Numerical and experimental investigation of flat-plate pulsating heat pipes with extra branches in the evaporator section

Sedighi, Erfan; Amarloo, Ali; Shafii, Behshad

doi:10.1016/j.ijheatmasstransfer.2018.05.047

Cited by 31 publications

(8 citation statements)

References 22 publications

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“…Sedighi et al [152] simulated a 4-branch PHP with an extra dead-end tube attached to the evaporator (to provide the circulation regime) in the bottom-heated mode. The 2D VOF OpenFoam approach was used with ∼ 10 cells across the channel.…”

Section: D and 3d Php Simulationsmentioning

confidence: 99%

Physical principles and state-of-the-art of modeling of the pulsating heat pipe: A review

Nikolayev

2021

Applied Thermal Engineering

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The Pulsating (called also oscillating) Heat Pipe (PHP) is a high performance passive heat transfer device. It consists in a closed capillary channel folded into several meanders, evacuated, and partially filled with a liquid and its vapor. One side is in thermal contact with a hot spot, the other with a cold spot. The oscillation of the liquid plugs and vapor bubbles spontaneously occurs after the heating beginning. The heat exchange takes place not only by latent heat transfer, but also by liquid convection. Both this advantage and the PHP structural simplicity make it competitive with respect to other kinds of heat pipes. However, the PHP operation is non-stationary and depends on many physical and material parameters. As a result, application of empirical correlations is quite unsuccessful. More sophisticated direct modeling is thus required. In this review, we present the past, present, and future perspectives of the theoretical PHP studies. The physical phenomena on the level of a single bubble and single liquid plug is addressed first. In this context, the modeling of the simplest, single branch PHP is described as a necessary first step toward the PHP understanding and model validation. The modeling of interaction between the bubbles and plugs (bubble generation and disappearance, plug evaporation) is discussed next. Finally, the state of the art of the physical modeling and simulation of the multi-turn PHP is reviewed and the difference between existing approaches is explained.

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Section: D and 3d Php Simulationsmentioning

confidence: 99%

Physical principles and state-of-the-art of modeling of the pulsating heat pipe: A review

Nikolayev

2021

Applied Thermal Engineering

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“…Numerous efforts have been carried out to seek improvement in the performance of PHPs by changing the structure. Sedighi et al 13 embedded external branches in the evaporator section of a flat‐plate PHP to perform the role of a pump which intensified the circulation of fluid inside the PHP. Using this novel structure, a 17% improvement in the performance of PHP was achieved.…”

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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“…The heat energy is directly delivered by the oscillation motion of working fluids in PHP. The thermal performance of PHP varied from different parameters, which are the operation parameters (eg, inclination angle and filled ratio), 10,11 thermodynamics parameters (eg, working fluids and surfactant solution), 12‐24 and geometric parameters (eg, cross‐section shape, inner diameter, turns, and heat pipe materials) 25‐29 . Especially, it is much more worth to further discuss the effect of thermodynamic parameters on the heat transfer mechanism of PHP.…”

Section: Introductionmentioning

confidence: 99%

Effect of ultrasonic on the enhancement of heat transfer for pulsating heat pipe

Zhang

Jiang

et al. 2021

Int J Energy Res

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Summary The pulsating heat pipe (PHP) has become one of the most promising devices to dramatically remove heat for electronic devices. This work focuses on the experimental investigation of ultrasonic on the enhancement of heat transfer of PHP, and further discusses this effect at the different working fluids. The results indicate that the external region of PHP exhibits more intense oscillation motion of working fluids than that of internal‐region. The heat transfer performance enhanced assisted with the ultrasonic at the heating power of 5 to 20 W but deteriorated at 25 W. For details, the heat transfer coefficient (HTC) increased 72.6%, and the internal and external start‐up times reduced 57.8% and 2.2%, respectively. Furthermore, the numerous vapors confirm that the ultrasonic cavitation would effectively accelerate the phase transition. Finally, it also discusses the couple effect between the ultrasonic and different working fluids on heat transfer coefficient. The maximum HTC of 1.85 is obtained at the heating power of 15 W for the PHP charged with acetone. In addition, the trend of HTC of PHP filled with acetone shows much more stable assisted with ultrasonic varying from the heating power inputs. Highlights The thermal performance was revealed by internal and external region of PHP The directly enhanced method of ultrasonic cavitation was introduced The novel index of the heat transfer coefficient (HTC) was proposed The couple effect ultrasonic on the enhancement of heat transfer was discussed with different working fluids

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Numerical and experimental investigation of flat-plate pulsating heat pipes with extra branches in the evaporator section

Cited by 31 publications

References 22 publications

Physical principles and state-of-the-art of modeling of the pulsating heat pipe: A review

Physical principles and state-of-the-art of modeling of the pulsating heat pipe: A review

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

Effect of ultrasonic on the enhancement of heat transfer for pulsating heat pipe

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