Two-Phase Flow Development of R134a in a Horizontal Pipe: Computational Investigation

To improve the performance of vapor compression refrigeration systems that use vertical gravitational flash tank separators, the liquid separation efficiency of the vertical gravitational flash tank separator requires to be approved. To approach this improvement, the two-phase flow development and its behavior after the expansion device need to be investigated and predicted. For thus, this paper presents a three-dimensional computational investigation of the two-phase flow development of R134a after the expansion device in a horizontal pipe. Computational Fluid Dynamic (CFD) was used to predict the two-phase development and its behavior in the horizontal pipe. ANSYS 16.2 program was used to generates the geometry of the three-dimensional horizontal pipe of 2 meters long and 25 mm inner diameter. The hexahedral mesh was generated and it is assessed to obtain the optimum mesh size and number. Eulerian-Eulerian two-phase model was used with k-ɛ turbulence model. R134a was used as a working fluid in the horizontal pipe utilizing four different inlet diameters: 12, 12.5, 25, and 50.0 mm. Mass flux and vapor quality have been changed from 288 to 447 kg/m2.s and from 10 to 20% respectively. Results were validated against experimental results from the literature and revealed that the separation region length is affected by the initial phase velocities, inlet vapor quality, and inlet tube diameter. An empirical correlation to predict the expansion region length is proposed as a function of Froude, Webber, and Lockhart-Martinelli numbers.

Analysis of condensation flow pattern and heat transfer of a cryogenic loop heat pipe with different heating powers

The cryogenic fluids' flow performance and condensation characteristics with different heating powers in cryogenic loop heat pipes (CLHPs) have not been studied due to the difficulty of measurement at low temperature. In this study, a test system was designed and fabricated to characterize the condensation flow patterns of a propylene CLHP and its heat transfer performance with different heating powers. The results show that the two-phase region length and flow pattern in the condenser were closely related to the operation mode of the CLHP. The vapor front in the condenser oscillated at the condenser inlet at a low heating power, which resulted in an unstable operation of the CLHP. Moreover, by comparing the condensation heat transfer coefficient (HTC) with the condensation correlations, the Cavallini correlation is recommended for the design of CLHP condenser.

A Study on the Effect of the Structural Parameters and Internal Mechanism of a Bilateral Gate-Controlled S/D Symmetric and Interchangeable Bidirectional Tunnel Field Effect Transistor

A bilateral gate-controlled S/D symmetric and interchangeable bidirectional tunnel field effect transistor (B-TFET) is proposed in this paper, which shows the advantage of bidirectional switching characteristics and compatibility with CMOS integrated circuits compared to the conventional asymmetrical TFET. The effects of the structural parameters, e.g., the doping concentrations of the N+ region and P+ region, length of the N+ region and length of the intrinsic region, on the device performances, e.g., the transfer characteristics, Ion–Ioff ratio and subthreshold swing, and the internal mechanism are discussed and explained in detail.

The Complete Mitogenome of Curculio Chinensis (Coleoptera: Curculionidae: Curculioninae): Structural Characterization and Phylogenetic Implication

To explore the phylogenetic position of Curculio chinensis Chevrolat, 1878 and phylogenetic relationships among major lineages of the family Curculionidae, we sequenced and annotated this mitogenome. The mitogenome is 18,680 bp in length, and includes the 37 typical mitochondrial genes and a large control region (length: 1,997 bp). Mitogenome organization, nucleotide composition, and codon usage are similar to most of the previously sequenced Curculioninae mitogenomes. All 13 protein-coding genes use ATN or TTG as start codon, and end with TAA/G or incomplete stop codons (single T-). Twenty-one transfer RNA genes have the typical clover-leaf structures, while the dihydrouridine (DHU) arm of trnS1 is missing. In Curculioninae mitogenomes, the size and number of tandem repeats in the control region are highly variable. Both ML and BI analyses based on the 13 PCGs and two rRNAs from 91 species of Coleoptera strongly supported the monophyly of Curculionidae and three of the included subfamilies (Platypodinae, Dryophthorinae, and Cryptorhynchinae) plus the sister relationship between Platypodinae and Dryophthorinae. Additionally, the monophyly of the genus Curculio was recovered with strong support.

Constraining the CME parameters of the spheromak flux rope implemented in EUHFORIA

<p>Coronal mass ejections (CMEs) are primary drivers of space weather phenomena. Modelling the evolution of the internal magnetic field configuration of CMEs as they propagate through the interplanetary space is an essential part of space weather forecasting. EUHFORIA (EUropean Heliospheric FORecasting Information Asset) is a data-driven, physics-based model, able to trace the evolution of CMEs and CME-driven shocks through realistic background solar wind conditions. It employs a spheromak-type magnetic flux rope that is initially force-free, providing it with the advantage of modelling CME as magnetised structures. For this work we assessed the spheromak CME model employed in EUHFORIA with a test CME case study. The selected CME eruption occurred on the 6th of January 2013 and was encountered by two spacecraft, Venus Express and STEREO--A, which were radially aligned at the time of the CME passage. Our focus was to constrain the input parameters, with particular interest in: (1) translating the angular widths of the graduated cylindrical shell (GCS) fitting to the spheromak radius, and (2) matching the observed magnetic field topology at the source region. We ran EUHFORIA with three different spheromak radii. The model predicts arrival times from half to a full day ahead of the one observed <em>in situ</em>. We conclude that the choice of spheromak radius affected the modelled magnetic field profiles, their amplitude, arrival times, and sheath region length.</p>

Numerical Investigation on Hydrodynamic Characteristics of Immersed Buoyant Platform

The Next Generation Subsea Production System (NextGen SPS) is considered as a competitive alternative system used for offshore petroleum production in ultra-deep sea based on the artificial seabed technology. The Immersed Buoyant Platform (IBP), which is located at a constant depth below the free surface of the water to minimize wave loading, provides a buoyant stable platform for supporting the well completion equipment. Therefore, the hydrodynamic characteristics of IBP in the currents play an essential role in determining the global responses of NextGen SPS. In this paper, aiming at acquiring an optimum structural form of IBP, the hydrodynamic characteristics of the flow past the cylindrical IBP with different height-to-diameter ratios are systematically investigated by use of the large eddy simulation (LES) approach. The simulations with fifteen different height-to-diameter ratios (H/D) are investigated. The Reynolds numbers are ranged from 0.94×106 to 3.45×106. It can be verified that the separated fluid reattaches on the surface of the cylinder when the aspect ratio is between 0.1 and 0.4. Due to the specific shape ratio and obvious 3D effect of the cylindrical IBP, no significant vortex shedding has been clearly observed when the aspect ratio is between 0.1 and 0.4. In the case of 0.4≤H/D≤5.0, a series of regular and alternating vortex street shedding appear behind the circular cylinder. The simulation results also show that the recirculation region length behind the cylindrical IBP can be significantly reduced with the decreasing aspect ratio. It can be concluded that the cylindrical IBP performs the best hydrodynamic characteristics when the aspect ratio is between 0.3 and 0.4. The research findings will be of great significance to providing valuable reference and foundation to determine the optimum form of underwater structures, such as the buoyancy cans of the hybrid riser system.

Reanalysis and Revision of the Complete Mitochondrial Genome of Artemia urmiana Günther, 1899 (Crustacea: Anostraca)

In the previously published mitochondrial genome sequence of Artemia urmiana (NC_021382 [JQ975176]), the taxonomic status of the examined Artemia had not been determined, due to parthenogenetic populations coexisting with A. urmiana in Urmia Lake. Additionally, NC_021382 [JQ975176] has been obtained with pooled cysts of Artemia (0.25 g cysts consists of 20,000–25,000 cysts), not a single specimen. With regard to coexisting populations in Urmia Lake, and intra- and inter-specific variations in the pooled samples, NC_021382 [JQ975176] cannot be recommended as a valid sequence and any attempt to attribute it to A. urmiana or a parthenogenetic population is unreasonable. With the aid of next-generation sequencing methods, we characterized and assembled a complete mitochondrial genome of A. urmiana with defined taxonomic status. Our results reveal that in the previously published mitogenome (NC_021382 [JQ975176]), tRNA-Phe has been erroneously attributed to the heavy strand but it is encoded in the light strand. There was a major problem in the position of the ND5. It was extended over the tRNA-Phe, which is biologically incorrect. We have also identified a partial nucleotide sequence of 311 bp that was probably erroneously duplicated in the assembly of the control region of NC_021382 [JQ975176], which enlarges the control region length by 16%. This partial sequence could not be recognized in our assembled mitogenome as well as in 48 further examined specimens of A. urmiana. Although, only COX1 and 16S genes have been widely used for phylogenetic studies in Artemia, our findings reveal substantial differences in the nucleotide composition of some other genes (including ATP8, ATP6, ND3, ND6, ND1 and COX3) among Artemia species. It is suggested that these markers should be included in future phylogenetic studies.