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Numerical study of a confined slot impinging jet with nanofluids.

Manca O, Mesolella P, Nardini S, Ricci D - Nanoscale Res Lett (2011)

Bottom Line: The dimensionless stream function contours show that the intensity and size of the vortex structures depend on the confining effects, given by H/W ratio, Reynolds number and particle concentrations.Furthermore, for increasing concentrations, nanofluids realize increasing fluid bulk temperature, as a result of the elevated thermal conductivity of mixtures.The required pumping power as well as Reynolds number increases and particle concentrations grow, which is almost 4.8 times greater than the values calculated in the case of base fluid.List of symbols.

View Article: PubMed Central - HTML - PubMed

Affiliation: Dipartimento di Ingegneria Aerospaziale e Meccanica, Seconda Università degli Studi di Napoli, Via Roma 29 - 81031 Aversa, Italy. oronzio.manca@unina2.it.

ABSTRACT

Background: Heat transfer enhancement technology concerns with the aim of developing more efficient systems to satisfy the increasing demands of many applications in the fields of automotive, aerospace, electronic and process industry. A solution for obtaining efficient cooling systems is represented by the use of confined or unconfined impinging jets. Moreover, the possibility of increasing the thermal performances of the working fluids can be taken into account, and the introduction of nanoparticles in a base fluid can be considered.

Results: In this article, a numerical investigation on confined impinging slot jet working with a mixture of water and Al2O3 nanoparticles is described. The flow is turbulent and a constant temperature is applied on the impinging. A single-phase model approach has been adopted. Different geometric ratios, particle volume concentrations and Reynolds number have been considered to study the behavior of the system in terms of average and local Nusselt number, convective heat transfer coefficient and required pumping power profiles, temperature fields and stream function contours.

Conclusions: The dimensionless stream function contours show that the intensity and size of the vortex structures depend on the confining effects, given by H/W ratio, Reynolds number and particle concentrations. Furthermore, for increasing concentrations, nanofluids realize increasing fluid bulk temperature, as a result of the elevated thermal conductivity of mixtures. The local Nusselt number profiles show the highest values at the stagnation point, and the lowest at the end of the heated plate. The average Nusselt number increases for increasing particle concentrations and Reynolds numbers; moreover, the highest values are observed for H/W = 10, and a maximum increase of 18% is detected at a concentration equal to 6%. The required pumping power as well as Reynolds number increases and particle concentrations grow, which is almost 4.8 times greater than the values calculated in the case of base fluid.List of symbols.

No MeSH data available.


Related in: MedlinePlus

Stagnation point values of local Nusselt number. Values of local Nusselt number in correspondence with the stagnation point, for different Re and concentrations: (a) H/W = 4; (b) H/W = 6; (c) H/W = 8; (d) H/W = 10.
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Figure 11: Stagnation point values of local Nusselt number. Values of local Nusselt number in correspondence with the stagnation point, for different Re and concentrations: (a) H/W = 4; (b) H/W = 6; (c) H/W = 8; (d) H/W = 10.

Mentions: The results in terms of local Nusselt numbers, calculated for the stagnation point, are depicted in Figure 11. They are provided as a function of Reynolds numbers and given for different concentrations for different H/W ratios, equal to 4, 6, 8, and 10. It is shown that profiles increase almost linearly with increasing Reynolds numbers for all the considered concentrations and H/W ratios. Moreover, the Nu0 values are the highest for ϕ = 6% for all the considered Reynolds numbers. For example, comparing the results for ϕ = 1, 4, and 6%, with the base fluid ones, an increase in values of 2.7, 10.8, and 16.2% are detected for H/W = 4 at Re = 20000, respectively. Moreover, Nu0 values rises as H/W increases for Re > 10000, as observed in Figure 11b, c, d.


Numerical study of a confined slot impinging jet with nanofluids.

Manca O, Mesolella P, Nardini S, Ricci D - Nanoscale Res Lett (2011)

Stagnation point values of local Nusselt number. Values of local Nusselt number in correspondence with the stagnation point, for different Re and concentrations: (a) H/W = 4; (b) H/W = 6; (c) H/W = 8; (d) H/W = 10.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211241&req=5

Figure 11: Stagnation point values of local Nusselt number. Values of local Nusselt number in correspondence with the stagnation point, for different Re and concentrations: (a) H/W = 4; (b) H/W = 6; (c) H/W = 8; (d) H/W = 10.
Mentions: The results in terms of local Nusselt numbers, calculated for the stagnation point, are depicted in Figure 11. They are provided as a function of Reynolds numbers and given for different concentrations for different H/W ratios, equal to 4, 6, 8, and 10. It is shown that profiles increase almost linearly with increasing Reynolds numbers for all the considered concentrations and H/W ratios. Moreover, the Nu0 values are the highest for ϕ = 6% for all the considered Reynolds numbers. For example, comparing the results for ϕ = 1, 4, and 6%, with the base fluid ones, an increase in values of 2.7, 10.8, and 16.2% are detected for H/W = 4 at Re = 20000, respectively. Moreover, Nu0 values rises as H/W increases for Re > 10000, as observed in Figure 11b, c, d.

Bottom Line: The dimensionless stream function contours show that the intensity and size of the vortex structures depend on the confining effects, given by H/W ratio, Reynolds number and particle concentrations.Furthermore, for increasing concentrations, nanofluids realize increasing fluid bulk temperature, as a result of the elevated thermal conductivity of mixtures.The required pumping power as well as Reynolds number increases and particle concentrations grow, which is almost 4.8 times greater than the values calculated in the case of base fluid.List of symbols.

View Article: PubMed Central - HTML - PubMed

Affiliation: Dipartimento di Ingegneria Aerospaziale e Meccanica, Seconda Università degli Studi di Napoli, Via Roma 29 - 81031 Aversa, Italy. oronzio.manca@unina2.it.

ABSTRACT

Background: Heat transfer enhancement technology concerns with the aim of developing more efficient systems to satisfy the increasing demands of many applications in the fields of automotive, aerospace, electronic and process industry. A solution for obtaining efficient cooling systems is represented by the use of confined or unconfined impinging jets. Moreover, the possibility of increasing the thermal performances of the working fluids can be taken into account, and the introduction of nanoparticles in a base fluid can be considered.

Results: In this article, a numerical investigation on confined impinging slot jet working with a mixture of water and Al2O3 nanoparticles is described. The flow is turbulent and a constant temperature is applied on the impinging. A single-phase model approach has been adopted. Different geometric ratios, particle volume concentrations and Reynolds number have been considered to study the behavior of the system in terms of average and local Nusselt number, convective heat transfer coefficient and required pumping power profiles, temperature fields and stream function contours.

Conclusions: The dimensionless stream function contours show that the intensity and size of the vortex structures depend on the confining effects, given by H/W ratio, Reynolds number and particle concentrations. Furthermore, for increasing concentrations, nanofluids realize increasing fluid bulk temperature, as a result of the elevated thermal conductivity of mixtures. The local Nusselt number profiles show the highest values at the stagnation point, and the lowest at the end of the heated plate. The average Nusselt number increases for increasing particle concentrations and Reynolds numbers; moreover, the highest values are observed for H/W = 10, and a maximum increase of 18% is detected at a concentration equal to 6%. The required pumping power as well as Reynolds number increases and particle concentrations grow, which is almost 4.8 times greater than the values calculated in the case of base fluid.List of symbols.

No MeSH data available.


Related in: MedlinePlus