Heat pipe theory pdf files

However, there are differences in the methods used, such as the heating temperatures, cooling rates, and quenching media necessary to achieve the desired properties. The vacuum pump model doap707aa and 18 hp is used for evacuating the heat pipe. Heat tracing is a method to provide the supplemental heat just enough. Wick structure problem description a heat pipe with minimum heat transport of 25 w is going to be used for cooling electronic components. The working fluids tested are diwater, silverwater colloid. Theory of the ultimate heat transfer limit of cylindrical. The original patent for heat pipes was granted in 1942 to mr. There has been much research on modelling the heat transfer associated with buried pipes with constant wall temperatures 7. Insulation will slow the heat loss, but will not prevent it. Hence, other than thermal design of the heat pipe, mechanical design of the.

Heat transfer and flow analysis in loop heat pipe with. Ats engineering ebook advanced thermal solutions, inc. The graph also shows that if the heat pipe is operated against the force of gravity, the liquid undergoes a larger pressure drop. Therefore, knowledge of the velocity distribution near a solid. Heat pipe is a capillary twophase heat transfer device. Heat pipes hardware m t l l i t b ith th i fmetal aluminum tube with grooves on the inner surface cold t ild extrusion grooves are filled with the working fluid water, ammonia, propylene, etc. The extensive theoretical and experimental investigations from the. When the evaporator section le is exposed to a heat source, the liquid inside vaporizes and the pressure in that section increases. The heat pipe is a twophase cooling solution, offering very high thermal coefficients. Starts with the introduction of heat exchangers and is concerned with the detailed classification of heat exchangers according to contact types, surface compactness, number of fluids, flow arrangement and. The liquid pressure decreases as it flows from the condenser to the evaporator. Various works on the heat transfer performance of loop heat pipes have been reported. Busse euratom ccr, 21020 ispra, italy received 22 december 1971 and in revised form 10 april 1972 abstracthe axial heat flux in heat pipes is limited in principle for two reasons.

The steam generator is also provided with temperature indicator cum controller and a safety valve. Intermediate heat transfer, a second course on heat transfer for undergraduate seniors and beginning graduate students. The theories of transient heat transfer in double pipe heat exchangers were explained and followed by literature correlations. The force of attraction to the earth of the hot fluid is less than for the cold fluid. A heat pipe is a two phase heat transfer device with a very high effective thermal conductivity. Heat pipe technology is currently still under development. Journals pdf frontiers in heat pipes fhp effect of. Whenever the contents of a pipe or vessel are maintained at temperatures exceeding the ambient temperature, there will be a flow of heat from the product to the external air. Journals pdf frontiers in heat pipes fhp bendable heat pipes. Gian brochure introduction to heat pipe science and. The vapor pressure decreases as it flows from the evaporator to the condenser. They have found widespread application, ranging from microelectronics cooling in computers and satellites to largescale waste heat recovery in various industries and power stations. There are several limits that govern heat pipe theory, however in terrestrial applications the capillary limit is the most limiting factor.

Heat pipes are highly efficient conductors of heat and can transport, in some cases, s times better than a solid copper conductor. Explore heat pipe with free download of seminar report and ppt in pdf and doc format. General heat pipe structure the advantages of heat pipes are best realized when they are long and thin, that is, take the form of long cylinders or extended thin planar structures. Heat tracing is a method to provide the supplemental heat just enough to compensate for the heat loss due to lower ambient temperature. Convection heat transfer reading problems 191 198 1915, 1924, 1935, 1947, 1953, 1969, 1977 201 206 2021, 2028, 2044, 2057, 2079 introduction in convective heat transfer, the bulk. Grover and his team made extremely important mathematic advances to heat pipe theory, proposed several key applications and coined the term heat pipe. The vapor then travels along the heat pipe to the cold interface. Apr 29, 2016 this section covers the fundamental theory behind the heat pipe based on different research papers and books available at present time in order to open a clear path for reader to design and fabricate their required heat pipe within their applications. The total heat load a heat pipe can carry is a function of total length, evaporator and condenser length, diameter, and orientation with respect to gravity. 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. Heat pipes are referred to as the superconductors of heatdue to their fast transfer capability with low heat loss. The chilled water circulating through the cooling coil tubes, after picking up heat from the mixed air, leaves the cooling coil and goes through the chilled water return chwr pipe to the chillers evaporator. This method has been used in the aerospace industry for about thr ee decades for supporting systemlevel design analysis.

It can heat, do work, sterilize and move over long distances. A rule of thumb for the effective thermal conductivity of a heat pipe is 4000 wmk. 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. At any cross section of the heat pipe, a pressure differential exists between the vapor and liquid phases. 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 general intent of heat tracing is either tracing for winterization andor tracing for. It was also found that the theory could be used to predict evaporator pressure and temperature gradients when the heat pipes were operated at various fractions. Unit operations lab heat exchanger 12 theory notes 1. Heat pipes a novel cooling principle for generator circuit. 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. Heat pipe design handbook, volume 1 internet archive. Install the trace heater in a loop, following illustration e as a guide.

I am trying to model evaporationcondensation phenomena in 2daxisymmetry heat pipe with vof multiphase model and global courant no. The modules listed in the overview are linked to the corresponding pages. Heat pipes and its applications lunds tekniska hogskola. Heat pipes are even cooling satellites electronics in zero gravity orbit. Working fluids, wick configurations, reservoirs, and pipe materials are dealt with, and cleaning, assembly, evacuation, charging, and closure of hp are covered. Heat pipe design and technology modern applications for. 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. Industrial applications where steam is often used include power, heatingcooling, tires, paper, food and beverage, wood products, pharmaceutical, refining and chemical. Capillary action, sonic limitation, entrainment limitation, boiling. Allows direct contact with heat source 1piece vapor chamber 10mm bend radius along. 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. In this chapter we will examine the basic theory of heat exchangers.

University of america for her endless support in obtaining few documents from the. Advanced cooling technologies yale eastman currently a director of act, a few years later describes the theory and history of the heat pipe technology in an article published in scientific american, may 1968. Subscripts h and c refer to the hot and cold fluids, respectively, and subscripts i and o refer to the inlet and outlet of the heat exchanger, respectively. 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. The interior of the pipe is covered with a wick, and the pipe is partially filled with a liquid such as water. Pdf the heat pipe is one of the remarkable achievements of. A heat pipe is a heat transfer device that combines the principles of both thermal conductivity and phase transition to effectively transfer heat between two solid interfaces at the hot interface of a heat pipe a liquid in contact with a thermally conductive solid surface turns into a vapor by absorbing heat from that surface. Insulated pipe supports do not require additional length of trace heater. To heat a cooler fluid by means of a hotter fluid 2. There are many types of heat exchangers applied in the process industry.

Thermomechanical design and characterization of flexible. A procedures manual was created for the double pipe heat exchanger. Heat exchangers 73 individual thermal resistances of the system. For uninsulated pipe supports, allow twice the length of the support, plus an additional 40 cm of trace heater. Heat pipes a novel cooling principle for generator. Tm in a concentric tube heat exchanger, the equations for calculating the performance characteristics heat power emitted, heat power absorbed, heat power lost, efficiency, logarithmic mean temperature difference, and overall heat transfer coefficient are contained in chapter 3.

R sekulib university of kentucky introduction a heat exchanger is a device that is used for transfer of thermal energy enthalpy between two or more fluids, between a solid surface and a fluid, or between solid particulates and a. The operating principles of heat pipes hp are expounded, along with a discussion of different types of hp, and the underlying theory, design, and fabrication of hp. This portable document format \ pdf \ file contains bookmarks, thumbnails, and hyperlinks to help you navigate through the document. Chapter 5 heat exchangers faculty of engineering and. Heat pipe science and technology, an international journal is encompassed on publish ing i fundamental studies of heat and mass transfer in heat pipes and twophase thermo syphons, ii new streams of technology development, iii industrial innovation in elec. South african heat pipe association solar water heating theory, 24 oct 2008, stias, stellenbosch thermosyphon solar water heating system how does it work. In this section we will briefly describe the basic working principle and the performance limits of heat pipes. Heat pipe 1piece vapor chamber 2piece vapor chamber 20 heat pipes bend radius 3x diameter of heat pipe. It is a vacuum tight device consisting of an envelope, a working fluid, and a wick structure. Also explore the seminar topics paper on heat pipe with abstract or synopsis, documentation on advantages and disadvantages, base paper presentation slides for ieee final year mechanical engineering me or production automobile students for the year 2019 2020. The result is less pumping of the wick with reduced heat transfer. Beginning with a definition of the problem, including the temperature. As with any design process, many of the decisions that must be taken are interrelated and the process is iterative. 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 drastically reduced due to the extra thermal resistances added by the bonding.

Steam generator to generate steam at constant pressure. Convection heat transfer microelectronics heat transfer. A heat exchanger is a component that allows the transfer of heat from one fluid liquid or gas to another fluid. Further, a cfd simulation of a wickless heat pipe that considers all the details of heat transfer phenomena inside the heat pipe has not yet been. Thermal conductivity of the heat pipe according to the circuitbreaker standards the maximum acceptable temperature rise at the main contacts is 65 k. Analysis of heat transfer and flow patterns in a loop heat pipe.

Pdf thermal performance of cylindrical heat pipe using. Flanges can be added on the outer surface for easy integration with instruments or radiators the flange is an integral part of the extrusion. Heat pipes and twophase thermosyphons are highly efficient heat transfer elements which utilize liquidvapour phase change latent heat transport. The basic idea behind a heat pipe is the circular process shown. Heat pipe principle it is not within the scope of the article to go into details of heat pipe theory.

Circular process of a heat pipe at the heat source the cold liquid is evaporated, the hot vapor flow is afterwards transported to the heat sink where the vapor condensates again and is transported back to the heat source. Standard heat pipe problem statement selection of working. It can be used practically in heat transfer for a relatively short time andor in a relatively thick material the governing equation with no bulk flow and no heat generation is the boundary conditions are the initial condition is 2 2 x t t t t x 0 t s t x t i t t 0 t i. A widely used concept here is the conduction shape factor, s, which for a buried pipe takes the form. Printed in great britain theory of the ultimate heat transfer limit of cylindrical heat pipes c. However, there are limited studies on the validation of predictions for modelling closed twophase thermosyphons or wickless heat pipes. Furthermore, even if the size, shape, temperature and materials of a heat pipe are specified, the mass, vapor volume fraction, thermal conductance and maximum heat flux are individually through not independently under the control of the designer. This new edition has been revised to include new information on the underlying. Heat pipe theory and practice 1976 edition open library. Heat exchangers are devices used to transfer heat between two or more. For example, choice of the wick and case material eliminates many candidate working fluids often including water due to compatibility constraints.

Pdf basic principles of heat pipes and history researchgate. This book provides a practical study of modern heat pipe engineering, discussing how it can be optimized for use on a wider scale. A loop heat pipe with coherent pores integrated to the heat source is considered as a calculation model in this paperfig. Erickson living installs hpts passive dehumidification systems at many of their facilities, saving thousands of. Custom heat pipe designs act advanced cooling technologies. Efficient heat transferefficient heat transfer boiling and condensationboiling and condensation small temperature difference between the heat source and. Heat transfer in a buried pipe university of reading.

This formulation leads to some unphysical heat transfer properties at the surface when both pipe and surface boundary temperatures are constant. 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 theory was based on the results of experiments similar to that illustrated in figure 1. When selecting the diameter and length of heat pipe it is important to consider the orientation with respect to gravity. Jun 18, 20 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. The amount of heat transfer decrease depends on the particular heat pipe. Text headings in each module are linked to and f\ rom the table of contents for that module. In the short heat pipe extreme 34 length, this effect is nearly zero, so please consult with wakefieldvette engineers to find the right solution for your application. At this stage the student can begin to apply knowledge of mathematics and computational methods to the problems of heat transfer. As shown in figure 1, the heat input vaporizes the liquid working fluid inside the wick in the evaporator section. Combining each of these resistances in series gives.

Haringx 10 modeled the bellow as the combination of annular plates connected by elastic cylinders and derived. Heat pipes heat transport limit for proper heat pipe operation, the total pressure drop must not exceed its capillary pressure head. To reduce the temperature of a hot fluid by means of a cooler fluid 3. Here it gives up the heat into the refrigeration system. Kaya and goldak 5 reported the boiling limit of loop heat pipe obtained. 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. Different heat pipes were developed as an outcome of experimental and theoretical studies of various configurations of the evaporator, condenser and adiabatic. Transports heat from a heat source to a heat sink works as an isothermalizer why twophase thermal system.