Tubular Heat Exchanger - Double Pipe
 
Welcome to this lecture, in this lecture we’re going to analyse the tubular heater heat echanger double pipe type in details. So already we have talked about the double pipe heat exchanger in one of our earlier lecture classes and we know that how it looks like and it’s the tube in tube heat exchanger it can be added hi there in counter-current heat exchange is more or it can be arranged in the parallel flow through its teams can be arranged in the parallel flow mode so it might look into this constructioneither it will be as it has shown that the fed is entering from both of us are entering from this end and designed and they’re contributing a countercurrent an infant if we put this floor from this link and display from this isn’t it becomes her life so adamant now looking into the construction of this geometry we see that these two are the support structures to keep it in position where as these are generally flanged connection so if we remove this partI can’t believe we have the use of cleaning please have the advantage of using these exchanges that we need or I mean both the fruit stains out of extremely high pressures are one of the foods to myself extremely high pressure on the negative side we have generally typically small surface area situated with this month and we have to literally bulky and a bit expensive this is part of the surface area if we look into it’s very expensive Safeway going to the find that is there can also be connected in series or are they can also be having it in the parallel linethe husband has been connected in series it means that one of the exchange of the fluid is entering from this end and then it is taking a turn then coming out and then it is going and enter into the second here be similarly the other fluid if we look at we will find that this fruit strippers coming from here coming from this site and we have an external directions and this is that every otherit is divided into two part one Barbie going to the stream and it will carry on like this the other part will be distributed to the second helping so this is entering here this is entering as this point so that’s all it is getting divided into two what’s about the other fruits trees the other fruits take me to look at it is entering from this side it is coming over here they’re just coming over here and this is getting distributed to end and move out like this but what's about the other Christian how it is moving out this is coming over here this will be back like thiswe have the other person which will follow this path in the end it will be getting distributed and finally come out so that switches in the parallel part of this we have talked about this andI also found that we have talked about this kind of heat transfer coefficient and this is just so there is nothing new for the other part is part in the part we have this forthis is the hydraulic diameter already have talked about the hydraulic diameter this is the hydraulic density it is defined as four times the free-flow area divided by the weighted perimeter what is the weighted perimeter weighted perimeter is this surface area and this perimeter so where the fluid is coming in contact with to the surface as well as it is coming to this circus so this is where it is waiting the perimeter and that we have to take into account so this is the inner diameter is sorry this is the outer diameter of the Inn at 5 and this is the inner diameter of the outer 5 so it is connecting with the outer diameter of the unified and inner diameter of them after 5 so this is what is the weighted perimeter and this is the definition we are family a bit for the hydraulic diameter now we have another diameter shares which is defined in terms of the heat transfer perimeter and if we call it as hydraulic equivalent diameter thisprobably transport is occurring in terms of only through this area because we have the inner fruit going through this team and the fluid flowing and the annular space and other through it so the heat transfer is taking place through this surface and that is related to buy a jio SIM video is the external diameter of the inactive and we define the equivalent diameter by the four times the Netflix elyria it remains the same this is the net free flow area and this has two part two discussed party is basically the Netflix no idea / the picture of the perimeter and the sound will be getting the feeling that this will be coming except that we have to use this calculation let me know Florida still defined by re-listen 2300 and when we have this is this is this is this is this should be there now did she wrote by t.i. as this ratio is infusing we have enough I mean massive public responding to the unit isn't as your last number called the external source in part because we will be let me know inif you look at the other floor easy that is the travelling Flores in we have the same correlations which we have set for the turbulent flow in the in for the inner tube can also be applied for the annular space but this is another heat transfer correlation which is in which can be used either for the inner tube valve for the annular space with appropriate hydraulic diameter and height is related to the friction factor given by this 1.5 l Audi S4 so we will make use of these correlations while solving the numerical problem so this only problem with the flow rate of 500 hours is heated up from 20 to 35 degrees centigrade by hot water at 1:40 to get tickets and there is 15 degree temperature drop allowed with the water and we have 3.5 m helping of 3 inch by 2 inch so by saying this one we have specified the outer diameter and also we have specified the inner diameter look we have been given the inner diameter 40 and ID book so it is a counterflow double fitted and pints is connected in series so this is important and so now we know that we have hot water and is having the cold water and 15 the exchange is insulated so there is no external cake and we need to calculate the number of sostill possible but we need to find out is the average temperature of the water so here we find out. The different we have been given I’ve been told about the mass flow rate of the cold water we know the floor of the temperature difference so what has not been told is the flow rate of the first wait so let us try to calculate the flow rate of the fluid and this can be done by an hcph delta t h is equals to MC dot CPC we have been told aboutdata TC so already we have all the properties know so we can come there calculate the average dog and this will come out to be 1.36 Casey park second so CP is taken as of the cold water it has been taken as 4.179 joule per kg Kelvin and we have also taken this is at the paarl temperature of 27.5 degree c this is an average temperature between 20 and 35 so we know that cold water is entering at 22 to say and it is living at 35 PVC so24 27.5 is the average temperature of the corporate and at the temperature we have evaluated the CPC so the city is also known in that equation we have used and this is how we know the heart rate must clear it so if we know the 8:30 or 8 then we can try to calculate first of all the in the velocity and all we can also pick the sea the mass flow rate / the free flow area and then we can apply this relationship eh by me to calculate the Reynolds number or we can also try to find out the velocity bye I’m not by no AC so here if it is for the heart rate it will be doing a c and you can find out it to be safe .673 metre per second so onceUT by image dog so this will come out 19343 so this is just a thing but the real number of diploid the hospital so it is going through this number it is much more than 2300 and obviously can understand that so we have to use the tablet number I’m in trouble and formulations and as a suspect that we will be using the number at the temperature at this is a 2 into r e to the power this is temperature on this earth is related to 1.58 into Ellen of r d – 3.28 this andinto 10 to the power – 3 and this value will be substituted to that idea equation when we know if we know ADI we know here and we’ll be able to find out this message not sent this message number any rupee is equals to 370accordingly we can find out the situation after I already know so we can find out thethen you have to use the appropriate correlation they can use this correlation but we may have two depending on whether we are calculating the friction factor of the heart is called the friction factor of the number or the heat transfer we have to use either hydraulic diameter or the equivalent diameter so let us just trying to fight depending on whether we’re calculating the friction factor of the heart is called the friction factor of the numberplay the sprint store trying to find out the fruit properties as we have said that from the cold fluid we know that the average temperature is for the Kool-Aid the average temperature is 27.5 degrees centigrade and enter temperature we have the recalls to 996.4 kg per metre cube and we also have k is equals to .609 what bird made at Kilburn then we have CP is equals to 4.179 joule per kg Kelvin then we have PR equals to 5.77 so as the temperature has reduced now we have the higher value of the product number and we have the music is 28.4 1 into 10 to the power – 6 Pascal second so we havespontaneous stop all we need to find out the velocity how do you will find out the velocity so we calculate we know the mass flow rate and then we find out the AC and what is that AC the AC is just nothing but trees this free Florida addresses the cross-sectional area and we can find out this one bye bye bye for this is the inner diameter of the outer 1 and this is the outer diameter 20 of the inner tube so we will use those two parameters we know already sold we’re all squared – 0 squared so this is the floor areafind out the velocity of the operators to 9 metre per second and the hydraulic diameter the hydraulic diameter can be calculated as how is the hydraulic diameter 4 times that free-flowing does just now we have calculated and that speed of blue which is nothing but my teacher up last year and we have 4 x 4 by by d squared t.i. square – 3 Square by 4 this is fine so download so we know the hydraulic diameter we know the myoptions123 far this one and by the way so this comes out to be 1500 021 so this is also more than 2300 so we have purple and fluorescein so we can use the correlation just now we have given so that is equals to a new be related to the same ey20d into 3 lbs etc so from there if you put these valuable find that if by two is coming to be 3.51 into 10 to the power – 3 and that message number at thenow the role of Valentine is coming into picture so the equivalent diameter would be able to calculate it STI Square – 20 square / 0 and this will come out to be 0403 matter if you put on the face so accordingly we will/ DC from here this will come out to be 1345 watt per metre square so once we know the external transfer coefficient we also know the internal heat transfer coefficient. So now you should be able to find out the overall heat transfer coefficient and then we can calculate the heat exchanger surface area. Thank you