Mathematical Modeling for Nanofluids Simulation: A Review of the Latest Works

Exploiting nanofluids in thermal systems is growing day by day. Nanofluids having ultrafine solid particles promise new working fluids for application in energy devices. Many studies have been conducted on thermophysical properties as well as heat and fluid flow characteristics of nanofluids in various systems to discover their advantages compared to conventional working fluids. The main aim of this study is to present the latest developments and progress in the mathematical modeling of nanofluids flow. For this purpose, a comprehensive review of different nanofluid computational fluid dynamics (CFD) approaches is carried out. This study provides detailed information about the commonly used formulations as well as techniques for mathematical modeling of nanofluids. In addition, advantages and disadvantages of each method are rendered to find the most appropriate approach, which can give valid results

Numerical Investigation of Heat Transfer Enhancement in a Rectangular Heated Pipe for Turbulent Nanofluid

Thermal characteristics of turbulent nanofluid flow in a rectangular pipe have been investigated numerically. The continuity, momentum, and energy equations were solved by means of a finite volume method (FVM). The symmetrical rectangular channel is heated at the top and bottom at a constant heat flux while the sides walls are insulated. Four different types of nanoparticles Al2O3, ZnO, CuO, and SiO2 at different volume fractions of nanofluids in the range of 1% to 5% are considered in the present investigation. In this paper, effect of different Reynolds numbers in the range of 5000 < Re < 25000 on heat transfer characteristics of nanofluids flowing through the channel is investigated. The numerical results indicate that SiO2-water has the highest Nusselt number compared to other nanofluids while it has the lowest heat transfer coefficient due to low thermal conductivity. The Nusselt number increases with the increase of the Reynolds number and the volume fraction of nanoparticles. The results of simulation show a good agreement with the existing experimental correlations

Heat transfer and friction loss analysis of non-wood fiber suspensions in closed conduit flow / Samira Gharehkhani

Study of the behavior of pulp fiber suspension flow is one of the most significant scientific interests as addition of small amount of fiber to the water changes the flow behavior considerably. Pulp and paper mills are the major industries using the fiber suspensions. However, the tendency of using non-wood fibers as one of the alternative sources is going to be increased, the lack of knowledge about the non-wood fiber suspension flow in pipe raised some concerns regarding the handle of non-wood pulp suspension in different processes. There is no significant reporting about non- wood pulp suspension flow in the pipelines. Therefore, the investigation of the non-wood fiber suspension in pipe flow, such as heat transfer and pressure drop trends seem necessary to obtain. A set up was built in order to evaluate the heat transfer and pressure drop characteristics of flowing pulp fiber suspensions. A number of experiments were conducted for different types of non-wood pulp fibers (Kenaf, Rice straw and Empty fruit bunches fibers). The results show that most of the fiber and paper properties could be correlated with both hc and pressure drop data. Using this strategy, the papermakers can predict and monitor the paper quality at the stock delivery step (delivery pipe). In order to investigate another objective of this study, a series of experiments were performed to examine the effect of presence of additives e.g. cationic polyacrylamide (CPAM), potato starch and nanocrystalline cellulose (NCC) in pulp suspension on pressure loss and drag reduction phenomena. Among these polymers the hydrodynamic behavior of NCC as a new generation of additives is less known and there is no any report on pipe flow behavior of NCC/pulp mixture. The results revealed that the pulp mixture containing 150 ppm NCC produced higher drag reduction level than pulp suspension alone. The findings in present work can shed light on flow mechanism of non-wood fibers suspensions and their mixtures with polymers in pipe flow

Heat transfer enhancement of turbulent nanofluid flow over various types of internally corrugated channels

A numerical study is carried out to investigate the effects of different geometrical parameters and various nanofluids on the thermal performance of rib-grooved channels under uniform heat flux. The continuity, momentum and energy equations are solved by using the finite volume method (FVM). Three different rib-groove shapes are studied (rectangular, semi-circular and trapezoidal). Four different types of nanoparticles, Al2O3, CuO, SiO2 and ZnO with different volume fractions in the range of 1% to 4% and different nanoparticle diameters in the range of 20nm to 60nm, are dispersed in the base fluids such as water, glycerin and ethylene glycol. The Reynolds number varies from 5000 to 25,000. To optimize the shape of rib-groove channels different rib-groove heights from 0.1Dh (4mm) to 0.2Dh (8mm) and rib-groove pitch from 5e (20mm) to 7e (56mm) are examined. Simulation results reveal that the semi-circular rib-groove with height of 0.2Dh (8mm) and pitch equals to 6e (48mm) has the highest Nusselt number. The nanofluid containing SiO2 has the highest Nusselt number compared with other types. The Nusselt number rises as volume fraction increases, and it declines as the nanoparticle diameter increases. The glycerin-SiO2 nanofluid has the best heat transfer compared to other base fluids. It is also observed that in the case of using nanofluid by changing parameters such as nanoparticle diameter, volume fraction and base fluids the skin friction factor has no significant change

Recent Advances in Cellulose Nanofibers Preparation through Energy-Efficient Approaches: A Review

Cellulose nanofibers (CNFs) and their applications have recently gained significant attention due to the attractive and unique combination of their properties including excellent mechanical properties, surface chemistry, biocompatibility, and most importantly, their abundance from sustainable and renewable resources. Although there are some commercial production plants, mostly in developed countries, the optimum CNF production is still restricted due to the expensive initial investment, high mechanical energy demand, and high relevant production cost. This paper discusses the development of the current trend and most applied methods to introduce energy-efficient approaches for the preparation of CNFs. The production of cost-effective CNFs represents a critical step for introducing bio-based materials to industrial markets and provides a platform for the development of novel high value applications. The key factor remains within the process and feedstock optimization of the production conditions to achieve high yields and quality with consistent production aimed at cost effective CNFs from different feedstock

The effect of nanocrystalline cellulose on flow properties of fiber crop aqueous suspension

Nanocrystalline cellulose (NCC) a nature-based material, has gained significant attentions for its unique properties. The present study aims to investigate the flow behavior of cellulosic suspension containing non-wood pulp fibers and NCC, by means of rheological and pressure drop measurements. The NCC sample was prepared by sulfuric acid hydrolysis from Acacia mangium fibers. The rheological properties of kenaf/NCC suspensions were studied using viscosity and yield stress measurements. The pressure drop properties of the suspension flow were studied with respect to variation in flow velocity (0.4 m/s–3.6 m/s) and the NCC concentration (70 mg/l and 150 mg/l). The pressure drop results showed that the pulp suspension containing 150 mg/l NCC had higher drag reduction than kenaf suspension alone. The present insights into the flow of pulp/NCC suspension provide a new data and promote the application of NCC in industries