This paper aims to study the effect of nanoparticle shape on the entropy generation characteristics of boehmite alumina nanofluid flowing through a horizontal double-pipe minichannel heat exchanger. Boehmite alumina ( γ -AlOOH) nanoparticles of different shapes (cylindrical, brick, blade, platelet, and spherical) are dispersed in a mixture of water/ethylene glycol as the nanofluid. The nanofluid and water flow in the tube side and annulus side of the heat exchanger, respectively. The effects of the Reynolds number and nanoparticle concentration on the frictional entropy generation rate, thermal entropy generation rate, total entropy generation rate and Bejan number are numerically analyzed for different nanoparticle shapes. The obtained results demonstrated that the nanofluids containing platelet shape and spherical shape nanoparticles have the highest and lowest rates of thermal, frictional, and total entropy generation, respectively. Additionally, it was found that the rates of thermal, frictional, and total entropy generation increase with an increase in the Reynolds number, while the opposite is true for the Bejan number. Furthermore, it was inferred from the obtained results that the increase of nanoparticle concentration results in higher frictional and total entropy generation rates and lower Bejan number.

Entropy generation of boehmite alumina nanofluid flow through a minichannel heat exchanger considering nanoparticle shape effect

Exploring the effect of nanoparticle shape on the fluid flow characteristics of boehmite alumina nanofluid in a horizontal double-pipe minichannel heat exchanger is the goal of this study. The proposed boehmite alumina nanofluid could consist of dispersed cylindrical, brick, blade, platelet, and spherical shape nanoparticles in a mixture of water/ethylene glycol. In this study, the water and nanofluid pass through the annulus and tube side of the heat exchanger, respectively. To accurately simulate the behavior of nanofluid, the two phase mixture model is utilized in the simulation. In this investigation, the effect of different Reynolds numbers, nanoparticle concentrations and shapes versus important hydrothermal properties are investigated. The results show that, the spherical and platelet shape lead to the highest and lowest performance index of heat exchanger, respectively. Moreover, it is found that the rates of heat transfer, overall heat transfer coefficient, pressure drop, and pumping power increases with increase in Reynolds number and nanoparticle concentration, while the opposite trend is observed for performance index of the heat exchanger. For instance, at the Reynolds number of 20 000, by boosting the nanoparticle concentration from 0.5 to 2%, the performance index for nanofluid containing platelet shape and spherical shape nanoparticles reduces by 130.63 and 3.88%, respectively.

Hydrothermal analysis of turbulent boehmite alumina nanofluid flow with different nanoparticle shapes in a minichannel heat exchanger using two-phase mixture model

An experimental study on dynamic viscosity and thermal conductivity of water-Cu-SiO2-MWCNT ternary hybrid nanofluid and the development of practical correlations

The thermal conductivity enhancement of nanofluids can be attributed to several factors such as volume fraction, temperature, material type, size and shape. In this study the effects of different morphology of supported nanoparticles, including copper (Cu), silver (Ag), aluminum dioxide (Al2O3), boehmite alumina (γ-AlOOH), molybdenum disulfide (MoS2) and silicon dioxide (SiO2), on heat transfer and entropy generation have been investigated in compression with each other in case of a water-based heat-sink solar collector located in Isfahan city, Iran. The control volume approach was used to solve the system of classical single phase three-dimensional governing equations by using the finite volume method (FVM). The standard k–e turbulence model with enhanced wall function was selected. Furthermore, the spectral radiative transfer equation (RTE) was used to consider radiative heat transfer effects. Based on obtained results, the maximum value of averaged Nusselt number is achieved for MoS2 nanoparticles with sphere shape in φ = 4%, and it is followed by Ag with sphere shape in φ = 0.15%, Cu with sphere shape in φ = 0.20%, γ-AlOOH with sphere shape in φ = 4%, Al2O3 with sphere shape in φ = 4% and SiO2 with sphere shape in φ = 4%. The maximum value of outlet temperature is achieved for Ag nanoparticles with sphere shape in φ = 0.15%, and it is followed by Cu with sphere shape in φ = 0.20%, MoS2 with sphere shape in φ = 4%, Al2O3 with sphere shape in φ = 4%, SiO2 with sphere shape in φ = 4% and γ-AlOOH with sphere shape in φ = 4%. The minimum value of entropy generation is achieved for γ-AlOOH nanoparticles with bricks shape in φ = 2%, and it is followed by SiO2 with bricks shape in φ = 1%, MoS2 with bricks shape in φ = 1%, Ag with sphere shape in φ = 0.05%, Cu with sphere shape in φ = 0.05% and Al2O3 with bricks shape in φ = 1%. In case of heat transfer for all studied nanoparticles (metal and nonmetal nanoparticles), sphere shape is the best morphology for each nanoparticle material. For metal nanoparticles the minimum value of entropy generation is achieved by sphere shape. But for nonmetal nanoparticles the minimum value of entropy generation is reached by bricks shape morphology. Due to fulfill a heat exchanger with more energy efficiency (1st law view point), usage of sphere nanoparticles with optimum size and volume fraction is suggested. In order to achieve a heat exchanger with less entropy generation (2nd law view point), usage of bricks shape nonmetal nanoparticles with optimum size and volume fraction and sphere shape metal nanoparticles with optimum size and volume fraction is suggested.

The effect of nanoparticle morphology on heat transfer and entropy generation of supported nanofluids in a heat sink solar collector

Heat transfer and flow optimization of a novel sinusoidal minitube filled with non-Newtonian SiC/EG-water nanofluids

Nanoparticle shape effects on thermal-hydraulic performance of boehmite alumina nanofluids in a sinusoidal–wavy mini-channel with phase shift and variable wavelength

Saeideh Kermani

Papers

Nanoparticle shape effects on thermal-hydraulic performance of boehmite alumina nanofluids in a sinusoidal–wavy mini-channel with phase shift and variable wavelength