scholarly journals Influence of fin thickness on heat transfer and flow performance of a parallel flow evaporator

2019 ◽  
Vol 23 (4) ◽  
pp. 2413-2419 ◽  
Author(s):  
Haijun Li ◽  
Enhai Liu ◽  
Guanghui Zhou ◽  
Fengye Yang ◽  
Zhiyong Su ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Comprehensive Evaluation ◽  
Reynolds Numbers ◽  
Parallel Flow ◽  
Heat Transfer Factor ◽  
Heat Transfer Capacity ◽  
Fin Thickness ◽  
The Heat Transfer Coefficient ◽  
Good Agreement

This paper studies numerically the influence of the louver?s fin thickness on heat transfer and flow performance of a parallel flow evaporator, a comprehensive evaluation and analysis of the five structures at different Reynolds numbers are systematically carried out. Comparison of the numerical results with the experimental data shows good agreement with maximal errors of 12.16% and 5.29% for the heat transfer factor and the resistance factor, respectively. The results show that the heat transfer coefficient and the pressure drop increase with the increase of the thickness of the louver fins when the Reynolds number is a constant. The analysis of the comprehensive evaluation factor shows that the A-type fin is the best, and it can effectively strengthen the heat exchange on the air side and improve the heat transfer capacity of the system. The research results can provide reference for the structural optimization of the louver fins.

Some Results on the Heat Transfer Within Resonant Cavities at Subsonic and Supersonic Mach Numbers

1971 ◽  
Vol 93 (4) ◽  
pp. 537-542 ◽  
Author(s):  
R. A. White
Keyword(s):  
Heat Transfer ◽  
Reynolds Numbers ◽  
Cavity Resonance ◽  
Pressure Oscillations ◽  
Resonant Cavities ◽  
Coefficient Distribution ◽  
Cavity Opening ◽  
Mach Numbers ◽  
The Heat Transfer Coefficient ◽  
Good Agreement

An experimental investigation of the heat transfer within two cavities (L/D = 1.25 and 2.0) exhibiting self-induced pressure oscillations (commonly referred to as resonance) is discussed. The tests were conducted with free stream Mach numbers between 0.35 and 1.5 with corresponding unit Reynolds numbers of 33 × 105/ft to 41 × 105/ft. The approaching boundary layer and shear layer over the cavitieswere turbulent at all times. The pattern for the heat transfer coefficient distribution over the cavity walls is in good agreement with that found by other investigators. The effect of the self-induced pressure oscillations, however, is to cause large changes in the level of the heat transfer, with low values occurring at the distinctive peaks of the pressure oscillations. The ratio of the integrated heat transfer within the cavity to the heat transfer from a flat plate with area equal to the area of the cavity opening was found to vary from 1.10 to 0.40, depending on Mach number and cavity resonance conditions.

scholarly journals Inter-cooler in solar-assisted refrigeration system: Theory and experimental verification

2015 ◽  
Vol 19 (4) ◽  
pp. 1379-1382
Author(s):  
Hui-Fan Zheng ◽  
Xiao-Wei Fan ◽  
Guo-Ji Tian ◽  
Lei Liu ◽  
Yin-Long Chen
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
System Theory ◽  
Apex Angle ◽  
Structure Parameters ◽  
Refrigeration System ◽  
Heat Transfer Capacity ◽  
Tooth Apex ◽  
Spiral Angle ◽  
Good Agreement

An inter-cooler in the solar-assisted refrigeration system was investigated experimentally and theoretically, and the theoretical prediction was fairly in good agreement with the experimental data. The influence of pipe diameter, tooth depth, and spiral angle of inter-cooler on the performance of the refrigerant system was analyzed. It was concluded that heat transfer is influenced deeply by the structure parameters of inter-cooler, and the heat transfer capacity increases with tooth depth and spiral angle increasing, and decreases with tooth apex angle increasing.

Experimental Study on Post-Dryout Heat Transfer of Dispersed Flow in Vertical Narrow Annuli

2004 ◽  
Author(s):  
Aye Myint ◽  
Wenxi Tian ◽  
Zhihui Li ◽  
Suizheng Qiu ◽  
Dounan Jia ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Mass Velocity ◽  
Narrow Channel ◽  
Empirical Correlations ◽  
Annular Gap ◽  
Low Mass ◽  
Narrow Annuli ◽  
The Heat Transfer Coefficient ◽  
Good Agreement

Forced convective post dryout heat transfer in narrow channel with 1.2 mm gap has been experimentally investigated with deionized water. The experiment was carried out with pressure ranging from 1.38 to 5.9 MPa and low mass velocity from 52.9 to 84.2 kg/m2 s. The experimental data were compared with well known empirical correlations such as Groeneveld, Polimik, Miropolskiy and Slaughterbeck and it was found that these correlations could not predict very well in narrow annular gap at low mass velocity. Based on the experimental data, the heat transfer coefficient increases with increasing heat flux, mass flux and pressure. A new empirical correlation for narrow annuli at low mass velocity was then developed which has a good agreement with the experimental data.

Diameter Effects on Nucleate Pool Boiling for a Vertical Tube

2000 ◽  
Vol 123 (2) ◽  
pp. 400-404 ◽  
Author(s):  
Myeong-Gie Kang
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Heat Transfer Coefficient ◽  
Boiling Heat Transfer ◽  
Pool Boiling ◽  
Vertical Tube ◽  
Nucleate Pool Boiling ◽  
Vertical Orientation ◽  
The Heat Transfer Coefficient ◽  
Good Agreement

Diameter effects on nucleate pool boiling heat transfer for a tube with vertical orientation have been obtained experimentally. According to the results (1) the heat transfer coefficient decreases as the tube diameter increases and the trend is more notable with a rougher surface, and (2) the experimental data is in good agreement with the Cornwell and Houston’s correlation within a ±20 percent scatter range.

Verification of RANS for Analyzing Convective Cooling System With and Without Ribs

2009 ◽  
Author(s):  
Wei Chen ◽  
Jing Ren ◽  
Hongde Jiang
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Pressure Drop ◽  
Turbulence Model ◽  
Cooling System ◽  
Reynolds Numbers ◽  
Convective Cooling ◽  
Turn Region ◽  
Good Agreement ◽  
Rans Method

Accurate prediction of pressure drop and heat transfer in convective cooling system is of importance to gas turbine industry. In the present paper, a detailed study and assessment of RANS method based on SST reattach turbulence model is performed on a convective cooling system in three kinds of U-duct: smooth, with 45 degree or 90 degree angled parallel ribs. Heat transfer and pressure drop distributions in the ducts are analyzed spatially at the Reynolds numbers of 15000, 30000 and 60000. The numerical results are compared with the experimental data and the empirical correlation from Han et al. It is found that the obtained pressure drop distribution based on RANS with SST reattach turbulence model matches the experimental data for all the U-ducts adequately. Meanwhile, the heat transfer is well predicted by the RANS method in the cases of smooth duct and 45 degree ribbed duct. A good agreement is obtained in the turn region of 45 degree ribbed duct, it owes to the strong secondary flow induced by ribs, which restrain the mainstream to separate and accelerate in the turn. But, the heat transfer is significantly under-predicted for 90 degree ribbed duct since the flow reattachment point between the ribs is predicted farther away from the upstream rib than that in the experiment. Therefore, it is suggested that the RANS method with a suitable turbulence model is valuable for the smooth and 45 degree ribbed U-duct with the acceptable engineering accuracy. But the prediction of heat transfer in 90 degree ribbed U-duct is still a challenge for the RANS to solve.

Heat Transfer in a Surfactant Drag-Reducing Solution—A Comparison With Predictions for Laminar Flow

2005 ◽  
Vol 128 (6) ◽  
pp. 557-563 ◽  
Author(s):  
Paul L. Sears ◽  
Libing Yang
Keyword(s):  
Heat Transfer ◽  
Laminar Flow ◽  
Reynolds Numbers ◽  
High Heat ◽  
High Heat Flux ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Nusselt Numbers ◽  
Drag Reducing Additive ◽  
Good Agreement

Heat transfer coefficients were measured for a solution of surfactant drag-reducing additive in the entrance region of a uniformly heated horizontal cylindrical pipe with Reynolds numbers from 25,000 to 140,000 and temperatures from 30to70°C. In the absence of circumferential buoyancy effects, the measured Nusselt numbers were found to be in good agreement with theoretical results for laminar flow. Buoyancy effects, manifested as substantially higher Nusselt numbers, were seen in experiments carried out at high heat flux.

Predictions of the Effect of Roughness on Heat Transfer From Turbine Airfoils

1998 ◽  
Author(s):  
Anil K. Tolpadi ◽  
Michael E. Crawford
Keyword(s):  
Heat Transfer ◽  
Side Surface ◽  
Suction Side ◽  
Reynolds Numbers ◽  
Surface Finishing ◽  
Transfer Coefficients ◽  
Average Roughness ◽  
Wide Range ◽  
Turbine Airfoils ◽  
Good Agreement

The heat transfer and aerodynamic performance of turbine airfoils are greatly influenced by the gas side surface finish. In order to operate at higher efficiencies and to have reduced cooling requirements, airfoil designs require better surface finishing processes to create smoother surfaces. In this paper, three different cast airfoils were analyzed: the first airfoil was grit blasted and codep coated, the second airfoil was tumbled and aluminide coated, and the third airfoil was polished further. Each of these airfoils had different levels of roughness. The TEXSTAN boundary layer code was used to make predictions of the heat transfer along both the pressure and suction sides of all three airfoils. These predictions have been compared to corresponding heat transfer data reported earlier by Abuaf et al. (1997). The data were obtained over a wide range of Reynolds numbers simulating typical aircraft engine conditions. A three-parameter full-cone based roughness model was implemented in TEXSTAN and used for the predictions. The three parameters were the centerline average roughness, the cone height and the cone-to-cone pitch. The heat transfer coefficient predictions indicated good agreement with the data over most Reynolds numbers and for all airfoils-both pressure and suction sides. The transition location on the pressure side was well predicted for all airfoils; on the suction side, transition was well predicted at the higher Reynolds numbers but was computed to be somewhat early at the lower Reynolds numbers. Also, at lower Reynolds numbers, the heat transfer coefficients were not in very good agreement with the data on the suction side.

Jet-to-Plate Distance Effect on Heat Transfer From a Flat Plate to an Impinging Jet at Various Reynolds Numbers

2012 ◽  
Author(s):  
Patricia Streufert ◽  
Terry X. Yan ◽  
Mahdi G. Baygloo
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Reynolds Number ◽  
Flat Plate ◽  
Numerical Solutions ◽  
Stokes Equations ◽  
Local Heat Transfer ◽  
Reynolds Numbers ◽  
Air Jet ◽  
Plate Distance

Local turbulent convective heat transfer from a flat plate to a circular impinging air jet is numerically investigated. The jet-to-plate distance (L/D) effect on local heat transfer is the main focus of this study. The eddy viscosity V2F turbulence model is used with a nonuniform structured mesh. Reynolds-Averaged Navier-Stokes equations (RANS) and the energy equation are solved for axisymmetric, three-dimensional flow. The numerical solutions obtained are compared with published experimental data. Four jet-to-plate distances, (L/D = 2, 4, 6 and 10) and seven Reynolds numbers (Re = 7,000, 15,000, 23,000, 50,000, 70,000, 100,000 and 120,000) were parametrically studied. Local and average heat transfer results are analyzed and correlated with Reynolds number and the jet-to-plate distance. Results show that the numerical solutions matched experimental data best at low jet-to-plate distances and lower Reynolds numbers, decreasing in ability to accurately predict the heat transfer as jet-to-plate distance and Reynolds number was increased.

Forced Convection in a Porous Channel With Discrete Heat Sources

2000 ◽  
Vol 123 (2) ◽  
pp. 404-407 ◽  
Author(s):  
C. Cui ◽  
X. Y. Huang ◽  
C. Y. Liu
Keyword(s):  
Heat Transfer ◽  
Reynolds Numbers ◽  
Heat Fluxes ◽  
Experimental Results ◽  
Porous Channel ◽  
Heat Sources ◽  
Nusselt Numbers ◽  
Discrete Heat Sources ◽  
Flow Through ◽  
Good Agreement

An experimental study was conducted on the heat transfer characteristics of flow through a porous channel with discrete heat sources on the upper wall. The temperatures along the heated channel wall were measured with different heat fluxes and the local Nusselt numbers were calculated at the different Reynolds numbers. The temperature distribution of the fluid inside the channel was also measured at several points. The experimental results were compared with that predicted by an analytical model using the Green’s integral over the discrete sources, and a good agreement between the two was obtained. The experimental results confirmed that the heat transfer would be more significant at leading edges of the strip heaters and at higher Reynolds numbers.

Heat Transfer Evaluation for a Two-Pass Smooth Wall Channel: Stationary and Rotating Cases

2019 ◽  
Vol 142 (6) ◽  
Author(s):  
Mandana S. Saravani ◽  
Nicholas J. DiPasquale ◽  
Ahmad I. Abbas ◽  
Ryoichi S. Amano
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Rotational Speed ◽  
Numerical Study ◽  
Flow Behavior ◽  
Smooth Wall ◽  
Eddy Simulation ◽  
Large Eddy ◽  
The Heat Transfer Coefficient ◽  
Good Agreement

Abstract This study presents findings on combined effects of Reynolds number and rotational effect for a two-pass channel with a 180-deg turn, numerically and experimentally. To have a better understanding of the flow behavior and to create a baseline for future studies, a smooth wall channel with the square cross section is used in this study. The Reynolds number varies between 6000 and 35,000. Furthermore, by changing the rotational speed, the maximum rotation number of 1.5 is achieved. For the numerical investigation, large eddy simulation (LES) is utilized. Results from the numerical study show a good agreement with the experimental data. From the results, it can be concluded that increasing both Reynolds number and rotational speed is in favor of the heat transfer coefficient enhancement, especially in the turn region.

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