Theoretical investigation of the thermal performance of a. At present, my loop only has a chiller, a variable speed pump and two air handlers in parallel, whereby it appears as though the inlet nodes to the air handlers act as twoway valves. The main parts include a wick, a heater block, an accumulator, 2m long copper wire and a condenser. Design and manufacturing of loop heat pipes for electronics cooling. Experimental study on a hybrid loop heat pipe matec web of. Pdf the present paper proposes general equations for predicting the steadystate behavior of a loop heat pipe, linking its. A multiturn php is a thermohydrodynamic genesis of a reverse thermosyphon without control valve, a bubble pump and a twophase loop 11. Heat pipe science and technology, an international journal is encompassed on publishing i fundamental studies of heat and mass transfer in heat pipes and twophase thermosyphons, ii new streams of technology development, iii industrial innovation in electronic thermal control, air conditioning, heating and cooling, aerospace thermal control. 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. Development of a flexible loop heat pipe cold plate 951436 the current trend in military avionics design is to physically move electronics closer to the components they control.
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 experiments are conducted on vertical orientations for different heat loads varying from 10 w to 100 w in steps of 10 w. The paper presents an overview of heat pipes, especially those used in different space missions. The present model could be a useful tool for the design of loop heat pipes. A loop heat pipe is a two phase liquidvapor flow heat transfer device that utilizes evaporation and condensation of a working fluid to transfer heat, and the capillary forces developed in the fine porous wicks to circulate the fluid. The loop heat pipe is composed of evaporator, reservoir, capillary wick, vaporliquid line, and condenser. Loop heat pipes lhps are highly efficient twophase heat transfer devices with the ability to transport significant amounts of heat over long distances.
However, in an actual application when a heat pipe is soldered or epoxied to the base of a heat sink, the effective thermal conductivity of the heat pipe may be. The figures below illustrate the operating principles of a typical loop heat pipe. 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. The loop heat pipe is composed of evaporator, reservoir, capillary wick, vapor liquid line, and condenser. The loop heat pipe for ams02 politecnico di milano. Various works on the heat transfer performance of loop heat pipes have been reported. Heat transfer and flow analysis in loop heat pipe with. Loop field pt ports source water in source water out gshp notes.
Taco radiant made easy application guide technical. In assembling a fairly detailed openstudioenergyplus model of a building, i realized i may need to more accurately model the chilled water loop. This saves on weight, increases component maintainability, reduces aircraft manufacturing costs, and reduces the amount of electromagnetic shielding. Pipe sizing sizing steam and condensate pipes pressure loss, recommended velocity, capacity and more. 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. Thinner loop heat pipe this loop heat pipe uses copper sheets that are only 0. The capability to smoothlycontinuously transport heat the proper operation for different heat loads. Heat pipes do not actually dissipate the heat to the environment, but serve to move heat efficiently within a thermal system. 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. How not to model a heat pipe a common trick is to model a heat pipe as a bar of highly conductive material. By combining radial and axial heat leak, the total heat leak is written as.
Pdf the present paper proposes general equations for predicting the steady state behavior of a loop heat pipe, linking its. A loop heat pipe lhp is a twophase heat transfer device that uses the latent heat of. The present study has shown that, using a special heat dissipation technology loop heat pipe, the highpower led lighting luminaire with input power from 36 to 150w for outdoor and indoor. Beginning with a definition of the problem, including the temperature. 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. Spirax sarco heat pipe heat exchanger cgi animation. Loop sizes are taken to the nearest half foot on the height and width. A loop heat pipe lhp is a passive, two phase heat transfer device comprising a porous membrane in its evaporator. The loop heat pipe lhp was invented in russia in the early 1980s. Operation characteristics of a newtype loop heat pipe lhp with wick separated from heating surface in the evaporator. Lowcost manufacturing of loop heat pipe for commercial. 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. Development of a flexible loop heat pipe cold plate.
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. Pdf analytical model for characterization of loop heat pipes. They can transport a large heat load over a long distance with a small. 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. Temperature expansion thermal expansion of pipes and tubes stainless steel, carbon steel, copper, plastics and more. 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. Loop heat pipes lhps are passive, twophase heat transport devices. Heat pipes heat transport limit for proper heat pipe operation, the total pressure drop must not exceed its capillary pressure head. Ats engineering ebook advanced thermal solutions, inc. 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. The technology was invented in the former soviet union in the 1980s for spacecraft thermal control. Lhps are similar to heat pipes but have the advantage of being able to provide reliable operation over long distance and the ability to operate against gravity. Outline from heat pipe to loop heat pipe and capillary pumped loop lhp operating principleslhp operating principles lhp components sizing and fluid inventory lhp operating temperature control lhp startup lhp shutdown lhp analytical modelinganalytical modeling recent lhp technology developments introduction to lhp ku 2015 tfaws 2. Steel pipe expansion loop capacity engineering toolbox.
The history of development of loop heat pipes lhps originates from 1972, when the first such device with a length of 1. Loop heat pipe transient behavior using heat source. 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. It is observed that the performance of the lhp is largely governed by the wicking characteristics of this porous membrane. Modern trends in electronic packaging and integration lead to extremally high power density designs. The values obtained from figure 4 are noted down in table 2 and table 3 to find out how effectively the miniature loop heat pipe cooling system works under 100% cpu load to drive away the excess. The abi infrared detectors need to be cold to accurately measure the thermal energy radiated from the earths atmosphere. Loop heat pipe, ammonia, elevated temperature, compatibility, non condensable gas. In actuality, one of the air handlers has a threeway. Test cell for a novel planar mems loop heat pipe based on.
It utilizes boiling and condensation to transfer heat, and the surface tension force developed at the liquidvapor interface on the evaporator wick to sustain the flow circulation. Kaya and goldak 5 reported the boiling limit of loop heat pipe obtained. An external fan was introduced to speed up the natural condensation process. The actual test results of heat pipe with different wick structure athorizontal and vertical gravity assist orientations. This part introduces components and phenomena, the next 3 parts describe modeling techniques in thermal desktop and flocad. Journals pdf frontiers in heat pipes fhp flow regime.
Loop heat pipes with flat evaporators sciencedirect. As air accumulates in the vents cylinder,the float lowers and even. Loop heat pipe design flexible heating pipe tech two. 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. 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. Historical perspectives, principles of operations, types of heat pipes are discussed. 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. Types of heat pipes thermosyphon leading edge rotating and revolving cryogenic pumped loop heat pipe flat plate micro heat pipes variable conductance capillary pumped loop heat pipe 16. Lhps can transfer heat efficiently up to several meters at any orientation in the gravity field.
The evaporator and condenser sections are 360 mm and 280 mm respectively. The lhp was first developed in the former soviet union in the early 1980s 1, about the same time that the capillary. 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. Analysis of heat transfer and flow patterns in a loop heat pipe. A loop heat pipe with coherent pores integrated to the heat source is considered as a calculation model in this paperfig.
Pdf a practical quasi threedimensional numerical model is. Astm a270 sanitary stainless steel tubing dimensions dimensions of astm a270 sanitary steel tubes. Steady state model of a loop heat pipe lhp with coherent. Loop heat pipes lhp s are twophase heat transfer devices that utilize the evaporation and condensation of a working fluid to transfer heat, and the capillary forces developed in fine porous wicks to circulate the fluid. 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. 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. Similarly, methods for modeling loop heat pipes lhps are distinct. Optimization of a loop heat pipe lhp with wick separated. Understanding loop heat pipes advanced thermal solutions.
The main objective of this project is to fabricate a 2m long loop heat pipe for efficient transfer of heat. The pump is controlled by a thermostat or timer, circulating water whenever it is needed to keep incoming water to the fixture at the desired temperature. The criteria set is simple and can be useful for calculations of lhp parameters and characteristics in engineering practice. Heat pipe minilhp can provide this function without many of the restrictions of conventional thermal. In an open loop system the pumps are typically located in a cabinet, under a shelf or counter top very near to the fixture. Keywords twophase flow, heat transfer, dimensionless, loop heat pipe, thermal control, figure of. Schematic of open and closed loop pulsating heat pipe with a prototype. Another common location is where a pipe must go up and over a structural beam and thus form a high point. Startup of the lhp was performed in flight and ground testing. Loop heat pipe lhp is a very robust and versatile heat transfer device which can transport large heat loads over long distances with small temperature differences1, 2.
The previous, approximately 10 mm thick evaporator of the loop heat pipe can now be reduced to 0. The radiator is divided in 176 thermal nodes having temperaturevarying capacitances. A wide variety of loop heat pipe options are available to you, such as directplug, split. Cold heat transfer fluid is circulated through the pipes and thus extracting the heat. Theoretical investigation of the thermal performance of a novel solar loop heat pipe facadebased heat pump water heating system wei he1,2, xiaoqiang hong1, xudong zhao2, xingxing zhang2, jinchun shen2, jie ji1 1department of thermal science and energy engineering, university of science and technology of china,hefei,china,230026. Operating characteristics of loop heat pipes semantic scholar. Cfd thermal analysis on laptop cooling system using loop. This study aims to create a loop heat pipe uses capillary wick copper sintered with.
Heat pipe design handbook, volume 1 internet archive. Details of the method of calculation is provided in the easy2000 users manual. Loop heat pipe sample model page 3 user documentation october 31, 2008 lhp prebuilt version 5. Pdf 3d heat transfer analysis in a loop heat pipe evaporator with a. Access to loop for flushingpurging and pressure testing is at flow center figure 1. A heat pipe loop hpl is a completely passive twophase heat transfer device that has features found in both heat pipes and loop heat pipes. An experimental package was constructed to operate a loop heat pipe lhp in microgravity aboard nasas kc5 aircraft. Miniature multiple evaporator multiple condenser loop heat pipe. A novel analytical modeling of a loop heat pipe employing. How to model a heat pipe heat transfer and fluid flow. Operating characteristics of loop heat pipes citeseerx. However, that method 1 does not simulate a heat pipes lengthindependent resistance, 2 cannot account for.
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