Phase Change Heat Exchangers – Part 2





Hello everyone so we were discussing heat exchangers involving phase change. So at least one fluid of a two fluid heat exchanger or multi fluid heat exchanger will change its phase within the heat exchanger. So those kinds of heat exchangers are called phase change heat exchangers or two phase heat exchangers, also we have told that our concern our focus is for liquid to vapour or vapour to liquid phase change that means the two mechanisms and boiling and condensation and for that matter in some cases it could be operation also should be the mechanism which we will consider for face change and which are prime importance for face change changes what we will dotypes of boilers and condenser the level in the industry used in practice should we will discuss at the beginning and then gradually you Will Go how the transfer takes place maybe we will touch upon little bit of fundamentals regarding boiling and condensation and then of course take examples to see with this fundamentals how one can build up the design principle for this kind of heat exchangers we will take up condensers first and then we will go to wireless operators let us first start with some sort of classification of these changes to its classification classification has been shown that it is direct contact two main classification direct and indirect contactindirect contact then kind of concerned there could be there could be free and free type condenser and there may be packed column we will come back to these things sometimes after work to give some overview of a different kind of condenses probably once again we we refer to the diagram also but now before we start the process of condensation one should have some idea regarding condensers so that’s why I am giving the classification then I toldwhite coffin scene and used in industry what is indirect contact let me recapitulate once again here between the two fluid stream there will be some sort of a solid wall so in case of condenses also paper and the cooling fluid they will be separated by a solid wall should direct contact indirect contactif you type condenser silent tube type heat exchanger there will be number of tubes and these tubes through these 21 stream of redoing pass and then these tubes will be exchanging quit with another system which will contain is very pertinent question was that with the contents include will be on the safe side or the or the cooling fluid will be on this side this depends on this depends on application so in some cases we will find that the condensing fluid will be in the sales sell-side and in some cases of course it is possible to have the condensing to eat in the TV show both possible and when specific examples will come I will even refer to this point now sealant tube type of heat exchangers generally the extent they are not so perfect but for big capacity wiredspace etc are not restricted large amount of blood has to be taken care of so silent heat exchangers accused show in power industry we had surface condenser and I feed water heater should let me explain these two things we know in a in a steam-powered cycle in a steam-powered cycle show in the boiler the water is heated to produce steam the Steam condenses in the turbine to produce work and then the exhausting from the by which is at a low pressure and low temperature is to be taken into a condenser condition where skin is getting condensed we use in most of the cases water as the coolant so basically one side there will be a condensing vapour in the heat exchanger and another side there will be a single phase liquid that is something that we have contacted or cases what we can help what we can ask if we can have any large there but that is ratificationI will try to show you different diagrams etc photographs etc mean taken from the day so that you can get a good idea how the process take this condenser air condition is taking place on outer surface of equal length is called service contract specifically this name is used forgenerating electricity so we go for that that's too high pressure with the help of the temperature temperature corresponding to the high-pressure is the large and that temperature we do not get at the outlet of this has to be done by different method but also so basically busy also kind construction while it may not be identical to the main contents of this department but many of the features are similar to what we are having our main concern at this point let me tell youlet’s see this is happy school days one is your 11 is your open and another is your closed beginning let us have some basic idea we are going to the vhdx etc at desert actually you kinda so let me tell one thing here from where they come so there is a standard which is known as Tamar standard demarco or the master what time is stands for the past tense for please note it carefully tubular exchanges value dollar exchanger manufacturers and they all designsukup manufacturing I spell mechanical and see if somebody wants to find some sort of way single solution or n-type solution of the exterior design one cannot but to consult the timer show in the day before in standard sail configurations and these are these are indicated by capital numbers what I can mention earlier to do the different kinds of cell structures and and eghj etc some of them I will order not all of them but at least some of them I will we will see later on and then total condensation so one is called reflex and another is called knock back again for the time being I like you to do all the detail probably reflux condenser we will touch upon to show what we can see our users and another use there are different they are used in different kind of designs are possible let me tell youis taking place and we have solved our problem so you can you pick one kind ofI will not be able to discuss in details but let me at the beginning you should have some idea that what are the different contentious now let's go back to bed nextbecause probably I will refer to the diagram once again some of the pilot said Friday it in detail but for the sake of completeness when we have discussed different classification of condensers latest different types of boilers let me tell a word of question which I will use number of times that the classification is cetera are we are showing this classification just play the previous classification is taken from the book of odisha and their classifications are not just one may have a different type of classification classification may not contain a particular type of because these are we think that comes in our wine is the boiler off apartment put it down we have gotwho is pearland from the industry we get wasted boiler flue there could be different kind of designs some of them I will go and now it is another kind of her wallet which is coming which is not there in this list that if we have combined cycle power plant that we can have a chat is a heat recovery steam generator so that is not there in this particular least so I maybe some of the coming lecturer in there not that I should share their complete and will be of different kind of and with this basic guideline for now as I had told that we will spend some time on analysis of condenser and first what weekday is silent you tube heat exchangers are quite common we have done its design the analysis for sealant tube condenser is not different from that not much different from that and then as this is the most used condenser configuration so we will spend some time on it if I am telling nothing new I want to I'm not into because if it is condensing over the entire heat exchanger but definitely1 kg of the condensing later on there will be less fibre content in 1 kg of the condensing content to change and that’s why it is by the heat transfer equation for the cooling system that will not be much different because it is not changing its face a total rate of the transfer will be given by mean overall heat transfer why Meri ladli with that of course which way is importantokay because here it is in the blog platform should there should be some sort of it had all the condenser before it is pumped out so this is permanent licence office department they said this is called a surface condenser what what is important to note that the condensation is taking place outside what has been shown is a schematic diagram generally the team in late is much larger to velocity it is not like this but it is here I am showing condensation on outside of anythinga 20-18 film of liquid overdue and condensation is dripping condensation are off to type one is film condensacion so here we can see free condensacion so he’s getting collected that’s why you can see this liquid drop here here you can see that there is it is not uniformly covered by fee so there are some patches where there is no fee and yet it is dropped while condition which we are also familiar we have in our day-to-day life so these are the drops for I want to show you thatif there is a deal and the film will be like this and we get the overall heat transfer coefficient by KL this is liquid is the number to number 8 by ruelle is the liquid rule is the liquid density Rosie is the gas density ily is the latent heat of vaporization g is the gravitational constant is the diameter is this concert is there is the thermal conductivity in is the subscript only Queen show this is the formula for nurseries along the periphery that means with angle file and by integrating we get this kind of this is what we get for outside heat transfer coefficient how determine how to determine the outside heat transfer coefficient maybe we will refer to this refer back to this formula. I would like to end this particular part of the lecture and then we like to continue with this in our next lecture.