813 research outputs found
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Monolithic optofluidic chips: from optical manipulation of single cells to quantum sensing of fluids
This paper was presented at the 4th Micro and Nano Flows Conference (MNF2014), which was held at University College, London, UK. The conference was organised by Brunel University and supported by the Italian Union of Thermofluiddynamics, IPEM, the Process Intensification Network, the Institution of Mechanical Engineers, the Heat Transfer Society, HEXAG - the Heat Exchange Action Group, and the Energy Institute, ASME Press, LCN London Centre for Nanotechnology, UCL University College London, UCL Engineering, the International NanoScience Community, www.nanopaprika.eu.We report on a new class of integrated optofluidic devices, fabricated by femtosecond laser
micromachining. The capability to combine optical waveguides with microfluidic channels in the same
glass chip provides a very powerful platform, introducing new tools in the field of optical sensing. Two
recent applications that greatly benefitted from this novel technology are on-chip optical manipulation of
single cells by optical forces and optical sensing of the refractive index of fluids by quantum states of light.
The specific properties of robustness, alignment free and portability of these devices pave the way to the use
of these advanced sensing technologies outside the lab, in a real application environment
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The separation of falling binary liquid film in the presence of inert components by diffusion distillation
This paper was presented at the 3rd Micro and Nano Flows Conference (MNF2011), which was held at the Makedonia Palace Hotel, Thessaloniki in Greece. The conference was organised by Brunel University and supported by the Italian Union of Thermofluiddynamics, Aristotle University of Thessaloniki, University of Thessaly, IPEM, the Process Intensification Network, the Institution of Mechanical Engineers, the Heat Transfer Society, HEXAG - the Heat Exchange Action Group, and the Energy Institute.The effects of heat and mass transfer on selectivity and mass fluxes in falling film evaporation of binary mixture on vertical surface, in the presence of inerts in gas (air, helium) and liquid (glycol) phase were investigated. The mathematical model of the process with different simplifying assumptions concerning heat and mass transfer was elaborated. In numerical calculations mass transfer resistances in both gas and liquid phases were considered. Experimental study was performed for 2-ipropanol-water system in the wide range of concentrations and temperatures. The comparison shows small effect of diffusional cross effects on mass transfer and selectivity
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Variation of Important Non-Dimensional Numbers During Bubble Growth at Nucleation Site in Microchannels
This paper was presented at the 4th Micro and Nano Flows Conference (MNF2014), which was held at University College, London, UK. The conference was organised by Brunel University and supported by the Italian Union of Thermofluiddynamics, IPEM, the Process Intensification Network, the Institution of Mechanical Engineers, the Heat Transfer Society, HEXAG - the Heat Exchange Action Group, and the Energy Institute, ASME Press, LCN London Centre for Nanotechnology, UCL University College London, UCL Engineering, the International NanoScience Community, www.nanopaprika.eu.Two phase flow initiates at Onset of Nucleate Boiling, where the first bubble emerges in the
downstream flow direction. Bubble nucleation and growth in microchannel heat sinks is very conspicuous
phase as the growing bubble can completely block the flow cross-section area at high heat flux. Hence,
microchannels are more susceptible to flow boiling instability. In this paper effort has been put to study the
bubble dynamics during bubble growth at nucleation site for microchannel in terms of non-dimensional
energy ratio numbers and their variation from bubble inception until departure. New non dimensional energy
ratio is also proposed, which can be useful to differentiate inertia controlled and thermal diffusion controlled
region during bubble growth at nucleation site
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Microchannel fluid flow and heat transfer by lattice boltzmann method
This paper was presented at the 4th Micro and Nano Flows Conference (MNF2014), which was held at University College, London, UK. The conference was organised by Brunel University and supported by the Italian Union of Thermofluiddynamics, IPEM, the Process Intensification Network, the Institution of Mechanical Engineers, the Heat Transfer Society, HEXAG - the Heat Exchange Action Group, and the Energy Institute, ASME Press, LCN London Centre for Nanotechnology, UCL University College London, UCL Engineering, the International NanoScience Community, www.nanopaprika.eu.Micro flow has become a popular field of interest due to the advent of micro electromechanical systems (MEMS). In this work, the lattice Boltzmann method, a particle-based approach, is applied to simulate the two-dimensional micro channel fluid flow.
We simulated fluid flow and heat transfer inside microchannel, the prototype application of this study is micro-heat exchangers. The main incentive to look at fluidic behaviour at micron scale is that micro devices tend to behave much differently from the objects we are used to handling in daily life. The choice of using LBM for micro flow simulation is a good one owing to the fact that it is based on the Boltzmann equation which is valid for the whole range of the Knudsen number. Slip velocity and temperature jump boundary conditions are used for the microchannel simulations with Knudsen number values covering the slip flow. The lattice Bhatnagar-Gross-Krook single relaxation time approximation was used. The results found are compared with the Navier-Stokes analytical and numerical results available in the literature and good matches are observed
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Heat transfer characteristics of hydrid microjet-microchannel cooling module
This paper was presented at the 4th Micro and Nano Flows Conference (MNF2014), which was held at University College, London, UK. The conference was organised by Brunel University and supported by the Italian Union of Thermofluiddynamics, IPEM, the Process Intensification Network, the Institution of Mechanical Engineers, the Heat Transfer Society, HEXAG - the Heat Exchange Action Group, and the Energy Institute, ASME Press, LCN London Centre for Nanotechnology, UCL University College London, UCL Engineering, the International NanoScience Community, www.nanopaprika.eu.The paper presents the experimental investigation of heat transfer intensification in a microjetmicrochannel
cooling module. Applied technology takes benefits from two very attractive heat removal
techniques. When jets are impinging on the surface, they have a very high kinetic energy at the stagnation
point, also in microchannels boundary layer is very thin allowing to obtain very high heat fluxes.
Main objective of this paper was to experimentally investigate the performance of a microjet-microchannel
cooling module. Intense heat transfer in the test section has been examined and described with precise
measurements of thermal and flow conditions. Reported tests were conducted under steady state conditions
for single phase liquid cooling.
Obtained database of experimental data were compared to standard cooling techniques, and compared with
superposed semi-empirical models for minichannels and microjet cooling, Mikielewicz and Muszynski
(2009). Gathered data with analytical solutions and numerical computer simulation allows the rational design
and calculation of hybrid modules and optimum performance of these modules for various industrial
applications
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Optical coherence tomography measurements of biological fluid flows with picolitre spatial localization
This paper was presented at the 4th Micro and Nano Flows Conference (MNF2014), which was held at University College, London, UK. The conference was organised by Brunel University and supported by the Italian Union of Thermofluiddynamics, IPEM, the Process Intensification Network, the Institution of Mechanical Engineers, the Heat Transfer Society, HEXAG - the Heat Exchange Action Group, and the Energy Institute, ASME Press, LCN London Centre for Nanotechnology, UCL University College London, UCL Engineering, the International NanoScience Community, www.nanopaprika.eu.Interest in studying the human and animal microcirculation has burgeoned in recent years. In part
this has been driven by recent advances in volumetric microscopy modalities, which allow the study of the
3-D morphology of the microcirculation without the limitations of 2-D intra-vital microscopy. In this paper
we highlight the power of optical coherence tomography (OCT) to image the normal and pathological
microcirculation with picolitre voxel sizes. Both Doppler and speckle-variance methods are employed to
characterize complex rheological flows both in-vitro and in-vivo. GPU accelerated image registration
methods are demonstrated in order to mitigate problems of bulk tissue motion in methods based on speckle
decorrelation. In-vivo images of the human nailfold microcirculation are shown
Ischemia with endovascular balloon during disarticulations and amputations of limbs
Objective Limb disarticulation has been widely performed since the
18th century, especially in war surgery. Actually is infrequently done
in orthopaedic and vascular surgery, and it is associated with a high
mortality rate because of frequent comorbidities. Disarticulation
usually is reserved for patients with malignant tumours or gangrene
from severe artherosclerosis. During disarticulation, hemodynamic
stability can be altered by hemorrhagic events in the femoral or
humeral arteries. We propose an endovascular technique for proximal
control of the artery to reduce blood loss during disarticulation. Our
experience today is limited at hip disarticulation.
Material and methods The vascular access was percutaneous at the
common femoral artery of the healthy limb. A 6 French (Fr) introducer
sheath was placed using the Seldinger technique. Under
fluoroscopic control, with a portable vascular C-arm capable of digitally
subtracter angiogram and roadmap angiography, a 0.035 inch
hydrophilic guide wire was crossed aver into the opposite side iliac
artery through a 5F contra angiographic catheter placed at the aortic
bifurcation. After a diagnostic angiography the guide wire was
replaced with an Amplatz 0.0035 inch, 260 cm long, super stiff guide
wire. Then, a 7 9 20 mm Ultra-thinTM SDS balloon catheter was
placed in the external iliac artery and systemic heparinization with
2500 UI was performed. The balloon catheter was inflated and femoral
pulsation ceased immediately. After proximal, endovascular
occlusion, hip disarticulation was accomplished without any hemorrhagic
complication. At the end of procedure, the balloon was deflated
and removed. Hemostasis of the surgical field completed the procedure.
The femoral access in the healthy common femoral artery was
controlled with a 6 Fr Angio-seal percutaneous hemostatic system.
Results and discussion In hip disarticulation, hemostatic tourniquets
cannot be used of the location of the operating field. Therefore,
control of bleeding is a major issue in this procedure. Various techniques
have been proposed, femoral vessels and nerves were attached before the disarticulation. The use of semi-compliant balloon catheters
for endovascular occlusion avoids injury to the endothelium of
the vessel wall during balloon inflation. However preoperative
assessment, with color-duplex scanning and plain abdominal radiographs,
is mandatory; coexisting atherosclerosis often is present
especially in elderly patients, and severe wall calcification can lead to
vessel rupture and retroperitoneal hematoma, or even balloon catheter
rupture. Moreover, color-duplex scanning and radiographs will help
in choosing the landing-zone for balloon inflation.
Conclusions Endovascular balloon assistance is a simple, safe and
effective technique in preventing major arterial bleeding during
amputation or disarticulation and can be routinely used
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Heat transfer enhancement with gas-to-gas micro heat exchangers
This paper was presented at the 4th Micro and Nano Flows Conference (MNF2014), which was held at University College, London, UK. The conference was organised by Brunel University and supported by the Italian Union of Thermofluiddynamics, IPEM, the Process Intensification Network, the Institution of Mechanical Engineers, the Heat Transfer Society, HEXAG - the Heat Exchange Action Group, and the Energy Institute, ASME Press, LCN London Centre for Nanotechnology, UCL University College London, UCL Engineering, the International NanoScience Community, www.nanopaprika.eu.A characterization of gas-to-gas micro heat exchangers has been performed in terms of pressure
drop behavior and heat transfer performance. The gas-to-gas micro heat exchangers differ by partition wall
material, partition wall thickness and flow arrangement. The pressure drop behavior has been analyzed due
to the pressure losses in different sections of the gas-to-gas micro heat exchangers. Increased pressure losses
in front of and behind the micro channels have been detected due to modified geometries in the inlet and
outlet distribution chambers. The heat transfer performance has been determined in terms of thermal
effectiveness. The comparison among different partition wall materials and partition wall thicknesses showed
no significant criteria of the influence of thermal conductivity on the thermal effectiveness. An assessment
due to an overall heat exchanger effectiveness has been performed to compare the gas-to-gas micro heat
exchangers. For this purpose, the overall exergy loss has been calculated by combination of thermal
effectiveness and pressure losses. A strong impact of the exergy loss due to pressure drop has been detected
which influences the overall exergy loss of the gas-to-gas micro heat exchangers
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The study of the influence of morphology anisotropy of clusters of superparamagnetic nanoparticle on magnetic hysteresis by Monte Carlo simulations
This paper was presented at the 4th Micro and Nano Flows Conference (MNF2014), which was held at University College, London, UK. The conference was organised by Brunel University and supported by the Italian Union of Thermofluiddynamics, IPEM, the Process Intensification Network, the Institution of Mechanical Engineers, the Heat Transfer Society, HEXAG - the Heat Exchange Action Group, and the Energy Institute, ASME Press, LCN London Centre for Nanotechnology, UCL University College London, UCL Engineering, the International NanoScience Community, www.nanopaprika.eu.Nowadays, extensive attentions have been focussed on the study of induction heating implanted magnetic nanoparticle under AC magnetic field for cancer hyperthermia treatment. Colloidal cluster composed of superparamagnetic nanoparticle has shown great potential for efficient hyperthermia heating. However, the relationship between cluster properties and heating efficiency is not clear. In this work, we investigate the influence of morphology anisotropy of cluster of superparamagnetic nanoparticle on magnetic hysteresis by Monte Carlo simulation. Five kinds of clusters with different shapes and structure are studied. We find that the morphology anisotropy of cluster changes the magnetic loss by affecting the tendency of cluster to remain magnetically aligned with the field orientation. A large aspect ratio of the length of cluster along the field orientation to the width perpendicular to the orientation can increase the amount of energy converted per cycle significantly. Lacking morphology anisotropy will make the magnetic hysteresis of cluster numb to the manipulation of cluster properties
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Parametric effects on dryout of propane in a vertical circular mini-channel
This paper was presented at the 3rd Micro and Nano Flows Conference (MNF2011), which was held at the Makedonia Palace Hotel, Thessaloniki in Greece. The conference was organised by Brunel University and supported by the Italian Union of Thermofluiddynamics, Aristotle University of Thessaloniki, University of Thessaly, IPEM, the Process Intensification Network, the Institution of Mechanical Engineers, the Heat Transfer Society, HEXAG - the Heat Exchange Action Group, and the Energy Institute.This article presents dryout results of propane in a vertical circular mini channel made of stainless steel with an internal diameter of 1.70 mm and a heated length of 245 mm. The experiments are performed at three saturation temperatures of 23 degrees C, 33 degrees C and 43 degrees C. Mass flux is varied from 100 kg/m2s to 500 kg/m2s.The heat flux is increased in steps up to occurrence of dryout. The effect of different parameters such as mass flux, vapour quality and saturation temperature on the dryout heat flux is investigated. The results show that the dryout heat flux increases with the increase in mass flux and with the decrease of vapour quality. Almost no effect of saturation temperature on the dryout heat flux is observed. The generalised CHF correlations developed for macro and micro scale from the literature are compared with experimental results. Correlations developed by Callizo et al. (2008), Bowring (1972) and Katto and Ohno (1984) gave reasonably good predictions
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