Forced Convective Heat Transfer of Nanofluids in Microchannels

Author(s):  
Jung-Yeul Jung ◽  
Hoo-Suk Oh ◽  
Ho-Young Kwak

Convective heat transfer coefficient and friction factor of a nanofluid in rectangular microchannel were measured. An integrated microsystem consisting of a single microchannel on one side and two localized heaters and five polysilicon temperature sensors along the channel on the other side were fabricated. Aluminum dioxide (Al2O3) nanofluids with various particle volume fractions were used in experiment to investigate the effect of the volume fraction of the nanoparticles to the convective heat transfer and fluid flow in microchannels. The convective heat transfer coefficient of the Al2O3 nanofluid in laminar flow regime was measured to be increased up to 15% compared to the distilled water at a volume fraction of 1.8 volume percent without major friction loss. The Nusselt number measured increases with increasing the Reynolds number in laminar flow regime. A new type of convective heat transfer correlation was proposed to correlate experimental data of heat transfer coefficient for nanofluids in microchannels.

2018 ◽  
Vol 19 (1) ◽  
pp. 251-269 ◽  
Author(s):  
Hossein Fatahian ◽  
Hesamoddin Salarian ◽  
Majid Eshagh Nimvari ◽  
Esmaeel Fatahian

The present study investigated the thermal effects of the use of nanoparticles in the fuel-oil and water-based fluids, as well as the numerical simulation of laminar flow of fuel-oil-alumina and the water-alumina nanofluids in a channel. A second order discretization method was used for solving equations and a SIMPLE algorithm was applied for pressure-velocity coupling using Fluent. Effect of nanoparticle volume fraction and particles size in different Reynolds numbers (900≤Re≤2100) on the convective heat transfer coefficient was studied. The simulation was conducted for three different volume fractions and particle sizes in the laminar flow under constant heat flux. The results showed that adding nanoparticles to the base fluid caused an increase in the thermal conductivity ratio of the fluid, which was observed to a greater degree in the fuel oil-alumina nanofluid than in the water-alumina nanofluid. The increase in nanoparticle volume fraction caused an increase in the convective heat transfer coefficient and the Nusselt number of the nanofluids. The significant point of this study was that in the same volume fraction, the effect of adding alumina nanoparticles to the fuel-oil-based fluid had more effect than adding these particles to water-based fluid, while the effect of increasing the Reynolds number in the water-alumina nanofluid on convective heat transfer coefficient was greater than the fuel-oil-alumina. Also, in the same Reynolds number and volume fraction with increasing size of nanoparticles, the value of the convective heat transfer coefficient was decreased. The results of this study can be used in refineries and petrochemical industries where the fuel-oil fluid flows in the channels. ABSTRAK: Kajian ini adalah bagi mengkaji kesan haba terhadap penggunaan bahan bakar-minyak dan cecair asas-air dalam nanopartikel, juga menjalankan simulasi pengiraan aliran laminar bahan bakar-minyak-alumina dan cecair-nano air-alumina dalam saluran. Kaedah berasingan kelas kedua telah digunakan bagi menyelesaikan persamaan dan algoritma SIMPLE telah diaplikasikan dalam gandingan kelajuan-tekanan menggunakan Fluent. Kesan jumlah pecahan nanopartikel dan pelbagai bilangan saiz zarah dalam bilangan Reynolds (900≤Re≤2100) pada pekali pemindahan haba perolakan telah dikaji. Simulasi telah dijalankan pada tiga pecahan isipadu berlainan dan pada zarah dalam aliran laminar dengan fluks haba tetap. Hasil kajian menunjukkan bahawa dengan penambahan nanopartikel dalam cecair-asas menyebabkan peningkatan nisbah daya pengaliran haba cecair pada cecair-nano bahan bakar-minyak-alumina melebihi daripada cecair-nano air-alumina. Penambahan pada pecahan isipadu nanopartikel ini menyebabkan peningkatan pada nilai pekali pemindahan haba perolakan dan bilangan Nusselt dalam cecair-nano. Perkara penting dalam kajian ini adalah pada pecahan isipadu sama, kesan penambahan nanopartikel alumina kepada cecair berasaskan minyak mempunyai kesan yang lebih besar daripada penambahan zarah-zarah ini kepada cecair berasaskan air. Pada masa sama, kesan peningkatan bilangan Reynolds dalam cecair-nano air-alumina pada pekali pemindahan haba perolakan lebih besar daripada kesan peningkatan bahan bakar-minyak-alumina. Selain itu, pada bilangan Reynolds yang sama dan dengan peningkatan saiz nanopartikel pecahan isipadu, nilai pekali pemindahan haba perolakan turut menurun. Hasil kajian ini boleh digunakan dalam industri penapisan dan petrokimia di mana bahan bakar cecair minyak mengalir dalam saluran.


2015 ◽  
Vol 37 ◽  
pp. 141
Author(s):  
Farhad Vahidinia ◽  
Behrooz Keshtegar ◽  
Mohadeseh Miri

In this paper, the statistical analysis of the effect of nanoparticles volume fraction on one of the most important thermal characteristics turbulent flow of nanofluid i.e. convection heat transfer coefficient, inside a circular tube with uniform wall heat flux is investigated numerically. Also, water as a base fluid and Al2O3 as suspended particles with a diameter of 36 nm are considered. Heat transfer characteristics are computed using the solution of elliptic equations based on discrete the finite volume method and the second order upwind. The relationship between pressure and velocity using SIMPLEC algorithm is established. In this study, the variation of volume fraction of nanoparticles is assumed in the range of 0 to 6%. The best probability distribution function of the heat transfer parameters are selected using chi square test that various probability distribution such as: Gamma, Normal, Lognormal, Gumbel, and Frechet are evaluated based on numerical analysis of tube flow. After reviewing the results, it was found that with increasing volume fraction of nanoparticles, the convective heat transfer coefficient increases. On the other hand, the convective heat transfer coefficients with regard to variation of volume fraction of nanoparticles follow Gumbel Max probability distribution function.


Sign in / Sign up

Export Citation Format

Share Document