Heat Pipes and Heat Pipe Heat Exchangers – Part 1





Hello friends we are studying heat exchangers fundamentals and design analysis, from this lecture we will switch over to a new topic. That is heat pipes and heat pipe heat exchangers. Many of you may be familiar with the word heat pipe by some of you may know how does it work, what is a heat pipe. For the benefit of most of you let me tell you that hit by itself is not a heat exchanger strictly speaking if we take the very common perception regarding a heat exchanger that heat exchanger is a device which facilitate heat transfer between two fluids teams from that definition point of you are from that concept point of you hit by is not itself is not a heat exchanger but she could be a part of a heat exchanger it is a very unique device that’s why we like to spend some time it is a very high very high de fuca device as it exchange of the exchange of thermal energy that’s why I will like to spend some time and with the help of a single 5 or maybe with the help of a number of ways we can have a design of heat exchanger which is a very efficient design of heat exchanger make a call for me at 15 if we go to the next slide his advice or very high thermal conductance that's what I have told that it was a very efficient device or exchanging thermal energy in the Blackhawks how it is doing this exchange of thermal energy that will be late but if we see the heateras a black but then we can do in that pipe is a device of a very high thermal conductance now the heat pipe is not new for long it might have been advocated all the design of 5 has been proposed by people the first suggestion came from Bangalore in 1942 but serious support for developing these devices starting from the Independent researcher independence innovation in there by 16 and from then on we will have different kind of design and today is 5 in the very established technology and it converts very large range of temperature starting from the cryogenic range of temperature to the temperature of several cows having more than 1000 degree Celsius or the liquid metal rain so we will have his wife different designs design and regarding the range wide range of education we will ask later but now we can understand the working principle of working principlephone to transfer transfer will be responsible for part of this week and at least I found that means the gravity that will assist the part of the food and there will be a transfer of thermal energy that is that is in a sense is what a thermosyphon can do and we will see how does it help in gravity that is what I havethe trend has to return to evaporate quickly here in a moment what is evaporated why the flu has to return to Liverpool tonight gravity plays a very important role in that gravity gravity gravity sensing returning the liquid from returning the liquid from the connection to the protection they are for the evaporator has to be at the bottom part of this device contacts to this is another important thing that design is such that the operator will be at the bottom part of it without knowingI have seen it happen any application your application and maybe in a room that is how we can do it we can do it with the help of energy we know that there is a lack of transferring heat from belowyou see this is basically it is having a tubular structure and generally it is evaporated and then there is a little bit of liquid working through it which we are calling or wanting to eat in this heat pipe so basically it’s a long cylindrical container son sleeping with liquid then it is evacuated and again sale and then the liquid due to gravity it will the lower part of BST device which is thermosyphon and then if we transfer him at this point so quickly try to start being lied to and it is becoming it is it is having a low density between try to fill this space and it will go to the top portion and we can remember that it willwhat place do to the assistance of gravity which will run continuously without needing any kind of power from anywhere only thing is that there is a temperature difference and the temperature difference is creating the fluid flow and when there is a free flow and face change the way I have to both operation and condensation should there be a transfer of heat from the high temperature today temperature what is it and there could be life outside of the slide I have been having some kindand the other part is occupied by the low-temperature fruit so this is basically sometimes for some type of circulation low and this is how we can transferbeef operate at the very least temperature difference that means that there could be a good amount of heat transfer the temperature difference between the heart and and cold and need not be very hard to be facing heat transfer is involved and admin office in the transfer is very efficient so this will have a very efficient way of transferring heat requiring very small amount of data that is the first feature which is a very desirable feature for any heat exchanger to be incorporated in which we have to know that thethe high temperature in is at the bottom of the temperature is at the top of the tank because we had to explain gravity for return of the fluid from the low temperature in high point this is this is one limitation of operation for this philosophy degree now let us go to the next light historical development of it came from the design ofthat limitation is that limitation is removed in case of a hit by design show an improvised design thermosyphon gives his bike so that is the first point and then second point if we like to see the basic hit 5 differs from the thermosyphon in that the former contents a week that means the heat file contains a week week week is nothing but a capillary structure which is a common reference to this capillary structure and details the return of the working fluid from the condensate section to evaporate so if we return of the fluid from the condenser exception to the operative section we do not need the the the the existence of gravity and then this particular orientation of thermosyphon is not essential that means always be her side will be at the park at the bottom and the cool side will be at the door so this kind of limitations of this kind of restriction will not be thereit is not required to return the free same thing I have done that evaporated need not be at the lowest position of the device this gives substantial flexibility of operation and it also makes the design on backwhen did two devices theoretically we can have it on my phone but can be used in a solar collector that with the storage device are so they can also work on the basis of time but the thing is not but whenever we design ofon the left-hand side I have simethicone side that we have bought a container light construction it could be in a simplest form it could be a cylinder closed at both the lowest point we have got some liquid which is known as working through it and the lowest point there is heating food we call it evaporated section and then5:23 and then at the top most part we have got the condenser show from the condenser concentration will take place at the condensate field will come back to the evaporator this this will continue as long as there is a small temperature difference between the hottest and coldest of the top side and the fact that the bottom side and bottom end and the top end of the no heat transfer factor in plants but it has to be in this kind of orientation butb option or 8:30 at the higher elevation and the cold part of the heat pipe at a lower elevation there is no because they're in their nestwhich actions are explained in capillary action do which is known to many of you for the sake of completeness and the benefit of all the participants let us take some time to do this which structure what is the what is the purpose of the week is something like this let’s say we have got 6 week is something like this let’s say we have got aand at the top we have got the flu so we all had to come to this point they're not how it is done there is a week which is better Alexa copy and then the continuously there will be flow of oil from the low point I mean from a lower elevation to hire this is the audience so actually what is happening is like this that if we have a very narrow tube let’s say it is a tube of solid materials and then we did so these teams are called capillary tube means that you should only for a day in a liquid what we will find the liquid will rise up to certain level so this is the liquid 2 height age it is defying Gravity because against the force of gravity there is a nice of liquid how does it take place many of you know it from your high school physics but if we try to explain it little bit so if we draw an exaggerated diagram the meniscus of the liquid is something like this and hear a force work which is your self-esteem some food and we denoted by sigma so sigma what’s along the periphery of the meniscus and there is a small angle you can see this is Tina so you can see that the horizontal component of the surface tension that we cancel because also the periphery theory substantial component that will add up physical component to Adam show in the particle direction there is a force and this force is the capillary force and it is drawing the or it is doing the liquid India election so if it is pulling the other one direction show in general is this that very very easy and let’s say this is your face one sigma one and two sigma one by whereor approximately one in 2G into age do things are very important that surface tension that should be fine to get a higher value of h and sorry and RR should be smallwhich are there in the cotton seed that gives the capillary kind of construction and we can raise thewhich is taken away by the brutal and continuously corporation tax place so this flu can be maintained in a oil lamp continuously oil is being bad so the floor is made otherwise if we have only is static lice to this is what is very important and this is how the liquid return what’s in kck shop-in-shop hit 50 we have got a capillary structure with this I will again go back to Indy todayis probable mechanism is required for the return of the condenser liquid from the condenser to the evaporator coil capillary structure is most commonly used in Dubai we do not want gravity to be responsible for this return of liquid from the condenser to the evaporator because we had limitations regarding the orientation of the fight that we do not want so that’s what we like to do that we want to have another charity is one mechanism providing capillary structure is one of the mechanism by which this can be done and calmly this is done by providing structure but there could be other methods also should hear some of the methods are giving now due to shortage of time I will not be able to show all these methods some of the method maybe we will show but whoever is interested you can see Gravity falls gravity that is purple so basically one can say thatto have a particular for orientation of the tablet which is most common that’s why I like to book some sort of it so it is written mechanism and standard by Luke hit by its cetera are standard pipe and look at 5 etc are based on this one then we can use the centripetal force rotating it by there are certain devices routed to the hospital and buy that also liquid can be returned or taken back to the operator electricthis one I said why magnetic field or magnetic properties are there so that can also be used as your return is magnetic forcethe mechanism which I have describe or which I have named unfortunately all of them cannot be explained in detail only here if you are interested you can see it from the data from some suitable source but obviously the calculator ti is the main mechanism and we will spend some time on this category device how does it provide the return path for the liquid and the analysis also we will try to do involving a capillary structure or wick structure. So that is what we’re going to do in this particular course, so we have to know its performance and the working principle but today this much is for the introduction to the heat pipe and thank you.