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  • Open Access

    ARTICLE

    NUMERICAL ANALYSES ON VAPOR PRESSURE DROP IN A CENTERED-WICK ULTRA-THIN HEAT PIPE

    Yasushi Koitoa,*

    Frontiers in Heat and Mass Transfer, Vol.13, pp. 1-6, 2019, DOI:10.5098/hmt.13.26

    Abstract This paper describes extended numerical analyses on vapor pressure distribution in a centered-wick ultra-thin heat pipe. Analyses were conducted by using a three-dimensional model developed by the author. Numerical results were obtained changing design parameters and operating conditions of the heat pipe. Discussion was made on the heat transfer limit as well as the vapor pressure drop. Moreover, a simple method was also presented to evaluate the vapor pressure drop in the ultra-thin heat pipe. Calculated results with the simple method agreed in 10 % with the three-dimensional numerical results. More >

  • Open Access

    ARTICLE

    Efficient Explanation and Evaluation Methodology Based on Hybrid Feature Dropout

    Jingang Kim, Suengbum Lim, Taejin Lee*

    Computer Systems Science and Engineering, Vol.47, No.1, pp. 471-490, 2023, DOI:10.32604/csse.2023.038413

    Abstract AI-related research is conducted in various ways, but the reliability of AI prediction results is currently insufficient, so expert decisions are indispensable for tasks that require essential decision-making. XAI (eXplainable AI) is studied to improve the reliability of AI. However, each XAI methodology shows different results in the same data set and exact model. This means that XAI results must be given meaning, and a lot of noise value emerges. This paper proposes the HFD (Hybrid Feature Dropout)-based XAI and evaluation methodology. The proposed XAI methodology can mitigate shortcomings, such as incorrect feature weights and impractical feature selection. There are… More >

  • Open Access

    ARTICLE

    Carbon Capture from Flue Gas Based on the Combination of Non-Contact Hydrophobic Porous Ceramic Membrane and Bubbling Absorption

    Yongde Luo, Jiang Jin*, Hua Zhang*

    Journal of Renewable Materials, Vol.11, No.7, pp. 3143-3153, 2023, DOI:10.32604/jrm.2023.027396

    Abstract A hybrid system combined with a non-contact membrane and bubbling absorption is proposed to capture CO2 from flue gas. The non-contact way of membrane and liquid absorbent effectively avoids the reduction of gas diffusion flux through the membrane. High-porosity ceramic membranes in hybrid systems are used for gas-solid separation in fuel gas treatment. Due to the high content of H2O and cement dust in the flue gas of the cement plant, the membrane is hydrophobically modified by polytetrafluoroethylene (PTFE) to improve its anti-water, anti-fouling, and self-cleaning performances. The results show that the diffusion flux of CO2 through the membrane is… More >

  • Open Access

    ARTICLE

    PREDICTION OF MASS TRANSFER COEFFICIENT OF THE CONTINUOUS PHASE IN A STRUCTURED PACKED EXTRACTION COLUMN IN THE PRESENCE OF SIO2 NANOPARTICLES

    Fereshteh Salimi Nanadegani, Bengt Sunden*

    Frontiers in Heat and Mass Transfer, Vol.14, pp. 1-11, 2020, DOI:10.5098/hmt.14.21

    Abstract In this experimental study, mass transfer and hydrodynamic parameters of water/kerosene/acetic acid system in a packed column were investigated, in which the mass transfer direction was set from the continuous phase (saturated water of kerosene and acetic acid) to the dispersed phase (saturated kerosene of water) in all the experiments. To assess the impact of nanoparticles on mass transfer, the experiments were performed in the presence of SiO2 nanoparticles and absence of the nanoparticles. The results showed that the addition of the nanoparticles to the base fluid (saturated kerosene of water) increased the mass transfer efficiency to the critical concentration,… More >

  • Open Access

    ARTICLE

    DIRECT SIMULATIONS OF BIPHILIC-SURFACE CONDENSATION: OPTIMIZED SIZE EFFECTS

    Zijie Chena , Sanat Modaka, Massoud Kavianya,* , Richard Bonnerb

    Frontiers in Heat and Mass Transfer, Vol.14, pp. 1-11, 2020, DOI:10.5098/hmt.14.1

    Abstract In dropwise condensation on vertical surface, droplets grow at nucleation sites, coalesce and reach the departing diameter. In biphilic surfaces, when the hydrophobic domain is small, the maximum droplet diameter is controlled by the shortest dimension where the droplets merge at the boundary. Through direct numerical simulations this size-effect heat transfer coefficient enhancement is calculated. Then the 1-D biphilic surface is optimized considering the size-dependent hydrophilic domain partial flooding (directly simulated as a liquid rivulet and using the capillary limit), the subcooling (heat flux) and condenser length effects. The predicted performance is in good agreement with the available experiments. More >

  • Open Access

    ARTICLE

    In Tube Condensation: Changing the Pressure Drop into a Temperature Difference for a Wire-on-Tube Heat Exchanger

    Louay Abd Al-Azez Mahdi, Mohammed A. Fayad, Miqdam T. Chaichan*

    FDMP-Fluid Dynamics & Materials Processing, Vol.19, No.9, pp. 2201-2214, 2023, DOI:10.32604/fdmp.2023.027166

    Abstract A theoretical study based on the Penalty factor (PF) method by Cavallini et al. is conducted to show that the pressure drop occurring in a wire-on-tube heat exchanger can be converted into a temperature difference for two types of refrigerants R-134a and R-600a typically used for charging refrigerators and freezers. The following conditions are considered: stratified or stratified-wavy flow condensation occurring inside the smooth tube of a wire-on-tube condenser with diameter 3.25, 4.83, and 6.299 mm, condensation temperatures 35°C, 45°C, and 54.4°C and cover refrigerant mass flow rate spanning the interval from 1 to 7 kg/hr. The results show that the… More > Graphic Abstract

    In Tube Condensation: Changing the Pressure Drop into a Temperature Difference for a Wire-on-Tube Heat Exchanger

  • Open Access

    ARTICLE

    A COMPARISON OF THE EQUILIBRIUM AND THE DROPLETS BASED NON-EQUILIBRIUM COMPRESSIBLE PHASE CHANGE SOLVERS FOR CONDENSATION OF CARBON DIOXIDE INSIDE NOZZLES

    Kapil Dev Choudhary, Shyam Sunder Yadav , Mani Sankar Dasgupta

    Frontiers in Heat and Mass Transfer, Vol.16, pp. 1-10, 2021, DOI:10.5098/hmt.16.14

    Abstract In the current work, we simulate the condensation of supercritical CO2 during its high speed flow inside two different converging-diverging nozzles. We use the homogeneous equilibrium method and the classical nucleation theory based non-equilibrium phase change model for this purpose. The simulation results indicate significant influence of the nozzle inlet condition, nozzle shape and the fluid thermophysical behaviour on the nonequilibrium conditions prevailing inside the nozzles. We observe very low, ∼0.15 K, supercooling for the flow of CO2 inside the Claudio Lettieri nozzle compared to the supercooling of ∼3 K observed for the Berana nozzle. Very high nucleation rate (∼… More >

  • Open Access

    ARTICLE

    NUMERICAL ANALYSES ON VAPOR TEMPERATURE DROP IN AN ULTRA-THIN HEAT PIPE WITH A THIN WICK SHEET

    Yasushi Koito*

    Frontiers in Heat and Mass Transfer, Vol.16, pp. 1-6, 2021, DOI:10.5098/hmt.16.8

    Abstract Numerical analyses were conducted for an ultra-thin heat pipe in which a thin wick layer was placed on the bottom. The vapor temperature drop caused by vapor flow friction was discussed for two types of the ultra-thin heat pipes with small and large widths. The numerical results were compared with those obtained for an ultra-thin heat pipe with a centered-wick structure. It was confirmed that the vapor temperature drop was reduced effectively by increasing the width of the heat pipe. Therefore, a wider ultra-thin heat pipe, that is, an ultra-thin vapor chamber is a promising option for nextgeneration thermal management. More >

  • Open Access

    ARTICLE

    HEAT TRANSFER AND FLOW PROFILES IN ROUND TUBE HEAT EXCHANGER EQUIPPED WITH VARIOUS V-RINGS

    Amnart Boonloia, Withada Jedsadaratanachaib,*

    Frontiers in Heat and Mass Transfer, Vol.18, pp. 1-13, 2022, DOI:10.5098/hmt.18.2

    Abstract This study numerically investigates pressure loss, heat transfer and thermal efficiency in round tube heat exchangers attached with various types of Vrings. A typical type A V-ring is compared with two types of modified V-rings (type B and C). The impacts of blockage ratios, b/D = 0.05, 0.10, 0.15 and 0.20 for all V-ring types in the turbulent region are discussed (Re = 3000 – 20,000). Flow directions in the round pipe attached with the V-rings are varied. The V-apex setting downstream is referred to as “V-Downstream, while the V-apex setting upstream is referred to as “V-Upstream”. The flow and… More >

  • Open Access

    ARTICLE

    THE EFFECTS OF NUSSELT, REYNOLDS NUMBER, AND PRESSURE DROP ON THE THERMAL PERFORMANCE OF PIERCED PIN FINS

    Wadhah Hussein Al doori*

    Frontiers in Heat and Mass Transfer, Vol.19, pp. 1-9, 2022, DOI:10.5098/hmt.19.8

    Abstract Perforated fin forced convection heat transfer is the primary focus of this investigation. The purpose of this research is to see if perforated pin fins can help with heat transmission in the devices. Each pin's perforation diameter and number of holes are rigorously examined. The Nusselt numbers for perforated pins are 47 percent higher than those for solid pins, according to the study, and this number raises as the number of holes increases. The pressure drop is reduced by 19% when perforated pins are used instead of solid pins. Heat transmission in a round-holed pin fin was studied using forced… More >

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