Journal articles: 'Micro heat pipe'

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Chang, Fun Liang, and Yew Mun Hung. "Circulation Effectiveness of Working Fluid in Inclined Micro Heat Pipes." Applied Mechanics and Materials 789-790 (September 2015): 422–25. http://dx.doi.org/10.4028/www.scientific.net/amm.789-790.422.

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Micro heat pipe is a two-phase heat transfer device offering effective high heat-flux removal in electronics cooling. Essentially, micro heat pipe relies on the phase change processes, namely evaporation and condensation, and the circulation of working fluid to function as heat transfer equipment. The vast applications of micro heat pipe in portable appliances necessitate its functionality under different orientations with respect to gravity. Therefore, its thermal performance is strongly related to its orientation. By incorporating solid wall conduction, together with the continuity, momentum, and energy equations of the working fluid, a mathematical model is developed to investigate the heat and fluid flow characteristics of inclined micro heat pipes. We investigate both the favorable and adverse effects of gravity on the circulation rate which is intimately related to the thermal performance of micro heat pipes. The effects of gravity, through the angle of inclination, on the circulation strength and heat transport capacity are analysed. This study serves as a useful analytical tool in the micro heat pipe design and performance analysis, associated with different inclinations and operating conditions.

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ZHANG, JIN, STEPHEN J. WATSON, and HARRIS WONG. "Fluid flow and heat transfer in a dual-wet micro heat pipe." Journal of Fluid Mechanics 589 (October 8, 2007): 1–31. http://dx.doi.org/10.1017/s0022112007007823.

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Micro heat pipes have been used to cool micro electronic devices, but their heat transfer coefficients are low compared with those of conventional heat pipes. In this work, a dual-wet pipe is proposed as a model to study heat transfer in micro heat pipes. The dual-wet pipe has a long and narrow cavity of rectangular cross-section. The bottom-half of the horizontal pipe is made of a wetting material, and the top-half of a non-wetting material. A wetting liquid fills the bottom half of the cavity, while its vapour fills the rest. This configuration ensures that the liquid–vapour interface is pinned at the contact line. As one end of the pipe is heated, the liquid evaporates and increases the vapour pressure. The higher pressure drives the vapour to the cold end where the vapour condenses and releases the latent heat. The condensate moves along the bottom half of the pipe back to the hot end to complete the cycle. We solve the steady-flow problem assuming a small imposed temperature difference between the two ends of the pipe. This leads to skew-symmetric fluid flow and temperature distribution along the pipe so that we only need to focus on the evaporative half of the pipe. Since the pipe is slender, the axial flow gradients are much smaller than the cross-stream gradients. Thus, we can treat the evaporative flow in a cross-sectional plane as two-dimensional. This evaporative motion is governed by two dimensionless parameters: an evaporation number E defined as the ratio of the evaporative heat flux at the interface to the conductive heat flux in the liquid, and a Marangoni number M. The motion is solved in the limit E→∞ and M→∞. It is found that evaporation occurs mainly near the contact line in a small region of size E−1W, where W is the half-width of the pipe. The non-dimensional evaporation rate Q* ~ E−1 ln E as determined by matched asymptotic expansions. We use this result to derive analytical solutions for the temperature distribution Tp and vapour and liquid flows along the pipe. The solutions depend on three dimensionless parameters: the heat-pipe number H, which is the ratio of heat transfer by vapour flow to that by conduction in the pipe wall and liquid, the ratio R of viscous resistance of vapour flow to interfacial evaporation resistance, and the aspect ratio S. If HR≫1, a thermal boundary layer appears near the pipe end, the width of which scales as (HR)−1/2L, where L is the half-length of the pipe. A similar boundary layer exists at the cold end. Outside the boundary layers, Tp varies linearly with a gradual slope. Thus, these regions correspond to the evaporative, adiabatic and condensing regions commonly observed in conventional heat pipes. This is the first time that the distinct regions have been captured by a single solution, without prior assumptions of their existence. If HR ~ 1 or less, then Tp is linear almost everywhere. This is the case found in most micro-heat-pipe experiments. Our analysis of the dual-wet pipe provides an explanation for the comparatively low effective thermal conductivity in micro heat pipes, and points to ways of improving their heat transfer capabilities.

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Gou, Xiang, Qiyan Zhang, Yamei Li, Yingfan Liu, Shian Liu, and Saima Iram. "Experimental Research on the Thermal Performance and Semi-Visualization of Rectangular Flat Micro-Grooved Gravity Heat Pipes." Energies 11, no. 9 (September 18, 2018): 2480. http://dx.doi.org/10.3390/en11092480.

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To strengthen the heat dissipating capacity of a heat pipe used for integrated insulated gate bipolar transistors, as an extension of our earlier work, the effect of micro-groove dimension on the thermal performance of flat micro-grooved gravity heat pipe was studied. Nine pipes with different depths (0.4 mm, 0.8 mm, 1.2 mm) and widths (0.4 mm, 0.8 mm, 1.2 mm) were fabricated and tested under a heating load range from 80 W to 180 W. The start-up time, temperature difference, relative thermal resistance and equivalent thermal conductivity were presented as performance indicators by comparison of flat gravity heat pipes with and without micro-grooves. Results reveal that the highest equivalent thermal conductivity of the flat micro-grooved gravity heat pipes is 2.55 times as that of the flat gravity heat pipe without micro-grooves. The flat gravity heat pipes with deeper and narrower micro-grooves show better thermal performance and the optimal rectangular micro-groove dimension among the selected options is determined to be 1.2 mm (depth) × 0.4 mm (width). Furthermore, the liquid–vapor phase behaviors were observed to verify the heat transfer effects and analyze the heat transfer mechanism of the flat micro-grooved heat pipes.

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Swanson, L. W., and G. P. Peterson. "The Interfacial Thermodynamics of Micro Heat Pipes." Journal of Heat Transfer 117, no. 1 (February 1, 1995): 195–201. http://dx.doi.org/10.1115/1.2822303.

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Successful analysis and modeling of micro heat pipes requires a complete understanding of the vapor–liquid interface. A thermodynamic model of the vapor–liquid interface in micro heat pipes has been formulated that includes axial pressure and temperature differences, changes in local interfacial curvature, Marangoni effects, and the disjoining pressure. Relationships were developed for the interfacial mass flux in an extended meniscus, the heat transfer rate in the intrinsic meniscus, the “thermocapillary” heat-pipe limitation, as well as the nonevaporating superheated liquid film thickness that exists between adjacent menisci and occurs during liquid dry out in the evaporator. These relationships can be used to define quantitative restrictions and/or requirements necessary for proper operation of micro heat pipes. They also provide fundamental insight into the critical mechanisms required for proper heat pipe operation.

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Yang, Yan Xia, Xiao Dong Wang, Yi Luo, and Liang Liang Zou. "Heat Transfer Characteristic of Flat Trapezoid Grooved Micro Heat Pipes." Key Engineering Materials 609-610 (April 2014): 1526–31. http://dx.doi.org/10.4028/www.scientific.net/kem.609-610.1526.

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To study the heat transfer performance of micro heat pipe, theoretical analysis of flat plate micro heat pipe with trapezoid cross section are presented in this paper. A one-dimensional stationary mathematical model for micro heat pipe grooved capillary flow using finite volume method (FVM) was established. The micro heat pipe had vapor space connect with each other and the influences of shear stress between vapor and fluid in the working process were described in the model which made the model more precisely. The axial variation of working fluid distribution in the heat pipe, pressure difference between vapor and liquid, and velocity of vapor and liquid were analyzed. In addition, the maximum heat transport capacity of micro heat pipe was calculated. The simulation results showed good agreement with the experiment results, and it could predict the heat transfer performance accurately, which was useful to micro heat pipe structural design.

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Peterson, G. P., and H. B. Ma. "Temperature Response of Heat Transport in a Micro Heat Pipe." Journal of Heat Transfer 121, no. 2 (May 1, 1999): 438–45. http://dx.doi.org/10.1115/1.2825997.

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A detailed mathematical model for predicting the heat transport capability and temperature gradients that contribute to the overall axial temperature drop as a function of heat transfer in a micro heat pipe has been developed. The model utilizes a third-order ordinary differential equation, which governs the fluid flow and heat transfer in the evaporating thin film region; an analytical solution for the two-dimension heat conduction equation, which governs the macro evaporating film region in the triangular corners; the effects of the vapor flow on the liquid flow in the micro heat pipe; the flow and condensation of the thin film caused by the surface tension in the condenser; and the capillary flow along the axial direction of the micro heat pipe. With this model, the temperature distribution along the axial direction of the heat pipe and the effect on the heat transfer can be predicted. In order to verify the model presented here, an experimental investigation was also conducted and a comparison with experimental data made. This comparison indicated excellent correlation between the analytical model and experimental results, and as a result, the analysis provides a better understanding of the heat transfer capability and temperature variations occurring in micro heat pipes.

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Longtin, J. P., B. Badran, and F. M. Gerner. "A One-Dimensional Model of a Micro Heat Pipe During Steady-State Operation." Journal of Heat Transfer 116, no. 3 (August 1, 1994): 709–15. http://dx.doi.org/10.1115/1.2910926.

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Micro heat pipes are small structures that will be used to cool microscale devices. They function much like their conventional counterparts, with a few exceptions, most notably the absence of a wick. It is expected that water-filled micro heat pipes will be able to dissipate heat fluxes on the order of 10–15 W/cm2 (100,000–150,000 W/m2). This work addresses the modeling of a micro heat pipe operating under steady-state conditions. A one-dimensional model of the evaporator and adiabatic sections is developed and solved numerically to yield pressure, velocity, and film thickness information along the length of the pipe. Interfacial and vapor shear stress terms have been included in the model. Convection and body force terms have also been included in the momentum equation, although numerical experiments have shown them to be negligible. Pressure, velocity, and film thickness results are presented along with the maximum heat load dependence on pipe length and width. Both simple scaling and the model results show that the maximum heat transport capability of a micro heat pipe varies with the inverse of its length and the cube of its hydraulic diameter, implying the largest, shortest pipes possible should be used.

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8

Li, Xi Bing, Z. M. Shi, S. G. Wang, Q. M. Hu, L. Bao, and H. J. Zhang. "Analysis of Structural Parameters of Grooved-Wicksin Micro Heat Pipes Based on Capillary Limits." Key Engineering Materials 499 (January 2012): 21–26. http://dx.doi.org/10.4028/www.scientific.net/kem.499.21.

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For great progress in heat pipe technology, a micro heat pipe has become an ideal heat dissipating device in high heat-flux electronic products, and capillary limit is the main factor affecting its heat transfer performance. Based on analyses of capillary limit and currently commonly-used groove structures, this paper built capillary limit models for micro heat pipes with dovetail-groove, rectangular-groove, trapezoidal-groove and V-groove wick structures respectively for theoretical analyses. The analysis results show that better heat transfer performances can be obtained in micro heat pipes with small-angle dovetail (i.e. a sector structure), rectangular and small-angle trapezoidal grooved wick structures when groove depth is 0.2-0.3mm and top-width-to-depth ratio is 1.2-1.5.

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9

Peterson, G. P., A. B. Duncan, and M. H. Weichold. "Experimental Investigation of Micro Heat Pipes Fabricated in Silicon Wafers." Journal of Heat Transfer 115, no. 3 (August 1, 1993): 751–56. http://dx.doi.org/10.1115/1.2910747.

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An experimental investigation was conducted to determine the thermal behavior of arrays of micro heat pipes fabricated in silicon wafers. Two types of micro heat pipe arrays were evaluated, one that utilized machined rectangular channels 45 μm wide and 80 μm deep and the other that used an anisotropic etching process to produce triangular channels 120 μm wide and 80 μm deep. Once fabricated, a clear pyrex cover plate was bonded to the top surface of each wafer using an ultraviolet bonding technique to form the micro heat pipe array. These micro heat pipe arrays were then evacuated and charged with a predetermined amount of methanol. Using an infrared thermal imaging unit, the temperature gradients and maximum localized temperatures were measured and an effective thermal conductivity was computed. The experimental results were compared with those obtained for a plain silicon wafer and indicated that incorporating an array of micro heat pipes as an integral part of semiconductor devices could significantly increase the effective thermal conductivity; decrease the temperature gradients occurring across the wafer; decrease the maximum wafer temperatures; and reduce the number and intensity of localized hot spots. At an input power of 4 W, reductions in the maximum chip temperature of 14.1°C and 24.9°C and increases in the effective thermal conductivity of 31 and 81 percent were measured for the machined rectangular and etched triangular heat pipe arrays, respectively. In addition to reducing the maximum wafer temperature and increasing the effective thermal conductivity, the incorporation of the micro heat pipe arrays was found to improve the transient thermal response of the silicon test wafers significantly.

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Kang, Shung-Wen, Sheng-Hong Tsai, and Ming-Han Ko. "Metallic micro heat pipe heat spreader fabrication." Applied Thermal Engineering 24, no. 2-3 (February 2004): 299–309. http://dx.doi.org/10.1016/j.applthermaleng.2003.08.008.

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11

Ha, J. M., and G. P. Peterson. "The Heat Transport Capacity of Micro Heat Pipes." Journal of Heat Transfer 120, no. 4 (November 1, 1998): 1064–71. http://dx.doi.org/10.1115/1.2825891.

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The original analytical model for predicting the maximum heat transport capacity in micro heat pipes, as developed by Cotter, has been re-evaluated in light of the currently available experimental data. As is the case for most models, the original model assumed a fixed evaporator region and while it yields trends that are consistent with the experimental results, it significantly overpredicts the maximum heat transport capacity. In an effort to provide a more accurate predictive tool, a semi-empirical correlation has been developed. This modified model incorporates the effects of the temporal intrusion of the evaporating region into the adiabatic section of the heat pipe, which occurs as the heat pipe approaches dryout conditions. In so doing, the current model provides a more realistic picture of the actual physical situation. In addition to incorporating these effects, Cotter’s original expression for the liquid flow shape factor has been modified. These modifications are then incorporated into the original model and the results compared with the available experimental data. The results of this comparison indicate that the new semiempirical model significantly improves the correlation between the experimental and predicted results and more accurately represents the actual physical behavior of these devices.

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12

Peterson, G. P., and A. K. Mallik. "Transient Response Characteristics of Vapor Deposited Micro Heat Pipe Arrays." Journal of Electronic Packaging 117, no. 1 (March 1, 1995): 82–87. http://dx.doi.org/10.1115/1.2792072.

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The transient thermal response of vapor deposited micro heat pipe arrays fabricated as an integral part of silicon wafers was measured to determine if these arrays could be used to reduce the local temperature gradients and improve the reliability of semiconductor devices. Wafers with arrays of 34 and 66 micro heat pipes were evaluated using an IR thermal imaging system in conjunction with a VHS video recorder. These arrays occupied 0.75 and 1.45 percent, of the wafer cross-sectional area, respectively. The wafers with micro heat pipe arrays demonstrated a 30 to 45 percent reduction in the thermal time constant when compared to that obtained for plain silicon wafers. This reduction in response time was shown to lead to a significant reduction in the maximum wafer temperature, due to the increased effective thermal conductivity caused by the vaporization and condensation occurring in the individual micro heat pipes. The experimental results were then used to validate a transient numerical model, capable of accurately predicting the transient temperature profile and thermal time constant of the wafer/heat pipe combinations.

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13

Mahmood, Lutful, and Razzaq Akhanda. "Experimental study on the performance limitation of micro heat pipes of non circular cross-sections." Thermal Science 12, no. 3 (2008): 91–102. http://dx.doi.org/10.2298/tsci0803091m.

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An experimental study of three different cross-sections (circular, semicircular and rectangular) of micro heat pipes having same hydraulic diameter (D= 3mm) is carried out at three different inclination angles (0?, 45?, 90?) using water as the working fluid. Evaporator section of the pipe is heated by an electric heater and the condenser section is cooled by water circulation in an annular space between the condenser section and the water jacket. Temperatures at different locations of the pipe are measured using five calibrated K type thermocouples. Heat supply is varied using a voltage regulator which is measured by a precision ammeter and a voltmeter. It is found that thermal performance tends to deteriorate as the micro heat pipe is flattened. Thus among all cross-sections of the pipes circular cross-section exhibits the best thermal performance followed by semicircular and rectangular cross-sections. Moreover maximum heat transfer capability of the pipes also decreases with decreasing of its inclination angle. A correlation is developed using all the gathered data of the present study to predict the heat transfer coefficient of micro heat pipes of different cross-sections placed at different inclination angles.

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Li, Xi Bing, Chang Long Yang, Gong Di Xu, Wen Yuan, and Shi Gang Wang. "A Mathematical Modeling Method for Capillary Limit of Micro Heat Pipe with Sintered Wick." Solid State Phenomena 175 (June 2011): 335–41. http://dx.doi.org/10.4028/www.scientific.net/ssp.175.335.

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With heat flux increasing and cooling space decreasing in microelectronic and chemical products, micro heat pipe has become an ideal heat dissipation device in high heat-flux products. Through the analysis of its working principle, the factors that affect its heat transfer limits and the patterns in which copper powders are arrayed in circular cavity, this paper first established a mathematical model for the crucial factors in affecting heat transfer limits in a circular micro heat pipe with a sintered wick, i.e. a theoretical model for capillary limit, and then verified its validity through experimental investigations. The study lays a powerful theoretical foundation for designing and manufacturing circular micro heat pipes with sintered wicks.

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Amjad Ali Pasha, Meshal Nuwaym Al-Harbi, Surfarazhussain S. Halkarni, Nazrul Islam, D. Siva Krishna Reddy, S. Nadaraja Pillai, and Ufaith Qadiri. "CFD study of Convective Heat Transfer of Water Flow Through Micro-Pipe with Mixed Constant Wall Temperature and Heat Flux Wall Boundary Conditions." CFD Letters 13, no. 7 (July 25, 2021): 13–26. http://dx.doi.org/10.37934/cfdl.13.7.1326.

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The dissipation of heat in tiny engineering systems can be achieved with fluid flow through micro pipes. They have the advantage of less volume to large surface ratio convective heat transfer. There are deep-rooted analytical relations for convective heat transfer available for fluid flow through macro size pipes. But differences exist between the convective heat transfer for fluid flow through macro and micro pipes. Therefore, there is a good scope of work in micro convection heat transfer to study the mechanism of fundamental flow physics. There have been studies with either constant heat flux wall boundary conditions or constant wall temperature boundary conditions with constant and variable property flows. In this article, first, the numerical simulations are validated with the experimental data for 2D axisymmetric conventional pipe with pipe diameter of 8 mm is taken with laminar, steady, and single-phase water flows with constant wall heat flux boundary condition of 1 W/cm2. The computed Nusselt number is compared to the experimental results at different Reynolds numbers of 1350, 1600 and 1700. In the next study, three-dimensional micropipe laminar flow is studied numerically using water with an inlet velocity of 3 m/s and pipe diameter of 100 µm. The mixed wall boundary conditions with upper half pipe surface subjecting to constant wall temperature of 313 K and lower half surface subjecting to 100 W/cm2 are used in the simulations. The focus of research would be to consider the effect of temperature-dependent properties like thermal conductivity, viscosity, specific heat, and density (a combined effect we call it as variable properties) on micro-pipe flow characteristics like Nusselt number at mixed wall boundary conditions and compare it with the constant property flows. The conventional pipe showed no significant difference with variable and constant property flows with different Reynolds numbers. On contrary the flow through 3D micropipe shows that the Nusselt number with variable property flows is less as compared to the constant property flows.

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Zhao, Guo Chang, Tian Dong Lu, Li Ping Song, Lei Cao, and Wei Zhang. "Research on the Applications of Heat Pipes in Cooling Aircraft Electrical Equipment." Advanced Materials Research 860-863 (December 2013): 1378–82. http://dx.doi.org/10.4028/www.scientific.net/amr.860-863.1378.

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In order to ensure proper temperatures for electronic equipment and to meet the increasing heat dissipation capacity needs of airborne electronic equipment, a suitable heat-pipe for use in aircraft equipment needs to be found. Considering both the acceleration and the changes in tilt angle of the aircraft, performance analysis of five main types of heat-pipes showed that dual compensation chamber loop heat pipe and micro-channel plate heat pipe were the most suitable for use in airborne electrical equipment.

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17

Peterson, G. P. "Overview of Micro Heat Pipe Research and Development." Applied Mechanics Reviews 45, no. 5 (May 1, 1992): 175–89. http://dx.doi.org/10.1115/1.3119755.

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The concept of a micro heat pipe was first proposed in 1984. Since that time, numerous analytical and experimental investigations have been conducted to determine the fundamental parameters that govern the operation of these devices. Micro heat pipes ranging in size from 1 mm in diameter and 60 mm in length to 30 μm in diameter and 10 mm in length have been analyzed, modelled, and fabricated. The following review describes the historical development of these devices, along with the analytical and numerical techniques used to model and predict their performance and the results of several recent experimental investigations. Because of recent advances in the development of micro heat pipes fabricated as an integral part of semiconductor wafers, particular emphasis has been placed on various construction and charging methods currently under investigation.

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Harris, Daniel K., Robert Dean, Ashish Palkar, and Gary Wonacott. "High Flux Value Micro-Heat Pipe Arrays." Additional Conferences (Device Packaging, HiTEC, HiTEN, and CICMT) 2010, DPC (January 1, 2010): 001760–807. http://dx.doi.org/10.4071/2010dpc-wp21.

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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.

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Mallik, A. K., and G. P. Peterson. "Steady-State Investigation of Vapor Deposited Micro Heat Pipe Arrays." Journal of Electronic Packaging 117, no. 1 (March 1, 1995): 75–81. http://dx.doi.org/10.1115/1.2792070.

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An experimental investigation of vapor deposited micro heat pipe arrays was conducted using arrays of 34 and 66 micro heat pipes occupying 0.75 and 1.45 percent of the cross-sectional area, respectively. The performance of wafers containing the arrays was compared with that of a plain silicon wafer. All of the wafers had 8 × 8 mm thermofoil heaters located on the bottom surface to simulate the active devices in an actual application. The temperature distributions across the wafers were obtained using a Hughes Probeye TVS Infrared Thermal Imaging System and a standard VHS video recorder. For wafers containing arrays of 34 vapor deposited micro heat pipes, the steady-state experimental data indicated a reduction in the maximum surface temperature and temperature gradients of 24.4 and 27.4 percent, respectively, coupled with an improvement in the effective thermal conductivity of 41.7 percent. For wafers containing arrays of 66 vapor deposited micro heat pipes, the corresponding reductions in the surface temperature and temperature gradients were 29.0 and 41.7 percent, respectively, and the effective thermal conductivity increased 47.1 percent, for input heat fluxes of 4.70 W/cm2. The experimental results were compared with the results of a previously developed numerical model, which was shown to predict the temperature distribution with a high degree of accuracy, for wafers both with and without the heat pipe arrays.

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Qu, Guang, Dong Sheng Wang, Qun You Wang, and Meng Zhang Hua. "An Experimental Study on Electrosparking of Tool Electrode Forced Cooling Based on Micro Heat Pipe Bundle." Key Engineering Materials 904 (November 22, 2021): 375–81. http://dx.doi.org/10.4028/www.scientific.net/kem.904.375.

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An electrosparking experiment of ASP30 powder metallurgical steel was carried out through tool electrode forced cooling based on micro heat pipe bundle by using the semiconductor encapsulation mould. Results demonstrate that the micro groove formed among sintered copper fibers based on wick of micro heat pipe and the unique composite structure of the surface chopped morphology can not only increase capillary pressure of the wick, but also strengthen evaporation/condensation process at two ends of the micro heat pipe, and improve cooling effect of micro heat pipe to tool electrode significantly. Compared with traditional electrosparking, electrosparking of tool electrode forced cooling based on micro heat pipe bundle increases the inter-electrode cooling, chip removal and deionization of electrosparking and further lowers tool electrode loss by strengthening heat dissipation of tool electrode. Hence, it can improve stability of electrosparking, increase pulse utilization and increase the processing speed and processing surface quality significantly.

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Man Lee, Man Wong, and Y. Zohar. "Integrated micro-heat-pipe fabrication technology." Journal of Microelectromechanical Systems 12, no. 2 (April 2003): 138–46. http://dx.doi.org/10.1109/jmems.2003.809955.

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Sotani, J., K. Nanba, Y. Kasagi, and K. Yoshioka. "Performance of flat micro-heat pipe." Experimental Thermal and Fluid Science 7, no. 2 (August 1993): 132. http://dx.doi.org/10.1016/0894-1777(93)90128-6.

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Babin, B. R., G. P. Peterson, and D. Wu. "Steady-State Modeling and Testing of a Micro Heat Pipe." Journal of Heat Transfer 112, no. 3 (August 1, 1990): 595–601. http://dx.doi.org/10.1115/1.2910428.

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A combined experimental and analytical investigation was conducted to identify and understand better the phenomena that govern the performance limitations and operating characteristics of micro heat pipes—heat pipes so small that the mean curvature of the vapor—liquid interface is comparable in magnitude to the reciprocal of the hydraulic radius of the flow channel. The analytical portion of the investigation began with the development of a steady-state model in which the effects of the extremely small characteristic dimensions on the conventional steady-state heat pipe modeling techniques were examined. In the experimental portion of the investigation, two micro heat pipes, one copper and one silver, 1 mm2 in cross-sectional area and 57 mm in length, were evaluated experimentally to determine the accuracy of the steady-state model and to provide verification of the micro heat pipe concept. Tests were conducted in a vacuum environment to eliminate conduction and convection losses. The steady-state experimental results obtained were compared with the analytical model and were found to predict accurately the experimentally determined maximum heat transport capacity for an operating temperature range of 40° C to 60° C. A detailed description of the methodology used in the development of the steady-state model along with a comparison of the predicted and experimental results are presented.

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Fallah Abbasi, Maryam, Hossein Shokouhmand, and Morteza Khayat. "An investigation on effect of EDL on heat transfer of micro heat pipe with square and triangular cross section." Mechanics & Industry 21, no. 3 (2020): 309. http://dx.doi.org/10.1051/meca/2020021.

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Electronic industries have always been trying to improve the efficiency of electronic devices with small dimensions through thermal management of this equipment, thus increasing the use of small thermal sinks. In this study micro heat pipes with triangular and square cross sections have been manufactured and tested. One of the main objectives is to obtain an understanding of micro heat pipes and their role in energy transmission with electrical double layer (EDL). Micro heat pipes are highly efficient heat transfer devices, which use the continuous evaporation/condensation of a suitable working fluid for two-phase heat transport in a closed system. Since the latent heat of vaporization is very large, heat pipes transport heat at small temperature difference, with high rates. Because of variety of advantage features these devices have found a number of applications both in space and terrestrial technologies. The theory of operation micro heat pipes with EDL is described and the micro heat pipe has been studied. The temperature distribution have achieved through five thermocouples installed on the body. Water and different solution mixture of water and ethanol have used to investigate effect of the electric double layer heat transfer. It was noticed that the electric double layer of ionized fluid has caused reduction of heat transfer.

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Li, Xi Bing, Ming Jian Li, Ming Li, and Ying Si Wan. "Research on Thermal Resistance of Micro Heat Pipe with Trapezium-Grooved Wick." Key Engineering Materials 693 (May 2016): 395–402. http://dx.doi.org/10.4028/www.scientific.net/kem.693.395.

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As an efficient heat conducting unit, micro heat pipe is widely used in high heat flux microelectronic chips, and thermal resistance is one of the factors that are crucial to its heat transfer capacity. Based on heat transfer theory, this paper established a theoretical model of total thermal resistance through analyzing the structure and heat transfer performance of circular heat pipe with trapezium-grooved wick, simplified the model and tested the micro heat pipe for its total thermal resistance performance by setting up a testing platform. The testing results show that when the micro heat pipe is in the optimal heat transfer state, its total thermal resistance well coincides with that from the established theoretical model. As for a micro heat pipe with trapezium-grooved wick, its total thermal resistance first decreases, then increases with heat transfer capability increment, and reaches the minimum when it is in the optimal state of heat transfer performance. That too much working fluid accumulates in evaporation section and the vapor velocity is rather low is the main cause for the greater thermal resistance when the pipe is in low heat transfer quantity, yet the greater total thermal resistance when the pipe is in high heat transfer quantity is mainly caused by the working fluid drying up in condensation section. The total thermal resistance is related to many factors, such as the thermal conductivity of tube-shell material, wall thickness, wick thickness, the number of the grooves, the lengths of condensation and evaporation sections, the diameter of vapor cavity etc.. Therefore, the structure parameters of a micro heat pipe with trapezium-grooved wick should be rationally designed according to specific conditions to ensure its heat transfer capacity and total thermal resistance to meet the requirements and be in the optimal state.

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Chang, Fun Liang, and Yew Mun Hung. "Gravitational effects on electroosmotic flow in micro heat pipes." International Journal of Numerical Methods for Heat & Fluid Flow 30, no. 2 (July 17, 2019): 535–56. http://dx.doi.org/10.1108/hff-01-2019-0008.

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Purpose This paper aims to investigate the coupled effects of electrohydrodynamic and gravity forces on the circulation effectiveness of working fluid in an inclined micro heat pipe driven by electroosmotic flow. The effects of the three competing forces, namely, the capillary, the gravitational and the electrohydrodyanamic forces, on the circulation effectiveness of a micro heat pipe are compared and delineated. Design/methodology/approach The numerical model is developed based on the conservations of mass, momentum and energy with the incorporation of the Young–Laplace equation for electroosmotic flow in an inclined micro heat pipe incorporating the gravity effects. Findings By inducing electroosmotic flow in a micro heat pipe, a significant increase in heat transport capacity can be attained at a reasonably low applied voltage, leading to a small temperature drop and a high thermal conductance. However, the favorably applied gravity forces pull the liquid toward the evaporator section where the onset of flooding occurs within the condenser section, generating a throat that shrinks the vapor flow passage and may lead to a complete failure on the operation of micro heat pipe. Therefore, the balance between the electrohydrodyanamic and the gravitational forces is of vital importance. Originality/value This study provides a detailed insight into the gravitational and electroosmotic effects on the thermal performance of an inclined micro heat pipe driven by electroosmotic flow and paves the way for the feasible practical application of electrohydrodynamic forces in a micro-scale two-phase cooling device.

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Peterson, G. P., and H. B. Ma. "Theoretical Analysis of the Maximum Heat Transport in Triangular Grooves: A Study of Idealized Micro Heat Pipes." Journal of Heat Transfer 118, no. 3 (August 1, 1996): 731–39. http://dx.doi.org/10.1115/1.2822693.

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A mathematical model for predicting the minimum meniscus radius and the maximum heat transport in triangular grooves is presented. In this model, a method for determining the theoretical minimum meniscus radius was developed and used to calculate the capillary heat transport limit based on the physical characteristics and geometry of the capillary grooves. A control volume technique was employed to determine the flow characteristics of the micro heat pipe, in an effort to incorporate the size and shape of the grooves and the effects of the frictional liquid–vapor interaction. In order to compare the heat transport and flow characteristics, a hydraulic diameter, which incorporated these effects, was defined and the resulting model was solved numerically. The results indicate that the heat transport capacity of micro heat pipes is strongly dependent on the apex channel angle of the liquid arteries, the contact angle of the liquid flow, the length of the heat pipe, the vapor flow velocity and characteristics, and the tilt angle. The analysis presented here provides a mechanism whereby the groove geometry can be optimized with respect to these parameters in order to obtain the maximum heat transport capacity for micro heat pipes utilizing axial grooves as the capillary structure.

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28

Li, Xi Bing, Shi Gang Wang, Jian Hua Guo, and Dong Sheng Li. "A Mathematical Modeling Method on Micro Heat Pipe with a Trapezium-Grooved Wick Structure." Applied Mechanics and Materials 29-32 (August 2010): 1686–94. http://dx.doi.org/10.4028/www.scientific.net/amm.29-32.1686.

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With heat flux increasing and cooling space decreasing in the products in microelectronics and chemical engineering, micro heat pipe has become an ideal heat radiator for products with high heat flux. Through analyzing the factors influencing the structure, strength and heat transfer limits of circular micro heat pipe with trapezium-grooved wick structure, the heat transfer models are established in this paper, including the models of viscous limit, sonic limit, entrainment limit, capillary limit, condensing limit, boiling limit, continuous flow limit and frozen startup limit. The study lays a powerful theoretical foundation for the design and manufacture of circular micro heat pipe with a trapezium-grooved wick structure.

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29

Khrustalev, D., and A. Faghri. "Thermal Analysis of a Micro Heat Pipe." Journal of Heat Transfer 116, no. 1 (February 1, 1994): 189–98. http://dx.doi.org/10.1115/1.2910855.

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A detailed mathematical model is developed in which the heat and mass transfer processes in a micro heat pipe (MHP) are examined. The model describes the distribution of the liquid in a MHP and its thermal characteristics depending upon the liquid charge and the applied heat load. The liquid flow in the triangular-shaped corners of a MHP with polygonal cross section is considered by accounting for the variation of the curvature of the free liquid surface and the interfacial shear stresses due to a liquid-vapor frictional interaction. The predicted results obtained are compared to existing experimental data. The importance of the liquid fill, minimum wetting contact angle, and the shear stresses at the liquid-vapor interface in predicting the maximum heat transfer capacity and thermal resistance of the MHP is demonstrated.

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30

Wang, Chenxi, Yutaka Kazoe, Kyojiro Morikawa, Hisashi Shimizu, Yuriy Pihosh, Kazuma Mawatari, and Takehiko Kitamori. "Micro heat pipe device utilizing extended nanofluidics." RSC Adv. 7, no. 80 (2017): 50591–97. http://dx.doi.org/10.1039/c7ra10017e.

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31

Lee, Man, Man Wong, and Yitshak Zohar. "Characterization of an integrated micro heat pipe." Journal of Micromechanics and Microengineering 13, no. 1 (November 15, 2002): 58–64. http://dx.doi.org/10.1088/0960-1317/13/1/309.

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32

Suman, Balram, Sirshendu De, and Sunando DasGupta. "Transient modeling of micro-grooved heat pipe." International Journal of Heat and Mass Transfer 48, no. 8 (April 2005): 1633–46. http://dx.doi.org/10.1016/j.ijheatmasstransfer.2004.11.004.

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33

Riffat, S. B., X. Zhao, and P. S. Doherty. "Investigation into the performance of a micro gravitational heat pipe and a micro gravitational heat pipe with artery." International Journal of Energy Research 27, no. 1 (2002): 45–61. http://dx.doi.org/10.1002/er.858.

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34

Han, Tian, Xiao Wei Liu, Rui Zhang, and Chao Wang. "A Mathematical Model for Optimizing the Structure of a Flat Micro Heat Pipe with Fiber Wick." Advanced Materials Research 187 (February 2011): 261–65. http://dx.doi.org/10.4028/www.scientific.net/amr.187.261.

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A three-dimensional mathematical model is developed for a kind of micro heat pipe with fiber wick. The effects of phase changing, the contact angle, gravity, and heat conducting between the fibers are accounted in the model. The governing equations are formulated in the control volume and calculated by iteration. The calculated results of the model present the velocity of the working material and the phase changing rate of the liquid. The structure of the micro heat pipe is optimized by the calculated results of the model and the two levels of fibers are enough for this kind of flat micro heat pipe.

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35

Kou, Zhi Hai, Min Li Bai, and Hong Wu Yang. "Thermal Performance of a Novel Flat Heat Pipe with Integral Micro-Grooved Wick for Energy Saving." Advanced Materials Research 648 (January 2013): 202–5. http://dx.doi.org/10.4028/www.scientific.net/amr.648.202.

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A novel flat heat pipe is put forward. The novel flat heat pipe is characteristic of its integral wick structure of microgrooves, which is made of a series of thin aluminum foils folded side by side. The thermal performance of the novel flat heat pipe under the different heat loads and incline angles has been investigated experimentally. It is found that the equivalent thermal conductivity of the novel flat heat pipe can be 12.3 times higher than that of the heat pipe material. Moreover, the novel flat heat pipe with integral micro-grooved wick has good temperature uniformity. The novel flat heat pipe can play a pronounced role in heat transfer enhancement, and be expected to be good candidates for thermal management of electronic devices.

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36

Tuz, V. O., and N. L. Lebed. "THERMOHYDRAULIC DISTRIBUTION IN TWISTED MICRO HEAT EXCHANGERS MOUNTED IN ANNULAR CHANNELS." Energy Technologies & Resource Saving, no. 4 (December 20, 2021): 71–79. http://dx.doi.org/10.33070/etars.4.2021.07.

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The design of twisted heat exchangers provides a possibility to compensate for temperature and mechanical stresses thus ensuring continuous and failsafe operation of the equipment. The authors use fins and multiturn pipe bundles to reduce the mass and size characteristics of the heat exchangers. Such design significantly complicates the calculating method. The main aspect of swirling flows is the presence of radial and axial pressure gradients. When vapor or gas flows swirl, the flow velocity near the walls is much higher than the average values, while at the axis the flow is significantly slower and in some cases its values can become negative. The liquid flowing near the axis has a notably lower pressure, which can cause it to boil. Considerable radial gradients of axial and rotational speed, as well as static pressure contribute to turbulent pulsations. Given that the working fluid flows along a helical line, the flow in the near-wall area is similar to the flow around curved surfaces. The study analyses how the pipe bundle geometry impacts hydraulic distribution and scrutinizes the main components of pressure loss in the twisted heat exchanger. The analysis allowed simplifying the method of hydraulic calculation of the multiturn twisted heat exchanger. Solving the outer heat transfer and hydrodynamics problem for the twisted heat exchanger allowed determining the effect of the main factors and the relationship between the parameters of the coolant and the working mass on the distribution values. The paper presents the equations for determining geometry of the pipes with different coiling diameters, as well as the equation for finding hydraulic distribution in individual pipes in the layers of the pipe bundle. The obtained results can help increase the accuracy of thermal calculation. The authors propose to use sectioning of twisted heat exchangers as a way to reduce hydraulic distribution. Bibl. 12, Fig. 1.

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Lou, Deyuan, Teng Li, Enkang Liang, Gengxin Lu, Shaokun Yang, Jian Cheng, Qibiao Yang, Qing Tao, and Dun Liu. "Superhydrophobic/Superhydrophilic Hybrid Copper Surface Enhanced Micro Heat Pipe by Using Laser Selective Texturing." ECS Journal of Solid State Science and Technology 10, no. 11 (November 1, 2021): 113005. http://dx.doi.org/10.1149/2162-8777/ac3772.

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The heat transfer performance of Flat micro heat pipe (FMHP) is mainly determined by liquid absorption capacity of the wick. A chemical-free laser selective micro-texture technology is proposed for the fabrication of FMHP. Series of samples with different widths of the superhydrophobic-superhydrophilic spacing stripes were prepared by laser micro texturing, and their transport capacity was tested. Scanning electron microscope, three-dimensional optical profiling, and X-ray photoelectron spectroscope techniques were used to characterize the surfaces, and the mechanism of accelerating liquid reflux was investigated. Two samples with the same spacing width were used to make FMHPs. The heat transfer performance of each group of FMHPs was tested, including the start-up time, steady state temperature, and axial maximum temperature difference, and the corresponding thermal resistances were calculated. The results show that the width of superhydrophobic-superhydrophilic spacing stripes can affect the capillary force and hysteresis force during droplet transport, thereby affecting the droplet transport velocity, and in turn, influencing the heat transfer performance of the FMHP. Compared with most current flat micro heat pipes, the laser selective textured heat pipe with superhydrophobic-superhydrophilic stripes can significantly improve the heat transfer performance, and is promising for heat transfer applications in microelectronic equipment.

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Pobelyansky, A. V., D. K. Dmitriev, and A. A. Levikhin. "Intensification of convective heat exchange of walls of heat pipe of 3D-printed micro-sized turbojet engine." Omsk Scientific Bulletin. Series Aviation-Rocket and Power Engineering 6, no. 1 (2022): 128–38. http://dx.doi.org/10.25206/2588-0373-2022-6-1-128-138.

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The article considers the solution of the urgent problem of creating a micro-sized turbojet engine using 3D printing. The article describes one of the ways to cool the walls of the heat pipe of a small combustion chamber made of heat-resistant material 08KhN53BMTYu. One of the acceptable ways to cool the walls of a small-sized chamber heat pipe is convective heat exchange of the outer side of the heat pipe due to intense vortex formation in the boundary layer of the flow. This effect is achieved by the device of projections on the outer wall of the heat pipe. The article highlights the peculiarity of the shape of the protrusions, which must be carried out taking into account the technological limitations of 3D printing. The article presents a description of an experimental stand for the study of the thermal state of the heat pipe of micro turbojet engines, the method of processing experimental data and the results of experiments on the heat transfer of the heat pipe shell with and without them.

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39

Li, Xibing, Zhixiong Ye, Nanpeng Li, Jialun Chen, and Tengyue Zou. "Ploughing-Pulling Forming for Wicking Structure of Flat Micro-Groove Heat Pipe and Machine Tool Optimization." Journal of Mechanics 36, no. 4 (February 27, 2020): 423–35. http://dx.doi.org/10.1017/jmech.2019.53.

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ABSTRACTIn forming procedure of the micro grooves in the flat micro-groove heat pipe, the tie rod is often observed to be broken and the multi-tooth cutter is damaged due to the sharp increase of the ploughing-pulling pressure. This paper theoretically analyzes the factors affecting the capillary heat transferring limit of the micro-groove heat pipe, and simulates the machining process using finite element to acquire the best processing parameters: the squeeze angle is 120°, the drawing depth is 0.25mm, and the ploughing-pulling velocity is 100mm/s. Then these parameters are verified by real manufacturing experiments. The experimental results show that the ploughing-pulling pressure of the micro-groove forming process is close to the strength limit of the rod or multi-tooth cutter, and the process makes little swarf during work. Thus, only using the appropriate machine tool parameters, forming parameters and forming methods can make the wicking structure of flat micro-groove micro-heat pipe with the best heat transferring performance.

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40

Liu, Yi Bing. "Finite Element Thermal Analysis on Heat Transfer Performance of Rectangular Micro – Groove Flat Heat Pipe." Advanced Materials Research 721 (July 2013): 456–60. http://dx.doi.org/10.4028/www.scientific.net/amr.721.456.

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Having fully considered the influence of gas-liquid interfacial friction on the heat transfer characteristics of heat pipe within the channel, the mathematical model of the flow and heat transfer process in the Rectangular Micro-groove flat heat pipe is established. The simulation is performed by using thermal analysis software ANSYS. The iterative computation values of the center point temperature of the heat pipe surface being compared with the simulation results, the error is only 5.27% and the two are basically the same values, which shows that the mathematical model has a guiding significance on the analysis of heat pipe theory.

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41

Guo, Na Na, Zhen Hua Quan, Yao Hua Zhao, Hui Min Liu, Wen Fang Guo, and Dan Yu. "The Experimental Study on Fresnel Lenses Concentrator Solar Cell Cooling by a Novel Micro Flat Plate Heat Pipe." Applied Mechanics and Materials 353-356 (August 2013): 3101–4. http://dx.doi.org/10.4028/www.scientific.net/amm.353-356.3101.

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A novel micro flat plate heat pipe, micro heat pipe array, was used as heat transfer element in Fresnel lenses concentrator solar cell cooling based on its temperature uniformity and the high thermal conductivity. The contrast experiment was carried out in September in Beijing and the cell performance had been studied for difference cooling means, respectively by ordinary fin and "heat pipe and fin". Experimental results show that compared with cooling by the ordinary fin, for "heat pipe and fin" cooling cell the cell temperature is reduced by maximum 8.2% and maintained at about 55°C. The maximum power is 13.21 W, increases by 7.6%. And the photoelectric conversion efficiency improves 6.1%, with maximum efficiency of 24.13%.

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42

Hopkins, R., A. Faghri, and D. Khrustalev. "Flat Miniature Heat Pipes With Micro Capillary Grooves." Journal of Heat Transfer 121, no. 1 (February 1, 1999): 102–9. http://dx.doi.org/10.1115/1.2825922.

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Flat miniature heat pipes (FMHP’s) are shown to be very promising in the cooling of electronic component systems. This investigation presents a detailed experimental and theoretical analysis on maximum heat transfer capabilities of two copper-water FMHP’s with diagonal trapezoidal micro capillary grooves and one copper-water FMHP with axial rectangular micro capillary grooves. Maximum heat flux on the evaporator wall of the 120-mm long axial grooved heat pipe, with a vapor channel cross-sectional area of approximately 1.5 × 12 mm2 and rectangular grooves of dimensions 0.20 mm wide by 0.42 mm deep, exceeded 90 W/cm2 in the horizontal orientation and 150 W/cm2 in the vertical orientation. Theoretical prediction of the capillary limitation in the horizontal orientation agreed reasonably well with the experimental data.

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43

He, Bing Qiang, and Chun Ling Liao. "Development of Micro Rectangular Channel Gas Cooler." Advanced Materials Research 614-615 (December 2012): 321–26. http://dx.doi.org/10.4028/www.scientific.net/amr.614-615.321.

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This paper configures rectangular micro channel porous pipe gas cooler model by numerical method, and adopts finite-element analysis and bursting test method to make intensity checking of main components of gas cooler, and make real rectangular micro channel porous pipe gas cooler at the same time by configuration technique of infiltration seal weld and “pierced flanging”. Through heat transfer test of gas cooler, it obtains the surface temperature field of rectangular micro channel porous pipe gas cooler, and makes analysis of the temperature distribution in nearby area of entrance and exit and influence of forced cooling to gas cooler heat transfer.

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44

Wang, Chen, Zhong Liang Liu, and Guang Meng Zhang. "Experimental Investigation on Thermal Performance of Flat Plate Heat Pipe with Intersected Micro-Grooves." Advanced Materials Research 772 (September 2013): 480–86. http://dx.doi.org/10.4028/www.scientific.net/amr.772.480.

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A copper-water flat plate heat pipe with intersected micro-grooves was developed for cooling electronic devices in this paper. The effects of heat flux, working fluid filling ratio and inclination angles on thermal performance of the flat plate heat pipe was tested and investigated. The laboratory tests show the optimal filling ratio of the heat pipe is about 65%. Excellent thermal performance is also observed in unfavorable titled positions including vertical and anti-gravity orientation at 65%. The smallest overall thermal resistance is obtained in horizontal position and the maximal thermal resistance is observed in vertical position. The influence of inclination angles on thermal performance of the heat pipe in both axial direction and radial direction is also investigated. As the heat pipe is tilted, the ability of temperature leveling in radial direction is enhanced, nevertheless, the capacity of heat transfer in radial direction decreased at the same time.

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45

Zeng, Liping, Xing Liu, Quan Zhang, Jun Yi, Xianglong Liu, and Huan Su. "Research on Heat Transfer Performance of Micro-Channel Backplane Heat Pipe Air Conditioning System in Data Center." Applied Sciences 10, no. 2 (January 13, 2020): 583. http://dx.doi.org/10.3390/app10020583.

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This paper deals with the heat transfer performance of a micro-channel backplane heat pipe air conditioning system. The optimal range of the filling rate of a micro-channel backplane heat pipe air conditioning system was determined in the range of 65–75%, almost free from the interference of working conditions. Then, the influence of temperature and air volume flow rate on the heat exchange system were studied. The system maximum heat exchange is 7000–8000 W, and the temperature difference between the inlet and outlet of the evaporator and the condenser is almost 0 °C. Under the optimum refrigerant filling rate, the heat transfer of the micro-channel heat pipe backplane system is approximately linear with the temperature difference between the inlet air temperature of the evaporator and the cooling distribution unit (CDU) inlet water temperature in the range of 18–28 °C. The last part compares the heat transfer characteristics of two refrigerants at different filling rates. The heat transfer, pressure, and refrigerant temperature of R134a and R22 are the same with the change of filling rate, but the heat transfer of R134a is lower than that of R22. The results are of great significance for the operational control and practical application of a backplane heat pipe system.

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Li, Xi Bing, Xun Wang, Yun Shi Ma, and Zhong Liang Cao. "Research on Thermal Resistance of Micro Heat Pipe with Sintered Wick." Key Engineering Materials 589-590 (October 2013): 552–58. http://dx.doi.org/10.4028/www.scientific.net/kem.589-590.552.

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As a highly efficient heat dissipation unit, a micro heat pipe is widely used in high heat flux microelectronic chips, and its thermal resistance is crucial to heat transfer capacity. Through analyses of the structure and heat transfer performance of a circular heat pipe with sintered wick, the theoretical model of total thermal resistance was established on heat transfer theory, and then simplified, finally a testing platform was set up to test for total thermal resistance performance. The testing results show that when the micro heat pipe is in optimal heat transfer state, its total thermal resistance conform well with that from the theoretical model, and its actual thermal resistance is much lower than that of the rod made of the material with perfect thermal conductivity and of the same geometric size. With the increment of heat transfer capability, the total thermal resistance of a micro heat pipe with sintered wick decreases first, then increases and reaches the minimum when it is in the optimal heat transfer state. The greater total thermal resistance in low heat transfer performance is mainly caused by too much working fluid accumulating in evaporator and the lower velocity in vapor cavity, and the greater total thermal resistance in high heat transfer performance is mainly due to the working fluid drying up in condenser. Total thermal resistance is related to many factors, such as thermal conductivity of tube-shell material, wall thickness, wick thickness, copper powders grain size and porosity, the lengths of condenser and evaporator, and the diameter of vapor cavity etc.. Therefore, the structure parameters of a micro heat pipe with sintered wick should be reasonably designed according to the specific conditions to ensure its heat transfer capacity and total thermal resistance to meet the requirements.

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47

Ji, Haiwei, Yaping Zhang, Fang Wang, and Jin Zhang. "Thermal Performance Simulation of Novel Micro Heat Pipe." Journal of Physics: Conference Series 1936, no. 1 (June 1, 2021): 012025. http://dx.doi.org/10.1088/1742-6596/1936/1/012025.

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48

Wang, Y. X., and G. P. Peterson. "Analysis of Wire-Bonded Micro Heat Pipe Arrays." Journal of Thermophysics and Heat Transfer 16, no. 3 (July 2002): 346–55. http://dx.doi.org/10.2514/2.6711.

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49

Launay, S., V. Sartre, and M. Lallemand. "Experimental study on silicon micro-heat pipe arrays." Applied Thermal Engineering 24, no. 2-3 (February 2004): 233–43. http://dx.doi.org/10.1016/j.applthermaleng.2003.08.003.

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Han, Tian, Xiao Wei Liu, and Chao Wang. "Design and Research of Flat Micro Heat Pipe with Glass Fiber Wick." Key Engineering Materials 483 (June 2011): 603–6. http://dx.doi.org/10.4028/www.scientific.net/kem.483.603.

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A kind of flat micro heat pipe with glass fiber wick structure is designed and fabricated. The structure of the wick is presented and also the excellence of the structure is described. For the glass fiber wick, the maximum heat transports is calculated by one-dimensional steady governing equations. Experimental testing is performed for the fabricated micro heat pipe in vacuum. The testing results is presented and analyzed.

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Journal articles on the topic 'Micro heat pipe'

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