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The convective instability driven by buoyancy and heat transfer characteristics of nanofluids are investigated analytically. This paper proposes a factor which describes the effect of nanoparticle addition on the convective instability and heat transfer characteristics of a base fluid. The Bruggeman model based on the mean field approach for expressing the thermal conductivity enhancement is chosen as a lower bound of the thermal conductivity relationship. The results show that as the density and heat capacity of nanoparticles increase and the thermal conductivity and the shape factor of nanoparticles decrease, the convective motion in a nanofluid sets in easily. The heat transfer coefficient of a nanofluid is enhanced by all parameters with respect to the volume fraction of nanoparticles.

With gel treatment, application of low salinity waterflood recovers significant amount oil from mixed- or oil-wet and severely heterogeneous reservoirs due to wettability alteration. In order to assess the performance of hybrid gel treatment with low salinity waterflood, numerical simulations has been performed for various injection schemes including low salinity polymer flood and hybrid gel treatment with low salinity waterflood. While injectivity in polymer process is significantly reduced by injection of low salinity water, that of gel treatment process is not highly influenced. In addition, optimization algorithm maximizing net present value (NPV) is applied to injection scheme under consideration of injectivity to clarify the assessment of potential of hybrid gel treatment with low salinity waterflood comparing with low salinity polymer flood. Restricted constraint condition of injection makes hybrid gel treatment with low salinity waterflood to become efficient recovery method with respect to not on...

This study evaluates the viability of n-octanol as an alternative fuel in a direct-injection diesel engine, aiming to enhance sustainability and efficiency. Experiments fueled by different blends of n-octanol with pure diesel were conducted to analyze their impacts on engine performance and emissions. The methodology involved testing each blend in a single-cylinder engine, measuring engine performance parameters such as brake torque and brake power under full-load conditions across a range of engine speeds. Comparative assessments of performance and emission characteristics at a constant engine speed were also conducted with varying loads. The results indicated that while n-octanol blends consistently improved brake thermal efficiency, they also increased brake-specific fuel consumption due to the lower energy content of n-octanol. Consequently, while all n-octanol blends reduced nitrogen oxide emissions compared to pure diesel, they also significantly decreased carbon monoxide, hydrocarbons, and smoke opacity, presenting a comprehensive reduction in harmful emissions. However, the benefits came with complex trade-offs: notably, higher concentrations of n-octanol led to a relative increase in nitrogen oxide emissions as the n-octanol ratio increased. The study concludes that n-octanol significantly improves engine efficiency and reduces diesel dependence, but optimizing the blend ratio is crucial to balance performance improvements with comprehensive emission reductions.

This study investigated bio-based plastic cushioning materials foamed through water phase-change characteristics using the natural by-product wheat bran. Experiments were carried out while increasing the wheat bran content from 20% to 70% in a blended composite material of polypropylene (PP) and wheat bran (WB). From the experimental results, we were able to prepare a bio-based plastic cushion that contained a high amount of natural materials, with a bran content of over 50%. This indicates the possibility of meeting the criteria for biodegradable plastics, as well as bio-based plastics. In this study, by inducing a foaming ratio of 95% or more, a volume-expansion ratio from 16 times to over 62 times was achieved. In addition, the optimal mixing condition for inducing a high-expansion foam was when the mixing ratio of PP and WB was 50/50, and the water content of the foaming agent was 25 parts per hundred resin. Finally, dynamic cushioning characteristics of PP50/WB50 composite foam prepared in this study and Polystyrene (PS) bead based commercial products were compared. The composite foam of this study showed comparable values, confirming commercialization possibility.

A shell-and-tube absorber and an ammonia absorption refrigeration (AAR) system were constructed to study falling film absorption on a horizontal tube. An empirical and numerical combined method (ENCM) was developed to estimate the actual falling film thickness using parametric analysis with a simplified mathematical falling film model and experimental results. Numerical and experimental studies showed that the simplified mathematical falling film model has an exact physical response about ammonia absorption process in the absorber. The temperature difference of solution decreases with the increasing inlet coolant temperature. The heat transfer performance of a real type shell-and-tube absorber with the AAR system is a more sensitive function of the coolant inlet temperature than the solution inlet temperature. The ENCM developed in the present study can be used to estimate the actual thickness of a falling film along a horizontal tube in the shell-and-tube absorber of the AAR system, which is very difficult to measure experimentally. The ammonia absorption rate decreases with inlet temperature of a weak ammonia solution and inlet coolant temperature.

Capture of trace amounts (parts per trillion or ppt level) of 90Sr from highly Na+-rich (5 M or 115 000 parts per million) liquid wastes produced from reprocessing of spent nuclear fuel rods is crucial for continuous operation of nuclear power plants.

This study evaluates the performance of a plate heat exchanger numerically and experimentally. The predictive model for estimating the heat transfer and frictional pressure drop across the plain and offset strip fins is compared with the experimental results with the parameters of Reynolds number and fin pitch. The heat transfer of the offset fin shape is 13.4% higher than that of the plain fin in the experiment in the case of Re = 6112 for the hot airflow and Re = 2257 for the cold airflow. A predictive model uses the effectiveness-Number of Transfer Units (NTU) method with the discretization in the segments divided into small control volumes in the heat exchanger. The difference of heat transfer and pressure drop for the plain fin between the numerical and the experimental results are approximately 1.9% and 5.9%, respectively. Thus, the results indicate that the predictive model for estimating the heat transfer is useful for evaluating the performance of the plate heat exchanger in the laminar-to-transition regions.

This study introduces a novel methodology to calculate the carbon dioxide (CO2) emission reduction related to residual emissions, calculating the CO2 emission reduction through a 2 MW (40 tCO2/day) carbon capture and utilization (CCU) plant installed at a 500 MW coal-fired power plant in operation, to evaluate the accuracy, maintainability, and reliability of the quantified reduction. By applying the developed methodology to calculate the CO2 emission reduction, the established amount of CO2 reduction in the mineral carbonation was evaluated through recorded measurement and monitoring data of the 2 MW CCU plant at the operating coal-fired plant. To validate the reduction, the accuracy, reproducibility, consistency, and maintainability of the reduction should be secured, and based on these qualifications, it is necessary to evaluate the contribution rate of nationally determined contributions (NDCs) in each country. This fundamental study establishes the concept of CCU CO2 reduction and quantifies the reduction to obtain the validation of each country for the reduction. The established concept of the CCU in this study can also be applied to other CCU systems to calculate the reduction, thereby providing an opportunity for CCU technology to contribute to the NDCs in each country and invigorate the technology.