Oil Convection Research Articles

Highly Sensitive and Stable In Situ Acetylene Detection in Transformer Oil Using Polyimide-Embedded Carbon Nanotubes.

This study presents an acetylene gas sensor capable of in situ monitoring transformer oils. This sensor utilizes carbon nanotubes (CNTs) embedded in polyimide (PI) synthesized by floating catalyst chemical vapor deposition. Unlike conventional sensors that target hydrocarbon gases dissolved in oil and measure the gas extracted from the oil, the proposed CNT-PI sensor detects gas within the oil in real time. The PI embedding technique effectively anchors and shields the CNT network against fluidic damage, ensuring stable sensing performance over 6 months, even under friction stress caused by oil convection. Decorating CNTs with gold nanoparticles further enhances the sensitivity and response of the sensor. The sensor achieves a high response (10.5% at 30ppm) and fast response/recovery times (28 s/77 s), Furthermore, the sensor demonstrates good response (10.4% at 30ppm) and moderate response/recovery times (444 s/670 s) in an oil medium, which qualifies for industrial applications. Additionally, a CNT-PI-based heater is integrated into the sensor as a multilayer component, maintaining an optimal operating temperature of 90 °C. The CNT-PI sensor demonstrates consistent gas-sensing performance even after 10,000 bending cycles and exhibits superior characteristics, indicating its compatibility with various forms of transformers.

CO2 dissolution and convection in oil at realistic reservoir conditions: A visualization study

CO2 convective mixing has been extensively studied for CO2 dissolution in saline water but very limited with the presence of oil. The objective of this work was to visually study the supercritical CO2 (sCO2) dissolution and convective mixing into oil at realistic reservoir temperature and pressure conditions with and without the presence of porous media.A specially designed high-pressure 2D-cell was used to investigate the sCO2 mixing into oil phases. Schlieren imaging method was used as the visualization method. The experiments were carried out at 100 bar and 50 °C using n-octane, n-decane, and crude oil as the main oils. Porous media with different permeability was prepared using glass beads.Convective fingering was found to accelerate the mixing of CO2 with n-octane and n-decane. It was not possible to visualize the CO2 convective fingering in crude oil due to the low opacity of the oil phase. The CO2 dissolution into oil phases was quite instantaneous and fast without the presence of porous media. The swelling of oil was measured as 55%, 50% and 11% for n-decane, n-octane and crude oil respectively without the presence of porous media. Boundary effects were affecting the CO2 mixing due to the circular shape of the 2D-cell. Having a water layer below the oil layer tends to dampen the CO2 transport from the oil phase to the water phase. CO2 dissolution into oil saturated porous media was slower compared to that without the presence of porous media. The mixing of CO2 was faster at higher permeability than at lower permeability. Visualization of CO2 convective mixing/fingers inside oil-saturated porous media using a Hele-Shaw cell yet to be achieved experimentally.

Thermal validation of a simple moving boundary model to determine the frying time of a thin potato crisp

A simple moving boundary model was redesigned to describe the immersion frying of a thin cut potato crisp of thickness 2 mm. The model took into account the effects of a variable oil convection heat transfer coefficient. In the model, the centre temperature was defined as a value of a region rather than a point. The model also predicted the effect of some shift in the location of the thermocouple on the measurements. Experiments at oil temperatures of 170, 180 and 190 °C were conducted to verify whether or not the model predictions were accurate. Good agreement was found between the experimental and predicted values, which were generally within the t99(0.01) confidence interval of the experimental data.

Conditions for the Static Equilibrium and Circulation of Insulating Liquids in Electric Fields

A demonstration of electrically induced convection in oil, depending on dielectric loss and permittivity relation, supports theoretical arguments that place limits on the possibility of static equilibrium in steady or alternating electric fields.

Free Convective Heat Transfer in Viscous Oil

The heat transfer by free convection in viscous oil is practically important for the design on the tank heaters of an oil tanker etc. The free convective phenomenon in oil is different from that in other fluids with constant properties, since oil has viscosity which depends sensively on temperature. However, few studies have been given to these kinds of problem. This paper deals with the theoretical analysis of the free convection in oil. The numerical solutions of the basic equations are given to a horizontal tube and a vertical plate in wide range of Prandtl numbers and wall temperature on a digital computer. And the effect of variable viscosity is discussed. Finally, the formulas for Nusselt number are presented for the case of the heat transfer in oil.