Numerical Investigation On The Impingement Of A Circular Jet Of Nanofluids On A Circular Flat Plate

Experimental Model ◽

Convective Heat ◽

Reynolds Numbers ◽

Transfer Coefficients ◽

Maximum Heat ◽

A numerical study was conducted to investigate and validate experimental convective heat transfer coefficient data associated with an Al2O3-H2O nanofluid through the use of an impingement jet on a flat, circular disk. It was observed that, in conjunction with experimental data, nanofluids provided increased local convective heat transfer coefficients in comparison to the base fluid. Nanofluid concentrations outlined in the experimental model, from 0.0198 to 0.0757 wt%, were investigated in a numerical model and resulting convective heat transfer coefficients were compared. In contrast to the experimental model, the maximum heat transfer enhancement occurred at the nanofluid concentration of 0.0757 wt%. In addition, several other models were tested with various Reynolds numbers and jet height-to-jet diameter ratios for further investigation along with discussion of sources of error. Overall, in comparison to experimental data, the lowest percentage errors achieved for the Reynolds numbers of 4245.7 and 8282 were 17.9% and 34.9%, respectively.

Experimental Study of Forced Convective Heat Transfer in a Coiled Flow Inverter Using TiO2–Water Nanofluids

Applied Sciences ◽

10.3390/app10155225 ◽

2020 ◽

Vol 10 (15) ◽

pp. 5225

Author(s):

Barbara Arevalo-Torres ◽

Jose L. Lopez-Salinas ◽

Alejandro J. García-Cuéllar

Keyword(s):

Heat Transfer ◽

Heat Exchanger ◽

Convective Heat ◽

Reynolds Numbers ◽

Working Fluid ◽

Transfer Coefficients ◽

Convective Thermal ◽

The curved geometry of a coiled flow inverter (CFI) promotes chaotic mixing through a combination of coils and bends. Besides the heat exchanger geometry, the heat transfer can be enhanced by improving the thermophysical properties of the working fluid. In this work, aqueous solutions of dispersed TiO2 nanometer-sized particles (i.e., nanofluids) were prepared and characterized, and their effects on heat transfer were experimentally investigated in a CFI heat exchanger inserted in a forced convective thermal loop. The physical and transport properties of the nanofluids were measured within the temperature and volume concentration domains. The convective heat transfer coefficients were obtained at Reynolds numbers (NRe) and TiO2 nanoparticle volume concentrations ranging from 1400 to 9500 and 0–1.5 v/v%, respectively. The Nusselt number (NNu) in the CFI containing 1.0 v/v% nanofluid was 41–52% higher than in the CFI containing pure base fluid (i.e., water), while the 1.5 v/v% nanofluid increased the NNu by 4–8% compared to water. Two new correlations to predict the NNu of TiO2–water nanofluids in the CFI at Reynolds numbers of 1400 ≤ NRe ≤ 9500 and nanoparticle volume concentrations ranges of 0.2–1.0 v/v% and 0.2–1.5 v/v% are proposed.

Study on Forced Convective Heat Transfer of FC-72 in Vertical Small Tubes

Journal of Thermal Science and Engineering Applications ◽

10.1115/1.4047143 ◽

2020 ◽

Vol 12 (6) ◽

Author(s):

Yantao Li ◽

Yulong Ji ◽

Katsuya Fukuda ◽

Qiusheng Liu

Keyword(s):

Heat Transfer ◽

Experimental Data ◽

Convective Heat ◽

Convection Heat Transfer ◽

Bulk Liquid ◽

Transfer Coefficients ◽

Forced Convective Heat Transfer ◽

Abstract This paper presents an experimental investigation of the forced convective heat transfer of FC-72 in vertical tubes at various velocities, inlet temperatures, and tube sizes. Exponentially escalating heat inputs were supplied to the small tubes with inner diameters of 1, 1.8, and 2.8 mm and effective heated lengths between 30.1 and 50.2 mm. The exponential periods of heat input range from 6.4 to 15.5 s. The experimental data suggest that the convective heat transfer coefficients increase with an increase in flow velocity and µ/µw (refers to the viscosity evaluated at the bulk liquid temperature over the liquid viscosity estimated at the tube inner surface temperature). When tube diameter and the ratio of effective heated length to inner diameter decrease, the convective heat transfer coefficients increase as well. The experimental data were nondimensionalized to explore the effect of Reynolds number (Re) on forced convection heat transfer coefficient. It was found that the Nusselt numbers (Nu) are influenced by the Re for d = 2.8 mm in the same pattern as the conventional correlations. However, the dependences of Nu on Re for d = 1 and 1.8 mm show different trends. It means that the conventional heat transfer correlations are inadequate to predict the forced convective heat transfer in minichannels. The experimental data for tubes with diameters of 1, 1.8, and 2.8 mm were well correlated separately. And, the data agree with the proposed correlations within ±15%.

Convective Heat Transfer Coefficients of Multifaceted Longitudinal and Transversal Bricks of Lattice Setting in Tunnel Kilns

Journal of Thermal Science and Engineering Applications ◽

10.1115/1.4040034 ◽

2018 ◽

Vol 10 (5) ◽

Cited By ~ 1

Author(s):

Hosny Z. Abou-Ziyan ◽

Issa F. Almesri ◽

Mosab A. Alrahmani ◽

Jaber H. Almutairi

Keyword(s):

Heat Transfer ◽

Experimental Data ◽

Sensitivity Analysis ◽

Convective Heat ◽

Specific Energy Consumption ◽

Uniform Flow ◽

Transfer Coefficients ◽

This paper reports the local multifaceted and area-averaged convective heat transfer coefficients (CHTCs) of longitudinal and transverse bricks arranged in lattice brick setting in tunnel kilns, using a three-dimensional (3D) computational fluid dynamics (CFD) model. A mesh sensitivity analysis was performed and the model was validated against reported experimental data in tunnel kilns. Three turbulence models were tested: the standard k–ε, re-normalization group (RNG) k–ε, and k–ω. The k–ω model provided the closest results to the experimental data. The CHTCs from the front, back, left, and right faces of the longitudinal and transverse bricks were calculated under various conditions. Area-averaged CHTCs for bricks were determined from the multifaceted CHTCs. Effects of rows, layers, and walls on faces and area-averaged CHTCs were investigated. A sensitivity analysis was performed to explore the effect of flow channels on the CHTCs. The numerical results showed that the CHTCs are enhanced by 17% for the longitudinal bricks and 27% for the transverse bricks when a uniform flow is reached in the tunnel kilns. Also, similar area-averaged CHTCs for the longitudinal and transverse bricks were obtained as a result of the uniform flow. Therefore, the specific energy consumption, quality, and quantity of brick production could be enhanced.