Loop heat pipe design flexible heating pipe tech two. The loop heat pipe is composed of evaporator, reservoir, capillary wick, vaporliquid line, and condenser. A key pe pipe design consideration for an open system is the fact that the system will have a suction and discharge loop. Pipe is a pressure tight cylinder used to convey a fluid or to transmit a fluid pressure, ordinarily designated pipe in applicable material specifications. A brief overview of loop heat pipes with respect to basic fundamentals, construction details, operating principles, and typical operating characteristics is presented in this paper. This book takes a systematic approach to the subject, focusing on the selection, design, rating, and operational challenges of various types of heat exchangers. The loop heat pipe lhp subsystem, which transfers heat from the abi electronics to the radiator, is not operating at its designed capacity. Aug 04, 2014 this entry was posted in heat pipe and tagged advanced thermal solutions, air flow, ats, electronics cooling, engineering, heat pipe, heat transfer, loop heat pipes, thermal design, thermal management.
A high thermal conductivity and permeability, and a low minimum capillary radius are somewhat contradictory properties in most wick designs. Instead, when it comes to cooling, heat pipes are standard. Pdf loop heat pipes lhps are twophase devices that can passively transport heat over long distances relative to other passive two phase systems. A loop heat pipe lhp is a passive twophase transfer device related to the heat pipe. The lhp evaporator wick uses capillary forces to passively supply liquid to the heated surface from the lower pressure condenser. Oscillating heat pipes ohp, also referred to as pulsating heat pipes php, are a relatively new development in the field of heat pipe technology. The ground itself is not a perfect heat sinksource because the energy added to the ground by the loop can change its temperature over time. The figures below illustrate the operating principles of a typical loop heat pipe. Heat pipe technology is pertinent to the design and application of selfcontrolled. The designer must balance the wick pumping capability against the wick permeability when designing a heat pipe or loop heat pipe. Feb 06, 2014 the heat pipe used in hpts heat recovery model hrm.
This paper presents and describes the test campaign of a lowcost loop heat pipes lhp design. Over the last several decades, several factors have contributed to a major transformation in heat pipe science and technology applications. This book provides a practical study of modern heat pipe engineering, discussing how it can be optimized for use on a wider scale. The evaporator configuration is the critical part of the performance design. This book describes the characteristics of heat pipes under steadystate and transient operating conditions. This handbook provides all aspects of piping design starting from fluid properties, stress analysis, construction and fabrication details, compensating methods for thermal expansion, erection etc. Circulating through a pipe formed in a closed loop, the liquid carries heat away from a hot spot. The life tests results investigation have generated important data that has been applied on the design and construction of loop heat. Published by butterworthheinemann, an imprint of elsevier, the sixth edition of heat pipes theory, design and applications, by david reay, peter kew and ryan mcglen, is a highly detailed book of over 250 pages. Heat pipes are considered as an effective thermal solution, particularly in high heat flux applications and in situations where there is a combination of nonuniform heat loading, limited airflow over the heatgenerating components, and space or weight constraints. Schematic of principle of operation of a loop heat pipe 1, 2. In contrast, an lhp has an inverted wick, with the. A loop heat pipe with coherent pores integrated to the heat source is considered as a calculation model in this paperfig.
Miniature loop heat pipes mlhps are coming up with a promising solution for the thermal management of futuristic electronics systems. For example, radiant floor heat has more even floortoceiling temperatures than other. Only fresh water is used, and there is no need for a special heat transfer or antifreeze solution. Steady state model of a loop heat pipe lhp with coherent porous silicon cps wick in the evaporator mohammed hamdan, frank m. 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.
Apr 01, 2005 loop heat pipes lhps are twophase heat transfer devices with capillary pumping of a working fluid. Steady state model of a loop heat pipe lhp with coherent. There is no connection whatsoever to the domestic water supply. Design considerations when using heat pipes electronics cooling. The previous, approximately 10 mm thick evaporator of the loop heat pipe can now be reduced to 0. 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. Introduction geothermal heat pumps aka ground source heat pumps ghp or gshp are used in two basic modes.
Loop heat pipes lhps are twophase devices that can passively transport heat over long distances relative to other passive two phase systems such as heat pipes. Loop design theory loop types a ground loop is a heat exchanger that either extracts or adds heat to the ground. Lownoise cooling system for pc on the base of loop heat pipes vladimir g. How do a pipe loop with expansion joints absorb movements. The design idea of the worlds first lhp system was proposed by scientists in 1971. Chapter hvac applications for pe pipe 465 then discharges the water back into the water supply. Heat pipes, 6th edition, takes a highly practical approach to the design and. As with any design process, many of the decisions that must be taken are interrelated and the process is iterative.
From heat pipe to loop heat pipe and capillary pumped loop. Loop heat pipes lhps are twophase heat transfer devices that utilize the evaporation and condensation of a working fluid to transfer heat, and the capillary forces. It doesnt cover newer heat pipe variations, such as pressure controlled heat pipes and variable conductance heat pipes, or loop heat pipes lhps. The main advantage to this system lies in the fact that, being closed, antifreeze instead of water can be used as the heat transfer medium.
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. Novel design of a miniature loop heat pipe evaporator for. Most of the art of lhp fabrication is in the primary and secondary wick. Pipes heating expansion and cooling contraction expansion or contraction when heating or cooling cast iron, carbon and carbon molybdenum steel, wrought iron, copper, brass and aluminum pipes. Written by a former senior chief scientist at lockheed who has also worked for westinghouse and the u. Loop heat pipe design, manufacturing and testing an industrial. The research will enable design, optimisation and analysis of such a new galhp. 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. This book introduces operational and design principles for heat pipes. Zurn radiant heating design and application guide radiant panel heating increases our comfort in many ways. This article is intended to offer design guidance when using heat pipes for the most prevalent types of electronics applications. This allows the wick in a loop heat pipe to be required only in the evaporator and. Single and multiple loop php studies are widely reported in the literature. Compensation chamber an overview sciencedirect topics.
Closed evaporationcondensation cycle which is realized inside of the twophase system leads to the extremely small temperature gradients along the heat pipe loop resulting in devices of a very high, unbeatable thermal conductivity. Originally developed and patented by hisateru akachi in 1990, ohps consist of a long meandering tube which is heated and cooled at. Pipes and tubes temperature expansion pipes expands when heated and contracts when cooled and the expansion can be expressed with the expansion. In order to implement these devices inside compact electronics, their evaporator has to be developed with small thickness while preserving the unique thermal characteristics and physical concept of the loop scheme.
Different working fluids, different liquid filling amounts, different capillary wicks, different sizes, and different cooling methods will have an important impact on the. Amir faghri written to cover simple, intermediate, and advanced approaches to the theoretical and experimental analysis of heat pipes, this second edition emphasizes the physics and mathematics of heat pipes as well as the related technological and experimental issues. We order this book in bulk to give to our engineers and research technicians i just bought 20 more copies. One of the first steps in heat pipe design is the working fluid selection. Materials designated tube or tubing in the specifications are treated as pipe when intended for pressure service.
Capillary wick designs and structures in heat pipes. In a heat pipe, the wick extends along the entire length so there are long lengths and large pressure drops for the liquid flow in the wick. An introduction to operational and design principles, this book. Introduction to loop heat pipes introduction to lhp ku 2015 tfaws 10. Understanding loop heat pipes advanced thermal solutions.
On the abovementioned production of line pipes, the design of base material together with welding material is not satisfactory on the stand point. Infloor radiant design guide hydronic underfloor heating. For example, choice of the wick and case material eliminates many candidate working fluids often including water due to. Closed loop systems the following presentation is a summary of material with the appropriate unit conversions presented in groundsource heat pumps design of geothermal systems for commercial and institutional buildings by. However, advanced military platforms have found this approach limits their operational effectiveness. Steel pipe expansion loop capacity engineering toolbox. In this paper, results of the nrl lhp experimental studies, conducted by naval research laboratory nrl and nasa goddard space flight center, will be presented. Loop heat pipes lhp are capable of providing a means of transporting. The evaporator receives heat from heat source, thus working fluid undergoes a phase change and turns into. Finally, the paper presents the current developments in modeling of thermohydraulics and design. Loop heat pipes lhps are twophase heat transfer devices with capillary pumping of a working fluid. Once you have the flow and have decided on the number of loops and by deduction the flow per loop then you can pick a diameter of pipe which regulates the flow velocity between a nominal 1.
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. Vapor grooves liquid line a section aa condenser main design features. This entry was posted in heat pipe and tagged advanced thermal solutions, air flow, ats, electronics cooling, engineering, heat pipe, heat transfer, loop heat pipes, thermal design, thermal management. Heat pipes are considered as an effective thermal solution, particularly in high heat flux applications and in situations where there is a combination of nonuniform heat loading, limited airflow over the heat generating components, and space or weight constraints.
Operating characteristics of loop heat pipes jentung ku. 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 pipe design, manufacturing and testing an. The heat pipe temperature reaches the water temperature in about 25 seconds, while the copper rod reaches just 30c after 200 seconds.
Their potential as passive heat transfer devices has been widely demonstrated in numerous both ground and spacebased applications. The loop heat pipe lhp is a passive twophase heat transport device that is gaining importance as a part of spacecraft thermal control systems and also in applications such as in avionics cooling. Design and technology of heat pipes for cooling and heat exchange. A thermal management system for electronics cooling in high temperature avionics environments is under development using loop heat pipe lhp and heat pipe based technology. A novel multistages loop heat pipe for cooling multiple heat sources, in. During postlaunch testing of the goes17 abi instrument, an issue with the instruments cooling system was discovered. Study of a novel liquidvapour separatorincorporated. This method has been used in the aerospace industry for about thr ee decades for supporting systemlevel design analysis. 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. The book begins with a thorough analysis of heat pipe infrastructure, including principles of operation, temperature limits, reliability and lessons learned from worked examples and case studies.
It utilizes boiling and condensation of the working fluid to transfer heat, and the surface tension forces of menisci formed at the liquidvapor interfaces on the porous wick to. The loop heat pipe is a variant of the ordinary heat pipe, and is a twophase flow loop type heat pipe, which is a unidirectional heat conduction element similar to a diode. Heat pipe science and technology, second edition by dr. Such considerations lead to successful operation for the design life of the unit. It emphasizes the physical aspects of heat pipe behavior and develops design formulas on the basis of mathematical models and empirical observation. Optimization of wick shape in a loop heat pipe for high heat transfer. This part introduces components and phenomena, the next 3 parts describe modeling techniques in thermal desktop and flocad. It can carry higher power over longer distances by having cocurrent liquid and vapor flow, in contrast to the countercurrent flow in a heat pipe.
Heat pipes are used in a wide range of applications, including electronics cooling, diecasting and injection moulding, heat recovery and energy conservation, deicing and manufacturing process temperature control, and in domestic appliances. For hydronic systems that provide both heating and cooling, the distribution system may be configured as either a 2 pipe system or a 4 pipe system. These studies highlight the influence of various design parameters of php on its performance. Esa satellite cooling system makes paris metro more. The technology was invented in the former soviet union in the 1980s for spacecraft thermal control.
Loop heat pipes lhps are twophase devices that can passively transport. Emphasis in this test program is to examine the turnkey startup of the nrl lhp and its. A large value for this parameter gives a small temperature drop across the wick, which is a favorable condition in heat pipe design. The loop heat pipe was first studied for the difficult temperature control conditions under aerospace conditions. A loop heat pipe lhp is one of the most efficient twophase heat transfer devices. Thermal performance and operational characteristics of. The first major contribution was the development and advances of new heat pipes, such as loop heat pipes lhps, micro and miniature heat pipes, and pulsating heat pipes phps. The loop heat pipe is composed of evaporator, reservoir, capillary. Lownoise cooling system for pc on the base of loop heat pipes. The most common variants are discussed here, including variable conductance heat pipes, oscillating and loop units, rotating and microheat pipes. Thinner loop heat pipe this loop heat pipe uses copper sheets that are only 0. Written by wellknown authors in the field of heat transfer, this book covers all the most commonly used types of heat exchangers, including condensers and evaporators.
It covers all of the basics, which havent changed since the book was written. However, a loop heat pipe can start, stop, and restart, at any time regardless of operating conditions. I have been involved in heat pipe design, fabrication, and testing for almost 30 years. To summarize, if you are a student just learning about heat pipes, or are on a limited budget, then this is a great book to get started. Variable conductance heat pipes vchp loop heat pipes. To maintenance of all pipeworks whether underground or overhead, carrying any fluid like water, oil, air, industrial gases like oxygen, nitrogen, acetylene etc. Design tools based on computational fluid dynamics simulation and hshptm heat sinkheat. It is now around 40 years since work began on the first edition, and it has. Here, a single piping loop is used to supply either chilled water during the cooling season or hot water during the heating season. Experimental study on thermal performance of loop heat. If the inner diameter of the capillary tube is small enough. Working of closed loop pulsating heat pipe the tube is first evacuated and then filled partially with a working fluid. Functionality, advancements and industrial applications of. Loop heat pipe lhp 3, 4, 5 is a twophase liquidvapour heat transfer.
Review and advances in heat pipe science and technology. If you are just getting interested in heat pipes, dunn and reay is an excellent starting point. Henderson department of mechanical, industrial, and nuclear engineering department of electrical and computer engineering and computer science university of cincinnati. The principles of this interaction are common in all loop types and will be discussed here.
The book is a useful reference for those with experience and an accessible. Loop heat pipes can be configured to handle multiple heat sources or evaporator sections, transport heat up to 23 meters 75 feet, withstand millions of flex cycles, or resist gravity loads up to 9g. Henderson department of mechanical, industrial, and nuclear engineering. Nov 25, 2016 heat pipe science and technology, second edition by dr. During its operation, a portion of the heat load applied to the evaporator is transferred to its compensation chamber cc through the evaporator sidewall, which is known as a heat leak, decreasing the performance of the lhp startup to a certain degree. Maydanik institute of thermal physics, ural branch of the russian academy of sciences, amundsen st. The specially designed evaporator and separated li quid and vapor lines are distinguishing features of the loop heat pipes lhp as a unique class of heat transfer devices. Today no one alternative heat transfer device can be as efficient as a heat pipe loop. Aavids loop heat pipes are rugged solutions for demanding environments. The percentage of propylene glycol antifreeze is determined by the type of heat source on. The loop heat pipe lhp was invented in russia in the early 1980s. The figure below shows how cm loop heat pipe operates.
Schematic of an lhp primary wick compensation arteries chamber evaporator. Heat pipe design handbook, volume 1 internet archive. Heat pipes and heat loops are heat superconductors. 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. Oct 12, 2006 peter kew first became involved in heat pipes in the late 1970s as a research officer with international research and development working on a range of heat transfer and energy conservation projects, including heat pipe development which was then led by david reay. This book presents current research and development related to the design, applications and technology of various heat pipes, including conventional heat pipes and thermosyphon, pulsating heat pipes, loop heat pipes, and variable conductance heat pipes.
Lhps are high thermal conductance devices that are selfcontained and passive. Data bases for standard pipe size and wall thickness and expansion characteristics may be accessed, or user data entered. Loop heat pipes lhps are passive, twophase heat transport devices. Heat pipes are not new, but many variants and applications are. Unfortunately, temperature control is not always possible with a loop heat pipe, and its effective thermal conductance is not as high as that of a capillary pumped loop hoang et al. Electronics cooling using high temperature loop heat pipes. In a heat pipe wick, heat enters from the liquid side of the wick. Loop heat pipe cooler master has developed a loop heat pipe for high heat flux, longdistance transportation and antigravity for graphics card application. 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. 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. This book is intended to explore some of the recent advances in heat pipes and their applications in thermal systems. In contrast, an lhp has an inverted wick, with the vapor located adjacent to the heated surface. Loop heat pipes lhps and capillary pumped loops cpls are.
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