scholarly journals Boiling heat transfer modelling: A review and future prospectus

2019 ◽  
Vol 23 (1) ◽  
pp. 87-107 ◽  
Author(s):  
Milica Ilic ◽  
Milan Petrovic ◽  
Vladimir Stevanovic
Keyword(s):  
Heat Transfer ◽  
Boiling Heat Transfer ◽  
Practical Significance ◽  
Current Status ◽  
Small Scale ◽  
Multi Scale ◽  
Road Map ◽  
Macro Scale ◽  
Transfer Modelling ◽  
Individual Scale

This paper reviews the current status of boiling heat transfer modelling, discusses the need for its improvement due to unresolved intriguing experimental findings and emergence of novel technical applications and outlines the directions for an advanced modelling approach. The state-of-the-art of computational boiling heat transfer studies is given for: macro-scale boiling models applied in two-fluid liquid-vapour interpenetrating media approach, micro-, meso-scale boiling computations by interface capturing methods, and nano-scale boiling simulations by molecular dynamics tools. Advantages, limitations and shortcomings of each approach, which originate from its grounding formulations, are discussed and illustrated on results obtained by the boiling model developed in our research group. Based on these issues, we stress the importance of adaptation of a multi-scale approach for development of an advanced boiling predictive methodology. A general road-map is outlined for achieving this challenging goal, which should include: improvement of existing methods for computation of boiling on different scales and development of conceptually new algorithms for linking of individual scale methods. As dramatically different time steps of integration for different boiling scales hinder the application of full multi-scale methodology on boiling problems of practical significance, we emphasise the importance of development of another algorithm for the determination of sub-domains within a macro-scale boiling region, which are relevant for conductance of small-scale simulations.

Pool Boiling Heat Transfer From Plain and Microporous, Square Pin Finned Surfaces in Saturated FC-72

1999 ◽  
Author(s):  
K. N. Rainey ◽  
S. M. You
Keyword(s):  
Heat Transfer ◽  
Boiling Heat Transfer ◽  
Large Scale ◽  
Pool Boiling ◽  
Nucleate Boiling ◽  
Small Scale ◽  
Surface Microstructure ◽  
Transfer Coefficients ◽  
Microporous Coating ◽  
Nucleate Boiling Heat Transfer

Abstract The present research is an experimental study of “double enhancement” behavior in pool boiling from heater surfaces simulating microelectronic devices immersed in saturated FC-72 at atmospheric pressure. The term “double enhancement” refers to the combination of two different enhancement techniques: a large-scale area enhancement (square pin fin array) and a small-scale surface enhancement (microporous coating). Fin lengths were varied from 0 (flat surface) to 8 mm. Effects of this double enhancement technique on critical heat flux (CHF) and nucleate boiling heat transfer in the horizontal orientation (fins are vertical) are investigated. Results showed significant increases in nucleate boiling heat transfer coefficients with the application of the microporous coating to the heater surfaces. CHF was found to be relatively insensitive to surface microstructure for the finned surfaces except in the case of the surface with 8 mm long fins. The nucleate boiling and CHF behavior has been found to be the result of multiple, counteracting mechanisms: surface area enhancement, fin efficiency, surface microstructure (active nucleation site density), vapor bubble departure resistance, and re-wetting liquid flow resistance.

scholarly journals Multi-Scale CFD Modeling of Plate Heat Exchangers Including Offset-Strip Fins and Dimple-Type Turbulators for Automotive Applications

Energies ◽  
2019 ◽  
Vol 12 (15) ◽  
pp. 2965 ◽  
Author(s):  
Augusto Della Torre ◽  
Gianluca Montenegro ◽  
Angelo Onorati ◽  
Sumit Khadilkar ◽  
Roberto Icarelli
Keyword(s):  
Heat Transfer ◽  
Fluid Dynamics ◽  
Heat Exchangers ◽  
Internal Combustion Engines ◽  
Cfd Simulation ◽  
Full Scale ◽  
Operating Conditions ◽  
Plate Heat ◽  
Multi Scale ◽  
Macro Scale

Plate heat exchangers including offset-strip fins or dimple-type turbulators have a wide application in the automotive field as oil coolers for internal combustion engines and transmissions. Their optimization is a complex task since it requires targeting different objectives: High compactness, low pressure drop and high heat-transfer efficiency. In this context, the availability of accurate Computational Fluid Dynamics (CFD) simulation models plays an important role during the design phase. In this work, the development of a computational framework for the CFD simulation of compact oil-to-liquid heat exchangers, including offset-strip fins and dimples, is presented. The paper addresses the modeling problem at different scales, ranging from the characteristic size of the turbulator geometry (typically µm–mm) to the full scale of the overall device (typically cm–dm). The simulation framework is based on multi-scale concept, which applies: (a) Detailed simulations for the characterization of the micro-scale properties of the turbulator, (b) an upscaling approach to derive suitable macro-scale models for the turbulators and (c) full-scale simulations of the entire cooler, including the porous models derived for the smaller scales. The model is validated comparing with experimental data under different operating conditions. Then, it is adopted to investigate the details of the fluid dynamics and heat-transfer process, providing guidelines for the optimization of the device.

Strain-weakening rheology in Earth’s lower mantle: a multi-scale numerical endeavour

2020 ◽  
Author(s):  
Gregor J. Golabek ◽  
Anna J. P. Gülcher ◽  
Marcel Thielmann ◽  
Paul J. Tackley ◽  
Maxim D. Ballmer
Keyword(s):  
Lower Mantle ◽  
Mantle Convection ◽  
Numerical Models ◽  
Order Effect ◽  
Small Scale ◽  
Localized Deformation ◽  
Earth Planet ◽  
Multi Scale ◽  
Macro Scale ◽  
Heterogeneous Rocks

<p>Rocks in the Earth’s interior are not homogeneous but consist of different mineralogical phases with different rheological properties. Deformation of heterogeneous rocks is thus also heterogeneous, and strongly depends on the rheological contrasts and spatial distribution of the mineral phases. In Earth’s lower mantle, the main rock constituents are bridgmanite (Br) and smaller amounts of ferropericlase (Fp). Bridgmanite is substantially stronger than ferropericlase [1]. Recent studies propose that lower mantle rheology is highly dependent on the relative mineral abundances and distribution of these two phases [1,2]. It has been suggested that for bridgmanite-depleted compositions, the viscosity decreases with accumulating strain due to the interconnection of the weaker ferropericlase. This implies that deformation may localize in the lower mantle, potentially aiding the formation and preservation of compositionally distinct and “hidden” reservoirs away from these regions of localized deformation [3]. Therefore, understanding the rheological nature of Br-Fp aggregates on a small-scale is crucial for assessing the dynamics of global mantle convection. Here, we address this objective with multi-scale numerical approaches.  </p><p>Using a numerical-statistical approach, a connection between ferropericlase morphology and effective rheology of Earth’s lower mantle has recently been established [4]. Results show that bulk-rock weakening depends on the topology of the weak phase as well on its rheology, but also that significant rheological weakening can already be achieved when ferropericlase does not (yet) form an interconnected weak layer.</p><p>In a second suite of models, we implement a macro-scale description of strain-weakening based on the micro-scale solutions found in [4] in a global mantle convection model to test the first-order effect of strain weakening on convection dynamics in the lower mantle. We present 2D numerical models of thermochemical convection in a spherical annulus geometry [5] that include a new implementation of tracking the strain ellipse at each tracer through time. We further allow lower mantle materials to rheologically weaken once a certain strain threshold has been reached. Preliminary results indicate that strain localizes along both up- and downwellings in the lower mantle and that rheological weakening has a stabilizing effect on these conduits. </p><p>This multi-scale approach is essential for addressing lower-mantle rheological behavior and our results form an important step towards addressing the feasibility of isolated, long-lived geochemical reservoirs in Earth’s lower mantle.</p><p>[1] Yamazaki and Karato (2001), Am. Mineral. 86, 385-391. [2] Girard et al. (2016), Science 351, 144-147. [3] Ballmer et al. (2017), Nat. Geosci. 10, 236-240. [4] Thielmann et al. (2020), Geochem. Geophys. Geosyst., doi:10.1029/2019GC008688. [5] Hernlund and Tackley (2008), Phys. Earth Planet. Int. 171, 48–54.</p>

scholarly journals Multi-scale heat and mass transfer modelling of cell and tissue cryopreservation

2010 ◽  
Vol 368 (1912) ◽  
pp. 561-583 ◽  
Author(s):  
Feng Xu ◽  
Sangjun Moon ◽  
Xiaohui Zhang ◽  
Lei Shao ◽  
Young Seok Song ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Mass Transport ◽  
Volume Change ◽  
Physical Processes ◽  
New Techniques ◽  
Multi Scale ◽  
Transfer Modelling ◽  
Physical Phenomena ◽  
Tissue Cryopreservation

Cells and tissues undergo complex physical processes during cryopreservation. Understanding the underlying physical phenomena is critical to improve current cryopreservation methods and to develop new techniques. Here, we describe multi-scale approaches for modelling cell and tissue cryopreservation including heat transfer at macroscale level, crystallization, cell volume change and mass transport across cell membranes at microscale level. These multi-scale approaches allow us to study cell and tissue cryopreservation.

Nano-Engineered Surfaces With Heterogeneous Wettability for Boiling Heat Transfer Enhancement

2011 ◽  
Author(s):  
Amy Rachel Betz ◽  
James Jenkins ◽  
Chang-Jin C. J. Kim ◽  
Daniel Attinger
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Boiling Heat Transfer ◽  
Transfer Enhancement ◽  
Sio2 Surface ◽  
Multi Scale ◽  
Engineered Surfaces ◽  
The Heat Transfer Coefficient

In this work we describe the manufacturing and characterization of multi-scale patterned heterogeneous wettability surfaces. We find drastic enhancements of the pool boiling performance in water. Compared to a hydrophilic SiO2 surface with a wetting angle of 7°, we find that surfaces combining superhydrophilic and superhydrophobic patterns can increase the heat transfer coefficient (HTC) by 300% and can increase the critical heat flux (CHF) by more than 100%.

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