Numerical and experimental investigations of hybrid nanofluids on pulsating heat pipe performance

Zufar, Muhammad; Gunnasegaran, Prem; Kumar, Harsha; Ng, Khai Ching

doi:10.1016/j.ijheatmasstransfer.2019.118887

Cited by 89 publications

(21 citation statements)

References 40 publications

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“…Pandya et al [22] charged an axial grooved heat pipe with a hybrid nanofluid composed of CeO 2 -MWCNT and observed that using this working fluid led to 30% lower thermal resistance compared with the case of using water as the working fluid. Aside from the abovementioned applications, using hybrid nanofluids in other types of thermal mediums, such as pulsating heat pipes, could result in the improvement of performance [23].…”

Section: Introductionmentioning

confidence: 99%

Thermophysical Properties of Hybrid Nanofluids and the Proposed Models: An Updated Comprehensive Study

et al. 2021

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Thermal performance of energy conversion systems is one of the most important goals to improve the system’s efficiency. Such thermal performance is strongly dependent on the thermophysical features of the applied fluids used in energy conversion systems. Thermal conductivity, specific heat in addition to dynamic viscosity are the properties that dramatically affect heat transfer characteristics. These features of hybrid nanofluids, as promising heat transfer fluids, are influenced by different constituents, including volume fraction, size of solid parts and temperature. In this article, the mentioned features of the nanofluids with hybrid nanostructures and the proposed models for these properties are reviewed. It is concluded that the increase in the volume fraction of solids causes improvement in thermal conductivity and dynamic viscosity, while the trend of variations in the specific heat depends on the base fluid. In addition, the increase in temperature increases the thermal conductivity while it decreases the dynamic viscosity. Moreover, as stated by the reviewed works, different approaches have applicability for modeling these properties with high accuracy, while intelligent algorithms, including artificial neural networks, are able to reach a higher precision compared with the correlations. In addition to the used method, some other factors, such as the model architecture, influence the reliability and exactness of the proposed models.

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Section: Introductionmentioning

confidence: 99%

Thermophysical Properties of Hybrid Nanofluids and the Proposed Models: An Updated Comprehensive Study

et al. 2021

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“…Their experimental results show that thermal boundary layer disturbance and nanoparticles have significant promoting effects on heat transfer enhancement, and the Nusselt number of pulsating flow is also higher than that of continuous flow. In addition, Zufar et al [13] numerically and experimentally studied the effect of mixed nanofluids on the heat transfer performance of pulsating heat pipes. Experimental results show that, nanofluids can initiate pulses at lower heating power.…”

Section: Introductionmentioning

confidence: 99%

Numerical study on the flow and heat transfer of water-based Al2O3 forced pulsating nanofluids based on self-excited oscillation chamber structure

et al. 2022

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In this study, the flow and heat transfer characteristics of the forced pulsating Al2O3/water nanofluid were numerically studied. The pulsating excitation of the nanofluid is provided by the Helmhertz self-excited oscillating cavity. The large eddy simulation method is used to solve the equation, and the local Nusselt number and heat transfer performance index are used to analyze the heat transfer characteristics of the nanofluid in the self-excited oscillation heat exchange tube. In addition, the effect of different downstream tube diameters on heat transfer enhancement is discussed. The research results show that the existence of the countercurrent vortex can increase the disturbance of the near-wall fluid, thereby improving the mixing degree of the near-wall fluid and the central mainstream. As the countercurrent vortex migrates downstream, pulse enhanced heat transfer is realized. Furthermore, it was also found that when the downstream tube diameter d2=1.8d1, the periodic effect of the local Nusselt number of the wall is the best and the heat transfer performance index has the most stable pulsation effect within a pulsation cycle. But when d2=2.0d1, the change curve of heat transfer performance index in a pulsating period is the highest, the maximum value is 3.95.

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“…Charging a PHP with the nanofluid at the concentrations of 1% and 1.5%, they found that the concentration of 1.5% of nanoparticles leads to the best performance of the PHP. Zufar et al 28 compared the impact of two hybrid nanofluids of Al 2 O 3 –CuO and SiO 2 –CuO at the concentration of 0.1% by weight on the performance of a four‐turns PHP. It was found that in terms of PHP performance, the SiO 2 –CuO nanofluid with 57% improvement was superior to Al 2 O 3 –CuO nanofluid with 34% improvement.…”

Section: Introductionmentioning

confidence: 99%

The impacts of utilizing nano‐encapsulated PCM along with RGO nanosheets in a pulsating heat pipe, a comparative study

et al. 2021

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Summary Heat pipes are useful devices in heat transfer and particularly, in cooling systems. Given the high demand for cooling systems in various applications, an improvement in the performance of heat pipes has gained much attraction in recent years. In this study, the effects of utilizing working fluids with different thermal properties on the performance of pulsating heat pipes (PHP) are experimentally studied. Hence, nano‐encapsulated phase change material (NPCM), reduced graphene oxide nanosheets, and their mixture, as a novel hybrid nanofluid, are prepared and dispersed in water as a working fluid. NPCM at 3 concentrations of 5, 10, and 20 g/L, as well as nanosheets at three concentrations of 0.3, 0.6, and 1.2 g/L, are synthesized and investigated. Moreover, both additives are mixed at five various concentrations to form a hybrid nanofluid. All experiments are conducted in the vertical orientation and filling ratio of 50%. It is found that due to the increase in viscosity with the increment of concentration, the highest concentration is not always the optimum concentration and the PHP's performance for each additive is optimized in a specific concentration. NPCMs could prevent the working fluid's temperature to rise by changing the phase, as a result, the effective specific heat of the working fluid is slightly augmented. Also, the thermal conductivity of the working fluid increased up to 13% using nanosheets. It is illustrated that using the mixture of nanosheets and NPCM leads to a 38% decline in thermal resistance. Meanwhile, it is found that the enhancement in the thermal performance of the PHP using nanofluids is not only purely due to the increase in thermal properties of nanofluids but also due to the increase in turbulence intensity and boiling nucleation sites created by the nanoparticles. Highlights Nano‐encapsulated phase change material (PCM), reduced graphene oxide (RGO) nanosheets, and their mixture are used as working fluid in a pulsating heat pipe (PHP). The thermal performance of PHP is improved using PCM nanocapsules, RGO nanosheets, and their mixture. Nanosheets have a higher impact on the performance of PHP compared with nano‐encapsulated PCM. The better performance of PHP using RGO nanosheets is due to the higher thermal conductivity and mixing of fluid containing them compared with pure water. The better performance of PHP using nanocapsules is attributed to the better mixing of the fluid.

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Numerical and experimental investigations of hybrid nanofluids on pulsating heat pipe performance

Cited by 89 publications

References 40 publications

Thermophysical Properties of Hybrid Nanofluids and the Proposed Models: An Updated Comprehensive Study

Thermophysical Properties of Hybrid Nanofluids and the Proposed Models: An Updated Comprehensive Study

Numerical study on the flow and heat transfer of water-based Al2O3 forced pulsating nanofluids based on self-excited oscillation chamber structure

The impacts of utilizing nano‐encapsulated PCM along with RGO nanosheets in a pulsating heat pipe, a comparative study

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