scholarly journals Experimental Set up of Two Closed Loop Pulsating Heat Pipe (CLPHP) with Water base Fluids

2019 ◽  
Vol 8 (12S) ◽  
pp. 715-719
Keyword(s):  
Thermal Resistance ◽  
Heat Pipe ◽  
Heat Dissipation ◽  
Heat Pipes ◽  
Heat Fluxes ◽  
Working Fluid ◽  
Water Mixture ◽  
Working Fluids ◽  
Pure Fluids ◽  
Acetone Water

Heat pipes are deliberated to be effective heat dissipation devices compared to other types of heat sinks due to their high effective thermal conductivity. Because of the flexibility in the design and layout of heat pipe turns along the heat source, pulsating heat pipes have gained popularity. One of the parameters that have the mainimpact on the presentation of CLPHP is the thermo physical properties of the working fluid. The properties of the working fluid affect the temperature difference between the evaporator and the condenser which in turn affect the thermal resistance of the CLPHP. In this connection, the influence of different working fluids is experimentally investigated on a two loop CLPHP, varying the evaporator heat flux. Pure fluids, viz., water, acetone, benzene and binary mixture, viz., Acetone-water and Benzene-water are utilized on working fluids. The heat input considered at the evaporator is 32W, 48W and 60W. The filling ratio is kept as 50 %. The results show that among the working fluids considered for the study, acetone exhibits least thermal resistance among the pure fluids at all heat fluxes considered in the analysis, while Acetone-water mixture has exhibited least thermal resistance among the water based mixtures.

An Experimental Study of Mesh Type Flat Heat Pipes

2011 ◽  
Vol 27 (2) ◽  
pp. 167-176 ◽  
Author(s):  
L.-H. Chien ◽  
Y.-C. Shih
Keyword(s):  
Thermal Resistance ◽  
Heat Pipe ◽  
Inclination Angle ◽  
Volume Fraction ◽  
Mesh Size ◽  
Heat Pipes ◽  
Working Fluid ◽  
Internal Space ◽  
Horizontal Orientation ◽  
Semi Empirical

ABSTRACTFlat heat pipes having mesh capillaries were investigated experimentally in this study. An apparatus was designed to test thermal performance of plate type copper water heat pipe having one or two layers of #50 or #80 mesh capillary structures with 5 to 50 W heat input. The working fluid, water, is charged in volumes equivalent to 25%, 33%, or 50% of the internal space. In addition to horizontal orientation, heat pipes were tested with the evaporator section elevated up to 40 degree inclination angle. Temperature distribution of the heat pipe was measured, and the evaporator, adiabatic and condensation resistances were calculated separately. The effects of mesh size, charge volume fraction, and inclination angle on thermal resistance were discussed. In general, the #80 mesh yielded lower thermal resistance than the #50 mesh. Inclination angle has a more significant effect on condenser than evaporator. Analysis of evaporation and condensation in flat heat pipes was conducted and semi-empirical correlations were derived. The present evaporation correlation predicts evaporation resistance between −20% and +30%, and the condensation correlation predicts most condensation resistance data within ±30% for 25% and 33% charge volume fraction.

High Flux Value Micro-Heat Pipe Arrays

2010 ◽  
Vol 2010 (DPC) ◽  
pp. 001760-001807
Author(s):  
Daniel K. Harris ◽  
Robert Dean ◽  
Ashish Palkar ◽  
Gary Wonacott
Keyword(s):  
Liquid Metal ◽  
Heat Pipe ◽  
Experimental Work ◽  
Performance Enhancement ◽  
Performance Testing ◽  
Heat Pipes ◽  
Working Fluid ◽  
Working Fluids ◽  
Micro Heat Pipe ◽  
Micro Heat Pipes

The concept of heat pipes was introduced by R.S.Gaugler in 1940s and Cotter first introduced the idea of “micro” heat pipes in 1984. Cotter in his paper, defined the micro heat pipe as being one in which the mean curvature of the vapor-liquid interface is comparable in magnitude to the reciprocal of the hydraulic radius of the total flow channel. The Micro Heat Pipes (MHPs) work efficiently through the use of two-phase heat transfer. Various working fluids have been tried in combination with various substrate materials. In this experimental work the main focus was to study the behavior of liquid metal filled MHPs made from silicon as the substrate material. Specially designed MHPs were assembled and charged with mercury as the working fluid. A special test setup was designed and built for the experimental work and the response of the MHPs to the controlled increment in the input power is presented. A number of experiments were carried out on the specimen MHPs to determine their effective thermal conductivity, the variation of the temperature along the axial length and the performance enhancement factor. Effective thermal conductivities as high as 900 W/m-K with a silicon equivalence of 6 were achieved with the liquid metal MHP. Based on the results from the various performance testing parameters, it was observed that the liquid metal charged MHPs performed substantially better than conventional MHPs filled with organic working fluids. The limitations and the possible methods of improving the performance of the MHPs are discussed.

Experimental investigation of a loop heat pipe with R245fa and R1234ze (E) as working fluids

2021 ◽  
pp. 1-17
Author(s):  
Guangming Xu ◽  
Rongjian Xie ◽  
Nanxi Li ◽  
Cheng Liu
Keyword(s):  
Thermal Resistance ◽  
Heat Pipe ◽  
Characteristic Temperature ◽  
Thermal Characteristics ◽  
Heat Pipes ◽  
Loop Heat Pipe ◽  
Working Fluids ◽  
Loop Heat Pipes ◽  
Heat Transfer Capacity ◽  
Heat Loads

Abstract Two kinds of new refrigerant-R1234ze (E) and R245fa were discussed as substitutes or supplements to traditional working fluids of loop heat pipes based on their favorable thermophysical properties and characteristics such as being safe and environmentally friendly. Thermal characteristics of a loop heat pipe with sintering copper wick at different charging ratios were experimentally investigated under variable heat loads. The results showed that the optimal charging ratio in the loop heat pipe range from 65% to 70%, and at this charging level, the R1234ze(E) system had better start-up response, while the R245fa system presented a stronger heat transfer capacity. The characteristic temperature of R1234ze(E) system was below 35 °C, and the corresponding thermal resistance was 0.08 K/W ~ 1.62 K/W under heat loads ranging from 5 W to 40 W. The thermal resistance of the R245fa system was 0.18 K/W ~ 0.91 K/W under heat loads of 10 W ~ 60 W, and the operating temperature was below 60 °C. The loop heat pipes charged with the proposed new refrigerants exhibit superb performance in room temperature applications, making them beneficial for enhancing the performance of electronics, and could provide a distinctive choice for the cooling of small-sized electronics especially.

Effects of Working Fluid, Fill Ratio and Orientation on Looped and Unlooped Pulsating Heat Pipes

2005 ◽  
Author(s):  
Kathryn Nikkanen ◽  
Christian G. Lu ◽  
Masahiro Kawaji
Keyword(s):  
Heat Pipe ◽  
Rectangular Channel ◽  
Heat Pipes ◽  
High Heat ◽  
Heat Fluxes ◽  
Working Fluid ◽  
Pulsating Heat Pipe ◽  
Fill Ratio ◽  
Triangular Channel ◽  
Horizontal Orientation

Improved miniaturization and a trend towards increasingly dense and compact architectures have led to unmanageably high heat fluxes in electronic components. In order to keep temperatures at operational levels more advanced cooling solutions are being required that go beyond the solid heat sink and forced convection. Pulsating heat pipes made out of multi port extrusion tubing are a proposed solution. Typically, gas-liquid slug flow occurs in the serpentine channel imbedded in the pulsating heat pipe. Vapour is produced in the heated section and condensed in the cooled section located at opposite ends of the heat pipe. In this work, experiments were conducted on four Multi-Port Extruded (MPE) aluminum tubing heat pipes with different internal structures: rectangular channel looped, rectangular channel unlooped, triangular channel looped, and triangular channel unlooped. The effect of changing the working fluid (ethanol or de-ionized water), fill ratio, and orientation were measured and compared for the different heat pipes. It was found that most of the heat pipes performed better with ethanol than de-ionized water. Only the looped rectangular channel heat pipe performed satisfactorily with de-ionized water, which is attributed both to the larger channel size and the looped architecture. The unlooped heat pipes performed best at the lowest fill ratios (10%) while the looped heat pipes showed their best performances between 30 and 50% with marked decrease at the lower and higher fill ratios. Both looped heat pipes performed poorly in horizontal orientation as compared to vertical, however, the unlooped heat pipes performed quite well in both orientations. This may be more the effect of the fill ratio on horizontal performance as literature suggests that horizontal orientation requires a lower fill ratio to perform satisfactorily.

Experimental Investigation and Performance Evaluation of a Multi Turn Closed Loop Pulsating Heat Pipe

2014 ◽  
Vol 592-594 ◽  
pp. 1554-1558 ◽  
Author(s):  
N. Narendra Babu ◽  
Rudra Naik
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Thermal Resistance ◽  
Transfer Coefficient ◽  
Heat Pipe ◽  
Closed Loop ◽  
Experimental Result ◽  
Working Fluid ◽  
Pulsating Heat Pipe ◽  
Working Fluids

Pulsating heat pipe (PHP) is a passive heat transfer device, which transfers heat from one region to another with exceptional heat transfer capacity. It utilizes the latent heat of vaporization of the working fluid as well as the sensible heat. As a result, the effective thermal conductivity is higher than that of the conductors. An experimental study on three turn closed loop pulsating heat pipe with three different working fluids viz., Acetone, Methanol, Heptane and distilled water were employed. The PHP is made up of brass material with an inner diameter of 1.95mm, with a total length of 1150 mm for different fill ratios (FR) was employed .The PHP is tested for the thermal resistance and the heat transfer coefficient. The experimental result strongly demonstrates that acetone is a better working fluid among the working fluids considered in terms of higher heat transfer coefficient and lower thermal resistance.

Testing the Thermal Resistance and Power Capacity of Production Heat Pipes

2005 ◽  
Author(s):  
Sukhvinder Kang ◽  
Randy Cook ◽  
Dave Gailus
Keyword(s):  
Thermal Resistance ◽  
Specific Heat ◽  
Heat Pipe ◽  
Heat Transport ◽  
Manufacturing Process ◽  
Heat Pipes ◽  
Test Method ◽  
Heat Sinks ◽  
Working Fluid ◽  
Transport Capacity

In recent years heat pipes have become widely use in high performance air-cooled heat sinks for cooling electronics equipment. Such heat sinks rely on the heat pipes to collect heat from small high heat flux sources, transport it over some distance, and spread the heat efficiently to a volume of fins where the heat is transferred to an air flow stream by convection. When used effectively, heat pipes enable heat sinks that have low thermal resistance and low mass. For the heat sink to be successful, the heat pipes must also have sufficient heat transport capacity. To deliver their design thermal resistance and heat transport capacity, heat pipes need to be manufactured with well-controlled wick characteristics, working fluid fill volume and minimal residual non-condensable gases. It is standard procedure for heat pipe manufacturing companies to test 100 percent of the heat pipes they manufacture. The most commonly used production test is designed to rapidly show whether or not a heat pipe functions as a heat pipe. On a sampling basis, manufacturers also test the heat transport capacity of their heat pipes. There is no rapid test that can verify that any specific heat pipe will achieve the desired operational life — this is achieved by validation of the manufacturing process and adequate manufacturing process controls. In this paper we describe a test method and apparatus that can be used to rapidly test whether a heat pipe has the required thermal resistance at the specified heat transport capacity. The apparatus is capable of testing heat pipes over a wide range of diameters and lengths in their end use configuration (with bends and flattened regions). The key design criteria for the test apparatus is described and test data for several application specific heat pipes is presented.

Effect of Concentration and Loading Fluid of Nanofluids on the Thermal Resistance of Sintered Powder Wick Heat Pipe

2013 ◽  
Vol 651 ◽  
pp. 728-735 ◽  
Author(s):  
Nandy Putra ◽  
Wayan Nata Septiadi ◽  
Ridho Irwansyah
Keyword(s):  
Thermal Resistance ◽  
Heat Pipe ◽  
Fluid Transport ◽  
Heat Pipes ◽  
Alternative Methods ◽  
Working Fluid ◽  
Cooling Systems ◽  
Sintered Copper ◽  
Sintered Powder ◽  
Flow Features

Heat pipes have been widely used as one of the alternative methods to absorb more heat in the cooling systems of electronic devices. One of the ways to improve the thermal performance of heat pipes is to change the fluid transport properties and flow features of working fluids using nanofluids. The purpose of this research was to investigate the effect of Al2O3-water nanofluids concentration and fluid loading to the thermal resistance between evaporator and adiabatic section of copper straight sintered copper powder wick heat pipe. In this research, sintered powder wick heat pipes were manufactured and tested to determine the thermal resistance of the sintered powder wick heat pipes which charged with water and Al2O3-water nanofluids. The concentrations of the nanoparticles were varied from 1 %, 3% and 5 % of the volume of the base fluid. The result shows that Al2O3-water nanofluids have the ability to reduce the temperature at the evaporator section and the thermal resistance of heat pipe. The increase in nanofluids concentration could give significant effect to reduce the thermal resistance of heat pipes. The amount of working fluid charged into the heat pipes also gives an effect in heat pipes thermal resistance, where the thermal resistance was lower when the heat pipe was charged with 60% of its volume. The formation of coating layer at sintered powder wick also can fixed the wick porosity and cause roughness on the surface of granular pore which the increased of capillary could give the effect for enhancement of heat pipe performance.

scholarly journals PERFORMANCE OF HEAT PIPE FOR DIFFERENT WORKING FLUIDS AND FILL RATIOS

2011 ◽  
Vol 41 (2) ◽  
pp. 96-102 ◽  
Author(s):  
A. K. Mozumder ◽  
A. F. Akon ◽  
M. S. H. Chowdhury ◽  
S. C. Banik
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Thermal Resistance ◽  
Transfer Coefficient ◽  
Heat Pipe ◽  
Thermal Capacity ◽  
Working Fluid ◽  
Working Fluids ◽  
Overall Heat Transfer Coefficient ◽  
Lower Temperature

An attempt is made to design, fabricate and test a miniature heat pipe with 5 mm diameter and 150 mm length with a thermal capacity of 10 W. Experiments were conducted with and without working fluid for different thermal loads to assess the performance of heat pipe. The working fluids chosen for the study were same as those commonly used namely, water, methanol and acetone. The temperature distribution across the heat pipe was measured and recorded using thermocouples. The performance of the heat pipe was quantified in terms of thermal resistance and overall heat transfer coefficient. The amount of liquid filled was varied and the variation of the performance parameters for varying liquid inventory is observed. Finally, optimum liquid fill ratio is identified in terms of lower temperature difference and thermal resistance and higher heat transfer coefficient. The data reported in this study will serve as a good database for the researchers in this field. Overall heat transfer coefficient of the Miniature heat pipe is found to be the maximum for the Acetone as working fluid.DOI: http://dx.doi.org/10.3329/jme.v41i2.7473

scholarly journals Numerical Study on the Effects of using Nanofluids in Pulsating Heat Pipe

2018 ◽  
Vol 7 (4.35) ◽  
pp. 204
Author(s):  
M. Zufar ◽  
P. Gunnasegaran ◽  
Ng K. Ching
Keyword(s):  
Thermal Resistance ◽  
Heat Pipe ◽  
Thermal Performance ◽  
Heat Transfer Performance ◽  
Numerical Study ◽  
Constant Heat Flux ◽  
Working Fluid ◽  
Pulsating Heat Pipe ◽  
Working Fluids ◽  
Resistance Value

Pulsating Heat Pipe (PHP) is the next generation heat pipe that has a prospect in improving the heat transfer performance. The type of working fluid use in the PHP has a direct influence on the thermal performance. Incorporating nanofluid in PHP may greatly increase its thermal performance as compared to using base fluid (water). The current work focuses on the simulations of 2-dimensional flows in PHP using working fluids such as diamond, silver (Ag), silica oxide (SiO2) nanofluids and water. Constant heat flux and filling ratio of 50% were used throughout the study. From the results, it was found out that diamond nanofluid has the lowest thermal resistance value as compared to other working fluids. The effect of the number of PHP turns was studied and it was discovered that higher number of turns would produce lower thermal resistance value.

scholarly journals Effect of Pure and Binary Fluids on Thermal Performance of Closed Loop Pulsating Heat Pipe

2020 ◽  
Vol 9 (3) ◽  
pp. 1716-1721
Keyword(s):  
Heat Transfer ◽  
Thermal Resistance ◽  
Heat Pipe ◽  
Closed Loop ◽  
Outer Diameter ◽  
Pulsating Heat Pipe ◽  
Binary Fluids ◽  
Working Fluids ◽  
Source To Sink ◽  
Acetone Water

Pulsating heat pipe is the raising methodology of cooling systems in many areas. CLPHP is a passive mode of phase change heat transfer device having potential to transfer heat from source to sink in less span. Heat transfer performance of this method is improving day by day as giving less thermal resistance. Number of experimentations are conducting to increase the efficiency of pulsating heat pipes in many aspects i.e. varying lengths, working fluids, number of turns, different fill ratios, heat inputs and orientation. As taking part of these research a five turn closed loop pulsating heat pipe (of tube inner diameter 2mm, outer diameter 3mm; adiabatic section length 170mm, condensation section length is50mm, evaporation section length is 42mm) working with pure and binary fluids (water-acetone, water-ethanol) compared with water, Acetone, Ethanol with heat inputs 20w, 40w, 60w, 80w, and fill ratio 50%, also the orientations are horizontal and vertical. The analysis from the results obtained was the thermal resistance of all working fluids is drastically diminishing from 20w to 40w heat input and slowly from 40w to 80w.

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