Loop heat pipe with multiple evaporators has the advantage of design flexibility for the cooling systems of many heating devices and it has been used for spacecraft applications 3, 4. A heat pipe is a copper tube with an internal wick structure that is sealed on both ends with a small amount of water inside. Cbeccres simulation as a rating tool, not a forecasting tool time dependent valuation tdv different price of electricity every hour of year based on puc cost model. Loop heat pipes with a flat evaporator a loop heat pipe lhp is a twophase heat transfer device that uses capillary action to remove heat from a high temperature source and transfers heat to a condenser, where the heat is removed by other cooling methods.
Figures 6 and 7 are photo illustrations of these heat pipe clamps as a separate assembly and as installed in the spacecraft. Heat up the heating end of the heat pipe emperature 700c and dissipate 5 6. Lancaster, pennsylvania 17601 steven m geng national aeronautics and space administration glenn research center cleveland, ohio 445 jon zuo advanced cooling teclmologies, inc. Introduction a typical heat pipe consists of a sealed pipe or tube made of a material that is compatible with the working fluid such as copper for water heat pipes, or aluminium for ammonia heat pipes. The amount of heat transfer decrease depends on the particular heat. The paper presents an overview of heat pipes, especially those used in different space missions. Steady state model of a loop heat pipe lhp with coherent. Test cell for a novel planar mems loop heat pipe based on. The evaporator and condenser sections are 360 mm and 280 mm respectively. Loop heat pipe with coherent porous wick since the porous material used for current heat pipes is usually stochastic structure, it is hard to apply analytical or numerical methods for design optimization. The loop heat pipe for ams02 politecnico di milano.
The figures below illustrate the operating principles of a typical loop heat pipe. Also, chandratilleke et al 2 showed that the loop heat pipe was able to transport at least 10 times the amount of heat as compared to a solid copper rod of the same size. A working fluid is encapsulated inside this closed loop as a coolant. A loop heat pipe lhp is a highly efficient heattransfer device operating on a closed evaporationcondensation cycle and using the capillary mechanism for pumping the working fluid. Several factors have contributed to the science and technology of the present stateofart heat pipe leading to the development of loop heat pipes, micro and miniature heat pipes and micro loop heat pipes. Loop heat pipe cooling mechanism for high power led was demonstrated by lu, hua, liu and cheng 9. Kaya and goldak 5 reported the boiling limit of loop heat pipe obtained. Looped heat pipes lhps are twophase heat transfer devices that employ the same capillary pumping of a working fluid as used in conventional heat pipes. The radiator is divided in 176 thermal nodes having temperaturevarying capacitances. The abi infrared detectors need to be cold to accurately measure the thermal energy radiated from the earths atmosphere.
Understanding loop heat pipes advanced thermal solutions. They can transport a large heat load over a long distance with a small. A loop heat pipe is a heattransfer device that consists of an evaporator that absorbs heat from the heat source and a condenser that dissipates that heat away, with the two components connected by pipes into a loop figure 1. Pe pipe is heat butt or socket fused with appropriate fittings using a fusion tool. Residential water heating energy in californias title 24. Over the years, researchers have continuously search new methods of heat transfer augmentation. Pb pipe is fused together with appropriate fittings using a fusion tool. Test cell for a novel planar mems loop heat pipe based on coherent porous silicon debra cytrynowicz 1, mohammed hamdan 2, praveen medis 1 h. The flow and heat transfer behaviour of a thermosyphontype heat pipe loop may be theoretically simulated by dividing the loop into a series of control volumes and applying the equations of change, namely mass, motion and energy, to each control volume and making use of say. Heat pipes heat transport limit for proper heat pipe operation, the total pressure drop must not exceed its capillary pressure head. How to model a heat pipe heat transfer and fluid flow.
All heat pipes have a temperature range over which they have the best performance. Copper fin with fan, cooling length 6080mm t heater. Heatpipe zonnecollector thermic 723 installatiegemak hoog. Beginning with a definition of the problem, including the temperature. Loop heat pipes lhps are passive, twophase heat transport devices. High performance loop heat pipe esas artes programmes. They possess all the main advantages of conventional heat pipes, but owing to the original design and special properties of the capillary structure are capable of transferring heat efficiency for distances up to several meters at any orientation in the gravity field, or to several tens of. Energy equation for the jth vapor plug in this model, the temperature is uniform within the. The heat transfer coefficient in microgravity is 50% less than the correspondent in normal gravity when the flow pattern is bubbly or slug. Lhps can transfer heat efficiently up to several meters at any orientation in the gravity field. Heat transfer in curved pipes christian carlsson may 2014 1 introduction heat transfer in pipes has important applications in many areas, such as for e. You can also choose from batch ics passive, thermosyphon passive loop heat pipe, as well as from indirect closed loop active, direct open loop active loop heat pipe, and whether. Heat pipes are referred to as the superconductors of heatdue to their fast transfer capability with low heat loss.
This is a man made method and is an increasingly important technical solution to heat transfer. Heat loops known as loop heat pipes, capillary pumped loops, mechanically driven loops, twophase loops, hybrid loops, etc. Remote fin stacks heat exchangers are a perfect example as with any heat pipe heat sink design, size the heat pipe with an additional 25% thermal headroom if youre interested in spreading heat to reduce hot spot andor attach to a local heat exchanger the ratio of heat spreader to heat source should be on the order of 20. The technology was invented in the former soviet union in the 1980s for spacecraft thermal control. Phd dissertation rotating heat pipe assisted annealing metin celik 2020. Ats engineering ebook advanced thermal solutions, inc. Qmax customer requirement then heat pipe is passed test frequency.
Choosing a backup generator plus 3 legal house connection options transfer switch and more duration. Cleanliness during installation, keep trash, soil, and small animals out of the pipe. Rotating heat pipe assisted annealing tu delft research. Heat pipes, 6th edition, takes a highly practical approach to the design and selection of heat pipes, making it an essential guide for practicing engineers and an ideal text for postgraduate students. A loop heat pipe with coherent pores integrated to the heat source is considered as a calculation model in this paperfig. They are often referred to as the superconductors of heat as they possess an extra ordinary heat transfer capacity and rate with almost no heat loss. Loop heat pipes lhps are twophase heattransfer devices with capillary pumping of a working fluid. Internal diameter of the php tube, input heat flux to the device. Historical perspectives, principles of operations, types of heat pipes are discussed. It is a twophase heat transfer device that utilizes the evaporation and condensation of a working fluid to transfer heat, and the capillary forces developed in fine porous wicks to circulate the fluid. Pdf the present paper proposes general equations for predicting the steady state. It is comprised of an evaporator section, a condenser section and a short adiabatic section connecting the two.
Pdf analytical model for characterization of loop heat pipes. Leave the ends of the ground loop pipe taped until t he. Stenger in 1966 2 first developed the technique of capillary pumped loop cpl in heat pipe and maydanik et al. With heat needing to be transported over a longer distance, and because the working fluid circulation in a heat pipe is directly proportional to the surface tension coefficient and inversely proportional to the effective pore radius of the wick, a different system for heat transport was required when the evaporator was above the condenser. As well as convection, conduction and radiation there is another method of transferring heat energy. The heat pipe is a twophase cooling solution, offering very high thermal coefficients. Water heat pipe parameters and limitations when to use. Loop heat pipe performance enhancement using primary wick with circumferential grooves. The most commonly encountered operating limit in a conventional heat pipe is the capillary limit. A heat pipe is a passive heat transfer device that can transfer a very large amount of heat over short distances with a small temperature difference between the heat source and heat sink.
The loop heat pipe lhp was invented in russia in the early 1980s. An overview of long duration sodium heat pipe tests john h. Gerner 2, eric golliher 3 1center for microelectronic sensors and mems, department of e lectrical computer engineering and computer science, university of cincinnati,cincinnati, ohio, 45221. Loop heat pipes with flat evaporators sciencedirect. This simplified model has been validated for each loopheatpipe operating mode for various geometries and operating conditions. A loop heat pipe model was built with the following mesh characteristics. Improvements have been done over time in heat pipes used for heat transfer.
Experimental analysis on thermal performance ofclosed. Analysis of heat transfer and flow patterns in a loop heat pipe. The total length of the closed loop pulsating heat pipe is 1080 mm. Copper dummy heater, heat source area 15x w mm condenser. The experiments are conducted on vertical orientations for different heat loads varying from 10 w to 100 w in steps of 10 w. A loop heat pipe lhp is a twophase heat transfer device that uses capillary action to remove heat from a source and passively move it to a condenser or radiator. Zonneboilerset met tapwaterboiler en heatpipe collector technea. Evaporator temperature of heat pipe, measurement on. Journals pdf frontiers in heat pipes fhp flow regime. This new edition has been revised to include new information on the underlying theory of heat pipes and heat transfer, and features fully updated applications, new data sections, and updated. Loop heat pipe design flexible heating pipe tech two. The result is less pumping of the wick with reduced heat transfer.
Pcbs with multiple hot spots, cooled by flat miniature heat pipes, and the. This part introduces components and phenomena, the next 3 parts describe modeling techniques in thermal desktop and flocad. Posted on august 4, 2014 by becca leonard leave a comment. Various works on the heat transfer performance of loop heat pipes have been reported. Deze thermic heatpipe zonnecollector rk723 heeft een 3laags absorber en daardoor een zeer hoge opbrengst.
This method has been used in the aerospace industry for about thr ee decades for supporting systemlevel design analysis. Factor affecting closed loop pulsating heat pipe it can be seen that six major thermomechanical parameters have emerged as the primary design parameters affecting the php system dynamics. A heat pipe is simply a type of heat exchanger that is very simple in construction, easy and straight forward for use. The loop heat pipe is a thermal device, which carry heat owing to latent heat of vaporisation, from the hot dissipative equipment to the cold external radiator. The thermal performance of this complete highpower coupling of transmitter transisfigure 4 ao40 heat pipe extrusion cross section. Development of sintered nicu wicks for loop heat pipes. A heat pipe is a simple device that can quickly transfer heat from one point to another. In that case a parameter that cut 50% heat transfer coefficients value can be imposed. A wide variety of loop heat pipe options are available to you, such as split. An overview of long duration sodium heat pipe tests. Goes17 loop heat pipe fact sheet role of the advanced baseline imager abi loop heat pipe loop heat pipes keep the abi at the correct operating temperatures.
Heater temperature, sensor is embedded between heater and evaporator section of heat pipe. Variable conductance heat pipe, rotating heat pipe, loop heat pipe, micro heat pipe, nanofluids 1. In order to insure optimal operation of sensitive electronic devices in space, it is essential to have a dependable thermal control system to regulate. Miniature multiple evaporator multiple condenser loop heat pipe. The value of the heat transfer between the wall and fluid is calculated based on forced convection heat transfer in the circular pipe.
The graph also shows that if the heat pipe is operated against the force of gravity, the liquid undergoes a larger pressure drop. The main part of an lhp is an evaporator, which contains a capillary structure wick and acts as a capillary pump and an evaporative heat exchanger. Installation instructions ground coupled loop system. Thermic zonneboiler set met tapwaterboiler en heatpipe collector isdesubsidie 120 500 liter installatiegemak weinig onderhoud. Uses statecertified, free, open source energy modeling software. Experimental analysis of heat transfer behavior inside. This device, totally passive no mechanical pump, use a capillary evaporator which provides a two phase flow owing to capillary suction. Project description by means of knowledge about the theory of heat pipes, one is now able to carry out a basic calculation of a heat pipe. Heat transfer and flow analysis in loop heat pipe with. A heat pipe heat exchanger is a simple device which ismade use of to transfer heat from one location to another,using an evaporationcondensation cycle. Mathematical modeling and experimental validation of. To improve this type of equipment, a good understanding is needed of the relation. How to model a heat pipe a brief explanation is provided of a networkbased method that is suitable for modeling constant conductance heat pipes cchps, also called fixed conductance heat pipes or fchps and vapor chamber fins.
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