Band 23, Heft 2

In recent years, nanotechnology has emerged as a field of study concerned with producing materials at the nanoscale and their usage for research and commercial purposes like nanoelectronics, biomedicals, energy storage, environmental remediation, heat transfer applications, etc. This review provides a comprehensive analysis of nanofluid synthesis methods, specifically the one-step and two-step approaches, with a focus on their scalability and industrial feasibility. The main aim of this review article is to provide a quick reference for researchers working on the synthesis of nanofluids for heat transfer applications in various thermal systems. The development of nanofluids as enhanced thermal fluids is a result of the obvious demand for fluids that are more efficient. The review systematically examines recent advancements in nanofluids, emphasizing key factors influencing their thermal conductivity, such as nanoparticle properties, base fluids, concentration, stability, and dispersion mechanisms. Additionally, the study explores the integration of nanofluid in heat transfer applications such as heat exchangers, internal combustion (IC) engines, convective boiling, and renewable energy systems. Furthermore, to address sustainability and potential ecological effects of nanofluids applications, a discussion on environmental impact of nanofluids is presented, highlighting the need for green synthesis methods and life cycle assessments. This review intends to provide useful information about the development and optimization of nanofluids for efficient thermal management in future energy systems.

Iron-bearing dust particles demonstrate poor pelletizing performance, resulting in weak and easily pulverized dust pellets, consequently reducing the efficiency of the rotary hearth furnace process. To address this issue, the partial substitution of bentonite with organic binders to create composite binders offers several advantages and represents a crucial strategy for enhancing pellet performance. In this study, we established a liquid bridge model between iron-bearing dust particles and investigated the mechanism of organic binders (OB-A and OB-B) enhancing the cold strength of iron-bearing dust pellets using infrared spectroscopy and contact angle analysis methods. While OB-A enhanced the hydrophilicity of particle surfaces and promoted denser pellet structures, OB-B significantly improved the compressive strength of dry pellets by forming a sturdy network structure during the drying process. These discoveries underscore the potential of composite binders, notably AH-1 binders (comprising 2 % bentonite, 0.18 % OB-A, and 0.8 % OB-B), to enhance both the green and dry pellet performance of iron-bearing dust pellets. Furthermore, the interaction between OB-A and OB-B was found to result in a denser and stronger pellet structure. Such improvements have far-reaching implications for boosting the efficiency of the rotary hearth furnace process.

The efficient use of biomass and the treatment of dye-contaminated wastewater are urgent issues. In this study, a novel mesoporous lignin-based composite aerogel (SL/CMX/AM) is synthesized via a chemical cross-linking/freeze-drying method, and its structure was characterized by SEM, FI-TR, and BET. The results showed that the structure of aerogel was mesoporous with dimensions ranging from 10 to 50 nm. The mesoporous lignin-based composite aerogels were further applied for the adsorption of dyes. The results revealed that the optimal purifying conditions were as follows: the pH of MB solution was 11, the mass of the aerogel was 0.0100 g, the concentration was 200 mg g −1 , the adsorption time was 720 min, and the adsorption temperature was 313.15 K, producing the highest adsorption capacity of 39.80 mg g −1 . The adsorption mechanism was discussed. The adsorption process followed the pseudo-second-order model and was fitted to the Langmuir isotherm model. The thermodynamic parameters indicated that the adsorption of dyes onto the investigated material was an endothermic and spontaneous reaction at 293.15–313.15 K. Overall, this work guides the preparation of mesoporous lignin-based composite aerogels and their potential application in addressing dye-contaminated wastewater problems.

The process which converts carbon-enriched material like phytomass, biowaste, etc. into combustible gas i.e., producer gas is known as gasification. It provides a certain amount of gasifying agent. The increase in energy requirement needs sustainable environmental-friendly sustainable energy sources. Thus biomass is a renewable energy source that is less in pollution and serves as the best backup. In this study, the mixed rubber shell and palm kernel shell as the input feed in the weighing ratios of 3:1 were used in gasification. The agent used in the gasification process was air in the open-core downdraft gasifiers. In the experiment setup, the equivalence ratio (ø) varies in the range of 0.187–0.269. Finally, maximal power was determined as 63.796 kW having a feed rate of 38.9 kg/h at the equivalence ratio of 0.269. Thus experiment results show maximum cold gas efficiency (CGE) and calorific value of PG which is 87.6 % and 6.6332 MJ/m 3 at the equivalence ratio of 0.242. The highest values of CH4 and H2 of Producer Gas were 21.5  and 17 %. Also, phytomass consumption rates, PG flow rates, Producer Gas (PG) heating values, gas compositions, and efficiency of cold gas were evaluated in evaluating the gasifier performance. The producer generated by gasification of blended rubber shell – palm kernel shell was rich in constituents having many uses in generating power and also in fuel production. In agricultural majority nations, wastes from agriculture were not regularly maintained, therefore causing environmental pollution which disturbs the ecological system. Therefore, the present study recommends the appropriate usage of agricultural wastes effectively.

Antibiotics in water body pose a threat to the ecosystem and human health, and the removal of antibiotics in water is imperative. Ti 3 C 2 T x has high specific surface area and structural stability, but suffers from low catalytic activity and insufficient utilization of active sites. In this paper, Ti 3 C 2 T x /Bi 2 S 3 composites (named PTB and STB, respectively) were prepared by in situ synthesis and physical composite method. The introduction of Bi 2 S 3 extends the light absorption of the composites to the visible region. Meanwhile, the electron migration resistance in PTB is smaller and the photoresponse current is larger. PTB exhibited better adsorption-photocatalytic performance than STB and pure Ti 3 C 2 T x , with a removal efficiency of 89 %. In addition, the study investigated the effects of water quality parameters and proposed a possible photocatalytic mechanism. Finally, the tetracycline adsorption and photocatalytic performance of PTB in real water samples showed good results, especially in lake water and tap water.

Highly efficient activated carbon (AC) derived from tea residue was used to produce clean fuel through adsorptive desulfurization. It was synthesized by heating in an inert atmosphere and chemical activation using K 2 CO 3 . The characteristics of the sorbent were determined with various techniques that clarified the porous morphology and large surface area (1,254.4 m 2 /g) with suitable properties. The performance of constructed AC in removing of dibenzothiophene (DBT) from n -Hexane was examined under mild operating conditions of ambient temperature and contact time of 15 min, which possessed a high efficiency of 96.1 %. The Langmuir and Freundlich isotherms were applied to study the sulfur compounds’ equilibrium adsorption. Based upon the results, it can be effectively expressed by Langmuir isotherm. Two types of kinetic models were evaluated, and it was revealed that adsorption by using modified AC obeys a pseudo-second-order pattern. This research aimed to provide a cost-effective adsorbent with excellent activity for desulfurization on a large scale.

As the primary production equipment for high-purity magnesia, shaft kilns are extensively employed in metallurgical and chemical processes. Understanding and optimizing the internal flow dynamics and heat transfer mechanisms within high-purity magnesia shaft kilns can significantly enhance production efficiency and product quality while reducing energy consumption and mitigating environmental impacts. Particularly, the airflow characteristics in shaft kilns directly impact burner selection, bed height, fan selection, and fan power consumption, consequently affecting heat transfer properties within the kilns. The airflow pressure drop across the high-purity magnesia particle bed under varying operational conditions was systematically investigated via experimentation utilizing a self-built experimental setup. Initially, the fundamental macroscopic attributes of high-purity magnesia particles, including particle size distribution, density, sphericity, and voidage, were meticulously quantified. Subsequently, employing the aforementioned experimental platform, the impacts of differing gas apparent flow velocities and particle equivalent diameters on gas flow pressure drop were assessed and analyzed. Incorporating considerations for the wall effect, the existing frictional pressure drop correlation was recalibrated through fitting procedures to derive an experimental correlation characterizing gas flow pressure drop within the high-purity magnesia particle bed layer, with subsequent verification of its applicability. The findings reveal a linear relationship between the wall-corrected frictional pressure drop, f w and the wall-corrected particle Reynolds number, Re w , with a gradual increase in the slope of the curve. Considering the substantial deviation between experimental data and previously established resistance correlation equations, a novel resistance correlation applicable to the high-purity magnesia bed was formulated through data fitting. The pressure drop correlation obtained in the present work can well predict the gas flow resistance in the multi-size high-purity magnesia bed with an error of less than 7 %.

Ice slurry serves as an effective secondary-loop refrigerant, boosting system performance while simultaneously minimizing refrigerant charge and leakage. This not only enhances energy efficiency but also addresses environmental safety concerns. Unlike single-phase flow, ice slurry exhibits complex multi-phase dynamics, making its behavior in pipelines distinctly different. Since bend sections are essential for flexible routing in pipeline transportation, they also significantly influence the flow characteristics. In this study, the flow behavior of ice slurry within bend sections has been thoroughly examined. The investigation has been performed in 23 mm diameter pipe with 180° bend section with 2 different (Bend radius/Pipe radius) ratios of 2.98 & 5.6. The Eulerian multi-phase based CFD model is developed for the investigation which is first validated with literature. Investigation has been done for ice concentrations of 10, 20 and 30 % by volume at 1 m/s to 3 m/s velocities, and particles diameters of 0.25 mm and 0.40 mm. From the investigation, it has been observed that, concentration and velocity distributions are affected in bend section. The concentration exhibits a rising trend from the inner section toward the outer section of the bend, as well as along the upper region of the pipe. Additionally, an increase in the R / r ratio from 2.98 to 5.60 leads to a reduction in pressure drop by up to 9 %. This indicates that as the relative size changes, there is a noticeable decrease in pressure drop, suggesting a potential correlation between the radius ratio and fluid resistance or flow characteristics.

The incorporation of internal pipes is recognized as effective strategy to augment the heat transfer area within an externally heated drum, but their presence can substantially alter the granular flow dynamics, potentially affecting the thermal and mass transfer processes. This study utilizes the Discrete Element Method (DEM) to analyze the interaction between an internal pipe and particles within a rotary drum. The focus is on how the pipe diameter, position, and rotational speed affect the active layer’s proportion, velocity distribution, active-passive boundary dynamics, and particle diffusion coefficient. Based on the observed flow phenomena, the rolling flow pattern within a free drum is further divided into several sub-patterns. The results demonstrate that the presence of an internal pipe divides the bed into five distinct flow patterns: Single-Cycle, Dual-Cycle, Triple-Cycle, Slumping-Rolling and Moving-Bed flow mode. When the pipe is positioned within the active layer and its diameter is smaller than the maximum thickness of the active layer in a free drum, the bed is inclined to develop a Dual-Cycle mode. In this mode, an increase in pipe diameter results in an increase in the time-averaged proportion of the active layer but a decrease in velocity and diffusion coefficient. Conversely, if the pipe’s diameter is larger, a Slumping-Rolling flow structure emerges, leading to a decrease in the active layer’s time-averaged proportion, velocity, and diffusion coefficient. As the pipe is moved from the active-passive interface towards the drum wall, the bed undergoes a transition from Single-Cycle and Triple-Cycle modes to Moving-Bed flow mode. During this transition, there is an initial rise followed by a notable drop in the time-averaged proportion, velocity, and diffusion coefficient of the active layer. Additionally, increasing the rotational speed does not alter the Triple-Cycle pattern but promotes the expansion of the active layer’s volume and enhances particle activity.