The entire assembly was tested in a thermal vacuum chamber at nasngsfc in early 2002. We can design modern systems that do not have to address any of the above. Loop heat pipe design flexible heating pipe tech two. The installation of the check valve is very difficult and costly because of the small nature of the device. Allows direct contact with heat source 1piece vapor chamber 10mm bend radius along. Loop heat pipe analysis loop heat pipes utilize the evaporation and condensation of fluid to transfer heat. To get a better understanding of the loop heat pipe and to determine the heat flux as well as evaporator base body temperature, thermocouples were distributed along the loop heat pipe as follows. Last but not the least, although the calculation or simulation can provide. The oscillating or pulsating heat pipe php is another. All piping engineers are well acquainted with expansion loops in the piping systems.
Although the lhp has been studied by many researchers, published results about its optimum design were few. One solution to remove excess heat is by utilization of heat pipes which are employed to remove the excess heat by directly attaching them to the heat source. Chilled water plant design guide december 2009 energydesignresources. The length of piping between the water heater and each fixture, the pipe diameter, and the material from which the pipe is made can all have great impact on hot water delivery system efficiency, because those factors determine the volume of water stored within the delivery system. Their performance has been proven through many experiments and actual applications in satellites, electronic devices and aircrafts. Fundamental study of heat pipe design for high heat flux source. Assume a wet rotor circulator with wiretowater efficiency of 25 is used as the primary circulator. The lhp was first developed in the former soviet union in the early 1980s 1, about the same time that the capillary. Modeling tools and prototype design of loop heat pipe for electronics. Experimental study on loop heat pipe under horizontal. Loop heat pipe, steadystate behavior, heat transfer coefficient, capillary structure, flat evaporator.
Design and analysis of highperformance aircooled heat exchanger with an integrated capillarypumped loop heat pipe matthew mccarthy1, teresa peters1, jon allison1, alonso espinosa1, david jenicek2, arthur kariya1, catherine koveal1, john g. Loop heat pipes lhps are passive, twophase heat transport devices. Modern hydronicsystem designs for condensing boilers. The life tests results investigation have generated important data that has been applied on the design and construction of loop heat pipes. Then different components of lhp and their contribution to the overall system operation are studied. Proper designs will determine the size and quantity of pipes which are required to meet design loads in btu, kw or tons of energy for a specific system. Compared to convenronal heat pipes, the one way flow of working the fluid inside the loop heat pipe, improves the heat transport capability. This statement is based on the advantages of lhps over conventional heat pipes. Both need to heat up before heat can be delivered to radiators. Dec 19, 2020 the allnew loopcad 2020 offers advanced design features including integrated heating and cooling load calculations, detailed hydronic calculations, snowmelt design, 3d cad views, and compatibility with oem design methods and materials.
Thermal vacuum testing of a novel loop heat pipe design. The blankets and shields protect the instrument from absorbing too much solar radiation. 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. Figure 7 shows a schematic of the current loop heat pipe design with multiple flat plate condensers. These are mainly required in any piping system design to. Loop heat pipes lhps and capillary pumped loops cpls are highcapacity passive heattransport. The wick is made of copper instead of ptfe polytetrafluoroethylene and has pores of size 0. Liquid cores play a critical role in reducing the pressure drop in the wick and in increasing the path length for heat transfer. Loop heat pipe for tacsat4 advanced cooling technologies. Although the user can build models of custom parts and control systems, prepackaged tools are provided for modeling common components such as pipes, pumps, valves, filters, accumulators, etc. Loop heat pipes lhp are used to cool electric devices in a satellite. Wang1 1department of mechanical engineering, 2department of electrical engineering. Loop heat pipes lhp are capable of providing a means of transporting large quantities of heat over long.
One of the first steps in heat pipe design is the working fluid selection. Thermal vacuum testing of a novel loop heat pipe design for. Mechanical engineering in this study a flat, flexible evaporator, which can conform to contoured surfaces, has been investigated for loop heat pipe applications. The figures below illustrate the operating principles of a typical loop heat pipe. In the course of this work, the lhp and its components including. Optimizing the design of a twophase cooling system loop. Plastic piping materials for ground source geothermal.
Whenever thermal displacements are more than a certain value these expansion loops are added to absorb the displacement inside the expansion loop. This paper designs and discusses a microplate loop heat pipe which is suitable for the heat dissipation of various electronic chips, discusses and explains. Mathematical modeling and testing of a loop heat pipe. Grooves and liquid cores are mounted on the evaporator case in the design of a flat evaporator. Although the flight system will consist of two lhps, a single unit, as shown in figure 2, was built for testing due to finding limitations. Experimental investigation on a thin loop heat pipe with new. This study aims to create a loop heat pipe uses capillary wick copper sintered with.
Loop heat pipe lhp is a tw ophase thermal m anagement device, usually appl ied in the th ermal control of. For the ease of the calculation, the calculation of the pressure drop of. Piping loops exchange heat with the earthgeothermal heat pumps can have efficiencies cop greater than 450%when operating in heating mode heat is rejected to the earth when cooling high eer heat pumps are indoors, out of sight, no noise low operating costs, high reliability, economical example of submerged pond loop courtesy igshpa. Design and manufacturing of loop heat pipes for electronics. Experimental study on a hybrid loop heat pipe matec web of. Experimental investigation on a thin loop heat pipe with. Thermal expansion of the carrier pipe during operation is.
The design of heat pipe test rig consists of following components. The recognition of the heat pipe as a reliable thermal device was initially due to the preliminary theoretical results and design tools that were reported in the first publication on heat pipe analysis by cotter 4. An example of primary loop circulator operating cost. Heat pipe 1piece vapor chamber 2piece vapor chamber 20 heat pipes bend radius 3x diameter of heat pipe. The radiator is a large reflective surface designed to reject excess thermal energy to space. The mathematical model, design, fabrication integration of the heat pipe with the pulse tube system and testing with stainless steel wick at the evaporator will be. Mathematical modeling and testing of a loop heat pipe using a. In order to verify the design for the bat loop heat pipes, an engineering test unit etu was built and tested in a thermal vacuum chamber at goddard space flight center. The loop heat pipe lhp technology has been under development by this. Consider a system that supplies 500,000 btuhr at design load.
Performance of flexible evaporator for loop heat pipe technlogies by mukta limaye december 2007 chair. An emphasis is put on the effect of a single operating parameter or design constraint on the overall lhp performance. The main advantages of the heat loops are 1 capability to manage high power densities due to special design of the evaporator and 2 great. This is a pdf file of an unedited manuscript that has been accepted for publication.
To get a better understanding of the loop heat pipe and to determine the heat flux as well as evaporator base body temperature, thermocouples were distributed along the loop heat pipe. Lhp is a twophase passive device which mainly consists of evaporator, condenser and compensation chamber cc, vapor line, liquid line and wick fig. 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. Newer modcon boilers usually have only a doe rating and have no pickup allowance since they are very low mass and heat up relatively quickly compared to. Table 1 presents the overall organization of sindafluint modeling tools. Introduction loop heat pipes lhp were firstly conceived in russia in the mid 70s to address some of the heat transfer issues present on board spacecrafts 17. Feb 10, 2021 a loop heat pipe lhp is a cooling device widely used in controlling the temperature of electronic components or packages to enhance their capabilities to deliver more efficiency. A loop heat pipe with coherent pores integrated to the heat source is considered as a calculation model in this paperfig. Pickup allows for the heating up of cold castiron boiler sections and cold steel pipe. 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. Such a development has been focused on designing, manufacturing, assembling. Why loop heat pipes are necessary the loop heat pipes transfer excess thermal. The extensive development of heat pipe technology has led to a variety of heat pipes, in terms of geometry, function andor operation, each designed to fit specific heat rejection and redistribution requirements for particular applications.
Loop heat pipes are similar to heat pipes but have the advantage of being able to provide reliable operation over long distance. Newer modcon boilers usually have only a doe rating and have no pickup allowance since they are very low mass and heat up relatively quickly compared to a cast iron boiler. Design optimization of a loop heat pipe to cool a lithium. The technology was invented in the former soviet union in the 1980s for spacecraft thermal control. Materials designated tube or tubing in the specifications are treated as pipe when intended for pressure service.
The use of loop heat pipes 912 as a thermal connection between the heat source and the heat sink opens new opportunities for the increase of e. Numerical analysis of performance of closed loop pulsating. Flow in the primary loop is 50 gpm with a corresponding head loss of 15 feet 6. Modeling of heat transfer and flow patterns in a porous. For lhp design and fabrication, preliminary analysis on the basis of dimensionless criteria is necessary due to complicated phenomena, which take place in the heat pipe. Heattransfer characteristics of a cryogenic loop heat pipe. Overview of piping expansion loop on the piping system. 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. Loop heat pipes lhp are capable of providing a means of transporting large. Pdf loop heat pipe ijirst international journal for. Plastic piping materials for ground source geothermal heating.
Capillary forces develop in porous wicks and drive flow between an evaporator and, traditionally, a single condenser. Pdf loop heat pipes lhps have been extensively investigated and considered for the thermal control of satellites and other space. Lhps are similar to heat pipes but have the advantage of being able to provide reliable operation over long distance and the ability to. The closed loop pulsating heat pipe has no complex structure so it is to be modeled. Optimizing the design of a twophase cooling system loop heat. Flow visualization was conducted for the closed loop pulsating heat pipe using ansys fluent. Loop heat pipes lhps are twophase heat transfer devices with capillary pumping of a working fluid. A loop heat pipe lhp is a twophase heat transfer device that uses the latent heat of vaporization of a working fluid for heat transfer. In this dissertation, a set of modeling tools for loop heat pipe lhp design is developed, and original analytical models for annular. So, the closed loop pulsating heat pipe modeled here has no wick material inside it as it present in heat pipe.
Mar 09, 2021 this paper presents thin loop heat pipes tlhps with evaporator thickness of 1 mm and a oneway transport length of 200 mm. 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 developed in fine porous wicks to circulate the fluid. The heat is transported to an external radiator by the loop heat pipes. 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. Tpls including loop heat pipes lhps and capillary pump loop cpls have attracted. Design optimization of a loop heat pipe to cool a lithium ion. Optimization of wick shape in a loop heat pipe for high heat transfer. Many of the present days electronic devices require cooling beyond the capability of conventional metallic heat sinks. The pressure loss at the wick in the loop heat pipes can be kept lower than in the conventional hps. 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.
Due to their inherent robustness, lhps are ideal candidates to meet the ever increasing thermal challenges facing the electronics and spacecraft industries. Lhps are high thermal conductance devices that are selfcontained and passive. With the use5 of the space shuttle, flight testing of prototype heat pipe designs continued at a much larger scale. Heat pipes are referred to as the superconductors of heatdue to their fast transfer capability with low heat loss.
In the calculation, two values of htri were used see table 2. Jan 25, 2017 evaporative heat transfer model of a loop heat pipe with bidisperse wick structure int. A thermoelectric generator using loop heat pipe and design. So, the closed loop pulsating heat pipe without a check valve is mostly used. Introduction loop heat pipes are twophase transport devices which utilize the capillary pressure developed in a fine capillary structure fcs pore wick to circulate the working fluid in a closed loop system connected heat source and heat. Plastic piping materials for ground source geothermal systems.
The evaporator configuration is the critical part of the performance design. Dec 01, 2014 also heat pipe experiments were conducted aboard the applications technology satellite6, in which an ammonia heat pipe with a spiral artery wick was used as a thermal diode. Heat enters the evaporator and vaporizes the working fluid at the interface between the wick and envelope. Lownoise cooling system for pc on the base of loop heat pipes. A design of the microplate loop heat pipe and development of the. The lhp uses ammonia as the working fluid and was designed. Modeling of heat transfer and flow patterns in a porous wick.
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. They can transport a large heat load over a long distance with a small. As noted, this calculation does not take into account the fluid motion inside the wick. Condition of 1dnode network analysis for calculation of cooling flow.
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