Energetic and Exergetic Performances of Plate Heat Exchanger Using Brine-Based Hybrid Nanofluid for Milk Chilling Application

Abstract

Theoretical study on the energetic and exergetic performances of a counter-flow corrugated plate heat exchanger using hybrid nanofluids for the milk chilling application has been done in the present investigation. Magnesia-silver and Alumina-silver nanoparticles have been dispersed in the ethylene glycol–water mixture and propylene glycol–water mixture (20:80 brine solutions) with different particle volume concentration separately. Effect of particle volume concentration and flow rate of the hybrid nanofluid on the heat transfer rate, convective, and overall heat transfer coefficients, mass flow rate of milk, pressure drop, pumping power, entropy generation rate, second law efficiency, irreversibility, irreversibility distribution ratio, non-dimensional exergy (NDE) destruction, and performance index have been studied. It has been observed that heat transfer rate, convective and overall heat transfer coefficients, pressure drop, pumping power, irreversibility, entropy generation rate, second law efficiency, and milk flow rate increase; while NDE destruction, performance index, and irreversibility distribution ratio decrease with the hybrid nanofluid flow rate and the volume concentration of the nanofluid. Within studied ranges, the hybrid nanofluid yields the maximum improvement of heat transfer rate and convective heat transfer coefficient of about 1.6% and 9.4%, respectively, compared to base fluid. It has also been found that silver?+?alumina shows slightly better performance improvement and hence hybrid nanofluid is recommended as a suitable alternative for the milk chilling units.     

Carbon nano-onions for imaging the life cycle of Drosophila melanogaster

Real-time X-ray or magnetic resonance imaging are known methods used for biomedical diagnosis. By the oral administration of barium meal, X-ray imaging can be extended for use in soft tissue imaging. The oral ingestion of a fluorescent probe is a new approach to imaging a living species. Here, water-soluble carbon nano-onions are introduced as a nontoxic, fluorescent reagent enabling Drosophila melanogaster (fruit flies) to be imaged alive. It is demonstrated that these water-soluble carbon nano-onions, synthesized from wood waste, colorfully image all the development phases of Drosophila melanogaster from its egg to adulthood. Oral ingestion of up to 4 ppm of soluble carbon nano-onions allows the optical fluorescence microscopy imaging of all the stages of the fruit fly life cycle without showing any toxic effects. The fluorescent Drosophila melanogaster excretes this fluorescing material upon the withdrawal of carbon nano-onions from its food.     

Electron beam induced synthesis of CdSe nanomaterials: Tuning of shapes from rods to cubes

Cadmium selenide (CdSe) nanomaterials of different shapes have been synthesized in the water pool of the water-in-oil microemulsions through 7 MeV electron beam irradiation. The rod shaped CdSe nanomaterials of lengths and breadths up to 1 μm and 200 nm, respectively with aspect ratios from 3 to 5 were grown in the case of microemulsions containing lower water content, water to surfactant concentrations ratio, w₀ = 10. In contrast, the cubic shaped CdSe nanomaterials of dimensions about 100 nm were formed in the microemulsions with higher water contents, w₀ values from 20 to 40. Such a transformation of shape from rod to cube was attributed to the change in the hydrophobicity and hydrophilicity of the micro-environment in the microemulsions. The as-grown CdSe nanomaterials were stable at ambient conditions and thus expected to be very useful in the device applications.     

Wiener chaos expansions for estimating rain-flow fatigue damage in randomly vibrating structures with uncertain parameters

The problem of estimating the fatigue damage in randomly vibrating structures with uncertain parameters is considered. The loadings are assumed to be stationary and Gaussian. The corresponding accumulated fatigue damage is described through the rain-flow cycle counting algorithm. For stationary and ergodic loads, the accumulated rain-flow fatigue damage can be estimated if the system and the load spectrum are known. However, these estimates would be erroneous if the structure properties and/or the spectrum parameters of the loading are significantly uncertain. Corrections to account for the parameter uncertainties is usually obtained using the Gauss error propagation formula, and is accurate for small parameter variations. An alternative approach based on Wiener chaos expansions is employed to estimate the rain-flow fatigue damage in linear/nonlinear structural systems with parameter uncertainties. The performance of the proposed approach is compared with the Gauss error propagation formula. The proposed method is illustrated through fatigue damage estimation of three simplified examples involving a moving vehicle on a rough road, Morison’s force due to random sea waves and the blade of a wind turbine.     

Soy isoflavone genistein induces cell death in breast cancer cells through mobilization of endogenous copper ions and generation of reactive oxygen species

Scope: Worldwide geographical variation in cancer incidence indicates a correlation between dietary habits and cancer risk. Epidemiological studies have suggested that populations with high isoflavone intake through soy consumption have lower rates of breast, prostate, and colon cancer. Isoflavone genistein in soybean is considered a potent chemopreventive agent against cancer. Although several mechanisms have been proposed, a clear anticancer action mechanism of genistein is still not known. Methods and results: Here, we show that the cytotoxic action of genistein against breast cancer cells involves mobilization of endogenous copper. Further, whereas the copper specific chelator neocuproine is able to inhibit the apoptotic potential of genistein, the molecules which specifically bind iron (desferroxamine mesylate) and zinc (histidine) are relatively ineffective in causing such inhibition. Also, genistein‐induced apoptosis in these cells is inhibited by scavengers of reactive oxygen species (ROS) implicating ROS as effector elements leading to cell death. Conclusions: As copper levels are known to be considerably elevated in almost all types of cancers, in this proof‐of‐concept study we show that genistein is able to target endogenous copper leading to prooxidant signaling and consequent cell death. We believe that such a mechanism explains the anticancer effect of genistein as also its preferential cytotoxicity towards cancer cells.     

The potential of wind electricity generation in Bangladesh

The hourly wind speed data of the coastal station Chittagong have been collected for the years 1978–1981. From the hourly average wind speed, the hourly and monthly energy outputs were computed for three commercial machines (22 kW, 16 kW and 4 kW) having different cut-in wind speed. The 22 kW machine was found to produce higher energy output per m² than the other two for our energy regime. The hourly and monthly energy variation of the 22 kW machine was studied and the cost per kWh of energy produced by this machine was obtained. Considering the wind speed distribution of Bangladesh, it appears that a wind machine in combination with a conventional diesel back up system will be economically viable for electricity generation in the off-shore islands but not in inland locations.     

Spatial Variation of Convective Heat Transfer Coefficient in Air Impingement Applications

ABSTRACT Spatial variation of heat transfer is an important factor in air impingement systems. Temperature data were obtained when a jet at room temperature impinged on a flat object initially at −50 °C to estimate heat transfer under freeze-thaw conditions. Single and double circular jets and slot jets were examined. Temperature data were fit into empirical relationships for predicting heat transfer coefficients and their spatial variation for conditions common in impingement freeze-thaw applications. For processing conditions involving cooling, the impingement surface was initially heated to a temperature of 70 °C and allowed to cool when subjected to impingement with room temperature air.     

Low-pressure pneumatic muscles: development,phenomenological modeling,and evaluation in assistive applications through sEMG analysis

Compliant actuators have received much attention from researchers over the last two decades. Specifically, pneumatic artificial muscles (PAMs) have been used in several human-in-loop assistive and rehabilitative devices due to their inherent behavior resembling biological muscles. We presented a lucid customizable fabrication process to develop low-pressure actuated PAMs, named pneumatic silicone tube artificial muscles (pSTAMs), and to cater activity-specific actuator requirements. Two constructions of pSTAMs with varying lengths were rigorously experimented at different pressure-load conditions for their isobaric static and stiffness characterizations. Estimation of bandwidth and use of empirical correction factors in the conventional analytical models for quasi-static characterization of pSTAMs were demonstrated. Lumped parameter-based phenomenological model was employed to closely model their dynamic characteristics. A detailed integrated electromyography analysis with surface electromyography signals from the targeted muscle groups was performed to determine the efficacy of using pSTAMs in two activities.

     

Transient torque reversals in indirect drive wind turbines

The adverse effect of transient torque reversals (TTRs) on wind turbine gearboxes can be severe due to their magnitude and rapid occurrence compared with other equipment. The primary damage is caused to the bearings as the bearing loaded zone rapidly changes its direction. Other components are also affected by TTRs (such as gear tooth); however, its impact on bearings is the largest. While the occurrence and severity of TTRs are acknowledged in the industry, there is a lack of academic literature on their initiation, propagation and the associated risk of damage. Furthermore, in the wide range of operation modes of a wind turbine, it is not known which modes can lead to TTRs. Further, the interdependence of TTRs on environmental loading like the wind is also not reported. This paper aims to address these unknowns by expanding on the understanding of TTRs using a high-fidelity numerical model of an indirect drive wind turbine with a doubly fed induction generator (DFIG). To this end, a multibody model of the drivetrain is developed in SIMPACK. The model of the drivetrain is explicitly coupled to state-of-the-art wind turbine simulator OpenFAST and a grid-connected DFIG developed in MATLAB®'s Simulink® allowing a coupled analysis of the electromechanical system. A metric termed slip risk duration is proposed in this paper to quantify the risk associated with the TTRs. The paper first investigates a wide range of IEC design load cases to uncover which load cases can lead to TTRs. It was found that emergency stops and symmetric grid voltage drops can lead to TTRs. Next, the dependence of the TTRs on inflow wind parameters is investigated using a sensitivity analysis. It was found that the instantaneous wind speed at the onset of the grid fault or emergency shutdown was the most influential factor in the slip risk duration. The investigation enables the designer to predict the occurrence of TTRs and quantify the associated risk of damage. The paper concludes with recommendations for utility-scale wind turbines and directions for future research.