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Keywords = hollow paddle

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15 pages, 7257 KiB  
Article
Numerical Simulation and Design of a Shaftless Hollow Pump for Plankton Sampling
by Shizhen Gao, Zhihua Fan, Jie Mao, Minhui Zheng and Junyi Yang
J. Mar. Sci. Eng. 2024, 12(2), 284; https://doi.org/10.3390/jmse12020284 - 4 Feb 2024
Viewed by 1561
Abstract
It is important to marine ecology research that plankton samples are collected without damage, especially for time series samples. Usually, most fixed-point plankton samplers are made using a pump with paddle blades in order to increase the flow rate. But it can easily [...] Read more.
It is important to marine ecology research that plankton samples are collected without damage, especially for time series samples. Usually, most fixed-point plankton samplers are made using a pump with paddle blades in order to increase the flow rate. But it can easily injure soft plankton. In this paper, a shaftless hollow sampling pump is designed, which can provide a highly efficient driving component for the plankton sampler. The numerical model of the sampling pump is established, and the flow rate of the sampling pump at different rotational speeds is simulated by the computational fluid dynamics method. In order to obtain a higher flow rate, the influence of internal and external cavity size, blade angle, and blade number on the flow rate of the sampling pump with a constant rotational speed of the blade was simulated and discussed. The results show that the flow rate at the internal cavity is positively correlated with the inlet and outlet pressure differences of the internal cavity, and the greater the negative pressure at the outlet of the internal cavity, the greater the flow rate. When the internal and external cavity sizes are h = 14 mm, d = 52 mm, blade angle θ = 45°, and number of blades s = 5, the flow rate of the sampling pump internal cavity reaches the maximum. Finally, the feasibility of the shaftless hollow sampling pump is verified by experiments. The shaftless hollow sampling pump can realize non-destructive sampling of plankton. This paper presents a theoretical design foundation for a new non-destructive siphon sampling method for marine plankton, which is of great significance for marine plankton sampling and subsequent research. Full article
(This article belongs to the Special Issue Innovation in Material and Design of Underwater Structures)
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18 pages, 8379 KiB  
Article
Investigation of a Novel Ultra-Low-Frequency Rotational Energy Harvester Based on a Double-Frequency Up-Conversion Mechanism
by Ning Li, Hu Xia, Chun Yang, Tao Luo and Lifeng Qin
Micromachines 2023, 14(8), 1645; https://doi.org/10.3390/mi14081645 - 20 Aug 2023
Cited by 3 | Viewed by 2289
Abstract
Due to their lack of pollution and long replacement cycles, piezoelectric energy harvesters have gained increasing attention as emerging power generation devices. However, achieving effective energy harvesting in ultra-low-frequency (<1 Hz) rotational environments remains a challenge. Therefore, a novel rotational energy harvester (REH) [...] Read more.
Due to their lack of pollution and long replacement cycles, piezoelectric energy harvesters have gained increasing attention as emerging power generation devices. However, achieving effective energy harvesting in ultra-low-frequency (<1 Hz) rotational environments remains a challenge. Therefore, a novel rotational energy harvester (REH) with a double-frequency up-conversion mechanism was proposed in this study. It consisted of a hollow cylindrical shell with multiple piezoelectric beams and a ring-shaped slider with multiple paddles. During operation, the relative rotation between the slider and the shell induced the paddles on the slider to strike the piezoelectric beams inside the shell, thereby causing the piezoelectric beams to undergo self-excited oscillation and converting mechanical energy into electrical energy through the piezoelectric effect. Additionally, by adjusting the number of paddles and piezoelectric beams, the frequency of the piezoelectric beam struck by the paddles within one rotation cycle could be increased, further enhancing the output performance of the REH. To validate the output performance of the proposed REH, a prototype was fabricated, and the relationship between the device’s output performance and parameters such as the number of paddles, system rotation speed, and device installation eccentricity was studied. The results showed that the designed REH achieved a single piezoelectric beam output power of up to 2.268 mW, while the REH with three piezoelectric beams reached an output power of 5.392 mW, with a high power density of 4.02 μW/(cm3 Hz) under a rotational excitation of 0.42 Hz, demonstrating excellent energy-harvesting characteristics. Full article
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19 pages, 6115 KiB  
Article
Thermal Stress and Deformation of Hollow Paddle-Shaft Components with Internal High Temperature Molten Salt Flow
by Taha Rajeh, Basher Hassan Al-Kbodi and Houlei Zhang
Processes 2020, 8(12), 1557; https://doi.org/10.3390/pr8121557 - 27 Nov 2020
Cited by 3 | Viewed by 2993
Abstract
Excessive thermal stress and deformation are important reasons causing disservice of high temperature heat exchangers. This paper presents thermal stress and expansion analysis of single-leaf type hollow paddle-shaft components with internal high temperature molten salt flow based on three-dimensional numerical simulations. The results [...] Read more.
Excessive thermal stress and deformation are important reasons causing disservice of high temperature heat exchangers. This paper presents thermal stress and expansion analysis of single-leaf type hollow paddle-shaft components with internal high temperature molten salt flow based on three-dimensional numerical simulations. The results show that the hollow paddles enhance the heat transfer and decrease the maximum thermal stress simultaneously with the expense of a much higher pressure drop than that of solid paddles. The cumulative von Mises stress distribution curve shows that the stress distribution of the component with hollow paddles is more uniform than that with solid paddles. The radial and axial deformations do not differ much for the components with hollow and solid paddles. A larger volume of the fluid space in the hollow paddles leads to stronger heat transfer, smaller maximum thermal stress, and more uniform stress distribution. The effects of the paddle height, the diameter and number of flow holes, the molten salt flow rate, and the material-side heat transfer coefficient are identified. The advantages of hollow paddle designs in both heat transfer and thermal stress (local and overall) performance are revealed. The work in this study can provide a reference for the design and optimization of hollow paddle heat exchangers with high temperature molten salt as working fluid. Full article
(This article belongs to the Special Issue Modelling and Experimental Investigation of Fluid Flows Systems)
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19 pages, 7878 KiB  
Article
Thermo-Fluid Characteristics of High Temperature Molten Salt Flowing in Single-Leaf Type Hollow Paddles
by Taha Rajeh, Ping Tu, Hua Lin and Houlei Zhang
Entropy 2018, 20(8), 581; https://doi.org/10.3390/e20080581 - 7 Aug 2018
Cited by 4 | Viewed by 4056
Abstract
A single-leaf type paddle heat exchanger with molten salt as the working fluid is a proper option in high temperature heating processes of materials. In this paper, based on computational fluid dynamics (CFD) simulations, we present the thermo-fluid characteristics of high temperature molten [...] Read more.
A single-leaf type paddle heat exchanger with molten salt as the working fluid is a proper option in high temperature heating processes of materials. In this paper, based on computational fluid dynamics (CFD) simulations, we present the thermo-fluid characteristics of high temperature molten salt flowing in single-leaf type hollow paddles in the view of both the first law and the second law of thermodynamics. The results show that the heat transfer rate of the hollow paddles is significantly greater than that of solid paddles. The penalty of the heat transfer enhancement is additional pressure drop and larger total irreversibility (i.e., total entropy generation rate). Increasing the volume of the fluid space helps to enhance the heat transfer, but there exists an upper limit. Hollow paddles are more favorable in heat transfer enhancement for designs with a larger height of the paddles, flow rate of molten salt and material-side heat transfer coefficient. The diameter of the flow holes influences the pressure drop strongly, but their position is not important for heat transfer in the studied range. Other measures of modifying the fluid flow and heat transfer like internal baffles, more flow holes or multiple channels for small fluid volume are further discussed. For few baffles, their effects are limited. More flow holes reduce the pressure drop obviously. For the hollow paddles with small fluid volume, it is possible to increase the heat transfer rate with more fluid channels. The trade-off among fluid flow, heat transfer and mechanical strength is necessary. The thermo-fluid characteristics revealed in this paper will provide guidance for practical designs. Full article
(This article belongs to the Special Issue Entropy Generation and Heat Transfer)
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