Journal: International Journal of Heat and Mass Transfer

Abbreviation

Int. J. Heat Mass Transfer

Publisher

Elsevier

Journal Volumes

ISSN

0017-9310
1879-2189

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Publications1 - 10 of 94
  • Enhancing the flow and heat transfer in a convective cavity using symmetrical and adiabatic twin fins
    Item type: Journal Article
    Liu, Yang; Zhang, Shuaikun; Huang, Han; et al. (2019)
    International Journal of Heat and Mass Transfer
    The enhancement of natural convection flow and the associated heat transfer in a differentially heated cavity with two horizontal adiabatic fins attached to each sidewall are numerically investigated at different Rayleigh numbers and with various fin positions in this study. The numerical approach is validated by both representative scales and experimental shadowgraph results. A typical double-plume flow regime is identified at both the early and fully-developed stages. The interaction of the two plumes is investigated in detail in this paper. With the increasing of the Rayleigh number, the separation frequency of the plume above both fins increases. It is also revealed that the separation frequency of the upstream plume at the quasi-steady stage does not only depend on the characteristics of the upstream flow, but also greatly depends on the position of the downstream fin. The frequency varies non-monotonically as the downstream fin moving toward the cavity ceiling, suggesting complex nonlinear characteristics. Compared to the scenario without any fin, the flow rate across the cavity is significantly boosted, which is increased by up to 136.2% at the early stage and 124.8% at the fully-developed stage. The heat transfer rate across the cavity having symmetrical fins on sidewalls is enhanced by up to 12.7% at a Rayleigh number of 3.68 × 109.
  • CFD analysis of convective heat transfer at the surfaces of a cube immersed in a turbulent boundary layer
    Item type: Journal Article
    Defraeye, Thijs; Blocken, Bert; Carmeliet, Jan (2010)
    International Journal of Heat and Mass Transfer
  • Direct numerical simulation of the compression stroke under engine relevant conditions: Evolution of the velocity and thermal boundary layers
    Item type: Journal Article
    Schmitt, Martin; Frouzakis, Christos E.; Wright, Yuri M.; et al. (2015)
    International Journal of Heat and Mass Transfer
  • Numerical analysis of convective drying of gypsum boards
    Item type: Journal Article
    Defraeye, Thijs; Houvenaghel, Geert; Carmeliet, Jan; et al. (2012)
    International Journal of Heat and Mass Transfer
  • The role of shadowed droplets in condensation heat transfer
    Item type: Journal Article
    Memos, George; Kokkoris, George; Constantoudis, Vassilios; et al. (2022)
    International Journal of Heat and Mass Transfer
    Dropwise condensation (DWC) is a phenomenon of common occurrence and significant utility in nature and technology. In energy applications, sustenance of DWC and avoidance of transition to film formation is directly related to efficient heat removal, ensuring high performance of related devices and processes. The efficiency of heat transfer in DWC depends on the heat transfer rates of individual droplets and the droplet size distribution. While the former can be summarily captured in engineering analysis through thermal resistance modeling, the theoretical analysis of the droplet size distribution involves assumptions often oversimplifying the complexity of droplet interactions, especially in the important sub–10 μm regime. Here, a modeling framework based on the thermal resistance approach is coupled with a dynamic model of droplet interactions: Droplet growth, coalescence, jumping, and removal of condensate due to gravity are all present during the unfolding of the phenomenon to accurately predict the droplet size distribution. The motivation is condensation experiments on superhydrophobic surfaces, namely rough aluminum substrates with a hydrophobic coating. Through the “interaction” of computations with measurements, the experimental findings are explained and critical parameters for condensation heat transfer on superhydrophobic surfaces are illuminated. Although larger droplets can be easily observed in experiments, it is shown that large droplets do not significantly affect heat transfer after reaching such state of growth. Instead, it is the small (with radius < 10 μm) and what we term “shadowed” droplets, i.e., the droplets grown in the shadow of the vertical projection area of the larger droplets, that play an important role in the heat transfer process. Due to the growth of these droplets and their concomitant shadowed coalescence and ensuing re-nucleation, the shift in the droplet size distribution towards smaller sizes is significant-enough to render the heat transfer rate rather insensitive to the presence of large droplets. In this regime, the effect of contact angle hysteresis on heat transfer is not crucial. Through the comparison with measurements, the dominant role of the density of nucleation sites on heat transfer is revealed and an estimation of the density of sites (∼105 mm−2) as a function of subcooling is extracted. Finally, the distribution of sites is found critical for heat transfer; an ordered distribution of sites outperforms random and clustered distributions.
  • Reticulated porous ceria undergoing thermochemical reduction with high-flux irradiation
    Item type: Journal Article
    Ackermann, Simon; Takacs, Michael; Scheffe, Jonathan; et al. (2017)
    International Journal of Heat and Mass Transfer
    A numerical and experimental analysis is performed on the solar-driven thermochemical reduction of ceria as part of a H2O/CO2-splitting redox cycle. A transient heat and mass transfer model is developed to simulate reticulated porous ceramic (RPC) foam-type structures, made of ceria, exposed to concentrated solar radiation. The RPC features dual-scale porosity in the mm-range and μm-range within its struts for enhanced transport. The numerical model solves the volume-averaged conservation equations for the porous fluid and solid domains using the effective transport properties for conductive, convective and radiative heat transfer. These in turn are determined by direct pore-level simulations and Monte-Carlo ray tracing on the exact 3D digital geometry of the RPC obtained from tomography scans. Experimental validation is accomplished in terms of temporal temperature and oxygen concentration measurements for RPC samples directly irradiated in a high-flux solar simulator with a peak flux of 1200 suns and heated to up to 1940 K. Effective volumetric absorption of solar radiation was obtained for moderate optically thick structures, leading to a more uniform temperature distribution and a higher specific oxygen yield. The effect of changing structural parameters such as mean pore diameter and porosity is investigated.
  • Suppression of nucleate boiling in upward two-phase annular flow: A direct measurement using modern diagnostics
    Item type: Journal Article
    Su, Guan-Yu; D'Aleo, Francesco P.; Phillips, Bren; et al. (2020)
    International Journal of Heat and Mass Transfer
    © 2020 Elsevier Ltd In heat exchangers employing flow boiling, e.g., boiling water reactors and industrial boilers, the heat transfer mechanism will transition from nucleate boiling to forced convective evaporation as the flow pattern transition from bubbly to annular flow at relatively high steam quality. Such thermal transition is called suppression of nucleate boiling (SNB). The occurrence of SNB affects the local heat transfer coefficient, the stability of liquid film, as well as the characteristics of entrained liquid droplets in the gas core. Despite its importance, there has been hitherto few direct measurements of the SNB conditions. Furthermore, the existing prediction approaches of SNB are only approximate, since they are based on extrapolation of empirical heat transfer correlations valid for nucleate boiling and forced convective evaporation regimes, rather than SNB mechanism. The objective of this study is to, experimentally and theoretically, fill the gap in understanding SNB phenomenon, using a modern set of diagnostics and a semi-empirical modeling approach. We leveraged synchronized infrared thermometry and an electrical conductance-based liquid film thickness sensor to investigate the details of the SNB phenomenon with high spatial and temporal resolutions. Such advanced diagnostics measure two crucial boundary conditions for SNB, i.e., the distribution of the temperature and heat flux on the heated wall, as well as the thickness of the liquid film. Such direct measurement revealed a clear dependency of SNB heat flux and wall superheat on both steam quality and mass flux. The experimental database has informed a more accurate semi-empirical model for predicting the SNB condition.
  • Stomatal transpiration and droplet evaporation on leaf surfaces by a microscale modelling approach
    Item type: Journal Article
    Defraeye, T.; Verboven, P.; Derome, D.; et al. (2013)
    International Journal of Heat and Mass Transfer
  • Efficiency of optimized bifurcating tree-like and parallel microchannel networks in the cooling of electronics
    Item type: Journal Article
    Escher, W.; Michel, B.; Poulikakos, D. (2009)
    International Journal of Heat and Mass Transfer
  • Heat transfer characteristics of urea-water spray impingement on hot surfaces
    Item type: Journal Article
    Liao, Yujun; Dimopoulos Eggenschwiler, Panayotis; Furrer, Roman; et al. (2018)
    International Journal of Heat and Mass Transfer
Publications1 - 10 of 94