Magnetic induction heating of superparamagnetic nanoparticles for applications in the energy industry
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A novel method of delivering thermal energy efficiently for flow assurance and for improved heavy oil production/transport is described. The method, an improved form of magnetic induction heating, uses superparamagnetic nanoparticles that generate heat locally when exposed to a high frequency magnetic field oscillation, via a process known as Neel relaxation. This concept is currently used in biomedicine to locally heat and ablate cancerous tissues. Dependence of the rate of heat generation by commercially available, single-domain Fe3O4 nanoparticles of ~10 nm size, on the magnetic field strength and frequency was quantified. Experiments were conducted for nanoparticles dispersed in water, in hydrocarbon liquid, and embedded in a thin, solid film dubbed “nanopaint”. For a stationary fluid heat generation increases linearly with loading of nanoparticles. The rate of heat transfer from the nanopaint to a flowing fluid was up to three times greater than the heat transfer rate to a static fluid. Dispersion models indicated that the thermal conductivity of the dispersing fluid did not greatly influence the heat transfer results, whereas differences in size between hydrophilic and hydrophobic nanoparticles did. The model of static fluid in a nanopainted tube verified that the nanoparticle loading in the paint was ~30wt% and the nanopaint thickness was 600 µm. The model of flowing fluid in a nanopainted tube showed that internal mixing in the system, even at laminar flow rates, improved heat transfer to the center of the flowing fluid. A waveguide model verified the feasibility of using steel hydrocarbon transport pipelines as a means to guide electromagnetic energy to target heating locations along the pipeline if the energy is transmitted at frequencies above the cutoff frequency. Heating of nanopaint with external magnetic field application has immediate potential impact on oil and gas sector, because such coating could be applied to inner surfaces of pipelines and production facilities. A nanoparticle dispersion could also be injected into the reservoir zone or gravel pack near the production well, so that a thin, adsorbed layer of nanoparticles is created on pore walls. With localized inductive heating of those surfaces, hydrate formation or wax deposition could be prevented; and heavy oil production/transport could be improved by creating a ‘slippage layer’ on rock pore walls and inner surfaces of transport pipes.