Preparation and some physicochemical properties of freeze-dried vegetables carving

Freeze-drying is a very gentle dehydration method to preserve the highest quality and give the final product a longer shelf-life, based on the principle of removing the ice by sublimation. This research aimed to study freeze-dried manufacturing processes of vegetable carving for application in the foodservice industry. Plant materials used in this study were pumpkin, carrot and Chinese radish which were carved into a rose shape. To prepare, all carved-rose vegetables were dipped in 1.0% CaCl2 solution as a firming agent for 5 mins before freeze-dried operations at the temperature of –50°C under vacuum (~30 Pa) for 50 hrs. Dyeing operation was conducted specifically in carved-rose Chinese radish using pink (0.05 and 0.1%) and red (0.05 and 0.1%) food-grade colour after pretreatment with CaCl2 . The results showed that dried carved-rose vegetables had low water activity (0.32-0.42) and moisture content (8.01-11.44%). The physical properties of freeze-dried pumpkin and carrot carving were firmed and presented a spongy texture with small bubbles spread continuously throughout the piece which helps protect the structural collapse. However, carved-rose radish had a slight shrinkage but it was restored as fresh after immersing in water. Rehydration time was 5 mins for pumpkin and carrot, and 10 mins for Chinese radish which showed remarkable that firm-liked fresh vegetables. Then, freeze-dried vegetables were packed in an aluminum bag filled with nitrogen gas and kept at 25±1°C for 2-months storage. The sensory characteristics evaluated by specialists were ranged in the medium to very like throughout the storage periods. Thus, freeze-dried carved-rose vegetable seems to be very interesting, moreover, conduction on a larger scale for the foodservice industry was particularly noticeable.

Design and 3D-model of a dynamic bubble trap for cardiopulmonary bypass

The use of extracorporeal circulation systems (cardiopulmonary bypass pumps, ECMO) can lead to brain and coronary artery microembolism, which significantly reduces postoperative rehabilitation and often leads to severe complications. Microembolism occurs when oxygen or air microbubbles (MBs) enter the arterial system of patients. Existing CPB pumps come with built-in bubble trap systems but cannot remove bubbles in the circuit. ECMO devices have arterial filters but cannot reliably filter out <40 μm bubbles in a wide flow range. We have proposed an alternative method that involves the use of an efficient dynamic bubble trap (DBT) for both large and small bubbles. The design includes development of two DBT variants for hemodynamic conditions of adult and pediatric patients. The device is installed in the CPB pump and ECMO outlet lines. It provides sufficient bubble separation from the lines in a blood flow of 3.0–5.0 L/min for adults and 0.5–2.0 L/min for children. The developed computer models have shown that MBs smaller than 10 μm can be filtered. The use of this device will greatly reduce the likelihood of air embolism and provide the opportunity to reconsider the concept of expensive arterial filters.

Scale-dependent anisotropy, energy transfer and intermittency in bubble-laden turbulent flows

Data from direct numerical simulations of disperse bubbly flows in a vertical channel are used to study the effect of the bubbles on the carrier-phase turbulence. We developed a new method, based on an extension of the barycentric map approach, that allows us to quantify and visualize the anisotropy and componentiality of the flow at any scale. Using this we found that the bubbles significantly enhance anisotropy in the flow at all scales compared with the unladen case, and that for some bubble cases, very strong anisotropy persists down to the smallest scales of the flow. The strongest anisotropy observed was for the cases involving small bubbles. Concerning the energy transfer among the scales of the flow, our results indicate that for the bubble-laden cases, the energy transfer is from large to small scales, just as for the unladen case. However, there is evidence of an upscale transfer when considering the transfer of energy associated with particular components of the velocity field. Although the direction of the energy transfer is the same with and without the bubbles, the behaviour of the energy transfer is significantly modified by the bubbles, suggesting that the bubbles play a strong role in altering the activity of the nonlinear term in the flow. The skewness of the velocity increments also reveals a strong effect of the bubbles on the flow, changing both its sign and magnitude compared with the single-phase case. We also consider the normalized forms of the fourth-order structure functions, and the results reveal that the introduction of bubbles into the flow strongly enhances intermittency in the dissipation range, but suppresses it at larger scales. This strong enhancement of the dissipation-scale intermittency has significant implications for understanding how the bubbles might modify the mixing properties of turbulent flows.

Towards Mechanistic Wall Heat Flux Partitioning Model for Fully Developed Nucleate Boiling

Mechanistic models developed to predict partial nucleate boiling are not adequate for fully developed nucleate boiling due to differences in the prevailing heat transfer governing mechanisms. In place of the mechanistic model, several empirical correlations and semi-mechanistic models have been proposed over the years for the prediction of fully developed nucleate boiling as presented in this study but they are unsuitable for use in computational fluid dynamics (CFD) code. Recently, the simulation of fully developed nucleate boiling has become much more practical because of advancement in a computational method that involves the coupling of the interface capturing method (for slug bubbles) with the Eulerian multi-fluid model (for dispersed spherical bubbles). Nonetheless, there is a need for a mechanistic closure law for the fully developed nucleate boiling phenomenon that would complement this advancement in CFD. Towards this end, a mechanistic wall heat flux partitioning model for fully developed nucleate boiling is proposed in this study. This model is predicated on the hypothesis that a high heat flux nucleate boiling is distinguished by the existence of a liquid macro-layer between the heated wall and the slug or elongated bubbles and that the macro-layer is interspersed with numerous high frequency nucleate small bubbles. With this hypothesis, the heat flux generated on the heated wall is partitioned into two parts: conduction heat transfer across the macro-layer liquid film thickness and evaporation heat flux of the microlayer of the nucleating small bubbles. The proposed model is validated against experimental data.

Bubble PIV technique to measure the velocity field of a free-swimming California sea lion

Fish et al. (2014) adapted laboratory PIV for safe use on larger animals. As opposed to seeding the entire flow with reflective particles and illuminating a plane of the flow with a laser, they produced a sheet of small bubbles and used sunlight for global illumination. Underwater cameras imaged the flow in a method similar to traditional PIV. This technique was used to measure the flow around a swimming dolphin and estimate the thrust produced during a tail stand maneuver (Fish et al. (2014, 2018)). In the current work, we will extend the modification of PIV of Fish et al. to measure the flow produced by a swimming sea lion also using bubbles as seeding particles and sunlight as illumination. This is the first time that the flowfield of a swimming sea lion has been directly measured. We will present an extensive extension to the image processing required to measure flow under field conditions. Finally, we will present the flow generated by propulsive strokes of an adult female (Cali) sea lion freely swimming through a pool of stationary water.

Promoting Effect of Ultra-Fine Bubbles on CO2 Hydrate Formation

When gas hydrates dissociate into gas and liquid water, many gas bubbles form in the water. The large bubbles disappear after several minutes due to their buoyancy, while a large number of small bubbles (particularly sub-micron-order bubbles known as ultra-fine bubbles (UFBs)) remain in the water for a long time. In our previous studies, we demonstrated that the existence of UFBs is a major factor promoting gas hydrate formation. We then extended our research on this issue to carbon dioxide (CO2) as it forms structure-I hydrates, similar to methane and ethane hydrates explored in previous studies; however, CO2 saturated solutions present severe conditions for the survival of UFBs. The distribution measurements of CO2 UFBs revealed that their average size was larger and number density was smaller than those of other hydrocarbon UFBs. Despite these conditions, the CO2 hydrate formation tests confirmed that CO2 UFBs played important roles in the expression of the promoting effect. The analysis showed that different UFB preparation processes resulted in different promoting effects. These findings can aid in better understanding the mechanism of the promoting (or memory) effect of gas hydrate formation.

Modeling of inclusion removal in a tundish by gas bubbling

Inclusion removal from liquid steel by attachment to rising gas bubbles has been reviewed. A mathematical model of inclusion removal by gas bubbling in a tundish has been developed and it is found that minimization of bubble size is critical to enhance removal. However, small bubble formation in a tundish may be problematic as bubble size is controlled by high contact angles between liquid metal and bubble orifice materials. A physical modeling technique has been developed to simulate inclusion removal by tundish bubbling. The influence of a floating particle sink, a flow pattern modifying impact pad, and a bubbler, on particle separation was examined. The influence of gas flow rate, tundish residence time, particle size and bubble size was also examined. Physical modeling confirms that particle separation by gas bubbling in a tundish can be efficient at enhancing inclusion removal. It was also confirmed that relatively small bubbles (<1mm in diameter) are required for maximum separation efficiency.

Modeling of inclusion removal in a tundish by gas bubbling

Inclusion removal from liquid steel by attachment to rising gas bubbles has been reviewed. A mathematical model of inclusion removal by gas bubbling in a tundish has been developed and it is found that minimization of bubble size is critical to enhance removal. However, small bubble formation in a tundish may be problematic as bubble size is controlled by high contact angles between liquid metal and bubble orifice materials. A physical modeling technique has been developed to simulate inclusion removal by tundish bubbling. The influence of a floating particle sink, a flow pattern modifying impact pad, and a bubbler, on particle separation was examined. The influence of gas flow rate, tundish residence time, particle size and bubble size was also examined. Physical modeling confirms that particle separation by gas bubbling in a tundish can be efficient at enhancing inclusion removal. It was also confirmed that relatively small bubbles (<1mm in diameter) are required for maximum separation efficiency.