Numerical Study of CNT Micro Fin Array for Cooling Application

Heat removing from a microelectronic chip packaging has grand effect on performance and durability of the chip. Today's microchips with high power densities would require efficient methods of cooling. Recently, vertical alignment CNTs, due to their superior thermal, electrical and mechanical properties, was suggested as an effective micro cooler on the level of modern electronics demands. In this paper, the cooling performance of the CNT fin structures is studied numerically. Flow of air was considered as the working fluid flow. CFD simulations have been carried out for a series of CNT micro-fin cooling architectures based on one and two dimensional fin array models. The modeling results indicate that fluid speed is the key factor in heat transfer capacity of the device. Also, the results of 2D carbon nanotube fin array model show more precise and greater thermal performance than that of 1D model. Finally, the examination of pressure drop between inlet and outlet of the cooling device is presented as an important factor which could limit the fluid speed and fin height effect on heat sink performance also investigated

Emerging Nano-Theranostic Strategies against Non-Alcoholic Fatty Liver Disease: a review

As a major global cause of liver damage, non-alcoholic fatty liver disease (NAFLD) is associated with excessive hepatocellular accumulation of lipids in the liver, elevated levels of hepatic enzymes,and the fibrotic evidence. The primary therapies for NAFLD are changing lifestyle or managing comorbid-associated diseases. Lately, nanotechnology has revolutionized the art of nanostructure synthesis for disease imaging, diagnosis, and treatment. Loading drugs into nanocarriers hasbeen established as a promising strategy to extend their circulating time, particularly in treating NAFLD. In addition, considering a master modulator of adipogenesis and lysosomal biogenesis and function, designing novel nanostructures for biomedical applications requires using biodegradable materials. Various nanostructures, including inorganic nanoparticles (NPs), organic-based NPs, metallic nanocarriers, biodegradable polymeric nanocarriers, polymer-hybrid nanocarriers, and lipid-based nanocarriers have been designed for NAFLD treatment, which significantly affected serum glucose/lipid levels and liver function indices. NPs modified with polymers, bimetallic NPs, and superparamagnetic NPs have been used to design sensitive nanosensors to measure NAFLD-related biomarkers. However, certain limitations are associated with their use as diagnostic agents. The purpose of this review article is to shed light on the recent advancements in the field of nanomedicine for the early diagnosis, treatment, and prognosis of this progressive liver disease

Effect of Source Solution Components on Quality of Electrospun PVDF Nanofibers for Nanogenerator Application

High surface area flexible thin films of Polyvinylidene Difluoride (PVDF) nanofibers are vastly used because of low cost, simple, safety and environmentally friendly production methods. PVDF nanofibers are inherently piezoelectric when produced by high voltage electrospinning method. In this paper, PVDF nanofibers are synthesis in a electrospinning apparatus, using a solution that contains PVDF dissolved in two solvents, THF (Tetrahydroforan) and DMF (N,N-Di-Methyl Formamid), which DMF has a higher boiling point than THF. The effects of THF to DMF ratio in the solution, and also, PVDF concentration on the morphology and diameter of the synthesised nanofibers are studied. Field emission scanning electron microscopy analysis of the nanofiber thin films indicates that by adding THF in the source suspension, smoother and more uniform nanofibers with lower diameter are resulted. However, by further increasing THF ratio, the cone-jet mode is formed on the tip of the needle, rapidly dried, before reaching the collector substrate. Results of the further experiments indicate that decreasing of PVDF concentration in the deposition source solves the latter problem. On the other hand, by decreasing the THF ratio to DMF, the solution cannot completely be dried, before collecting by the substrate. The best and uniform nanofibers with the diameter of 200 to 300 nm are obtained from a ratio of 3:1 For THF:DMF and 10 % PVDF concentration. Fabricated nanogenerator, based on the best mentioned sample, shows an output power of 0.56 W/m2 when actuated by a vibration mechanical force with the frequency of 8 Hz

Investigation of the Effect of Nanoparticles Mean Diameter on Turbulent Mixed Convection of a Nanofluid in a Horizontal Curved tube Using a Two Phase Approach

Turbulent mixed convection of a nanofluid (water/Al2O3, Φ=.02) has been studied numerically. Two-phase mixture model has been used to investigate the effects of nanoparticles mean diameter on the flow parameters. Nanoparticles distribution at the tube cross section shows that the particles are uniformly dispersed. The non-uniformity of the particles distribution occurs in the case of large nanoparticles and/or high value of the Grashof numbers. The study of particle size effect showed that the effective Nusselt number and turbulent intensity increases with the decreased of particle size

Thermodynamic analysis and optimization of solar desalination unit, using humidification-dehumidification cycle usable in remote waterless areas by applying doe method

Paper presented at the 7th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Turkey, 19-21 July, 2010.ej201

Performance of Potassium Bicarbonate and Calcium Chloride Draw Solutions for Desalination of Saline Water Using Forward Osmosis

Forward osmosis (FO) has recently drawn attention as a promising membrane based method for seawater and brackish water desalination. In this study, we focus on the use of calciun chloride (CaCl2) and potassium bicarbonate (KHCO3) as inorganic salt draw solution candidates due to their appropriate performance in water flux and reverse salt diffusion as well as reasonable cost. The experiments were carried at 25 °C and cross-flow rate of 3 L min−1.  At the same osmotic pressure, the water flux of CaCl2 draw solution tested against deionized feed water, showed 20% higher permeation than KHCO3, which it was attributed to the lower internal concentration polarization (ICP). The reverse diffusion of CaCl2 was found higher than KHCO3 solution which it would be related to the smaller ionic size and the higher permeation of this salt through the membrane. The water flux for both draw solutions against 0.33 M NaCl feed solution was about 2.8 times lower than deionized feed water because of ICP. Higher concentrations of draw solution is required for increasing the water permeation from saline water feed towards the draw side

Numerical Study of Operating Pressure Effect on Carbon Nanotube Growth Rate and Length Uniformity

Chemical Vapor Deposition (CVD) is one of the most popular methods for producing Carbon Nanotubes (CNTs). The growth rate of CNTs based on CVD technique is investigated by using a numerical model based on finite volume method. Inlet gas mixture, including xylene as carbon source and mixture of argon and hydrogen as carrier gas enters into a horizontal CVD reactor at atmospheric pressure. In this article the operating pressure variations are studied as the effective parameter on CNT growth rate and length uniformity

ICHMT2014-XXXX Investigation of CNT Growth Regimes in a Tubular CVD Reactor Considering Growth Temperature

Abstract In Carbon nanotube (CNT) growth process via Chemical vapor deposition (CVD) method, there are two distinct regimes based on growth temperatures, so called mass transfer controlled and surface reaction controlled regimes, which represent different type of behaviour in growth. Operating in each regime has different characteristic that can influence on other operating condition effects on CNTs growth. Thus study of these regimes is important for better understanding of CNTs growth; also it helps to control of other operating conditions effect on growing CNTs. In this paper these two regimes is established and then relevant processes in reactor is studied in details. Results show that CNTs total production in mass transfer controlled regime has higher order and less sensitivity to the growth temperature compared to surface reaction controlled regime. Also produced CNTs in mass transfer controlled regime has less length uniformity compared to surface reaction controlled regime

An improved thermal and electrical model for a solar photovoltaic thermal (PV/T) air collector

In this paper, an attempt is made to investigate the thermal and electrical performance of a solar photovoltaic thermal (PV/T) air collector. A detailed thermal and electrical model is developed to calculate the thermal and electrical parameters of a typical PV/T air collector. The thermal and electrical parameters of a PV/T air collector include solar cell temperature, back surface temperature, outlet air temperature, open-circuit voltage, short-circuit current, maximum power point voltage, maximum power point current, etc. Some corrections are done on heat loss coefficients in order to improve the thermal model of a PV/T air collector. A better electrical model is used to increase the calculations precision of PV/T air collector electrical parameters. Unlike the conventional electrical models used in the previous literature, the electrical model presented in this paper can estimate the electrical parameters of a PV/T air collector such as open-circuit voltage, short-circuit current, maximum power point voltage, and maximum power point current. Further, an analytical expression for the overall energy efficiency of a PV/T air collector is derived in terms of thermal, electrical, design and climatic parameters. A computer simulation program is developed in order to calculate the thermal and electrical parameters of a PV/T air collector. The results of numerical simulation are in good agreement with the experimental measurements noted in the previous literature. Finally, parametric studies have been carried out. Since some corrections have been down on thermal and electrical models, it is observed that the thermal and electrical simulation results obtained in this paper is more precise than the one given by the previous literature. It is also found that the thermal efficiency, electrical efficiency and overall energy efficiency of PV/T air collector is about 17.18%, 10.01% and 45%, respectively, for a sample climatic, operating and design parameters.Solar photovoltaic thermal (PV/T) air collector Computer simulation