Delovanje toplotnih cevi

Žiber, Ylenia (author), Čopar, Simon (mentor), Lapuh, Rok (comentor)

Toplotne cevi se že vrsto let uporabljajo za hlajenje različnih komponent. Njihova glavna lastnost je izkoriščanje faznih sprememb za boljši prenos toplote med dvema točkama. Ta način odvajanja toplote ima kot glavno prednost pasivnost. Ob dovolj veliki temperaturni razliki med koncema cevi začne sistem delovati in toplota na vročem delu se prenese na hladen del. Toplotna cev je razdeljena na tri dele, na kondenzacijski del, na adiabatni del in na uparjalni del. Uparjalnik se postavi na vir toplote in preko kondenzatorja se toplota odvede na hladilna rebra ali v primeru vodnega hlajenja, na vodo. Zastavila sem si vprašanje ali lahko toplotne cevi odvajajo nekaj kW moči in kako so pri tem omejene. Preko teoretičnih osnov bom razložila njihovo delovanje in omejitve. Z analizo literature sem dodatno želela raziskati smiselnost uporabe toplotnih cevi na ultralahkih letalih. Posebno okolje kot je letenje v ozračju nam daje dodatne omejitve pri obravnavi toplotnih cevi, kot so nagibi toplotne cevi, smer letala glede na gravitacijo in prostorska omejenost. Komentirala bom tudi smiselnost uporabe toplotnih cevi za hlajenje baterij električnih vozil. Toplotne cevi so omejene z zunanjimi pogoji, predvsem na temperaturo. Na ultralahkih letalih moramo biti pozorni na temperaturne omejitve komponent. Pri delovanju toplotnih cevi se ne moremo zanesti na pomoč gravitacije, saj se lahko orientacija letala med letom zelo spreminja. Mogoče je izdelati toplotno cev, ki lahko odvaja nekaj kW toplote, ampak so za to potrebne tekoče alkalijske kovine, ki pa so neprimerne za vsakdanjo uporabo. Take toplotne cevi bi bile tudi dimenzijsko prevelike za omejene prostore na ultralahkih letalih. Namesto ene toplotne cevi za velike moči bi se lahko uporabilo več toplotnih cevi za nižje moči. Izračunala sem, da bi bil tak sistem hlajenja masno in prostorsko potraten v primeru moči 8 kW. Ugotovila sem, da toplotne cevi niso dovolj učinkovit način hlajenja v primeru velikih moči velikostnega reda nekaj kW. Toplotne cevi lahko toploto iz toplega dela na hladni del odvajajo le pri nekaj sto W, kar je primerno za hlajenje manjših elektronskih komponent. Primerne so za pomoč pri hlajenju baterij, saj imajo lahko vlogo vmesne komponente med samo baterijo in aktivnim vodnim hlajenjem.

• Language: Slovenian
• Keywords: toplotne cevi, moči nekaj kW, ultralahka letala
• Work type: Final paper
• Typology: 2.11 - Undergraduate Thesis
• Organization: FMF - Faculty of Mathematics and Physics
• Year: 2020
• PID: 20.500.12556/RUL-118103
• COBISS.SI-ID: 25540355
• Publication date in RUL: 20.08.2020

Secondary language

• Language: English
• Title: Operating of heat pipes

Abstract

Heat pipes have been used for many years to cool various components. Their main feature is utilizing phase changes for better heat transfer between two points. This heat dissipation system has passivity as the main advantage. When the temperature difference between both ends of the pipe is large enough, the heat from the hot part is transferred to the cold part. The heat pipe is divided into three parts: a condenser, an adiabatic part and an evaporator. The evaporator is placed on a heat source and the heat is transferred to the condenser. The heat is then transferred to the cooling fins or water, in the case of water cooling. I wanted to find out whether heat pipes can dissipate few kW of power and what are their limits. I explained the operation and its limitations, through the theoretical basis. By analyzing the literature, I wanted to further explore the feasibility of using heat pipes on ultralight aircraft. A special environment such as flying in the atmosphere, gives us additional limitations when dealing with heat pipes. I will also comment on the suitability of heat pipes to cool electric vehicle batteries. Heat pipes are limited by external conditions, especially temperature. On ultralight aircraft, we must pay attention to the temperature limits of the components. When it comes to the way heat pipes operate, we cannot rely upon gravity. The orientation of the aircraft can vary greatly during flight. It is possible to make a heat pipe which can dissipate many kW of heat, but this requires liquid alkali metals, which are unsuitable for everyday use. Such heat pipes would also be too large for confined spaces on ultralight aircraft. Instead of using one heat pipe for high power, several heat pipes for lower power could be used. The calculation showed that in the case of 8 kW power, this cooling system would be wasteful in terms of mass and volume. I discovered that heat pipes are not a sufficiently efficient way of cooling in the case of high power. Heat pipes can dissipate heat from the warm part to the cold part only at a few hundred W, which may be suitable for cooling smaller electronic components. They are suitable for cooling the batteries, as they can act as an intermediate component between the battery itself and the active water cooling.

• Keywords: Heat pipes, heat loads of kW, ultralight aircraft