. to relieve the system fluid of excess heat and lower its operating

temperature heat exchangers are used. It uses coolant medium and involves the transfer of

heat from the working fluid to reduce its temperature. Thus it can used again for thesubsequent cycles.


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Hydrauliccellar

Heatexchanger

specification

No. ofplates

as percircuit

No. ofplates

found

Platepacked

lengthfound

Maximumworking

pressure

Oilinlet

temp.

Oiloutlet

temp.

Waterinlet

temp.

Wateroutlet

temp.

Purposeserved

to

H1 Type- P2-FHSerial No.-

30107-76-777

Capacity-

50.2 kW

31 98 330 mm 10kg./sq.cm. 33

oC 31.5oC 25oC 27oC Slab

charging

H2 Type- P2-FH

Serial No.-

30101-61-584

Capacity-

50.2 kW

31 31 110 mm 6

kg./sq.cm.

25oC 24

oC 20.5

oC 22.5

oC Slab

dischargi

ng

H3 Type- P2-FH

Serial No.-30101-73-719

Capacity-

60 kW

38 68 246 mm 10

kg./sq.cm.

37oC 33

oC 23

oC 26

oC Edger

roughingMill

H4 Type- P2-FH

Serial No.-

30101-61-586

Capacity-

60 kW

38 38 134 mm 6

kg./sq.cm.

34oC 30

oC 21.5

oC 24

oC Manipula

tor


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Hydrauliccellar

Heatexchanger

specification

No. ofplatesas percircuit

No. ofplatesfound

Platepackedlengthfound

Maximumworkingpressure

Oilinlet

temp.

Oiloutlettemp.

Waterinlet

temp.

Wateroutlettemp.

Purposeserved

to

H5 Type- P2-FH

Serial No.-

30101-32-976Capacity-

120 kW

85 105 380 mm 10

kg./sq.cm.

42oC 37

oC 22.5

oC 25.5

oC Coiling

box

H6 Type- P2-FH

Serial No.-

30101-61-582

Capacity-

140 kW

31 85 302 mm 6

kg./sq.cm.

31oC 29

oC 20.5

oC 24

oC Finishing

mill

H7 Type- P2-FH

Serial No.-

30101-32-976

Capacity-

60 kW

38 97 326 mm 6

kg./sq.cm.

35.5oC 33

oC 22.5

oC 25.5

oC Finishing

mill

H8 Type- P2-FHSerial No.-

30101-73-723

Capacity-

140 kW

125 163 575 mm 10kg./sq.cm.

40.5o

C 36.5o

C 22o

C 25o

C Finishingmill


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Hydrauliccellar

Heatexchanger

specification

No. ofplatesas percircuit

No. ofplatesfound

Platepackedlengthfound

Maximumworkingpressure

Oilinlet

temp.

Oiloutlettemp.

Waterinlet

temp.

Wateroutlettemp.

Purposeserved

to

H9 Type- P2-FH

Serial No.-

30101-73-722Capacity-

140 kW

125 125 455 mm 10

kg./sq.cm.

34oC 31.5

oC 20

oC 24

oC Down

coiler 1

H9A Type- P2-FH

Serial No.-

30101-73-721

Capacity-

140 kW

125 125 438 mm 10

kg./sq.cm.

34oC 31.5

oC 20

oC 24

oC Down

coiler 2

H10 Type- P2-FH

Serial No.-

30106-74-501

Capacity-

120 kW

85 153 556 mm 10

kg./sq.cm.

43.5oC 40.5

oC 22.5

oC 29

oC Coil

conveyor

-1

H11 Type- P2-FH

Serial No.-

30101-61-583

Capacity-

200 kW

_ 133 465 mm 6

kg./sq.cm.

42oC 37

oC 25.5

oC 27.5

oC Coil

conveyor

-2 to 6


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In the study of heat exchangers in different hydraulic circuits we came to know what

type of heat exchangers are generally useful in an industry, how different types of heat

exchangers work, where the heat exchanger should be placed, at what pressure a heat

exchanger generally work, what kind of problems can arise in a heat exchanger etc. Andespecially why we need a heat exchanger in a hydraulic system. In the industry we have

also learnt how an industry is really operating. There we came to know how hydrauliccylinders operate, why and where filtration is needed in a hydraulic system, function of

direction control valve etc. and all these are beyond of our bookish knowledge. Our

theoretical knowledge would be incomplete without watching an industry running andhow theoretical knowledge is incorporated in the real world just like making strips in

HSM dept. by rolling the slabs and this process does not only include manufacturing

knowledge of ours, it also includes the other topics of mechanical engineering like

hydraulics, lubrication, material science and other branches of engineering also likeelectrical and others. These all are possible due to the help from our guide Mr. Braj

Kishor Kumarand alsoMr. M.B. Victor Joseph. Whenever we needed a help we got them.And we should not deny the co-operation of the workers of HSM Dept. of TATA STEELLtd. And above all there was a hand of authority was always there with us. Lastly we

want to thank them all for their co-operation in gathering knowledge about heat

exchanger and without their help our project would be incomplete.

********** THE END **********

study of heat exchangers in different hydraulic circuits in hsm

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