Vittorio Raffaele A. Romano

A mathematical model to study the influence of wireless temperature sensor during assessment of canned food sterilization

Abstract Wireless temperature sensors (WTS) are measurement devices widely used by food industry to determine time-temperature history during typical processes, such as thermal sterilization. A mathematical model was developed to study, under certain hypotheses, how the insertion of (WTS) influence the heat transfer into conductive canned food. The considered system is mainly described by a can filled with a conductive food with a WTS fixed at the bottom or suspended in the container, to measure the temperature at the slowest heating point. The equations have been solved by means of the finite element method to predict the temperature in every point of the domain. The domain has been meshed in different ways, by increasing the node density where a better investigation is needed, such as around the WTS. The kinetics of microbial inactivation was coupled to the heat transfer model to analyse the processes in terms of the sterilizing value. Simulation results show that the influence of the temperature sensor is related to the relative dimensions of can and WTS, as well as to the WTS position into the container.

Glucoamylase by recombinant Kluyveromyces lactis cells: production and modelling of a fed batch bioreactor

A cultural system, aimed at the production of glucoamylase with cells of a non-conventional yeast transformed for the enzyme expression, Kluyveromyces lactis JA6-GAA was realised. Glucoamylase production was accomplished in a reactor operating in fed batch mode to avoid limitations with respect to oxygen transfer, and achieve high cell density. A mathematical model able to describe batch and fed batch operations was developed. The theoretical and experimental approach permitted to catch sight of possible physiological changes in the producer strain and set up a suitable fed-batch run to achieve a higher cell density.

Anisotropic thermal conductivity study of nano-additives/epoxy based nanocomposites

This study investigates the anisotropic thermal conductivity behavior of an tetrafunctional epoxy resin containing low percentages (at loading level from 0.25 to 2% wt) of different types of carbon...

Evaluation of thermal and electrical conductivity of carbon-based PLA nanocomposites for 3D printing

PLA nanocomposites for fused-deposition modeling (FDM) technique are considered. Thermal and electrical conductivity of carbon-based PLA nanocomposites are investigated looking at the different morphological characteristic of the carbon nanoparticles. In particular commercial multi-walled carbon nanotubes (CNTs) and graphene nanoplates (GNPs) are considered as filler in order to realize filament for 3D printed devices for electrical and thermal application. In this paper a filler concentration up to 12% in weight is investigated. Transient Plane Source (TPS) measurements of thermal conductivity show that better heat conduction is obtained through the incorporation in the PLA matrix of carbonaceous nanostructures with predominantly two-dimensional shape (GNPs). DC electrical measurements show that the nanocomposite filled with the predominant mono-dimensional carbon nanoparticle (i.e. CNT) exhibits lower electrical percolation threshold, whereas a greater post percolation electrical conductivity is established with the two-dimensional filler (i.e. GNP). Such characteristics are to be considered in order to make robust and cost effective 3D printed device, by preferring 1D filler or 2D filler for electrical or thermal application respectively. Moreover, multiphase nanocomposites obtained with an optimized combination of CNT and GNP nanoparticles could be exploited to realize devices for joint electrical and thermal application.PLA nanocomposites for fused-deposition modeling (FDM) technique are considered. Thermal and electrical conductivity of carbon-based PLA nanocomposites are investigated looking at the different morphological characteristic of the carbon nanoparticles. In particular commercial multi-walled carbon nanotubes (CNTs) and graphene nanoplates (GNPs) are considered as filler in order to realize filament for 3D printed devices for electrical and thermal application. In this paper a filler concentration up to 12% in weight is investigated. Transient Plane Source (TPS) measurements of thermal conductivity show that better heat conduction is obtained through the incorporation in the PLA matrix of carbonaceous nanostructures with predominantly two-dimensional shape (GNPs). DC electrical measurements show that the nanocomposite filled with the predominant mono-dimensional carbon nanoparticle (i.e. CNT) exhibits lower electrical percolation threshold, whereas a greater post percolation electrical conductivity is establi...

Thermal investigation of tetrafunctional epoxy resin filled with different carbonaceous nanostructures

This paper presents a preliminary investigation of thermal behaviour of epoxy nanocomposites containing different types of nanofillers, such as 1-D Multiwall Carbon Nanotubes (MWCNTs) and 2-D predominant shape of Exfoliated Graphite nanoparticles (EG). The cure behavior of the different epoxy formulations (filled and unfilled) was studied by Differential Scanning Calorimetry (DSC).The DSC technique is particularly advantageous for studying the cure of reactive epoxy systems because the curing process is accompanied by the liberation of heat. For all the epoxy nanocomposites analyzed in this work, Differential Scanning Calorimetry (DSC) investigation shows curing degree (DC) values higher than 92% for the curing cycle up to 200°C, reaching up to 100% for the samples filled with Exfoliated Graphite nanoparticles (EG). The calorimetric results also show that Exfoliated Graphite nanoparticles accelerate the curing process of the epoxy resin of about 20°C. Transient Plane Source measurements of thermal conduct...

Thermal conductivity of epoxy nanocomposites filled with MWCNT and hydrotalcite clay: A preliminary study

Aim of this work is to study the effect clay on the thermal conductivity of epoxy resin filled with CNTs. Experiments and theoretical predictions show that the presence of hydrotalcite clay in a mesh of carbon nanotubes gives rise to aggregates and twisted bundles, resulting in a lower carbon nanotubes length and a lower thermal conductivity of epoxy nanocomposites.

On the effectiveness factor of immobilized enzymes with linear mixed-type product inhibition kinetics

Abstract The problem of simultaneous mass transfer and product-inhibited enzyme kinetics in porous slabs was numerically solved. Effectiveness factor and overall reaction rate were evaluated as function of physical and kinetic parameters. The study was mainly focused on the linear mixed-type product inhibition pattern. It was proved that, independently of the Thiele modulus, uncertainty exists in identifying the inhibition mechanism in the case of entrapped enzymes. Unexpected behaviours of the observable rate of reaction were pointed out and the possibility was presented of optimizing product formation per unit biocatalyst weight by appropriately selecting substrate conversion, i.e. concentrations of reactant and product in the liquid phase bathing the external particle surface.