Effects of heat transfer on characteristics of thermionic energy converter

2018 ◽  
Vol 96 (12) ◽  
pp. 1247-1258
Author(s):  
Weiwei Zhu ◽  
Cong Ji ◽  
Fan Gu
Keyword(s):  
Heat Transfer ◽  
Current Density ◽  
Large Scale ◽  
Thermionic Emission ◽  
Electrical Energy ◽  
Output Current ◽  
Energy Converter ◽  
Emitter Temperature ◽  
Output Characteristics ◽  
Thermionic Energy

Photon enhanced thermionic emission (PETE) is a new concept in solar energy conversion, combining thermal and photovoltaic carrier excitations with thermionic emission. A solar-power-driven thermionic energy converter operates by illuminating the solar light condensed by a large-scale Fresnel lens to convert heat energy into electrical energy. By enhancing the efficiency of converting solar radiation into the emitter internal energy, the output power and efficiency of the thermionic energy converter can be greatly improved. In this study, using numerical simulations, the effects of emitter temperature and output characteristics on a thermionic energy converter were investigated. The results showed that the higher rate of the heating power represented the higher temperature of an emitter, as well as output current density, and efficiency. In addition, by reducing the diameter of a collector and thermal conductivity of insulation materials, or increasing the diameter of emitter, the temperature of emitter, output current density, and efficiency could be notably improved. It is also worth mentioning that the main factor that affected the emitter temperature in the process of heat transfer was heat conduction between solids. In conclusion, adequate illumination, reasonable size of collector and emitter, as well as appropriate insulation measurements could efficiently improve the output characteristics of thermionic energy converter.

scholarly journals Mathematical models for thermionic emission current density of graphene emitter

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Olukunle C. Olawole ◽  
Dilip K. De ◽  
Sunday O. Oyedepo ◽  
Fabian I. Ezema
Keyword(s):  
Mathematical Models ◽  
Current Density ◽  
Coefficient Of Thermal Expansion ◽  
Thermionic Emission ◽  
Emission Current Density ◽  
Least Square ◽  
Emission Current ◽  
Two Dimensional Materials ◽  
Current Emission ◽  
Thermionic Energy

AbstractIn this study, five mathematical models were fitted in the absence of space charge with experimental data to find a more appropriate model and predict the emission current density of the graphene-based thermionic energy converter accurately. Modified Richardson Dushman model (MRDE) shows that TEC's electron emission depends on temperature, Fermi energy, work function, and coefficient of thermal expansion. Lowest Least square value of $$S=\sum {\left({J}_{th}-{J}_{exp}\right)}^{2}=0.0002 \,\text{A}^{2}/\text{m}^{4}$$ S = ∑ J th - J exp 2 = 0.0002 A 2 / m 4 makes MRDE most suitable in modelling the emission current density of the graphene-based TEC over the other four tested models. The developed MRDE can be adopted in predicting the current emission density of two-dimensional materials and also future graphene-based TEC response.

scholarly journals EQUIVALENTS OF THE PASSIVE EIGHT-EARTH POLAR WITH THREE INPUT AND FIVE OUTPUT CONCLUSIONS

2019 ◽  
Vol 20 (9-10) ◽  
pp. 109-119
Author(s):  
G. A. Bolshanyn
Keyword(s):  
Electrical Energy ◽  
Input Voltage ◽  
Individual Case ◽  
Output Current ◽  
Current Output ◽  
Input And Output ◽  
Voltage Output ◽  
The Difference ◽  
Output Characteristics ◽  
The Relationship

Eight-poles of various designs, including an eight-terminal network with three input and five output terminals, are needed to replace some power objects. Especially when only the input and output characteristics of electrical energy are of interest. The paper presents the eightterminal network equations with three input and five output terminals, establishing a connection between these characteristics. Equations of the A-form establish a connection between the input and output voltages and currents; the B-form equations establish a connection between the output and input voltages and currents; G-form equations establish a connection between the input current, output voltages and output voltage, output currents; H-form equations establish the relationship between the input voltage, output currents and output current, output voltages; the Yform equations establish a connection between the input and output currents and the input and output voltages; The Z-form equations establish the relationship between the input and output voltages and the input and output currents. When implementing these equations, attention should be paid to the difference in the directions of the currents in each individual case.

Output Characteristics of Solar-Power-Driven Thermionic Energy Converter

2004 ◽  
Vol 43 (1) ◽  
pp. 309-314 ◽  
Author(s):  
Akihisa Ogino ◽  
Toshiya Muramatsu ◽  
Masashi Kando
Keyword(s):  
Solar Power ◽  
Energy Converter ◽  
Output Characteristics ◽  
Thermionic Energy

scholarly journals A vanadium-based oxide-phosphate-pyrophosphate framework as a 4 V electrode material for K-ion batteries

2021 ◽  
Author(s):  
Mirai Ohara ◽  
A. Shahul Hameed ◽  
Kei Kubota ◽  
Akihiro Katogi ◽  
Kuniko Chihara ◽  
...  
Keyword(s):  
Energy Storage ◽  
Electrode Material ◽  
Large Scale ◽  
Electrode Materials ◽  
Electrical Energy ◽  
Positive Electrode ◽  
Electrical Energy Storage ◽  
Positive Electrode Materials

K-ion batteries (KIBs) are promising for large-scale electrical energy storage owing to the abundant resources and the electrochemical specificity of potassium. Among the positive electrode materials for KIBs, vanadium-based polyanionic...

scholarly journals Numerical Evaluation of a HVAC System Based on a High-Performance Heat Transfer Fluid

Energies ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 3298
Author(s):  
Gianpiero Colangelo ◽  
Brenda Raho ◽  
Marco Milanese ◽  
Arturo de Risi
Keyword(s):  
Heat Transfer ◽  
High Performance ◽  
Cooling System ◽  
Electrical Energy ◽  
Simulation Software ◽  
Heat Transfer Fluid ◽  
Hvac System ◽  
Dynamic Simulations ◽  
Heating And Cooling ◽  
The University

Nanofluids have great potential to improve the heat transfer properties of liquids, as demonstrated by recent studies. This paper presents a novel idea of utilizing nanofluid. It analyzes the performance of a HVAC (Heating Ventilation Air Conditioning) system using a high-performance heat transfer fluid (water-glycol nanofluid with nanoparticles of Al2O3), in the university campus of Lecce, Italy. The work describes the dynamic model of the building and its heating and cooling system, realized through the simulation software TRNSYS 17. The use of heat transfer fluid inseminated by nanoparticles in a real HVAC system is an innovative application that is difficult to find in the scientific literature so far. This work focuses on comparing the efficiency of the system working with a traditional water-glycol mixture with the same system that uses Al2O3-nanofluid. The results obtained by means of the dynamic simulations have confirmed what theoretically assumed, indicating the working conditions of the HVAC system that lead to lower operating costs and higher COP and EER, guaranteeing the optimal conditions of thermo-hygrometric comfort inside the building. Finally, the results showed that the use of a nanofluid based on water-glycol mixture and alumina increases the efficiency about 10% and at the same time reduces the electrical energy consumption of the HVAC system.

scholarly journals Impact of Process Parameters on the Diameter of Nanobubbles Generated by Electrolysis on Platinum-Coated Titanium Electrodes Using Box–Behnken Experimental Design

Energies ◽  
2021 ◽  
Vol 14 (9) ◽  
pp. 2542
Author(s):  
Karol Ulatowski ◽  
Radosław Jeżak ◽  
Paweł Sobieszuk
Keyword(s):  
Experimental Design ◽  
Process Parameters ◽  
Current Density ◽  
Salt Concentration ◽  
Multivariate Regression ◽  
Electrical Energy ◽  
Multiphase System ◽  
Anova Analysis ◽  
Dependent Variables ◽  
Parameter Function

(1) The generation of nanobubbles by electrolysis is an interesting method of using electrical energy to form bubble nuclei, effectively creating a multiphase system. For every process, the effectiveness of nanobubble generation by electrolysis depends on various process parameters that impact should be determined. (2) In this work, the electrolytic generation of hydrogen and oxygen bubbles was performed in a self-built setup, in which a Nafion membrane separated two chambers. The generation of bubbles of both gases was investigated using Box–Behnken experimental design. Three independent variables were salt concentration, current density, and electrolysis time, while the dependent variables were Sauter diameters of generated bubbles. An ANOVA analysis and multivariate regression were carried out to propose a statistical and power model of nanobubble size as a process parameter function. (3) The generation of bubbles of hydrogen and oxygen by electrolysis showed that different factors or their combinations determine their size. The results presented in this work proved to be complementary to previous works reported in the literature. (4) The Sauter diameter of bubbles increases with salt concentration and stays constant with increasing current density in investigated range. The proposed correlations allow the Sauter diameters of nanobubbles generated during electrolysis to be predicted.

scholarly journals Heat Transfer in Rotating Serpentine Passages With Trips Normal to the Flow

1992 ◽  
Vol 114 (4) ◽  
pp. 847-857 ◽  
Author(s):  
J. H. Wagner ◽  
B. V. Johnson ◽  
R. A. Graziani ◽  
F. C. Yeh
Keyword(s):  
Heat Transfer ◽  
Turbine Blade ◽  
Large Scale ◽  
Flow Direction ◽  
Operating Conditions ◽  
Transfer Model ◽  
Transfer Coefficients ◽  
Flow Equations ◽  
Turbine Blade Cooling ◽  
Heat Transfer Coefficients

Experiments were conducted to determine the effects of buoyancy and Coriolis forces on heat transfer in turbine blade internal coolant passages. The experiments were conducted with a large-scale, multipass, heat transfer model with both radially inward and outward flow. Trip strips on the leading and trailing surfaces of the radial coolant passages were used to produce the rough walls. An analysis of the governing flow equations showed that four parameters influence the heat transfer in rotating passages: coolant-to-wall temperature ratio, Rossby number, Reynolds number, and radius-to-passage hydraulic diameter ratio. The first three of these four parameters were varied over ranges that are typical of advanced gas turbine engine operating conditions. Results were correlated and compared to previous results from stationary and rotating similar models with trip strips. The heat transfer coefficients on surfaces, where the heat transfer increased with rotation and buoyancy, varied by as much as a factor of four. Maximum values of the heat transfer coefficients with high rotation were only slightly above the highest levels obtained with the smooth wall model. The heat transfer coefficients on surfaces where the heat transfer decreased with rotation, varied by as much as a factor of three due to rotation and buoyancy. It was concluded that both Coriolis and buoyancy effects must be considered in turbine blade cooling designs with trip strips and that the effects of rotation were markedly different depending upon the flow direction.

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