Complex interfacial flows with heat transfer: Analysis, direct numerical simulations and experiments

Lead Research Organisation: Imperial College London
Department Name: Department of Chemical Engineering

Abstract

Multiphase flows often play a central role in engineering and have numerous practical applications. The proposed research focuses on free-surface thin-film flows over heated substrates. Such flows are part of the general class of interfacial flows which involve such diverse effects as dispersion and nonlinearity,
dissipation and energy accumulation, two- and three-dimensional phenomena and hence they are of great fundamental significance. Film dynamics and stability are governed by the effects of gravity, inertia, capillarity, thermocapillarity, viscosity, as well as surface topology and conditions. The thermocapillary forces give rise to an important surface phenomenon known as the Marangoni effect, in which variations in surface tension due to temperature result in liquid flow. The Marangoni effect leads to film deformation, driving it to rise locally and thus to generate instabilities that lead eventually to the formation of wave structures. In low-Reynolds (Re)-numbers heated falling films the thermocapillary forces are in competition with those of gravity and viscosity. In shear-driven horizontal flows, gravity is absent and the driving force is that of viscous shear at the gas-liquid interface. At higher Re inertia begins to play an increasingly dominant role.

Film flows show great promise in terms of their heat exchange capabilities. We aspire to harness and extend this promise, which will allow step improvements to the performance and efficiency of a host of technologies and industrial applications that rely crucially on film flows. This proposal seeks funding for a comprehensive three-year research programme into a three-pronged novel experimental, theoretical and numerical investigation aimed at rationally understanding and systematically predicting the hydrodynamic characteristics of liquid films flowing over heated surfaces, and furthermore, how these characteristics control the heat transfer potential of the corresponding flows. The proposal aims to answer these questions, with the goal of being able to accurately and efficiently predict complex physical behaviour in
heated film flows. We focus specifically on two paradigm flows: gravity-driven falling films and gas-driven horizontal films. The analytical work will be complemented by detailed numerical simulations that will act to verify the efficacy of the developed flow models while both analysis and computations will be contrasted with advanced experiments. The work will be undertaken by a team from the Chemical and Mechanical Engineering Departments at Imperial College London with complementary skills and strengths: Kalliadasis (Analysis--Theory), Markides (Experimental Fluid Mechanics) and van Wachem (Multiphase Flow Modelling--Computations).

Planned Impact

In addition to the academic impact described earlier, the following types of impact are envisaged:

Society--economy: Providing physical insight in thin-film flows with heat transfer and the appropriate modelling/predictive tools for such systems would allow researchers and engineers, whose technological processes involve at some stage such flows, to tackle classes of problems that have been inaccessible to them so far. There is also a wide spectrum of applications from traditional industries, such as chemical plants and nuclear industry to rapidly growing areas such as microfluidics and MEMS. The computational tools will be of benefit to the control and optimisation of technological processes that exploit thin-film flows as they would allow their rapid design or the designer surfaces for targetted heat transfer applications.

Industrial links--interaction with industry: We participate in a number of industrial, economic and decision-making networks and groupings, all of which could serve as vehicles to facilitate the wider impact of the research and to ensure that it is channeled towards the appropriate applications. Furthermore, we place great emphasis on the interactions between the project and the industrial collaborations. Direct knowledge exchange between the academic and industrial partners is planned while the research outputs will be used directly to allow successful development of new technological concepts and ideas.

Human resources: The project will offer an excellent training opportunity of the PDRAs it will employ. Indeed, training will take place in a highly cross-disciplinary context at the cross-road between applied mathematics, fluid dynamics and computational engineering/physics. This in turn will increase the specialist knowledge of the UK at the interface of these areas.

Publications

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Charogiannis A (2016) Thermographic particle velocimetry (TPV) for simultaneous interfacial temperature and velocity measurements in International Journal of Heat and Mass Transfer

 
Description Improved protocols for high-effectiveness micro-processor cooling schemes and improved heat exchanger designs.
First Year Of Impact 2013
Sector Chemicals,Electronics,Energy,Manufacturing, including Industrial Biotechology
Impact Types Economic

 
Description Africa Capacity Building Initiative
Amount £1,017,430 (GBP)
Funding ID AQ150077 
Organisation The Royal Society 
Sector Charity/Non Profit
Country United Kingdom
Start 01/2016 
End 01/2021
 
Title Experimental facility for the investigation of falling films via advanced optical diagnostic methods 
Description An experimental facility is used to establish falling films over a flat plate. The facility has been design to allow the investigation of different phenomena (e.g., fluid dynamics or heat transfer related) such as: (i) the test section can be positioned at an arbitrary angle, including negative angles; (ii) the length of the test section can be varied; (iii) the test section can be heated either over the entire area or locally, (iv) the flow can be pulsed in order to stimulate the formation of interfacial instabilities. 
Type Of Material Improvements to research infrastructure 
Year Produced 2015 
Provided To Others? Yes  
Impact - A new velocimetry technique has been developed on the facility, namely Thermographic Particle Velocimetry. 
 
Title New models and computational tools for interfacial flows with heat transfer 
Description We developed new low-dimensional models for complex interfacial flows with heat transfer using appropriate perturbation techniques and by taking into account heat transfer in the supporting wall (thus scrutinising the full conjugate heat transfer problem). We also developed new computational methodologies for interfacial flows with heat transfer based on the volume-of-fluid method allowing us to solve the full governing equations (Navier-Stokes-Fourier) with the appropriate wall and free-surface boundary conditions. 
Type Of Material Improvements to research infrastructure 
Provided To Others? No  
Impact The research provided both physical insight in thin flows with heat transfer and the appropriate modelling/predictive tools for such systems. The theoretical-computational tools developed as part of this project are of benefit to the control and optimisation of processes that exploit thin-film flows as theyallow their rapid design or designer surfaces for targeted heat transfer applications. This is in addition to the academic impact upon each subject and topic. 
URL http://www.imperial.ac.uk/complex-multiscale-systems
 
Title Thermographic Particle Velocimetry for simultaneous interfacial temperature and velocity field measurements 
Description Novel experimental technique which is capable of the simultaneous measurement of two-dimensional (2-D) surface temperature and velocity at the interface of multiphase flows (e.g., gas-liquid). This technique can be applied for the recovery of 2-D temperature and velocity field information at the interface of any flow with a sufficient density gradient between the two fluid phases. The technique relies on a single infrared imager (IR) and is based on the employment of highly reflective particles (in IR wavelengths) which can be distinguished from the surrounding fluid domain due to their different emissivity. The processing is based on the decomposition of the raw IR images into separate thermal and particle images. The velocity fields are then calculated using standard Particle Image Velocimetry (PIV) based cross-correlation algorithms. 
Type Of Material Improvements to research infrastructure 
Year Produced 2016 
Provided To Others? Yes  
Impact The newly developed technique can be used together with already established ones to in detail study interfacial flows; such as falling films, various multiphase flows (e.g., slug, stratified, annular flow, etc), or on a large scale can be applied in civil engineering (e.g., rivers). These are of high importance in a number of industries, e.g., oil-and-gas (oil or water transport; distillation columns); chemical (sulfonation reactors); medical (flow of mucus through trachea) or urban and environmental planning (drainage systems; rivers). 
 
Title Computational methods for interfacial flows with heat transfer 
Description We developed an arsenal of computational tools using the volume-of-fluids method allowing us the direct numerical simulation (DNS) of interfacial flows with heat transfer, that is the numerical solution of the full Navier-Stokes-Fourier equations together with the associated wall and free-surface boundary conditions for such flows. 
Type Of Material Computer model/algorithm 
Provided To Others? No  
Impact The computational tools developed as part of this project is of benefit to the control and optimisation of processes that exploit thin-film flows as they allow their rapid design or designer surfaces for targeted heat transfer applications. This is in addition to the academic impact upon each subject and topic. For instance, prior to this project there were no previous systematic and efficient DNS studies of interfacial flows in the presence of complexities such as heat transfer. 
URL http://www.imperial.ac.uk/complex-multiscale-systems
 
Title Tvd Differencing On Three-Dimensional Unstructured Meshes With Monotonicity-Preserving Correction Of Mesh Skewness (Accompanying Data) 
Description This data set contains the data accompanying the article F. Denner and B. van Wachem, TVD differencing on three-dimensional unstructured meshes with monotonicity-preserving correction of mesh skewness, Journal of Computational Physics (2015), http://dx.doi.org/10.1016/j.jcp.2015.06.008. 
Type Of Material Database/Collection of data 
Year Produced 2015 
Provided To Others? Yes  
 
Description Collaboration with Alfa Laval 
Organisation Alfa Laval AB
Country Sweden 
Sector Private 
PI Contribution One of the model systems we looked at during the tenure of the project, a film flowing down an inclined heated substrate, is pertinent to heat exchanger design, of particular interest to Alfa Laval.
Collaborator Contribution Alfa Laval focuses on heat exchangers and related products and solutions. Our research programme was of direct interest to Alfa Laval as it had the potential to improve their knowledge of heat transfer of thin interfacial flows. Alfa Laval was given the chance to shape our proposal but also provided feedback in our theoretical-computational and experimental developments by providing advice in relation to potential applications and by pointing out the gaps in current industrial knowledge know-how and by suggesting areas for further improvement. They also provided us with prototypes of patterned heat exchangers surfaces for us to test (part of our project dealt with film flows over heated microstructured substrates).
Impact Development of improved protocols for heat exchanger designs.
Start Year 2013
 
Description Collaboration with TTP 
Organisation TTPCom Ltd
Country United Kingdom 
Sector Private 
PI Contribution One of the model systems we looked at as part of the project was the gas-/shear-driven horizontal film flow on a locally heated substrate. This model is pertinent to small-scale electronics-microprocessor cooling schemes, of particular interest to TTP.
Collaborator Contribution The contribution of TTP consisted in providing us with information on their advanced thermal management projects they work, in particular in relation to technology development of high-effectiveness micro-processor cooling schemes. But also advice apropos our theoretical-computational developments during project review meetings we held with industrial sponsors.
Impact Development of improvement protocols for micro-processor cooling schemes.
Start Year 2013