Innovative Heat Transfer Fluids Research Articles

Exploration of 3D stagnation-point flow induced by nanofluid through a horizontal plane surface saturated in a porous medium with generalized slip effects

Heat transfer enhancement is a contemporary challenge in a variety of fields such as electronics, heat exchangers, bio and chemical reactors, etc. Nanofluids, as innovative heat transfer fluids, have the potential to be an efficient tool for increasing energy transport. This benefit is obtained as a result of an enhancement in effective thermal conductivity and an alteration in the dynamics of fluid flow. Thus, this paper is concerned with heat transfer enhancement via nanofluids. The intention is to find numerical double solutions to the 3D stagnation-point flow (SPF) and heat transfer incorporated nanoparticles in a porous medium with generalized slip impacts. Appropriate similarity variables are used to non-dimensionalize the leading equations, which are then numerically solved using the three-stage Lobatto IIIa integration formula. The impacts of different parameters on the dynamics of flow and characteristics of heat transfer induced by nanofluids in the presence of an unsteady parameter, nanoparticle volume fraction, velocity slip parameter, and porosity parameter are investigated. Based on the latest findings, it is closed that the velocity slip improves the heat transfer as well as shear stress in the axial direction in both solutions, while the shear stress behaves oppositely in the respective lateral direction. In addition, the velocity profile remarkably enriches for both branch solutions, while the temperature distribution elevates for the upper branch and declines for the lower branch owing to the larger porosity parameter.

Carboxymethyl Cellulose Based Second Grade Nanofluid around a Horizontal Circular Cylinder

Modern challenges include improving heat transmission in a range of industries, including electronics, heat exchangers, bio and chemical reactors, etc. Innovative heat transfer fluids like nanofluids have the potential to increase energy transport effectively. This gain is attained as a result of improved effective thermal conductivity and modified fluid flow dynamics. Therefore, the topic of this paper is improving heat transmission using nanofluids. The objective is to deal with the second grade fluid model passing through a horizontal circular cylinder with mixed convection and suspended nanoparticles. The respective nanoparticles and based fluid of Copper (Cu) and carboxymethyl cellulose (CMC-water) are considered. Both non-dimensional and non-similarity transformation variables are utilized to convert the governing equations to a system of partial differential equations (PDEs). Reduction to ordinary differential equations (ODEs) is attained from the resulting PDEs at the lower stagnation area and then tackled via the Runge-Kutta Fehlberg technique (RKF45) in the Maple software. Graphs are used to illustrate the detailed description of the results of dimensionless parameters like the Biot number, mixed convection, and the second grade parameter. Results show that the fluid slows down while the temperature increases as the value of second grade parameter rises.

Feature of metallic oxide nanoparticles in the thermal efficiency and flow structure of non-Newtonian homogeneous nanofluid: experimental data-based mathematical approach

Nanofluids are innovativeheat transfer fluids with superior thermophysical properties and have numerous engineering applications in several necessary fields. Keeping this in mind, the flow characteristics of non-Newtonian nanofluids over moving flat surfaces are discussed. We use nanofluids that are synthessed by dispersing the nanoparticles SiO2, TiO2, and MgO with (20–30 nm, 60–70 nm), (30, 50 nm) and (20 nm, 40 nm) particle diameters, respectively, in ethylene glycol-based fluid, including 5%, 10%, 15%, and 20% nanoparticle volume fraction. Mathematical modeling is demonstrated by continuity, momentum, heat equations, and parameters of the rheological model are associated with the viscosity-shear rate relation that follows the experimental results. We consequently explore velocity and temperature profiles through graphs under the impact of distinct nanoparticle volume fractions and diameters. The heat transfer rate and shear stress at the wall are investigated under different nanoparticle volume fractions. Furthermore, we have investigated and understood the behavior of mass flow rate and momentum flux through displacement and momentum thickness parameters. The results revealed that velocity is decreased due to increased viscosity and deficiency in mass and momentum flow rates with the enhancement in nanoparticle concentration.

Thermal performance of nanomaterial in solar collector: State-of-play for graphene

Several studies have performed various nanomaterials for the dispersion of working fluids, including copper oxide, alumina, and silica, and so forth in solar collectors. In this present study thermal performance of graphene nanofluid and hybrid, nanofluid has been considered mostly. The thermo-physical properties of the working fluid are significantly enhanced and the performance of solar collectors is therefore improved. This study summarizes the performance of different solar collectors using carbon-based nanofluids especially graphene. The influence of nanofluid concentration, temperature, and flow rate on the collector efficiency of the solar collectors was highlighted. Using graphene thermal conductivity increase by 17% sharp and using graphene derivatives develop almost a 40% increase. Viscosity enhances almost 50% by using graphene nanoparticles. By the way, graphene has stable properties, cheap in price, using a fluid flow mechanism in thermal collector graphene nanoparticles gives an excellent result. The most important and highlighted inherent properties of graphene are its contact angle which is responsible for conductivity. Higher surface area to volume production improves the heat transfer capacity of graphene nanofluids. In this review, the article elaborates on the graphene and graphene-based nanofluid superiority in the thermal solar collector. Graphene nanofluids perform a crucial role in the development of newer technologies ideal for thermal solar systems. This advanced type of graphene nano liquid has a strong potential for use in medium-temperature systems, for example, solar collectors, as innovative heat transfer fluids.

Enhancement of heat transfer in radiator using copper oxide nano fluids

Many industries requires higher cooling rate for equipment which intern affects the life and efficiency of the equipment. However fluids have limited rate of heat transfer through material. Has limitation for developing higher amount of heat transfer per unit time for cooling purpose. Nano fluids are prepared by separating nano particles in base fluid such as water, oil etc. which is used for higher amount of heat transfer per unit time. Innovative heat transfer fluids are synthesized by suspending metal oxide nano size solid particles. Experiments on nanofluid shown that it has higher thermal conductivity compared to its base fluid. These nano sized particles which are suspended in fluid changes thermal motion between different particles of fluid which increases the amount of heat transfer per unit time. As can be seen from the literature extensive research work is done on aluminium oxide–water and Copper oxide–water nano fluids. In this research utilized nanoparticles as CuO (copper oxide) as it has enormous thermal conductivity, had prepared CuO nanoparticles followed by nanofluid preparation. This article deals entirely about Copper oxide nanofluid with distilled water as base fluid, sodium dodecyl sulphate as surfactant and the percentage increment of amount of heat transfer per unit time of nano fluid is higher than that of base fluid and sample size found by X-Ray diffraction (XRD).

Temperature dependence of thermophysical and rheological properties of seven vegetable oils in view of their use as heat transfer fluids in concentrated solar plants

Selecting a heat transfer fluid (HTF) depends on the value of thermophysical parameters. In response to the need for innovative heat transfer fluids in concentrated solar power (CSP) plants, vegetable oil offers a promising solution. The relevant thermophysical properties are density, thermal conductivity and specific heat capacity. Moreover, a rheological property, the dynamic viscosity is also relevant. The objective of this work was to study and compare these properties for seven different vegetable oils (rapeseed, soybean, sunflower, palm, copra, cotton and jatropha) in the temperature range from ambient to 250°C. For all the properties studied, the values evolved with increasing temperature and were influenced by the fatty acid composition of each vegetable oil. Experimental results are compared with those in the literature and are found to be consistent. The temperature dependencies are correlated to temperature using polynomial equations. The correlations presented here may be useful as a database for the selection of innovative heat transfer fluids.

Temperature dependence of thermal conductivity of vegetable oils for use in concentrated solar power plants, measured by 3omega hot wire method

Following the growing need for innovative heat transfer fluids in concentrated solar power (CSP) plants, the thermal conductivities of different vegetable oils (rapeseed, soybean, sunflower, palm, copra, cotton and jatropha) were measured in the temperature range from ambient to 230 °C relative to a reference oil. The small differences in the obtained thermal conductivities are influenced by the fatty acid composition. For balanced saturated/unsaturated fatty acids composition, the average thermal conductivity decreases from 0.167 Wm−1K−1 at 20 °C to 0.137 Wm−1K−1 at 230 °C. The use of a reference synthetic oil makes the calibration of the thermal probe unnecessary. The used method is based on a hot wire thermal probe with ac excitation and 3ω lock-in detection and has a long-term relative error of 1.2% and absolute accuracy of 2%. It allows measuring in real-time, continuously and independently, the thermophysical properties of oils for thermal applications.

Preparation, characterization, viscosity, and thermal conductivity of nitrogen-doped graphene aqueous nanofluids

Nanofluids perform a crucial role in the development of newer technologies ideal for industrial purposes. In this study, Nitrogen-doped graphene (NDG) nanofluids, with varying concentrations of nanoparticles (0.01, 0.02, 0.04, and 0.06 wt%) were prepared using the two-step method in a 0.025 wt% Triton X-100 (as a surfactant) aqueous solution as a base. Stability, zeta potential, thermal conductivity, viscosity, specific heat, and electrical conductivity of nanofluids containing NDG particles were studied. The stability of the nanofluids was investigated by UV–vis over a time span of 6 months and concentrations remain relatively constant while the maximum relative concentration reduction was 20 %. The thermal conductivity of nanofluids was increased with the particle concentration and temperature, while the maximum enhancement was about 36.78 % for a nanoparticle loading of 0.06 wt%. These experimental results compared with some theoretical models including Maxwell and Nan’s models and observed a good agreement between Nan’s model and the experimental results. Study of the rheological properties of NDG nanofluids reveals that it followed the Newtonian behaviors, where viscosity decreased linearly with the rise of temperature. It has been observed that the specific heat of NDG nanofluid reduced gradually with the increase of concentration of nanoparticles and temperature. The electrical conductivity of the NDG nanofluids enhanced significantly due to the dispersion of NDG in the base fluid. This novel type of fluids demonstrates an outstanding potential for use as innovative heat transfer fluids in medium-temperature systems such as solar collectors.

Nanostructured phase-changeable heat transfer fluids

AbstractCooling is one of the most important technique challenges faced by a range of diverse industries and military needs. There is an urgent need for the innovative heat transfer fluids with improved thermal properties over the currently available. This review paper discusses the concept of using phase-changeable nanoparticles to increase the effective heat capacity and the heat transfer rate of the fluid. A large amount of heat can be absorbed or released when these nanoparticles undergo phase transition from solid to liquid or liquid to gas or vice versa and, thus, enhancing the heat transfer rate. Two types of phase-change fluids are introduced: one contains liquid nanodroplets that will evaporate at elevated temperatures or solidifies at reduced temperatures, called “nanoemulsion fluids”; the other is suspensions of solid-liquid metallic phase-change nanoparticles. The material synthesis and property characterizations of these phase-changeable fluids are two main aspects of this paper. The explosive vaporization of the dispersed nanodroplets would significantly improve the heat transfer in the nanoemulsion fluid. The solid-liquid metallic phase-change nanoparticles will increase the effective heat capacity and thermal conductivity of the base fluids simultaneously. This paper also identifies the several critical issues in the phase-changeable fluids to be solved in the future.

A new solution for reduced sedimentation flat panel solar thermal collector using nanofluids

The present paper reports the experimental results and the potential performance of the investigation on flat solar thermal collectors using nanofluids as innovative heat transfer fluids for solar energy applications. The straight use of heat-transfer nanofluids in traditional solar flat panel revealed some technical issues, due to the nanoparticles sedimentation. Therefore, sedimentation has been investigated both in standard solar flat panels and modified ones made from transparent tubes. The results of the first tests showed that the main sedimentation parameter is the flow velocity and to better control it a standard flat panel was modified changing the cross-section of the lower and top header of the panel, that have been tapered to keep constant the fluid axial velocity. The modification of the panel shape (patent pending) enabled a negligible particles deposit.After different nanofluids were tested on the panel prototype, water–Al2O3 was chosen as heat transfer fluid. All tested nanofluids were prepared in batch and their thermal conductivity and convective heat transfer coefficient were measured prior of their use as heat transfer fluid in the solar panel. A thermal conductivity enhancement up to 6.7% at a concentration of 3vol% was observed, while the convective heat transfer coefficient increased up to 25%.

Study of Iron Nanopowders into Fluids of Industrial Lubrication

The machines and equipment has required increasing performance of lubricating fluids and coolants which plays important role on reducing friction with the metal parts and heat extraction. Viscosity and thermal conductivity are the most important properties of lubricants, in relation to the friction between the fluid molecules. This paper presents two useful models to predict this properties and their relation with the particles volume fraction and temperature in the nanofluid formed by adition of iron or particles produced by friction. Nanofluids are innovative heat transfer fluids with superior potential for enhancing the heat transfer performance of conventional fluids. In this paper the Unit Cell Model (UCM) which considers the Brownian movement experienced by the nanoparticles are adapt to predict the increment of thermal conductivity of iron nanopowders and standard lubrication oil. The viscosity of the nanofluids was adapt from a model usually suitable for predict the effective viscosity of emulsions. Model results indicated a strong effect of the particle size and volume fractions on the increment of thermal conductivity.

Al2O3-based nanofluids: a review

Ultrahigh performance cooling is one of the important needs of many industries. However, low thermal conductivity is a primary limitation in developing energy-efficient heat transfer fluids that are required for cooling purposes. Nanofluids are engineered by suspending nanoparticles with average sizes below 100 nm in heat transfer fluids such as water, oil, diesel, ethylene glycol, etc. Innovative heat transfer fluids are produced by suspending metallic or nonmetallic nanometer-sized solid particles. Experiments have shown that nanofluids have substantial higher thermal conductivities compared to the base fluids. These suspended nanoparticles can change the transport and thermal properties of the base fluid. As can be seen from the literature, extensive research has been carried out in alumina-water and CuO-water systems besides few reports in Cu-water-, TiO2-, zirconia-, diamond-, SiC-, Fe3O4-, Ag-, Au-, and CNT-based systems. The aim of this review is to summarize recent developments in research on the stability of nanofluids, enhancement of thermal conductivities, viscosity, and heat transfer characteristics of alumina (Al2O3)-based nanofluids. The Al2O3 nanoparticles varied in the range of 13 to 302 nm to prepare nanofluids, and the observed enhancement in the thermal conductivity is 2% to 36%.