Plate fin heat exchanger: Numerical Problem – Part 1
You are welcome to this lecture we were talking about the plate fin type heat exchangers. Now today in this lecture will try to solve some numerical problem where we will try to estimate the heat transfer or the heat transfer taking place. It’s basically simulation problem we’ll try to solve fine we’ll try to estimate what is the amount of heat getting transferred in the applicant iFit exchanges so now let us look into the details of this playful type heat exchanger where you will find that all the heat exchanger dimensions are the details will be given with some inlet parameters and accordingly we will be trying to sell what is the exact temperature of the fruits names and also will try to estimate what is the amount of heat getting transferred so it now look into the details of this he text me a configuration this has been I'm sorry this is fundamental design in this problem has been told is the overall dimension of the heat exchanger has been given so doing that one really does look into the other parameters that has been already been told stay here this is basically your heat recovery exchange about the gas and air will be exchanging kit so the exhaust gas is preheating the air so as we can understand that the exhaust gas is preheating the air means the gas is getting cold and the air is getting healed up so this is the house clean so this train is a hot spring and there is basically Coldstream so we have a to stream exchanger and as you can understand on the configuration that this is basically nothing but a cross-flow type heat exchanger solar systems are there in a crossbow arrangement then what has been given as the gas Florida you can see that the gas flow that is given and it is a parliamentary floor right to it is not the Casey in terms of kg per metre cube per kg per second it is in metre cube per second and also its entry temperature is given it is entering at 900% to get at a pressure of 160 kPa kilopascals satellite is 1.25 per second floor entering at a temperature of 200 degrees centigrade at 288 pressure but we need to look at the cemetery this is an upside to screw this is the specification even find it this has been taken from the Kaiser London theatres near book and this is an offset prescription with the one by eight the it was the nomenclature given in Castle London and 19.86 so there’s the one that stands for basically we will look into that part but it stands for whether it is the length length of the fan height of the face and this is also facing number of things by inch so when we have this knowledge about the offsetthat means we will be able to find out it’s Fahrenheit in spacing then what is the free-flow area and etc so then we have another the information given to this is that in the similar feel the same feeling brother are used both in I’m in for the gas side as well as in by your side book there and guess that will have the same officers 21 by 8 19.86 so these are the things that goes along with that the frame hi sorry that he text me that height than width and the length of the exchange has already been told so now if you look at this geometry he will find that this is the gas flow area I'm in this is how the gas is flowing on thisthe air frontal area is this much is the air frontal area so the air is coming from these giant and this is what is the frontal area that is 1 m by .3 m more if we look at The gaslight know what will find what is the frontal area we know that this is the frontal area I’m in the gas is coming from the this side so it flushes this is what is that a surface area on for the gas and what is the dimension we already know this dimension is the one and this dimension is also point to meet us here in this case we have both the frontal area similar to each other so we have this informationit is good and it has been in the construction of the idiot that means it is across floor I think it’s near that is also given so now you can look what we have to estimate is the exit temperature I mean200 English central get and it’s pressure has only been told as 200 kPa so now what we need to find out is the exact temperature of the air and what is the exact temperature of the gas so when we know the exact temperature of each gas we would be able to find out the capacity of thelooking at this problem now it is not difficult for you to because of previous knowledge we have already talked about it like this is basically I waiting problem all this is nothing but he text me that performance problem so rating of heat exchanger performance performance evaluation of simulation whatever we call it as simulation so we have been told about the geometry of the exchange and we have been told about the inlet conditions of the two bit streams and on the heat exchanger a specifications unknown we know about the fine details we know about the floor arrangement we know the overall dimensions of the heaters near do you know this is the length is 1.3 metre by 3-metre so basically it boils down to a simulation problem so if we have a simulation problem and now or what would be our approach to solve this problem before going into that approach we would now like to have a look into the film details as I have told you that this offset stripping 1 by 80 19.86 what does it mean then to water the information which we help for about this thing so if we now look into that part latest into that part so these are the specification if you go back to the Curzon London compactly textbook they will find that this is the geometry conspiring to this geometry this is what is given as I was telling you that 1 by 8 what is made it is basically meaning that it is the length length or this is very not this is the floor but this is the floor side and today after certain distance the landline this trip things are upset so here you can see from the top of that this pain and between the screen that is another feeling between so it is getting upset and to slant slant the on the Finland is now we often call it feel in the hallway of his college plans length so this is equals to .125 or 1/8 of an inch so in terms of the metre this is .31 and 3.175 into 10 to the power – 3 metre so we have the film pitch the other a parameter as you can understand that to 1 by 8 and 9 2.86fence panels and disconnects ponds 2017 80 to 82 number of feet in one metre in a metre it would be able to accommodate Sam’s 72 number of fans found that you would be able to estimate how many number of fans are there if we make one metre long length of this thing so we are going to get some 782 number of feels so this is one thing between long-distance it is having some fun at thickness so between this point to the beginning of this one this is the repetitive block and this pain this is the fence spacing so now we have the film pitch so that will give youheight silverfin hide on the plate spacing that gives you the b is equals to .098 inch in metre this is 2.45 iPhone 9 millimetre and Finland the other landlines are ready as I have told that it is a .125 inch or point-to-point 175 ml so we have the as soon as we have talked about the this thing we know about that this is what is the Fahrenheit this is pin spacing and the film thickness is also given off in metal thickness that’s also given 0.21 2.10 to millimetre and that’s what is the film thickness that is I mean this between this is point 12.10 2 millimetre so I'll put this informationthe Field of the heat transfer area to the volume between the plates is also known and also we know the flow hydraulic diameter so this hydraulic diameter is basically we estimate in terms of the free-flow area and the the heat transfer surface area and the length of the fish soap found that we would be able to estimate the hydraulic diameter into the already been given for this type of thing and it is this matchup 1.5 for the imm is the hydraulic diameter of this pain then we have the total heat transfer surface area divided by the volume between the plates so this beetle this is an important parameter so when we know the overall volume of the volume between the plates we will be able to estimate the total heat transfer surface areahusband regarding this one is the female by the total area of this is again something which is very important for us if you look into this parameter we will come across this value when we talk about the overall fin efficiency of the America texting so if you remember that we have talked about this this is that they’re the two plates the connected between that there is a pain and we have the CTF the efficiency of the single thing but it is not a single thing that I had multiple pains associated with that process available in related to it it’ll cheer up and it was you know an ETA if I will find their correlated by the overall this is the overall fuel efficiency and they are correlated with the individual feel appreciated by the surfing area by total area a FYI so that we will come across the south end of values will be the necessary particularly for estimating the heat transfer on the simulation of the heat exchangers are given in this one this weekend on the calendar book so it is not only about the geometricaltriple parameters can we need to know to talk about what is called the inspector flow hydraulic data so we have against talked about it or we have shown him earlier that this is expressed as a function of Jay and if there’s such a is basically the same number 49 for the number to the party because the hair it is given as strengthen number to the part 2 3rd and this all these data points are making this points are the experimental values so this is the best interpretation so even have the numerical values as well as this graphical values for this the one byspecification of spirit of grouping similar type of different type of offence and with different geometrical parameters will find in the killer London because we’re interested can look into this concert will be fine that both the chair and the sister is expressed in terms of the standard number and PIN number to the park to 3rd and this is how it is with the Reynolds number so we had tocalculating the scantron number phone number 232 3rd or the same value and this title number contents that heat transfer coefficient that will decrease if we’re looking for a particular site and we also have this friction factor which will be necessary if someone wants to calculate the pressure drops you may remember in some of our earlier calculations were trying to estimate the pressure drop occurring in the fridge to the film passengers and then we have been told about that okay this is the friction factor if you remember in that example we have been told about the Reynolds number and corresponding toisolezwe specifying the fee that means the fine details are known we have in the geometrical parameter is necessary for the faith and we also know what is the friction factor or what is the chill factor so please don’t mind that these values have been estimated experimentally but there are also the correlations available for the offset stripping the way we find out for the different playing the triangle offence or others and one can also use the school relations while estimating the transparent pressure drop GMAthe experimental data are found to be more reliable okay so now we will go to the next time we will I mean this is the exchange of this expression you remember that we have this expression for the Epsilon ncube and the CR value of the capacity ratio 3 find that this is this particular correlation is meant for the cross flow heat exchanger cross-flow direction Little things which we have already announced visit the information already available to us so based on the available information now we have to frame hour the army or try to solve this simulation problem and one by one we had to go into it so I think I understand that since we are trying to solve this simulation problem when we have a complete knowledge of the tickets in the geometry so if we have the German belong to us what is the approach that we will let you know we have to think about like going to The approach will be applicable or not so if you look into the temperature differences but we do not know exactly what is the temperature difference because we are trying to find out the exact temperature so we don’t have the knowledge about the temperature differentials at the entry and exit so we won't be able to this expression for the NT what it talks about is the way by simianthe hot side then we have the evolving since then we have told her this is for the heart side then you’ll have the email for the cold side and that will be say it’ll Cheadle a heart and then age heart and then you have the similar terms for the cold side and the side door glue is the resistance offered by the separating plate so if it is a separating play the freight is trying to flow from heat is trying to flow from here to hear this because of this fine night thickness of this world this will also gives rise to some kind of resistance to the flow of heat and that we have taken into account here so far we have the common sense we know the fence person furcation we would be able to ideally calculate the age we would be able to calculateideally we are supposed to evaluate the word necessary for estimating that you and the other part that see me what is the minimum capacity fluid we would be ideally able to estimate an even better and we will be physically able to calculate the ENT in Raleigh and this one’s remember until we know from this relation what is the asylum so once we know the Epsilon our relations I’m in Epsilon from the Epsilon is related to the inlet and the exact temperature and we can easily calculate the exact temperature and well you know the exact temperature if it is not difficult to find out the CDT from the MCP 1034 the hot and cold sciencewhat is the you where and when we try to find the way we need to find what is a tuxedo and not only that it is hero we need to find out age age and also the heat transfer surface area so for that we need to go systematically one-by-one first couple to start with we need to have an idea about how many number of layers of air and there’s a guest rooms are there in this particular heat exchanger and once we know the number of players available for the gas and the flip side then we have an idea about the heat transfer surface area available for the gas side as well as for the air side so we will try to first estimate because we have the overall dimension of the heat exchanger blown towards overall heat transfer limit the number of heat overall dimensions of the heat exchanger known to us then we can estimate the total number of players for the inside out for the gas side because we also know one of the number of I'm in the overall dimension of the fieldthickness that has been given us point a 5-mm this this is equals 2.5 mm so we know this point this is the thickness of the separating play twin or about the same height what is the Fahrenheit that has already been told so we would be able to find out how many such players constitute I’m in a if I put one over the other in between of course there will be the other lads one layer of fat free stream 1-0 of the gas station and client that the total number of players will constitute that heat exchanger so this is that would be the total heat exchanger like that similarly I am in number of players on this side on this side will constitute the total dimension the total dimension is there been since the individual field details are given below the separating other fins associated with the gas side and the fluid side rear side. So based on that information we’ll be able to do all the calculations so we will look into that in another class, thank you.
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