Pub Date : 2019-06-01DOI: 10.1109/ICDL.2019.8796686
K. Yasuoka, Yuta Yamada, Mo Chen, R. Nakayama, S. Kubo, S. Zen
Hybrid DC switches have been intensively studied because of the increasing demand for DC power distribution systems. A hybrid switch consists of high-speed mechanical contacts, semiconductor power devices, and metal– oxide varistor elements. Make arcs are suppressed from occurring by turning on the power device connected in parallel before closing the contacts. In the opening period, the contact voltage increases and microsecond make arcs occur intermittently during the rise of contact voltage exceed the boiling voltage of the contact material. The arc voltage turns on the power device and subsequently the circuit current commutates from the contacts to the power device. The DC current is interrupted by the power device with varistors. Although the duration of make arcs was a few 10 m s, the contact surface was degraded and the insulation strength decreased up to 20% in 1 kA DC commutation.
由于直流配电系统的需求日益增长，混合直流开关得到了广泛的研究。混合开关由高速机械触点、半导体功率器件和金属氧化物压敏电阻元件组成。在闭合触点之前，通过打开并联的电源装置来抑制电弧的发生。在开启阶段，触点电压升高，微秒使触点电压上升超过触点材料的沸腾电压时产生间歇性电弧。电弧电压导通电源器件，随后电路电流从触点向电源器件换向。直流电流由带有压敏电阻的电源装置中断。虽然电弧持续时间仅为10 m s，但在1 kA直流换流中，接触面退化，绝缘强度下降高达20%。
{"title":"Commutation of Current in a Hybrid DC Switch","authors":"K. Yasuoka, Yuta Yamada, Mo Chen, R. Nakayama, S. Kubo, S. Zen","doi":"10.1109/ICDL.2019.8796686","DOIUrl":"https://doi.org/10.1109/ICDL.2019.8796686","url":null,"abstract":"Hybrid DC switches have been intensively studied because of the increasing demand for DC power distribution systems. A hybrid switch consists of high-speed mechanical contacts, semiconductor power devices, and metal– oxide varistor elements. Make arcs are suppressed from occurring by turning on the power device connected in parallel before closing the contacts. In the opening period, the contact voltage increases and microsecond make arcs occur intermittently during the rise of contact voltage exceed the boiling voltage of the contact material. The arc voltage turns on the power device and subsequently the circuit current commutates from the contacts to the power device. The DC current is interrupted by the power device with varistors. Although the duration of make arcs was a few 10 m s, the contact surface was degraded and the insulation strength decreased up to 20% in 1 kA DC commutation.","PeriodicalId":102217,"journal":{"name":"2019 IEEE 20th International Conference on Dielectric Liquids (ICDL)","volume":"166 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"120851330","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-06-01DOI: 10.1109/ICDL.2019.8796724
D. Koulova, P. Traoré, H. Romat
In this article we analyse the results of a numerical simulation of an electro-thermo-convective flow induced in a dielectric liquid layer by the simultaneous action of an external electric field and a thermal gradient. A low conductivity liquid is placed between two horizontal electrodes and subjected to strong unipolar charge injection which set the fluid in motion under the combined action of Coulomb and buoyancy forces. The motion induced by the charge injection has a vigorous character and strongly increases the electric charge transfer and heat transfer between the electrodes. The full set of governing equations including Navier-Stokes equation, the conservation equations of electric charge and energy and Poisson equation for electric potential is solved by a finite volume method. We define an electric Nusselt number (Ne) as the ratio of the effective current and the current existing without liquid motion, number which can be considered as the analog of Nusselt number (Nu) for a pure thermal problem. The case of heating and strong injection of electric charges from lower electrode is considered. The variation of the electric Nusselt number Ne with electrical parameter T for different values of the non-dimensional parameter mobility number M and Rayleigh number is then analyzed. It is shown that the mobility number M is a parameter which plays an important role in the characterization of electro-thermo-convective flows and also that the physical mechanisms of the different instability regimes can be better understood considering the electric Nusselt number Ne.
{"title":"Effect of Electric Nusselt Number on Electro-Thermo-Convection in Dielectric Liquid Subjected to Unipolar Injection","authors":"D. Koulova, P. Traoré, H. Romat","doi":"10.1109/ICDL.2019.8796724","DOIUrl":"https://doi.org/10.1109/ICDL.2019.8796724","url":null,"abstract":"In this article we analyse the results of a numerical simulation of an electro-thermo-convective flow induced in a dielectric liquid layer by the simultaneous action of an external electric field and a thermal gradient. A low conductivity liquid is placed between two horizontal electrodes and subjected to strong unipolar charge injection which set the fluid in motion under the combined action of Coulomb and buoyancy forces. The motion induced by the charge injection has a vigorous character and strongly increases the electric charge transfer and heat transfer between the electrodes. The full set of governing equations including Navier-Stokes equation, the conservation equations of electric charge and energy and Poisson equation for electric potential is solved by a finite volume method. We define an electric Nusselt number (Ne) as the ratio of the effective current and the current existing without liquid motion, number which can be considered as the analog of Nusselt number (Nu) for a pure thermal problem. The case of heating and strong injection of electric charges from lower electrode is considered. The variation of the electric Nusselt number Ne with electrical parameter T for different values of the non-dimensional parameter mobility number M and Rayleigh number is then analyzed. It is shown that the mobility number M is a parameter which plays an important role in the characterization of electro-thermo-convective flows and also that the physical mechanisms of the different instability regimes can be better understood considering the electric Nusselt number Ne.","PeriodicalId":102217,"journal":{"name":"2019 IEEE 20th International Conference on Dielectric Liquids (ICDL)","volume":"47 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123836705","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-06-01DOI: 10.1109/ICDL.2019.8796663
C. Dotterweich, Fabian Dax, M. Zink, John Popp, T. Staab, G. Sextl, F. Berger
A comprehensive theory of the conduction processes in dielectric liquids is needed to describe their behavior from low to high field strengths. To investigate the conductivity of dielectric liquids a paraffin with low self-conductivity and well-defined chemical structure is used. Particularly at higher field strengths the material and surface of the electrodes has to be considered as well. It is shown, that ground and polished electrodes of stainless steel reveal different behavior during current measurements. Furthermore, particularly at high field strengths long-time measurements are needed to reach steady state conditions. The current measurement employing polished electrodes shows great scattering. Due to the polishing process several surface irregularities became apparent. Hence, for current measurements the electrode material and surface treatment of the electrodes are of great importance.
{"title":"Influence of the Electrode Surface Roughness on the Electrical Conductivity of Pure Paraffin","authors":"C. Dotterweich, Fabian Dax, M. Zink, John Popp, T. Staab, G. Sextl, F. Berger","doi":"10.1109/ICDL.2019.8796663","DOIUrl":"https://doi.org/10.1109/ICDL.2019.8796663","url":null,"abstract":"A comprehensive theory of the conduction processes in dielectric liquids is needed to describe their behavior from low to high field strengths. To investigate the conductivity of dielectric liquids a paraffin with low self-conductivity and well-defined chemical structure is used. Particularly at higher field strengths the material and surface of the electrodes has to be considered as well. It is shown, that ground and polished electrodes of stainless steel reveal different behavior during current measurements. Furthermore, particularly at high field strengths long-time measurements are needed to reach steady state conditions. The current measurement employing polished electrodes shows great scattering. Due to the polishing process several surface irregularities became apparent. Hence, for current measurements the electrode material and surface treatment of the electrodes are of great importance.","PeriodicalId":102217,"journal":{"name":"2019 IEEE 20th International Conference on Dielectric Liquids (ICDL)","volume":"59 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116630564","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-06-01DOI: 10.1109/ICDL.2019.8796570
D. Linhjell, L. Lundgaard, M. Unge
The propagation of positive streamers in a naphtenic transformer oil in an 80 mm point-plane gap has been investigated under an impulse voltage being close to a step voltage and under pressures ranging from 0.1 to 1.7 MPa. As has previously been found in short gap experiments of 1 – 7 mm in various liquids, increasing voltage leads to shorter stopping length of non-breakdown streamers and higher breakdown voltages while the velocity is close to independent of pressure. The “acceleration” voltage from which streamer velocity rapidly increase with increasing voltage is also close to pressure independent. It is argued that this indicates that the processes determining velocity must take place in the liquid phase at the streamer head while conditions in the channel determines the stopping length of non-breakdown streamers.
{"title":"Pressure Dependent Propagation of Positive Streamers in a long Point-Plane Gap in Transformer Oil","authors":"D. Linhjell, L. Lundgaard, M. Unge","doi":"10.1109/ICDL.2019.8796570","DOIUrl":"https://doi.org/10.1109/ICDL.2019.8796570","url":null,"abstract":"The propagation of positive streamers in a naphtenic transformer oil in an 80 mm point-plane gap has been investigated under an impulse voltage being close to a step voltage and under pressures ranging from 0.1 to 1.7 MPa. As has previously been found in short gap experiments of 1 – 7 mm in various liquids, increasing voltage leads to shorter stopping length of non-breakdown streamers and higher breakdown voltages while the velocity is close to independent of pressure. The “acceleration” voltage from which streamer velocity rapidly increase with increasing voltage is also close to pressure independent. It is argued that this indicates that the processes determining velocity must take place in the liquid phase at the streamer head while conditions in the channel determines the stopping length of non-breakdown streamers.","PeriodicalId":102217,"journal":{"name":"2019 IEEE 20th International Conference on Dielectric Liquids (ICDL)","volume":"83 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115426855","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-06-01DOI: 10.1109/ICDL.2019.8796536
Yuan Wang, Xiaojing Zhang, Haichuan Yu, Xin Li, Yang Xu
With the development of high temperature insulation system, natural ester transformers grow rapidly at present. The international standard for the compatibility of transformer construction materials with natural ester are necessary by industry. ANBT NBR 16341, standards in Brazil, identified compatibility of natural ester transformers. However, thermal ageing temperature, 100°C, is too low to identified high temperature insulation system, such as aramid enhanced cellulose with natural ester. In this paper, a series of construction material used in natural ester transformers have been tested, including nitrile rubber, acrylic ester, inner surface varnish, varnish of silicon steel sheet and varnished wire. The natural ester adopted in this paper was FR3. The properties of FR3, rubber and vanished wire were tested before and after 164 hours, 336 hours thermal aging under 130°C. The experimental results indicate that the dielectric strength, dielectric dissipation factor, viscosity and acid value of natural ester, the mass and hardness of rubber are the necessary parameters for evaluating the compatibility of construction materials with natural ester. Meanwhile it is observed that the parameters benchmark of FR3 in ANBT NBR 16341 needed to be justified for overloading transformer. According to the initial test data in this paper, there is big concern for compatibility of the Nitrile rubber and varnished wire with FR3, while acrylic ester, inner surface varnish of transformer and varnish of silicon steel sheet are well compatible with FR3 natural ester. The results in this paper can provide some reference to the revision of the standard for the compatibility of transformer construction materials with natural ester.
{"title":"Investigation on the Compatibility of Transformer Construction Materials with Natural Ester","authors":"Yuan Wang, Xiaojing Zhang, Haichuan Yu, Xin Li, Yang Xu","doi":"10.1109/ICDL.2019.8796536","DOIUrl":"https://doi.org/10.1109/ICDL.2019.8796536","url":null,"abstract":"With the development of high temperature insulation system, natural ester transformers grow rapidly at present. The international standard for the compatibility of transformer construction materials with natural ester are necessary by industry. ANBT NBR 16341, standards in Brazil, identified compatibility of natural ester transformers. However, thermal ageing temperature, 100°C, is too low to identified high temperature insulation system, such as aramid enhanced cellulose with natural ester. In this paper, a series of construction material used in natural ester transformers have been tested, including nitrile rubber, acrylic ester, inner surface varnish, varnish of silicon steel sheet and varnished wire. The natural ester adopted in this paper was FR3. The properties of FR3, rubber and vanished wire were tested before and after 164 hours, 336 hours thermal aging under 130°C. The experimental results indicate that the dielectric strength, dielectric dissipation factor, viscosity and acid value of natural ester, the mass and hardness of rubber are the necessary parameters for evaluating the compatibility of construction materials with natural ester. Meanwhile it is observed that the parameters benchmark of FR3 in ANBT NBR 16341 needed to be justified for overloading transformer. According to the initial test data in this paper, there is big concern for compatibility of the Nitrile rubber and varnished wire with FR3, while acrylic ester, inner surface varnish of transformer and varnish of silicon steel sheet are well compatible with FR3 natural ester. The results in this paper can provide some reference to the revision of the standard for the compatibility of transformer construction materials with natural ester.","PeriodicalId":102217,"journal":{"name":"2019 IEEE 20th International Conference on Dielectric Liquids (ICDL)","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129729748","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-06-01DOI: 10.1109/ICDL.2019.8796667
D. Testi
The paper shows the elaboration of a photometric technique with the purpose of obtaining thickness maps of liquid films, subject to corona wind. Light absorption occurring through a liquid layer with the addition of dyestuff is used to evaluate its thickness. The layer is illuminated from the back of the wetted wall and the transiting light intensity is measured by means of a digital camera. Non-uniformities in the original intensity field suggest building a calibration curve for each measurement point. The filtering and interpolation procedure necessary to transform the measured light intensity into the thickness field is described in detail. The technique is economical and non-intrusive. It can determine the local film thickness with an accuracy below 10 % of the measuring range. Application to obtaining a liquid thickness map for falling films under ionic wind in different regimes and at different waviness is illustrated. It is particularly interesting to study this phenomenon, since an ionic wind, with electrical currents lower than 1 mA, can create additional waves and ripples on the liquid/gas interface, thus, in practical applications, it increases mass and heat transfer between the two phases with a negligible energy expense. The thickness of the falling film is measured with and without the generation of corona wind by a thin wire. The pattern of surface ripples can be observed over the entire illuminated area and the beneficial effect on surface waviness can be evaluated at both polarities of the applied high voltage.
{"title":"Mapping the Thickness of Falling Liquid Films under Ionic Wind by a Light Absorption Technique","authors":"D. Testi","doi":"10.1109/ICDL.2019.8796667","DOIUrl":"https://doi.org/10.1109/ICDL.2019.8796667","url":null,"abstract":"The paper shows the elaboration of a photometric technique with the purpose of obtaining thickness maps of liquid films, subject to corona wind. Light absorption occurring through a liquid layer with the addition of dyestuff is used to evaluate its thickness. The layer is illuminated from the back of the wetted wall and the transiting light intensity is measured by means of a digital camera. Non-uniformities in the original intensity field suggest building a calibration curve for each measurement point. The filtering and interpolation procedure necessary to transform the measured light intensity into the thickness field is described in detail. The technique is economical and non-intrusive. It can determine the local film thickness with an accuracy below 10 % of the measuring range. Application to obtaining a liquid thickness map for falling films under ionic wind in different regimes and at different waviness is illustrated. It is particularly interesting to study this phenomenon, since an ionic wind, with electrical currents lower than 1 mA, can create additional waves and ripples on the liquid/gas interface, thus, in practical applications, it increases mass and heat transfer between the two phases with a negligible energy expense. The thickness of the falling film is measured with and without the generation of corona wind by a thin wire. The pattern of surface ripples can be observed over the entire illuminated area and the beneficial effect on surface waviness can be evaluated at both polarities of the applied high voltage.","PeriodicalId":102217,"journal":{"name":"2019 IEEE 20th International Conference on Dielectric Liquids (ICDL)","volume":"10 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129128483","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-06-01DOI: 10.1109/ICDL.2019.8796812
S. Tee, D. Walker, M. Bebbington
A fire in an embedded substation triggered a policy change in SP Energy Networks (SPEN) which led to the use of synthetic ester filled transformers in 11kV distribution embedded substations. Driven by improved understanding from research and increased experience in operating synthetic ester filled transformers, the use of synthetic ester then expanded to 33kV primary and 132kV grid transformers. This paper charts the increased use of synthetic ester filled transformers in SPEN along with sharing the benefits realised from adopting synthetic ester applications. Factory acceptance test and condition monitoring data are also presented which indicated the suitability of synthetic ester filled transformers as viable alternatives to conventional mineral oil filled units.
{"title":"Experience of Synthetic Ester Filled Transformers in SP Energy Networks","authors":"S. Tee, D. Walker, M. Bebbington","doi":"10.1109/ICDL.2019.8796812","DOIUrl":"https://doi.org/10.1109/ICDL.2019.8796812","url":null,"abstract":"A fire in an embedded substation triggered a policy change in SP Energy Networks (SPEN) which led to the use of synthetic ester filled transformers in 11kV distribution embedded substations. Driven by improved understanding from research and increased experience in operating synthetic ester filled transformers, the use of synthetic ester then expanded to 33kV primary and 132kV grid transformers. This paper charts the increased use of synthetic ester filled transformers in SPEN along with sharing the benefits realised from adopting synthetic ester applications. Factory acceptance test and condition monitoring data are also presented which indicated the suitability of synthetic ester filled transformers as viable alternatives to conventional mineral oil filled units.","PeriodicalId":102217,"journal":{"name":"2019 IEEE 20th International Conference on Dielectric Liquids (ICDL)","volume":"11 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125263744","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-06-01DOI: 10.1109/ICDL.2019.8796533
Niharika Baruah, Mrutyunjay Maharana, Sujita Srichandana Dey, S. K. Nayak
Nanofluids (NFs) are being increasingly used to improve the heat transfer and dielectric capabilities of the electrical equipment and enhance their life expectancy. Preparation of a stable NF and its superior thermophysical and electrical properties is expected to lead to a much lower life-cycle cost of a power/distribution transformer. This paper intends to analyze the effect of polarization of the nanoparticles (NPs) on the improvement of relative permittivity when they are dispersed in TO. To validate the existing theories about it, experiments are carried out to determine the values of the relative permittivity of both the fresh mineral oil (MO) and vegetable oil (VO), and also the MO-NF and VO-NF. The VO used for this study is the pongamia pinnata oil. In this work, different volumetric concentrations of 0.01, 0.05 and 0.1 wt.% of exfoliated hexagonal boron nitride (Eh-BN) NP dispersed in both MO and VO are considered to understand the variation in the permittivity measurements and a comparative analysis is carried out. This study recognizes the effects of using NPs in both MO and VO and how significantly it influences the dielectric behaviour of the liquid. The results show enhanced permittivity for the NFs as compared to the base fluids. The mechanism behind the change in the relative permittivity is understood by the impact of polarization effects in the Eh-BN NPs added to the oil.
{"title":"Nanoparticle Polarization Effect on the Permittivity of the Dielectric Liquid","authors":"Niharika Baruah, Mrutyunjay Maharana, Sujita Srichandana Dey, S. K. Nayak","doi":"10.1109/ICDL.2019.8796533","DOIUrl":"https://doi.org/10.1109/ICDL.2019.8796533","url":null,"abstract":"Nanofluids (NFs) are being increasingly used to improve the heat transfer and dielectric capabilities of the electrical equipment and enhance their life expectancy. Preparation of a stable NF and its superior thermophysical and electrical properties is expected to lead to a much lower life-cycle cost of a power/distribution transformer. This paper intends to analyze the effect of polarization of the nanoparticles (NPs) on the improvement of relative permittivity when they are dispersed in TO. To validate the existing theories about it, experiments are carried out to determine the values of the relative permittivity of both the fresh mineral oil (MO) and vegetable oil (VO), and also the MO-NF and VO-NF. The VO used for this study is the pongamia pinnata oil. In this work, different volumetric concentrations of 0.01, 0.05 and 0.1 wt.% of exfoliated hexagonal boron nitride (Eh-BN) NP dispersed in both MO and VO are considered to understand the variation in the permittivity measurements and a comparative analysis is carried out. This study recognizes the effects of using NPs in both MO and VO and how significantly it influences the dielectric behaviour of the liquid. The results show enhanced permittivity for the NFs as compared to the base fluids. The mechanism behind the change in the relative permittivity is understood by the impact of polarization effects in the Eh-BN NPs added to the oil.","PeriodicalId":102217,"journal":{"name":"2019 IEEE 20th International Conference on Dielectric Liquids (ICDL)","volume":"63 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129941012","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-06-01DOI: 10.1109/ICDL.2019.8796510
D. Cocks, R. White
The possibility for solvation of an electron in a non-polar liquid by an excitation collision is considered in the context of capture into natural fluctuations. We focus on liquid methane as input data is readily available, although our method is easily extended to other species. We adapt our previous work, which found that sound mode excitations in atomic fluids could allow for trapping of electrons in weak fluctuations, to consider incoherent excitations as the trapping mechanism. These excitations present opportunities for solvation to occur at higher energies, around the threshold energies of the excitation processes. The rates we obtain for solvation in liquid methane are weak, due to the low abundance of fluctuations supporting bound states. The formalism presented here is aimed at providing an ab-initio energy-discriminant description, in contrast to an empirical time-scale, for modelling solvation of electrons in applications such as plasma exposure of water or biological bodies.
{"title":"Excitation processes as a pathway for electron solvation in non-polar liquids","authors":"D. Cocks, R. White","doi":"10.1109/ICDL.2019.8796510","DOIUrl":"https://doi.org/10.1109/ICDL.2019.8796510","url":null,"abstract":"The possibility for solvation of an electron in a non-polar liquid by an excitation collision is considered in the context of capture into natural fluctuations. We focus on liquid methane as input data is readily available, although our method is easily extended to other species. We adapt our previous work, which found that sound mode excitations in atomic fluids could allow for trapping of electrons in weak fluctuations, to consider incoherent excitations as the trapping mechanism. These excitations present opportunities for solvation to occur at higher energies, around the threshold energies of the excitation processes. The rates we obtain for solvation in liquid methane are weak, due to the low abundance of fluctuations supporting bound states. The formalism presented here is aimed at providing an ab-initio energy-discriminant description, in contrast to an empirical time-scale, for modelling solvation of electrons in applications such as plasma exposure of water or biological bodies.","PeriodicalId":102217,"journal":{"name":"2019 IEEE 20th International Conference on Dielectric Liquids (ICDL)","volume":"51 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130019898","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-06-01DOI: 10.1109/ICDL.2019.8796518
D. Testi
In this paper, an experimental campaign is illustrated, showing the heat transfer enhancing effect of an ionic jet that impinges on the upper surface of a heated plate. Ion injection is obtained by a sharp high-voltage electrode. The employed liquid is the space-qualified coolant H-Galden ZT S5. Several tests are conducted, with different compositions, shapes and polarities of the electrode, changing the high voltage, the electrode-to-plane distance, and the applied heat flow. The electrohydrodynamic technique produces heat transfer augmentation up to 230 % with respect to thermogravitational convection and heat transfer coefficients in the order of one kW/(m2.K). The electrohydrodynamic enhancing effect is obtained with very low power input. The ionic flow has remained active for 750 hours of continuous monitored operation. H-Galden ZT S5 performs better than other dielectric liquids, such as FC-72, HFE-7100, and Vertrel XF tested in previous campaigns reported in literature, dedicated to improving heat transfer by the application of electric fields.
{"title":"Heat Transfer Enhancement in a Dielectric Coolant by Electroconvection in Point-Plane Geometry","authors":"D. Testi","doi":"10.1109/ICDL.2019.8796518","DOIUrl":"https://doi.org/10.1109/ICDL.2019.8796518","url":null,"abstract":"In this paper, an experimental campaign is illustrated, showing the heat transfer enhancing effect of an ionic jet that impinges on the upper surface of a heated plate. Ion injection is obtained by a sharp high-voltage electrode. The employed liquid is the space-qualified coolant H-Galden ZT S5. Several tests are conducted, with different compositions, shapes and polarities of the electrode, changing the high voltage, the electrode-to-plane distance, and the applied heat flow. The electrohydrodynamic technique produces heat transfer augmentation up to 230 % with respect to thermogravitational convection and heat transfer coefficients in the order of one kW/(m2.K). The electrohydrodynamic enhancing effect is obtained with very low power input. The ionic flow has remained active for 750 hours of continuous monitored operation. H-Galden ZT S5 performs better than other dielectric liquids, such as FC-72, HFE-7100, and Vertrel XF tested in previous campaigns reported in literature, dedicated to improving heat transfer by the application of electric fields.","PeriodicalId":102217,"journal":{"name":"2019 IEEE 20th International Conference on Dielectric Liquids (ICDL)","volume":"25 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127928836","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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