Enhanced heat transfer in oscillatory flows within multiple-hole baffled tubes

Compound enhancement techniques are considered to be the forefront of heat transfer enhancement. In this work, the combination of active and passive techniques in low-Reynolds number tube flows is explored by means of the superposition of a fully-reversing oscillatory flow into a baffled tube. This arrangement has been employed during the last twenty-years in the so called ‘oscillatory baffled reactors’, focusing on the achievement of plug flow. Little work has been done, however, on the experimental and numerical analysis of the enhanced convective heat transfer that follows the resulting chaotic flow. A standard single-hole baffle geometry has been previously characterized experimentally by some authors, whereas the potential of multiple-hole baffles has not been studied from the point of view of enhanced heat transfer. A numerical investigation has been undertaken to examine the heat transfer augmentation in multiple-hole baffled tubes with fully-reversing oscillatory flow. Different circular baffles with 1, 3, 7, 19 and 43 holes are analyzed, all of them releasing the same total cross sectional area. The flow across these baffles generates a beam of jets which extend downstream and upstream –according to the reversing flow - showing different swirl structures that promote intensive radial mixing and early onset of turbulence. As a consequence, heat transfer between the fluid and the tube wall is significantly enhanced. A circular tube of 25 mm inner diameter has been modeled with 10 baffles uniformly spaced. The simultaneously hydrodynamic and thermal developing flow has been simulated with uniform heat flux as boundary condition in the tube wall, using water as working fluid. The achievement of spatial and time periodicity is thoroughly analyzed prior to the data reduction for the computation of Nusselt number. The time-resolved and time-averaged heat transfer characteristics are presented for an oscillating frequency ranging from f=0.1 Hz to f=1Hz and oscillating amplitudes of x0=� , 2�/3 and �/3 (where � is the inner hole diameter for each baffle). The strong dependency of Nusselt number on the operating parameters of the oscillations is reported. Besides, the positive influence of an increasing number of baffle holes is demonstrated, and a description of the flow structures that induce this heat transfer augmentation is discussed.Papers presented to the 12th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Costa de Sol, Spain on 11-13 July 2016

Process development using oscillatory baffled mesoreactors

PhD ThesisThe mesoscale oscillatory baffled reactor (meso-OBR) is a flow chemistry platform whose niche is the ability to convert long residence time batch processes to continuous processes. This reactor can rapidly screen reaction kinetics or optimise a reaction in flow with minimal waste. In this work, several areas were identified that could be addressed to broaden the applicability of this platform. Four main research themes were subsequently formulated and explored: (I) development of deeper understanding of the fluid mechanics in meso-OBRs, (II) development of a new hybrid heat pipe meso-OBR for improved thermal management, (III) further improvement of continuous screening using meso-OBRs by removing the solvent and employing better experiment design methodologies, and (IV) exploration of 3D printing for rapid reactor development. I. The flow structures in a meso-OBR containing different helical baffle geometries were studied using computational fluid dynamics simulations, validated by particle image velocimetry (PIV) experiments for the first time. It was demonstrated, using new quantification methods for the meso-OBR, that when using helical baffles swirling is responsible for providing a wider operating window for plug flow than other baffle designs. Further, a new flow regime resembling a Taylor-Couette flow was discovered that further improved the plug flow response. This new double vortex regime could conceivably improve multiphase mixing and enable flow measurements (e.g. using thermocouples inside the reactor) to be conducted without degrading the mixing condition. This work also provides a new framework for validating simulated OBR flows using PIV, by quantitatively comparing turbulent flow features instead of qualitatively comparing average velocity fields. II. A new hybrid heat pipe meso-OBR (HPOBR) was prototyped to provide better thermal control of the meso-OBR by exploiting the rapid and isothermal properties of the heat pipe. This new HPOBR was compared with a jacketed meso-OBR (JOBR) for the thermal control of an exothermic imination reaction conducted without a solvent. Without a solvent or thermal control scheme, this reaction exceeded the boiling point of one of the reactants. A central composite experiment design explored the effects of reactant net flow rate, oscillation intensity and cooling capacity on the thermal and chemical response of the reaction. The HPOBR was able to passively control the temperature below the boiling point of the reactant at all conditions through heat spreading. Overall, a combined 260-fold improvement in throughput was demonstrated compared to a reactor requiring the use of a solvent. Thus, this ii wholly new reactor design provides a new approach to achieving green chemistry that could be theoretically easily adapted to other reactions. III. Analysis of in situ Fourier transform infrared (FTIR) spectroscopic data also suggested that the reaction kinetics of this solventless imination case study could be screened for the first time using the HPOBR and JOBR. This was tested by applying flow-screening protocols that adjusted the reactant molar ratio, residence time, and temperature in a single flow experiment. Both reactor configurations were able to screen the Arrhenius kinetics parameters (pre-exponential factors, activation energies, and equilibrium constants) of both steps of the imination reaction. By defining experiment conditions using design of experiments (DoE) methodologies, a theoretical 70+% reduction in material usage/time requirement for screening was achieved compared to the previous state-of-the-art screening using meso-OBRs in the literature. Additionally, it was discovered that thermal effects on the reaction could be inferred by changing other operating conditions such as molar ratio and residence time. This further simplifies the screening protocols by eliminating the need for active temperature control strategies (such as a jacket). IV. Finally, potential application areas for further development of the meso-OBR platform using 3D printing were devised. These areas conformed to different “hierarchies” of complexity, from new baffle structures (simplest) to entirely new methods for achieving mixing (most complex). This latter option was adopted as a case study, where the passively generated pulsatile flows of fluidic oscillators were tested for the first time as a means for improving plug flow. Improved plug flow behaviour was indeed demonstrated in three different standard reactor geometries (plain, baffled and coiled tubes), where it could be inferred that axial dispersion was decoupled from the secondary flows in an analogous manner to the OBR. The results indicate that these devices could be the basis for a new flow chemistry platform that requires no moving parts, which would be appealing for various industrial applications. It is concluded that, for the meso-OBR platform to remain relevant in the next era of tailor-made reactors (with rapid uptake of 3D printing), the identified areas where 3D printing could benefit the meso-OBR should be further explored

Valorization of waste cooking oil based biodiesel for biolubricant production in a vertical pulsed column: Energy efficient process approach

International audienceDevelopment of bio-based lubricants have received growing interest as sustainable substitutes to petroleum-based lubricants due to their renewability, biodegradability and superior physicochemical properties. Biolubricant production from waste cooking oil in an intensified reactor, which is designed with the aim of scaling-up for industrial purposes, can effectively decrease the cost of finished product. In this study, a vertical pulsed column with tri-orifice baffles was applied to produce trimethylolpropane fatty acid triester (biolubricant) from waste cooking oil, which is a cost and environmentally effective feedstock. This type of reactor enables high interfacial areas between immiscible reactants, leading to improved reaction performance. In addition, response surface methodology was used to optimize the levels of different operating parameters to obtain the highest reaction yield and the lowest power consumption. An optimal reaction yield of 83.3% and power consumption of 1006 kW/m 3 were obtained with an oscillation frequency of 3.6 Hz, a baffle spacing of 1.45d e , a molar ratio of 4:1 and a potassium carbonate catalyst loading of 1%

Energy dissipation and mixing characterization in continuous oscillatory baffled reactor

The focus of this thesis is to study the macro and micromixing performance of a secondary component in the bulk flow and how it should be introduced into a COBR. The effect of the position of secondary feeds, the influence of the oscillatory conditions and power dissipation on the macro and micromixing performance is studied, using numerical simulations and experiments carried out in a commercial Nitech® OBR with smooth constrictions. Energy dissipation is calculated through CFD simulations using two different ways – via viscous energy dissipation and the mechanical energy balance, the latter being preferred due to its lower demand for a refined computational mesh. A dimensionless power density number is obtained and proposed as a useful tool in the prediction of power density in COBRs. The impact of the position where a secondary feed enters the COBR on the spatial mixing quality is studied, and shows that when the source position is chosen correctly, an increase in the velocity ratio enhances mixing performance from 2% to 87% of the perfectly mixed state. The influence of the oscillatory conditions and flow rate of a secondary feed on the micromixing quality is analysed. Micromixing performance does not appear to correlate directly with power density. However, higher amplitudes and lower frequencies are preferred over lower amplitudes and higher frequencies to have a better micromixing performance. An attempt at characterising macromixing in the COBR experimentally using a coloured tracer was made however unexpected mixing performance was observed. Some preliminary experiments therefore focused on the behaviour of the tracer upstream of the COBR as a function of the oscillatory conditions

Characterisation of solid-liquid flow in a continuous oscillatory baffled reactor using computational fluid dynamics

Continuous Oscillatory Baffled Reactors (COBRs) have been proven a viable alternative to traditional batch reactors for organic synthesis and crystallization processes. This thesis investigates the behaviour of solids in liquid in a COBR using CFD. Firstly, CFD is used to analyse the validity of two existing models for the estimation of power density in this type of reactors, the “quasi-steady” model (QSM) and the “eddy enhancement” model. By using a revised power law dependency on the number-of-baffles term (nx) in both models, an appropriate orifice discharge coefficient (CD) in the QSM and a proposed empirical correlation estimate EEM’s “mixing length”, both models were successfully validated. Secondly, energy losses experienced by both liquid and solid phases in COBRs are analysed; for the former, temporal pressure drop profiles and power dissipation rates along the length of a COBR are monitored for a wide range of operating and geometric conditions. The results provide detailed insights into the relationship between power dissipation and pressure drop profiles and reveals that geometries that are perfectly symmetric in the axial direction, i.e. periodically repeatable, do not present signs of energy losses. On the other hand, geometric events such as sections missing one or multiple baffle constrictions led to a decrement in power dissipation rates and velocities, caused by the eddy shedding phenomenon within the missing baffle sections. And sections with a reduced cross-sectional area of the baffle constriction and bend joints do not yield energy losses in the device; instead, they require a higher power density for the flow to overcome these constraints. A multiphase (S-L) Eulerian- Lagrangian model was employed to simulate the presence of solid particles suspended in a continuous liquid phase in a COBR. The behaviour of these particles was monitored with time as they travelled downstream the device for particles of different sizes; results unveiled that as particles increases in size they experience dampening in oscillatory velocity, translating into smaller axial dispersion, longer residence times and a reduction of particles’ suspension. For the determination of axial dispersion, both perfect and imperfect pulse methods were employed, the latter providing more reliable results. Thirdly, this research introduces an alternative Lagrangian based methodology, i.e. the Smoothed-Particle Hydrodynamics (SPH), for the simulation of fluid flow in an OBR. The results from a bespoke SPH solver are compared with those from Eulerian modelling, i.e. Finite Volume (FV) method, displaying a high degree of agreement. SPH was able to capture the expected flow characteristics in OBR as clearly and equally as its Eulerian counterpart. Making full use of SPH’s capabilities and its Lagrangian feature, two new indexes for the assessment of mixing and plug flow efficiency have also been proposed.Engineering and Physical Sciences Research Council (EPSRC)

Selection, development and design of a continuous and intensified reactor technology to transform waste cooking oil in biodiesel and biosourced formulations

L'objectif de cette thèse est de proposer un réacteur continu et intensifié pour la transformation d’huiles végétales de récupération en produits ou intermédiaires qui seront ensuite utilisés ou formulés en applications destinées au BTP. Ce travail s’inscrit dans le cadre du FUI AGRIBTP, projet de recherche collaboratif qui a pour finalité la création d'un outil industriel de valorisation des sous-produits de l'agro-industrie. Le réacteur se veut pluri-réactionnel, c’est-à-dire adapté et efficace pour réaliser les réactions de transestérification ou d’estérification par le méthanol ou par le glycérol, pour une consigne de production fixée à 100 kg/h. Pour parvenir à cet objectif, une revue de la littérature a permis de dégager une liste de technologies de réacteurs adaptés à ces réactions. L’analyse comparative de ces systèmes a conduit à sélectionner trois types de réacteurs intensifiés existant dans le commerce et qui ont été ensuite testés expérimentalement: les réacteurs microstructurés (type Corning®), les réacteurs micro-ondes et les réacteurs pulsés à chicanes (type NiTech®). De bonnes conversions sont obtenues pour les réactions de transestérification et d’estérification par le méthanol, montrant une meilleure efficacité de ces réacteurs intensifiés par rapport aux réacteurs conventionnels; en revanche les résultats sont encore insuffisants pour l’estérification avec le glycérol en raison de limitations en température. Concernant le réacteur micro-ondes, les excellents résultats rapportés dans la littérature sont à modérer en raison d’une imprécision de mesure de la température. La technologie de réacteurs pulsés à chicanes a finalement été retenue : leur flexibilité, l’indépendance entre le débit et le mélange généré, et enfin leur diamètre suffisamment étendu pour ne pas générer de blocage éventuel dû à l’encrassement du réacteur par la matière entrante sont les principaux arguments qui ont guidé ce choix. Le système disponible construit en verre a tout de même montré ses limites en montée en température et en pression et il a donc été envisagé d’étoffer nos investigations dans des gammes de fonctionnement plus larges. Ainsi une collaboration avec le laboratoire TNO de Delft, aux Pays-Bas a permis d’avoir accès à un réacteur pulsé à chicanes en acier inoxydable. Les résultats obtenus pour la réaction d’estérification par le glycérol - qui n’offrait pas jusqu’à présent des données concluantes - sont satisfaisants, et même de qualité supérieure comparés à ceux obtenus avec un réacteur tubulaire hélicoïdal lui aussi pulsé. Parallèlement à ces études, des simulations numériques des écoulements dans le réacteur ont permis de proposer des améliorations de la forme des chicanes, celle-ci étant déterminante pour la bonne capacité de dispersion liquide-liquide des réactifs immiscibles et la qualité du mélange. Ces simulations ont été comparées à des mesures de vitesses obtenues sur un pilote expérimental conçu pour permettre la visualisation par technique laser des écoulements dans un élément du réacteur à chicanes. Pour terminer, l’extrapolation des résultats obtenus sur les pilotes étudiés à une échelle de production de 100 kg/h a été initiée, aboutissant à la proposition d’un procédé permettant la production sélective de monoglycérides via l’estérification par le glycérol, mais également la fabrication de biodiesel par la transestérification, incluant un réacteur intensifié pulsé dont la géométrie de chicanes a été optimisée, et ce afin de répondre à l’objectif initial de la thèse. ABSTRACT : The objective of this thesis is to propose a continuous and intensified reactor to transform waste cooking oil into products that will be used in applications in the building and public works sector. This work is part of the FUI AGRIBTP, a collaborative research project whose finality is to the creation of an industrial tool for the reuse of co-products from agroindustries. The reactor must be able to handle transesterification and esterification (with methanol or with glycerol) reactions efficiently with a total flow rate of 100 kg/h. To achieve this objective, a literature review has identified a list of suitable reactor technologies for these reactions. The comparative analysis of these different technologies has led to the selection of three types of intensified reactors microstructured reactors (Corning® type), microwave reactors and oscillatory baffled reactors (NiTech® type). The performance of these reactors for transesterification and esterification reactions has then been investigated experimentally. High conversions have been obtained for transesterification and esterification with methanol reactions, thereby showing the improved performance of these intensified reactors compared with conventional reactors; however results obtained with esterification with glycerol reaction are still rather low due to limitations in operating temperature. Concerning the microwave reactor, the excellent results previously reported in the literature should be taken with care because of the inaccuracy of temperature measurements, as proven in this work. The oscillatory baffled reactor technology has been selected has the most industrially viable equipment for the considered reactions. The flexibility of this reactor, the independency of the flow rate and mixing, as well as the diameter ,which is large enough to avoid fouling caused by the quality of the feed line, are the main reasons for this choice. The commercial available system, built in glass, has nevertheless shown limitations in terms of operating temperature and pressure. As a result, further work has focused on reactor operation in a wider range of operating conditions. To do this, a collaboration with the TNO laboratory in Delft, Netherlands, was set up in order to investigate reaction performance an oscillatory baffled reactor made of stainless steel. The reaction performance obtained for esterification with glycerol is more than satisfactory, being significantly greater that that obtained in the glass Nitech reactor and even of higher quality compared to that obtained with a oscillatory helicoidal tubular reactor. In parallel to these studies, CFD simulations of flow in the reactor have enable the investigation of new baffle designs, which play a major role in the capacity to generation liquid-liquid dispersions of the immiscible reactants and in the quality of the mixing. These simulations have been compared with velocity measurements and flow patterns obtained in a transparent experimental rig using Particle Image Velocimetry. Finally, the results obtained on the pilot-scale rigs have been used to size a the oscillatory flow reactor for a total flow rate of 100 kg/h, which would be dedicated to the selective production of monoglycerides by esterification with glycerol reaction and also biodiesel production by transesterification reaction

Selection, development and design of a continuous and intensified reactor technology to transform waste cooking oil in biodiesel and biosourced formulations

The objective of this thesis is to propose a continuous and intensified reactor to transform waste cooking oil into products that will be used in applications in the building and public works sector. This work is part of the FUI AGRIBTP, a collaborative research project whose finality is to the creation of an industrial tool for the reuse of co-products from agroindustries. The reactor must be able to handle transesterification and esterification (with methanol or with glycerol) reactions efficiently with a total flow rate of 100 kg/h. To achieve this objective, a literature review has identified a list of suitable reactor technologies for these reactions. The comparative analysis of these different technologies has led to the selection of three types of intensified reactors microstructured reactors (Corning® type), microwave reactors and oscillatory baffled reactors (NiTech® type). The performance of these reactors for transesterification and esterification reactions has then been investigated experimentally. High conversions have been obtained for transesterification and esterification with methanol reactions, thereby showing the improved performance of these intensified reactors compared with conventional reactors; however results obtained with esterification with glycerol reaction are still rather low due to limitations in operating temperature. Concerning the microwave reactor, the excellent results previously reported in the literature should be taken with care because of the inaccuracy of temperature measurements, as proven in this work. The oscillatory baffled reactor technology has been selected has the most industrially viable equipment for the considered reactions. The flexibility of this reactor, the independency of the flow rate and mixing, as well as the diameter ,which is large enough to avoid fouling caused by the quality of the feed line, are the main reasons for this choice. The commercial available system, built in glass, has nevertheless shown limitations in terms of operating temperature and pressure. As a result, further work has focused on reactor operation in a wider range of operating conditions. To do this, a collaboration with the TNO laboratory in Delft, Netherlands, was set up in order to investigate reaction performance an oscillatory baffled reactor made of stainless steel. The reaction performance obtained for esterification with glycerol is more than satisfactory, being significantly greater that that obtained in the glass Nitech reactor and even of higher quality compared to that obtained with a oscillatory helicoidal tubular reactor. In parallel to these studies, CFD simulations of flow in the reactor have enable the investigation of new baffle designs, which play a major role in the capacity to generation liquid-liquid dispersions of the immiscible reactants and in the quality of the mixing. These simulations have been compared with velocity measurements and flow patterns obtained in a transparent experimental rig using Particle Image Velocimetry. Finally, the results obtained on the pilot-scale rigs have been used to size a the oscillatory flow reactor for a total flow rate of 100 kg/h, which would be dedicated to the selective production of monoglycerides by esterification with glycerol reaction and also biodiesel production by transesterification reaction

Mixing, mass transfer and energy analysis across bioreactor types in microalgal cultivation and lipid production

Microalgae are recognised as a source of lipids for bioenergy, nutrients and pharmaceuticals. Photobioreactors, closed vessels for microalgal cultivation, are known to have high energy consumption due to mixing and aeration. Sparging is commonly used for mixing and gas-liquid mass transfer in photobioreactors, but is energy intensive. The aim of this work was to reduce these energy requirements by optimising conventional sparging and considering surface aeration coupled with mechanical agitation as an alternative. An airlift photobioreactor was used as a base for comparison with two novel, surface aerated reactors: oscillatory baffled and wave photobioreactors. The three bioreactors were compared in terms of power input, mixing, CO2 mass transfer, algal growth and lipid production. Prior to comparison, each photobioreactor was optimised based on these parameters. To calculate power input, isothermal gas expansion equations were used for sparged systems and calorimetry was used for mechanically agitation systems. Mixing was investigated using a salt tracer and phenolphthalein indicator and mass transfer was measured using the gassing-in method. Scenedesmus sp., a high lipid-producer, was cultivated in low nitrate media across a range of mixing rates in each photobioreactor.In the airlift photobioreactor a critical minimum CO2 supply rate (of 2.7×10-5 m s-1) was found, below which carbon was limiting and above which energy was spent on sparging without increased productivity (0.20 g L-1 d-1 biomass; 0.03 g L-1 d-1 lipid). In the oscillatory baffled reactor, insufficient mass transfer limited algal productivity (0.11 g L-1 d-1 biomass; 0.02 g L-1 d-1 lipid). The wave reactor had high CO2 mass transfer coefficients (10 – 140 h-1) in comparison to the airlift (2.7 – 40 h-1) and oscillatory baffled reactors (6.3 – 37 h-1). Sufficient biomass productivity (0.18 g L- -1 d-1) and higher lipid productivity (0.045 g L-1 d-1) at lower power input in the wave reactor resulted in higher energy efficiency compared to the airlift reactor. Life cycle analysis of simulated algal biodiesel production showed that bioreactor energy contributed 99% of total energy consumption. Therefore, the global warming potential was reduced by 73% when the airlift reactor was operated at the critical minimum CO2 supply (with gas compression to 2 bar) and a further 19% when the wave reactor was used. This work offers an energy efficient alternative to sparging, through the generation of a well-mixed wave in a surface aerated bioreactor. It also offers methods for optimisation of energy usage with respect to mixing and aeration. Reducing bioreactor energy consumption is key to feasibility, and was demonstrated here to reduce energy-related environmental burdens

Process development for the continuous epoxidation of renewable terpenes using “Mesoscale” 3D-printed oscillatory baffled reactor

Ph. D. Thesis.A continuous process was developed for the epoxidation of (R)-(+)-limonene and α-pinene with an oxidant (H2O2) using a polytungstophosphate catalyst in a mesoscale Oscillatory Baffled Reactor (mesoOBR). Waste biomass derived (R)-(+)-limonene and α-pinene were used as an alternative to petrochemical-based epoxides. A selective process towards the epoxides was investigated by the screening of process parameters including temperature, oxidant molar ratio, sodium sulphate (Na2SO4) amount, acid (H2SO4) concentration and solvent type. The mass and heat transfer limitation associated with the exothermic and biphasic epoxidation reaction was overcome using new 3D-printed baffles in the mesoOBR platform. Screening the process parameters for the epoxidation of (R)-(+)-limonene revealed that a high H2O2 conversion (~95 %) and selectivity to the limonene-1,2-epoxide (100 %), was able to achieve in 15 minutes with a single-step addition of H2O2. The operating conditions included a 50 °C temperature in an organic solvent-free environment, with a (R)-(+)- limonene/H2O2/catalyst molar ratio of 4:1:0.005. To prevent the hydrolysis of the epoxide, the reaction mixture was saturated with Na2SO4 (5.7 g). An acid concentration of lower than 0.04 M was used and found to have a significant effect on the selectivity. Kinetic studies were performed to allow modelling of the reaction scheme. A kinetic investigation showed that the reaction was first-order in terms of (R)-(+)-limonene and catalyst concentration, and fractional order (~0.5) with respect to the H2O2 concentration. The activation energy for the formation of limonene-1,2-epoxide and limonene1,2-diol was determined to be ~36 and 79 kJ mol‒1 , respectively. The epoxidation of α-pinene with H2O2 was also performed using polytungstophosphate catalyst. The variables in the screening parameters were temperatures (30–70 °C), oxidant amount (100-200 mol%), acid concentrations (0.02-0.09 M) and solvent types (1,2- dichloroethane, toluene, p-cymene, and acetonitrile). Screening the process parameters revealed that a 100% selective epoxidation of α-pinene to α-pinene oxide was possible with negligible side-product formation within a short reaction time (~20 minutes), using process conditions of a 50 °C temperature in an organic solvent-free environment and a α-pinene/H2O2/catalyst molar ratio of 5:1:0.01. A kinetic investigation also showed that the reaction was first-order in terms of α-pinene and catalyst concentration, and fractional order (~0.5) with respect to the H2O2 concentration. The activation energy of ~35 kJ mol-1 was obtained for the epoxidation of αpinene, which was similar to ~36 kJ mol-1 for (R)-(+)-limonene. Novel 3D-printed orifice baffles were integrated with a mesoscale oscillatory baffled reactor for the continuous epoxidation of terpenes ((R)-(+)-limonene and α-pinene) with H2O2 in an organic solvent-free environment. The biphasic reaction is highly exothermic, usually requiring solvent, tight temperature control and effective multiphase mixing. The performance of the new 3D-printed single, tri- and multi-orifice baffles was compared to conventional helical and integral baffles. The performance investigated were the mixing intensity, induction period, multi steady state and heat removal capability. Passive isothermalisation was also investigated using mesoOBR in a heat pipe assembly. The tri- and multi-orifice baffles were able to overcome mixing limitation in continuous epoxidation and achieved a comparable rate of reaction to batch epoxidation at mixing condition of oscillatory Reynolds number (Reo) >850 and Reo >500, respectively. Both baffles exhibited rapid steady state attainment, shorter induction period at t = 1.5 residence time (τ) and better reproducibility with product variation of ~ 1.3%. Other mesoOBRs designs had induction times of 2.0 τ – 3.0 τ and product variations in the range of 1.6 – 2.1 %. The helically baffled mesoOBR designs demonstrated effective heat transfer capability, allowing the reaction to being operated isothermally with ±1 °C temperature variation in an organic solvent-free condition. Thisremoves the need of a solvent, thus reducing reaction volume by a 5-fold. The timescale for the reaction was reduced from ~ 8 hours in a conventional process to 30 minutes in the multi-orifice mesoOBR, a 16-fold reduction. Therefore, a better process has been developed for a continuous epoxidation of (R)-(+)- limonene and α-pinene with H2O2 using multi-orifice mesoOBRs, with a potential intensification factor of ~ 80.Universiti Putra Malaysia, The Ministry of Education, Malaysia, Engineering and Physical Sciences Research Council (ESPRC