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Electric Conduction in Mineral Oil based ZnONanofluids under Intense Electric Fields
KTH, Skolan för elektroteknik och datavetenskap (EECS).ORCID-id: 0000-0002-8173-8765
KTH, Skolan för elektroteknik och datavetenskap (EECS), Elektroteknisk teori och konstruktion.ORCID-id: 0000-0002-6375-6142
Department of Chemistry and Chemical Engineering, Chalmers University of Technology, SE-412 96 Gothenburg, Sweden.ORCID-id: 0000-0001-5867-0531
(Engelska)Manuskript (preprint) (Övrigt vetenskapligt)
Abstract [en]

The electric conduction processes in mineral oil based ZnO–C18 nanofluids under intense electric fields are investigated. For this, conduction currents are measured usinga needle-plane electrode configuration. Furthermore, an electrohydrodynamic (EHD) model is used here to discuss the charge generation mechanisms and the electronic properties of the ZnO–C18 nanofluids. The analysis of the conduction currents shows that ZnO–C18 nanoparticles increase the generation of charge carriers, and at the same time they augment the scavenging of quasi-free electrons compared with the measurements with mineral oil only. It is found that the existing nanoparticle electron scavenging model reported in the literature grossly underestimates the electron scavenging process here reported. A new analytical formulation for the nanoparticle electron scavenging process is proposed. The EHD model is also used to simulate the electric conduction processes just before negative streamer inception in mineral oil and ZnO–C18 nanofluids. It is shown that ZnO–C18 nanoparticles hinder the streamer initiation process by reducing the effective electric field at the tip of the needle. This electric field reduction is caused by the combined effect of the generation of charge carriers and the electron scavenging of ZnO–C18 nanoparticles.

Nationell ämneskategori
Elektroteknik och elektronik Nanoteknik
Forskningsämne
Elektro- och systemteknik
Identifikatorer
URN: urn:nbn:se:kth:diva-255604OAI: oai:DiVA.org:kth-255604DiVA, id: diva2:1340015
Anmärkning

QC 20190802

Tillgänglig från: 2019-08-01 Skapad: 2019-08-01 Senast uppdaterad: 2019-08-02Bibliografiskt granskad
Ingår i avhandling
1. Pre-breakdown Phenomena in Mineral Oil Based Nanofluids
Öppna denna publikation i ny flik eller fönster >>Pre-breakdown Phenomena in Mineral Oil Based Nanofluids
2019 (Engelska)Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
Abstract [en]

Mineral oil is a dielectric liquid commonly used in high voltage equipment such as power transformers. Interestingly, it has been experimentally observed that the dielectric strength of the mineral oil is improved when nanoparticles are added. However, the mechanisms behind these improvements are not well understood, hindering the further innovation process of these so-called nanofluids. This thesis aims to contribute to the understanding of the mechanisms explaining the dielectric strength improvement of the base oil when nanoparticles are added.For this, several experiments and numerical simulations are performed in this thesis. The initiation voltage of electric discharges infive different kind of nanofluids was measured. The large data set obtained allowed to cast experimental evidence on the existing hypotheses that are used to explain the effect of nanoparticles. It is found that hydrophilic nanoparticles hinder the electric discharge initiation from anode electrodes. On the other hand, electric discharge initiation from cathode electrodes was hindered by nanoparticles with low charge relaxation time.The electric currents in mineral oil and nanofluids were also measured under intense electric fields (up to 2GV/m). It is found that the addition of certain nanoparticles increases the measured currents. The possible physical mechanisms explaining the measured currents inmineral oil with and without nanoparticles were thoroughly discussed based on results of numerical simulations. Preliminary parameters used in this thesis to model these mechanisms led to a good agreement between the measured and simulated electric currents.

Ort, förlag, år, upplaga, sidor
Stockholm: KTH Royal Institute of Technology, 2019. s. 69
Serie
TRITA-EECS-AVL ; 2019:58
Nationell ämneskategori
Elektroteknik och elektronik
Forskningsämne
Elektro- och systemteknik
Identifikatorer
urn:nbn:se:kth:diva-255605 (URN)978-91-7873-241-8 (ISBN)
Disputation
2019-09-06, Kollegiesalen, Brinellvägen 8, Stockholm, 10:00 (Engelska)
Opponent
Handledare
Anmärkning

QC 20190802

Tillgänglig från: 2019-08-02 Skapad: 2019-08-01 Senast uppdaterad: 2019-08-02Bibliografiskt granskad

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Aljure, MauricioBecerra Garcia, MarleyPourrahimi, Amir Masoud

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Aljure, MauricioBecerra Garcia, MarleyPourrahimi, Amir Masoud
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Skolan för elektroteknik och datavetenskap (EECS)Elektroteknisk teori och konstruktion
Elektroteknik och elektronikNanoteknik

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