Carbon Nanotube Nanofluids Research Articles

Modeling the thermal conductivity of carbon nanotube (CNT) nanofluids and nanocomposites – a fresh restart

After two decades of discussion it seems that the model-based prediction of the thermal conductivity of carbon nanotube (CNT) nanofluids and nanocomposites has come to a dead end and needs a fresh restart, since misleading statements and claims and repeated over and over again, mainly in the current literature on CNT nanofluids. In this paper a simple but rigorous model is presented (in two variants) for predicting the thermal conductivity of CNT nanofluids and nanocomposites. The model is based on Fricke's classical Maxwell-type effective medium approximation for systems with spheroidal particles, but – in contrast to all previous models – takes into account the Molyneux bounds for describing the random orientation of the CNTs. We show that the predictions of our model are significantly lower than the corresponding predictions via Nan's model and will thus turn out to be closer to experimental data reported in the literature.

Solid‐Volume‐Fraction Retained Tailoring of Thermal Diffusivity of Multiwalled Carbon Nanotube Nanofluid: A Photothermal Investigation

The diversified forms of heat engines necessitate developing energy‐efficient engine oils and coolants. The article proposes a method of thermal diffusivity tuning of the base fluid (ethylene glycol) using multiwalled carbon nanotubes (MWCNTs), annealed at different temperatures, without altering the solid volume fraction. Having studied the annealing‐induced structure modifications of MWCNTs through thermogravimetric and spectroscopic studies, the thermal diffusivity variations are investigated through the sensitive photothermal mode‐mismatched dual‐beam thermal lens technique. The study reveals that the annealing‐induced structure modifications lower the nanofluid's thermal diffusivity and unveils the existence of transition annealing temperature of MWCNTs above which the nanoparticles can make the nanofluid a heat trapper. The study also proposes the importance of making more energy‐efficient engine oils by keeping the temperature of the engine oil below the transition temperature.

Investigating the thermal effect of channel heatsink using MWCNTs nanofluids

The utilisation of Multi-walled carbon nanotubes (MWCNTs) nanofluids is considered to be a highly efficient approach in the field of thermal engineering, specifically for the purpose of cooling electronic processors. The usage of a microchannel along with an electronic chip for liquid cooling of electronics presents a compelling substitute to the conventional bulky aluminium heat sinks. A minichannel heat sink employing MWCNTs nanofluid as a coolant is further enhanced in thermal and hydraulic performance. In order to analyze the performance of the minichannel heat sinks, a conjugate heat transfer model has been solved using the commercial software ANSYS-CFD. Theoretically, it showed that the presence of MWCNTs reduced thermal resistance and increased the thermal conductivity of liquid cooling system. The results reveal a maximum enhancement of in average heat transfer coefficient ( h ) for minichannel heat sink using MWCNTs as a coolant at volume 40%, 46%, and 52% concentrations of 0.25%, 0.5% and 0.75%. The performance evaluation shows that the overall performance of the minichannel heat sink using MWCNTs cooled minichannel heat sink at 0.75% volume concentration is roughly enhanced more as compared to water.

Computation of Stagnation Point Convection Flow of Carbon Nanotube Nanofluids From a Stretching Sheet With Melting: Dual Solutions

Abstract A theoretical study in stagnation point flow is presented where melting heat transfer effects of carbon nanotube (CNT) from a stretching surface is appeared. Both carbon nanotubes like single-wall CNT (SWCNT) and multiwall CNT (MWCNT) are homogeneously dispersed in the base fluid. As the ordinary (or base) fluids, water and kerosene oil are employed. A set of nonlinear ordinary differential equations with appropriate boundary conditions is formed by transforming the governing equations via similarity transformations. The transformed nonlinear ordinary differential equations are then solved numerically using the bvp4c solver in matlab, an efficient numerical finite difference method. The impact of nanoparticle volume fraction, velocity, melting, stretching parameter, and CNT type on transport characteristics are explored and visualized graphically and in tabular forms. Verification of the matlab computations with available data in certain limiting cases is included showing excellent agreement. Existence of dual (upper and lower branch) solution is shown for a certain range of stretching sheet parameter. The obtained dual solutions are examined for velocity and temperature in detail. A stability analysis demonstrates that the first solution is a stable solution, and the second solution is an unstable solution. Local skin friction and local Nusselt number are also computed in order to determine critical values that can permit dual solutions. It is observed that when a dimensionless melting parameter is greater than 1, SWCNT nanofluids attain greater velocities than MWCNT nanofluids for water as well as kerosene oil base fluids. Moreover, the flow is accelerated for SWCNT compared with MWCNT for both water and kerosene oil. With increasing stretching parameter, the heat transfer rate (Nusselt number) increases, whereas skin friction coefficients decrease. Higher skin friction and Nusselt number are obtained for SWCNTs compared to MWCNTs due to their greater density and thermal conductivity. The study is relevant to phase change manufacturing fluid dynamics of nanomaterials.

ANFIS based effectiveness and number of transfer units predictions of MWCNT/water nanofluids flow in a double pipe U-bend heat exchanger

In this study, the heat transfer coefficient, Nusselt number, effectiveness and number of transfer units of water mixed multi-walled carbon nanotubes nanofluids passes through a tube-in-tube heat exchanger was experimentally investigated. Investigations were performed in the operating conditions of Reynolds number ranging from 3500 to 12000 and volume concentrations ranging from 0% to 0.3%, respectively. The obtained four parameters were predicted using adaptive neuro fuzzy inference system (ANFIS). The Reynolds number and particle volume loadings are the input data in artificial neural network analysis and heat transfer coefficient, Nusselt number, effectiveness and number of transfer units is output or target. The Nusselt number, heat transfer coefficient, effectiveness, and number of transfer units was enhanced to 31.3%, 44.17%, 2.51% and 2.76% at φ = 0.3% and at a Re of 10005, against base fluid. Implementation of ANFIS with various quantities of neurons in the mid layer provides 1–10−6 with the correlation coefficient (R2) of 0.9978, and 0.9998 and root mean square error of 0.0018581, and 0.0014159 for heat transfer coefficient and Nusselt number, respectively. The above developed structure has been successful in predicting 96% of variation in all the parameters.

Comparisons of thermal performances in a pulsating heat pipe by using a nanofluid and a self-rewetting nanofluid with carbon nanotubes

Heat transfer performances of the ultrapure water, n-butanol self-rewetting fluid (SRF), multi-walled carbon nanotubes (MWCNTs) nanofluid (NF), and n-butanol self-rewetting MWCNTs nanofluid (SRNF) were investigated in a pulsating heat pipe (PHP). The highlight of this study was to analyze their thermal performances under different heating powers, inclination angles, and ambient temperatures. Experimental results indicated that all functional working fluids generally gave advantages in thermal transport performances relative to the ultrapure water in most cases. Furthermore, advantage of the SRF gradually emerged with increasing thermal input when compared with the ultrapure water and its enhancement ratio reached a maximum of 22%. In contrary, advantage of NF was demonstrated only when the thermal input exceeded 20W, and its enhancement percentage reached 16% at 35W. The SRNF exhibited an outstanding increase of the thermal transfer performance at a low heating power range. The augmented percentage of the SRNF was around 7–17% with the maximum value obtained at 35 W. The inclination angle also had a non-negligible impact on thermal performances of different working fluids, particularly, their thermal transfer limits in the PHP. In addition, a lower ambient temperature could generally raise the heat transmission performance of the PHP with operating fluids.

Exergy efficiency and entropy analysis of MWCNT/Water nanofluid in a thermosyphon flat plate collector

The thermal efficiency, Nusselt number, exergy efficiency, thermal entropy generation, and frictional entropy generation of natural circulation of water-based multi-walled carbon nanotubes nanofluids flow in a flat plate collector was analyzed experimentally in this paper. The experiments were conducted between the time duration from 09:00 to 16:30 hr, with particle volume loading ranging from 0 % to 0.3 % under outdoor conditions. Results show that the heat transfer coefficient, Nusselt number, and exergy efficiency increase gradually from 09:00 hr reaching a maximum value at 13:00 hr, and then decreases gradually until the end of the test at 16:30 hr, Hence, in the analysis of the results, the experimental time duration is divided into two durations: time duration-1 (09:00 to 13:00 hr) and time duration-2 (13:00 to 16:30 hr). Dynamic regression equations were developed for Nusselt number and friction factor for time durations 1 and 2. At the peak value of 13:00 hr, the thermal efficiency of the flat plate collector increased from 27.78 % for water to 56.69 % for with 0.3 vol% nanofluid; the exergy efficiency increased from 0.5 % to 2.67 %. Compared to water, the results show that the Nusselt number of 0.3 vol% of nanoparticle in water is higher by 18.01 %; and the friction factor is higher by 13.05 %; the thermal entropy generation is lower by 2.378 %. Using genetic algorithm, the thermal and exergy efficiencies of 52.4 % and 2.59 % are found at an optimal mass flow rate of MWCNT/water in flat plate collector of 0.0243 kg/s and an inlet temperature of 48.2 °C.

Energy, economic and environmental analysis of an evacuated tube solar collector using hybrid nanofluid

Hybrid nanofluids are novel advanced fluids that improve sustainable energy production. In the current study, the performance of the evacuated tube solar collector is experimentally investigated using hybrid nanofluids of magnesium oxide and multi-walled carbon nanotubes with water base. The experiments are carried out at various weight ratios and at three flow rates ranging from 1 to 3 L/min. The results show an improvement in the optical efficiency of the collector by up to 78.1% with the increase in the weight ratio of multi-walled carbon nanotubes nanoparticles. The average heat energy gain has increased from 240 W to 495 W. The utilization of the hybrid nanofluid shows an enhancement in the inlet–outlet temperature difference of the fluid by 56% and a reduction in the area of the collector by 36%. Economic and environmental analyses are conducted to investigate the role of magnesium oxide/multi-walled carbon nanotubes hybrid nanofluid in energy savings and CO2 emission reduction. The period for Carbon Payback Time and Simple Payback Period declines by 36.2% and 34.6%, respectively, for magnesium oxide/multi-walled carbon nanotubes (50:50) hybrid nanofluid. The Energy Yield Factor reaches 27.09 throughout the lifetime of the collector. According to the findings, magnesium oxide/multi-walled carbon nanotubes hybrid nanofluid is a viable working fluid alternative to multi-walled carbon nanotubes nanofluid that provides enhanced properties and a more economical raw material cost.

An experimental study integrated with prediction using deep learning method for active/passive cooling of a modified heat sink

In this paper, the effects of various cooling methods for electronic chipsets integrated with a deep learning algorithm are studied. For this purpose, the separated and simultaneous impacts of active/passive cooling methods on the thermal management of a modified heat sink are experimentally investigated. As active methods, two modules of circulating liquid flow and fan are employed. For the circulating liquid flow, distilled water and multiwalled carbon nanotubes (MWCNT) nanofluid, with flow rates in the range of 50–150 ml/min, pass through the heat sink which is attached to a printed circuit board (PCB) where heat fluxes in the range of 20000–40000 W/m2 are generated. For the fan, two modes of 4.5 and 9 W are applied in order to generate air forced convection. Regarding the passive methods, a phase change material (PCM) and nano-phase change material (NPCM) are integrated with the heat sink; paraffin is used as a PCM while MWCNT is added into paraffin to prepare NPCMs with mass fractions of 0.5 % and 1 %. The results show that employing a combination of MWCNT nanofluid flow, air forced convection, and NPCM with 0.5 % mass fraction leads to the best thermal performance where the PCB maximum temperatures of 29.9, 34.4, and 39.4 °C are measured under heat fluxes of 20000, 30000, and 40000 W/m2, respectively. Applying a hybrid configuration where all active and passive cooling methods are utilized, may enhance the mean heat transfer coefficient by a substantial amount (e.g., 42.7 % for 20000 W/m2) compared to the case where only circulating water flow is used. This observation demonstrates the high potential of hybrid methods for the purpose of cooling electronic chipsets. Next, to predict the temperature of the PCB during the operation under different working conditions, various deep learning algorithms are considered. These algorithms include reinforcement learning-group method of data handling (RL-GMDH), multi-layer perceptron (MLP), radial basis function (RBF), support vector regression with the linear kernel (SVRL), and Gaussian kernel (SVRG). The RL-GMDH algorithm is found to result in the best prediction for the PCB temperature (up to 30 s during the operation) which agree well with those of the experiments for various intermittent/continuous operation loads. The predictions of this learning algorithm can open a new approach for the controlling systems to prevent overheating of the electronic chipsets.

Cattaneo–Christov heat flux model and multiple slip effect on carbon nanofluid over a stretching sheet in a Darcy–Forchheimer porous medium

AbstractIn several biotechnological processes, multiple slips are the most paramount, such as blood pumping from the heart to different body components, endoscopy treatment, pabulum distribution, and the heat transport phenomenon regulation. In the current research, we have studied the multiple slips, Darcy–Forchheimer, and Cattaneo–Christov heat flux model on a stretching surface exposed to magnetic carbon nanotube nanofluid. We have additionally included a heat source or sink, a chemical reaction for manipulating the heat and mass transport phenomena. The resulting governing partial differential equations have been transformed into ordinary differential equations. With the Runge–Kutta–Fehlberg fourth–fifth‐order procedure, the transformed governing equations are numerically solved. Numerical solutions for different parameters for velocity, temperature, and concentration profiles (Eckert number, velocity slip, thermal slip, mass slip, etc.) are highlighted. Graphical and numerical results for the various parameters in the modeled problem have been outlined. The present numerical results are compared with the published ones for some limiting cases. The slip has been found to control the flow of the boundary layer.

Optimizing the heat transfer characteristics of MWCNTs and TiO2 water-based nanofluids through a novel designed pilot-scale setup

This study aimed to investigate the effect of titanium dioxide (TiO2) nano additives on the thermal performance of a pilot-scale cross-flow cooling tower. Moreover, it is a continuation of our previous study on the effect of using multi-walled carbon nanotubes (MWCNTs) nanofluid, and the results were compared with the results of TiO2 and previous work. An experimental design by response surface methodology (RSM) based on central composite design (CCD) with two factors (concentration and flow rate) was used to study the effectiveness of the setup, Merkel number, and the cooling range. The nanofluids were prepared by the two-step method. The stability tests were performed considering different surfactants such as Gum Arabic, Triton X-100, and sodium dodecyl sulfate, and Gum Arabic was determined as the optimal surfactant. The visual method, dynamic light scattering (DLS), and Zeta potential analyses were used to ensure the stability of the nanofluids and determine the size distribution of the nanoparticles in the nanofluids. The findings revealed that the heat transfer characteristics of the working fluid were improved with the addition of nanoparticles. Moreover, by comparing the effect of nanoparticles, it was found that MWCNTs could enhance the thermal features better than TiO2. The nanofluid containing 0.085 wt% of the MWCNTs improves the Merkel number, effectiveness, and cooling range by 28, 10.2, and 15.8%, respectively, whereas these values for TiO2 containing nanofluids are 5, 4.1, and 7.4%, respectively. MWCNTs nanofluid with a concentration of 0.069 wt% and a flow rate of 2.092 kg/min was proposed for optimal system setup. Under these conditions, the cooling range, effectiveness, and Merkel number were about 23.5, 55.75%, and 0.64, respectively.

Solvent-Free Carbon Nanotube Nanofluid-Reinforced Copper Matrix Composites with Enhanced Mechanical Properties

Solvent-free nanofluid displays liquid-like function in the absence of solvent at room temperature by grafting organic salts on the surface of materials. In this study, carbon nanotube (CNT) fluid is synthesized by a chemical grafting method for the preparation of CNTs/copper (Cu) composite powder. After hot-pressing and sintering, the CNTs-fluid/Cu composites are further treated by hot rolling to improve their mechanical properties. The microstructure and mechanical properties of the as-obtained composites are systematically characterized by SEM, TEM, FTIR, Raman, rheological analysis, hardness and tensile tests. It is demonstrated that the optimal mechanical properties of the composite can be achieved by adding 0.75[Formula: see text]wt.% CNTs nanofluid. The yield and tensile strength of the resultant material are about 397.6[Formula: see text]MPa and 517.5[Formula: see text]MPa, respectively, which are 282% and 156% higher than that of pure Cu. Meanwhile, its hardness value reaches 152.2[Formula: see text]HV, which is increased by 27% and 38% of pure Cu and the unrolled sample, respectively. Such significant property improvement is conjointly contributed by load transfer strengthening, Orowan strengthening, matrix strengthening and thermal mismatch. This study provides a new insight into the interface structure to enhance the mechanical properties of metal matrix composites.

Rotating Flow and Heat Transfer of Single-Wall Carbon Nanotube and Multi-Wall Carbon Nanotube Hybrid Nanofluid with Base Fluid Water over a Stretching Sheet

In this article, numerical simulations of the rotational flow of water-based magnetohydrodynamic (MHD) nanofluid containing single-wall carbon nanotube (SWCNT) and hybrid nanofluid containing single- and multiple-wall carbon nanotube (SWCNT-MWCNT) over a stretching sheet are performed. The primary goal is to improve thermal transport efficiency due to CNTs extraordinary thermal conductivity. The 3D governing equations for microorganism concentration, energy, momentum, concentration, and mass conservation are transformed into 1D ordinary differentiation via similarity transformations. In a MATLAB environment, the resultant system of equations (ODEs) are then solved using Runge–Kutta fourth order with the shooting process. Tables and graphs were used to show the results of physical parameters. According to our findings, enhancing the rotational parameter λ and the magnetic field M reduce the base fluid velocity along the x-axis, and on the other hand, the opposite tendency is shown along the y-axis. Furthermore, the velocities, temperature, and microorganism concentration profiles of hybrid nanofluid (SWCNT−MWCNT/H2O) are found to be higher than those of mono nanofluid (H2O+SWCNT), while the concentration profile is found to be lower.

Lubrication Mechanisms of a Nanocutting Fluid with Carbon Nanotubes and Sulfurized Isobutylene (CNTs@T321) Composites as Additives

Developing high-efficiency lubricant additives and high-performance green cutting fluids has universal significance for maximizing processing efficiency, lowering manufacturing cost, and more importantly reducing environmental concerns caused by the use of conventional mineral oil-based cutting fluids. In this study, a nanocomposite is synthesized by filling sulfurized isobutylene (T321) into acid-treated carbon nanotubes (CNTs) with a liquid-phase wet chemical method. The milling performance of a nanocutting fluid containing CNTs@T321 composites is assessed using a micro-lubrication technology in terms of cutting temperature, cutting force, tool wear, and surface roughness. The composite nanofluid performs better than an individual CNT nanofluid regarding milling performance, with 12%, 20%, and 15% reductions in the cutting force, machining temperature, and surface roughness, respectively. The addition of CNTs@T321 nanocomposites improves the thermal conductivity and wetting performance of the nanofluid, as well as produces a complex lubricating film by releasing T321 during machining. The synergistic effect improves the cutting state at the tool–chip interface, thereby resulting in improved machining performance.

Hybrid Plasma-Liquid Functionalisation for the Enhanced Stability of CNT Nanofluids for Application in Solar Energy Conversion.

Macroscopic ribbon-like assemblies of carbon nanotubes (CNTs) are functionalised using a simple direct-current-based plasma–liquid system, with oxygen and nitrogen functional groups being added. These modifications have been shown to reduce the contact angle of the ribbons, with the greatest reduction being from 84° to 35°. The ability to improve the wettability of the CNTs is of paramount importance for producing nanofluids, with relevance for a number of applications. Here, in particular, we investigate the efficacy of these samples as nanofluid additives for solar–thermal harvesting. Surface treatments by plasma-induced non-equilibrium electrochemistry are shown to enhance the stability of the nanofluids, allowing for full redispersion under simulated operating conditions. Furthermore, the enhanced dispersibility results in both a larger absorption coefficient and an improved thermal profile under solar simulation.

Impact of a hot constructal tree-shaped fin on the convection flow of single wall carbon nanotube water nanofluid inside a sinusoidal enclosure

Heat transfer due to natural convection in different types of fins embedded closed enclosures are widely used in various fields including petrochemicals, solar collectors, heat exchangers, gas turbines, semiconductor devices, automobile radiators, etc. Herein, the natural convection flow of a water-based single-wall carbon nanotube (SWCNT) nanofluid inside a novel sinusoidal closed geometry is investigated. The horizontal bottom and top boundaries of the enclosure are presumed to be hot and thermally adiabatic, respectively. The left and right vertical sinusoidal boundaries are assumed to be cold. A hot constructal tree-shaped fin is placed at the center of the hot bottom wall. The impact of the simple constructal heated tree-shaped fin on steady, two-dimensional, laminar, and incompressible flow of the water-based SWCNT nanofluid inside the sinusoidal enclosure is analyzed. The mathematical formulation of water-based SWCNT nanofluid flow inside the enclosure is formulated using the Navier–Stokes equations under the Boussinesq approximation. A modified effective thermal conductivity model of carbon nanotubes including the radius of water molecules and carbon nanotubes is employed. Galerkin finite element simulations are conducted to study the flow and heat transfer characteristics via stream function, isotherms, local Nusselt number, and averaged Nusselt number graphs. The combined effect of the amplitude of the sinusoidal wall (A = 0.1, 0.15, and 0.2) with the Rayleigh number (Ra = 104–106), nanotube volume fraction (φ = 0.01–0.05), and the thickness of the tree-shaped fin (B = 0.02–0.06) are comprehensively studied. The temperature gradient decreases with increasing nanotube volume fraction and the sinusoidal wall amplitude, while it increases above the fin with the thickness of the tree-shaped fin. Moreover, the averaged Nusselt number increases with the thickness of the tree-shaped fin by 14.72%, 16.74%, and 19.6% for A = 0.1, 0.15, and 0.2 along the fin, respectively. The averaged Nusselt number along the fin is an increasing function of the Rayleigh number, nanotube volume fraction, thickness of the tree-shaped fin, and amplitude of waviness. Additionally, a novel correlation for the averaged Nusselt number along the fin is derived.

Radiative Darcy-Forchheimer Micropler Bödewadt flow of CNTs with viscous dissipation effect

This article aims at the examination of the three-dimensional micropolar nanofluids of single and multi-walled carbon nanotubes (CNTs) dissolved in water and gasoline liquids for the first time reported to the case of so-called classical Bo¨dewadt flow, which occurs when a fluid rotates at an adequate great distance out of a static disk. The static disk is then stretched linearly in the radial direction. The Darcy-Forchheimer porous media are also taken into account. Energy equation is investigated in existence of convection and radiation. The effect of viscous dissipation is also taken into account. The flow field equations are converted from PDEs to ODEs using appropriate transformation. The implementation of the bvp4c technique (Shooting scheme) is used to construct solutions to these ODEs. In addition to Nusselt number, skin friction, axial velocity, radial velocity, tangential velocity, micro-rotational velocities and fluid temperature are all investigated using physical factors. The finding indicates that the volume fraction enhanced, the micro-rotational velocities enhances. The tabulation outcomes indicates that the skin friction declined for escalating values of porosity parameter and volume fraction, while Nusselt number show opposite behavior. It has been also discovered that the effect of multiple-walled CNTs is quite effective than that of single-walled CNTs. When compared to water-based fluids, gasoline oil also displays an overarching trend.

Three-dimensional analysis of combined thermal–solutal buoyancy and capillary convection of water-based micropolar multi-walled carbon nanotubes nanofluids

Three-dimensional analysis of combined thermal–solutal buoyancy and capillary convection of water-based micropolar multi-walled carbon nanotubes nanofluids

Heat transfer enhancement and entropy generation minimization using CNTs suspended nanofluid upon a convectively warmed moving wedge: An optimal case study

AbstractThis paper aims to examine the effects of singleand multi‐walled carbon nanotubes (CNTs) nanoparticles on heat transfer enhancement and inherent irreversibility in the boundary layer of water base nanoliquid flow over a convectively heated moving wedge with thermal radiation. Manipulation of the angle positioning towards the flow stream provides the opportunity for comparing physical aspects in the flow states, where three main geometries of the well‐known Falkner–Skan problem include: (i) the flat plat (named Blasius flow), (ii) the wedge, and (iii) the vertical plate (named Hiemenz stagnation flow) have been considered to present a comprehensive development of this significant problem. Applying suitable similarity constraints, the model partial differential equations are transformed into a set of nonlinear ordinary differential equations. Solutions are obtained analytically via optimal homotopy asymptotic method and numerically via shooting technique coupled with the Runge–Kutta–Fehlberg fourth–fifth scheme. The impacts of solid volume fraction of carbon nanoparticles along with other germane factors, such as wedge angle, velocity ratio parameter, Biot number, thermal radiation, and so forth on velocity and thermal profiles, Nusselt number, heat transfer enhancement, rate of entropy generation, and irreversibility ratio, are scrutinized via graphical simulations and discussed. Optimization of such entropy developments in the system was found to depend on geometrical (β), dynamical (λ), and thermophysical (Bi, NR, Ec, φ) parameters. The ultimate objective of reducing the energy loss and enhancing heat transference was obtained with the geometrical manipulation of a flat plate case (β = 0). Dynamically (λ = 1) were spotted to exert the best fluidity irrespective of obstacle shapes (wedge or plate) in its way. In thermophysical aspects, reducing the convective heating develops a favorable situation for attaining the optimal balance between energy loss and heat transfer. SWCNT/water could be the better choice with enhanced thermal transference ability and exerts minimal irreversibility to overshadow the influences of all the above‐mentioned factors. The SWCNT suspended nanofluid can provide 12%–64% heat transfer enhancement when compared with the multiwalled CNT nanofluid which ranges from over 11% to 58% heat transference rate.

Experimental study on thermal performances of flat-plate pulsating heat pipes under static and swing conditions

Pulsating heat pipe (PHP), as an efficient heat transfer component, can be used for waste heat recovery and electronic cooling. The influences of typical ocean motions, such as inclination and swing, on thermal performances of PHPs are inevitable for practical offshore applications. In this study, surfactant-free functionalized multi-walled carbon nanotubes (f-MWCNTs) nanofluids with long-term stability were prepared. Thermal performances of PHP with f-MWCNTs nanofluids and mixed fluids under static and swing conditions were comparatively investigated. Results indicate that 0.25 mg/ml f-MWCNTs nanofluids (base fluid, 1:1 ethanol-DI water) shows the lowest thermal resistance among all working fluids. Thermal performances of flat-plate PHP with ethanol-DI water mixed fluids are better than that of ethanol-based f-MWCNTs nanofluids, and HFE-7100-DI water mixed fluids are more suitable for performance enhancements at the lower heat loads. As for effects of swing motion, the increased swing amplitudes and decreased swing periods will reduce thermal performances. In the worst case, swing motions can reduce thermal performances by 5.85%. Moreover, frequencies of temperature difference fluctuations increase with the decrease of swing periods. Although the change of swing amplitudes has a certain effect on frequencies and amplitudes of temperature difference fluctuations, but the influence seems negligible as well. These results can be used to guide practical offshore applications of PHPs.