| 1. |
- Gu, Huaduo, et al.
(författare)
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Analysis, modeling and simulations of an innovative sliding vane rotary compressor with a rotating cylinder
- 2021
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Ingår i: Energy Conversion and Management. - : Elsevier BV. - 0196-8904. ; 230
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Tidskriftsartikel (refereegranskat)abstract
- A novel sliding vane rotary compressor with a rotating cylinder is proposed in this paper. The sliding vane dynamics analysis reveals that, compared with the traditional compressor, the friction loss at the sliding vane tips and between rotor and cylinder can be reduced to 0.25% and 10.23%. To numerically investigate the internal flow mechanism, a reliable three-dimensional simulation method is developed via Fluent 2020R1. Three pressure ratios are considered. During transient calculations, all parameters begin to fluctuate periodically after the fourth round. Both temperature and pressure for a single chamber reach the maximum near the exhaust port. As the pressure ratio εp increases from 5, 10 to 15, the outlet temperature increases from 496.9, 623.0 to 754.4 K and the mass flow rate decreases from 0.03089, 0.02946 to 0.02764 kg/s, the volumetric efficiency and isentropic compression efficiency decrease, with the maximum values of 97.14% and 90.33%. The gaps between the rotor and the cylinder and at the vane tips are 0.03 and 0.01 mm, but the leakage mass of the former is one order higher than that of the latter. The research can provide guidance for the design and practical application of sliding vane rotary compressors.
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| 2. |
- Huang, Dan, et al.
(författare)
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Experimental study on heat transfer of nanofluids in a vertical tube at supercritical pressures
- 2015
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Ingår i: International Communications in Heat and Mass Transfer. - : Elsevier BV. - 0735-1933. ; 63, s. 54-61
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Tidskriftsartikel (refereegranskat)abstract
- Regenerative cooling system at supercritical conditions can accommodate high heat fluxes effectively in aerospace applications. The potential of nanofluids as regenerative coolants at supercritical pressures was evaluated in this work. Experiments were carried out to study the heat transfer characteristics of Al2O3-kerosene nanofluids flowing upward in a vertical minitube at supercritical pressures. Parametric effects of mass flow rate, heat flux, pressure and particle content on the heat transfer performance are presented. Results show that increasing the mass flow rate or pressure enhances heat transfer, while higher heat fluxes lead to poorer heat transfer performance. Nanofluids tend to deteriorate heat transfer at supercritical pressures because deposition of the nanopartides smoothens the wall roughness and presents an additional thermal resistance. As the particle content increases, the heat transfer performance becomes worse. Based on the experimental data, a heat transfer correlation was established for Al2O3-kerosene nanofluids at supercritical pressures and the correlation shows good predictive ability. (C) 2015 Elsevier Ltd. All rights reserved.
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| 3. |
- Wu, Zan, et al.
(författare)
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Convective vaporization in micro-fin tubes of different geometries
- 2013
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Ingår i: Experimental Thermal and Fluid Science. - : Elsevier BV. - 1879-2286 .- 0894-1777. ; 44, s. 398-408
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Tidskriftsartikel (refereegranskat)abstract
- An experimental investigation was performed for convective vaporization of R22 and R410A inside one smooth tube and five micro-fin tubes with the same outer diameter of 5 mm. Data are for mass fluxes ranging from 100 to 620 kg/m2 s at 279 K saturation temperature. The results suggest that the tube with fin height of 0.15 mm, apex angle of 25° and 38° starts has the best thermal performance for convective vaporization when mass velocity is less than 400 kg/m2 s, while the tube with fin height of 0.12 mm, apex angle of 25° and 58° starts has the best heat transfer performance at larger mass velocities, which is probably due to the relative size between fin height and liquid film thickness. Considering the effects of micro-fin on flow boiling, a new general semi-empirical model has been developed based on the present data and recent data from literature. The new model is applicable for intermittent and annular flow patterns, covering different fluids, nominal diameters from 2.1 to 14.8 mm, mass fluxes from 100 to 650 kg/m2 s, heat fluxes based on the total inner surface area from 0 to 30 kW/m2, and reduced pressure from 0.08 to 0.69. The model predicts the parametric trends correctly and the average and local heat transfer coefficients accurately. The heat transfer mechanism can also be observed clearly by the new model.
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| 4. |
- Yang, Yanjie, et al.
(författare)
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Transport dynamics of droplet impact on the wedge-patterned biphilic surface
- 2020
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Ingår i: Experimental Thermal and Fluid Science. - : Elsevier BV. - 0894-1777 .- 1879-2286. ; 113
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Tidskriftsartikel (refereegranskat)abstract
- Droplet impact on biphilic surfaces with a wettability contrast has been intensively studied in recent years. In this work the effects of tilting and apex angles on droplet transport dynamics after impacting on a wedge-patterned biphilic surface at low Weber numbers were investigated experimentally. The biphilic surface was fabricated by applying a hydrophobic polymer coating on a bare silicon surface. According to the experimental results, a larger apex angle below 67.4° can accelerate the droplet effectively at first. Then the friction force controls the droplet movement and reduces the speed. The tilting angle along the hydrophilic direction activates the droplet. If the gravity component is opposite to the hydrophilic direction and the tilting angle is over 15°, the droplet can hardly move toward the hydrophilic area. By modeling the hydrodynamics of the droplet movement after impact on a biphilic surface with assumptions of no evaporation, no Marangoni effect, negligible dynamic contact angle variation and negligible rotation effect, the surface tension values versus the position at different apex angles are derived. The predicted position versus time trends agree well with the experimental data. This study aims to provide a better understanding of the mechanisms of droplet hydrodynamics on wedge-patterned biphilic surfaces at low Weber numbers.
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| 5. |
- Abbood, Sahar A., et al.
(författare)
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Numerical study of natural convection for cu and tio 2 nanofluids inside different enclosures
- 2017
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Ingår i: Proceedings of CHT-17 ICHMT International Symposium on Advances in Computational Heat Transfer, 2017. - 9781567004618 ; , s. 1403-1418, s. 1403-1418
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Konferensbidrag (refereegranskat)abstract
- In this study, steady-state laminar natural convection of Cu and TiO 2 nanofluids inside different enclosures is numerically investigated. Natural convection is concerned due to a temperature difference between the hot and cold surfaces. The Boussinesq approximation is used to form the governing equations and the commercial software package ANSYS Fluent version 14.0 is used to numerically solve the governing equations. The temperature profiles and flow patterns at different Rayleigh numbers, i.e., 10 4 , 10 5 and 10 6 are studied and compared for the different curved geometries which are 1/8, 2/8 and 3/8 from the height of the enclosure. Heat transfer coefficients are presented for the enclosures with different nanofluid concentrations. The nanoparticles enhance the heat transfer. The heat transfer enhancement increases with increasing nanoparticle concentrations. A new curved enclosure is suggested to augment heat transfer.
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| 6. |
- Abbood, Sahar A., et al.
(författare)
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Thermal assessment for prostheses : State-of-the-art review
- 2017
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Ingår i: International Journal of Computational Methods and Experimental Measurements. - 2046-0546. ; 5:1, s. 1-12
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Tidskriftsartikel (refereegranskat)abstract
- Hundreds of young people have had limbs amputated after being wounded by civil wars, explosions or gunshots. Heat and perspiration within a prosthetic socket are the most common side effects of reduced quality life for prosthesis. Besides, the environment between liner and skin is an ideal host of residual limb skin problems such as contact dermatitis and bacterial infections. It is important to minimize the limiting heat transfer to improve amputee safety and comfort. Usually, when there is a skin problem, the treatment requires the amputee not to wear his/her prosthesis for an extended period of time. This functional loss can adversely affect the amputee’s physical, mental and emotional well-being. This work aims to highlight a number of important issues concerning the effect of thermal conditions on prosthetics to shed light on new design methods for prosthetics.
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| 7. |
- Abdul Fattah Abood, Sahar, et al.
(författare)
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Analysis of natural convection of Cu and TiO2nanofluids inside nonconventional enclosures
- 2018
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Ingår i: Journal of Enhanced Heat Transfer. - 1563-5074. ; 25:4-5, s. 315-332
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Tidskriftsartikel (refereegranskat)abstract
- Steady-state laminar natural convection of Cu and TiO2 nanofluids inside different enclosures is numerically investigated. Natural convection is concerned due to a temperature difference between the hot and cold surfaces. The Boussinesq approximation is used to form the governing equations and the commercial software package ANSYS FLUENT version 14.0 is used to numerically solve the governing equations. The temperature profiles and flow patterns at different Rayleigh numbers, i.e., 104, 105and 106 are studied and compared for different curved geometries which are 1/8, 2/8 and 3/8 of the height of the enclosure. Heat transfer coefficients are presented for enclosures with different nanofluid concentrations. The nanoparticles enhance the heat transfer. The heat transfer enhancement increases with increasing nanoparticle concentrations. A new curved enclosure is suggested to augment heat transfer.
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| 8. |
- Abdul Fattah Abood, Sahar, et al.
(författare)
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Numerical study of natural convection for Al2O3 and CuO nanofluids inside different enclosures
- 2016
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Ingår i: ; , s. 1-4
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Konferensbidrag (refereegranskat)abstract
- In this study steady-state natural convection for Al2O3 and CuO nanofluids inside different enclosures are numerically investigated. Natural convection is concerned due to a temperature difference between hot and cold surfaces. Rectangular and curved enclosures are investigated. The Boussinesq approximation is used to form the governing equations and the commercial software package ANSYS Fluent version 14.0 is used to numerically solve the governing equations. The temperature profiles and flow patterns for different cases are studied. Heat transfer coefficients for various Rayleigh numbers are presented for the enclosures with different nanofluid concentrations. The nanoparticles enhance the heat transfer. The heat transfer enhancement increases with increase in nanoparticle concentration. A new curved enclosure is suggested to provide highest heat transfer.
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| 9. |
- Andersson, Martin, et al.
(författare)
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A Review of Cell-Scale Multiphase Flow Modelling, including Water Management, in Polymer Electrolyte Fuel Cells
- 2016
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Ingår i: Applied Energy. - : Elsevier BV. - 1872-9118 .- 0306-2619. ; 180, s. 757-778
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Tidskriftsartikel (refereegranskat)abstract
- The PEFC has emerged as the most viable fuel cell type for automotive and some portable applications, and also has potential back-up power unit applications due to its low operating temperature, comparative simplicity of construction, high power density, and ease of operation. In spite of tremendous scientific advances, as well as engineering progress over the last few decades, the commercialization of PEFCs remains unrealized, owing primarily to economic viability associated with the high prices of materials and components and technical problems relating primarily to water management. The difficulty in addressing the water management issues lies mostly in the two-phase multi-component flow involving phase-change in porous media, coupled heat and mass transfer, interactions between the porous layers and gas channel (GC) and the complex relationship between water content and cell performance. Due to the low temperature of operation, water generated by the electrochemical reactions often condenses into liquid form, potentially flooding the gas diffusion layer (GDL), GC or other components. Insight into the fundamental processes of liquid water evolution and transport is still lacking, preventing further enhanced PEFC development.The aim of this paper is to give a comprehensive introduction to PEFC modeling inside GCs and GDLs, with a focus on two-phase flow and related phase-change and transport processes. Relevant momentum, mass and heat transport processes are introduced and the microstructural effects on the transport processes inside the porous GDL are extensively discussed.The selection of a computational approach, for the two-phase flow within a GDL or GC, for example, should be based on the computational resources available, concerns about time and scale (microscale, cell scale, stack scale or system scale), as well as accuracy requirements. One important feature, included in some computational approaches, is the possibility to track the front between the liquid and the gas phases. To build a PEFC model, one must make a large number of assumptions. Some assumptions have a negligible effect on the results and reliability of the model. However, other assumptions may significantly affect the result. It is strongly recommended in any modeling paper to clearly state the assumptions being implemented, for others to be able to judge the work.It is important to note that a large fraction of the expressions that presently are used to describe the transport processes inside PEFC GDLs were originally developed to describe significantly different systems, such as sand or rocks. Moreover, the flow pattern maps and pressure drop correlations of two phase flow in micro channels may not be applicable for GCs due to one side wall being porous, with the resulting interaction between the GDL and GC.
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| 10. |
- Bernhardsson, Carolina, et al.
(författare)
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Development of a highly efficient 50K single nucleotide polymorphism genotyping array for the large and complex genome of Norway spruce (Picea abies L. Karst) by whole genome resequencing and its transferability to other spruce species
- 2021
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Ingår i: Molecular Ecology Resources. - : John Wiley & Sons. - 1755-098X .- 1755-0998. ; 21:3, s. 880-896
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Tidskriftsartikel (refereegranskat)abstract
- Norway spruce (Picea abies L. Karst) is one of the most important forest tree species with significant economic and ecological impact in Europe. For decades, genomic and genetic studies on Norway spruce have been challenging due to the large and repetitive genome (19.6 Gb with more than 70% being repetitive). To accelerate genomic studies, including population genetics, genome-wide association studies (GWAS) and genomic selection (GS), in Norway spruce and related species, we here report on the design and performance of a 50K single nucleotide polymorphism (SNP) genotyping array for Norway spruce. The array is developed based on whole genome resequencing (WGS), making it the first WGS-based SNP array in any conifer species so far. After identifying SNPs using genome resequencing data from 29 trees collected in northern Europe, we adopted a two-step approach to design the array. First, we built a 450K screening array and used this to genotype a population of 480 trees sampled from both natural and breeding populations across the Norway spruce distribution range. These samples were then used to select high-confidence probes that were put on the final 50K array. The SNPs selected are distributed over 45,552 scaffolds from the P. abies version 1.0 genome assembly and target 19,954 unique gene models with an even coverage of the 12 linkage groups in Norway spruce. We show that the array has a 99.5% probe specificity, >98% Mendelian allelic inheritance concordance, an average sample call rate of 96.30% and an SNP call rate of 98.90% in family trios and haploid tissues. We also observed that 23,797 probes (50%) could be identified with high confidence in three other spruce species (white spruce [Picea glauca], black spruce [P. mariana] and Sitka spruce [P. sitchensis]). The high-quality genotyping array will be a valuable resource for genetic and genomic studies in Norway spruce as well as in other conifer species of the same genus.
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