A Comprehensive Study on Intermittent Operation of Horizontal Deep Borehole Heat Exchangers

Utilizing a deep Borehole Heat Exchanger (BHE) has been recognized as a clean, renewable, low-carbon-emission, and sustainable way for heating of residential buildings and greenhouses. In this study, the long-term performance of horizontal deep BHE in intermittent mode is scrutinized. In this regard, to predict the transient heat transfer process in the deep BHEs, a mathematical model is developed and then verified by using the experimental results. The effect various key parameters including flow rate of circulating fluid, undisturbed ground temperature, inlet fluid temperature, and ground thermal conductivity on the thermal performance of deep BHE in continuous and intermittent mode is studied. According to the results, increasing the flow rate of circulating fluid, undisturbed ground temperature, and ground thermal conductivity is favorable for heat extraction rate. Moreover, the effect of three specific parameters for intermittent operation including periodic time interval, flow rate ratio, and recovery period ratio on the long-term performance of horizontal deep BHE are scrutinized. Based on the results, by decreasing the periodic time interval and increasing the flow rate ratio, the mean heat extraction rate in the period of 30 years is increased and the mean borehole’s wall temperature is decreased. Furthermore, by increasing the recovery period ratio, the heat extraction rate increases significantly while the total extracted energy decreases.

Characterization of TiZrN and TaZrN Nanocomposite Multilayer Coating Deposited via RF/DC Magnetron Sputtering on AISI4140 Steel

In this present research work, TiZrN and TaZrN multilayer coating was deposited on 4140 steel by RF/DC magnetron sputtering for comparative work also prepared in single layer. The flow rate ratio of Ar/N2 was set to 15 : 3 sccm and the thin film was prepared by the PVD (physical vapor deposition) method by RF/DC magnetron using a Ti-Zr and Ta-Zr target with a purity of 99.99%. The crystal structure, surface morphology microstructure, and component arrangements were explored by X-ray diffraction (XRD), scanning electron microscope (SEM), and atomic force microscopy (AFM). It has been found that the crystal structure, surface morphology, microstructure, and elemental composition of the membrane are strongly dependent on deposition parameters. It is mechanically characterized by corrosion and Vickers hardness. In AFM measurements, coarse cluster particles with increasing Ti and Ta values not only increase the average roughness (Ra) by 2.341 nm (200°C) and 2.951 nm (400°C) but also have a continuous average thickness which was shown to increase by 1.504 nm and 781.75 nm. With the increase of hardness, the roughness decreases correspondingly. The TiZrN multilayer microhardness augmented to 314 GPa at 200°C and 371 GPa for TaZrN (400°C).

Highly Permeable Mixed Matrix Hollow Fiber Membrane as a Latent Route for Hydrogen Purification from Hydrocarbons/Carbon Dioxide

This work reported on the fabrication and investigation of a mixed matrix hollow fiber membrane (MMHFM) by incorporating commercially available alumina particles into a polyetherimide (PEI) polymer matrix. These MMHFMs were prepared by the dry-wet spinning technique. Accordingly, optimizing the spinning parameters, including the air gap distance and flow rate ratio, is key to determining the gas separation performance. However, there are few studies regarding the effect of the filler dimensions. Consequently, three sizes of alumina particles, 20 nm, 30 nm, and 1000 nm, were respectively added into the PEI phase to examine the influence of filler size on gas permeation property. Moreover, the permeation properties of lower hydrocarbons (i.e., ethane and propane) were also measured to evaluate potential for emerging applications. The results indicated the as-synthesized membrane exhibited a remarkable hydrogen permeance of 1065.24 GPU, and relatively high separation factors of 4.53, 5.77, and 5.39 for H2/CO2, H2/C2H6, and H2/C3H8, respectively. This resulted from good compatibility between the larger fillers and the PEI polymer, as well as a reduction in the finger-like voids. Overall, the MMHFM in this work was deemed to be a promising candidate to separate hydrogen from gas streams, based on the comparison of the separation performance against other reported studies.

Prediction Models of Droplet Characteristics Based on the Locally Convergent Configurations in PMMA Microchips

This paper novel designed the local convergence configuration in the coaxial channels to study the two-phase flow (lubricating oil (continuous phase, flow rate Q c)/deionized water (dispersed phase, flow rate Q d)). Two geometric control variables, the relative position (x) and tapering characteristics (α), had the different effects on the droplet formation. The increase of relative position x caused the higher frequency and finer droplets, and the increase of convergence angle α, took the opposite effects. The results indicated that the equivalent dimensionless droplet length Ld/Wout and the flow rate ratio Qd/Qc had an exponential relationship of about 1/2. Similarly, it was found that the dispersed droplets generating frequency and the two-phase capillary number, CaTP = uTPμc/σ, had an exponential relationship. The advantage of the convergent configurations in micro-channel was the size and efficiency of droplet generation was very favorable to be controlled by α and x.

Turbulence Calculations of a Dual-Structure Oxygen Lance for Converter Based on Hydrodynamics

The oxygen lance is a piece of special equipment in the converter steelmaking process for blowing oxygen into the molten steel. After more than 80 years of development, the structure and function of the oxygen lance have undergone many changes. In this paper, based on the theory of hydrodynamics, the jet behavior characteristics of a dual-structure oxygen lance for the converter are determined and optimized by CFD simulations and compared with those of the traditional-structure oxygen lance. The research results show that multiple jets deflect to the central axis of the oxygen lance during movement and the inclination angle of the nozzle holes influences the jet deflection. A decrease in the nozzle hole angle results in an increase in the mutual suction between the streams. With the increasing flow rate through the large holes in the new dual-structure oxygen lance, the dynamic radial pressure increases at the middle of the jet. The jet flow characteristics of the new dual-structure oxygen lance are better than those of the traditional oxygen lance. Its impact on the molten pool includes greater momentum, a larger impact area, and a more uniform and powerful stirring of the molten pool. A nozzle angle of 14° combined with a flow rate ratio of 65% and a nozzle angle of 17° combined with a flow rate ratio of 35% are the optimal parameters for the new dual-structure oxygen lance.

Numerical Investigation of a Designed-Inlet Optofluidic Beam Splitter for Split-Angle and Transmission Improvement

The beam splitter is one of the important elements in optical waveguide circuits. To improve the performance of an optofluidic beam splitter, a microchannel including a two-stage main channel with divergent side walls and two pairs of inlet channels is proposed. Besides, the height of the inlets injected with cladding fluid is set to be less than the height of other parts of the microchannel. When we inject calcium chloride solution (cladding fluid) and deionized water (core fluid) into the inlet channels, the gradient refractive index (GRIN) developed in fluids flowing through the microchannel split the incident light beam into two beams with a larger split angle. Moreover, the designed inlets yield a GRIN distribution which increases the light collected around the middle horizontal line on the objective plane, and so enhances the transmission efficiency of the device. To demonstrate the performance of the proposed beam splitter, we use polydimethylsiloxane to fabricate the microchannel. The results obtained by simulation and experiment are compared to show the effectiveness of the device and the validity of numerical simulation. The influence of the microchannel geometry and the flow rate ratio on the performance of the proposed beam splitter is investigated.

Microfluidic Technology for the Production of Hybrid Nanomedicines

Microfluidic technologies have recently been applied as innovative methods for the production of a variety of nanomedicines (NMeds), demonstrating their potential on a global scale. The capacity to precisely control variables, such as the flow rate ratio, temperature, total flow rate, etc., allows for greater tunability of the NMed systems that are more standardized and automated than the ones obtained by well-known benchtop protocols. However, it is a crucial aspect to be able to obtain NMeds with the same characteristics of the previously optimized ones. In this study, we focused on the transfer of a production protocol for hybrid NMeds (H-NMeds) consisting of PLGA, Cholesterol, and Pluronic® F68 from a benchtop nanoprecipitation method to a microfluidic device. For this aim, we modified parameters such as the flow rate ratio, the concentration of core materials in the organic phase, and the ratio between PLGA and Cholesterol in the feeding organic phase. Outputs analysed were the chemico–physical properties, such as size, PDI, and surface charge, the composition in terms of %Cholesterol and residual %Pluronic® F68, their stability to lyophilization, and the morphology via atomic force and electron microscopy. On the basis of the results, even if microfluidic technology is one of the unique procedures to obtain industrial production of NMeds, we demonstrated that the translation from a benchtop method to a microfluidic one is not a simple transfer of already established parameters, with several variables to be taken into account and to be optimized.

Numerical investigation on the behavior of combining open-channel flow

Open-channel flow is known as fluid flow with an open atmospheric surface. It has become an important issue especially when measuring the flow rate and depth of water as part of environmental management schemes. Many efforts have been made by the previous researchers to investigate the behavior of water flow. However, most studies on water flow have only been carried out in a straight prismatic main channel, either in a trapezoidal and rectangular type of channel section with lateral branch of angle of 90^o. In this study, the general equations of combining open-channel flow for trapezoidal and V-shaped channels are modified in the form of nonlinear polynomial equations. The proposed equations are solved using Newton-Raphson procedure to determine the upstream flow depth. All the computations and analysis of the behavior of water flow depth influenced by Froude number and flow rate ratio are performed using graphical user interface, which is designed in MATLAB software. Comparative analysis shows that the modified equations agree well with the experimental data as reported in the literature. The trapezoidal channel demonstrates the highest value of flow depth as the Froude number and flow rate ratio increase; thus, it has potential to avoid water overflow.