The solidification process in a multi-tube latent heat energy system is affected by the natural convection and the arrangement of heat exchanger tubes, which changes the buoyancy effect as well. In the current work, the effect of the arrangement of the tubes in a multi-tube heat exchanger was examined during the solidification process with the focus on the natural convection effects inside the phase change material (PCM). The behavior of the system was numerically analyzed using liquid fraction and energy released, as well as temperature, velocity and streamline profiles for different studied cases. The arrangement of the tubes, considering seven pipes in the symmetrical condition, are assumed at different positions in the system, including uniform distribution of the tubes as well as non-uniform distribution, i.e., tubes concentrated at the bottom, middle and the top of the PCM shell. The model was first validated compared with previous experimental work from the literature. The results show that the heat rate removal from the PCM after 16 h was 52.89 W (max) and 14.85 W (min) for the cases of uniform tube distribution and tubes concentrated at the bottom, respectively, for the proposed dimensions of the heat exchanger. The heat rate removal of the system with uniform tube distribution increases when the distance between the tubes and top of the shell reduces, and increased equal to 68.75 W due to natural convection effect. The heat release rate also reduces by increasing the temperature the tubes. The heat removal rate increases by 7.5%, and 23.7% when the temperature increases from 10 °C to 15 °C and 20 °C, respectively. This paper reveals that specific consideration to the arrangement of the tubes should be made to enhance the heat recovery process attending natural convection effects in phase change heat storage systems.

This study aims to study the discharging process to verify the influence of geometry modifications and heat transfer flow (HTF) patterns on the performance of a vertical triplex-tube latent heat container. The phase change material (PCM) is included in the middle tube, where the geometry is modified using single or multi-internal frustum tubes instead of straight tubes to enhance the discharging rate. The effects of the HTF flow direction, which is considered by the gravity and opposite-gravity directions, are also examined in four different cases. For the optimal geometry, three scenarios are proposed, i.e., employing a frustum tube for the middle tube, for the inner tube, and at last for both the inner and middle tubes. The effects of various gap widths in the modified geometries are investigated. The results show the advantages of using frustum tubes in increasing the discharging rate and reducing the solidification time compared with that of the straight tube unit due to the higher natural convection effect by proper utilization of frustum tubes. The study of the HTF pattern shows that where the HTF direction in both the inner and outer tubes are in the gravity direction, the maximum discharging rate can be achieved. For the best configuration, the discharge time is reduced negligibly compared with that for the system with straight tubes which depends on the dimensions of the PCM domain.

Corrosion costs the Oil & Gas Industry billions of pounds annually, primarily due to environmental factors such as high salinity, temperature fluctuations, and humidity in marine environments. Mobile Offshore Drilling Units (MODUs), especially jack-up rigs, are particularly susceptible to these dangers. This paper examines the impact of cold stacking on aging jack-up rigs and highlights how the absence of an adequate corrosion control system can accelerate structural deterioration. Our findings show that repair costs following cold stacking can far exceed the costs associated with maintaining rigs in a warm-stacked state. Preload tanks are critical areas prone to degradation due to microbiologically influenced corrosion (MIC) and inadequate preservation practices. Furthermore, although high-strength steels are frequently utilized in the construction of jack-up rigs due to their durability, we illustrate that, in the absence of meticulously devised preventative measures, these steels are susceptible to considerable corrosion, resulting in substantial repair expenses and diminished operational lifespans. This study highlights the significance of proactive corrosion control measures in maintaining the long-term structural integrity and cost-effectiveness of offshore drilling units.

Drilling operations generate large volumes of drill cuttings contaminated with hydrocarbons, salts, and trace metals, creating significant environmental and regulatory challenges for offshore disposal. Most regulatory frameworks prohibit the discharge of drill cuttings containing more than 1 wt.% oil-on-cuttings, necessitating effective on-site treatment technologies. This study evaluates a novel continuous hybrid microwave–infrared thermal desorption process, the Advanced Thermal Processor (ATP), which, unlike conventional batch thermal desorption systems, simultaneously applies microwave volumetric heating and infrared surface heating within a rotating drum under continuous feed operation. Six samples of offshore water-based drill cuttings contaminated with sour crude oil were collected from Middle Eastern drilling operations and processed in two batches using a pilot-scale ATP unit under inert, low-oxygen conditions. The treatment was carried out at a solid discharge temperature of 60–100 °C and a residence time of approximately 15–30 min. The process achieved oil removal efficiencies of 95.0–97.8%, consistently reducing oil-on-cuttings to below 1 wt.%. Total Petroleum Hydrocarbons (TPH) and Total Oil and Grease (TOG) were reduced by more than 96% across all samples. Thermogravimetric analysis confirmed that most volatile contaminants were removed at temperatures below 110 °C, suggesting a substantially lower thermal demand than conventional incineration or friction-based thermal desorption, which typically operate above 300–500 °C. The results demonstrate that hybrid microwave/infrared thermal processing is an effective and energy-efficient approach for the treatment of offshore drill cuttings, enabling regulatory compliance while minimising secondary emissions and operational disruption.