Condenser performance in a cylindrical humidification and dehumidification (HDH) system

In recent years, humidification and dehumidification (HDH) systems have garnered significant attention due to their enhanced effectiveness with packed beds, particularly for high-salinity waters. The direct-contact packed beds HDH system offers a more convenient and efficient installation compared with conventional HDH systems. This paper introduces a novel, compact cylindrical crossflow HDH system design that is easily constructed and scalable for industrial and residential applications. The compact crossflow-packed bed condenser employs perforated air tubes to distribute humidified air radially while cooling water drips vertically through the packed bed, coming into direct contact with the humidified air. To evaluate the system's performance, two-dimensional steady-state energy, and mass conservation equations were developed solving enthalpies instead of temperatures as dependents. The coupled partial differential equations were numerically solved to predict water temperature, air/vapor temperature, humidity ratio, and condenser effectiveness. Multiple designs were proposed, demonstrating that the proposed configuration can achieve effectiveness above 0.80 and a water production rate of 3.85 g/s under ideal operating conditions.     

Preparation of high isotactic polybutene‐1

Polymerization of butene‐1 (B‐1) was carried out with a PP‐TiCl₃/Et₂AlCl/methyl methacrylate (MMA) catalyst system in n‐heptane. The influence of temperature, pressure, time and H₂ on molecular weight, isotacticity, and catalytic activity were studied by viscometry, solubility in boiling diethyl ether, and measuring the polymer produced, respectively. The structural properties of the isotactic polybutene‐1 (IPB‐1) were characterized by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and melt flow index (MFI). The molecular weight of the products can be controlled by H₂. It was found that the catalyst showed high isotacticity and activity. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 2533–2539, 2000     

Designing scalable product families by the radial basis function–high-dimensional model representation metamodelling technique

Product family design is cost-efficient for achieving the best trade-off between commonalization and diversification. However, for computationally intensive design functions which are viewed as black boxes, the family design would be challenging. A two-stage platform configuration method with generalized commonality is proposed for a scale-based family with unknown platform configuration. Unconventional sensitivity analysis and information on variation in the individual variants’ optimal design are used for platform configuration design. Metamodelling is employed to provide the sensitivity and variable correlation information, leading to significant savings in function calls. A family of universal electric motors is designed for product performance and the efficiency of this method is studied. The impact of the employed parameters is also analysed. Then, the proposed method is modified for obtaining higher commonality. The proposed method is shown to yield design solutions with better objective function values, allowable performance loss and higher commonality than the previously developed methods in the literature.     

A new layered manufacturing machine with cutting force analysis in tapered end milling

We introduce a new layered manufacturing machine with its associated geometric cutting force model. This machine is designed to build metal parts and is a modified type of commercial layered object manufacturing (LOM) machine. This apparatus uses tapered end mills with different angles instead of laser to cut the layer edges. The proposed machine needs higher stiffness, because cutting action would regularly create more inaccuracy. Consequently, a new force model is considered that takes into account cutting conditions, cutter geometry and combination of tool-workpiece materials. Then, by force and stress analysis cutting-force induced inaccuracy has been evaluated for different components of the machine. Finally, the effectiveness of the machine and its capability to build functional metal parts with different geometries is clearly shown.     

The effect of anisotropic dispersion on the convective mixing in long‐term CO2 storage in saline aquifers

Carbon dioxide storage in deep saline aquifers is considered a possible option to bring greenhouse gas emissions under control. The understanding of the underlying mechanisms, such as convective mixing and associated mechanisms, affecting this mixing may have an impact on the long‐term sequestration process in deep saline aquifers. One of the significant aspects of the flow of miscible species in porous media is velocity dependent dispersion. The effect of dispersion on dissolution of carbon dioxide (CO₂) into brine is investigated by full nonlinear numerical simulations. This study reveals that dispersion may dramatically change the trend of CO₂ dissolution into brine. It was found that the dissolution of CO₂ increases as dispersion strength increases. The mixing pattern also shows three different mechanisms: diffusion, convection, and a highly nonlinear interaction mechanism. However, the medium dispersivity ratios were found to slightly affect the mixing, while having an impact on the fingering pattern. © 2010 American Institute of Chemical Engineers AIChE J, 2011     

Effect of nonionic side chain length of polycarboxylate-ether-based high-range water-reducing admixture on properties of cementitious systems

Despite the large variations in the behaviors of water-reducing admixtures upon changes in their structures, most previous reports on the cement-admixture compatibility did not provide sufficient information on the structure of the admixture. Hence, the evaluation and generalization of the reports on the cement-admixture compatibility are challenging. In this study, three different polycarboxylate-ether-based water-reducing admixtures with the same free nonionic content, anionic/nonionic molar ratio, and main chain length and different side chain lengths were produced. The compatibility of these admixtures with a CEM I 42.5R-type cement was investigated. In addition, an analysis of variance was performed on the experiment results to evaluate the contributions of the admixture type, admixture/cement ratio, and elapsing time to the Marsh funnel flow time, mini-slump, slump flow, and compressive strength. The water-reducing admixtures having long or short side chains reduced the initial flow characteristics of the cementitious systems. However, the admixture having the shortest side chain was better with regard to flow retention. The side chain length of the admixture did not have significant effects on the compressive strength and water absorption capacity of the mortar mixtures and mini-slump performances of the cement paste mixtures. Regarding the behaviors of the admixtures in the cementitious systems, an optimal admixture side chain molecular weight is proposed.