Heat Pipes and Heat Pipe Heat Exchangers – Part 4





Welcome everyone if you recall, we were halfway in between the modeling a of a heat piepe we have taken conventional heat pipe constructor constant cross-sectional area constant cross-sectional area with a circular cross-section and where the liquid returned from the condenser to the evaporator is supported by capillary structure for wick. That kind of heat pipe was developed at the beginning and so far most of the heat pipes we use are of that kind of different variations and if you recall that we have adopted network analysis for the design of this kind of very innovative and intelligent kind of and for suchand decree declare when we have just started describing and last lecture I have told that before alarmingly predict what the fluid flow inside the midwife has to be under a continuing with this what I will do I will go back to our previous last night of the PDF previously this life networkugly start transferring heat and evaporation evaporation of the fluid in the week will start and then this paper will flow and it will be weakened and subsections so here it is being extracted to hear it will get into liquid state and that liquid state will return to the weak structures to be should we continue this is ok liquid paperfloor and circulatory floor and not only that involves two types of fruits one is a gas or vapour another kind of show this I have told again I will repay that here we can see him in his carseat for Cummins falls where is the pressure difference between liquid and this minusca minusca is not uniform also there is a change in the meniscus serve in the US election should the water pressureand then this side we have gone through this length is the Independent dimensionand on the other side we have seen how depression Harry’s along the way and how did they show that is a long delay that we want to see both for the liquid and 4304 what I have shown that the vapour pressure it starts with a high value at the evaporator or at the beginning of the operator and then it falls it falls and it comes to some sort of a minimum value at the end of the idea billing section showprediction what will happen in the condensation gradual condensation of the perfect place florette videos so we will have some sort of pressure rise many people call it pressure recover so there will be some sort of a pressure recovery and at the end of the evaporator condenser the pressure will be somewhere okthis is kind of thick then we we had liquid is getting form from the bank or transform from the paper in the evil condensa condensation liquid and then the condensate floors two through the week structure and then we have to understand that there is not much change of the liquid volume liquid being incompressible paper is compressible vapour density is also less but the liquid density is not that list so liquid mass flow rate there is like change but after that the volume flow rate does not change so for the liquid this blue line if we see that there will be continuous fall in pressure as it moves from the condenser into your curator because they are all this but I have told that we assume that there is nowhat we can see that there is some sort of inlet pressure cake for the paper says and there is pressure drop for the liquid phase and if the circulation has to be thinking balance and then only we will have circulation this is what we get from our free flow consideration of the fluid flow we can understand what is taking place now if we move to the next slide next life means we have to go here sweetie model to develop the fluidic model the following assumptions are made class is one-dimensional liquid is incompressible where is represented by the ideal gas equation and the vapour compression and expansion Spotify strictly in the evaporator and condenser is constant in the week adiabatic section we have constantly because this addiction take a very major role in the pressure drop of the liquid and liquid temperature is equal to the week temperature in each 856 this is what we have also assumed earlier that the week structure and the liquid they are at thermal equilibrium at nex let us move forward model model modelwe have shown that there are two paper 1 paper tank is there in the weight restriction one paper tank is there any construction super goals from one tank to another in the construction work is there so there is getting transform into liquid and that goes to a liquid tank situated in liquid flows to another which is situated and the liquid goes to the vapour tank transformation process model and the connection is cool down a mass of weed in that condenser is condensed and flows into the condenser liquid time for the week capillary pressure pushes the mass of liquid m0l from the condenser liquid tank for back to evaporate a liquid tank 12 show for tanks for the paper inside the tank is modelled as an ideal gas this is what he told earlier and we will follow that the continuity equation that is we will get this kind of a continuity equation show actually you see thethat is the pressure of the different evaporated section and bby is the volume of the vehicle and evaporated section is the gas constant and gamma is city by that is the ratio of the specific it’s so shity by city and this quantity this is equal to what in the evaporator – in that paper so which is going out this means that means let us if we go to thewe are doing some sort of a transient analysis if we do not do the transient analysis that whatever him that if he is coming that will be aimed at me but if we are considering transient analysis there some sort of EPA regulation can be done in this paper tank which is ranked number two so this is what we have read to me in the next life in the next like if we see that I’m not be a that is entering the tank and I’m not be that is going out and then we can write some sort of an equation like this and then we can simplify the equation something like this cve it is kind of a capacitance weekend right for the condenser also similar recreation I do not likeconsidering the adiabatic polytropic process relation between pressure and temperature is outside so we assumed that idea better quality audit process is taking place when there is an expansion or there is a change in temperature show the change in temperature with time we can get with this kind of equation with this if we go to the next level then how we get that how much mass is coming to the evaporated tank so I’m not even that is Q’s RTV 18 / similarly-named condenser that is whatever is the heat / Clayton and then they are our dogs which are there is a dark we have conceptualize the dark which is carrying the weapon for that some sort of a pipeline equation with resistance etc thanks we will get thisin the volume whatever liquid mass is there that we can get how this is the role density this is the porosity and this is the cross-sectional area and this is a lie that means the cross-sectional area into length that will give us the volume of the week structure x the ferocity that mean give up the volume *I have done separately the analysis of quite a few things I have done with what I have done with food network and then I have separately considered the past I have separately considering between and then ultimately between the network and ok the equation for the line that we have got on here for the other lights should we bring some sort of resistance Kok is an empirical constant for actually liquid line you have to see it is through the porous structure so this is how we can bring then the product key whatever we have got to destroy dick suck it can be represented like this so predict circuit we can see that there are different resistances and then there are other kind of events also so that we can write write down this truly suck it for our conceptual understanding but already have written the latest move to that first to see that coupling between liquid and vapour should coupling between liquid and vapour if we if we think of the evaporator section so this is the this is a very exaggerated way of drawing the operator section so this is the evaporator wall and this is the structure and this is the card interface this is your liquid and this is okay so here we see that we get the car interface and interface show some sort of radius of curvature one can get which is our Alexa this is your car this is your radius that is given by this is nothing but your class equation and one can derive this equation so we will get this relationship between vapour pressure and the liquid pressure they are related by the surface tension of the liquid and the radius of curvature how do you getand the ingredients is it then or she is related to watch and then again we get finally one equation between as the difference between the liquid phase and look at what we have read the previous equation Excel and with a factor of some sort of a correction at the coupling between these and thissalad and fruit thermal coupling know what we can do that q you was gonna tell you I put it aside so that we can determine knowing that what is the week temperature temperature within the week and temperature of the paper Hindi mein puritan and then the resistance sure that will give you some sort of mass flow rate and that is equal to the prom this equation we will get the mass flow rate by this particular formula where HIV is the latent heat of vaporization should the resistance we have to calculate these two actually week temperature can be related to liquid temperature in evaporated liquid and vapour temperature can be related by the by the Young Laplace equation show and the resistance calculation we have mentioned earlier through with all these things we can be able to couple the solid and fraternal solid and free and then this thermal coupling between Frederick and thermal network and different network can be compared to similar situation one can get four tickets with all these things we will be able to close our model close our network so we need of course some small correlation coefficient small number of correlation coefficient is The dimension of the dimension of the five we need the some details regarding the week structure with all these things we will be able to calculatedesign of the fibre analysis can be obtained by from different books in the next class I like to give you some I like to give you mention some books on heat pipe and those books can be referred for getting details if possible I will also give some details of the papers or reference of the papers from there also one can see what is the network analysis show me this way move to important topic but unfortunately dinosaur show today I will not be able to tell this only let me once I have introduced this light let me tell you hear what we want to do we want to see what is the working range of a heat pipe. So there are different limiting phenomena so with these limiting phenomena what is the working range of the heat pipe that we want to see and that we will do in the next class. For the time being I like to thank all of you for your attention, thank you.