Screen Mesh Wick Heat Pipe Research Articles

Predicting the thermal performance of screen mesh wick heat pipe with alumina nanofluids using response surface methodology

This study aims to investigate the effect of heat load, tilt angle, and volume concentration of alumina nanofluid on the thermal performance enhancement of cylindrical screen mesh wick heat pipe in terms of thermal resistance(R) and thermal conductivity(k). Response surface methodology based on the Box–Behnken design was implemented to investigate the influence of heat input (100–200 W), tilt angle (0–90°), and volume concentration (0.05–0.25 vol%) of nanofluid as the independent variables. Second-order polynomial equations were established to predict the responses, ‘R’, and ‘k’. The significance of the models was tested by means of analysis of variance (ANOVA). In addition, a correlation between the independent variables was derived in this study. The results revealed that the optimum heat input, inclination angle, and concentration of nanofluid were determined as 200 W, 52.72°, and 0.1773 vol. % respectively for both ‘R’ and ‘k’. SEM analysis was performed to observe the thermal performance phenomena of the heat pipe before and after experimentation.

Thermal performance prediction of heat pipe with TiO2 nanofluids using RSM

Heat pipe is a two-phase heat transfer device with high effective thermal conductivity and transfer huge amount of heat with minimum temperature gradient in between evaporator and condenser section. This paper objective is to predict the thermal performance in terms of thermal resistance, R, and heat transfer coefficient, h, of screen mesh wick heat pipe with deionized water-TiO2 as working fluid. The input process parameters of heat pipe such as heat load, Q, tilt angle, ?, and concentration of nanofluid, ?, were modeled and optimized by utilizing response surface methodology with MINITAB-17 software to attain minimum thermal resistance and maximum heat transfer coefficient. The minimum thermal resistance of 0.1764 ?C per W and maximum heat transfer coefficient of 1411.52 W/m2 ?C was obtained under the optimized conditions of 200 W heat load, 57.2? tilt angle, and 0.159 vol.% concentration of nanofluid.

Experimental and transient thermal analysis of screen mesh wick heat pipe

Transient thermal analysis of a screen mesh wick heat pipe is performed with a screen mesh numbers 60 and 100 using de-ionized water as working fluid, which is applicable in electronics cooling. Based on evaporation and condensation phenomenon heat pipe is operating. Experiments are conducted (ranging from 20Watts-160Watts) with different inclination angles (15,30,60,90) for calculation of thermal resistance(Rth) and heat transfer coefficient (h), at different mass flow rates and heat inputs. Computational transient thermal analysis is done for the same heat inputs using ANSYS 16.0. It is observed that thermal resistance decreases with increase in heat input [maximum at 0.042(°C//W), minimum at 0.023 (°C/W)] because fluid molecular bonding decreases with increase in heat input. Heat transfer coefficient values are maximum at 8800 (W/m2K) for transient thermal analysis and 8500 (W/m2K) for experimental. The Heat transfer coefficient is more in thermal analysis when compared to experimental results because heat loss is less in ANSYS and more in practical. At 60 W of heat input the maximum Heat transfer coefficient is found.

Performance evaluation of the cylindrical shaped heat pipe utilizing water-based CuO and ZnO hybrid nanofluids

ABSTRACT The influence of the heat pipe orientation and the working fluid type of the screen mesh wick heat pipe was investigated experimentally. A hybrid nanofluid using three proposals for composite nanoparticles scattered in DI Water was used as the working fluid. In each case, seven directions (0°–90°, deviation 15°) were investigated. Thermal properties were evaluated by the average temperature gap between the evaporator and condenser surfaces, thermal resistance, thermal conductivity (effective), and overall HTC. Experimental results imply that the tilt angle and the hybrid nanofluid used have a significant impact on heat transfer of heat pipe. By the time the tested heat pipes come into contact with 75% CuO–25% ZnO/DI water at an angle of 60°, they have the best heat transfer properties of any other type of fluid. Furthermore, it was found that the thermal characteristic of the heat pipes tested were hampered by the expansion of heat loads in the range 60–160 W.

Heating and cooling capacity of phase change material coupled with screen mesh wick heat pipe for thermal energy storage applications

The thermal performance of a phase change material (PCM) heat pipe system is experimentally analysed using acetone as heat pipe fluid in a heat load range of 10-50 W at different flow rates of the condenser coolant. The evaporator of the heat pipe is enclosed in a chamber which filled with a PCM or water. Heat inputs are applied at the evaporator of the heat pipe through the PCM or water. In this study, the heat retention as well as cooling time of the PCM-water are estimated at different heat loads and flow rates of condenser coolant. Similarly, the thermal resistance, evaporator and condenser heat transfer coefficients are also estimated at different heat loads. It is observed that the PCM takes more time during heating and cooling cycles to reach the steady-state temperatures and the temperature values reached during heating are also higher for PCM compared to water. The use of PCM enhances the thermal storage capacity and shows a maximum enhancement of 200% in heat retention time compared to water at 50 W. Moreover, a maximum enhancement of 63.6% is observed in the steady-state temperature of the PCM compared to water. Similarly thermal resistance, evaporator wall temperature and heat transfer coefficients of the heat pipe also vary for PCM and water. The experimental results indicate that PCM or water can be used in this combined system depending upon requirement of thermal storage or electronics cooling.

Population balance for capillary limit modeling in a screen mesh wick heat pipe working with nanofluids

In this work, a study to evaluate the effect of the concentration of nanoparticles of an Al2O3/water nanofluid on the capillary limit of a heat pipe with a screen mesh wick was performed. For the first time, a numerical model has been developed to couple the hydrodynamical equations that describe the flow and the phase change of the working fluid in the wick of a screen mesh heat pipe, with a population balance which account for the agglomeration of Al2O3 nanoparticles and the deposition of them on the surface of the wick. The model has been validated with experimental data of temperature and capillary limit.Experimental results showed that capillary limit is reached at higher heat input when nanoparticles are added to the working fluid. The best improvement of the capillary limit was around 30–40%. At high nanoparticle concentration, the improvement of the capillary limit was more variable, and the thermal resistance was higher than even the working fluid without nanoparticles. The improvement of the capillary limit has been found to be due to the modification of the wettability of the wick instead of reduction of effective pore radius or enhancing of the thermal conductivity. Numerical results fitted in good agreement the experimental data, but some limitations were found when high nanoparticle concentration was simulated because model can not predict the non-uniform deposition observed at microscopic level. Finally, it was found that there is an optimal concentration of nanoparticles to delay the occurrence of capillary limit. In this work, that optimal concentration was Al2O3/water 0.5% w/w.

Heat Transfer Performance Analysis of Screen Mesh Wick Heat Pipe Using CuO Nano Fluid

In this paper, the effect of multilayer screen mesh wicks and CuO nano-fluid as working fluid is investigated on the performance of heat pipe. Three heat pipes were fabricated with different layers of screen mesh wicks to improve capillary action of working fluid. Heat pipes of 350 mm length and 19.5 mm diameter were used. The different mesh configurations used in this work were 100+150 mesh, 100+2X150 mesh and 4X150 meshes. The concentration of CuO nano-fluids in the experiments was maintained at 1% by weight of water. The heat pipes are tested with water and CuO as working fluid for different heat inputs of 35W, 50W 75W, 100W and 120W. The thermal resistance and heat transfer rate were determined. It is found that the thermal resistance decreases with increase in heat input. There is increase in heat transfer rate in case of CuO nanofluid loading in ordinary water compared to distilled water as working fluid. For all orientation the maximum heat transfer through the heat pipe increased as the number of mesh layer of the wick is increased. The heat transfer rate is found to be maximum at 100 l/h mass flow rate compared to that of 150 l/h.

An experimental investigation and optimization of screen mesh heat pipes for low-mid temperature applications

The perspectives of utilization of a screen mesh heat pipe (HP) for low to medium operating temperature applications are studied in this study. A two-dimensional mathematical model for heat and mass transfer of HPs is presented to define its performances under steady state operations. The model couples heat conduction in the wall with both liquid flow in the wick and vapor flow in the core. Experimental analysis is developed to evaluate the influence of operating parameters (the orientation and the cooling temperature) as well as the evaporator section length on the performance of the HP. Furthermore, a modeling approach to optimize the HP performance from a thermal point of view is presented. Using the heat transfer capability and total thermal resistance as the objective function and the structure parameters as the decision variable, the optimization design for the HP is performed using the Non-Dominated Sorting in Genetic Algorithms-II (NSGA-II). The results show that the optimal wick thickness and wick permeability to be a strong function of the heat flux. It is concluded that to have lower thermal resistance at lower heat fluxes for a screen mesh wick HP may have a large effective thermal conductivity, but have a small permeability. While at high heat transfer rate a small effective thermal conductivity, but a large permeability is recommended. The designer must always make trade-offs between these competing factors to obtain an optimal wick design. The investigations are aimed to determine working limits and thermal performance of HPs for low to medium operating temperature applications.

Experimental studies on heat transfer characteristics of SS304 screen mesh wick heat pipe

In this paper, the experimental performance of a SS304 heat pipe under natural and forced convection modes using two different wick mesh sizes is reported. Deionised water was used as a working fluid with different heat inputs. The wick material is made up of SS303 with two mesh sizes (such as, 100 and 200 mesh). The heat pipe was positioned at three orientations (such as, horizontal, inclined, and vertical). During experiments, the ambient temperature was maintained at 30 ± 2°C. The results showed that the heat pipe at an inclined position of 45° has about 71% higher heat transfer coefficient with minimum thermal resistance when compared to the horizontal and vertical positions. Moreover, the results confirmed that, the heat pipe using wick with 200 mesh specification at inclined position is an optimal configuration when compared to other configurations.

Augmented Thermal Performance of Straight Heat Pipe Employing Annular Screen Mesh Wick and Surfactant Free Stable Aqueous Nanofluids

abstractStable surfactant-free Al2O3/deionized (DI) water nanofluids are prepared by a two-step process and are stabilized using an ultrasonic homogenizer. The thermal conductivity enhancement measured by a transient hot wire technique demonstrated a nonlinear relationship with increase in volume fraction of dispersed nanoparticles and attains a maximum enhancement of 15% for 1 vol% of Al2O3 loading in deionized water at 70°C. The stabilized Al2O3/DI water nanofluids were employed as the working fluid in a screen mesh wick heat pipe placed horizontally. The straight heat pipe configuration is altered for more practicality in use, with crimped edges, extended conduction lengths, and minute surface depressions. The heat pipe is tested at various levels of heat inputs and concentrations of Al2O3 nanoparticles. The evaporator section is heated by circulating water through a heating chamber, and the condenser section is cooled under free convection. The experimental results show an optimum reduction of 22% in the thermal resistance value using 1 vol% of Al2O3/DI nanofluids as compared to DI water at low heat input of 12 W. The stabilized operation of the heat pipe is observed at high heat input of 73 W and at low concentration of 0.005 vol% Al2O3/DI water nanofluids. The findings emphasize potential for nanofluids as future heat pipe fluids.

A Feasibility Study About Using SiO2 Nanofluid Screen Mesh Wick Heat Pipe for Cooling of High-Power LEDs

Effective and timely heat removal from high-power light-emitting diodes (LEDs) is crucial to their performance and lifetime. The strategy of using a screen mesh wick heat pipe with SiO2 nanofluid as the working fluid for LED heat dissipation is comprehensively evaluated. An experimental system is set up to study the heat transfer performance of the heat pipe. The obtained experimental results give optimal conditions/parameters for the heat pipe: 60% charging ratio, 30° incline angle, and 1wt% concentration of the nanofluid. Compared with a heat pipe using the secondary distilled water as the working fluid, the thermal resistance of the heat pipe using the SiO2 nanofluid as the working fluid is generally reduced by around 35–40% for the investigated heat load range of 1–60 W. Based on an equivalent heat conductivity of the SiO2 nanofluid heat pipe derived from the experimental results, an Icepak modeling effort for the cooling system of a 60-W LED lamp is then expended. The numerical results show that the temperature of the LED lamp remains low and quite uniform across the LED chip region, indicating the technical feasibility of using this class of heat pipes for cooling of high-power LEDs.

Numerical analysis of a screen mesh wick heat pipe with Cu/water nanofluid

A two-dimensional transient numerical model is developed to predict the vapor core, wall temperatures, vapor pressure, vapor velocity and liquid velocity in the screen mesh wick heat pipe. The mass, momentum and energy equations are solved numerically for liquid and vapor regions. The effect of Cu–water nanofluid on the heat transfer performance of heat pipe is studied using the developed model and the same is compared with that of the DI water. The transient profiles of vapor and liquid velocities in the wick region and the location of dry-out in the evaporator section of the heat pipe are also obtained using the developed model. It is found that the addition of nanoparticles leads to the reduction in wall temperature, operating pressure, vapor temperature and total resistance of the heat pipe; thereby, increasing the heat transfer of the heat pipe at the same heat load. Interestingly, the liquid and vapor velocities of the heat pipe charged with 0.1wt% of Cu-water nanofluid is found to be 20% higher when compared with that of the heat pipe with DI water at the same operating conditions. It is also observed that the decreased pore size of the wick due to the addition of nanoparticles increases the effective thermal conductivity of the wick structure which acts as a coating layer and enhances the heat transfer capability of the heat pipe.

Characteristics of Screen Mesh Wick Heat Pipe with Nano-fluid as Passive Cooling System

The heat pipe is one of the cooling media which is potential to be developed for the passive cooling system for nuclear reactors. To enhance the performance of the heat pipe, nanofluids have been used as the working fluid for the heat pipe. This paper studies the characteristics of nanofluids as the working fluid of heat pipe with screen mesh wick, which was the mixture of nano-sized particles (Al 2 O 3 and TiO 2 ) with water as the base fluid. The nanoparticles have average diameter of 20 nm, made with 1% to 5% volume fraction. The heat pipe thermal performance was tested using heater with different heat load. The experimental result shows the use of 5% Al 2 O 3 -water improve the thermal performance by reducing the temperature at evaporator side as much as 23.7% and the use of TiO 2 -water reduce the temperature at evaporator side as much as 20.2% compared to the use of water. The use of nanofluid also decreases the thermal resistance of heat pipe. As the use of nanofluid improves thermal performance of heat pipe, it has a potential for applications along with heat pipes at nuclear reactors. Received: 04 December 2012, Revised: 13 February 2013, Accepted: 25 February 2013

Experimental investigation of thermal conductivity and heat pipe thermal performance of ZnO nanofluids

Nanofluids consisting of nanoparticles dispersed in heat transfer carrier fluid have received attention over the last view years for their enormous potential to improve the efficiency of heat transfer fluids. This work investigated the synthesis of ZnO nanoparticle-based thermal fluids prepared using a two-step process. Chemical precipitation was used for the synthesis of the ZnO powders, and ultrasonic irradiation was used to disperse the nanoparticles in ethylene glycol as the base fluid. The thermal conductivity enhancement of the nanofluid demonstrated a nonlinear relationship with respect to volume fraction and crystallite size, with increases in the volume fraction and crystallite size both resulting in increases in the measured enhancement. The nanofluids used in conductivity measurements were further employed as the working medium for a conventional screen-mesh wick heat pipe. The experiments were performed to measure the temperature distribution and thermal resistance of the heat pipe. The results showed temperature distribution and thermal resistance to decrease as the concentration and the crystallite size of the nanoparticle increased.

Thermal performance of screen mesh wick heat pipes using water-based copper nanofluids

Fairly stable surfactant free copper–distilled water nanofluids are prepared using prolonged sonication and homogenization. Thermal conductivity of the prepared nanofluid displays a maximum enhancement of ∼15% for 0.5 wt% of Cu loading in distilled water at 30 °C. The wall temperature distributions and the thermal resistances between the evaporator and the condenser sections of a commercial screen mesh wick heat pipe containing nanofluids are investigated for three different angular position of the heat pipe. The results are compared with those for the same heat pipe with water as the working fluid. The wall temperatures of the heat pipes decrease along the test section from the evaporator section to the condenser section and increase with input power. The average evaporator wall temperatures of the heat pipe with nanofluids are much lower than those of the heat pipe with distilled water. The thermal resistance of the heat pipe using both distilled water and nanofluids is high at low heat loads and reduces rapidly to a minimum value as the applied heat load is increased. The thermal resistance of the vertically mounted heat pipe with 0.5 wt% of Cu–distilled water nanofluid is reduced by ∼27%. The observed enhanced thermal performance is explained in light of the deposited Cu layer on the screen mesh wick in the evaporator section of the heat pipe.

Thermal performance of screen mesh wick heat pipes with nanofluids

Heat pipes have been widely used as one of the alternative methods to absorb more heat in the cooling systems of electronic devices. To improve the thermal performance of heat pipes, the practice of using various combinations of heat pipes and nanofluids has been widely observed. The purpose of this research was to determine the concentrations and the types of nanofluids that can best enhance the thermal performance of screen mesh wick heat pipes and to determine the effect of coatings on the structure of the screen mesh wick after using nanofluids as the working fluid. In this research, screen mesh wick heat pipes were manufactured and tested to determine the thermal resistance of nanofluids such as Al2O3–water, Al2O3–ethylene glycol, TiO2–water, TiO2–ethylene glycol and ZnO–ethylene glycol charged in the screen mesh wick heat pipes. The concentration of the nanoparticles was varied from 1% to 5% of the volume of the base fluid. The screen mesh wick heat pipe with the best performance was that which used Al2O3–water nanofluid with 5% volume concentration. Using nanofluids in the heat pipes resulted in the formation of a thin coating on the screen mesh surface from the element of the nanoparticles. However, the thin coating promotes good capillary structure. The higher thermal performance of heat pipes charged with nanofluids proved the potential of nanofluids as a substitute for conventional working fluids. This finding makes nanofluids attractive as working fluids in screen mesh wick heat pipes.