The problem of laminar forced convection flow of nanofluids has been thoroughly investigated for two particular geometrical configurations, namely a uniformly heated tube and a system of parallel, coaxial and heated disks. Numerical results, as obtained for water-γAl 2 O 3 and Ethylene Glycol-γAl 2 O 3 mixtures, have clearly shown that the inclusion of nanoparticles into the base fluids has produced a considerable augmentation of the heat transfer coefficient that clearly increases with an increase of the particle concentration. However, the presence of such particles has also induced drastic effects on the wall shear stress that increases appreciably with the particle loading. Among the mixtures studied, the Ethylene Glycol -γAl 2 O 3 nanofluid appears to offer a better heat transfer enhancement than water- γ/Al 2 O 3 ; it is also the one that has induced more pronounced adverse effects on the wall shear stress. For the case of tube flow, results have also shown that, in general, the heat transfer enhancement also increases considerably with an augmentation of the flow Reynolds number. Correlations have been provided for computing the Nusselt number for the nanofluids considered in terms of the Reynolds and the Prandtl numbers and this for both the thermal boundary conditions considered

Heat transfer enhancement by using nanofluids in forced convection flows

In the present article, double pipe with installed tape was offered as a system to use the hot gas energy. The shell side was full of nanofluid (CuO-H2O) and counter flow was considered. Both zones contain turbulent regime and k–ɛ model has been implemented for simulation. Single phase model in predicting the feature of nanomaterial help us to decrease the computation cost. Modeling based on FVM was employed to extract the contours in various sections in shell region and calculation of f and Nu. In outputs, influences of revolution (N) and Re were examined. Go through the shell side, temperature goes up and velocity increases. When Re* = 5, N = 7, going from inlet to outlet sections leads to intensification of velocity and temperature about 36.1% and 5.63%. Changing N makes temperature to decline about 2.83% and 4.3% when Re = 5000 and 2000, respectively. Moreover, augment of revolution in Re* = 2 and 5 makes velocity to intensify about 16.15% and 12.53%. When N = 3, temperature declines about 4.11% with intensification of inlet velocity while velocity augments about 157.69%. Given Re* = 2, rise of N up to 5 causes Nu and f to intensify to about 17.4% and 33.15%, respectively. With intensification of Re at N = 3, Darcy factor declines to about 15.73% while Nu intensifies to about 100.59%.

Application of nanomaterial for thermal unit including tube fitted with turbulator

Thermal performance of energy conversion systems is one of the most important goals to improve the system's efficiency. Such thermal performance is strongly dependent on the thermophysical features of the applied fluids used in energy conversion systems. Thermal conductivity, specific heat in addition to dynamic viscosity are the properties that dramatically affect heat transfer characteristics. These features of hybrid nanofluids, as promising heat transfer fluids, are influenced by different constituents, including volume fraction, size of solid parts and temperature. In this article, the mentioned features of the nanofluids with hybrid nanostructures and the proposed models for these properties are reviewed. It is concluded that the increase in the volume fraction of solids causes improvement in thermal conductivity and dynamic viscosity, while the trend of variations in the specific heat depends on the base fluid. In addition, the increase in temperature increases the thermal conductivity while it decreases the dynamic viscosity. Moreover, as stated by the reviewed works, different approaches have applicability for modeling these properties with high accuracy, while intelligent algorithms, including artificial neural networks, are able to reach a higher precision compared with the correlations. In addition to the used method, some other factors, such as the model architecture, influence the reliability and exactness of the proposed models.

Thermophysical Properties of Hybrid Nanofluids and the Proposed Models: An Updated Comprehensive Study.

In this experimental study, the specific heat capacity of water-based Fe3O4-Al2O3-ZnO was fabricated. Three mixture ratios of 1:1:1 (33.33%% Fe3O4, 33.33%% Al2O3, 33.33%% ZnO), 1:2:1 (25% Fe3O4, 50% Al2O3, 25% ZnO,) and 1:1:2 (25% Fe3O4, 25% Al2O3, 50% ZnO,) were synthesized at volume fraction of 0.5%, 0.75%, 1% and 1.25%. All the experiments were carried out at a temperature range of 25°C and 65°C. Zeta potential test and particle size analyzer were used in examining the dispersal stability of the nanofluids, and nanoparticle size, respectively. Also, a high-resolution scanning electron microscope was used in describing the morphological structure of the nanocomposites. The result of the study showed that there exists a linear effect of temperature on the specific heat capacity of the ternary hybrid nanofluid. Also, when the volume concentration increases, it causes the specific heat capacity to decrease. At the mixture ratio of 1:1:1(Fe3O4-Al2O3-ZnO), 1:2:1 (Fe3O4-Al2O3-ZnO) and 1:1:2 (Fe3O4-Al2O3-ZnO), the maximum specific heat capacity increment of 11.9399%, 14.6491% and 13.5572% respectively was recorded at 1.25% volume concentration and 25°C temperature, as compared to the base fluid. The experimental result showed a `peaking effect` in the specific heat capacity, which was measured at a mixture ratio of 1:1:1. The least specific heat capacity values recorded are for the mixture ratio of 1:2:1. Correlation and machine learning models were developed in this study, and the result showed that the most accurate prediction of the experimental data was obtained using the support vector regression model. When the support vector regression and correlation models were compared to the experimental results, the maximum deviation recorded was 0.2% and 12.467% respectively.

Synthesis of Fe3O4-Al2O3-ZnO/water ternary hybrid nanofluid: Investigating the effects of temperature, volume concentration and mixture ratio on Specific heat capacity, and development of Hybrid machine learning for prediction

A critical review of specific heat capacity of hybrid nanofluids for thermal energy applications

The present work focused on preparing and studying the fluid and thermal properties such as density, viscosity, specific heat capacity and thermal conductivity of low concentration hybrid nanofluids. The present work also focused on comparing these properties and the thermal enhancements with other low concentration mono nanofluids. The nanofluids used for present work are Al2O3-CuO, Al2O3 and CuO combined with a 60:40 mixing ratio of distilled water and ethylene glycol acting as the base fluid. The volume concentration at which the nanofluids are prepared are fixed 0.02%, 0.04% and 0.06%. The findings show that the thermal conductivity of the hybrid samples is higher compare to its mono counterparts. The thermal conductivity of Al2O3-CuO showed enhancements by 2.3% when compared to CuO and by 3.6% when compared to Al2O3. By using the prepared samples as a working fluid in a compact fin and tube heat exchanger test rig, an experimental investigation is conducted. This is to observe any form of improvements in terms of heat transfer by comparing the experimental results of the hybrid nanofluids with its respective mono counterparts. Based on the experiments conducted, it is found that the use of Al2O3-CuO hybrid nanofluids as a working fluid in a compact heat exchanger test rig showed an increase in both Nusselt number and average heat transfer coefficients by 6.7% and 7.2% respectively when compared to CuO nanofluids and by 17.9% and 12.1% respectively when compared to Al2O3 nanofluids.

Experimental investigation on the thermal performance of compact heat exchanger and the rheological properties of low concentration mono and hybrid nanofluids containing Al2O3 and CuO nanoparticles

Neeshoun Asokan

Papers

Experimental investigation on the thermal performance of compact heat exchanger and the rheological properties of low concentration mono and hybrid nanofluids containing Al2O3 and CuO nanoparticles