Only fresh water is used, and there is no need for a special heat transfer or antifreeze solution. Lhps are high thermal conductance devices that are selfcontained and passive. 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. 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.
There is no connection whatsoever to the domestic water supply. 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. Loop heat pipes lhps are passive, twophase heat transport devices. The most common variants are discussed here, including variable conductance heat pipes, oscillating and loop units, rotating and microheat pipes. This book introduces operational and design principles for heat pipes.
Chapter hvac applications for pe pipe 465 then discharges the water back into the water supply. Schematic of an lhp primary wick compensation arteries chamber evaporator. Electronics cooling using high temperature loop heat pipes. The research will enable design, optimisation and analysis of such a new galhp. 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. From heat pipe to loop heat pipe and capillary pumped loop. 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. This part introduces components and phenomena, the next 3 parts describe modeling techniques in thermal desktop and flocad. We order this book in bulk to give to our engineers and research technicians i just bought 20 more copies. As with any design process, many of the decisions that must be taken are interrelated and the process is iterative.
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. The loop heat pipe was first studied for the difficult temperature control conditions under aerospace conditions. In contrast, an lhp has an inverted wick, with the vapor located adjacent to the heated surface. Data bases for standard pipe size and wall thickness and expansion characteristics may be accessed, or user data entered.
Lownoise cooling system for pc on the base of loop heat pipes vladimir g. Compensation chamber an overview sciencedirect topics. The figure below shows how cm loop heat pipe operates. Introduction geothermal heat pumps aka ground source heat pumps ghp or gshp are used in two basic modes. It emphasizes the physical aspects of heat pipe behavior and develops design formulas on the basis of mathematical models and empirical observation. A loop heat pipe with coherent pores integrated to the heat source is considered as a calculation model in this paperfig. 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. The percentage of propylene glycol antifreeze is determined by the type of heat source on. An introduction to operational and design principles, this book. Loop heat pipes lhp are capable of providing a means of transporting. 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. These studies highlight the influence of various design parameters of php on its performance.
Loop heat pipe design, manufacturing and testing an industrial. Esa satellite cooling system makes paris metro more. Working of closed loop pulsating heat pipe the tube is first evacuated and then filled partially with a working fluid. 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. 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. 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. How do a pipe loop with expansion joints absorb movements. Experimental study on thermal performance of loop heat. For example, choice of the wick and case material eliminates many candidate working fluids often including water due to. The life tests results investigation have generated important data that has been applied on the design and construction of loop heat. The lhp evaporator wick uses capillary forces to passively supply liquid to the heated surface from the lower pressure condenser. Thermal performance and operational characteristics of. Steady state model of a loop heat pipe lhp with coherent.
This book provides a practical study of modern heat pipe engineering, discussing how it can be optimized for use on a wider scale. Functionality, advancements and industrial applications of. 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. The loop heat pipe lhp subsystem, which transfers heat from the abi electronics to the radiator, is not operating at its designed capacity. Different working fluids, different liquid filling amounts, different capillary wicks, different sizes, and different cooling methods will have an important impact on the. It is now around 40 years since work began on the first edition, and it has. 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. Study of a novel liquidvapour separatorincorporated. 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. 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 method has been used in the aerospace industry for about thr ee decades for supporting systemlevel design analysis. I have been involved in heat pipe design, fabrication, and testing for almost 30 years. For example, radiant floor heat has more even floortoceiling temperatures than other. The heat pipe temperature reaches the water temperature in about 25 seconds, while the copper rod reaches just 30c after 200 seconds.
It doesnt cover newer heat pipe variations, such as pressure controlled heat pipes and variable conductance heat pipes, or loop heat pipes lhps. Aavids loop heat pipes are rugged solutions for demanding environments. If the inner diameter of the capillary tube is small enough. 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. The loop heat pipe is composed of evaporator, reservoir, capillary. Capillary wick designs and structures in heat pipes. Loop heat pipes lhps are twophase devices that can passively transport. Heat pipes, 6th edition, takes a highly practical approach to the design and. Loop heat pipe design, manufacturing and testing an. 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. The previous, approximately 10 mm thick evaporator of the loop heat pipe can now be reduced to 0. To maintenance of all pipeworks whether underground or overhead, carrying any fluid like water, oil, air, industrial gases like oxygen, nitrogen, acetylene etc. Instead, when it comes to cooling, heat pipes are standard. Review and advances in heat pipe science and technology.
Oscillating heat pipes ohp, also referred to as pulsating heat pipes php, are a relatively new development in the field of heat pipe technology. 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. 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. Finally, the paper presents the current developments in modeling of thermohydraulics and design. On the abovementioned production of line pipes, the design of base material together with welding material is not satisfactory on the stand point.
Most of the art of lhp fabrication is in the primary and secondary wick. 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. Every heat pipe theory book has a paragraph or chapter, which are dedicated to this problem. However, a loop heat pipe can start, stop, and restart, at any time regardless of operating conditions. Apr 01, 2005 loop heat pipes lhps are twophase heat transfer devices with capillary pumping of a working fluid. A novel multistages loop heat pipe for cooling multiple heat sources, in. Design considerations when using heat pipes electronics cooling. Circulating through a pipe formed in a closed loop, the liquid carries heat away from a hot spot. Design and technology of heat pipes for cooling and heat exchange. The figures below illustrate the operating principles of a typical loop heat pipe. 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. Henderson department of mechanical, industrial, and nuclear engineering.
Pdf loop heat pipes lhps are twophase devices that can passively transport heat over long distances relative to other passive two phase systems. The book is a useful reference for those with experience and an accessible. It also presents a concise design guideline for the assembly of heat pipes. 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. The evaporator receives heat from heat source, thus working fluid undergoes a phase change and turns into. Miniature loop heat pipes mlhps are coming up with a promising solution for the thermal management of futuristic electronics systems. 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. 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. Heat pipe science and technology, second edition by dr.
Pipes and tubes temperature expansion pipes expands when heated and contracts when cooled and the expansion can be expressed with the expansion. 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. Loop heat pipes lhps and capillary pumped loops cpls are. 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. 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. The technology was invented in the former soviet union in the 1980s for spacecraft thermal control. Steady state model of a loop heat pipe lhp with coherent porous silicon cps wick in the evaporator mohammed hamdan, frank m.
Loop heat pipes lhps are twophase heat transfer devices with capillary pumping of a working fluid. Over the last several decades, several factors have contributed to a major transformation in heat pipe science and technology applications. Written by a former senior chief scientist at lockheed who has also worked for westinghouse and the u. 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. The designer must balance the wick pumping capability against the wick permeability when designing a heat pipe or loop heat pipe. Today no one alternative heat transfer device can be as efficient as a heat pipe loop.
In contrast, an lhp has an inverted wick, with the. Loop design theory loop types a ground loop is a heat exchanger that either extracts or adds heat to the ground. Understanding loop heat pipes advanced thermal solutions. 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. Emphasis in this test program is to examine the turnkey startup of the nrl lhp and its. Variable conductance heat pipes vchp loop heat pipes. The design idea of the worlds first lhp system was proposed by scientists in 1971.
This allows the wick in a loop heat pipe to be required only in the evaporator and. The loop heat pipe is composed of evaporator, reservoir, capillary wick, vaporliquid line, and condenser. Heat pipe technology is pertinent to the design and application of selfcontrolled. Operating characteristics of loop heat pipes jentung ku. Zurn radiant heating design and application guide radiant panel heating increases our comfort in many ways. 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. In a heat pipe wick, heat enters from the liquid side of the wick. 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. Thinner loop heat pipe this loop heat pipe uses copper sheets that are only 0. Heat pipes are not new, but many variants and applications are.
The loop heat pipe lhp was invented in russia in the early 1980s. Originally developed and patented by hisateru akachi in 1990, ohps consist of a long meandering tube which is heated and cooled at. A high thermal conductivity and permeability, and a low minimum capillary radius are somewhat contradictory properties in most wick designs. 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. Thermal expansion of the carrier pipe during operation is. This book describes the characteristics of heat pipes under steadystate and transient operating conditions. Schematic of principle of operation of a loop heat pipe 1, 2. This book is intended to explore some of the recent advances in heat pipes and their applications in thermal systems. Loop heat pipe lhp 3, 4, 5 is a twophase liquidvapour heat transfer. Materials designated tube or tubing in the specifications are treated as pipe when intended for pressure service.
The working medium is mainly composed of a gas phase and a liquid phase in the steam pipe and the liquid pipe respectively. Vapor grooves liquid line a section aa condenser main design features. Loop heat pipe design flexible heating pipe tech two. 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. 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. Introduction to loop heat pipes introduction to lhp ku 2015 tfaws 10. 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. Ats engineering ebook advanced thermal solutions, inc. Maydanik institute of thermal physics, ural branch of the russian academy of sciences, amundsen st. Heat pipes and heat loops are heat superconductors.
This article is intended to offer design guidance when using heat pipes for the most prevalent types of electronics applications. 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. However, advanced military platforms have found this approach limits their operational effectiveness. A loop heat pipe lhp is one of the most efficient twophase heat transfer devices. Infloor radiant design guide hydronic underfloor heating. It covers all of the basics, which havent changed since the book was written. 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. Feb 06, 2014 the heat pipe used in hpts heat recovery model hrm. A large value for this parameter gives a small temperature drop across the wick, which is a favorable condition in heat pipe design. Henderson department of mechanical, industrial, and nuclear engineering department of electrical and computer engineering and computer science university of cincinnati. This paper presents and describes the test campaign of a lowcost loop heat pipes lhp design. Here, a single piping loop is used to supply either chilled water during the cooling season or hot water during the heating season. Pipe is a pressure tight cylinder used to convey a fluid or to transmit a fluid pressure, ordinarily designated pipe in applicable material specifications.
Optimization of wick shape in a loop heat pipe for high heat transfer. If you are just getting interested in heat pipes, dunn and reay is an excellent starting point. 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. 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. 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. 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. Design tools based on computational fluid dynamics simulation and hshptm heat sinkheat. Loop heat pipe cooler master has developed a loop heat pipe for high heat flux, longdistance transportation and antigravity for graphics card application.
Steel pipe expansion loop capacity engineering toolbox. 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. A loop heat pipe lhp is a passive twophase transfer device related to the heat pipe. Lownoise cooling system for pc on the base of loop heat pipes. 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. Such considerations lead to successful operation for the design life of the unit. Single and multiple loop php studies are widely reported in the literature. During postlaunch testing of the goes17 abi instrument, an issue with the instruments cooling system was discovered. This book takes a systematic approach to the subject, focusing on the selection, design, rating, and operational challenges of various types of heat exchangers. Nov 25, 2016 heat pipe science and technology, second edition by dr. 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. 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. The evaporator configuration is the critical part of the performance design. One of the first steps in heat pipe design is the working fluid selection.
A key pe pipe design consideration for an open system is the fact that the system will have a suction and discharge loop. Heat pipe design handbook, volume 1 internet archive. Novel design of a miniature loop heat pipe evaporator for. The principles of this interaction are common in all loop types and will be discussed here. 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.
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