Heat Exchanger Testing – Part 1
Welcome to this lecture, today will try to understand an important aspect of the heat exchanger design and simulation. That is the heat exchanger testing, so what is heat exchanger testing? It is, we have to understand that are we have used two different kind of heat exchanger test surfaces right from the fin tube, then we have talked about the plate fin type of heat exchangers. Then we have also talked about the perforated plate, we have talked about the metal form and other surfaces and one of the important aspect for these services is basically to understand it is a different type of the playful type of surface is this is right between then we have always found that the plaintiff anglophone this is metal formed when we have also talked about the fact that originated so for all these services what we need is the characterization of these surfaces and when we characterize the surfaces the surface characterization properties will be used to generate the answer will be used to design or simulate the heat exchangers so this is basically some of the heat exchangers and very design or simulator a text we also needs to make a performance evaluation of those exchanges or like basically want to find out how the is the effectiveness of these exchanges also be generated so basically these two are the primary aspects of any heat exchangers basically the heat and the performance evaluation of the eight theit was for patient and pressure drop characteristics so here we find that the transfer rate is basically we have celebrated call heat transfer coefficient and that is generally expressed dimensionally in the form of kuravanji practice and the reason that cold wind chill factor we have that the parameters in Build-A-Bear at least that is equals to the hospital andbltv discussing details about this lecture and the matter will be available apartments in geometry what is the height of the train then the thickness of the friend then the same frequency frequency so this is the parameterswhich will be different for different type of face says we have the way we feel we have the Senate at 3 and we have other field licences that said I’ll show you just like just in a previous life save the plain rectangular plain rectangular tray and so forth so we have been a factor in we find that it is the function of the number find it is the function of the three properties and it is so you don’t function of the pituitary so they can understand that we will have the different heat transfer coefficient of friction factor in principle we will be able to I'm in pick n parts in Paramount design classes understand that function of this number and each particular geometry it will be a function of the Sam’s club in principle j&f the friction factor of the heat transfer coefficient dimensionless for more in its original form we should be able to predict from the competition afraid dynamic from the velocity and the temperature profile but it may not always the most accurate data or reliable data so that the authentic or reliable data most of the time I will before the experimental determination of the heat transfer coefficient and the pressure drop and when wethe data in the form of simulation simulation experiment to minimise the number of accidents so what we understand that the design of the experiment is always necessary so we’ll try to understand it in the next life so what are the experiments that those that possible or generally used for the determination of the heat transfer coefficient and the pressure drop particularly we are talking about the surface characterization so we have the transient technical or when we call it as single flowtechnik and then we have the steady-state technical understand but this time components of the but it is also it's very kind of something like this is more like the regulator test services are the disciplines that we have in this particular case to the way we talk about this Lee understand that we need only one type of test services particularly which is suitable for the generator or very high and detection yes we go for the single bro Technic but the steady-state Technic we need a kind of heat exchanger the surface and this one we don’t really need it but it needs a kind of the earliest displayed successive plates or the surfaces to be arranged as sequentially to tasty China Singapore condition about this two processessequential in the heart and all three steps from each side I do have written separately the equation for the solid part and we have also given the equation for the fridge parts and the in addition to this we have also another dance particularly for the solid part which we have not included in this one is the actual production of faith that means when we have two surfaces or I’m into metals and we have a temperature gradient along this so there’ll be an addict on which will take care of the actual production in this integration andpicnic and we have different type of numerical models are techniques to solve this equations and now coming back to our single to take one important aspect of it is the most accurate prediction of the temperature or the high transportation from this experiment is obtained from this outlet temperature prediction same here this is the typical experimental setup while the floor Express from this end we have a bill mounce type of this is the floor conduit through which the floor will take place this is the float strickler this is will straighten the floor because we’re doing the floor is taking place from this one through this bellmouth it is well my office to the Makers North entry of the air most of the time we use air and the freight and here we have the floors pregnantdepending on the geometry of the surface is the best surface and depending on the geometry of the best surface it may be a circular cross-section and it may be the best action movie of circular cross-section on it maybe of rectangular cross-section heater this is the heater and bring this heater is switched on this will heat up the say if this floor is where the air is getting streamlined and uniform velocity with the uniform velocity it is approaching this heater and before entering to this test section it will get uniformly heated and what we do is that we have some tango couples are the PLT plot number is 210 The Beatles on some temperature measurement and so we measure the England temperature and when it comes out of this heated floor or the air will be passing through this test section and when it comes out from this and it will also get heated up having it is it will be earlier when it was not getting rid of it was coming with the same temperature same in the temperature in Longfield temperature versus then but now this year features it has already been heated up it will pick up some heat on it will reject some height to this metal and then it will follow this temperature profile will be following this one so it will go to the flow measurement device and there is a blower to have induced kind of flow through this test section what is the kind of temperature profile that we expect and the inlet and what we do what we expected the exit so here you can understand that this is the actor equals 200 this is the temperature of the air and at this point I have started the heater switched on the heater and the temperature of this great so which is being measured at this point at this point before the entry to the test section so here’s temperature is keep on rising and add some tea towels to infinity it will treat your strength temperature at this point so when this is our you know after sometime it is reaching this temperature lol what is the kind of temperature we observe and the ACthis is our time with this following this kind of temperature profile and obviously as you can understand that this translate fennel in a bit with this time limit it will finally lead to approach this temperature so this is the only temperature but it is indicating it up the heating is complete it will reach to the all this era of the fluid that is coming out will have the same temperature as that of the destruction of that of the freight which was coming in so this isn’t it comes to infinity and this is all so we have the exact temperature the temperature will be increasing like this so now I understand from the orange theory so what we will try now that we have this data point for the exit temperature so what we will try now that we have this data point for the exact temperature so we have measured this exact temperature and theoretically as you have noted that this theoretical prediction of the temperature profile will have a perimeter college now we will put different value of the age to find out which value is giving a good prediction of the heat transfer coefficient of the temperature profile so depending on that value or save we will be this is corresponding to submit this is some other age value and the one which is giving a good prediction they will accept that value of the age for this measurement so like that you can understand that this is a this is basically trying to find out the heat transfer coefficient in a single measure metric so this is how we measure the heat transfer coefficient and mostly it is meant for degenerative time or if a very high is do it is injected as it can understand that only one through it is passing through these exchanges and it’s not the it's like in aand it's the temperature Disney on ice and the temperature on this site is also going to be you know on the timeat the inlet condition so it will start at 8 will start decreasing so this is in the cooling mode and this is the temperature profile which we did called when you switch off the heater and this is the temperature corresponding to the exit of the outlet so the temperature at initially the this is the exact dfo and towels to chill and initially when you have just switch off slowly it’s the temperature will be gradually drop it will be dropping and decreasing and he’ll also in that condition as we have switched out the height and the air is blowing on top of this one so gradually it will try to reduce and it will follow this kind of different profile this will also follow that one you know we have a set of data points we will update for the temperature profile and the AC and depending on the temperature profile didn’t you know as a input to that chair table calculation and they’re also for different age we will have different type of production of the temperature profile the temperature profile corresponding to the edge which gives the best fitting of this call will be the heat transfer coefficient so this has to be followed for different flow rate and accordingly we will have the heat transfer coefficient for different velocity of the year and corresponding to different re and we’ll be able to calculate the age and if this is the dimensional formula a transfer today then we need to calculate the non-dimensional form of it mostly used as the truth and this isthis is the concert will be coming out so we have the saturated steam or condensing Floyd on one side or the other side is there so the air is getting heated up and the saturated steam is getting contest so from this heat transfer we would be able to find out the heat transfer coefficient and the pressure drop pressure drop of course we measure it and the inlet and exit and now as I have said that this is a heat exchanger which is the best sectional what I mean is that what is the best surface is where did we put the test services the decimal places are there on the inside where does the skin side is slightly having a wider channels or know where we have the loan heat transfer coefficient and for the Yeezy drainage of the discounts that and have a loan interest calculation for that side and all the condensing condensing pretty much had heat transfer coefficient compared to their side of the inside so this is how I will industrial estate technically allowed there to reach to a study state condition and the scheme will be continuously flowing through this texting you and we will measure the condensate we will measure the flow rate of the air we will measure the data across the heat exchanger and then we will be able to predict the heat transfer coefficient and finally we have to calculate the dimension of dimension of the heat transfer coefficient of this technique will find that test on the on theand that’s also know that this is all so it may be substantial or it may be enough for a very accurate measurement of the heat transfer coefficient we should not neglect is this wall resistance will be awesome or did you hear me find that so there’s this is ita chiller is the overall heat transfer coefficient and eat I have is basically the fin efficiency and that this as parameter you know that it is 28 by Katy services location approximation and this is quite legitimate for playful type of fetishes and here as you can understand that SMS containing some hshm is basically the Queen height don't be confusedgenerally it’s a very high five electric type of a text in years but still we initially assumed 200 need to be one and later on anyway we have estimates an estimate of age then we calculate this it hurts REM and from there we calculate the ETF and from there we calculate the 80 and then we put those values on this site to get it corrected value of the age so that’s the usual tactic but I’m sure we have this equation that we know that one of the heater is the inside of the heat transfer coefficient is not the other side I’m sorry the other side is not known and weight calculated one light experimentally and then we'll try to find out what is the heat transfercommission on the unknown side so that we also have this relation to this is basically related particularly when we have a temperature profile like this I mean this is a common-sense table using and the temperature is giving it to be constant as father was previous a long chin and the temperature of the flight is going from this in the temperature to this exact temperature so this ad is taking up hit a from the condensing stay and the condensing steam is maintained at a particular temperature. So based on that equation we will be having this NTU Epsilon relation and from there we will be able to predict the Ua so we will come to that in the next slide. Thank you for your attention.
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