Classification of Heat Exchangers
Hello everyone welcome back to heat exchangers fundamentals and design analysis we have some introduction on heat exchangers and in that I wanted to impress upon you that heat exchangers are of very large variety. There could be a wide variation in design construction the arrangement of the fruitful and application as well as science a picture classification of heat exchanger is very important and already we have started towards the end of the last lecture to give some classic classification of heat exchanger we will continue with that maybe we will repeat some of the points which we have discussed in our last lecture because they are very important and then we will proceed with further classification initially I had told that depending on humidity of the heat exchanger heat transfer transfer process direction of flow application is situated in classifications are possible once into classification that exchanges can be divided into two broad classes recuperated and regenerate is regenerated transferred directly from one point to another word to fruit may not maybe John will not mix with each other there could be some sort of a supporting wall which is a solid wall between these two fruits but there will be direct transfer of thermal energy from one place to another and this is called recuperators most of the heat exchanger we see around us most of the heat exchangers used in industry are of this class examples of silent heat exchanger plate heat exchanger I think you'll be the exchanges and many others then regenerate is there is an intermediate medium which will temporarily stored thermal this is kind of a store is dry heat exchanger and there is it hard medium in between two fruit strips and well they're they're also very important though they are not as many in numbers as the recuperators are should fix being regenerated rotating blade regenerated and there are other examples where we find as we proceed with the course so these are regenerated if we go to another type of classification classification according to transfer process if you recall this we have already told in our last class baby to give some sort of introduction but yeah we can see that between they can come in Direct contact with each other that is weird calling Direct contact and sweet they may not come in Direct contact in between there could be some other medium be eating solid bet flowingly queen-bee testing medium be in class particulates solid particulates so whatever it may be so that is your indirect and direct crossword clue that is that could be again single phase and it would operate multiface then there could be stories time and there could be fluidized-bed show in all these cases the tree to fruit streams are not contacting with each other well as direct contact guys there will be some sort of intermediate sorry immediate immediate mixing between the two fluids and that's why there is a limitation what kind of fruits things can be is Joe there it could be two immiscible let's say they are two different either in the liquid condition their invisible or lips A1 vapour and another is liquid they also many of the organs in chemical Industries are condensed in connection with water with Direct contact with water to these are invisible example of invisible fluid contact creating some sort of Direct contact I understand that there is no question can be done by spraying water I have give one example and then liquid-vapour if you turn off the liquid then if there is mixing then there is not much problem in many of the application we can have this kind of Direct contact with heat exchangers so important is a good example desuperheater and feed water heater opentype feed water heater are these kind of heat exchanger via Steam and water exchange sheet and there could be also faced transfer some of the heat exchanger we will while we are telling you the classification by some sort of description otherwise the other heat exchangers we will be later on in details so please at this moment is if it is important to know the types and I also encourage you to search literature to get some information regarding the type of ethics in discussing during classification only one particular getting picked up from our last classification that is included but I have taken an exam find that here the water in and out of the Serpentine coil or coil which is having a large linked with in this heat exchanger system comes out of it it is submerged in some sort of a particular way and this party pullenvale to make contain some inert material and some combustible material show through this one can send there and with the hair this combustible material may be coldest or some other solid fuel that will burn and produce heat but that it will be in this tree dies bed in the Grand solid particulates when does particulate will come in contact with that you should they will transfer it the first air is heated or the product of combustion that is eaten and then that hit through the valuable material transferred to the fluid which is passing through Serpentine coil kind of thing so it is an indirect transfer type of device and at the topic in hot air is going so it can give some more heat for the production of Steel this is one example very difficult kind of heat exchanger does there not many in number this kind of it is in Jackson not many in number but they are very important for electric conversion recovery of his teeth and burning of low calorific value fuel Environmental Protection now we go to another kind of classification classification according to earlier mentioned that this particular in the first case you can see there are three points in two to three passages central one I have mastered one intermediate one is too and the peripheral 1st show the intermediate one that is having thermal communication with one and three but other two fluids like 1 and 3 they're having only one thermal communication in the second case as there is a sale and in that sell their attitudes and attitudes are carrying two different fluids but she has thermal communication is there between 1 and 32 and three but she is communicating with with one and two so there could be different design that design what we can see that there is a Central tube at the top there is another fruit passing and at the bottom there is another person so again here we will have a different kind of thermal communication many design variation could be done is a conceptual some sort of conceptual arrangement I have shown but early to see in actual heat exchanger how sweet it is done on the left-hand side what I have shown on the left-hand side I have phone a plate fillet exchanger show in the plane finity India there is a mini very versatile I am I would like to proceed on without giving much details of the place minutes and then you can take it now that this is a place in India on the left side and you can see that there are three different colour green green indicates one particular kind of ruined then we have got blue blue is indicating another kind of another friend and then read that is with her through this influence and passing through the same heat exchanger then this is one example and plate heat exchanger are very good for multiple operation then on the right hand side you have got one example which could be a hybrid air conditioning system and in that you can see and that centrally there is there is one heat exchanger where to fluids are there it is a two fluid type or double tube type of heat exchanger but at the periphery there are scenes so that means on the periphery we can pass a hair so basically there will be two liquid and one particular one gas which is here and with these three fluid we can have some sort of its liquidity I have given the reference if somebody is interested this typical and very interesting kind of heat exchanger one can see the details from the reference itself I think here we need to take some time this classification according to the surface compactness we will spend some time on compact heat exchanger but this is the terminology which is used for high performance it extremely high performance could be from different aspects but one common feature of these attacks India that they are having very large surface area within the heat exchanger volume 25 please of the heat exchanger what we do we do not we have coined a term compactness and if we did not take with some sort of a simple beat so you see there is beta beta Beta you see the unit is giving metre square by metre cube so this is heat transfer area per unit volume of the heat exchanger define it from the hot side or From The Cold side
So what we will call compact critics India that depends on what kind of weed we are using so if there is heat transfer from gas to some sort of liquid then the competitive singer should have a better value greater than 700 and if this value better value is less than 700 then we will call the citizen as a non-competitive teacher suppose we have got liquid to liquid heat exchanger that means but besides me of the heat transfer service the solid surface we have got liquid or one of the liquid is going through a phase change unless they both of the liquid also can go through first and then the definition of compactness or the boundary of compactness is slightly different so here is better is better than 400 metre square per metre cube we will call it a competitive danger and if it is less than 400 metres per metre square per metre cube then we will call is non-compact one thing I have mentioned earlier than delay I I like to mention once again that the most of the things we I have taken from all I have done taking the idea from the book of fundamentals of heat exchanger design by hand circular which has been given as the first reference for textbook for this particular course and time to time I have also acknowledge this thing how many of the ideas have been taken by the work of shop by the publication from the publications of Prussia next next we go to a slide which is very important and one should I spend some time here to understand what is compactness what is compactness in in terms of army in connection with it if I have a meeting in the first case there are two slits lips as indicating at detecting let's say that you threw in some fluid is passing and the space in between these tubes there is another kind of need another it is kind of the most widely used Names of the humidity has been shown the 60 x l d x l into this so this is kind of a pitch between two tubes and this side there is another pitch between the two tubes the is the diameter of the Tube and from Elementary geometry we get beta in this particular with this particular relationship okay so I can be calculated that is that is that is the whole idea that knowing the geometry of the heat exchanger we can calculate beta well then there are certain other things that later see which are the compact heat exchanger in an industry where we have use of competitive it is very widely used so it will be I mean the least we'll be quite long wiry hair using a competitive so probably hear what we find that the earliest use of compact exchanger where we had to use compactor texting it's due to the requirement of the process so when we can see cryogenica text India rising it means liquification etc are the pageant requirement and there we need to have very competitive and then gas gas turbine rotary the generator that is already I have shown some sort of somatic diagram that is also competitive senior then automotive radiators now it is particularly now it is the automotive radiators what we are getting all all the heater used in automobiles whatever we are getting their very compact battery wire screens fear-based these are all competitive with this there is a comparison of some organism organ of a living being that is human human long we can see it is much more compact compared to the heating element extension document is some sort of organ in human body but it also serves the purpose of exchanging particularly there is lot of mass exchange to human and for that also we need large surface area volume to this is one of the examples how increasing the surface area within a small volume you can have very large rate of exchange okay with this description of this which is very important here there is again stepped in and heat exchanger so this is this falls in the intermediate reading what we can see human long is on on one extreme and on another extreme we have got plain tubular sail indubitably this is more or less one heat exchanger which is having small surface area per unit volume and if we consider human lung this is one exchange let us not call it heat exchanger it is having largest amount of surface area within given volume The amount of surface area with a given volume is kill this kid has been food at the bottom of Africa now this girl has been made that one side if we go from left to right then we are increasing their increasing the compactness means passages are becoming narrower and narrower messages to which fluid will be flowing that will be become that will become narrower and narrower so if it becomes more mellow then hydraulic diameter with reduced so in this scale from left-to-right hydraulic diameter is reducing the definition of hydraulic diameter that is known to all of us show based on that hydraulic diameter has been calculated and you see here we have got some sort of relationship between compactness and hydraulic diameter bringing some sort of a sigma Factor here the value has been given and then along with this one how the compactness and hydraulic diameter are related beta is equal to 3333 by DHS is in metre cube per metre Surya metre square per metre cube this value has been quite a few other things there in this figure better spend some more time as we have told that plane to plane to listen to it which is most commonly used in a large variety of industries which is one of the oldest type of industrial heat exchanger to B42 is invented by human being that is having very less compactness and then what we can do this compactness can be increased that if on the gas side we provide some sort of contact service then plate heat exchanger that is having less compared to this and this here again we can have some liquid side contact surfaces and then here you see the heat exchangers so what we can have in this range starting from rest compactness to high compactness plane cubulous lnt which exchanger then slightly more compactness plate heat exchanger then plate heat exchanger with different kind of fence stripping Andrew between heat exchanger automobile radiator there could be different design nowadays the design has been changed with micro scale geometrical passages teachers come in geometry and the tube you met report has changed then metrics iPad screen type heat exchanger in between we have got trigenic heat exchanger gas turbine rotary weekend what kind of heat exchanger which has become very important nowadays that is your micro heat exchanger services become very important of the manufacturing development in the manufacturing methods we have got different methods of creating very small geometry with kind of large amount of surface area surface variation surface variation will increase the heat transfer coefficient surface area will increase the rate of heat transfer so we have got this this this kind of variety that means micro heat exchanger services and when this micro here we can make micro and micro scale things for electronic industry in a large volume of this increase is a very important to understand this one if we use the compactness of the heater off predicted that the other aspects we come but let me cursorily tell at this point that this is not without any penalty because when we make it very compact then the along with the complexity of the manufacturing process is the pressure drop that also increases and one has to manage the pressure drop and if the pressure drops increase is Justified by other benefits then only one can go very competitive the other thing is that that is the passage is self small there could be a possibility of choking of this family there could be a possibility of choking of these messages because initially a heat exchanger is new and clean but as the time passes we will have the position on the wall of the transfer case which is called for me which is a very important aspect of heat exchangers time to time we will refer to Falling and if time permits we will also try to see that house Holyoke is how we can respectfully the contact heat exchanger should use the fluids and should be operated under operating conditions which does not promote to this is another important aspect of competitive senior and if that is satisfied then only competitive figure can be used I like to end this particular lecture we will continue with classification of heat exchangers in our next lecture. Thank you.
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