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So now, we will start up with a new chapter, the System Simulation. So, now on it will
get, it will get mathematical, everything will get mathematical. So, we will be solving
lots of problems in the class, as I told you before, please come to the class with your
calculators. Now, first half an hour, we will just go through some basics; and I will teach
you about information flow diagrams, which will be helpful to you, in solving of System
Simulation problems. Even without that, you can solve, but things will be more organized,
particularly if a system is made of several components, it is always a good idea to represent
each of this as blocks and find out, what is the information which is going into the
system, what is the information which is coming out.
So that, you get an overall idea, but I have seen,I have been teaching this for 10 years
IIT students, do not like to draw all this and so, straight away you want to solve that
is ok. There are only2 or 3 components are involved, but if you have large system, which
consists of several components, it is always a good idea to do to do, what is called an
information flow diagram, which I will discuss in today’s class. So, the mathematics will
start from the next class onwards. So, I will teach you the method of successive substitution
and Newton Rapson method for single unknown as well as multiple unknowns.
So,what is system simulation, system simulation is basically a is basically a mimicry or you
mimic the system, you mimic a system it can be defined as a calculation of operating variables
such as pressure, temperature and flow rates of energy in a thermal or energy system operating
in a steady state,I am sorry this it can also include system operating in the steady state
and also operating in the transcendent condition.For example, a power plant, most of the times
we are interested in the steady state performance of the power plant.
But, there are also issues like starting up and shutting down of a power plant, these
are the very critical for the nuclear reactor. Suddenly, there is an accident and there is
an emergency shutdown, you can shutdown all the things, you will shut down your reactor,
but this nuclear fission is not going to stop immediately, it will continue to the fission
reaction will continue to proceed and if all the all the systems breakdown, you would not
have pumps which will take the heat from the fission, fission reaction.
And therefore, you will not be able to dissipate all the heat ultimately to the ambient. So,
in this case natural convection will take over, because pump is not working.So, you
should design a nuclear system such that in the case of an accident in the case of an
accident even under natural convection even under natural convection, you do not have
catastrophic consequences. So, these are the essential part of is an
essential safety divisions are very very important in nuclear nuclear power plants, lots of engineers
working on safety, there is a separate body in India called the Atomic Energy Regulatory
Board (AERB) which is actually separate from the which is actually separate from the atomic
energy, I mean atomic power plants. So, this is the regulatory body which comes and checks
periodicperiodic intervals of time, whether the safe safety systems are in place.
So, as thermal engineers or mechanical engineers while most of the time we are interested in
the steady state. We are also some times interested in transient; the mechanical engineer on the
other hand is often times interested often times interested in the transient operation.
So, processes control, process control is big time, process control is a big deal in
chemical engineering, process control is not a big dealing,your you just learning one course
in controls, instrumentation and controls. How much of control did you study in that
course? It is mostly on instrumentation.
So, control will also involve in stability analysis and all that. So, suppose you give
a disturbance to a system whether it non-linearly grows or decays with time. So, this essentially,
what is called as a stability analysis and so on, so chemical engineers are often interested
in this, but mechanical engineers somehow, we do not concentrate much of course, needless
to say in this course, we will concentrate only on steady state, but I want you to remember
that transient are also important. The definition which I given above basically,
we want to calculate. So, just like in the previous example, you actually calculate the
actually figured out the diameter the diameter of the pipe as well as the ratings for the
pump, we should be able to calculate all the operating variables. So, it could be possible
that you actually have a heat exchanger and you want to work out the outlet temperatures
of the fluids and so on. That is basically, I am talking about an analysis problem. So,
design problem is given in all this flow rates and all that what will be the heat exchanger
size, how many numbers of tubes and so on. So, I already explained to the difference
between the analysis problem and the design problem. So, simulation is more concern with
the design concern with the analysis rather than the design. So, this definition is basically
for a thermal system. So therefore, for us to do System Simulation, we need to know the
perform performance characteristics of all components and we need to know the equations
for the thermodynamic properties of the working substances, thermodynamic. So, we are not
going to work with air always, it is very beauty, it is very easy to work with air and
water that is why old thermodynamics there are onlytwo fluids, in your M.E 110, we taught
you onlytwo fluids. Now, its M.E110, air, p is equal to row r
d, and all that simply keep on doing this; no problem, other one you use the steam tables,
anything beyond that we are not taughtthermodynamics, but however, new fluids are constantly coming
up deficiencies or, because of monitorial protocol people are changing moving away from
CSCand so on. Who will give us the properties of all these?
So, there should be groups of scientists or engineers, we are constantly adduct, we are
using equipment,we are developing equipment to measure all these properties and give us
in the form of hand books, charts in the form of CDs or post it on internet or whatever.
Now, in order to do system simulation, it is not possible to use tables, I ask you to
do simulation, you take 100 bar 400 degree centigrade, when will you complete the work.
So, what you need, properties must be in the form of in the form of equations, you need
to have equations therefore, regression is required for this.
So, you need to be good in statistics, if the proper if if for example, the enthalpy
is given as a function of pressure and temperature, can you construct can you construct equations
of Y as a function of x 1 and x2, where x 1 is… Y is enthalpy, x 1 is pressure; x2
is temperature.So, Y as a function of (x 1, x2) enthalpy, entropy and all this, then change
of phase h f g; that is later heat, all these things you should be you should be comfortable
in converting all the whatever information you have put them in the form of mathematical
equations. Similarly, if I know, if I know the if I if
I know the operating variables of a compressor or a blower whatever, I should be able to
calculate the efficiency in terms of these operating variable therefore, a knowledge
of regression and knowledge of how to represent the properties or a system performance in
terms of equations is inherent, this information has got to be embedded, otherwise you will
not be able to do simulation. Therefore, after after do going through the
simulation for few classes, we will get back to regression. And I will teach you, if you
have got Y as a function of (x 1, x2) how do you get this equation. So, some two weekstwo
weeks some intensive crash course on regression, essentially with the view essentially with
the view to get equations for either the system properties or for getting the performance
characteristics of components is very much important, I will teach you certain things
which were not studied elsewhere, but for my M. Tech student there will be some overlap
with your measurements course there will be some reputations, but that is unavoidable
butit is very very important, it is imperative that you learn this.
Now, what is a storing? The equations for the performance characteristics
of the components and thermodynamic properties along with mass and energy balance will constitute
a set of simultaneous equations, which relate the operating variables. If you solve the
system of simultaneous equations, you will be able to fix all the operating parameters
of this system under question, this is basically System Simulation.
There will be a largethere will be a large number of variables. So, you will have to
do matrix operations for large system; however, for the classroom environment, we will restrict
our attention only to two and three variables problems.
So, system simulation is thus a way is thus a way of mimicking the performance of a real
system. Instead of trying to do an experiment,I am trying to find out, how the output will
change in each of these inputs changes, you write all this in terms of mathematical equations.
So, you have a computer model or a mathematical model of a simulation and you go ahead and
do numerical experiments or you do experiments on the computer and up front even before you
design, you get an idea, how the system is performance is changing, if the design, if
the operating variables are changed. So, that is the goal ofthat is the goal ofSystem Simulation.
So, this simulation is different from another kind of simulation where a system is simulated
by observing by observing the performance of another physical system. That is basically
called the “analog model” which you have learn, which you have studied heat transfer.
So, that is what System Simulation, I am not talking about that for example.
So, there is aslab, it is thickness x, thermal conductivity k having steady state. So, here
there is a heat transfer coefficient of h 1 and definition temperature of T infinity
1, here we have a heat transfer coefficient of h2, it is T infinity2. So, this situation
is typically encountered in heat exchange replication, where there is a plate which
separates the two fluids. So, there is a heat transfer from one fluid to another fluid let
us say that. So, this plate is baked this plate is baked
by hot fluid on one side and it is baked by cold fluid on the other side. So, this plate
access a mediator for the transfer of heat between from onefrom one fluid to another
fluid, but convection is encountered at the interface between this solid and fluid and
convection is also encountered at the interface between this solid and this.
And therefore, there is a flow of heat from left to right; this is the physical problem,
now it is possible for us, because h 1 and h2 are not equal to infinity. T infinity 1
will not be equal to T 1 and T2 will not be equal to T infinity, if h where to be infinity
if h 1 where to be infinity it requires an infinitely infinity smelly Small temperature
difference to accomplish the heat transfer from the fluid on to the solid; however, since
the maximum heat transfer coefficients even number boiling or condensations only 20000
watts per meter square or 15000 watts per meter square Kelvin, watts per meter square
Kelvin technically it is impossible to have a situation, where T 1 will be exactly equal
to T infinity 1.Therefore, whenever whenever there is convection there is always a resistance,
therefore, denote it as R convection. Now, because this fellow also does not have
an infinite thermal conductivity, it requires the temperature different heat transfer heat
will not be transfer unless there is a temperature difference. Technically, we will say in boiling
or condensations heat will flow with no temperature different, but that is only theory, then you
do not require heat exchanger at all;q is equal to h a, delta h a is infinity, you can
go home by having a heat exchange with 0 area. It is not possible, if if you have to make
the if you are you getting the point, if you were decrease the delta T, then the A will
increase the exponentially the cost will go up. So, you have a R conduction, again have
a R convection,we call it R convection inside, outside and so on; this is also a model of
the system, this is called the electrical analog model,it is aelectrical model; that
is, the flow of heat analog the flow of electricity,I am not talking… What you are tried to say
is, I am not talking about this; that you have we have talked about M.E 317 0 or whatever.
So, an example for this is the electricalanalogy for conduction, which is called “analog
model”.An example for what an example for what we have not talking.
Some uses of simulation, at the design stage simulation extremely useful achieving an improved
design, you can evaluate alternate design and find out which is better point number
one. Point number two it may be applied to an existing system to explore prospective
modifications. Existing system, you want to improve, you want to middle with the improve
then it is possible for you to use simulation. Simulation is usually needed for studying
performance, this is the very critical. Simulation is usually is usually needed for studying
performance at off - design conditions, why this is very critical is most of the times
most of the times, the system is working at off - design, there is a change in some variable
or the other. For example, it is working at part load or power plant.
During the evening time, afternoon and all that it will be heavy demand. Early morning
there would not be demand and so on. There will be a design load, but most of the time
there isoff - design load not consistently above or consistently below. Are you getting
the point? So, how does the system perform under off
– design condition is an important question, which can be answered, ifyou areif you are
able to develop a model and simulate the system.
Why are you so much interested in all this, because generally for a power plant,for example,
if you have to design a heat exchanger or if you designing air conditioning system for
an auditorium, air conditioning system for a mall, city center and other thing, where
lot of cost are involved. So, you are trying to simulate and then trying to not only simulate
and trying to optimize, because these cost are going up.
Now people are taking simulation optimization little more seriously, accompanied by this
is the fact that; you get powerfulcomputers as well as software programs, which can be
all these analysis very quickly, combine these analyses with an optimization technique and
try to arrive at an optimum; that is the story.
Most thermal systems operated off design conditions.So, simulation at the design stage itself will
be very useful to arrive at decisions if several alternatives are available for example, it
helps you to explore several alternatives. For existing systems, system simulation will
be useful to fix at, to fix an operational problem or to look at improvements.I already
discussed about this.
In summary, to cut a long story short simulation can be used to evaluate different designs.
Study behavior under off - design conditions. Study the sensitivity of the performance performance
of the system to various operating conditions. If x 1 to x n if x 1 to x nor you design variables
and y is the variable under question y is the system efficiency or the power output
of the plant d y by d x 1, d y by d x2 . Mathematics we call it, as Jacobean matrix,
if you are able to write in terms of matrix, if there are several Y’s d y 1 d y 1 by
d x 1 to d y n by d x 1, d y n d x 1 to d y n d x n that Jacobin matrix, if you are
able to evaluate all the components of that then, you can play around you get an overall
idea, how things work out for this complicated system.
Different classes of simulation, this is only story,do not worry; I am not going to ask,
I have already put this upon the net. Did you see it? I have already put it upon my
this thing, assignment two also I will put it up, I think all of you have copies, just
in case you want look at it, you can do that; different.
So, quickly we goes through this, these are all necessary evils, whenever you study something,
you should also learn the background theory, but doss is our would not. We will start working
for problems of the next class. Different classes of simulation, it can be dynamic or
steady - state; that is transient in steady - state. In transient, the change of operating
variables with reference to time, you are worried about the transient,basically required
for a control system, to avoid unstable operating conditions.
I already explained the background to you, steady state most often we are interested
only in the steady state; and it is usually applied to large systems.
The typical temperature versus the time, response for a steady state system, so a power plant,
even when you even when you start your motor car, when start your bike, you start an air
plane. So, there will be start up phase involved, the pilot just cannot… first you will close
the door, unless you closes the doors, you cannot start the engine. First, you have to
close close the doors and then you will start the engine one by one, you will start the
engine, right engine, left engine, then you will raise the throttle, full throttle you
will go, you will reduce the throttle, you will see whether the sounds everything are
ok. You will flop wings up and down all these
are mandatory just before takeoff something happen in between, but at least before at
least before taking off, he has to, he will check all,he will check all there will be
there will behuman number of this thing display, he will get the latest radar,radar this thing.
Now, they all have internet, all these modern planes have internet. He can look at all weather
maps, while in, while the plane is in motion off course, he has a very powerful radar,
where he can he can actually do this plus or minus 20 degrees he can go and then here
this radar has up to 120 kilometers he can see up to 120 kilometers he can see and then
up to here I thing here 60 degrees or 70 degrees left side,70 degrees right side. So, you can
you can do a lot of things, the only danger is sometimes micro burst. Suddenly,there is
an up draft and the down draft, which cannot deducted by radar that is called clean or,
then he is in trouble. So, otherwise he has to go through this, first
he will start the engine look at this thing and then once he gets on to the main runway,
he has to do it systematically, then he will havetwo or three levels and then at full throttle
at full throttle do the take off. After that the wheels have to go in again, if there are
going he is in trouble, because what happen the drag you know, increases enormously.
So, that is the beauty, look at the wheels so the hydraulically operated. You should
be able to deploy them whenever you wants, you should be able to retract them whenever
you wants. So, the transient all this thing there is a protocol. So, again approach that
when we lands again 20 minute before he has to and then there is a particular sequence
there is a particular sequence he has to follow, because the other planes are also flying and
there is a particular decent rate, because he is already flying at the MAC number 0.8
or 0.9. If it touches MAC number 1, then the m v square
by r then little bit enormously increase the gas turbine will cup; that is that is what
may be happen to a 4 to a 7, if you increases MAC number beyond 1 the engine will work,
but the plane may get blown up, because the stresses will be too much. So, transients
are very important. In the power plant we just start in the nuclear power plant.
So, there will be stage where you start with is the start - up then it reaches a steady
state and then there is a shut down. We will shut down for the maintenance or break down
whatever. Now, in this course mostly we are focusing on the steady state, if you want
transient then it cannot be done in a first level course, you would to learn it separately
or you take process control chemical engineering.
Simulation can be deterministic or stochastic.There are several cases are possible, where input
conditions are not known preciselyand the probability distribution may be given instead
with the dominant frequency, an average and an amplitudevariation.Then you cannot use
a deterministic simulation. So, then you have to do a stochastic simulation, suppose you
are… for example, you are going to do your MBA or going to do PhD management; for example,
they are these guys also do simulation, they do what is called a Monte carol simulation.
Let us say, there is a big the gastro department of the big corporate hospital. It is hiring
a consultant to do simulation, to find out the optimum deployment of it is OTs, OT is
Operation Theater.If you test three or four OTs,so it wants to optimally deploy; for example,
the bypass surgery and the kidney transplant may take long time, whereas the gall bladder
removal may take 2 or 3 hours only. So, it want to study then, what are the various steps
involved for example, a bypass surgery patient is first wielding ,then anesthetics moves
in, then they make measurements. Mostly surgeries engineering you know, mechanical
engineering mostly it is cutting and heavy engineering orthopedic is also too much engineering
actually, surgery is mostly engineering then they make measurements, they hopefully they
remember heart is in the left hand side then the junior doctor will make the measurement,
they will take x ray they will take x ray echo cardio, echo cardiogram report and then
they will identify, what is the size and all that and then he will make primary this thing
forwhere to cut and all that. And then the main surgeon will come and then
they will anaesthetize will monitor, how the this thing patient is responding then they
will start the surgery, then they will cut and then they put it on to the up heart lung
machine or now a days it is called what is it beating heart surgery? The heart keeps
beating heart keeps beating and they do the surgery, online surgery whatever and then.
So, it is the heart is not is stop, the heart is technically not stop stop and no artificial
heart lung machine, then he closes and then he is put in a recovery room to see whether
it is stabilize and then he taken to the ICUand so on.
Now, each of this for example, you can have a Gaussian distribution, the normal time taken
by anesthetist will be 30 minutes with a sigma of 5 or five or8 minutes. The, normal time
taken for a for a bypass operation, which fellow has a three blocks it is called TVD
- Triple Vessel Disease. So, triple will be 3 hours for the surgeon plus sigma of 18 minutes
then for the anesthetist to anesthesia to aware of all this.
Now, suppose we want to do a Monte carol simulation, you generate a random number random number
44 random number 44 means, You will say that if it is between 0 to 50 then the anesthetist
will do exactly at mean plus gamma, if it is between 50 to 70, he will take mean minus
gamma if it is the number between 70 to 90, you pre assign like that you come with the
model and using sequential random numbers you add up all these and find out, what is
the total number, total time which is taken. So, let us say the total time is218 minutes,
you can run this Monte carol simulation several time, if you take an average and then take
the variance and that will give you an idea of what is the overall Monte carol simulation
of a bypass surgery Apollo hospital that treatment information you can have, like that if you
do for everything Monte carol simulation, then what is the optimal - what is the total
time taken in a day, how many operations can you schedule and all this or the average time
corporate hotels are interested in the average time taken by a guest, when you enters the
hotel between the time enters the hotel, the time actually enters the hotel room, how much
time taken can we optimize on this, how much time taken for check out.
These are also related to QN theory and all the ORN. So, in all these cases it is not
known we cannot say that all surgeons will exactly finish it in2 and half an hour’s
they may have some unexpected thing, they will find something new. So, this it happen,
we may find somebody heartless that can that can be only in MRI scan whatever heartless
means, different, something different.So, these are Deter..So, this is basically not
Deterministic, this is Stochastic, because we do not know. The variables can be… the
variables can change with time. In a deterministic simulation, all the things are known priory
with certainty.
The condition may also be completely random with an equal probability that is what I explain
now in this so called example when for example, another example could be dealing with consumer
demands for power, stochastic descriptions is better than a deterministic descriptions.
So, I already gave you a Monte carol simulation, now you useful simulation method with the
only one course on Monte carol simulation method, we use it in heat transfer in all
group we use the Monte carol method to solve the inverse heat transfer problem.
The Monte carol method uses the randomness of the process along with the randomness of
the process along with the given probability distribution to simulate the system and to
get the average output and other characteristics. I explain in the last 5 minutes also how to
get the average time for the surgery and all that you can use the Monte carol method.
You can have a continuous and discrete simulation, most often times in thermal systems we have,
we are interested in the continual operations,continues operations of power plant AC systems IC engine
and so on.The flow of fluid assumed to be continuous; we do not encounter this discrete
kind of system, these discrete kind of systems are encountered in manufacturing, some there
is a batch mode and so on. So, whenever discrete pieces such as bearings, fasteners and gears
undergo a thermal process. Simulation focuses on a finite number of such items; simulation
of discrete discrete system is of particular relevance to manufacturing and involves consideration
of individual items as they go through a given process.
Information flow diagrams, the information flow diagram is a pictorial way of representing
the representing the performance.Representing the all the information which is required
for simulating the overall system by looking at the by looking at the information pertinent
to a particular component. Now, this is best,I want to close this represented by a block.
The information flow diagram is supposed to tell you, what are the inputs to this block,
what are the outputs from this block, what is a equation governing this component; that
is a, information flow diagram.
For a typical heat exchanger, can you take a guess on what are the inputs and what the
inputs or what the outputs or you already saw it there, but hopefully you did not read
it carefully, HX heat exchanger, two fluids are involved, now tell me mathematically flu
ride be more specific.The inputs to the… So, now we are looking at the information
flow diagram of a heat exchanger m dot hot then.
What will be the output T hot in T,I do not have to put T equal to out, because is already
fixed. How? T is already fixed by AC balance. So, the
information flow diagram is such in concise and precise, we do not say more than what
is required, what is the equation for equipment, you are saying this now, f of m hot,T hot
in, m cold, T cold in,T hot out equal to 0, this is the general, generic depiction or
description of the equation for the equipment. Can I get more specific for these equipments?
Since, you all studied heat transfer, what will be the f for this. What is the equation
that connecting all these variables? Energy balance alone will not help man. These
are designing heat transfer equipments. Hit the please, hit the right.
What is the equation? UALMTD.
UALMTD, this is one equation one from energy balance.
So
So f equal to… so you can write the equation as f equal to Q minus UALMTDF equal to 0.So,
actually do the System Simulation, the goal of your System Simulation is to make f 0 numerically
or as close as 0 to possible, you will stop iterations when f reaches 10 to the 10 to
the minus 3 or minus 4 or minus5. Are you getting this point?
Now, Compressor, please think for 2 minutes and tell me, incoming arrows, outgoing arrows,
theequation will write f of and leave it, compressor only one fluid is involved air
compressor,mass and correct good mass and pressure. So, m dot P 1, I need not put2 arrows
m dot, because the same arrow is coming out. Why unnecessarily waste more arrows? Are you
getting the point? What will come out? P2. That is it good the point. So, power equal
to m dot. Oh sorry sorry
Compressor in the last portion of the board is not visible to them m dot. Are you doing
steady state or unsteady?
So, f of… So, I can just say f of m dot, P 1, P 2 equal to 0.
What is that f of?
Correct. And make a mistake, it is fine, you have a doubt something is bothering you, Vinay
what isbothering, please ask me? P 2 fix.
You want to fix P 2, you want to know the, you want to fix P 2 why?
No, suppose I give different power what is the maximum P 2, I can get, suppose I am looking
at something like that. So, and efficiency is also there. No this is basically one component
system there is no funning this, all these you have studied either in thermo machineryand
thermodynamics and all these. Please, draw the information flow diagram
for a vapor compression refrigeration system. Question, please draw the information flow
diagram for a vapor compression refrigeration system. So, we will close with this example,
pleasethe question is, draw an information flow diagram for a vapor compression refrigeration
system. So, the first part of the story is representing the vapor compression refrigeration
system on previous diagram. Identify the various processes and the components associated with
each of these processes, represent each of these components in a box and find out what
is the link between the box; that is what is coming in and what is going out.
The output of one component will become the input of some other component and this is
called a Sequential Simulation, because everything is going in one cycle. Are you getting the
point? Turbine compressor is evaporator and so, it forms a... So, this is called a Sequential,
is called a Sequential Arrangement. Please go ahead, I will give you 5 minutes, please
draw the TS diagram, you do not have to very too much of the about the equation, you just
put f 1, f2, f 3, f 4.
What is this called?SUPER HEAT HORN
So, I will quickly explain the cycle, I told you modeling in the syllabus when I gave you
the course content I said modeling. So, to the extent required for this course, I will
teach you modeling in between. So, I already told you little about pump compressor and
so on. So, I will explain, I will give you 3 minutes course on Vapor Compression refrigeration
System. So, you start from point 1, point 1 is the fully saturated vapor 100 percent
vapor no liquid. So, let us assume compression it is pressure
and temperature increased. It is temperature is such that the temperature is the temperature
is raised to a level at which it is possible for you to condense that is, it is at a temperature
greater than the surrounding. Now, there is a super heating which takes place, then it
become fully saturated then it becomes fully saturated vapor, then it is condense please
remember the2 ,2 dash,3 are taking place at the same pressure. Now it becomes an it becomes
a fully saturated liquid refrigerant then it is throttled throttled is an… So, 1-2,
2-2 dash dc super heating,
4-1 is evaporation. So, it is an isenthalpic process the basic
job of this throttling is to ensure that the pressure is decreased, when the pressure decreases
automatically the temperature also decreases here, the temperature decreases now it is
a mixture of liquid and vapor which is at 4. Since, throttling is an irreversible process,
you cannot take it from 4 to 3,4 to 3 is so difficult, because it is it is impossible
to design a pump which is accomplish the objective, because it is impossible to do in a rank an
cycle in all the way here and then do this, you remember the rank an cycle. So, 4 now
you got a cold refrigerant, it first enters the, it enters the inin the for example, if
it is, this can be use for both refrigeration, air condition.
If it is a refrigerator, first it will enter the deep freezer, it will enter the deep freezer
then it will go to the chiller and milk chilling and places and all that. Then it will come
to the place where you keep vegetable and fruits and all that, it picks up the heat
it collects the heats from the food stuff, takes all the heat and vaporizes and comes
to state 1 and cycle is repeated. So, the whole thing we have an anti clock wise operation,
whenever there is an anti clock wise operation there is an it is a net work absorbing cycle,
it is a reverse heat engine.
And its performance is can be stated in terms of the coefficient of performance, the coefficient
of performance is refrigerating effect.
So for 1 kg, Can you tell me? In terms of enthalpy
h1 minus h4 by h2 minus h1. In variably the COP is greater than 1. So, the COPcarnot will
be
Correct. Will be COP, the heat engine operating between,so let us say this is, I do not know,
you have to call it as T i and T H and T L, 1 minus... Now, we have to draw the information
flow diagram for this is this clear, if it reverse the arrows, we reverse the direction
of arrows you get a you get arank and cycle power plant.Correct.
So, the rank and cycle power plant will be like this. So, if you do this if you do thisitit
will be extremely wet, it will be an extremely wet mixture at the end of the at the end of
the expansion more than if it is less than 88 percent, it will cost it will costof the
blades therefore, we super heated and bring it. Now, it is possible for you it is also
possible for you, also possible for you to do this. So, this is basically re heat. So,
you can reheat. So, you can have reheat you can have reheat regenerative cycle and so
on. These are all complicated versions of the more comply,more complex version of the
rank and cycle power plant.
So, basically the idea is you have got to do this, because nobody invented a pump to
do this and some people may be having an idea, why can we do like this, what will be the
pressure here, then if this produces x, this will 1.x. So, sometime you have like this,
what is this? Super Critical Cycle
So, in the in the tube itself, the water directly becomes steam.The here is the efficiency,
the efficiency is a strong function of two temperatures, one temperature is the heat
at which the temperature at which the heat reject it and the temperature at which the
heat is added, the temperature at which the heat is rejected is not under control, because
it is basically ambient, but the temperature at which the heat can be added is under your
control subject to whatever is allowed be material scientist therefore, all this cycle
basically the fund exploit this and they try to increase the mean temperature of heat addition,
the mean temperature at which the heat is added, if it is increase the efficiency will
increase.
So,Compressor, Condenser, Throttle valve, Evaporator and it comes back right m dot T
1 will not work here, h 1, h2, h 3h three good h that is it. So, here the equation will
be f 1 of m dot h 1.
There is no big design of this equipment sorry. So, this is called a sequential arrangement
the output of one becomes input to the other, any problem, a some people do not like h 4,
if you want to be threateningly formal you can still use h 3. So, this is sequential
arrangement, where the output from one component becomes input to the other component; everything
is linked. Now if you know all this equations, these
equations will come from the manufacturer or if you got the data for various values
of what is the performance andall that if you know f 1, f2, f 3, f 4,you can write you
can put all this together; write your script and simulate these vapor compression cycle
on your math lab, provided if you, provided you know the properties, enthalpies at all
temperatures and pressures and then you can start playing with the variables and try to
find out when your system is working well and all this and then you can define a objective
function, cost and optimize and so on. So, you can use smiling to the math lab which
can be used to simulate more than one component. So, if you are doing the B. Tech project,
M. Tech project, MS or PhD in system,system design and system design analysis and optimization,
I encourage you to learn the smiling. There is also something called, software also does
all this. I stop here.