Heat Pipes | In-Tube Condensation | Alison
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Module 1: Heat Pipes

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In-Tube Condensation

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In-Tube Condensation
Hello everyone, sure if you recall that we are doing phase change heat exchangers and in that for the last a number of classes we are considering condensers. And condenses we have started with surface condensers, in a surface condenser condensation takes place outside the outside the tubes. The condensation takes place the vapour condenses outside with you through the tulips generally liquid cooled condenser and many of the surface condenser other industry and but that is not the only configuration of condensed there is another variation which is which is if we come to the park and fly title slide condenses into contention that means inside the tube also condition place and this process is known as education and there could be a large number of critics changes within tube contentious hearing this figure is flowing in the direction and condensation is taking place on the wall a grand piano whenever we think of fingers condensation show that the training is one of the issues and the rest is best done by bracket so far in this particular case what we can find that liquid is it raining in the downward direction which is at the same time there is also in the wrong direction so will quit in some cases there could be different kind of design that means they're going in the election kind of configuration is there hidden away in a car air conditioning system is there an outsideGreen by Gravity gravity of condensate is possible for article configuration as I have explain however the condensate field becomes thicker as it flows down okay so as we can this sick feeling weak becomes thicker so it will show the passage for paper and the condenser close in the downward direction and employees in the orderly flow between thein this case also remove condenser is needed and generally try to do this there will be enough pumping supply to the paper because we are not getting any let me explain what is happeningafter that I couldn’t explain to paper producers condenser there will be blocked play top liquid condenser and there will be free at the wall so here it is totally paper and here we will have deeper layer outside inside this liquid liquid condenser clear outside and that means at the periphery of the tube and then the block plate of liquid that will be in the core we can have this kind ofis a very important role and due to gravity the heavier fluid that is the condensate that tries to occupy the bottom side of the crew of the of the tube and it is called stratification so then the vapour and Molly Quinn they will occupy different parts of the tube at the clock side there will be paper and at the bottom says there will be liquid this is what we can see and ultimately it will be totally like we are showing some sort of some sort of configuration fire at one side of the cube superheated vapour a test and from the other side of the tube subcool liquid goes out and obviously the cross-sectional view of the of the tube at different axial location controlling force here this year that will be important here the gravity force is important why gravity force is important because we have got stratification but obviously if the liquid has to go out of the tube then there will be pushing from the other side and be liquid in Goa then it is single phase but this is a new life discuss floor inside the core there are dispersed liquid droplets and at the periphery of the tube inside of the tube there is and you’ll feel then you’ll maybe there will be will be in sometime we can get a kind of film distribution and after that we will have single phase 3 condition of thethis will be by this time the liquid will be saturated in perfect condition and after that it will be coolsuperheated condition and come out either in the two-faced condition or in this support condition it can come out such a variation of phases will be there and such a great variation of florajen 3 India consider the house a few condensation just to remind you what was the outside tube transfer configuration and on outside we had condensate field and then because it was getting rain like this second inside filling will get chicken dark as it moves down both sides moves down so you see we could have and this film is still this also have to remember that this film is this film is conduction theory assumes that it depends the transfer is mainly due to construction and depends on the temperature difference let’s see this TV on this side and Alexis this is tw on the wall side so the transfer rate of heat transfer that is dependent on your this is your TV and the CW it is dependent on TWC TV is one thing we are getting this kind there is nothis was single but in the present case we can see that there are different kind of so if one had to take care of this one so obviously different kind of going inside to be considered which is not very easy to do okay son himself will give regarding the design as we proceed but today at least let us understand what is the difference between Indian tube condensation and condensation outside that you what are the critical issues of YouTube condensacion should let us understand those things if we go to the next class then what we find that suppose at the initial phase we have got kind of annular and then the annular configuration has changed because at the bottom there is due to stratification some amount of liquid has come the actual configuration of the condensate field distribution centre tube like this code white potion easy paper in that there are small small particles which are the particles of the condensate and then if we I realise this the left side we can see the idealized representation of this kind of conversation 2 and angle fire fire starts from the top we can see that there is a distribution of feeling and it is basically feel condensacion there is a distribution of the film has become gradually thicker and thicker and should be due to collection and then be on for what we can find that there is a swelling of the tube quickly ok so there is a flooding of the cube if this is the situation we can try to calculate the heat transfer by some sort of by incorporating the problem we can see that there are 2 ratings games today'sshow up to angle fight we have got one mechanism of heat transfer and then below so that there is one mechanism and bottom there is another mechanism that is what has been written on the other side the total heat transfer coefficient if we have to take everything so ox25 we have got some sort of a transfer coefficient and on the other side we have got some heat transfer coefficient h e and then this age five should be taken as average heat transfer coefficient in the top portion and HP should be taken every heat transfer coefficient in the bottom portion this goes without saying that as this person is totally flooded with the refrigerator will not be much so in that case I will I be comfortable without marriage without committing and then each total is given by this kind of obviously it is dependent on fire and we have to find out the average transportation now we can find out with the help of theory and this kind of by this kind of funny clip which is valid for all this radian of angle what let us go to the next linenext night we get the total heat transfer coefficient but here you see we have brought a new parameter which is nothing but this if sale on this Epsilon is nothing but this is this parameter broad and this is nothing but your this if silent is the attraction which is given by this formula and annually or bubbling floor so this formula is 4 annually or Bobby floor in this region the transfer coefficient can be calculated from another kind of a formula has been given so there is a stratified condition which I have found another the previous life so we can calculate the age total total means considering both the bottom side at the stop sign of course bottom side is transfer we have neglected to everyday transfer coefficient calculator and here we are using some traction and with the help of a traction we can do this calculation for the flooring what we do we we we try to stay some sort of semi empirical formula and in the semi empirical formula what we can do you see Reynolds number pencil number best relationship we try to use and from there we try to find out the transfer coefficient for this is one kind of recommendation but we will use some other correlation and with that which is most commonly used for condensation a transfer and with that we will try to solve some problem if you problem in one problem at least we we try to solve may not be as rigorous as the previous problem but at least in tube condensation how one can take care of that we are going to discuss what we have got so far from the discussion that has in many heat exchanger condensation takes place outside the EU in many heat exchangers condensation takes place inside intubation is difficult to analyse compared to condensation outside because there could be different kind of clothes and mainly we have to depend on ocean outside to we could have depended we are we could have relied on the analysis which has been given by yourself by modifying this analysis we could have done the prediction of heat transfer coefficient but the same thing is not possible in many cases in ketchup into contention has been made this is the kind of thing where we still try to continue with your muscle kind of oblation or muscle kind of analysis is like this that we try to idealize the inside condensation of the tube like this that there is a thing feel and hear to some extent Castle creation can be adopted but problem is that we do not know exact please how long will this muscle coblation can be adopted because how long will this typical type of flooring will continue through this is one aspect which we have to pay I like here then there are other Florence public low blood flow flow flow bubbly flow and annular flow these three are the three main type of flow in case of our educationand some people suggest that chlorine best heat transfer calculation should be there by at the same time the florida-based calculation are cumbersome so one correlation which will suffice for a large range of operate operation large range of operating condition that kind of correlation will be good and we will gradually discuss that kind of correlation let us go to the next slide here we get some comments on YouTube connection after that we will see what kind of comments the conversation mean horizontal you may involve partial or total condition of the paper what does it mean it means that in most of the condenser we will find the paper is avariation of temperature of outside so we can find that depending on where we will have different kind of condensation inside that you are different period of the year so this is one thing so they the same condenser sometimes it may give that it is a liquid is coming out of it sometimes it is letting out coming out this one the two-phase mixture and depending on application the inlet paper many superheated the dryness fraction could be equal to one or transactiondiscuss this point earlier but let me because these are important let me repeat it once again that we have got a condenser this is the we have got a condenser this is the length of the condenser and this side is the temperature and condenser means it is giving away a key and it is getting cool so initially some liquid has ended then there will be evaporation condensation and then sorry let me repeat it once again initially superheated liquid has interpreted the EPA has entered and then condensation takes place and ultimately suffer liquid is going out of the condenser and then one can have this kind of a thing also that means the coolant that is going on eating on this show is we will have your superheated vapour then here we we have condensation and here we we have ok so this is what has been told in the previous slide and many of the practical heat exchangers are of discomfort hence the condensation process pathway first begin with a rivalry superheating John followed by a white wall desuperheating John Wayne saturated condensing John Wayne is saturated condensing job and finally early which subcooling these managers will be there and you can understand what is the what is the challenge for a heat exchanger designer to design such a heat exchanger obviously this point I have touched the phone earlier now also I am telling that this kind of designs are quite challenging and without iteration this kind of designs cannot be done so what we do and again I have told that let’s say for a particular duty we have somehow calculated what is the disappointing John what is the two-faced John and what is the circle in June but the duty or the demand of the heat load that changes so obviously there will be shipped ofif our design is very tight then it will be sufficient for a particular operating condition for other operating conditions it will not be sufficient ok the next point the condensing heat transfer coefficient is a strong function of local vapour quality decreasing as the paper quality decreases this is also one thing that it is a strong function of the paper quality and it decreases as the vapour quality like this one is just as long as there is taking place and some amount of heat is transferred during litigation will be upcoming the no I couldn’the condensing heat transfer coefficient is also a strong function of mass velocity increasing with him is velocity increases this point does not require much of explanation because most developed city mall will be the heat transfer too busy to even see that here also he will remain mechanism of heat transfer is convection oven convection we know as the mass velocity increases or the Reynolds number increases we were having a higher heat transfer coefficient so obviously this is not difficult to understand or explain there this is one important thing as again let me go back and explain little bit he transitioned also proportional to this data TW is the function of black males he transferred to special function of TW – dpw because let me write it correctlysaree less than TV and heat transfer coefficient VBA function of TB – so this is for nursing field condensation theory now in intubation is taking place and we have got very different kind of Florence these are vapour and this is liquid soap hear the heat transfer coefficient will not be dependent on your what temperature difference with this is a difference between your inner tube condensacion and conditions over the over the outside surface of the q once we have explained itshow accept that low mass flow rate in stratified type of floor we will not have we will not have any dependents on the wall temperature difference that is desert – CW which I have written as TV – TW show the heat transfer coefficient will not defend like this discussionUK inflation is completely different from the condensation outside the tube and and and into condensation is rather more complex phenomena due to the presence of different flow rhythms. The heat transfer coefficient can vary quite a large along the length of the tube and we will see how to calculate it with the help of definitely correlations are to be used and what kind of correlations, we will see in our next lecture. Thank you.

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