Report on Working Principle of Heat Pipes

Added on - 28 May 2020

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Running head: HEAT TRANSFERHeat Transfer[Name of the Student][Name of the University][Author note]
HEAT TRANSFER1Table of ContentsIntroduction:...............................................................................................................................2Discussion:.................................................................................................................................3Working principle:.....................................................................................................................3Literature review:.......................................................................................................................7Application of heat pipes:..........................................................................................................9Benefits of heat pipes:..............................................................................................................10Types of heat pipes:.................................................................................................................111. Vapour Chambers:...........................................................................................................112. variable conductance heat pipes:......................................................................................113. Diode heat pipes:..............................................................................................................11Components of heat pipes:.......................................................................................................12Conclusion:..............................................................................................................................14References:...............................................................................................................................15
HEAT TRANSFER2Introduction:Gaugler in the year of 1994 and Trefethen in the year of 1962 were the first twopersons to consider the original idea of “heat pipes”. For the basic presentation of “heatpipes” Gaugler performed a test with a very lightweight heat transfer device. Along with thisless attention was paid to this device at that time when it was considered (Zohuri, 2016).Trefethen was the first person to suggest this in the year of 1962. This was followed by apatent application of this pipes in the year of 1963 by Wyatt. This was not publicized till theyear of 1964 when “George Grove” along with his co-worker at “Los Alamos NationalLaboratory” made an invention regarding the concept which is totally independently. Thiswas done for the space program that is existing right now along with the application of thisprogram. Heat pipes are nothing but a two phase flow device responsible for transferring ofheat. In this device the liquid changes to vapour and again the vapour changes to liquid formand this usually as the liquid or the vapour circulates amongst the evaporator and thecondenser which is having a high effective “thermal conductivity” (Orr et al., 2014). Thisdevice has a high heat transport capacity. The heat pipes makes a combination of both theprinciples of “thermal conductivity” along with the “phase transition” for the purpose oftransferring the heat in an effective manner. This report mainly discusses about the workingprinciple of heat pipes. Along with this the report also discusses about the variouscomponents of heat pipe and the design as well.Discussion:Working principle:The heat pipes are responsible for employing the evaporative cooling for the purposeof transferring the “thermal energy” from a point to another point by means of “evaporation”
HEAT TRANSFER3and “condensation” of the fluid that works as a cooling fluid. The existence of the differencein the temperature between the two ends of the pipe are mainly responsible the working of theheat pipes. This means when a specific end of the pipe heats up the cooling fluid presentinside the pipe then the fluid gets evaporated at the end along with increasing the pressure ofthe vapour that is present inside the heat pipe’s cavity (Fu et al. 2012). The vaporisationabsorbs the “latent heat of evaporation” of the working fluid and associated with this is thereduction in the pipes end temperature. The vapour pressure is much higher than that of thevapour which is at equilibrium. This vapour pressure is present over the hot working fluidand is mainly present at the end of the pipes. This is also higher over the condensing workingfluid that is present al the cooler ends of the pipe. The difference of the pressure is the mainreason for driving of the mass transfer at a rapid rate towards the end where the condensationtake place. At this the excess vapour condenses which is associated by the releasing of thelatent heat along with warming up the cool part of the pipe (Tran et al., 2014). The gas that donot condense is responsible for impeding of the flow of gas. Due to this reason theeffectiveness of the heat pipes is also reduced and this happens only at particular lowtemperature where the pressure of the vapour is also low. The molecules present in the gas ishaving a speed almost similar to that of sound. And for cases of gases that does not condense,this is the upper speed limit of the molecules in the heat pipe but in general case the vapourspeed gets limited by the rate at which condensation occurs at the cold end of the pipe. This isvery much lower than the speed of the molecules. (Choi et al., 2012). This happens when thesurface for condensation is cold. The evaporation from the surface is nearly negligible if thedifference in the temperature is more than 10 degrees. This can be accessed from the curvesof the vapour pressure. It becomes very much challenging when the efficient heat transportthrough the gas takes place. The main challenge is to maintain a sufficient temperaturebetween the condensing surface and the gas. Along with this the differences in the
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