ME 315 King Fahd University Introduction to Heat Exchangers Thesis Paper

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ME 315

King Fahd University of Petroleum and Minerals

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 Abstract (300 – 500 words)

 Chapter1: Introduction to heat exchangers (1-3 pages)

 Chapter2: Heat exchangers in combined-cycle power plants (1-5 pages)

 Chapter3: Description of combined-cycle power plant (1-5 pages)

o Components e.g. pumps, boiler, low & high pressure turbines, compressors, condenser, reheater, feedwater heater, etc.

o Thermodynamic states/properties e.g. temperature, pressure, etc.

o Other details e.g. flowrates, fuel type, efficiencies, etc.

 Chapter4: Description of the heat exchanger(s) used in the CCPP.

o Design, material, measurements, effectiveness, fouling, etc.

 Chapter5: Simulation of heat exchanger operation for the following conditions:

o Heat exchanger operation from Time=0 to steady-state condition.

o Heat exchanger operation at steady state condition.

o Heat exchanger operation from steady-state to complete shutdown mode.

 Conclusions and recommendations

 References




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ABSTRACT
This paper covers the design and modeling of a Heat Exchanger in a Combined Cycle Power Plant
(CCPP). This sort of power plant has gotten increasingly used because of its high proficiency and
low outflows. The Heat Exchanger assumes a focal function in the steam age utilizing the gas
turbine
's fumes heat.

There is a hypothetical clarification of the CCPP segments and control framework remembered
for this proposition's extent. The advancement technique is depicted, and the top-down
methodology that was utilized is clarified. The structure and conditions used are accounted for
every one of the created models, and a realistic portrayal is given. To guarantee that the Heat
Exchanger model would work in a total CCPP model, transformations were made, and tuning was
performed on the current encompassing segment models in the CCPP. Static checks of the models
are performed.
Joined cycle (CC) power plants permit to fulfill the developing energy need with the least fuel
utilization. Subsequently, it is of extraordinary premium to characterize a technique for advancing
these frameworks, to get more special exhibitions and proficiency.
The reason for the most piece of the world associated with this area is to arrive at generally warm
effectiveness of 45% in the short period, most notably by improving the gas turbine bay
temperature.
To create power with higher overall efficiency, general productivity, and sensible expense, focus
on power industries' power terrible situation. Even though a combined cycle power plant is the
most efficient approach to deliver power in this day and age, quickly expanding fuel costs rouses
to characterize a methodology for savvy improvement of this framework.

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CHAPTER ONE
INTRODUCTION TO HEAT EXCHANGERS

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Heat exchangers are devices used to transfer or 'exchange' thermal energy between two fluids
(Forsberg, 2020). The fluids can be single or two-stage and, contingent upon the exchanger type
might be isolated or indirect contact. Gadgets, including fuel sources, for example, atomic fuel
sticks or fired heaters, are not ordinarily viewed as heat exchangers, albeit a large number of the
standards associated with their plan are the equivalent (Brogan, 2011). The unique kind of heat
exchanger is a vehicle radiator. In a radiator, a water and ethylene glycol solution moves heat from
the motor to the radiator and afterward from the radiator to the encompassing air moving through
it. This cycle assists with shielding a's motor from overheating. Likewise, Aavid's warmth
exchangers are intended to eliminate overabundance of heat from airplane motors, optics, x-beam
tubes, lasers, power supplies, military hardware, and numerous gear types that require cooling past
what air-cooled heat sinks can give (Boyd Corporation, n.d.).

As the fluids move through an exchanger, one fluid increases heat, and the other loses heat. If the
cycle does exclude dissipation or buildup, the two liquids will encounter a temperature
adjustment—one liquid expanding in temperature and the further diminishing in temperature. Heat
exchangers have a bunch of uses (Forsberg, 2020). They fill in power plants as steam condensers,
feedwater radiators, steam generators, and preheaters. Heat exchangers see broad use in compound
cycle applications. Likewise, they are widely utilized in the HVAC business, where they are
boilers, condensers, evaporators, warmers, forced air systems, radiators, and heating/cooling
loops.

Contingent upon the sort of Heat exchanger utilized, the heat transferring cycle can be gas-to-gas,
fluid-to-gas, or fluid-to-fluid and happen through a solid separator forestalls blending of the liquids

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or direct liquid contact. Discovering application across a broad scope of ventures, a different
determination of these heat trading devices are planned and produced for use in both heat and
cooling measures.

To examine heat exchangers, it is essential to give some classification. Two methodologies are
regularly taken. The main considers the flow configuration inside the heat exchanger, while the
second depends on the order of hardware type principally by construction(Ronquillo, 2017). Other
plan attributes, including construction materials and construction, and heat transfer mechanisms,
likewise help arrange and sort the kinds of heat exchangers available. All are considered here
(Brogan, 2011).
Classification of Heat Exchangers by Flow Configuration
There are four basic flow configurations(Brogan, 2011):
1. Counter Flow
2. Concurrent Flow
3. Crossflow
4. Hybrids such as Cross Counterflow and Multi-Pass Flow
In a counterflow exchanger, the two fluids flow corresponding to each other in inverse ways. This
kind of flow arrangement permits the most significant change in the two liquids' temperature and
is thus generally useful. This is illustrated in Figure 1

Figure 1. Countercurrent flow.
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Figure 2 illustrates a concurrent flow heat exchanger, the heat flow parallel to each other and in
the same direction. This is less efficient than countercurrent flow but does provide more uniform
wall temperatures.

Figure 2. Concurrent flow.
Figure 3 illustrated a Crossflow heat exchanger, which is more similar to a transitional in
efficiency between countercurrent flow and parallel flow exchangers. In these units, the streams
stream at the right points to one another.

Figure 3. Crossflow.

In industrial heat exchangers, hybrids of the above flow types are common. These are combined
crossflow/counterflow heat exchangers and multi-pass flow heat exchangers, and pass flow heat
exchangers, as shown in Figure 4.

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Figure 4. Cross/counter flow.

Classification of Heat Exchangers by Construction
In this part, heat exchangers are characterized basically by their construction, Garland (1990), as
shown in Figure 5. The primary degree of characterization is to partition heat exchanger types into
recuperative or regenerative. A Recuperative Heat Exchanger has separate flow paths for every
fluid, and fluids flow at the same time through the exchanger trading heat across the wall divider
isolating the flow ways. A Regenerative Heat Exchanger has a flow path, which the hot and cold
liquids alternately go through.

Figure 5. Heat exchanger classifications.

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Regenerative heat exchangers
In a regenerative heat exchanger,, the flow path typically comprises a matrix, which is heated
when the hot liquid goes through it. This heat is then delivered to the cold fluid when this courses
through the matrix. Regenerative Heat Exchangers are otherwise known as Capacitive Heat
Exchangers. A decent outline of regenerators is given by Walker (1982).
Regenerators are predominantly utilized in gas/gas heat recovery applications in power stations
and other energy serious ventures. The two principal kinds of regenerator are Static and Dynamic.
The two sorts of regenerator are transient in activity and except if extraordinary consideration is
taken in their construction there is regular cross defilement of the hot and cold streams.
Notwithstanding, the utilization of regenerators is probably going to increase later on as endeavors
are made to improve energy efficiency and recover more low grade heat. In any case, on the
grounds that regenerative heat exchangers will in general be utilized for expert applications,
recuperative heat exchangers are more common.

Recuperative heat exchangers
There are numerous sorts of recuperative exchangers, which can comprehensively be assembled
into indirect contact, direct contact and specials. Indirect contact heat exchangers keep the fluids
trading heat separate by the utilization of tubes or plates and so forth Direct contact exchangers
don't separate the fluids trading heat and indeed depend on the fluids being in close contact.

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CHAPTER TWO
HEAT EXCHANGERS IN COMBINED-CYCLE POWER PLANTS
To build the general efficiency of electric power plants, different cycles can be consolidated to
recuperate and use the leftover heat energy in hot fumes gases. In joined cycle mode, power plants
can accomplish electrical efficiencies up to 60 percent (WARTSILA, n.d.). The expression
"combined cycle" alludes to the joining of various thermodynamic cycles to create power.
combined cycle activity utilizes a heat recovery steam generator (HRSG) that catches heat from
high temperature exhaust gases to deliver steam, which is then provided to a steam turbine to create

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extra electric force. The cycle for making steam to deliver work utilizing a steam turbine depends
on the Rankine cycle.
The most widely recognized kind of combined cycle power plant uses gas turbines and is known
as a joined combined gas turbine (CCGT) plant. Since gas turbines have low efficiency in basic
cycle activity, the yield created by the steam turbine represents about a portion of the CCGT plant
yield. There are a wide range of designs for CCGT power plants, however commonly each GT has
its own related HRSG, and various HRSGs supply steam to at least one steam turbine.
The HRSG is fundamentally a heat exchanger, or rather a progression of heat exchangers. It is
likewise called an evaporator, as it makes steam for the steam turbine by passing the hot fumes gas
stream from a gas turbine or burning motor through banks of heat exchanger tubes. The HRSG
can depend on a normal course or use constrained dissemination utilizing siphons. As the hot fumes
gases stream past the warmth exchanger tubes in which hot water courses, heat is consumed
causing the making of steam in the cylinders. The cylinders are masterminded in areas, or modules,
each serving an alternate capacity in the creation of dry superheated steam. These modules are
alluded to as economizers, evaporators, superheaters/reheaters, and preheaters.
The economizer is a heat exchanger that preheats the water to move toward the immersion
temperature (limit), provided to a thick-walled steam drum. The drum is found nearby finned
evaporator tubes that course warmed water. As the hot fumes gases stream past the evaporator
tubes, heat is retained, causing steam formation in the cylinders. The steam-water combination in
the cylinders enters the steam drum where steam is isolated from the high temp water utilizing
dampness separators and typhoons. The isolated water is recycled to the evaporator tubes. Steam
drums additionally serve stockpiling and water treatment capacities. An elective plan to steam
drums is a once-through HRSG, which replaces the steam drum with meager walled parts that are

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more qualified to deal with changes in fumes, gas temperatures, and steam pressures during regular
beginnings and stops. In particular plans, channel burners are utilized to add warmth to the fumes
gas stream and lift steam creation; they can deliver steam regardless of whether there is a deficient
fume gas stream.
Immersed steam from the steam drums or once-through framework is shipped off the super radiator
to deliver the steam turbine's dry steam. Preheaters are situated at the most relaxed finish of the
HRSG gas way and assimilate energy to preheat heat exchanger fluids, for example, water/glycol
combinations, in this way removing the most financially reasonable measure of warmth from
fumes gases.
The superheated steam delivered by the HRSG is provided to the steam turbine, where it extends
through the turbine edges, bestowing pivot to the turbine shaft. The energy conveyed to the
generator drive shaft is changed over into power. After leaving the steam turbine, the steam is
shipped off a condenser, which courses the consolidated water back to the HRSG.

CHAPTER THREE
DESCRIPTION OF COMBINED-CYCLE POWER PLAN

As of late, the consistently developing interest for electric power has incredibly expanded the
interest in combined cycle power plants. This is primarily a direct result of their high efficiency,
and generally, low venture costs comparative with different advancements (Flynn., 2003).

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In this part, an overall foundation, including the hypothetical information pertinent for
comprehension of the created CCPP dynamic model, is introduced.
3.1 General Description of Thermodynamic Cycles
A thermodynamic cycle contains a series of thermodynamic processes moving warmth and work
while carrying the weight, the temperature, and other state factors. These game plans of cycles, in
the end, return the system to its entire state and structure a cycle (Yunus and Boles, 2002).
Particular thermodynamic processes are used to portray respected variations of the cycles that
occur in, for instance, power plants. An average plan for a CCPP relies upon joining the Brayton
Cycle and the Rankine Cycle to efficiently grow plants' plants. The blend of these two cycles
depicts the essential handiness of the CCPP.
3.1.1 The Ideal Brayton Cycle
The Brayton Cycle is utilized to portray the activity of the gas turbine motor. In Figure 1, the cycle
is clarified. The schematics to one side speak to the parts that play out the energy transformations
in the cycle. The graph in the center shows the connection between the weight, P, and explicit
volume, v, in the cycle. The chart to the correct show's relationship between the
temperature, T, and the particular entropy, s

Figure 6: The Brayton Cycle explained by schematics, a P-v diagram, and a T-s diagram
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The numbers 1-4 in Figure 6 each speak to an alternate thermodynamic state that the system is in.
A thermodynamic state depicts the fleeting condition of a thermodynamic framework.
The efficiency of the ideal Brayton Cycle, here meant Bη, is determined utilizing the simultaneous
equation:

Want is the net power output, QH is the net heat input, and is the ambient temperature, T1, implies
the temperature of the gas turbine's environmental factors. T2 additionally represents the
temperature when the thermodynamic system is in state 1. T2 signifies the weather after the
compression has occurred (http://web.mit.edu, 2011).
3.1.2 The Ideal Rankine Cycle
The ideal Rankine Cycle is a cycle for a hypothetically enhanced steam plant concerning
productivity if it would work under ideal conditions. This cycle can demonstrate the general
functions of the water/steam cycle in the CCPP. In Figure 7 and Figure 8, this cycle is clarified.
The plan speaks to the parts that play out the Rankine Cycle's energy changes, the evaporator, the
steam turbine, the condenser, and the siphon.

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Figure 7: The components in an ideal Rankine Cycle

Figure 8: A T-s diagram of the ideal Rankine cycle

The numbers in Figure 7 and Figure 8 identify the different thermodynamic states
that together complete the cycle. When the system moves from one state to another, it is called a
thermodynamic process. The processes in the Rankine Cycle is as follows:

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Cycle 1-2: liquid is siphoned from low to high pressure.
Cycle 2-3: The high-pressure fluid enters a boiler where it is warmed at steady pressure by
an outside heat source, so it gets dry immersed steam.
Cycle 3-4: The dry saturated steam grows through a steam turbine, and mechanical work is
created.
Cycle 4-1: The steam at that point enters a condenser where it is condensed.
When contemplating a thermodynamic framework, the enthalpy is a significant property. Enthalpy
is a thermodynamic capacity of a system, identical to the amount of the system's inside energy and
the result of its volume duplicated by the pressure applied on it by its environmental factors. The
explicit enthalpy indicated is characterized as:
h=u+pv
The specific internal energy, v is the specific volume, and p is the pressure. The specific enthalpy
has the SI unit joules per kilogram. The efficiency of the ideal Rankine Cycle, here denoted ηR,
can be described for example by using the following formula:

In the numerator, the network yield is determined, and in the denominator, the heat provided to
the heater is spoken to. Here hi indicates the particular enthalpies at the state I where i=1...4. So if
the enthalpies at the conditions of the framework are known, the system's efficiency can be
determined without much of a stretch (Storck et al., n.d.).

3.2 The Combined Cycle Power Plant

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Because of their high general plant proficiency and low outflows, contrasted with, for instance,
ordinary single-cycle power plants, Combined Cycle Power Plants (CCPP) have picked up
ubiquity lately. The low discharge is an outcome of the utilization of low carbon content fills. e.g.,
flammable gas, which decreases the ozone harming substances creation (Marie-Noëlle, 2004). A
regular CCPP utilizes the fumes gases from a gas turbine to create steam in an HRSG for additional
steam turbine usage. A Combined Cycle is, as the name recommends, a blend of two distinctive
thermodynamic cycles, generally the Brayton Cycle and the Rankine Cycle, that were portrayed
above. The joined process frames the theoretical base for the capacity of the CCPP, yet relying
upon the application, the arrangement and segments utilized shifts (Boyce., 2001).
A mix of cycles with various working media is fascinating because their focal points can
supplement one another. Combined Cycle activity gives preferences for both the high-and the lowtemperature parts of the ignition cycle. The Brayton Cycle has excellent execution working in the
high-temperature district, and the Rankine Cycle has perfect performance working in the lowtemperature area (Flynn., 2003). When two cycles are consolidated, the higher temperature cycle
is known as the fixing cycle. The process of working at a lower temperature level is known as the
lining cycle. Figure 9 shows an improved stream chart for a typical joined cycle arrangement
(Hannemann et al., 2009).

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Figure 8 Conceptual diagram of a CCPP
3.3 COMPONENTS OF CCPP
3.3.1 The Drum Boiler
Boilers can be of various shapes, sizes, and types. One of the most well-known sorts of evaporators
utilized for the steam age in warm force plants is the drum evaporator. This kettle uses an enormous
drum for steam and water (Bell and Åström; 2000, #). There are two kinds of drum boilers, one
that utilizes characteristic dissemination in the downcomer-riser circle and one where water is
coursed using a siphon. The siphons are arranged at the lower part of the risers. Drum boilers that
utilize the prior arrangement are called constrained flow drum boilers.
The drum heater has a significant influence on the CCPP since it is the steam delivering unit, and
its dynamic conduct positively affects the reaction of the framework. The course of the water steam
combination is significant. It builds the bubbling cycle's efficiency and keeps all pieces of the
evaporator at an almost uniform temperature. That expands the solidness of the drum evaporator.
During pressure changes, the energy is put away in the steam, and the water is delivered or
consumed rapidly. This is additionally a critical property to make the temperature uniform in the

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whole unit, regardless of whether drum boilers frequently have enormous actual measurements
(Bell and Åström, 2000, #).
Keeping the drum evaporator controlled and operational is vital to plant activity and security.
Keeping away from the drum's flood, implying that feed water enters the superheater, is significant.
So is staying away from dry out that occurs if the drum is dependent upon unnecessary warming.
Over-warming the riser lines could likewise prompt material harm and line spills. Staying away
from circumstances when an excess of weight develops inside the drum is also significant
(Ganapathy., 2001, #). Every one of these dangers related to drum kettle activity should be
evaluated by the proper use of the control situation.

3.3.2 The Superheater
Likewise, the superheater is a warmth exchanger, yet it has an unexpected impact compared to the
economizer in the HRSG framework. This part is utilized to warm up the steam leaving the drum
evaporator using the most noteworthy temperature fumes gas from the gas turbine. The superheater
can comprise a few stages where each progression is a different warmth exchanger.
The superheater's motivation in the CCPP is to raise the steam temperature from immersion
conditions to make it superheated. Superheated steam diminishes the steam turbine's steam heat
pace, improving the turbine and generally plant power yield and proficiency. Significantly, the
steam turbine is furnished with smoke with the correct properties, so it works under the conditions
it was intended for. The reason for utilizing the superheater along with its regulator, portrayed in
Section 3.4.6.3, is to guarantee these appropriate activity conditions. On the off chance that this
falls flat and beads would frame that, at that point enters the steam turbine, it can harshly harm the
turbine edges (Ganapathy., 2001, #).

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The superheater can create superheated steam by engrossing the warmth by the superheater's metal
containers and, subsequently, by the steam inside the superheater. The steam stream's properties
from the drum and fumes gas, leaving the gas turbine to impact the steam elements in the
superheater (Ganapathy., 2001, #).
3.3.3 Supplementary Firing
Valuable terminating burners can be introduced to expand the intensity of the CCPP. Strengthening
terminating likewise diminishes the particular plant venture cost. The strengthening terminating
raises the temperature of the fumes gas. There are various alternatives when choosing the burners'
situation, yet one arrangement is to put them between two of the superheater steps. A gas turbine
has a few focal points as a force source. It tends to be effortlessly gathered and raised, and it can
have effectiveness going from 25% to 40%. They likewise require less cooling water than other
leading players (Ganapathy., 1996, #). They arrive in a wide assortment of sizes and force yields
and have a few applications. The gas turbine's primary segments are the blower, the burning
chamber, and the real turbine coupled to a generator.
The blower drives air into an ignition chamber. In the ignition chamber, the combination of air and
fuel is lighted. The combusted hot blend makes the turbine work, and it changes the
energy from the hot gas into dynamic energy. The motor energy is then used to drive the blower
and the generator for the creation of power. An approach to depicting this cycle is by utilizing the
Brayton Cycle that was portrayed before. The fumes gas temperature is high, which assists with
producing high-weight and high-temperature superheated steam in the HRSG (Ganapathy., 1996,
#)
3.3.4 The Condenser

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A condenser is a gadget utilized in steam turbines to condensate the steam that leaves the steam
turbine. However, the condenser is also a sort of warmth exchanger with an unexpected reason
compared to in the economizer or the superheater. A typical kind of mechanical application is the
shell and cylinder heat exchanger. The warmth is taken out from the steam by utilizing a cooling
medium, usually air or water. Surface condensers use the shell and cylinder heat exchangers. They
comprise a large vessel containing countless cylinders, some finned tubes, to enlarge the heat move
region.
An air-cooled condenser is picked when cooling water is shy of supply, yet it is a more costly
arrangement than the water-cooled condenser (Boyce., 2001, #). One method of expanding the
general effectiveness of a CCPP is to keep a low weight in the condenser. The mass stream rate
frequently should be extensively higher on the cooling side to make the steam condensate. The
consolidated steam is then siphoned through to the feed water tank utilizing a condensate siphon.

CHAPTER FOUR
DESCRIPTION OF THE HEAT EXCHANGER(S) USED IN THE CCPP
4.0 Design Analysis of Heat Exchanger
Although many types of heat exchangers exist, shell and tube heat exchangers were selected for
this design. Shell and tube heat exchangers are the most versatile type of heat exchangers. In
process industries, they are used in conventional and nuclear power stations as condensers, steam

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generators in pressurized water reactor power plants, feedwater heaters, and some air conditioning
and refrigeration systems. They are also proposed for many alternative energy applications,
including ocean, thermal, and geothermal. Shell and tube heat exchangers provide relatively large
heat transfer ratios to volume and weight, and they can be easily cleaned.
Shell and tube heat exchangers offer great flexibility to meet almost any service requirement. The
reliable design methods and shop facilities are available for their successful design and
construction. Shell and tube heat exchangers can be designed for high pressures relative to the
environment and high-pressure differences between the fluid streams. Shell and tube heat
exchangers are built of round tubes mounted in a cylindrical shell parallel to the shell. One fluid
flows inside the pipes, while the other fluid flows across and along the exchanger's axis. This
exchanger's significant components are tubes (tube bundle), shell, front-end head, baffles, and tube
sheets.
Shell types-various front and rear head types and shell types have been standardized by the Tubular
Exchanger Manufacturers Association (TEMA). The E-shell is the most common due to its
cheapness and simplicity. In this shell, the shell fluid enters at one end of the body and leaves at
the other end; that is, there is one pass on the shell side. The tubes may have single or multiple
passes and are supported by transverse baffles. This shell is the most common for single-phase
shell fluid applications. With single-tube access, a nominal counter flow can be obtained. The
design of a body and tube heat exchanger is an iterative process because heat transfer coefficients
and pressure drop depend on many geometric factors, including shell and tube diameters, tube
length, tube layout, baffle type, and spacing and the numbers of tube and shell passes, all of which
are initially unknown and are determined as part of the design process.

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In any power plant, heat exchangers are essential equipment. The heat exchanger is used to
increase or decrease the mixture to the desired temperature. The heat exchanger that was used here
is the shell and tube exchanger. Shell and tube heat exchangers are the most common type of heat
exchanger used in the industry. This is because it has many advantages. The advantages are: 1. It provided a large transfer area in a small space.
2. Good mechanical layout: a good shape for pressure operation.
3. We used well-established fabrication techniques.
4. It can be constructed from a wide range of materials.
5. It can be cleaned easily.
6. Well-established design procedures.
7. Single phases, condensation or boiling, can be accommodated in either the tubes or the
shell, in vertical or horizontal positions.
8. Pressure range and pressure drop are virtually unlimited and can be adjusted independently
for the two fluids.
9. Thermal stresses can be accommodated inexpensively.
10. A great variety of construction materials can be used and may be different for the shell and
tubes.
Design of the Heat exchanger
Power plants use heat exchangers to collect heat from hot waste gases to get power. The hot fluid
is steam available at 200oC, which is condensed into liquid water. The cooling fluid is cold water,
available at room temperature with a maximum temperature rise of 50K.

The chemical

engineering design for the heat exchanger is also known as thermal. The design requires the
calculation of the heat transfer area required. From this value, the unit's design features such as the
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tube and shell size, tube counts, and layout are determined. The pressure loss of the fluids across
the unit is also ca...


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