Towards a Durable Polymeric Internal Coating for Diabatic Sections in Wickless Heat Pipes

2019 ◽  
Vol 141 (9) ◽  
Author(s):  
Fabio Villa ◽  
Marco Marengo ◽  
Joël De Coninck
Keyword(s):  
Heat Flux ◽  
Heat Pipe ◽  
Surface Properties ◽  
Critical Heat Flux ◽  
Thermal Performance ◽  
Heat Pipes ◽  
Surface Wettability ◽  
Polymeric Coating ◽  
Stainless Steel Surface ◽  
Power Load

Heat pipe characteristics are linked to the surface properties of the diabatic surfaces, and, in the evaporator, surface properties influence both the onset boiling temperature (TONB) and the critical heat flux (CHF). In this work, the effect of surface wettability in pool boiling heat transfer is studied in order to understand if there could be a path to increment heat pipe thermal performance. This work analyzes the effects of surface wettability on boiling (tested fluid is pure water) and proposes a new super-hydrophobic polymeric coating (De Coninck et al., 2017, “Omniphobic Surface Coatings,” Patent No. WO/2017/220591), which can have a very important effect in improving the heat pipe start-up power load and increasing the thermal performance of heat pipes when the flux is lower than the critical heat flux. The polymeric coating is able to reduce the TONB (−11% from 117 °C to about 104 °C) compared with the uncoated surfaces, as it inhibits the formation of a vapor film on the solid–liquid interface, avoiding CHF conditions up to maximum wall temperature (125 °C). This is realized by the creation of a heterogeneous surface with superhydrophobic surface (SHS) zones dispersed on top of a hydrophilic surface (stainless steel surface). The proposed coating has an outstanding thermal resistance: No degradation of SH properties of the coating has been observed after more than 500 thermal cycles.

scholarly journals Experimental Study on Thermal Performance of a Bent Copper-Water Heat Pipe

2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Shuangshuang Miao ◽  
Jiajia Sui ◽  
Yulong Zhang ◽  
Feng Yao ◽  
Xiangdong Liu
Keyword(s):  
Heat Flux ◽  
Heat Pipe ◽  
Critical Heat Flux ◽  
Working Conditions ◽  
Thermal Performance ◽  
Heat Input ◽  
High Heat ◽  
High Heat Flux ◽  
Electronic Components ◽  
Copper Water

Vapor-liquid phase change is regarded as an efficient cooling method for high-heat-flux electronic components. The copper-water bent heat pipes are particularly suited to the circumstances of confined space or misplaced heat and cold sources for high-heat-flux electronic components. In this paper, the steady and transient thermal performance of a bent copper-water heat pipe is studied based on a performance test system. The effects of cooling temperature, working conditions on the critical heat flux, and equivalent thermal conductivity have been examined and analyzed. Moreover, the influences of heat input and working conditions on the thermal response of a bent heat pipe have also been discussed. The results indicate that the critical heat flux is enhanced due to the increases in cooling temperature and the lengths of the evaporator and condenser. In addition, the critical heat flux is improved by extending the cooling length only when the operating temperature is higher than 50°C. The improvement on the equivalent thermal by increasing the heating length is more evident than that by increasing cooling length. It is also demonstrated by the experiment that the bent copper-water heat pipe can respond quickly to the variation of heat input and possesses superior transient heat transfer performance.

An Experimental Study on the Thermal Performance of the Flat Heat Pipe

2016 ◽  
Author(s):  
Hao Xiaohong ◽  
Jiqing Guan ◽  
Jingbo Zhao
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Pipe ◽  
Thermal Performance ◽  
Electronic Devices ◽  
Heat Pipes ◽  
Deionized Water ◽  
Working Fluid ◽  
Nano Fluid ◽  
Flat Heat Pipe

As the rapid growing of the semiconductor logic gate number and operation speed, the heat dissipated from electronic devices increases drastically. Moreover, most of the heat flux can reach about 100 W/cm2, therefore efficient removal of the heat from the electronic devices is essential to ensure the reliable operation of the electronic devices. The traditional direct cooling system, such as air cooling, liquid cooling, would not be able to transfer the high heat flux owing to their heat transfer limits, so advanced cooling solutions are necessary. The flat heat pipes have some advantages, such as small scale, strong heat transfer capacity, low weight penalty and low environmental requirements, therefore, in recent years, researchers have shown great interest for the flat heat pipe. But most of them played the important on the structure design of the flat heat pipes, and few of them focused on the study of the effect of the working fluid on the heat transfer performance. In this paper, a flat heat pipe with rectangular channel is designed and manufactured, and an experimental set up was built to study working fluid on the effects of the flat heat Pipe thermal performance. The flat heat pipe is heated via a 35mmx20mm rectangular electrical resistance (the evaporator side), and the other side (the condenser side) is cooled by convection of a heat sink. In the experimental work, three types of working fluid are used in the heat pipe: (A) deionized water, (B) deionized water-based Fe3O4 nano fluid (1, 1.5wt%). A comparison is performed for the thermal performance of different size flat heat pipe. Finally, the experimental results showed that nano fluid could improve the thermal performance of the FHP. With the same charge volume, the heat transfer coefficient of the FHPs filled with nano fluid were higher than that of DI water. There was an optimal mass concentration which was estimated to be 1.5 wt% to achieve the maximum heat transfer enhancement.

scholarly journals The effect of operating parameters on the heat transfer in the heat pipe

2021 ◽  
Vol 2119 (1) ◽  
pp. 012088
Author(s):  
A. A. Litvintceva ◽  
N. I. Volkov ◽  
N. I. Vorogushina ◽  
V. A. Moskovskikh ◽  
V. V. Cheverda
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Pipe ◽  
Temperature Difference ◽  
Heat Pipes ◽  
Working Fluid ◽  
Operating Parameters ◽  
Temperature Stabilization ◽  
Ir Camera ◽  
Fluid Properties

Abstract Heat pipes are a good solution for temperature stabilization, for example, of microelectronics, because these kinds of systems are without any moving parts. Experimental research of the effect of operating parameters on the heat transfer in a cylindrical heat pipe has been conducted. The effect of the working fluid properties and the porous layer thickness on the heat flux and temperature difference in the heat pipe has been investigated. The temperature field of the heat pipe has been investigated using the IR-camera and K-type thermocouples. The data obtained by IR-camera and K-type thermocouples have been compared. It is demonstrated the power transferred from the evaporator to the condenser is a linear function of the temperature difference between them.

Effect of Fluid Loading on the Performance of Wicked Heat Pipes

Volume 3 ◽  
2004 ◽  
Author(s):  
R. Kempers ◽  
A. Robinson ◽  
C. Ching ◽  
D. Ewing
Keyword(s):  
Heat Flux ◽  
Heat Pipe ◽  
Heat Transport ◽  
Heat Pipes ◽  
Working Fluid ◽  
Fluid Loading ◽  
Maximum Heat ◽  
Horizontal Orientation ◽  
Maximum Heat Flux ◽  
Dry Out

A study was performed to experimentally characterize the effect of fluid loading on the heat transport performance of wicked heat pipes. In particular, experiments were performed to characterize the performance of heat pipes with insufficient fluid to saturate the wick and excess fluid for a variety of orientations. It was found that excess working fluid in the heat pipe increased the thermal resistance of the heat pipe, but increased maximum heat flux through the pipe in a horizontal orientation. The thermal performance of the heat pipe was reduced when the amount of working fluid was less than required to saturate the wick, but the maximum heat flux through the heat pipe was significantly reduced at all orientations. It was also found in this case the performance of this heat pipe deteriorated once dry-out occurred.

Advanced Cooling With Embedded Heat Pipes for High Power Microelectronics

2009 ◽  
Author(s):  
Victor Adrian Chiriac
Keyword(s):  
Heat Pipe ◽  
Thermal Performance ◽  
Heat Sink ◽  
Heat Pipes ◽  
Optimal Operation ◽  
Operating Conditions ◽  
Peak Temperature ◽  
Transient Temperature ◽  
Efficient Operation ◽  
The Impact

The transient thermal behavior of a complex testing system including multiple fans, a mixing enclosure, Cu inserts and a leaded package dissipating large amounts of power over short time durations is evaluated via numerical simulations. The system performance is optimized with heat sink/fan structure for device efficient operation under constant powering. The study provides meaningful understanding and prediction of a transient powering scenario at high powering levels, evaluating the impact of alternative cooling fan/heat pipe configurations on the thermal performance of the system. One design is chosen due to its effective thermal performance and assembly simplicity, with the package embedded in heat sink base with multiple (5) heat pipes. The peak temperature reached by the modified design with 4 cooling fans is ∼95°C, with the corresponding Rja thermal resistance ∼0.58°C/W. For the transient study (with embedded heat pipes and 4 fans), after one cycle, both peak temperature (at 45 s) and the end temperature (at 49 s) decrease as compared to the previous no heat pipe/single fan case (especially the end temperature reduces by ∼16%). The temperature drop between peak and end for each cycle is ∼80.2°C, while the average power per transient cycle is ∼31.27W. With this power, the design with 5 perpendicular heat pipes, 4 fans and insert reaches a steady state peak temperature of ∼98°C. Applying the superposition principle, the maximum transient temperature after a large number of operating cycles will not exceed ∼138.1°C, satisfying the thermal budget under the current operating conditions. The benefit of the study is related to the possibility to extract the maximum/minimum temperatures for a real test involving a large number of heating-cooling cycles, yet maintaining the initial and peak temperatures within a certain range for the optimal operation of the device. The flow and heat transfer fields are thoroughly investigated: using a combination of numerical and analytical study, the thermal performance of the device undergoing large number of periodic thermal cycles is predicted. Further comparison between measurement and simulation results reveals good agreement.

scholarly journals Transport in Flat Heat Pipes at High Heat Fluxes From Multiple Discrete Sources

2004 ◽  
Vol 126 (3) ◽  
pp. 347-354 ◽  
Author(s):  
Unnikrishnan Vadakkan ◽  
Suresh V. Garimella ◽  
Jayathi Y. Murthy
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Fluid Flow ◽  
Heat Pipe ◽  
Three Dimensional ◽  
Heat Pipes ◽  
Density Change ◽  
Heat Sources ◽  
Discrete Heat Sources ◽  
Energy Equations

A three-dimensional model has been developed to analyze the transient and steady-state performance of flat heat pipes subjected to heating with multiple discrete heat sources. Three-dimensional flow and energy equations are solved in the vapor and liquid regions, along with conduction in the wall. Saturated flow models are used for heat transfer and fluid flow through the wick. In the wick region, the analysis uses an equilibrium model for heat transfer and a Brinkman-Forchheimer extended Darcy model for fluid flow. Averaged properties weighted with the porosity are used for the wick analysis. The state equation is used in the vapor core to relate density change to the operating pressure. The density change due to pressurization of the vapor core is accounted for in the continuity equation. Vapor flow, temperature and hydrodynamic pressure fields are computed at each time step from coupled continuity/momentum and energy equations in the wick and vapor regions. The mass flow rate at the interface is obtained from the application of kinetic theory. Predictions are made for the magnitude of heat flux at which dryout would occur in a flat heat pipe. The input heat flux and the spacing between the discrete heat sources are studied as parameters. The location in the heat pipe at which dryout is initiated is found to be different from that of the maximum temperature. The location where the maximum capillary pressure head is realized also changes during the transient. Axial conduction through the wall and wick are seen to play a significant role in determining the axial temperature variation.

Effects of Surface Coating of Nanoparticles on Thermal Performance of Open Loop Pulsating Heat Pipes

2012 ◽  
Author(s):  
Mehdi Taslimifar ◽  
Maziar Mohammadi ◽  
Ali Adibnia ◽  
Hossein Afshin ◽  
Mohammad Hassan Saidi ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Heat Pipe ◽  
Thermal Performance ◽  
Surface Coating ◽  
Heat Pipes ◽  
Open Loop ◽  
Working Fluid ◽  
Pulsating Heat Pipe ◽  
Performance Of Heat Transfer

Homogenous dispersing of nanoparticles in a base fluid is an excellent way to increase the thermal performance of heat transfer devices especially Heat Pipes (HPs). As a wickless, cheap and efficient heat pipe, Pulsating Heat Pipes (PHPs) are important candidates for thermal application considerations. In the present research an Open Loop Pulsating Heat Pipe (OLPHP) is fabricated and tested experimentally. The effects of working fluid namely, water, Silica Coated ferrofluid (SC ferrofluid), and ferrofluid without surface coating of nanoparticles (ferrofluid), charging ratio, heat input, and application of magnetic field on the overall thermal performance of the OLPHPs are investigated. Experimental results show that ferrofluid has better heat transport capability relative to SC ferrofluid. Furthermore, application of magnetic field improves the heat transfer performance of OLPHPs charged with both ferrofluids.

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