Volume Concentration Of Nanofluid Research Articles

Thermal Management of Electronic Devices Using Combined Effects of Nanoparticle Coating and Graphene–Water Nanofluid in a Miniature Loop Heat Pipe

The thermal management of electronic devices such as high-end central processing units, graphic processing units, insulated gate bipolar transistor, and circuit breaker in low-voltage switchboard operating between 20 and 380 W is investigated using a miniature loop heat pipe (mLHP) having nanoparticle-coated evaporator with graphene–water nanofluid. The thermal evaporation method is used to deposit copper nanoparticles on the evaporator surface for a coating thickness of 400 nm. The experimental results show that the combination of nanoparticle coating and nanofluid gives the highest heat transfer compared to the mLHP having uncoated and coated evaporator with distilled water as a working fluid. The use of nanofluid enhances the heat transfer performance of mLHP with an average reduction of 45.2% in thermal resistance and an average enhancement of 113.4% in evaporator heat transfer coefficient for the optimum nanofluid volume concentration of 0.006%. Similarly, the lowest evaporator temperatures are also obtained with the same concentration of nanofluid for various heat loads. The experimental results of mLHP having nanoparticle coating and nanofluid are also found to be repeatable from the repeated tests and suitable for a long-term operation.

Exergy analysis of hybrid nanofluids with optimum concentration in a plate heat exchanger

This paper highlights an investigation on the comparative analyses of exergetic performance with optimum volume concentration of hybrid nanofluids in a plate heat exchanger (PHE). Different types of hybrid nanofluids (Al2O3 + MWCNT/water, TiO2 + MWCNT/water, ZnO + MWCNT/water, and CeO2 + MWCNT/water) as coolant have been tested. Proportion of 0.75% of nanofluid has been found to be the optimum volume concentration. The requisite thermal and physical properties of the hybrid nanofluids were measured at 35 °C. Various exergetic performance parameters have been examined for comparing different hybrid nanofluids. The highest reduction in exergy loss of CeO2 + MWCNT/water hybrid nanofluid has been obtained at a concentration of about 24.75%. Entropy generation decreased with the increase in volume concentration. The results established that CeO2 + MWCNT/water hybrid nanofluid can be a promising coolant for exergetic performances in a PHE.

Fabricating an experimental setup to investigate the performance of an automobile car radiator by using aluminum/water nanofluid

In this present work, effect of Al/water nanofluids on the rheological performance of an automobile car radiator has been investigated. Nanofluids were fabricated by two-step methods, i.e., dispersing of aluminum metal bases nanoparticles of size 75–135 nm in double-distilled water. Experiments were conducted on single-pass cross-flow compact heat exchanger by varying the various parameters such as inlet temperature, flow rate through the heat exchanger, concentration of nanoparticles and velocity of air employed for cooling purpose. It was concluded that the hot side Nusselt numbers are improved by 3.37 and 5.0877% for 0.2 and 0.3% concentrations of nanofluids, respectively, at 318.15 K inlet fluids temperature as compared to base fluids. Colburn factor was increased by 12.94 and 23.45% for 0.2 and 0.3% nanoparticles volume concentration of nanofluids, respectively, at 318.15 K inlet temperature with respect to double-distilled water. Hot fluid side friction factor was increased by 14.04 and 20.916% for 0.2 and 0.3% nanoparticles volume concentration of nanofluids with respect to base fluids, but this average value of friction factor was decreased by 2.29 and 9.1412% when temperature was increased from 318.15 to 323.15 K and 328.15 K, respectively.

Heat Transfer by Porous Pin Fins and Nanofluid in Rectangular Microchannels

The forced convective heat transfer with 3D, triangular, porous pin fins as bundle of MWCNTs at the bottom of rectangular mini channels made of silicon. Overall heat transfer performances in porous pin fins are much better than those in traditional solid pin fins. As nanofluid volume concentration increases, pressure drops and heat fluxes in porous pin fin channels increase and maximal overall heat transfer are obtained at 0.01% concentration. Enhancement in Nu were 6% with respect to porosity and 88 % with respect to 0.01% Al 2 O 3 /H 2 O. With the same physical parameters, the Nu in the staggered triangular porous pin fin channels of CNTs with fin height of 0.75 mm, smaller fin width of 0.5 mm and spacing double the fin width using 0.01% CuO/H 2 O nanofluid showed the highest enhancement of 91% at higher Re with a corresponding decrease in pressure drop of 25%. DOI: http://dx.doi.org/10.5755/j01.mech.24.1.17284

Discrete phase numerical model and experimental study of hybrid nanofluid heat transfer and pressure drop in plate heat exchanger

In the present study, numerical as well as experimental investigations have been done on the plate heat exchanger using hybrid nanofluid (Al2O3+MWCNT/water) at different concentration to investigate its effect on heat transfer and pressure drop characteristics. Discrete phase model has been used for the investigation using CFD software and results have been compared with the experimental result as well as result of the homogenous model. Effects of different operating parameters (nanofluid inlet temperature, flow rate and volume concentration) have been studied on coolant outlet temperature, heat transfer rate, convective and overall heat transfer coefficients, Nusselt number, friction factor, pressure drop, pumping power, effectiveness and performance index. Velocity and temperature profiles have been also studied for base fluid, nanofluid and hybrid nanofluid. By using hybrid nanofluid, heat transfer coefficient enhances by 39.16% (merit) with negligible increase in pumping power of 1.23% (demerit). An enhancement in heat transfer and pressure drop characteristics; and hence on the effectiveness of plate heat exchanger has been observed while using hybrid nanofluids instead of base fluid.

Heat transfer and friction factor of nanodiamond-nickel hybrid nanofluids flow in a tube with longitudinal strip inserts

The heat transfer and friction factor of a new kind of nanodiamond-nickel (ND-Ni) hybrid nanofluids flow in a tube with and without longitudinal strip inserts were studied experimentally. The hybrid ND-Ni nanoparticles were synthesized using in-situ and chemical coprecipitation method and characterized with different techniques. The bulk quantity of hybrid ND-Ni nanofluids were prepared and used for heat transfer and friction analysis. The experiments were conducted in the Reynolds number range from 3000 to 22,000, for the volume concentrations of 0.1% and 0.3%, and for different aspect ratios (AR = 1, 2 and 4) of the longitudinal strip inserts. The Nusselt number is enhanced by 35.43% (without insert) and further enhanced by 93.30% with longitudinal strip insert (AR = 1) for 0.3% volume concentration of nanofluid and at Reynolds number of 22,000 compared to water data. The friction factor penalty of 1.12-times without inserts and further penalty of 1.248-times with longitudinal strip insert (AR = 1) at 0.3% volume concentration of nanofluid and at Reynolds number of 22,000 compared to water data. The obtained experimental Nusselt number of hybrid nanofluids was compared with that of other kind of hybrid nanofluids available in the literature. The Nusselt number and friction factor correlations were developed based on the experimental data.

Effects of sonication time and temperature on thermal conductivity of CuO/water and Al2O3/water nanofluids with and without surfactant

In this article, an experimental work was carried out to investigate the thermal conductivity of CuO/water and Al2O3/water nanofluids with and without surfactants. Three different volume concentrations of nanofluids (0.05, 0.1 and 0.2%) prepared by using single step preparation method. Sodium dodecylbenzene sulfonate used as a surfactant in this study. The analysis is carried out on the effects of sonication time and thermal conductivity of the prepared nanofluids by varying temperature from 30°C to 60°C. The obtained results indicate that the thermal conductivity of nanofluids increased with an increase of sonication time, temperature and the amount of surfactant. Also, the maximum thermal conductivity value was obtained for 0.2% volume concentration of CuO/water nanofluid with SDBS surfactant.

Performance study of conical strip inserts in tube heat exchanger using water based titanium oxide nanofluid

The objective of the study is to observe the Nusselt number and friction factor behavior in a tube heat exchanger fitted with staggered and non-staggered conical strip inserts using water based titanium oxide nanofluid under laminar flow conditions. Water based titanium oxide nanofluid was prepared using a two-step method with a volume concentration of 0.1% and 0.5%. The tube inserts used were staggered and non-staggered conical strips having three different twist ratios of 2, 3, and 5. The experimental results indicated that the Nusselt number increased in the presence of water based titanium oxide nanofluid compared to the base fluid. Nusselt number further increased enormously with the use of conical strip inserts than a tube with no inserts. It was observed that the strip geometry and the nanofluid had a major effect on the thermal performance of the circular tube heat exchanger. It was found that with the staggered conical strip having a twist ratio of Y = 3 and 0.5% volume concentration of nanofluid provided the highest heat transfer. Correlations have been derived using regression analysis.

Flow behaviour of suspensions of functionalized graphene nanoplatelets in propylene glycol–water mixtures

The low thermal conductivity of the fluids usually used in heat exchange processes (water, oils, glycols…) has proved to be one of the limiting factors in improving their heat transfer performance. These traditional fluids enhance their thermal capabilities by dispersing nano-sized particles with high thermal conductivity, as many researches have revealed in the last decades. Although the thermal conductivity of nanofluids has centred the interest of the heat transfer community, the rheological behaviour of the resulting dispersions is very influential in the heat transfer process, pressure drops and pumping powers. In this work, different samples of functionalized graphene nanoplatelets dispersed into two different binary mixtures of propylene glycol and water at 10:90wt% and 30:70wt% have been analysed by using a DHR-2 rotational rheometer equipped with concentric cylinder geometry. Firstly, the flow curves for Krytox GPL102 oil, pure propylene glycol, and the two binary mixtures of propylene glycol and water used as base fluids were experimentally obtained. These values were used to check our experimental procedure finding a good agreement between them and those reported and well known in the literature, with an absolute average deviation of 2.0%. Then, the viscosity-shear rate curves in the temperature range from 278.15 to 323.15K were obtained for the different graphene nanofluid sets. Furthermore, a new equation was proposed in this work to describe the viscosity dependence on both the temperature and the nanoparticles volume concentration of graphene nanoplatelet nanofluids with an absolute average deviation with respect to our experimental data lower than 2%. Additionally, oscillatory tests of the samples were performed observing pseudoplastic behaviour for the nanofluids at lower angular frequencies.

Thermo-electrical performance of PEM fuel cell using Al2O3 nanofluids

Nanofluid adoption as an alternative coolant for Proton Exchange Membrane (PEM) fuel cell is a new embarkation which hybridizes the nanofluids and PEM fuel cell studies. In this paper, findings on the thermo-electrical performance of a liquid-cooled PEM fuel cell with the adoption of Al2O3 nanofluids were established. Thermo-physical properties of 0.1, 0.3 and 0.5% volume concentration of Al2O3 nanoparticles dispersed in water and water: Ethylene glycol (EG) mixtures of 60:40 were measured and then adopted in PEM fuel cell as cooling medium. The result shows that the cooling rate improved up to 187% with the addition of 0.5% volume concentration of Al2O3 nanofluids to the base fluid of water. This is due to the excellent thermal conductivity property of nanofluids as compared to the base fluid. However, there was a penalty of higher pressure drop and voltage drop experienced. Thermo electrical ratio (TER) and Advantage ratio (AR) were then established to evaluate the feasibility of Al2O3 nanofluid adoption in PEM fuel cells in terms of both electrical and thermo-fluid performance considering all aspects including heat transfer enhancement, fluid flow and PEM fuel cell performance. Upon analysis of these two ratios, 0.1% volume concentration of Al2O3 dispersed in water shows to be the most feasible nanofluid for adoption in a liquid-cooled PEM fuel cell.

A new turbine model for enhancing convective heat transfer in the presence of low volume concentration of Ag-Oil Nanofluids

This study aims to experimentally investigate and introduce a new model for enhancing convective heat transfer in the presence of Ag/ oil nanofluid. An annular tube was designed with a turbine element attached to the inner tube. The inner tube was a bearing shaft which could rotate with the rotation of turbine element. As the previous works by authors, the setup was conducted with a fully developed laminar flow regime with the Reynolds numbers less than 160. The outer surface of the annular tube was heated by an element with constant heat flux of 204 W. Ag/ oil nanofluid was used in different volume concentrations of 0.011%, 0.044% and 0.171%. The new model could enhance the convective heat transfer coefficient up to 54% (compared to the simple annular tube in the case of base fluid) for the best studied case (nanofluid with the volume concentration of 0.171%) while the friction factor remained low. The new model can be applied for related applications regarding Ag/ oil nanofluid as a new step in enhancing the convective heat transfer coefficient.

Unsteady MHD slip flow of non Newtonian power-law nanofluid over a moving surface with temperature dependent thermal conductivity

In this paper, unsteady magnetohydrodynamic (MHD) boundary layer slip flow and heat transfer of power-law nanofluid over a nonlinear porous stretching sheet is investigated numerically. The thermal conductivity of the nanofluid is assumed as a function of temperature and the partial slip conditions are employed at the boundary. The nonlinear coupled system of partial differential equations governing the flow and heat transfer of a power-law nanofluid is first transformed into a system of nonlinear coupled ordinary differential equations by applying a suitable similarity transformation. The resulting system is then solved numerically using shooting technique. Numerical results are presented in the form of graphs and tables and the effect of the power-law index, velocity and thermal slip parameters, nanofluid volume concentration parameter, applied magnetic field parameter, suction/injection parameter on the velocity and temperature profiles are examined from physical point of view. The boundary layer thickness decreases with increase in strength of applied magnetic field, nanoparticle volume concentration, velocity slip and the unsteadiness of the stretching surface. Whereas thermal boundary layer thickness increase with increasing values of magnetic parameter, nanoparticle volume concentration and velocity slip at the boundary.

Experimental investigation of Al2O3/water nanofluids on the effectiveness of solar flat-plate collectors with and without twisted tape inserts

Abstract The thermal effectiveness of solar water heaters can be enhanced if passive heat transfer enhancement techniques are used. Among the most effective passive heat transfer enhancement techniques are the increase of the working fluid thermal conductivity and of its flow turbulence. In this paper, Al2O3 nanofluids and twisted tape inserts are the passive techniques used to enhance the heat transfer and, consequently the thermal effectiveness of the solar water heater. In the solar water heating system considered in this study, the collector is essentially mimicked by a tube with or without a twisted tape, with water or nanofluids flowing through it. Results of the heat transfer experiments indicate that for a Reynolds number of 13000 the heat transfer enhancement for 0.3% volume concentration of nanofluid is 21% for the plain tube and it is further enhanced to 49.75% when a twisted tape of H/D = 5 is inserted in the tube. The maximum friction penalty of 1.25-times was observed for 0.3% nanofluid with H/D = 5 when compared to water in a plain collector. The thermal effectiveness of the plain collector is enhanced to 58%, when the 0.3% nanofluid is used and it is further enhanced to 76% with a twisted tape of H/D = 5 at a mass flow rate of 0.083 kg/s. Solar water heaters, in which the collectors have twisted tape inserts and use nanofluids, have thermal performance increases that largely outweigh pressure drop losses. Under the same operating conditions, the nanofluids/twisted tape inserts collector outperforms that with water and no twisted tapes.

Experimental investigation of thermal conductivity and dynamic viscosity on nanoparticle mixture ratios of TiO2-SiO2 nanofluids

In recent years, research is focused on enhancing the thermo-physical properties of single component nanofluids. Hence, the hybrid or composite nanofluids are developed to enhance the heat transfer performance. The thermo-physical properties of TiO2-SiO2 nanoparticles suspended in a base fluid of water (W) and ethylene glycol (EG) mixture with 60:40vol ratio are investigated. The experiments were conducted for 1.0% volume concentration of TiO2-SiO2 nanofluids with different mixture ratios of 20:80, 40:60, 50:50, 60:40 and 80:20. The measurements of thermal conductivity and dynamic viscosity were performed in the temperature range of 30–80°C by using KD2 Pro Thermal Properties Analyzer and Brookfield LVDV III Ultra Rheometer respectively. The highest thermal conductivity for TiO2-SiO2 nanofluid was obtained with a ratio of 20:80 and the maximum enhancement exceeded up to 16% higher than the base fluids. The nanofluids with a ratio of 50:50 provided the lowest effective thermal conductivity. Meanwhile, the dynamic viscosity variation for all mixture ratios is always lower than the ones with a ratio of 50:50. The properties enhancement ratio suggests that TiO2-SiO2 nanofluid with 1.0% volume concentration will aid the heat transfer for all mixture ratios except for the ratio of 50:50. Asa conclusion, the optimum mixture ratios for TiO2-SiO2 nanofluids are attained with 40:60 and 80:20 ratios where the combination of enhancement in thermal conductivity and dynamic viscosity had more advantages to heat transfer as compared to other ratios.

Turbulent heat transfer and friction factor of nanodiamond-nickel hybrid nanofluids flow in a tube: An experimental study

Turbulent heat transfer and friction factor of nanodiamond-nickel (ND-Ni) hybrid nanofluids flow in a horizontal tube has been investigated experimentally. The ND-Ni nanoparticles were synthesized using in-situ growth and chemical co-precipitation method and characterized by XRD, TEM and VSM. The hybrid nanofluids were prepared by dispersing ND-Ni hybrid nanoparticles in distilled water. The thermal conductivity and viscosity enhancements were observed as 29.39% and 23.24% at 0.3% volume concentration of hybrid nanofluid at 60°C compared to distilled water. The heat transfer and friction factor experiments were conducted at different Reynolds numbers (3000–22,000) and particle volume concentrations (0.1% and 0.3%). The Nusselt number enhancement of 0.3% volume concentration of hybrid nanofluid is 35.43% with a friction factor penalty of 1.12-times at a Reynolds number of 22,000 compared to distilled water data. The obtained experimental Nusselt number of hybrid nanofluids was compared with other kind of hybrid nanofluids available literature. New Nusselt number and friction factor correlations were proposed based on the experimental data.

Titanium oxide with nanocoolant for heat exchanger application

The objective of this paper is to investigate the properties of oil-based nanofluids and produce stable and biodegradable oil-based nanofluids by metal oxide nanoparticles. The cooking oil was used as a base for the nanofluid preparation. Titanium oxide was embedded as the nanoparticles, mixed with cooking oil volume concentration of nanofluids specimens, and labelled as 0.01, 0.03, 0.05, 0.07, and 0.09. The study explained the analysis techniques applied to determine the enhancement of thermal properties of nanofluids. The thermal conductivity of nanofluids was studied by heat transfer rate and the overall heat transfer coefficient gained. The metal oxide nanomaterials were mixed with the oil-based fluids in order to prepare the specimens. This research focused on the usage of vegetable oil and titanium oxide nanoparticles mixture to form nanofluids. The results obtained indicated that the nanofluid gave better thermal conductivity than oil-based fluids. The results significantly increased the thermal properties limitation and improved the product reliability. The enhancement of heat transfer rate for 0.09% of nanofluid volume concentration was increased by 36.25%

Heat Transfer Enhancement Analysis of Al2O3-Water Nanofluid Through Parallel and Counter Flow in Shell and Tube Heat Exchangers

Heat exchanger plays an essential part in industrial sector in transferring the heat energy. Heat is exchanged between fluids in convection and conduction mode through the walls of the heat exchanger. If the heat transfer medium has low thermal conductivity, it will greatly limit the efficiency of the heat exchanger. Whenever the system acts subjected to an increase in the heat load, heat fluxes caused by more power and smaller size, cooling is one of the technical challenges faced by the industries. The objective of this research work is to evaluate the overall heat transfer coefficient through an experimental analysis on the convective heat transfer and flow characteristics of a nanofluid. In our experiment, the nanofluid consists of water and one percentage volume concentration of Al2O3-water nanofluid flowing through parallel and counter flow in shell and tube heat exchangers. About 50[Formula: see text]nm diameter of Al2O3 nanoparticles was used in this analysis and found that the overall heat transfer coefficient and convective heat transfer coefficient of nanofluid were slightly higher than those of the base liquid at same mass flow rate and inlet temperature. Here, there are three samples of dissimilar mass flow rates, which have been identified for conducting the experiments and their results are continuously monitored and reported. Finally, the observed results through an experimental investigation were presented and concluded that the enhancement of overall heat transfer coefficient is likely to be feasible by means of increasing the mass flow rate of base fluid and prepared nanofluid on the proportional basis.

Thermal performance and thermal properties of hybrid nanofluid laminar flow in a double pipe heat exchanger

The mixing of solid nanoparticles suspended in liquid is defined as a hybrid nanofluid that represents a new class of heat transfer augmentation. In order to examine the laminar convective heat transfer of nanofluid, experiments were conducted using a hybrid nanofluid through a double pipe heat exchanger. The mixtures of Aluminum Nitride nanoparticles into ethylene glycol (EG) as a basefluid are considered to augment the heat transfer. The hybrid nanofluid is prepared with the volume fraction of 1–4% and having the size of diameter 30nm in addition to measuring the thermal properties experimentally. Both hydrodynamic and thermal performances of AlN nanoparticle dispersed in EG are studied. The flow rates and Reynolds number along experiments are changed in the range of 0.5–4LPM and 500–1750 respectively. The results show that the friction factor decreases when there is an increase in the flow rate and it increases when the volume concentration of nanofluid is increased while the Nusselt number increases by increasing of the flow rate and volume concentration of nanofluid. Meanwhile, the application of hybrid nanofluid with low volume fractions may augment heat transfer efficiency up to 160% as compared with conventional fluids. It was found that the thermal performance of hybrid nanofluid could drastically augment the thermal performances of a heat exchanger in comparison with basefluid up to 35% at high volume fraction.

Thermal conductivity of Al2O3 + TiO2/water nanofluid: Model development and experimental validation

A water based bi-particle nanofluid including Al2O3 and TiO2 nanoparticles was prepared and its thermal conductivity behavior was studied. Two different models were developed to predict the thermal conductivity of a bi-particle nanofluid. The first model was the extended Maxwell model (EMM) and the second one was particle mapping model (PMM). The results show that thermal conductivity of a bi-particle nanofluid versus fractional particles volume concentration has a nonlinear behavior according to the PMM and experimental results. The factors those influencing the thermal conductivity of bi-particle nanofluids were studied and it was found that the nanofluid stability is the most affecting factor for describing the nonlinear behavior of the thermal conductivity against fractional particles volume concentration.

Numerical investigation of shell and tube heat exchanger using Al2O3 nanofluid

This paper presents the effect of number of tubes, unequal baffle spacing and tube diameter on heat transfer and pressure drop characteristics of a typical shell and tube type heat exchanger. Upon geometrical optimization, the second phase of this research work aims at studying the influence of Al2O3 nanofluid of 0.5%, 0.75%, 1%, 1.25% and 1.5% concentrations by admitting water along the tubes and Al2O3 nanofluid along the shell side. The shell and tube heat exchangers of various geometrical configurations are modeled using SOLIDWORKS 2015. The heat transfer and fluid flow characteristics through the heat exchanger are obtained by solving the governing equations namely continuity, momentum and energy equations using ANSYS CFX 15 CFD code. Temperature, pressure contours and velocity streamlines along the mid-plane of the shell and tube heat exchanger are obtained for various geometrical configurations and for different volume concentration of nanofluid. The heat transfer coefficient and the pressure drop for various volume fraction concentrations of the nanofluid are plotted. The use of nanofluid resulted in increase of both the pressure drop and heat transfer coefficient. The heat transfer coefficient at 1.25% volume concentration of nanofluid is found to be the optimum value.