Type Of Base Fluid Research Articles

The Effect of Base Fluid Type in Nanofluids for Heat Transfer Enhancement in Microtubes

In this paper, single phase model was used to investigate the effect of base fluid in enhancing the heat transfer for forced convection flow of SiO2 in microtube. Four different types of base fluid such as water, ethylene glycol, engine oil and glycerin were used in this investigation. Reynolds number used was ranged from 10 to 120. The results are presented in terms of axial and wall temperature along the tube radius and tube axis, axial velocity and Nusselt number. The result shows that the glycerin has the highest Nusselt number followed by engine oil, ethylene glycol then water.

Numerical and model validation of uncovered nanofluid sheet and tube type photovoltaic thermal solar system

In this paper, an experimental and numerical study is performed to evaluate the performance of a photovoltaic thermal (PV/T) nanofluid based collector. A two-dimensional numerical model is established to study the effects of using nanofluids as working fluid in PV/T collector. The model is validated experimentally by comparing the simulations with the experimental results. The influence of concentration (0.1, 0.2 and 0.4wt.%), types of nanoparticles (Al2O3 and Cu) and different base fluids (pure water and ethylene glycol) on the electrical and thermal performance of the collector is investigated. Also, the model is applied to predict the annual electrical and thermal output of the PV/T for three different cities: Lyon (France), Mashhad (Iran) and Monastir (Tunisia). The results indicated that using pure water as a base fluid provides a higher performance in comparison with ethylene glycol. Using Cu/water gives the best thermal and electrical efficiency in comparison to Cu/ethylene glycol, Al2O3/water and Al2O3/ethylene glycol. It is also found that the thermal and electrical energy output for Monastir (Tunisia) climate condition is higher than that of Mashhad (Iran) and Lyon (France).

SIMULATION OF LAMINAR FORCED CONVECTION HEAT TRANSFER AND FLUID FLOW OVER A BACKWARD FACING STEP WITH OBSTACLE USING (SIO ) NANOPARTICLES

Simulation of Heat transfer and laminar Sio2/water and Sio2/oil-engine flow over backward facing step with and without obstacle numerically studied in this paper. The finite volume method adopted to solve continuity,momentum and energy equations in two dimensions. The aspect ratio of triangular obstaclew/e= 0.5 presented.The step height and expansion ratio of channel were 4.8mm and 2 respectively, the range of Reynolds number varied from 100 to 250, constant heat flux subjected on downstream of wall was 2000W/m2.Two types of base fluid used in this simulation the water and oil-engine with constant properties at T = 300K°, The Sio2nanoparticles used with nanoparticles diameter 30nm and volume friction 4%. The average nusselt number noticed increase with increase Reynolds number withobstaclefor two basefluid and also noticed that the nanofluid of Sio2-oil engine has higher nusselt number compared with other nonofluid. The result shows increase of local nusselt numberfor backward facing step with obstacle in compared to those without obstacle. The maximum enhancement of heat transfer observed at obstacle due to increase recirculation flow after the obstacle. Streamline showing the increase of recirculation region with used obstacle in compared without obstacle and highest recirculation region observed at obstacle.

Characterization of Thermal Conductivity and Viscosity of Nanofluids with Aqueous Base Fluids

Two different nanofluids (SiO2 – EG/DW and SiO2 – DW) with various volume fractions are prepared by dispersing SiO2 nanoparticles (< 20 nm) into two different types of base fluid: distilled water and ethylene glycol/distilled water mixture. The effective thermal conductivity and viscosity of nanofluids are characterized and compared over a temperature range of 25oC - 50oC. It is found that the effective thermal conductivity and viscosity of nanofluid are influenced by the nanoparticle volume fraction and the operating temperature. The thermal conductivity of the SiO2 nanofluids with different volume concentrations increases as temperature increases while the viscosity decreases with the increasing temperature. The base fluid alters the characteristics of both the thermal conductivity and viscosity of nanofluid. Over the same range of operating temperature, the effective thermal conductivity and viscosity of SiO2 – EG/DW nanofluid manifest stronger dependency on the nanoparticle concentration compared to those of water-base-fluid nanofluid.

Effects of aligned magneticfield and radiation on the flow of ferrofluids over a flat plate with non-uniform heat source/sink

In this study we analyzed the influence of radiation and aligned magneticfield on the flow of ferrofluids over a flat plate in presence of non-uniform heat source/sink and slip velocity. We considered Fe 3 O 4 magnetic nano particles embedded within the two types of base fluids namely water and kerosene. The governing partial differential equations are transformed into nonlinear ordinary differential equations by using similarity transformation and solved numerically using bvp5c Matlab package. The effects of dimensionless quantities on the flow and temperature profiles along with the friction factor and Nusselt number is discussed and presented through graphs and tables. It is found that present results have an excellent agreement with the existed studies under some special assumptions. Results indicate that a raise in the aligned angle enhances the skin friction coefficient and heat transfer rate.

Theoretical analysis of natural convection boundary layer heat and mass transfer of nanofluids: Effects of size, shape and type of nanoparticles, type of base fluid and working temperature

The problem of natural convection boundary layer heat transfer of nanofluids is theoretically analyzed. Different aspects of nanoparticles, such as size, shape and constructive material, as well as the type of the base fluid and the working temperature, are examined. The drift-flux model of nanofluids, including the effects of Brownian motion, thermophoresis, and the local volume fraction of nanoparticles, is adopted to model the boundary layer heat and mass transfer of nanofluids. Following the state-of-the-art, the thermo-physical properties are extracted from five different synthesized types of nanofluids. A new non-dimensional parameter, the enhancement ratio, indicating the ratio of the convective heat transfer coefficient of the nanofluid to the base fluid, is introduced. The effect of the nanoparticles on the enhancement of natural convective heat transfer of nanofluids is discussed. The main findings of this study are as follows: (i) the type of the nanoparticles and the base fluid are the most important parameters affecting the heat transfer of nanofluids; (ii) in some cases, the presence of nanoparticles in the base fluid deteriorates the heat transfer rate; and (iii) the rise of the working temperature reduces the efficiency of the nanofluid, which is a crucial issue in applications of nanofluids as coolants.

Effects of viscous dissipation and slip velocity on two-dimensional and axisymmetric squeezing flow of Cu-water and Cu-kerosene nanofluids

Squeezing flow of nanofluids has been taken into account under the effects of viscous dissipation and velocity slip. Two types of base fluids are used to study the behavior of Copper nanoparticles between parallel plates. Nonlinear ordinary differential equations governing the flow are obtained by imposing similarity transformations on conservation laws. Resulting equations are solved by using an efficient analytical technique the variation of parameters method (VPM). Influences of nanoparticle concentration and different emerging parameters on flow profiles are presented graphically coupled with comprehensive discussions. A numerical solution is also sought for the sake of comparison. Effect of different parameters on skin friction coefficient and Nusselt number is also discussed.

Hydromagnetic Boundary Layer Flow and Heat Transfer Characteristics of a Nanofluid over an Inclined Stretching Surface in the Presence of a Convective Surface: A Comprehensive Study

In this paper we investigate numerically the hydromagnetic boundary layer flow and heat transfer characteristics of a nanofluid using three types of nanoparticles (copper, aluminium oxide and titanium dioxide) having various shapes (spherical, cylindrical, arbitrary, etc) by considering three kinds of base fluids (water, ethylene glycol and engine oil) over a nonlinear inclined stretching surface, taking into account the effect of convective surface condition. Using similarity transformations, the governing nonlinear partial differential equations of the physical model are transformed into non-dimensional ordinary differential equations which are solved for local similar solutions using the very robust computer algebra software, Maple 13. The numerical simulation is carried out to investigate the role of the pertinent parameters on the flow and temperature fields as well as on the rate of heat transfer and on the rate of shear stress. The results show that the addition of nanoparticles to the base fluid may not always increase the rate of heat transfer. It depends significantly on the surface convection, type of base fluid and nanoparticles. The finding of this study will open a gate for better understanding of nanofluid characteristics.

Statistical optimization of microchannel heat sink (MCHS) geometry cooled by different nanofluids using RSM analysis

In this work, an analytical investigation of the heat transfer for the microchannel heat sink (MCHS) cooled by different nanofluids (Cu, Al2O3, Ag, TiO2 in water and ethylene glycol as base fluids) is studied by the porous media approach and the Galerkin method and results are compared with numerical procedure. Response surface methodology (RSM) is applied to obtain the desirability of the optimum design of the channel geometry. The effective thermal conductivity and viscosity of the nanofluid are calculated by the Patel et al. and Khanafer et al. model, respectively, and MCHS is considered as a porous medium, as proposed by Kim and Kim. In addition, to deal with nanofluid heat transfer, a model based on the Brownian motion of nanoparticles is used. The effects of the nanoparticles volume fraction, nanoparticle type and size, base fluid type, etc., on the temperature distribution, velocity and Nusselt number are considered. Results show that, by increasing the nanoparticles volume fraction, the Brownian movement of the particles, which carries the heat and distributes it to the surroundings, increases and, consequently, the difference between coolant and wall temperature becomes less.

Partial slip effect on non-aligned stagnation point nanofluid over a stretching convective surface

The present study inspects the non-aligned stagnation point nano fluid over a convective surface in the presence of partial slip.Two types of base fluids namely water and kerosene are selected with Cu nanoparticles. The governing physical problem is presented and transformed into a system of coupled nonlinear differential equations using suitable similarity transformations. These equations are then solved numerically using midpoint integration scheme along with Richardson extrapolation via Maple. Impact of relevant physical parameters on the dimensionless velocity and temperature profiles are portrayed through graphs. Physical quantities such as local skin frictions co-efficient and Nusselt numbers are tabularized. It is detected from numerical computations that kerosene-based nano fluids have better heat transfer capability compared with water-based nanofluids. Moreover it is found that water-based nanofluids offer less resistance in terms of skin friction than kerosene-based fluid. In order to authenticate our present study, the calculated results are compared with the prevailing literature and a considerable agreement is perceived for the limiting case.

Numerical Analysis of Turbulent Forced Convection of Nanofluid Flow over a Heated Shallow Cavity

This work presents a numerical investigation of turbulent forced convection of a nanofluid over a heated cavity in a horizontal duct. Heat transfers in separated flows are frequently encountered in engineering applications, such as: heat exchangers, axial and centrifugal compressor blades, gas turbines blades, and microelectronic circuit boards. Thus, it is very essential to understand the mechanisms of heat transfer in such regions in order to enhance heat transfer. Different volume fractions of nanoparticles are presented in the base fluid and different types of nanoparticles are used. The objective of this study is to check the effect of nanofluid on heat transfer in such a configuration. Numerical simulations are performed for pure water and four nanofluids (Cu, CuO, Ag, and Al2O3). The results are analyzed through the thermal and dynamical fields with a particular interest to the skin friction coefficient and Nusselt number evolutions. The average Nusselt number increases with the volume fraction of nanoparticles for the whole tested range of Reynolds number. A correlation of average Nusselt number versus Reynolds number and volume fraction of each type of nanoparticles over the cavity wall is proposed in this paper.

Enhance heat transfer in the channel with V-shaped wavy lower plate using liquid nanofluids

The heat transfer and flow characteristics in corrugated with V-shape lower plate using nanofluids are numerically studied. The computations are performed on uniform heat flux over a range of Reynolds number (Re) 8000–20,000. The governing equations are numerically solved in the domain by a finite volume method (FVM) using the k–ε standard turbulent model. Studies are carried out for different types of nanoparticles Al2O3,CuO, SiO2 and ZnO with different volume fractions in the range of 0–4%. Three different types of base fluid (water, glycerin, ethylene glycol) are also examined. Results indicated that the average Nusselt number for nanofluids is greater than that of the base liquid. The SiO2 nanofluid yields the best heat transfer enhancement among all other type of nanofluids. Heat transfer enhancement increase with increases the volumetric concentration, but it is accompanied by increasing pressure drop values. Moreover, the average Nusselt number increases with an increase in Reynolds number and volume concentration. The SiO2–glycerin nanofluid has the highest Nusselt number compared with other base fluids. The present study shows that these V-shaped wavy channels have advantages by using nanofluids and thus serve as promising candidates for incorporation into efficient heat transfer devices.

Thermophysical effects of carbon nanotubes on MHD flow over a stretching surface

This article is intended for investigating the effects of magnetohydrodynamics (MHD) and volume fraction of carbon nanotubes (CNTs) on the flow and heat transfer in two lateral directions over a stretching sheet. For this purpose, three types of base fluids specifically water, ethylene glycol and engine oil with single and multi-walled carbon nanotubes are used in the analysis. The convective boundary condition in the presence of CNTs is presented first time and not been explored so far. The transformed nonlinear differential equations are solved by the Runge–Kutta–Fehlberg method with a shooting technique. The dimensionless velocity and shear stress are obtained in both directions. The dimensionless heat transfer is determined on the surface. Three different models of thermal conductivity are comparable for both CNTs and it is found that the Xue [1] model gives the best approach to guess the superb thermal conductivity in comparison with the Maxwell [2] and Hamilton and Crosser [3] models. And finally, another finding suggests the engine oil provides the highest skin friction and heat transfer rates.

Stability of Nanofluids for Heat Pipe

Different mass concentrations of Al2O3, SiO2, CuO nanofluids were made by using two-step method with the three types of base fluids deionized water, ethanol and ethylene glyco. The suspension stability of nanofluids and its effect by adding anion and cation surfactants through sedimentation method were studied. The results show that ehylene glycol is as the base fluid, the suspension stability of nanofluids with DW as the base fluid is worst. The suspension stability of Al2O3, SiO2, CuO nanofluids is significantly improved by addition of appropriate dosage of adding anion and cation surfactants for different base fluids. The effect of HTAB is better than that of SDBS.

Heat transfer properties of aqueous carbon nanotubes nanofluids in coaxial heat exchanger under laminar regime

The thermal performance of water-based multi-wall carbon nanotubes nanofluids are measured in a coaxial heat exchanger under laminar regime within the range of Reynolds numbers 500–2500. The convective heat transfer properties with constant wall temperature are evaluated for four different multi-wall carbon nanotubes based nanofluids at low concentration of 0.05% in weight (0.026% in volume). The measurements of thermal and rheological properties of the nanofluids with operating temperature were investigated experimentally. The effects of the aspect ratio of carbon nanotubes, the type of base fluid and surfactant on viscosity, thermal conductivity and laminar convective heat transfer were studied. Based on the experimental results, we reported the shear-thinning behavior of nanofluids, the nanofluid viscosity being dependant on the base fluid type in the Newtonian region. We also showed that the enhancement of the thermal conductivity and the average convective heat transfer of nanofluids increased with the aspect ratio of nanotubes and decreased when the thermal conductivity of the base fluid increases. This enhancement attains at least 10% in comparison to base fluid even with the low content of nanotubes used.

Wavy Channel and Different Nanofluids Effects on Performance of Plate-Fin Heat Exchangers

In the present research, an experimental study of forced convective flows of different nanofluids through a corrugated wavy channel at a constant wall temperature condition was performed. Effects of different parameters, including nanoparticle concentration (copper nanoparticles in deionized water), types of oxide nanoparticles (, , ZnO, , , and CuO), and types of base fluid (deionized water–ethylene glycol mixture), for different volumetric flow rates were examined. The convective heat transfer coefficient and pressure drop measurements were carried out. Results indicate that, for all the values of the flow rate, the Nusselt number augments and Fanning friction factor reduces as the concentration of the copper nanoparticles decreases. In addition, it is shown that the -deionized water nanofluid yields the best thermal–hydraulic performance among the studied oxide nanoparticles in deionized water, and the - and CuO-deionized water nanofluids come in second and third. It is also found, whereas the thermal–hydraulic performance improves with increasing the mass of ethylene glycol in the deionized water base fluid, the nanoparticles in a base fluid with the lower mass of the ethylene glycol in the deionized water shows a better performance.

EXPERIMENTAL INVESTIGATION OF PARAMETERS AFFECTING NANOFLUID EFFECTIVE THERMAL CONDUCTIVITY

The present research reports nanofluid effective thermal conductivity enhancements (ETCE) using an accurate transient short hot wire method system. Preparation of nanofluids was carried out through a two-step method with highly powered pulses similar to that for nanoparticle dispersion in base fluids. Parameters affecting nanofluid heat conductivity such as concentration, sizes, and material of nanoparticleş type of base fluid, temperature, ultrasonic mixing time, and elapsed time after preparation were studied. In the present study, nanoparticles of Al, Al2O3, CuO, SnO2, TiO2, and SiO2 with base fluids of water and ethylene glycol were used. Parameters like concentration, size, temperature, and the type of base fluid showed more noticeable effect on the effective thermal conductivity than the others, and mixing time had the least effect. The results showed that any increase in concentration and temperature, and also any decrease in size of nanoparticles and time elapsed after nanofluid preparation, leads to the ETCE of the nanofluid. However, the effects of nanoparticle material, base fluid, and mixing time on thermal conductivity of the nanofluid showed varying trends. Last, a number of mathematical models for prediction of thermal conductivity of nanofluids were applied.

Stable Nanofluids for Convective Heat Transfer Applications

Abstract Nanofluids are stable dispersions of ultrafine or nanoscale metallic, metal oxide, ceramic particles in a given base fluid. It is reported that nanofluids register an extraordinarily high level of thermal conductivity, and thus possess immense potential in improvement of heat transfer and energy efficiency of several industrial applications including vehicular cooling in transportation, nuclear reactors, and microelectronics. The key issues with nanofluids are: (i) a robust, cost-effective and scalable method to produce nanofluids to industrial scale has not yet been developed, (ii) stability in industrial applications is not yet established, and (iii) meaningful data in flow based heat transfer process do not exist. The present work attempts to address all these three issues. We have developed an in-situ technique for preparation of stable nanofluids by wet-milling of the metal oxide powder in the base fluid, and in the presence of a suitable dispersant. The nanofluids thus produced are tested for heat transfer efficiency under flow conditions in double pipe heat exchangers. Alumina nanofluids have been found to show enhancements of around 10–60% for various base fluids flown under different flow conditions. Thermal enhancements have been found to depend on the flow-rate, particle concentration, type of base fluid, and material of the thermal contact surface of the heat exchanger. The nanofluids thus obtained exhibit sustained stability (>30 months) and their stability remains unaltered for several heating-cooling cycles.

Analysis of entropy generation using nanofluid flow through the circular microchannel and minichannel heat sink

In this paper, different types of entropy generations in the circular shaped microchannel and minichannel are discussed analytically using different types of nanoparticles and base fluids. In this analysis, Copper (Cu), alumina (Al2O3) as the nanoparticle and H2O, ethylene glycol (EG) as the base fluids were used. The volume fractions of the nanoparticles were varied from 2% to 6%. In this paper, the irreversibility or entropy generation analysis as the function of entropy generation ratio, thermal entropy generation rate and fluid friction entropy generation rate for these types of nanofluids in turbulent flow condition have been analyzed using available correlations. Cu–H2O nanofluid showed the highest decreasing entropy generation rate ratio (36%) compared to these nanofluids flow through the microchannel at 6vol.%. The higher thermal conductivity of H2O causes to generate much lower thermal entropy generation rate compared to the EG base fluid. The fluid friction entropy generation rate decreases fruitfully by the increasing of volume fraction of the nanoparticles. Cu–H2O and Cu–EG nanofluid gave the maximum decreasing rates of the fluid friction entropy generation rate are 38% and 35% respectively at 6% volume fraction of the nanoparticles. Smaller diameter showed less entropy generation in case of all nanofluids.

Influence of nanofluids and rotation on helically coiled tube heat exchanger performance

The effects of using various types of nanofluids and rotation on heat transfer and fluid flow characteristics in a helically coiled tube heat exchanger (HCTHE) are numerically investigated. Mainly, the effects of nanoparticles type (Al2O3, SiO2, CuO, ZnO), its concentration (1–4%), and particle diameter (25–80nm), base fluid type (water, ethylene glycol, engine oil), towards the heat transfer and fluid flow characteristics are comprehensively analyzed. The three-dimensional steady, laminar flow and conjugate heat transfer governing equations of a balanced HCTHE are solved using the finite volume method. The results reveal that nanofluids can enhance the thermal properties and performance of the HCTHE but it is accompanied with a slight increase in pressure drop. It is found that the Nusselt number is highest using CuO–water nanofluid in this study. In addition, rotation can be used to enhance the heat transfer rates.