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Pietro Asinari

Politecnico di Torino, Energy Department, Faculty Member

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Pietro Asinari is Full Professor of heat and mass transfer and Director of the Multiscale Modeling Laboratory (SMaLL, https://www.polito.it/small) at the Politecnico di Torino. He graduated with honors in Mechanical Engineering in 2001 and received his PhD in Energy Engineering in 2005, winning the ENI-Italgas award for Energy and the Environment. He is a member of the Management Committee of the European Council for Material Modeling (EMMC, https://emmc.info). He is an international member of the Advisory Committee of the American OpenKIM project (https://openkim.org) for interatomic models. He is a member of the Executive Committee of the Italian Union of Thermo-fluid dynamics (UIT). He is a member of the editorial board of the journal Heliyon (Elsevier) since 2016. He is responsible for numerous European (eight projects in H2020) and national projects. His research lies in the field of energy and environmental sustainability, in particular regarding the use of renewable sources for the production of drinking water, the heat and mass transfer in energy devices, and the modeling of materials. He has published more than 100 articles in international journals, including Nature Sustainability and Nature Communications.

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Papers by Pietro Asinari

Machine learning and materials modelling interpretation of in vivo toxicological response to TiO2 nanoparticles library (UV and non-UV exposure)

Nanoscale, 2021

Based on a highly detailed materials characterisation database (including atomistic and multiscal... more

Atomistic modelling of water transport and adsorption mechanisms in silicoaluminophosphate for thermal energy storage

Applied Thermal Engineering, 2019

SAPO-34-a silicoaluminophosphate microporous material-has recently attracted a great attention in... more SAPO-34-a silicoaluminophosphate microporous material-has recently attracted a great attention in the field of sorption thermal storage, since it is characterized by good water adsorption behavior (i.e. type V adsorption isotherms) and low regeneration temperature (i.e. 80°C, for instance available by standard solar thermal energy collectors). However, the nanoscale mechanisms of water transport and adsorption in the microporous framework of SAPO-34 cannot be fully unveiled by experiments alone. In this work, water adsorption onto SAPO-34 is for the first time studied by means of an atomistic model built upon experimental evidence. First, Monte Carlo simulations are employed to set up a convenient atomistic model of water/SAPO-34 non-bonded interactions, and numerical adsorption isotherms are validated against experimental measures. Second, the validated model is used to study the water diffusion through SAPO-34 by Molecular Dynamics simulations, and to visualize preferential adsorption sites with atomistic detail. Such atomistic model validated against experiments may ease the investigation and in silico discovery of silicoaluminophosphates for thermal storage applications with tailored adsorption characteristics.

Multistage and passive cooling process driven by salinity difference

Science Advances, 2020

Net cooling flux and temperature difference shown in a static machine only driven by salty water ... more

Wettability of soft PLGA surfaces predicted by experimentally augmented atomistic models

MRS Bulletin

A challenging topic in surface engineering is predicting the wetting properties of soft interface... more A challenging topic in surface engineering is predicting the wetting properties of soft interfaces with different liquids. However, a robust computational protocol suitable for predicting wettability with molecular precision is still lacking. In this article, we propose a workflow based on molecular dynamics simulations to predict the wettability of polymer surfaces and test it against the experimental contact angle of several polar and nonpolar liquids, namely water, formamide, toluene, and hexane. The specific case study addressed here focuses on a poly(lactic-co-glycolic acid) (PLGA) flat surface, but the proposed experimental-modeling protocol may have broader fields of application. The structural properties of PLGA slabs have been modeled on the surface roughness determined with microscopy measurements, while the computed surface tensions and contact angles were validated against standardized characterization tests, reaching a discrepancy of less than 3% in the case of water. O...

A Roadmap for Transforming Research to Invent the Batteries of the Future Designed within the European Large Scale Research Initiative BATTERY 2030+

Advanced Energy Materials, 2022

Figure 11. AI-driven design and manufacturing methodologies linked together as a whole.

Spreading of Impacting Droplets on Wettability-Patterned Surfaces

Bulletin of the American Physical Society, 2016

at Chicago-Droplet collision on solid surfaces is a long-studied field that has focused mostly on... more at Chicago-Droplet collision on solid surfaces is a long-studied field that has focused mostly on droplets striking uniform-wettability surfaces. As of now, very few studies exist that analyzed droplet impact on non-uniform (spatially) wettability surfaces. More importantly, no model exists for predicting droplet impact behavior on spatially non-uniform surfaces. Using photolithograhically-produced surfaces, we study droplet impact on axially-symmetric, non-uniform wettability surfaces. We expand upon previously presented models for uniform-wettability surfaces, and predict the maximum spreading diameter of droplets impacting on symmetric patterns on varying wettability surfaces. The present model is expanded to account for n annular regions of different wettabilities, and calculate the corresponding maximum spreading diameter. In addition, within the model we explore the concept of a wettability contrast barrier that must be overcome by the impacting droplets in order to continue their spreading phase. We show under which conditions a droplet can successfully overcome this barrier, and under which conditions it cannot. The model put forth makes strong use of the previously-reported droplet impact model of Passandideh-Fard et al. It draws upon geometric assumptions, such as cylindrical shape for the expanding liquid and spherical cap for the impacting droplet. The work is fundamental in nature, but offers valuable insight that helps understand droplet impact dynamics on non-uniform wettability surfaces.

A Modeling-Based Design to Engineering Protein Hydrogels with Random Copolymers

ACS Nano, 2021

Protein enzymes have shown great potential in numerous technological applications. However, the d... more Protein enzymes have shown great potential in numerous technological applications. However, the design of supporting materials is needed to preserve protein functionality outside their native environment. Direct enzyme-polymer self-assembly offers a promising alternative to immobilize proteins in an aqueous solution, achieving higher control of their stability and enzymatic activity in industrial applications. Herein, we propose a modeling-based design to engineering hydrogels of cytochrome P450 and of PETase with styrene/2-vinylpyridine (2VP) random copolymers. By tuning the copolymer fraction of polar groups and of charged groups via quaternization of 2VP for coassembly with cytochrome P450 and via sulfonation of styrene for coassembly with PETase, we provide quantitative guidelines to select either a protein-polymer hydrogel structure or a single-protein encapsulation. The results highlight that, regardless of the protein surface domains, the presence of polar interactions and hydration effects promote the formation of a more elongated enzyme-polymer complex, suggesting a membrane-like coassembly. On the other hand, the effectiveness of a single-protein encapsulation is reached by decreasing the fraction of polar groups and by increasing the charge fraction up to 15%. Our computational analysis demonstrates that the enzyme-polymer assemblies are first promoted by the hydrophobic interactions which lead the protein nonpolar residues to achieve the maximum coverage and to play the role of the most robust contact points. The mechanisms of coassembly are unveiled in the light of both protein and polymer physical-chemistry, providing bioconjugate phase diagrams for the optimal material design.

Sustainable polyethylene fabrics with engineered moisture transport for passive cooling

Nature Sustainability, 2021

Polyethylene (PE) has emerged recently as a promising polymer for incorporation in wearable texti... more Polyethylene (PE) has emerged recently as a promising polymer for incorporation in wearable textiles owing to its high infrared transparency and tuneable visible opacity, which allows the human body to cool via thermal radiation, potentially saving energy on building refrigeration. Here, we show that single-material PE fabrics may offer a sustainable, high-performance alternative to conventional textiles, extending beyond radiative cooling. PE fabrics exhibit ultra-light weight, low material cost and recyclability. Industrial materials sustainability (Higg) index calculations predict a low environmental footprint for PE fabrics in the production phase. We engineered PE fibres, yarns and fabrics to achieve efficient water wicking and fast-drying performance which, combined with their excellent stain resistance, offer promise in reducing energy and water consumption as well as the environmental footprint of PE textiles in their use phase. Unlike previously explored nanoporous PE materials, the high-performance PE fabrics in this study are made from fibres melt spun and woven on standard equipment used by the textile industry worldwide and do not require any chemical coatings. We further demonstrate that these PE fibres can be dry coloured during fabrication, resulting in dramatic water savings without masking the PE molecular fingerprints scanned during the automated recycling process. The textile industry is one of the largest polluters. Here the authors show that polyethylene is a sustainable alternative textile with water wicking and fast-drying performance. The fabrication of polyethylene fabrics is compatible with standard equipment and could be dry-coloured, further reducing water consumption.

Sustainable freshwater production using passive membrane distillation and waste heat recovery from portable generator sets

Applied Energy, 2020

Abstract More than two billion people live in areas affected by water stress. In some coastal reg... more Abstract More than two billion people live in areas affected by water stress. In some coastal regions, freshwater supply has been progressively improved by large-scale desalination systems, which are nowadays mostly driven by non-renewable energy sources. Here we discuss, and experimentally investigate, the use of small-scale desalination devices for freshwater production powered by waste heat from electric power generators. The water purification technology relies on a passive, multi-stage and thermally-driven membrane distillation device, recently proposed by some of the authors of this work. The distiller is powered by low-grade (temperature lower than 80 °C) waste heat, recovered from the coolant circuit of small diesel engines for electricity production. Field experiments show that, for the tested engine, up to 1.12  kW m - 2 can be recovered in standard operating conditions, which yield a nearly 2.61  L m - 2 h - 1 freshwater production from seawater. A lumped parameter model, validated by experiments, shows that this productivity could be eventually enhanced by tuning the number of distillation stages. Utilization with exhaust gases, and thus higher feeding working temperatures, is also discussed. The proposed solution may provide a sustainable, simple, inexpensive and efficient means for freshwater production from recovered waste heat, which would otherwise be wasted to the ambient. Therefore it could be particularly effective, for instance, for field hospitals in remote or impoverished areas, especially in emergency situations.

Integrated receivers with bottom subcooling for automotive air conditioning: detailed experimental study of their filling capacity

International Journal of Refrigeration, 2016

The use of the integrated receiver in condensers for common automotive air conditioning-A/C-syste... more The use of the integrated receiver in condensers for common automotive air conditioning-A/C-systems is widespread, because of its thermodynamic and operational advantages. Many studies have been already conducted on estimating the effect of the subcooling value. However, this study aims at determining the most important factors affecting the length of the refrigerant stable operating plateau and how the receiver filling is affected by geometrical and thermodynamic boundary conditions, by means of an experimental campaign built using design of experiments-DOE-techniques. Results demonstrate how the receiver diameter and the axle spacing between its inlet and outlet holes have the highest influence on the receiver operation. Finally, these results have been used to set up a numerical model able to accurately estimate the filling efficiency of the integrated receiver, in terms of volume of the operating plateau compared to the net available receiver volume.

Thermal fluid dynamic analysis in compact shell & tube heat exchangers for industrial applications

Compact fin&tube heat exchangers are employed in a wide range of engineering applications. Despit... more Compact fin&tube heat exchangers are employed in a wide range of engineering applications. Despite these components have by now been largely studied and the literature on the topic is huge, the interest on their numerical analysis and optimization is always actual. Furthermore, the continuous effort in the development of more and more sophisticated CFD tools, together with the increasing computational resource available (i.e. cluster facilities), contributes to maintain an interest on the numerical simulation and analysis of these components. The present work deals with the thermal fluid dynamic analysis of an industrial gas cooler by means of the commercial CFD solver ANSYS Fluent. The attention is firstly focused on the detailed analysis of the finned pack. The in-pack conditions are studied taking advantage of the symmetries of the domain. Different fin layouts are taken into consideration, in order to understand the effects of the geometrical features on the heat transfer coeffi...

Influence of Porous Electrode Structure on PEM Fuel Cells Design and Performance

2nd International Conference on Fuel Cell Science, Engineering and Technology, 2004

Gas flow in fuel cell porous electrodes is usually modelled with Darcy’s law, which requires the ... more Gas flow in fuel cell porous electrodes is usually modelled with Darcy’s law, which requires the definition of a resistance constant for the material. This can be done directly via experimentation or indirectly via numerical tuning to fit experimental data on cell behaviour. Both methods lack generality, as they do not take into account the particular porous structure of each electrode. In the present work, a numerical procedure for calculating the resistance constant for a given porous structure is presented. This procedure is based on Lattice Boltzmann models, which treat the problem from a microscopic point of view, reproducing collisions between fluid molecules and solid particles. It can be demonstrated that under certain hypotheses, these models yield Navier-Stokes equations on a macroscopic scale, hence obeying fluid mechanics laws. Here the flow in a set of thirty randomly generated porous structures was analyzed, thus obtaining a distribution of values for Darcy’s constant....

CFD Modeling of Solar Collector with Nano-Fluid Direct Absorption for Civil Application

Direct solar absorption has been considered often in the past as a possible configuration of sola... more Direct solar absorption has been considered often in the past as a possible configuration of solar thermal collectors for residential and small commercial applications. Of course, a direct absorption could improve the performance of solar collectors by skipping one step of the heat transfer mechanism of standard devices and by modifying the temperature distribution inside the collector. In fact, classical solar thermal collectors have a metal sheet as absorber, designed such that water has the minimum temperature in each transversal section, in order to collect as much as possible the solar thermal energy. On the other hand, in a direct configuration, the hottest part of the system is the operating fluid and this allows to have a more efficient conversion. Nanofluids, i.e. fluids with a suspension of nano-particles, as carbon nano-horns, could be a good and innovative family of absorbing fluids, for their higher absorption coefficient with respect to the base fluid and stability under moderate temperature gradients. Moreover, carbon nanohorns offer the significant advantage to be non-toxic unlike other carbon nanoparticles (e.g. carbon nanotubes). In this work, an original 3D model of the absorption phenomena in nano-fluids flowing in a cylindrical tube is coupled with a CFD analysis of the flow and temperature field. Recent measurements of the optical properties of nano-fluids with different concentrations have been used for the radiation heat transfer modeling and included in the fluid dynamic modeling as well. Heat losses due to conduction, convection and radiation at the boundaries are included in the model. The results are compared with the typical performance of flat solar collectors present on the market.

Interfacial water thickness at inorganic nanoconstructs and biomolecules: Size matters

Physics Letters A, 2016

Water molecules in the proximity of solid nanostructures influence both the overall properties of... more Water molecules in the proximity of solid nanostructures influence both the overall properties of liquid and the structure and functionality of solid particles. The study of water dynamics at solid-liquid interfaces has strong implications in energy, environmental and biomedical fields. This article focuses on the hydration layer properties in the proximity of Carbon Nanotubes (CNTs) and biomolecules (proteins, polipeptides and amino acids). Here we show a quantitative relation between the solid surface extension and the characteristic length of water nanolayer (δ), which is confined at solid-liquid interfaces. Specifically, the size dependence is attributed to the limited superposition of nonbonded interactions in case of small molecules. These results may facilitate the design of novel energy or biomedical colloidal nanosuspensions, and a more fundamental understanding of biomolecular processes influenced by nanoscale water dynamics.

With Tunable Bulk Viscosity for Enhancing Stability

Taking advantage of a closed-form generalized Maxwell distribution function [P. Asinari and I.V. ... more Taking advantage of a closed-form generalized Maxwell distribution function [P. Asinari and I.V. Karlin, Phys. Rev. E 79, 036703 (2009)] and splitting the relaxation to the equilibrium in two steps, an entropic quasi-equilibrium (EQE) kinetic model is proposed for the simulation of low Mach number flows, which enjoys both the H-theorem and a free-tunable parameter for controlling the bulk viscosity in such a way as to enhance numerical stability in the incompressible flow limit. Moreover, the proposed model admits a simplification based on a proper expansion in the low Mach number limit (LQE model). The lattice Boltzmann implementation of both the EQE and LQE is as simple as that of the standard lattice Bhatnagar-Gross-Krook (LBGK) method, and practical details are reported. Extensive numerical testing with the lid driven cavity flow in two dimensions is presented in order to verify the enhancement of the stability region. The proposed models achieve the same accuracy as the LBGK method with much rougher meshes, leading to an effective computational speed-up of almost three times for EQE and of more than four times for the LQE. Three-dimensional extension of EQE and LQE is also discussed.

European Materials Modelling Council

The aim of the European Materials Modelling Council (EMMC) is to establish current and forward lo... more The aim of the European Materials Modelling Council (EMMC) is to establish current and forward looking complementary activities necessary to bring the field of materials modelling closer to the demands of manufacturers (both small and large enterprises) in Europe. The ultimate goal is that materials modelling and simulation will become an integral part of product life cycle management in European industry, thereby making a strong contribution to enhance innovation and competitiveness on a global level. Based on intensive efforts in the past two years within the EMMC, which included numerous consultation and networking actions with representatives of all stakeholders including Modellers, Software Owners, Translators and Manufacturers in Europe, the EMMC identified and proposed a set of underpinning and enabling actions to increase the industrial exploitation of materials modelling in Europe. EMMC will pursue the following overarching objectives in order to bridge the gap between acad...

Nonlinear Boltzmann equation for the homogeneous isotropic case: Minimal deterministic Matlab program

The homogeneous isotropic Boltzmann equation (HIBE) is a fundamental dynamic model for many appli... more The homogeneous isotropic Boltzmann equation (HIBE) is a fundamental dynamic model for many applications in thermodynamics, econophysics and sociodynamics. Despite recent hardware improvements, the solution of the Boltzmann equation remains extremely challenging from the computational point of view, in particular by deterministic methods (free of stochastic noise). This work aims to improve a deterministic direct method recently proposed [V.V. Aristov, Kluwer Academic Publishers, 2001] for solving the HIBE with a generic collisional kernel and, in particular, for taking care of the late dynamics of the relaxation towards the equilibrium. Essentially (a) the original problem is reformulated in terms of particle kinetic energy (exact particle number and energy conservation during microscopic collisions) and (b) the computation of the relaxation rates is improved by the DVM-like correction, where DVM stands for Discrete Velocity Model (ensuring that the macroscopic conservation laws ar...

Link-wise Artificial Compressibility Method

The Artificial Compressibility Method (ACM) for the incompressible Navier-Stokes equations is (li... more The Artificial Compressibility Method (ACM) for the incompressible Navier-Stokes equations is (link-wise) reformulated (referred to as LW-ACM) by a finite set of discrete directions (links) on a regular Cartesian mesh, in analogy with the Lattice Boltzmann Method (LBM). The main advantage is the possibility of exploiting well established technologies originally developed for LBM and classical computational fluid dynamics, with special emphasis on finite differences (at least in the present paper), at the cost of minor changes. For instance, wall boundaries not aligned with the background Cartesian mesh can be taken into account by tracing the intersections of each link with the wall (analogously to LBM technology). LW-ACM requires no high-order moments beyond hydrodynamics (often referred to as ghost moments) and no kinetic expansion. Like finite difference schemes, only standard Taylor expansion is needed for analyzing consistency. Preliminary efforts towards optimal implementation...

Integrated molecular dynamics and experimental approach to characterize low-free-energy perfluoro-decyl-acrylate (PFDA) coated silicon

Materials & Design, 2021

This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Unfolding the prospects of computational (bio)materials modeling

The Journal of Chemical Physics, 2020

In this perspective communication, we briefly sketch the current state of computational (bio)mate... more In this perspective communication, we briefly sketch the current state of computational (bio)material research and discuss possible solutions for the four challenges that have been increasingly identified within this community: (i) the desire to develop a unified framework for testing the consistency of implementation and physical accuracy for newly developed methodologies, (ii) the selection of a standard format that can deal with the diversity of simulation data and at the same time simplifies data storage, data exchange, and data reproduction, (iii) how to deal with the generation, storage, and analysis of massive data, and (iv) the benefits of efficient "core" engines. Expressed viewpoints are the result of discussions between computational stakeholders during a Lorentz center workshop with the prosaic title Workshop on Multi-scale Modeling and are aimed at (i) improving validation, reporting and reproducibility of computational results, (ii) improving data migration between simulation packages and with analysis tools, (iii) popularizing the use of coarse-grained and multi-scale computational tools among non-experts and opening up these modern computational developments to an extended user community.

Machine learning and materials modelling interpretation of in vivo toxicological response to TiO2 nanoparticles library (UV and non-UV exposure)

Nanoscale, 2021

Based on a highly detailed materials characterisation database (including atomistic and multiscal... more

Atomistic modelling of water transport and adsorption mechanisms in silicoaluminophosphate for thermal energy storage

Applied Thermal Engineering, 2019

SAPO-34-a silicoaluminophosphate microporous material-has recently attracted a great attention in... more SAPO-34-a silicoaluminophosphate microporous material-has recently attracted a great attention in the field of sorption thermal storage, since it is characterized by good water adsorption behavior (i.e. type V adsorption isotherms) and low regeneration temperature (i.e. 80°C, for instance available by standard solar thermal energy collectors). However, the nanoscale mechanisms of water transport and adsorption in the microporous framework of SAPO-34 cannot be fully unveiled by experiments alone. In this work, water adsorption onto SAPO-34 is for the first time studied by means of an atomistic model built upon experimental evidence. First, Monte Carlo simulations are employed to set up a convenient atomistic model of water/SAPO-34 non-bonded interactions, and numerical adsorption isotherms are validated against experimental measures. Second, the validated model is used to study the water diffusion through SAPO-34 by Molecular Dynamics simulations, and to visualize preferential adsorption sites with atomistic detail. Such atomistic model validated against experiments may ease the investigation and in silico discovery of silicoaluminophosphates for thermal storage applications with tailored adsorption characteristics.

Multistage and passive cooling process driven by salinity difference

Science Advances, 2020

Net cooling flux and temperature difference shown in a static machine only driven by salty water ... more

Wettability of soft PLGA surfaces predicted by experimentally augmented atomistic models

MRS Bulletin

A challenging topic in surface engineering is predicting the wetting properties of soft interface... more A challenging topic in surface engineering is predicting the wetting properties of soft interfaces with different liquids. However, a robust computational protocol suitable for predicting wettability with molecular precision is still lacking. In this article, we propose a workflow based on molecular dynamics simulations to predict the wettability of polymer surfaces and test it against the experimental contact angle of several polar and nonpolar liquids, namely water, formamide, toluene, and hexane. The specific case study addressed here focuses on a poly(lactic-co-glycolic acid) (PLGA) flat surface, but the proposed experimental-modeling protocol may have broader fields of application. The structural properties of PLGA slabs have been modeled on the surface roughness determined with microscopy measurements, while the computed surface tensions and contact angles were validated against standardized characterization tests, reaching a discrepancy of less than 3% in the case of water. O...

A Roadmap for Transforming Research to Invent the Batteries of the Future Designed within the European Large Scale Research Initiative BATTERY 2030+

Advanced Energy Materials, 2022

Figure 11. AI-driven design and manufacturing methodologies linked together as a whole.

Spreading of Impacting Droplets on Wettability-Patterned Surfaces

Bulletin of the American Physical Society, 2016

at Chicago-Droplet collision on solid surfaces is a long-studied field that has focused mostly on... more at Chicago-Droplet collision on solid surfaces is a long-studied field that has focused mostly on droplets striking uniform-wettability surfaces. As of now, very few studies exist that analyzed droplet impact on non-uniform (spatially) wettability surfaces. More importantly, no model exists for predicting droplet impact behavior on spatially non-uniform surfaces. Using photolithograhically-produced surfaces, we study droplet impact on axially-symmetric, non-uniform wettability surfaces. We expand upon previously presented models for uniform-wettability surfaces, and predict the maximum spreading diameter of droplets impacting on symmetric patterns on varying wettability surfaces. The present model is expanded to account for n annular regions of different wettabilities, and calculate the corresponding maximum spreading diameter. In addition, within the model we explore the concept of a wettability contrast barrier that must be overcome by the impacting droplets in order to continue their spreading phase. We show under which conditions a droplet can successfully overcome this barrier, and under which conditions it cannot. The model put forth makes strong use of the previously-reported droplet impact model of Passandideh-Fard et al. It draws upon geometric assumptions, such as cylindrical shape for the expanding liquid and spherical cap for the impacting droplet. The work is fundamental in nature, but offers valuable insight that helps understand droplet impact dynamics on non-uniform wettability surfaces.

A Modeling-Based Design to Engineering Protein Hydrogels with Random Copolymers

ACS Nano, 2021

Protein enzymes have shown great potential in numerous technological applications. However, the d... more Protein enzymes have shown great potential in numerous technological applications. However, the design of supporting materials is needed to preserve protein functionality outside their native environment. Direct enzyme-polymer self-assembly offers a promising alternative to immobilize proteins in an aqueous solution, achieving higher control of their stability and enzymatic activity in industrial applications. Herein, we propose a modeling-based design to engineering hydrogels of cytochrome P450 and of PETase with styrene/2-vinylpyridine (2VP) random copolymers. By tuning the copolymer fraction of polar groups and of charged groups via quaternization of 2VP for coassembly with cytochrome P450 and via sulfonation of styrene for coassembly with PETase, we provide quantitative guidelines to select either a protein-polymer hydrogel structure or a single-protein encapsulation. The results highlight that, regardless of the protein surface domains, the presence of polar interactions and hydration effects promote the formation of a more elongated enzyme-polymer complex, suggesting a membrane-like coassembly. On the other hand, the effectiveness of a single-protein encapsulation is reached by decreasing the fraction of polar groups and by increasing the charge fraction up to 15%. Our computational analysis demonstrates that the enzyme-polymer assemblies are first promoted by the hydrophobic interactions which lead the protein nonpolar residues to achieve the maximum coverage and to play the role of the most robust contact points. The mechanisms of coassembly are unveiled in the light of both protein and polymer physical-chemistry, providing bioconjugate phase diagrams for the optimal material design.

Sustainable polyethylene fabrics with engineered moisture transport for passive cooling

Nature Sustainability, 2021

Polyethylene (PE) has emerged recently as a promising polymer for incorporation in wearable texti... more Polyethylene (PE) has emerged recently as a promising polymer for incorporation in wearable textiles owing to its high infrared transparency and tuneable visible opacity, which allows the human body to cool via thermal radiation, potentially saving energy on building refrigeration. Here, we show that single-material PE fabrics may offer a sustainable, high-performance alternative to conventional textiles, extending beyond radiative cooling. PE fabrics exhibit ultra-light weight, low material cost and recyclability. Industrial materials sustainability (Higg) index calculations predict a low environmental footprint for PE fabrics in the production phase. We engineered PE fibres, yarns and fabrics to achieve efficient water wicking and fast-drying performance which, combined with their excellent stain resistance, offer promise in reducing energy and water consumption as well as the environmental footprint of PE textiles in their use phase. Unlike previously explored nanoporous PE materials, the high-performance PE fabrics in this study are made from fibres melt spun and woven on standard equipment used by the textile industry worldwide and do not require any chemical coatings. We further demonstrate that these PE fibres can be dry coloured during fabrication, resulting in dramatic water savings without masking the PE molecular fingerprints scanned during the automated recycling process. The textile industry is one of the largest polluters. Here the authors show that polyethylene is a sustainable alternative textile with water wicking and fast-drying performance. The fabrication of polyethylene fabrics is compatible with standard equipment and could be dry-coloured, further reducing water consumption.

Sustainable freshwater production using passive membrane distillation and waste heat recovery from portable generator sets

Applied Energy, 2020

Abstract More than two billion people live in areas affected by water stress. In some coastal reg... more Abstract More than two billion people live in areas affected by water stress. In some coastal regions, freshwater supply has been progressively improved by large-scale desalination systems, which are nowadays mostly driven by non-renewable energy sources. Here we discuss, and experimentally investigate, the use of small-scale desalination devices for freshwater production powered by waste heat from electric power generators. The water purification technology relies on a passive, multi-stage and thermally-driven membrane distillation device, recently proposed by some of the authors of this work. The distiller is powered by low-grade (temperature lower than 80 °C) waste heat, recovered from the coolant circuit of small diesel engines for electricity production. Field experiments show that, for the tested engine, up to 1.12  kW m - 2 can be recovered in standard operating conditions, which yield a nearly 2.61  L m - 2 h - 1 freshwater production from seawater. A lumped parameter model, validated by experiments, shows that this productivity could be eventually enhanced by tuning the number of distillation stages. Utilization with exhaust gases, and thus higher feeding working temperatures, is also discussed. The proposed solution may provide a sustainable, simple, inexpensive and efficient means for freshwater production from recovered waste heat, which would otherwise be wasted to the ambient. Therefore it could be particularly effective, for instance, for field hospitals in remote or impoverished areas, especially in emergency situations.

Integrated receivers with bottom subcooling for automotive air conditioning: detailed experimental study of their filling capacity

International Journal of Refrigeration, 2016

The use of the integrated receiver in condensers for common automotive air conditioning-A/C-syste... more The use of the integrated receiver in condensers for common automotive air conditioning-A/C-systems is widespread, because of its thermodynamic and operational advantages. Many studies have been already conducted on estimating the effect of the subcooling value. However, this study aims at determining the most important factors affecting the length of the refrigerant stable operating plateau and how the receiver filling is affected by geometrical and thermodynamic boundary conditions, by means of an experimental campaign built using design of experiments-DOE-techniques. Results demonstrate how the receiver diameter and the axle spacing between its inlet and outlet holes have the highest influence on the receiver operation. Finally, these results have been used to set up a numerical model able to accurately estimate the filling efficiency of the integrated receiver, in terms of volume of the operating plateau compared to the net available receiver volume.

Thermal fluid dynamic analysis in compact shell & tube heat exchangers for industrial applications

Compact fin&tube heat exchangers are employed in a wide range of engineering applications. Despit... more Compact fin&tube heat exchangers are employed in a wide range of engineering applications. Despite these components have by now been largely studied and the literature on the topic is huge, the interest on their numerical analysis and optimization is always actual. Furthermore, the continuous effort in the development of more and more sophisticated CFD tools, together with the increasing computational resource available (i.e. cluster facilities), contributes to maintain an interest on the numerical simulation and analysis of these components. The present work deals with the thermal fluid dynamic analysis of an industrial gas cooler by means of the commercial CFD solver ANSYS Fluent. The attention is firstly focused on the detailed analysis of the finned pack. The in-pack conditions are studied taking advantage of the symmetries of the domain. Different fin layouts are taken into consideration, in order to understand the effects of the geometrical features on the heat transfer coeffi...

Influence of Porous Electrode Structure on PEM Fuel Cells Design and Performance

2nd International Conference on Fuel Cell Science, Engineering and Technology, 2004

Gas flow in fuel cell porous electrodes is usually modelled with Darcy’s law, which requires the ... more Gas flow in fuel cell porous electrodes is usually modelled with Darcy’s law, which requires the definition of a resistance constant for the material. This can be done directly via experimentation or indirectly via numerical tuning to fit experimental data on cell behaviour. Both methods lack generality, as they do not take into account the particular porous structure of each electrode. In the present work, a numerical procedure for calculating the resistance constant for a given porous structure is presented. This procedure is based on Lattice Boltzmann models, which treat the problem from a microscopic point of view, reproducing collisions between fluid molecules and solid particles. It can be demonstrated that under certain hypotheses, these models yield Navier-Stokes equations on a macroscopic scale, hence obeying fluid mechanics laws. Here the flow in a set of thirty randomly generated porous structures was analyzed, thus obtaining a distribution of values for Darcy’s constant....

CFD Modeling of Solar Collector with Nano-Fluid Direct Absorption for Civil Application

Direct solar absorption has been considered often in the past as a possible configuration of sola... more Direct solar absorption has been considered often in the past as a possible configuration of solar thermal collectors for residential and small commercial applications. Of course, a direct absorption could improve the performance of solar collectors by skipping one step of the heat transfer mechanism of standard devices and by modifying the temperature distribution inside the collector. In fact, classical solar thermal collectors have a metal sheet as absorber, designed such that water has the minimum temperature in each transversal section, in order to collect as much as possible the solar thermal energy. On the other hand, in a direct configuration, the hottest part of the system is the operating fluid and this allows to have a more efficient conversion. Nanofluids, i.e. fluids with a suspension of nano-particles, as carbon nano-horns, could be a good and innovative family of absorbing fluids, for their higher absorption coefficient with respect to the base fluid and stability under moderate temperature gradients. Moreover, carbon nanohorns offer the significant advantage to be non-toxic unlike other carbon nanoparticles (e.g. carbon nanotubes). In this work, an original 3D model of the absorption phenomena in nano-fluids flowing in a cylindrical tube is coupled with a CFD analysis of the flow and temperature field. Recent measurements of the optical properties of nano-fluids with different concentrations have been used for the radiation heat transfer modeling and included in the fluid dynamic modeling as well. Heat losses due to conduction, convection and radiation at the boundaries are included in the model. The results are compared with the typical performance of flat solar collectors present on the market.

Interfacial water thickness at inorganic nanoconstructs and biomolecules: Size matters

Physics Letters A, 2016

Water molecules in the proximity of solid nanostructures influence both the overall properties of... more Water molecules in the proximity of solid nanostructures influence both the overall properties of liquid and the structure and functionality of solid particles. The study of water dynamics at solid-liquid interfaces has strong implications in energy, environmental and biomedical fields. This article focuses on the hydration layer properties in the proximity of Carbon Nanotubes (CNTs) and biomolecules (proteins, polipeptides and amino acids). Here we show a quantitative relation between the solid surface extension and the characteristic length of water nanolayer (δ), which is confined at solid-liquid interfaces. Specifically, the size dependence is attributed to the limited superposition of nonbonded interactions in case of small molecules. These results may facilitate the design of novel energy or biomedical colloidal nanosuspensions, and a more fundamental understanding of biomolecular processes influenced by nanoscale water dynamics.

With Tunable Bulk Viscosity for Enhancing Stability

Taking advantage of a closed-form generalized Maxwell distribution function [P. Asinari and I.V. ... more Taking advantage of a closed-form generalized Maxwell distribution function [P. Asinari and I.V. Karlin, Phys. Rev. E 79, 036703 (2009)] and splitting the relaxation to the equilibrium in two steps, an entropic quasi-equilibrium (EQE) kinetic model is proposed for the simulation of low Mach number flows, which enjoys both the H-theorem and a free-tunable parameter for controlling the bulk viscosity in such a way as to enhance numerical stability in the incompressible flow limit. Moreover, the proposed model admits a simplification based on a proper expansion in the low Mach number limit (LQE model). The lattice Boltzmann implementation of both the EQE and LQE is as simple as that of the standard lattice Bhatnagar-Gross-Krook (LBGK) method, and practical details are reported. Extensive numerical testing with the lid driven cavity flow in two dimensions is presented in order to verify the enhancement of the stability region. The proposed models achieve the same accuracy as the LBGK method with much rougher meshes, leading to an effective computational speed-up of almost three times for EQE and of more than four times for the LQE. Three-dimensional extension of EQE and LQE is also discussed.

European Materials Modelling Council

The aim of the European Materials Modelling Council (EMMC) is to establish current and forward lo... more The aim of the European Materials Modelling Council (EMMC) is to establish current and forward looking complementary activities necessary to bring the field of materials modelling closer to the demands of manufacturers (both small and large enterprises) in Europe. The ultimate goal is that materials modelling and simulation will become an integral part of product life cycle management in European industry, thereby making a strong contribution to enhance innovation and competitiveness on a global level. Based on intensive efforts in the past two years within the EMMC, which included numerous consultation and networking actions with representatives of all stakeholders including Modellers, Software Owners, Translators and Manufacturers in Europe, the EMMC identified and proposed a set of underpinning and enabling actions to increase the industrial exploitation of materials modelling in Europe. EMMC will pursue the following overarching objectives in order to bridge the gap between acad...

Nonlinear Boltzmann equation for the homogeneous isotropic case: Minimal deterministic Matlab program

The homogeneous isotropic Boltzmann equation (HIBE) is a fundamental dynamic model for many appli... more The homogeneous isotropic Boltzmann equation (HIBE) is a fundamental dynamic model for many applications in thermodynamics, econophysics and sociodynamics. Despite recent hardware improvements, the solution of the Boltzmann equation remains extremely challenging from the computational point of view, in particular by deterministic methods (free of stochastic noise). This work aims to improve a deterministic direct method recently proposed [V.V. Aristov, Kluwer Academic Publishers, 2001] for solving the HIBE with a generic collisional kernel and, in particular, for taking care of the late dynamics of the relaxation towards the equilibrium. Essentially (a) the original problem is reformulated in terms of particle kinetic energy (exact particle number and energy conservation during microscopic collisions) and (b) the computation of the relaxation rates is improved by the DVM-like correction, where DVM stands for Discrete Velocity Model (ensuring that the macroscopic conservation laws ar...

Link-wise Artificial Compressibility Method

The Artificial Compressibility Method (ACM) for the incompressible Navier-Stokes equations is (li... more The Artificial Compressibility Method (ACM) for the incompressible Navier-Stokes equations is (link-wise) reformulated (referred to as LW-ACM) by a finite set of discrete directions (links) on a regular Cartesian mesh, in analogy with the Lattice Boltzmann Method (LBM). The main advantage is the possibility of exploiting well established technologies originally developed for LBM and classical computational fluid dynamics, with special emphasis on finite differences (at least in the present paper), at the cost of minor changes. For instance, wall boundaries not aligned with the background Cartesian mesh can be taken into account by tracing the intersections of each link with the wall (analogously to LBM technology). LW-ACM requires no high-order moments beyond hydrodynamics (often referred to as ghost moments) and no kinetic expansion. Like finite difference schemes, only standard Taylor expansion is needed for analyzing consistency. Preliminary efforts towards optimal implementation...

Integrated molecular dynamics and experimental approach to characterize low-free-energy perfluoro-decyl-acrylate (PFDA) coated silicon

Materials & Design, 2021

This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Unfolding the prospects of computational (bio)materials modeling

The Journal of Chemical Physics, 2020

In this perspective communication, we briefly sketch the current state of computational (bio)mate... more In this perspective communication, we briefly sketch the current state of computational (bio)material research and discuss possible solutions for the four challenges that have been increasingly identified within this community: (i) the desire to develop a unified framework for testing the consistency of implementation and physical accuracy for newly developed methodologies, (ii) the selection of a standard format that can deal with the diversity of simulation data and at the same time simplifies data storage, data exchange, and data reproduction, (iii) how to deal with the generation, storage, and analysis of massive data, and (iv) the benefits of efficient "core" engines. Expressed viewpoints are the result of discussions between computational stakeholders during a Lorentz center workshop with the prosaic title Workshop on Multi-scale Modeling and are aimed at (i) improving validation, reporting and reproducibility of computational results, (ii) improving data migration between simulation packages and with analysis tools, (iii) popularizing the use of coarse-grained and multi-scale computational tools among non-experts and opening up these modern computational developments to an extended user community.