It is important to reveal the heat transfer and flow mechanisms of laser-induced nanobubble generation on nanoparticles in the fields of solar energy utilization, medical treatment, and seawater purification. In this study, a coupled framework integrating the phase-change lattice Boltzmann method (LBM) with the depth-first search (DFS) algorithm is proposed. The proposed framework accurately quantifies transient laser energy absorption based on instantaneous nanoparticle aggregation and nanobubble coverage. The nanoparticle trajectory in the fluid is studied based on the momentum exchange method. The convection is investigated by conjugated thermal boundary to investigate the temperature evolutions in the nanoparticles and the surrounding fluid. The interfacial thermal conductance, nanoparticle distance, the laser intensity, fluid velocity, and channel configuration effect on nanoparticle and nanobubble heat absorption, nanobubble generation, and nanoparticle motion are studied. The nanoparticle dimer enhances the nanobubble generation while the nanobubble coverage suppresses the nanobubble generation. The bubble volume ratio of the Y-shaped channel with the small bifurcation angle outstrips the vertical channel.
Noise and vibration caused by the operating principles and structural characteristics of diesel engines are critical in terms of passenger comfort and engine components' lifespan. The use of ethanol as a dual fuel in diesel engines and carbon nanotube (CNT) additives offers an innovative approach to optimizing noise and vibration levels by improving combustion characteristics. In this study, the effects of ethanol port injection rate, exhaust gas recirculation (EGR) rate, engine load, and nanotube-enhanced fuel types on the noise and vibration characteristics of a single-cylinder diesel engine were investigated. Experiments were conducted using different ethanol rates (10-30%), EGR rates (0-20%), and fuel types (neat diesel, diesel with 25-50 ppm SWCNT and MWCNT additives), and measurements of noise and vibration levels were performed using specialized sensors and data acquisition systems. Central composite design (CCD) was used to create the experimental matrix, while response surface methodology (RSM) was used for optimization. analysis of variance (ANOVA) showed that all input parameters significantly affected noise and vibration responses, with engine load emerging as the dominant factor. As a result of global optimization, the lowest noise (93.5 dBA) and vibration (88.9 m/s2) values were obtained at a 17.7% ethanol content, 20% EGR rate, and 50 ppm SWCNT-containing fuel coded SW50 under 0% load conditions. SWCNT-blended fuels demonstrated superior performance compared to neat diesel and MWCNT-blended fuels, particularly under low load conditions. The results indicate that moderate ethanol enrichment, appropriate EGR application, and CNT-blended fuels are effective strategies for reducing engine noise and vibration. The study provides a robust statistical basis for developing advanced combustion strategies to improve noise, vibration, and harshness (NVH) performance in compression-ignition engines.
This study numerically investigates the seasonal thermal performance of an indirect solar water heating (SWH) system designed for the continental climate of Central Asia. A detailed Python-based dynamic model was developed for a flat-plate collector and a stratified 300-L storage tank with an immersed coil heat exchanger. The model was validated using experimental data and TRNSYS simulations, showing good agreement with experimental measurements, consistent with typical accuracy levels of dynamic flat-plate collector models and 6-8% for tank charging/discharging. The validated framework was applied to five representative cities (Almaty, Astana, Atyrau, Tashkent, and Ashgabat). Results show strong seasonal variability: in summer, peak absorber temperatures reach 82-87 degrees C and top-layer tank temperatures 63-65 degrees C, enabling at least one hot-water draw-off event per day without auxiliary heating. In winter, maximum tank temperatures remain below 32-36 degrees C due to low irradiance, indicating the need for supplementary heating. Spring and autumn conditions produce intermediate performance, with top-layer temperatures of 46-60 degrees C depending on location. Overall, the proposed model reliably captures transient heat transfer, stratification, pump control behavior, and thermocline evolution, providing a flexible tool for optimizing indirect SWH systems in cold continental regions.
