Comparison of Mist Effect on the Heat Transfer Coefficient and Skin Friction Factor in an Impinging Jet

2008 ◽  
Author(s):  
Mohammad Mahdi Heyhat ◽  
Mohammad Moghiman ◽  
Shoatb Mahjoub
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Friction Factor ◽  
Skin Friction ◽  
Impinging Jet ◽  
The Heat Transfer Coefficient

scholarly journals Cooling of High Heat Flux Flat Surface with Nanofluid Assisted Convective Loop: Experimental Assessment

2017 ◽  
Vol 64 (4) ◽  
pp. 519-531 ◽  
Author(s):  
Amir Arya ◽  
Saeed Shahmiry ◽  
Vahid Nikkhah ◽  
Mohamad Mohsen Sarafraz
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Friction Factor ◽  
High Heat ◽  
High Heat Flux ◽  
Overall Heat Transfer Coefficient ◽  
Cooling Loop ◽  
The Heat Transfer Coefficient

Abstract Experimental investigation was conducted on the thermal performance and pressure drop of a convective cooling loop working with ZnO aqueous nanofluids. The loop was used to cool a flat heater connected to an AC autotransformer. Influence of different operating parameters, such as fluid flow rate and mass concentration of nanofluid on surface temperature of heater, pressure drop, friction factor and overall heat transfer coefficient was investigated and briefly discussed. Results of this study showed that, despite a penalty for pressure drop, ZnO/water nanofluid was a promising coolant for cooling the micro-electronic devices and chipsets. It was also found that there is an optimum for concentration of nanofluid so that the heat transfer coefficient is maximum, which was wt. % = 0.3 for ZnO/water used in this research. In addition, presence of nanoparticles enhanced the friction factor and pressure drop as well; however, it is not very significant in comparison with those of registered for the base fluid.

Prediction of Heat Transfer and Friction for the Louver Fin Geometry

1992 ◽  
Vol 114 (4) ◽  
pp. 893-900 ◽  
Author(s):  
A. Sahnoun ◽  
R. L. Webb
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Friction Factor ◽  
Reynolds Numbers ◽  
Maximum Error ◽  
Transfer Coefficients ◽  
Mean Error ◽  
The Heat Transfer Coefficient

This paper is concerned with prediction of the air-side heat transfer coefficient of the louver fin geometry used in automotive radiators. An analytical model was developed to predict the heat transfer coefficient and friction factor of the louver fin geometry. The model is based on boundary layer and channel flow equations, and accounts for the “flow efficiency” in the array, as previously reported by Webb and Trauger. The model has no empirical constants. The model allows independent specifications of all of the geometric parameters of the louver fin. This includes the number of louvers over the flow depth, the louver width and length, and the louver angle. The model was validated by predicting the heat transfer coefficient and friction factor of 32 louver arrays tested by Davenport, which spanned hydraulic diameter based Reynolds numbers of 300–2800. At the highest Reynolds number, all of the heat transfer coefficients were predicted within a maximum error of −14 / + 25 percent, and a mean error of ± 8 percent. The high Reynolds number friction factors were predicted with a maximum error −22 /+ 26 percent, with a mean error of ± 8 percent. The error ratios were slightly higher at the lowest Reynolds numbers.

Convective heat transfer and fluid flow characteristics in fin and oval-tube heat exchanger

2021 ◽  
Vol 15 (2) ◽  
pp. 7936-7947
Author(s):  
Yamina Abdoune ◽  
Sahel Djamel ◽  
Benzeguir Redouane ◽  
Alem Karima
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Heat Transfer Coefficient ◽  
Heat Exchanger ◽  
Transfer Coefficient ◽  
Friction Factor ◽  
Tube Heat Exchanger ◽  
Baseline Case ◽  
Oval Tube ◽  
The Heat Transfer Coefficient

The forced convective heat transfer behavior of a turbulent air flow, steady and Newtonian over a fin and oval-tube heat exchanger has been examined numerically. Where, the effect of the tube tilt angle (α) on the heat transfer coefficient and the friction factor was tested. The inclination angle of the oval-tubes going from 0° (Baseline case) to 90° with a step of 10°. The fluid flows and heat transfer characteristics are presented for Reynolds numbers ranging from 3.000 to 12.000. All investigations are carried out with the help of the CFD ANSYS Fluent. Heat transfer coefficient results in the term of the Nusselt number are validated with the available experimental data and a maximum deviation of 9 % is observed. Reasonable agreement is found. The obtained results show that the tube's inclination angle of 20° is the best design which significantly removes the hot spots behind the tubes, thus giving an increase in the heat transfer coefficient of 13 % compared to the baseline case. In addition, useful correlations are developed to predict Nusselt number and friction factor in the fin and oval-tube heat exchanger.

Numerical Simulation of Impinging Jet with Mist Injection

2012 ◽  
Vol 249-250 ◽  
pp. 452-459
Author(s):  
Xiao Ming Tan ◽  
Ye Fang Li ◽  
Jing Zhou Zhang
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Mass Flow ◽  
Impinging Jet ◽  
Cooling Effectiveness ◽  
Cooling Performance ◽  
Air Mass ◽  
The Heat Transfer Coefficient

Two-phase CFD calculations using commercial code Fluent were employed to calculate the air and droplet flows with and without mist in an impinging jet. The effects of phase changing of the water droplets, the mist injection rate, the heat flux of target and the geometrical parameters of the slot were studied to reveal the cooling effectiveness. The results show that the key enhancement mechanism of mist/air impinging jet is the effect of evaporation of the droplets. The wall temperature significantly decreased because of mist injection and the injection of 5% mist has a strengthen of cooling effectiveness with 89% enhancement. This enhancement would be reduced by higher heat flux of target wall. Concentration plays a major role in the cooling performance. Increasing the mist ratio makes the cooling strengthen significantly. A mist of 5% can provide a cooling enhancement of 32% at stagnation than the mist of 1%. The effect of the mist ratio on cooling declines gradually from the impingement area to the downstream area. A fit width and height ratio had a major impact on the cooling performance of mist/air impinging jet. For constant mist/air mass flow and inlet width b, when H/b increases, the heat transfer coefficient increases first and then decreases; for constant mist/air mass flow and impinging distance H, the heat transfer coefficient increases as H/b increases.

The Effect of Surface Roughness on the Convection Heat-Transfer Coefficient for Fully Developed Turbulent Flow in Ducts With Uniform Heat Flux

1959 ◽  
Vol 81 (2) ◽  
pp. 168-173 ◽  
Author(s):  
R. T. Lancet
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Friction Factor ◽  
Convection Heat Transfer ◽  
Uniform Heat Flux ◽  
Friction Factors ◽  
Fully Developed Turbulent Flow ◽  
The Heat Transfer Coefficient ◽  
Effect Of Surface

Experimental data are presented for the heat-transfer coefficient and friction factor in a smooth and a rough duct with a hydraulic diameter of approximately 0.035 in. The flow was fully developed and turbulent, and the heat addition was uniform over the length of the tube. The rough tube indicated appreciable increases in heat-transfer coefficient and friction factor. The smooth-tube friction factors corresponded to rough-tube values, indicating the difficulty involved in obtaining smooth surfaces for very small ducts.

Heat Transfer and Pressure Drop Correlations for Double-Pass Solar Collector With and Without Porous Media

2002 ◽  
Author(s):  
K. Sopian ◽  
Adam M. Elradi ◽  
Shahrir Abdullah ◽  
K. V. Wong
Keyword(s):  
Heat Transfer ◽  
Porous Media ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Friction Factor ◽  
Operating Conditions ◽  
Transient Heat Transfer ◽  
Double Pass ◽  
The Heat Transfer Coefficient

Correlations of transient heat transfer and pressure drop have been developed for air flowing through the porous media, which packed a double-pass solar air heater. Various porous media are arranged in different porosities to increase heat transfer, area density and the total heat transfer rate. Transient heat transfer experiments indicate that both the heat transfer coefficient and the friction factor are strong functions of porosity. The heat transfer coefficient and the friction factor are also strong functions of the geometrical parameters of the porous media. A test collector was developed and tested indoors by varying the design features and operating conditions using a halogen-lamp simulator as a radiation source. This type of collector can be used for drying and heat applications such as solar industrial processes, space heating and solar drying of agricultural products.

Buoyancy and Property Variation Effects in Turbulent Mixed Convection of Water in Vertical Tubes

1996 ◽  
Vol 118 (2) ◽  
pp. 381-387 ◽  
Author(s):  
Y. Parlatan ◽  
N. E. Todreas ◽  
M. J. Driscoll
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Mixed Convection ◽  
Transfer Coefficient ◽  
Friction Factor ◽  
Temperature Dependent Viscosity ◽  
Experimental Conditions ◽  
Property Variation ◽  
Dependent Viscosity ◽  
The Heat Transfer Coefficient

Friction factor and heat transfer coefficient behavior are investigated experimentally under mixed convection conditions in aiding and opposing transition and turbulent flow of water (4000 < Re < 9000 and Bo < 1.3). With increasing buoyancy influence, the friction factor increases by as much as 25 percent in aiding flow, while it decreases by as much as 25 percent in opposing flow (GrΔT < 7·106). The effects of temperature-dependent viscosity variations are also included in the analysis (0.5 < μw/μb < 1.0). When they are taken into account, the increase in the friction factor due to buoyancy forces alone in upward flow becomes larger. The friction factor behavior is compared with previous studies in the literature. Our experimental data agree well with some of the previous experiments described in the literature. The heat transfer coefficient was also measured under the same experimental conditions; the heat transfer coefficient monotonically increases in opposing flow by as much as 40 percent, and first decreases by 50 percent and then recovers in aiding flow with increasing buoyancy influence.

scholarly journals Effect of Low Volume Concentration on Heat Transfer Enhancement of EG-Water Based Fe3O4 Nanofluid

2020 ◽  
Vol 9 (4) ◽  
pp. 1796-1802
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Heat Transfer Enhancement ◽  
Friction Factor ◽  
Base Fluid ◽  
Volume Concentration ◽  
Transfer Enhancement ◽  
Water Based ◽  
The Heat Transfer Coefficient

Customization of thermophysical properties of the working fluids has tremendous potential in heat transfer enhancement. In the present paper, experimentation is conducted to determine the heat transfer coefficient and friction factor of 20:80 Ethylene Glycol-Water(20:80 EG-Water) based Fe3O4 nanofluid in a Double Pipe Heat Exchanger with U Bend (DPHE). Experiments are performed in the turbulent flow regime at an operating temperature of 47.5°C. Fe3O4 nanoparticles of size less than 50 nm are mixed with 20:80 EG-Water solution in the volume concentration range of 0.02% to 0.08%. Results indicate that as the concentration of nanoparticles increase, the heat transfer coefficient of the nanofluid increases up to 0.04% concentration and then decreases, while the friction factor is observed to increase with the increase of volume concentration. Within the Reynolds number range considered in the analysis, the average enhancement in the heat transfer coefficient is 24.1% at 0.04% concentration compared to that of the base fluid. The average enhancement in the friction factor is observed to be 25.58% at 0.08% concentration of Fe3O4 / 20:80 EG-Water nanofluid compared to that of base fluid.

Undershoots in the Heat Transfer Coefficient and Friction-Factor Distributions in the Entrance Region of Turbulent Pipe Flows

2018 ◽  
Vol 140 (6) ◽  
Author(s):  
Eph M. Sparrow ◽  
John M. Gorman ◽  
Daniel B. Bryant
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Friction Factor ◽  
Local Minimum ◽  
Turbulent Pipe Flow ◽  
Transfer Coefficients ◽  
Fanning Friction Factor ◽  
The Heat Transfer Coefficient ◽  
Pipe Inlet

Heat transfer coefficients for turbulent pipe flow are typically envisioned as axially varying from very high values at the pipe inlet to a subsequent monotonic decrease to a constant fully developed value. This distribution, although well enshrined in the literature, may not be universally true. Here, by the use of high accuracy numerical simulation, it was shown that the initially decreasing values of the coefficient may attain a local minimum before subsequently increasing to a fully developed value. This local minimum may be characterized as an undershoot. It was found that whenever a turbulent flow laminarizes when it enters a round pipe, the undershoot phenomenon occurs. The occurrence of laminarization depends on the geometry of the pipe inlet, on fluid-flow conditions in the upstream space from which fluid is drawn into the pipe inlet, on the magnitude of the turbulence intensity, and on the Reynolds number. However, the presence of the undershoot does not affect the fully developed values of the heat transfer coefficient. It was also found that the Fanning friction factor may also experience an undershoot in its axial variation. The magnitude of the heat transfer undershoot is generally greater than that of the Fanning friction factor undershoot.

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