Heat Exchanger Network Synthesis - Part 1





Hello friends we had a journey in the domain of heat exchangers. We have started from the fundamentals, we have seen different types of heat exchangers. We have discussed what are the basic engineering principles of analysing heat exchangers, their application different types of heat exchangers other attributes like fouling etc. So all these things we have decided as we have discussed at least to a basic level we have discussed all this now we have come to the last topic of this particular course heat exchanger heat exchangers fundamental and design analysis this topic is it Indian network analysis by pitch let me give you some background this is a topic closely related to heat exchangers do not exactly the design of it is dangerous but we thought that this is an important topic which the person who like to have a general uprisal general overview of India should be included what is this all about it is like this that a single heat exchanger is very important it’s analysis thermal design hydraulic design mechanical design integration with the other components of the plant the system that is very but who inhidden power plant power generation we use a number of heat exchangers number of equipments dealing with energy exchange in that case how we should have some sort of interconnection between the heat exchangers so that is actually it is danger network more of it will be cleared now the course on this topic there are very important for chemical engineers process engineer engineers it's very important they are number onessay on this topic as we have done for other topics also we have a reference it is given in the title slide it said the design method for heat exchanger net worth buying enough and y in chemical engineering science volume number fiveand at least let us have some idea regarding network analysis so for that one of the standard method light peach technique I like to introduce next light heat exchanger network what is a heat exchanger network considering process plant many streams needed heating or cooling let’s say a petroleum refinery where we have to go for fractional distillation show shorten streams are to be heated and second-string fact we could okay and large number of streams at to be eating large number of pizza House heating and cooling can be done there could be utilities utilities like hot air hot oil steam does could be used for heating utilities like here water water refrigerated cetera the ending Aldi’sstream Ami from scream like to be called Steve said to be heated and hot stream set to be good to know if we can do it mutually the heating and cooling that can be done mutually between the streets so obviously from outside when did not have that much of energy PlayStation so our operating cost to introduce this reduces the use of utilities means this reduces the operating cost over this increases the number of to do this probably means so we want to put it of course the first goal is to minimise the use of utility surrounding cast energy when it becomes up and running cost will be minimised obviously lot of benefits not only direct benefits it has got also if it means we are we are we are generating more energy so sorry we are using more energy internally so our demand on fossil fuel sources of fossil fuel that will get reduced that is the direct advantage internet advantage is that when we are using less amount of fossil fuel the degree diction of the environment within the creation of this is my second okay and that is the first cold has gotten the primary activity secondary activity network is that I will try to minimise the use of utility but I will do it with minimum number offreedom network has got a very profound in today’s scenario this is very important in today’s scenario he has to be that long process plant or chemical process plan for that matter has been designed with without there some sort of considerations to eat integration of process integration analysis thisthere are different techniques of synthesis of at the pinch technique is there different techniques but we are using to remember that basically what we’re dealing with is that optimisation problem we are trying to minimise or something so this is a and optimisation problem there are many constraints particularly particularly when we are taking a practical power plant by practical process plant the plant is very large and there are many many constraints very conflicting constraints are there in many cases suppose one constantly have one effect or the other kind of other constantly have almost the reverse kind of effect so those situations are there so basically we’re trying to do all the optimisation problem now in the the demand in industry as far as this process integration is concept one hot streamer each one is to be cool he is having initially and high-temperature I have to be if you look at what I can do so there are many Coldstream available which needs to be heated so we can have some mutual heat exchange between a point and see what each one and see to H1 and see three by these three heat exchangers but that does not bring the stream at 1 to the target temperature so ultimately what we have to do at the end I need to have a cooler and from there I will have the required temperature minimum number of heat exchangers that is you mean that is equal to 8 – 1a profit streams how do we get how do we get a that is number of Protestants and one and number of utility Street and to show if there are any number of process streams including both hot stream and cold springs and into number of people it is showing is equal to 81 + 8 and then minimum number of wickets from here all right this is this they're going to pitch for the discussion at which technical iswhere is only hurting pretty and only one called utility of incapacity this is specific to our discussion that there could be many holidays that means we can have her abilities at hundred degree celsius 150 degree celsius at 250 degree celsiusall the any of the other any of the hot steel temperature and capacity will be fine and and then there is another utility that the cold utility is temperature will be worse than any of the Coldstream temperature and capacity is itwe’re considering steady-state operations and there is no restriction sometimes two streams do they can give very good energy cannot be mad because the two strings are at to extreme end of the plant bringing them close is difficult or let’s say 1 scream is very hard as it is better not to put in heat exchanger that particular stream along with the city directionsnow we are trying to analyse the problem with the help of it with the help of a we are trying to analyse the beach technique are trying to learn the technique with the help of a problem which has been taken by taken from the reference which I have given that is lean of an invoice and this is a very famous problem too small but it is a very famous problem and many people have taken this problem for explaining what is your ETA and the hotspotc b x m x to the z this is 282.5 and 330 different value and Dale 30 min is 20 degree celsius what is delta-t minimum minimum minimum temperature that is reliable between to sweet street that is used in 30 min sometimes it is also called the beach this is used to it we cannot let us go to the next slide in this light what we find that this side is the hottest 100 stream Wii u noted by one that goes from what 150 degrees Celsius to 60 degrees Celsius and then the second fluid stream that goes from 90 degree celsius to 60 Coldstream 1 Coldstream starts at 20 degree celsius and cools to 125 degree celsius another team starts at 25 degree celsius and it goes to undertake we have got this what we can see that in which temperature range it is possible in which temperature range will change between streams there is there is the onestream from 25 degree to 60° but the hottest temperature will be in only 6 and then here again we can see that heartstring temperature from 15221 25 degree celsius no old Street has to be brought to that high temperatures this is what we can see if we can see that the temperature either via the it is initial temperature is there are the final temperature of there to do that strategic temperatures points of the internet work so what we can see 20 degree celsius 25 degree Celsius is 60 degree celsius 90 degree celsius and degree celsius 125 degree celsius at 150 degree celsius it becomes it becomes important in the order become important in the internet work that 2562maybe extend a let’s say come 2nd degree celsius to 150 degree celsius in this entire temperature range there are Jones and in each zone there will be fewer number of Streets there will be somenow with this background let us see what is the goal of heat exchanger network synthesis we had to have minimum utility the way we will send that synthesise the extender network that we have got issues of minimum that means what is the meaning of gold what is the minimum usage of cold utility and what is the minimum usage of hot utility I can describe two things I have to find out from the synthesis of hit its area network then screaming inside here you see in this job 60 degree to 90 degree celsius in this job in this part of the network there will be all the force between the streams will be exchanged between stream2stream for and stream so that I had to tell from my this is called stream and there will be different how many which another but how many heat exchangers are to be there everyday I have confident they are there in diary tile countertops so there will be two streams for extreme there will be two temperatures in the temperature right now in temperature so far this year there will be four terminal temperature two inlet temperature and two outlet temperature so all this food temperatures also so then I will get a complete picture of the heat exchanger let me go a little bit that we have got or let me use this what we try to do that we try to combine the Amit we try to combine all the old strings and again we try to combine all the hot streets so let’s say instead of these 434 and 32 hot stream we have got only one hot stream which we call super it extreme or composite what's Indian hear it wind up summit capacity I had mixed with the street so hear the heat capacity that will increase because to stream something so I can have some sort of the heat capacity there at each is everything on the hot Steam and four tickets so next week I am doing all the hospital I am combining together and all the cool stuff I am combining so obviously it capacities is different and interesting what I have done is this the composite heating carbon-composite cooling car I have got I could have been a different colour because this is actually cold but I have given great to mean that that is has to be heated and this is to be cool so what we see that composite cooling car this is your composite cooling car and this is your composite heating car combining all the Coldstream together we got this car and combining all the hot sleep together we got this so what we can see that there is some overlapping temperature show ok so there is some overlapping temperature June and in this overlapping temperature Joe there will be exchanged between the streams and where the hot stream will not be able to supply the hill there I have to use a utility and again when the Coldstream will not be able to extract the I will havethat based on an assumption we can solve the heat exchanger network analysis or we can have what we have to help that we are basically having all the Coldstream number of full-speed we are having number of hot springs it capacity weight of each of these films are there show heat capacity weight of each of these streams are there so we can create some sort of composite card. This composite card will give us in which range mutual heat exchange is possible and in which range mutual range heat exchange is not possible. From there we will proceed further. Thank ou foor your attention.