Heat Exchanger Network Synthesis - Part 3
Welcome back, so we were working on or we are learning the heat exchanger network analysis by pinch technique. So the pinch point I have introduced to have got the pinch point, the pinch point devides the problem into two parts. One is hot end problem of the heat exchanger network, another is cold end problem of the heat excganger network. And each of these ends can be designed separately and the design has to be starting from the pinch point. So this was the message I had give me the last lecture now let us look at the rules for peeing change matching number of hot a number for tint number of hot springs village the number of course okay andok and four Golden number of Coldstream should be equal to or less than number of this is very important and why it is so hot the hot and we cannot use any call you so if we cannot use any cold utility all the hot screams are to be cool with the help of Coldstream only two number of cohorts team should not be less than call Steve and same is same old school for the golden in the hot and there are some amount of 40 PT and hot stream which can only exchange with extreme heat with questions so that is what I have told that at the hotel there is no call.dpd Horsham can exchange it only with the cold stream show the number of course you should be more or at least equal then the number of steps for individual match against extending the logic one can get see a seat capacity at the hot springs that should be less than the heat capacity weight of the courts plus the knowledge and that the cold LCC that should be less than CH4 haunted this cumulative thing also has to be taken into care ok so for the hot and this has to be taken into care this is not very stringent but generally this is also taken into care and sorry similarly for cold and also we will have similar type of now with this if we go to the next life we have got some example let’s say this is your hot stream and this is another get hot screen and we have got four as the heat capacity range for the first trip to as the heat capacity weight for the 2nd Street and for the Arts community Coldstream this is five and this is three show difference is this one is solution is possible in this case now if we change these values little bit or we bring in some sort of a new kind of me another Coldstream okay first one first one first one we are getting that first one this is God this is God of war stream has got a heat capacity rate of for Coldstream has got a heat capacity rate of 5 and this is important after the 8.45 is more than four solution is possible and then cumulative thing also solution is possible so this is a good case in this case 4525 is more than 4 that is all right and then here also stimulating thing if we see then then also the solution is possible cases we can get some sort of solution and in this case what you want to see here the number of dots per inch is equal to number of Coldstream this is also one condition which to be satisfied and hear the number of what stream is less than the number of Coldstream so this is also something which is desirable for your hot end of the pitch similarly we can proceed we can go to the next slide so far Cotton design this is this is the thing number of hot stream should be less than equal to number of course to if not then what we have to do we have to split the cost so if we split the Coldstream then the number of Coldstream will increase so then we have to check with the number of what stream is higher than the number of caustic then once this is this is the most stringent want this is satisfied we go to the next sch is less than equal to c c for each match and for cumulative stress strain yes then we can get this solution if not then we have to get these streams be fleeting and which district splitting we have to go again to the top ok so this is your cotton design now let us go back for our let us go back to this problem with which we have started showing the hot and we have got history one hot spring starts from 150 degree celsius equals to 90 degree because this is our 10.1 Coldstream start from 70 degrees Celsius that is the pinch point and goes to 125 degree Celsius from 70 degree celsius to it has to go to so what we can have we can have this solution between stream 102 we can have a heat exchanger and we can have a heat exchanger hear the temperature difference to be 90 and this is 70 that is a pinch point and then if we know this temperature we know how much heat transfer can be done and here we use some sort of a philosophy which is called stick of philosophy what is peacock philosophical philosophy is too old or is like this that we will have them but such that at least 1st it’s heating or cooling requirement is satisfied so let’s say 150 degree has to be cool to 90 degrees Celsius so if it has to beso how much did it take we can calculate simply from the algebra and then probably what we will get that the hot scream will be cool from 150 degrees to 90 degrees Celsius windy Coldstream we visited from 70 degree to 118 degrees Celsius but my tablet temperature is 125 degree celsius so what can I do the rest of the heating of the Coldstream can be done bringing 143 how much hotter will it is needed that also you can calculate then there is another Coldstream what I should do for that has to be heated from 70 degrees Celsius to 100 degrees Celsius know what stream is available so I have to bring her stupidity and anytime heating has to be done by the hot plate ok how many heat exchanger I will need I will need one heat exchanger over here one hot utility heat exchanger another 40 pretty heated seat I can go for an alternate solution let’s say the hot stream 13 week old stream old of methodology have to use the copier have to use I can see that the third Coldstream know this is the fourth Coldstream this can be totally heated with the help of the hot chick I will7200 degrees 40 degree temperature difference kW multi crescent Celsius is the heat capacity weight so I need 90 kw of heat but that will not cool hot sweet heart string instrument that and that can be done with the help of your Coldstream number three okay so he had 30 kw of heat is to be in can be instructed so that means yet 13/94 what that means 120 kW 150 degrees to be cool to 90 degrees Celsius temperature difference is 6060 into 2 that is 120 and 120 has exactly been taken from the hot stream but what about the Coldstream Coldstream is to be heated from 70 degree to 125 degree celsius so what will happened this is not enough so I have to use 10 ticket so basically again I am using three heat exchanger but I have got to alternate solution even more than that one can get in specific cases and these are the flexibility of the design I am getting more number of solution I gave then actually many of the practical things I have neglected in a planned whatever practical things are there I had neglected like her to slim cannot be brought together or heat exchanger do it is very small with capacity or with a small capacity should not be used to those kind of things I have neglected so now I have got many alternate solution means does practical aspects now I can see and what is the best solution I can pick up let us go to the next light street fighting for school and now I am coming to the cold so in the cold and there are superstring and two coats the hot stream and Coldstream numbers are matching so fast requirement has been satisfied ok at the cold end number of hot stream should not be less than the number of old Street that has been satisfied but you see the hot stream this side is hot spring 3 and 2.5 I believe just let me have a look let us have all of us let us have a look into the problem so hot stream 1021 is 2.5 and cold stream one is three and another is a timer lead 2 and 2.5 is the hot stream and 8 and c is equal string now if I like to maths that 8 and 2/3 and 2.5 what is happening 8 is more than three this is good but two is not more than 2.5 so this is not good this is not we are not getting this solution over here more than 2.5 here we are getting a solution sorry it is the cold side and 2.5 is the hot side hot side should be more so here this is not a solution and this also this is the solution because what side is more than the cold side but in both cases one side we cannot match in one match in this match listen this match we are not getting solution but this gives solution because what side is more than coresite if we switch over or if we just make it reverse then uncc the hot more than two biscuits with the solution but 2.5 is less than 8 but that does not give the solution latest free 27.5 .5 and 2 and this side it is 3 and 2.5 3 is more than 30 more than 7.5 so this is not a good solution to .5 is more than 2.5 is more than .5 so again this is not a viable solution so here’s what we do hear what we do is that let’s see just to meetand sorry this can give you bibles solution because not stream 7.5 and this is three but this cannot give a viable solution because this is your Coldstream and it is less than .5 less than so now we can have 7.5 and .5 and here also we are speaking it let’s say this is 3 but we have got 3.5 and 2 show displate we may split we may not speak so I have shown that in which Coldstream has not been in this case cuz she has not been split in this case could not be in this case but we may have to split now we have got the Golden solution this is one hot stream it starts from 90 degree celsius that is the pinch point goes to 60 degrees Celsius another hot stream it starts from 90 degree celsius goes to 60 degree celsius its seat capacity that is a and we have seen this has to be split so we have split it and do if you have plated display today’s the pinch points near the pinch point we will have some sort of a matching between the hot strip and the Coldstream with that we can take of the Coldstream number for total total hitting requirement of the but he sure it can it requires two heat exchanger just like this as I have shown but with all these things II hot stream which is which is actually this is one this is to source the second hot steam can be totally cool to 60 degrees Celsius but the first hot stream cannot be cool to 60 degrees Celsius so we need some sort of a cold with the cold utility we will be able to quit from 80 degree 2 degree celsius so you see how many will be needed 1234 and all the and temperature of the heat exchanger we can get okay so this is the solution of the content we can get another solution but in any case as I have told that the hot stream with it capacity weight 8 has to be split this has to be sweet as I have shown this has to be speech ok then in this case the fast or stream is to be matched with the some sort of an intermediate one that is what we can see this is possible and then we have got other matches so this is also one kind of a solution which is possible and this is also one solution which is possible and with this we can get two different two different alternate for the cold and also and with this we have gone to different solution of the hot and we have got two different solution of the cold end and as I have told that any solution of the hot and can be combined with any solution of the coolant so basicallyso basically whatever we have done with that we can get four different solution of the entire heat exchanger network basically with whatever we have done we can get four different solution of the entire network heat exchanger network and what will this solution gives us this solution as I have told from the problem table method whatever we have got that is very important that we know what is the hottest it’s minimum amount of water filter to be used we get what is the minimum amount of gold infinity to be utilised so that means recapitulate it once again min 16 years should be very important things we should you get from Finch Alicia minimum hop utility minimum called euclid minimum number of heat exchangers with minimum hot and cold abilities stream matching for every heat exchanger then terminal temperature and capacity of Egypt more than that also last one Legacy the terminal temperature and the heat capacity so from there actually one can proceed towards the heat exchanger design which we have done but more than that also we can get like the pinch temperature in Italy we have to but which temperature is one thing which the designer has to say it so if we go for smaller pinch temperature then more energy recovery is possible ok but initially the cost of the heat exchanger will be more because we have to use better heat exchanger or larger heat exchanger so one can have some sort of the optimisation between the operating cost and the initial cost and one can also decide regarding the pitch temperature many other things are possible but this is a good course of heat exchanger here we cannot devote more time on the time on. Only one topic that is the heat exchanger network, with this if you go to books etc there are books, there are papers, so if you go to that further details you will get for heat exchanger analysis. Thank you for your attention.
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